Stem cell-derived pancreatic beta cells: a step closer to functional diabetes treatment?

Abstract

Abstract

Diabetes remains one of the significant health struggles worldwide, leading to disability and mortality. There are several types, with Types 1 and 2 representing the majority of cases. Pancreatic beta cells play a key role in glucose control through the secretion of insulin. Insulin, a key player, is under-secreted in diabetes due to autoimmune destruction of the beta cells in type 1 diabetes and exhaustion of beta cell secretion in type 2. Hence, insulin plays a central role in the management of both conditions. Lifestyle modifications and pharmacological agents are significant components of managing diabetes, although they come with limitations; hence, the exploration of stem cells in diabetes management. A thorough literature search was conducted across several databases, identifying randomized and non-randomized controlled trials that utilized stem cells in patients with diabetes. The intervention details, primary and secondary outcomes, key findings, and safety profiles were documented and discussed. We explored key protocols and methods for generating pancreatic beta-like cells from stem cells, as well as the role of specific molecules and pathways in stem cell differentiation. In this paper, we also discuss preclinical animal studies, explore the challenges of immunogenicity, and address ethical concerns that limit the implementation of stem cells in clinical practice. A comparative analysis was conducted to evaluate conventional insulin therapy, islet transplantation, and stem cell-based approaches. Although stem cells represent a potentially valuable direction, their application clinically remains mainly experimental, and future studies should incorporate larger cohorts, diverse populations with varying comorbidities, and extended follow-up periods to better ascertain their long-term efficacy and safety.

Clinical trial number

Not applicable

Introduction

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both [1]. Diabetes has remained a disease of public health importance, affecting over 800 million individuals globally, with its prevalence rising exponentially in low-middle-income countries [2]. It affects almost all the systems in the body, resulting in microvascular complications such as retinopathy, neuropathy, and nephropathy, and macrovascular complications such as cardiovascular complications and peripheral arterial disease, which results in lower limb ulceration and amputation [3, 4]. Data from 2021 revealed that almost 2 million deaths were directly a result of diabetes, with kidney diseases related to diabetes causing more than 500,000 extra deaths [2]. Additionally, 11% of cardiovascular deaths were reported to be due to hyperglycemia [2]. There are several classifications of diabetes mellitus, but the two major ones are type 1 and type 2. Type 1 DM occurs due to autoimmune destruction of the pancreatic beta cells, which results in deficient insulin production. It is also treated with daily insulin administration. Type 2 diabetes mellitus (T2DM) is more prevalent and often remains undiagnosed for long periods due to its asymptomatic progression. It occurs due to the combination of defects in insulin secretion by pancreatic beta cells and insulin resistance [5].

While classic symptoms like polyuria, polydipsia, polyphagia and weight loss are observed in type 1 diabetes mellitus (T1DM), many type 2 diabetics may remain asymptomatic [6]. Management of Type 2 DM includes lifestyle modifications such as diet, exercise, and medications [7, 8].

DM medications could be insulin, oral medications, or other injected medications. Insulin replacement therapy is used to treat type 1 DM, in which the pancreas does not secrete insulin [2]. Insulin can also be used to manage type 2 DM when blood glucose levels cannot be controlled by diet, weight loss, and oral medications. Oral hypoglycemic agents are used to treat type 2 DM in addition to lifestyle modifications. These oral hypoglycemic agents are divided into various classes, which include sulphonylureas, biguanides, DPP-4 inhibitors, alpha-glucosidase inhibitors, GLP-1 receptor agonists, meglitinide analogues, thiazolidinediones, and SGLT-2 inhibitors [2, 8]. Metformin, a biguanide which enhances insulin sensitivity, is used as the first-line drug [9]. Other classes can be used as second-line or third-line drugs [9]. Despite the availability of these drugs that significantly improve the quality of life for type 2 DM patients, treatment limitations persist. Over time, as the disease progresses, these medications offer little to no help [10].

Additionally, certain drugs are associated with side effects that can limit their long-term use or suitability for specific patients, resulting in challenges in achieving optimal disease management [11]. While insulin is helpful in the control of blood glucose in type 1 DM, it is not a cure [2]. Other limitations to achieving long-term glycemic control in type 1 and type 2 DM patients include an elevated risk of hypoglycemia, unintended weight gain, unpredictable fluctuations in glucose levels throughout the day and risk of long-term complications due to the underlying metabolic issues [12–15].

To overcome these limitations, advanced and emerging treatment approaches are being explored, including stem-cell-derived beta-like cell therapies, while established strategies like pancreas and islet transplantation continue to evolve [15, 16]. Stem cell therapy offers an innovative yet investigational approach to managing diabetes mellitus, with early-stage studies showing encouraging preclinical results. Human pluripotent stem cells (hPSCs) could either be embryonic stem cells, mesenchymal stem cells, or new induced pluripotent stem cells that are generated by reprogramming mature adult cells. These stem cells have the ability to replicate and differentiate into any adult cell type [17]. Under the right conditions, these stem cells can differentiate into insulin-producing beta-like cells, replacing damaged cells [18]. We use the term “beta-like cells” to reflect that although these cells share many functional properties with native pancreatic beta cells, they are not yet identical in terms of stability, full maturity, and physiological regulation. Although significant progress has been made in this area of research, the clinical application of this modality for DM treatment currently faces several challenges and limitations, including immunogenicity and the risk of teratoma formation [18, 19]. This study aims to investigate the role of stem cells in the generation of pancreatic beta-like cells, as well as current preclinical and clinical studies on this subject. It also examines the challenges and considerations in stem cell therapy for diabetes mellitus (DM), compares it with other therapies, and outlines future directions.

Methodology

Literature search strategy

The appropriate studies on stem-cell-derived pancreatic beta-like cells for diabetes treatment were identified through a thorough literature search. The search was made through PubMed, Scopus, Embase, Web of Science, and Google Scholar databases. Key search terms used were “pancreatic stem cell transplant,” “beta cell regeneration,” “stem-cell therapy,” “Type 1 Diabetes,” “Type 2 Diabetes,” and “Clinical trials.” Our search was limited to peer-reviewed studies published in English and dated between 2018 and 2025. A summary of the included studies is presented in Table 1.

Table 1.

Overview of included studies

Author & Year	Study design	Rationale	Sample size	Patient population	Intervention Details	Primary & Secondary outcomes	Follow-up duration	Key findings	Safety profile
Dantas et al., 2020 [60]	Prospective, dual-center, open trial	To preserve β-cell function and prolong the honeymoon phase in recent‐onset T1D patients using adipose tissue‐derived stromal/stem cells (ASC) and vitamin D.	7 ASC (Adipose tissue-derived stromal/stem cells) + VIT D) and 2 controls	Recent-onset Type 1 Diabetes (T1D) patients aged 16–35 years; <4 months since diagnosis; positive GADA (glutamic acid decarboxylase antibody) test	One dose of allogenic ASC (1 × 10^6 cells/kg) infused + daily oral cholecalciferol (2,000 UI/day) for six months	Primary: Changes in basal and peak C-peptide levels. Secondary: HbA1c levels, insulin requirements, frequency of honeymoon phase.	6 months	- ASC + Vitamin D showed improved basal C-peptide levels (p = 0.018). - HbA1c decreased (p = 0.01). − 100% of Group 1 were in the honeymoon phase at T6 compared to 75% (Group 2) and 50% (Group 3). - Insulin doses remained stable.	Transient headache, local infusion reactions, tachycardia (n = 4), thrombophlebitis (n = 4), abdominal cramps (n = 1), transient scotomas (n = 2), and one case of central retinal vein occlusion (n = 1); resolved by the 6th month.
Wang et al., 2024 [63]	Phase 1 clinical trial, single patient	To restore insulin production and achieve glycemic control in longstanding T1D through autologous chemically induced pluripotent stem cell-derived islets (CiPSC‐islets) transplantation	1	25-year-old female with Type 1 Diabetes (T1D) for 11 years, BMI 27.3 kg/m², with prior liver and pancreas transplants.	Transplantation of autologous chemically induced pluripotent stem-cell-derived islets (CiPSC-islets) beneath the abdominal anterior rectus sheath.	Primary: Decrease in HbA1c to < 7% or by ≥ 1%, no occurrence of severe hypoglycemic events, safety and tolerability assessment Secondary: Insulin independence, stimulated C-peptide level ≥ 0.3 ng/mL.	1 year	- Achieved insulin independence on Day 75 post-transplantation. - Sustained glycemic control with HbA1c ≤ 5.7%. - Improved glucose tolerance, C-peptide response, and glycemic variability (TIR > 98%).	No teratoma formation or graft overgrowth. Minor adverse events included pain at the puncture site and nausea. No treatment-emergent severe adverse events observed during follow-up.
Ramzy et al., 2021 [65]	Open-label, phase 1/2 clinical trial	To replace lost insulin-producing cells and reduce insulin requirements by providing an exogenous source of insulin-producing cells in patients lacking endogenous beta cell function, using implanted pancreatic endoderm cells (PEC-01).	15	Adults with Type 1 Diabetes (10–54 years since diagnosis)	PEC-01 pancreatic endoderm cells implanted in macroencapsulation devices, combined with immunosuppressive therapy (ATG and MMF).	Primary: Change in C-peptide levels from baseline to Week 26 MMTT. Secondary: Implant tolerability, adverse events, immune sensitization, premature explants, change in insulin requirements, > 50% reduction in insulin requirements, insulin independence, and time in target glucose range.	1 year	Meal-responsive C-peptide secretion increased significantly by Week 26 (p = 0.0026). Insulin requirements reduced by 20% (p < 0.001), and time in target glucose range improved by 13% (p < 0.001). No patients achieved insulin independence, and only one patient had a > 50% reduction in insulin requirements. Implants were well-tolerated with no teratoma formation.	No teratoma formation observed. Two patients experienced serious immunosuppression-related adverse events (typhlitis, liver abscess, aplastic anemia).
Keymeulen et al., 2024 [62]	Phase 1/2, open-label, multicenter clinical trial	To replace beta cells in beta-cell-deficient individuals through the implantation of device-encapsulated pancreatic endoderm cells (PEC 01).	10	Men and non-pregnant women with Type 1 Diabetes (T1D) for ≥ 5 years, hypoglycemia unawareness (Clarke score ≥ 4) or significant glycemic lability, stable diabetes regimen, willing to use continuous glucose monitoring, and eligible for surgical implantation.	Implantation of device-encapsulated PEC-01 (pancreatic endoderm cells) cells with optimized perforation patterns, under immunosuppression (anti-thymocyte globulin, tacrolimus, mycophenolate mofetil).	Primary: Change in C-peptide levels from baseline to Week 26 mixed meal tolerance test (MMTT) Secondary: Percent of patients achieving C-peptide > 0.07 nmol/L, reduction in insulin dose, time in glycemic ranges (hypoglycemia, euglycemia, hyperglycemia), frequency of hypoglycemic events (HE).	2 years	Plasma C-peptide levels increased (> 0.07 nmol/L) in 4 of 10 patients by Week 26. Insulin dose reductions were observed but no patients achieved insulin independence. Time in euglycemic range (70–180 mg/dL) improved, with one patient reaching 85% Time in Range (TIR) at Month 12.	The most common adverse event was procedural pain. Two serious events occurred: one related to surgery, and one to immunosuppression. No teratoma formation or adverse events leading to withdrawal were reported.
Izadi et al., 2022 [64]	Phase I/II, triple-blinded, placebo-controlled clinical trial	To modulate immune responses and preserve β-cell function in newly diagnosed T1D patients using autologous mesenchymal stem cells (MSCs).	21	Newly diagnosed T1D patients (8–40 years), fasting C-peptide ≥ 0.3 nmol/L, presence of at least one β-cell autoantibody.	Autologous bone marrow-derived MSCs (1 × 10^6 cells/kg) injected intravenously at weeks 0 and 3; placebo group received normal saline.	Primary: Safety (treatment-related adverse events and hypoglycemia) Secondary: Changes in HbA1c, C-peptide, pro-/anti-inflammatory cytokines, regulatory T-cell percentages, and Quality of Life (QoL).	12 months	MSC transplantation significantly reduced HbA1c levels by month 12 (p = 0.043). C-peptide levels improved, though changes were not significant. Anti-inflammatory cytokines IL-4 and IL-10 increased significantly (p < 0.05), while TNF-α decreased by month 6 (p = 0.027). Early transplantation resulted in better metabolic and immune responses compared to late transplantation.	No major complications or deaths reported. Mild adverse events included a transient injection site reaction and mild lymphocytosis.
Lian et al., 2023 [66]	Phase 2, open-label, randomized clinical trial	To improve immune regulation and metabolic control in T2DM patients using intravenous human umbilical cord-derived mesenchymal stem cells (hUC-MSCs).	34	Adults with T2DM, HbA1c 7.5-9%, fasting blood glucose (FBG) < 10 mmol/L.	Intravenous infusion of human Umbilical Cord-MSCs (hUC-MSC) at a dose of 1 × 10^6 cells/kg weekly for 3 weeks. Placebo group received acellular saline.	Primary: Safety (adverse events). Secondary: Changes in HbA1c, FBG, lymphocyte levels, coagulation markers, and immune parameters.	24 weeks	hUC-MSC infusion improved immune response markers (increased immunoglobulin levels, decreased lymphocyte counts, and higher neutrophil-to-lymphocyte ratio). No significant changes in HbA1c, FBG, or liver/renal functions were observed. Coagulation markers (D-dimer and fibrinogen) were elevated but normalized post-treatment.	No serious adverse events reported. Mild events included transient fever (16.7%) and fatigue (16.7%). Hypoglycemia occurred in one patient, resolved spontaneously. No evidence of tumor formation or organ dysfunction was observed.
Lian et al., 2022 [67]	Open-label clinical study	To enhance β-cell function and reduce insulin resistance in T2DM patients through repeated infusions of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs).	16	Adults (18–70 years) with T2DM, HbA1c 7-9.5%, stable glucose-lowering treatment for at least 2 months.	Intravenous infusion of human umbilical cord mesenchymal stem cells (hUC-MSCs) at 1 × 10^6 cells/kg per week for 3 weeks.	Primary: Safety (adverse events). Secondary: Changes in fasting blood glucose (FBG), HbA1c, islet β-cell function (HOMA-β), insulin resistance (HOMA-IR), and hypoglycemic agent dosage.	12 weeks	Fasting blood glucose significantly reduced by Day 14 [baseline: 9.34 (8.36, 11.77) mmol/L; Day 14: 6.52 (5.22, 8.69) mmol/L; p < 0.01]. HbA1c significantly reduced by Day 84 [baseline: 7.8 (7.53, 8.68)%; Day 84: 7.15 (6.6, 7.93)%; p < 0.01]. HOMA-β improved significantly by Day 28 [baseline: 29.90 (16.43, 37.40); Day 28: 40.97 (19.27, 56.36); p < 0.01]. Hypoglycemic agents reduced in all patients, with 50% achieving > 50% reduction and one patient discontinuing agents.	Four patients experienced transient fever post-infusion. One case of asymptomatic nocturnal hypoglycemia resolved with insulin dose adjustment. No serious adverse events or organ dysfunction reported.
Carlsson et al., 2018 [68]	Phase 1, open-label clinical trial	To assess the viability and safety of a bioartificial pancreas device (βAir) for sustaining islet graft function in T1D.	4	Adults (> 18 years) with T1D for > 5 years, intensive diabetes self-management (≥ 3 daily blood glucose checks and insulin injections/pump therapy).	Subcutaneous implantation of the βAir device containing 155,000-180,000 human islet equivalents, with daily oxygen refilling to support cell viability.	Primary: Safety of the βAir device. Secondary: Efficacy in glycemic control (HbA1c, C-peptide levels), insulin requirements, and patient satisfaction (DTSQ).	3–6 months	C-peptide was detectable in all patients 1 day post-transplantation (range: 0.028–0.093 nmol/L) but declined within 2–4 weeks in most patients. HbA1c improved in 3 patients, though not significantly (p = 0.21). Insulin requirements remained unchanged. Ex vivo tests showed low insulin secretion from retrieved devices. Amyloid deposits were observed in islets post-explanation.	Mild inflammation at the surgical site resolved within 10 days. No donor-specific HLA sensitization or systemic immune responses observed. One patient required a second surgery to fix rotated oxygen ports. No severe adverse events reported.
Carlsson et al., 2015 [69]	Open-label, randomized clinical study	To preserve β-cell function and slow disease progression in newly diagnosed T1D through infusion of autologous mesenchymal stromal cells (MSCs).	20 (10 in MSC group, 10 in control)	Adults (18–40 years) with newly diagnosed Type 1 Diabetes (T1D), stimulated C-peptide > 0.1 nmol/L.	Autologous bone marrow-derived mesenchymal stromal cells (MSCs), cultured under GMP conditions, infused intravenously (2.1–3.6 × 10^6 cells/kg) in a single session.	Primary: Safety of MSC infusion. Secondary: Changes in C-peptide response, HbA1c, insulin doses, and β-cell autoantibodies (GAD65, IA2).	1 year	MSC-treated patients showed preserved or increased C-peptide responses to MMTT, while control patients experienced significant decreases (p < 0.05). No significant changes in HbA1c or insulin doses between groups. GAD65 and IA2 antibodies showed no significant differences.	No serious adverse events were reported. No tumors, infections, or systemic immune responses occurred. Mild upper respiratory tract infections occurred in both groups.
Cai et al., 2016 [70]	Open-label, randomized controlled trial	To restore β-cell activity and improve metabolic control in longstanding T1D using combined umbilical cord mesenchymal stem cells (UC-MSCs) and autologous bone marrow mononuclear cells (aBM-MNCs).	42 (21 SCT, 21 control)	Adults (18–40 years) with Type 1 Diabetes (T1D) for 2–16 years, HbA1c ≥ 7.5% and ≤ 10.5%, fasting C-peptide < 0.1 pmol/mL, daily insulin requirement < 100 IU.	Combined infusion of umbilical cord mesenchymal stromal cells (UC-MSCs) and autologous bone marrow mononuclear cells (aBM-MNCs) through pancreatic artery cannulation	Primary: Change in C-peptide area under the curve (AUC) during Oral Glucose Tolerance Test. Secondary: HbA1c, insulin use, fasting glucose, fasting C-peptide, adverse events, quality of life.	1 year	C-peptide AUC increased 105.7% in the SCT group compared to a 7.7% decrease in controls (p = 0.00012). HbA1c reduced by 12.6% in the SCT group vs. a 1.2% increase in controls (p < 0.01). Insulin use decreased by 29.2% in the SCT group, unchanged in controls (p < 0.01).	Transient abdominal pain (4.7%) and mild bleeding at the puncture site resolved without sequelae. No severe adverse events, malignancies, or systemic immune responses observed.
Gu et al., 2018 [71]	Phase 2, non-randomized, parallel-assignment trial	To induce immune reset and achieve insulin independence in recent-onset T1D using autologous hematopoietic stem cell transplantation (AHSCT).	40 (20 AHSCT, 20 Insulin injections)	Patients with Type 1 Diabetes diagnosed within 6 months using clinical and metabolic parameters, with positive anti-glutamic acid decarboxylase antibody (anti-GAD).	Autologous hematopoietic stem cell transplantation (AHSCT). This involves a high-dose immunosuppressive therapy cyclophosphamide and antithymocyte globulin followed by infusion of patient-derived hematopoietic stem-cells.	Primary: Exogenous insulin dosage. Secondary: C-peptide (fasting, Cmax, AUCC), HbA1c, and anti-GAD antibodies.	48 months	- Insulin Independence: 70% in AHSCT group initially, but 78.6% relapsed by 48 months (p < 0.01). - C-peptide: Higher throughout in the AHSCT group but declined significantly by 48 months (p < 0.001). - HbA1c: Improved early in AHSCT group, no significant difference at 48 months (p < 0.01). - Insulin Dosage: Lower in AHSCT group throughout, including at 48 months (p < 0.01).	Febrile neutropenia (45%), nausea/vomiting (55%), and alopecia (95%) were common but resolved within 2–4 weeks. No severe infections, drug toxicities, or deaths occurred.
Zhao et al., 2017 [72]	Phase I/II, open-label, multi-center clinical trial	To enhance β-cell function and immune modulation in T1D and T2D patients through Stem Cell Educator (SCE) therapy.	36 (9 T1D, 21 T2D)	Patients with T1D or T2D, diagnosed by American Diabetes Association standards, with at least one islet autoantibody for T1D.	Stem Cell Educator (SCE) therapy: Autologous lymphocytes “educated” by co-culture with CB-derived stem cells in a closed-loop system and reinfused into the patient.	Primary: Long-term safety of SCE therapy. Secondary: Improvement in β-cell function (C-peptide), immune modulation (platelets), and metabolic control.	4 years	- β-Cell Function: T1D patients showed a 90% increase in glucose-stimulated C-peptide after 4 years (p = 0.004). - Metabolic Control: 4/6 T2D patients sustained improved fasting C-peptide levels (from 0.39 ng/ml to 0.82 ng/ml, p = 0.017) and OGTT-stimulated C-peptide levels (p = 0.004). - Platelet Modulation: Platelet count increased significantly in both T1D (p = 0.017) and T2D patients (p = 0.027).	No significant adverse events or tumor formation during 4 years. Common mild effects resolved without long-term consequences.
Bhansali et al., 2017 [61]	Randomized, placebo-controlled, single-blinded	To improve insulin sensitivity and β-cell function in T2DM patients via autologous bone marrow-derived cell therapies using mesenchymal stem cells (ABM-MSCs) and mononuclear cells (ABM-MNCs).	30 patients with 10 in each group: Autologous bone marrow-derived mesenchymal stem cells (ABM-MSC), and Autologous bone marrow-derived mononuclear cells (ABM-MNC, Control)	Patients with T2DM; aged 30–65 years on triple oral antidiabetic drugs and insulin therapy for ≥ 5 years, HbA1c ≤ 7.5%	Group I: ABM-MSC at dose of 1 million cells/kg. Group II: ABM-MNC at a dose of 1 billion cells/patient. Group III: Sham procedure (placebo control)	Primary: ≥50% reduction in insulin requirement while maintaining HbA1c < 7.0% Secondary: Changes in insulin sensitivity and C-peptide response	12 months	- ABM-MSC: Improved insulin sensitivity (p < 0.05) - ABM-MNC: Enhanced C-peptide response (p < 0.05) - Control: No significant improvement	Minor hypoglycemia (low blood sugar) occurred in all groups (19 episodes in ABM-MSC, 15 in ABM-MNC, and 9 in controls). No major adverse events. Whole-body fluorine 18-fluorodeoxyglucose positron emission tomography–computed tomography (18 F-FDG PET-CT) revealed no abnormalities.

Inclusion and exclusion criteria

Inclusion criteria

• Study Type: Randomized controlled trials (RCTs); phase I/II clinical trials were included.

• Population: Adults and adolescents diagnosed with Type 1 or Type 2 Diabetes.

• Intervention: Studies using stem-cell-derived pancreatic beta-like cells or related intervention protocols, such as mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), or induced pluripotent stem cells (iPSCs).

• Outcomes: At least one of the following outcomes:

  • Primary: C-peptide levels, HbA1c reduction, insulin independence.
  • Secondary: Safety profile, adverse events, immune modulation, and quality of life measures.

• Language: Only studies published in English were included to ensure coherence in data interpretation.

Exclusion criteria

• Study Type: Non-peer-reviewed articles, editorials, and opinion pieces were excluded.

• Population: Studies not involving diabetes patients or those focusing exclusively on animal models.

• Outcomes: Studies without measurable outcomes, different targets, or those with insufficient data were excluded.

  See Fig. 1- PRISMA flow chart.

Fig. 1.

PRISMA flowchart summarizing the selection process

Data extraction and management

Data from the included studies were extracted individually by two researchers to strengthen accuracy. The key information extracted included study design, sample size, intervention details, primary and secondary outcomes, key findings, follow-up duration, and safety profiles. Differences were settled through discussions held with a third researcher. A narrative was synthesized to highlight the trends in the efficacy, safety, and clinical applicability of the interventions.

Approach to synthesizing and categorizing findings

Data were summarized qualitatively and quantitatively to identify trends, limitations, and future directions in using stem cells to generate functional pancreatic beta-like cells for diabetes treatment.

To ensure reliability, two reviewers [C.S.O. and V.O.A] independently screened articles, extracted data, and resolved discrepancies through consensus. A narrative synthesis approach was used to present qualitative insights, while quantitative findings were summarized in tables and figures to highlight trends and comparisons.

Study appraisal

The quality of included RCT studies was assessed using the standardized Cochrane Risk of Bias tool. A critical evaluation of each study’s methodology, data analysis, and reporting was done.

Stem cells and their roles in pancreatic beta-like cell generation

Stem cells—the human body’s most distinctive and influential group of cells—have an exceptional capacity for self-renewal. They are unspecialized but possess the ability to differentiate into various body cell types, such as muscle cells, blood cells, and brain cells, during the early stages of development and growth [20–22]. Even after development and growth, the body continues to depend significantly on stem cells to repair damaged or worn-out tissues or cells [23]. See Fig. 2.

Fig. 2.

A flowchart summarizing stem cell therapy for diabetes, mechanisms of actions, and the downstream effects

Types of stem cells

The NIH [20] identifies two major classes of stem cells: pluripotent stem cells and non-embryonic or somatic stem cells, also known as adult stem cells. Pluripotent stem cells, which include both embryonic and induced pluripotent stem cells, can differentiate into all types of human body cells. Adult stem cells, on the other hand, are observed within tissues or organs and can differentiate into the specialized cell type characteristic of the tissue or organ in question [22]. Embryonic and adult stem cells are the main classes of stem cells in humans [20, 21].

• Pluripotent Stem Cells (PSCs): As mentioned earlier, pluripotent stem cells can differentiate into any cell type in the body. They have an infinite capacity for self-renewal when cultivated under favorable growth conditions in the laboratory. These cells enable scientists to create models of diseases and developmental processes, facilitate the testing of novel therapeutic strategies, and inform the development of cell-based therapies [23].

• Embryonic Stem Cells (ESCs): A few days after the fertilization of an ovum with sperm, a hollow ball of cells called the blastocyst is produced. It is within the inner cell mass of this blastocyst that ESCs are derived. Being pluripotent, ESCs give rise to all cell types in the fully developed body, except the placenta and the umbilical cord. They provide scientists with a sustainable source for investigating diseases alongside normal growth and development. Findings from these investigations hold immense potential in developing therapeutic strategies that could lead to the replacement or restoration of worn-out or damaged tissues. Human ESCS (hESCs) are obtained from blastocysts created during an in vitro fertilization (IVF) procedure that were no longer useful [24].

• Induced Pluripotent Stem Cells (iPSCs): These cells have been produced by the bioengineering of ordinary adult stem cells to behave like embryonic stem cells [25] through a process known as reprogramming [20]. In the production of iPSCs, adult or somatic stem cells are reprogrammed into a pluripotent state over weeks by inducing the forceful expression of genes that govern pluripotency. These genes, called master regulator genes, include FACT [26], OCT4, SOX2, NANOG [27], KLF4, and MYC [28]. They repress genes associated with differentiation and, simultaneously, promote the expression of genes that facilitate pluripotency [20, 26]. Traditionally, reprogramming involved the integration of viral vectors to deliver these genes. However, this method posed the risks of insertional mutagenesis [29]. Recent advances have introduced safer and more efficient non-integrative methods, including synthetic modified mRNA (iRNA), episomal vector, microRNAs, and small molecules [29, 30]. These novel approaches not only enhance reprogramming efficiency but also eliminate the risk of genomic integration, making them more suitable for clinical applications.

• Adult Stem Cells (ASCs): Also referred to as tissue-specific or somatic stem cells, these cells are found in a diverse range of tissues, including the liver, bone marrow, brain, heart, and skin, among others [31]. ASCs are unspecialized cells that possess the ability to give rise to diverse cell types of the tissue or organ they inhabit [32]. A typical example is the hematopoietic stem cells (HSCs) of the bone marrow, which generate erythrocytes, leucocytes, and platelets. ASCs are specific to their respective tissues or organs of origin and will not differentiate into cells of other organs – a phenomenon known as multipotency. Put simply, HSCs will not generate hepatic cells or pulmonary cells and vice versa [31]. ASCs reside in tissues for extended periods and primarily replenish lost cells as required, such as the daily regeneration of skin in humans [31].

• Additional examples of adult (multipotent) stem cells include mesenchymal stem cells (MSCs), neuronal stem cells (NSCs), and intestinal stem cells (ISCs). MSCs are unique. They can differentiate into a diverse group of cell types, including chondrocytes (cartilage cells), adipocytes (fat cells), osteoblasts (bone cells), muscle cells, and skin cells [33]. NSCs differentiate into glial and neuronal cells, while ISCs are responsible for the regeneration of intestinal cells.

Stem cell differentiation into beta-like cells: key protocols and methods for generating pancreatic beta-like cells from stem cells

Nihad et al. [34] suggest that a comprehensive understanding of beta islet cell formation in vivo is a crucial starting point for developing various differentiation protocols. By identifying the principal actors and networks involved in the formation of beta islets from the embryonic stage to the mature stage, researchers could replicate the required conditions for differentiation in vitro. The past decade has witnessed the emergence of several key protocols or recipes for differentiating hESCs and iPSCs into mature beta islet cells of the pancreas in vitro. These protocols involve the utilization of various culture methods, including planar, suspension, and 3D cultures [35]. They may include altering the chemical composition of the culture medium, reforming the cells by inducing the forced expression of desired genes, or adjusting the surface of the culture dish [20]. Despite the advances made in the protocol design and differentiation efficiency, the inability to maintain long-term functional maturation of the derived beta-like cells has posed a major limitation [36]. There is concern about their long-term stability and functionality. At the early stages, the cells may express characteristic beta cell markers; however, over time, regression or dedifferentiation may occur. This is thought to be partly driven by epigenetic barriers that interfere with full maturation and sustained identity [37, 38], an area that is unresolved and calls for further investigation.

One protocol utilizes a suspension culture, which involves prolonging the pancreatic progenitor (PP) formation stage by adding growth factors, including keratinocyte growth factor (KGF), SANT1, and retinoic acid, to enhance differentiation efficiency. In an alternative method, a 7-stage planar differentiation protocol is employed, in which latrunculin A is added at the onset of stage 5, thereby eliminating the need for suspension culture. Another protocol uses a series of growth factors and small molecules to guide stem cells through pancreatic developmental stages. Additionally, 3D cultures systems, such as static microwells or rotating suspension, have been employed to further optimize differentiation efficiency, allowing for the generation of homogeneously small-sized islet-like aggregates that possess a similar structure and functionality to traditional pancreatic islets. Other methods of differentiation involve the use of several growth factors and small molecules, such as Activin A, Wnt signaling, and BMP signaling, to regulate the differentiation process. Another protocol combines 11 factors and molecules, including phorbol 12,13-dibutyrate (PdBu), in differentiating PPs into beta-like cells. The xeno-free “GiBi” protocol generates PPs that possess the capability to differentiate into pancreatic lineages. This protocol replaces Activin A with dorsomorphin (DM) [35, 39].

Finally, techniques such as fluorescence-activated cell sorting (FACS) can be used to sort and enrich beta-like cell populations, although the lack of a definitive extracellular marker poses a challenge. Strategies such as negative selection – excluding non-beta-like cells– or the use of transgenic reporters and zinc-binding dyes have been employed to achieve enrichment [35]. These approaches have shown promise in generating functional pancreatic beta-like cells, which express key markers, such as MAFA, INSULIN, and C-peptide. Additionally, the sorted cells exhibit functional characteristics, including glucose-stimulated insulin secretion (GSIS) and improved in vivo glucose tolerance [35].

Yet, the beta-like cells generated from the protocols discussed above are not fully mature; are characterized by polyhormonal expression; and, despite their much-vaunted functionality, fail to exhibit equivalent functional properties to native pancreatic beta cells. Furthermore, mice transplanted with insulin-producing cells (IPCs) typically exhibit short-lived euglycemia. The cells frequently exhibit gene expression profiles characteristic of fetal cells, indicating incomplete maturation, and show suboptimal responsiveness to glucose [18]. These limitations may compromise the clinical significance of beta-like cells.

Growth factors and signaling pathways: role of specific molecules in differentiation

Signaling molecules and pathways

Activin A induces definitive endoderm (DE) formation and promotes pancreatic differentiation. Wnt3a enhances DE formation and pancreatic differentiation by activating Wnt/β-catenin signaling. Noggin inhibits BMP signaling, promoting DE formation and pancreatic differentiation. BMPs (Bone Morphogenetic Proteins) inhibit endoderm induction and pancreatic differentiation. Fibroblast Growth Factors (FGFs) are helpful for early endoderm lineage determination and pancreatic differentiation. Hepatocyte Growth Factor (HGF) stimulates beta cell mass and function [40].

Activin A/LiCl/Noggin

To generate functional pancreatic beta-like cells that produce insulin, embryonic stem cells have to be differentiated through definitive endoderm cells and pancreatic endocrine progenitors. The pancreatic endocrine progenitors then give rise to insulin-producing beta-like cells, which are capable of producing insulin in response to glucose. Activin A, a member of the transforming growth factor beta (TGFβ) superfamily, is a specific molecule with the all-important property of inducing these definitive endoderm cells [40]. Scientists can adjust their concentration, culture conditions, and application time to achieve desired results. Studies show that activin A directs embryonic stem cells (ESCs) into the definitive endoderm germ layer by activating the TGF-beta pathway [41]. Li et al. [42] report that activating signaling pathways such as the Wnt, Nodal, and FGF in the differentiation of embryonic body culture enhanced definitive endoderm cell differentiation, whereas the activation of BMP4 signaling suppressed the process. When combined with LiCl and Noggin, Activin A has been reported to efficiently differentiate endoderm cells from mouse embryonic stem cells, which can then be further guided to become specific types of cells [42, 43].

Differentiation factors, such as cyclopamine, retinoic acid, sodium butyrate, and betacellulin (BTC) promote pancreatic differentiation. Transcription factors important in stem cell differentiation have been studied and shown to play essential roles in studies, including those from mouse models: Pdx1, which is essential for pancreatic development and beta cell function [44]; Nkx6-1, which is involved in pancreatic beta cell development and function [45]; Ngn3, which is essential for endocrine cell differentiation in the pancreas [44]; and Sox17, a marker of DE which is involved in pancreatic differentiation [46].

Other functional molecules include: vitamin C, which enhances beta cell-specific gene expression and promotes pancreatic differentiation; exendin-4; and IGF-1 (Insulin-like Growth Factor 1), both of which support beta cell proliferation and differentiation [40].

Arroyave et al. [47] discussed in their study that combining ascorbic acid and retinoic acid in a four-stage, xeno-free differentiation protocol could enhance beta-like cell differentiation. This study highlights the significance of epigenetic regulation in modulating signal pathways. It demonstrates that insulin-producing cells derived using this method express pancreatic markers with minimal off-target endocrine hormone production [47].

Selective Hedgedon (Hh) pathway inhibitors like SANT-1, are employed to prevent unwanted hepatic differentiation [47]. SANT-1 blocks the Gli-mediated transcription, eliminating Hh-driven hepatic fate bias and allowing for proper pancreatic lineage commitment. During the pancreatic progenitor specification window, cyclopamine, also a potent Hh inhibitor, represses Hh signaling, hence facilitating the pancreatic identity [48]. LiCl, a GSK3β inhibitor, activates the Wnt signaling which works in synergy with Activin/Nodal signs and aids in achieving a robust DE formation [49].

Current preclinical and clinical studies

Preclinical data: overview of animal studies and successful beta-like cell generation in-vitro

Preclinical studies have played a crucial role in expanding our understanding of stem cell-based treatments for diabetes.

A few animal studies have investigated the potential of stem cell-based therapies to restore beta cell function and improve glycemic control. A suitable example lies in the study by Chen et al. [50], in which they successfully generated insulin-producing cells from mouse gallbladder stem cells. The procedure resulted in significant reductions in the glucose levels of diabetic mice and required no gene modification, implying that it was potentially safer and more efficient compared to gene-edited approaches; however, further comparative studies are needed to substantiate this [50]. The researchers also developed a new method for transplanting these insulin-producing cells using a cellulosic sponge, allowing minimally invasive surgery. Similar studies by other researchers [51] reported even more significant reductions in glucose levels in diabetic mice. These studies have employed various stem cell sources, including gallbladder and adult muscle-derived stem cells, and demonstrated their capability to differentiate into functional beta-like cells.

Parallel studies from multiple research groups over the past decade further showcase the potential of stem-cell-derived beta-like cells as a promising experimental source of functional beta-like cells for cell therapy in diabetes treatment. Results from these studies highlight laudable advancements in generating beta-like cells that closely mimic the behavior of native beta cells, thereby paving the way for experimental therapeutic applications in managing diabetes. In their early foundational work, Kumar et al. [52] successfully reversed hyperglycemia in mice using insulin-producing rat bone marrow- and blastocyst-derived hypoblast stem cell-like cells, demonstrating the immense therapeutic potential of this strategy. The findings from this study have important implications for the treatment of T1 DM. The generation of functional beta-like cells from rat multipotent adult progenitor cells (rMAPC) and rat extraembryonic endoderm precursor cells (rXEN-P) demonstrates experimental potential for beta cell replacement therapy. Further validation, however, is warranted to establish reproducibility, safety and long-term functionality.

This approach may offer potential therapeutic options for type 1 diabetic patients whose insulin-secreting beta cells have been destroyed by autoimmune mechanisms; however, concerns about long-term efficacy and immune rejection remain. Using rMAPC and rXEN-P cells as an alternative source of beta cells could surmount the obstacles associated with traditional islet cell transplantation, which is hindered by the shortage of cadaveric islet cells. Furthermore, the study’s findings provide valuable insights into the signals that govern beta-like cell differentiation, which could aid in the development of culture systems to transform other pluripotent stem cells into clinically useful beta-like cells.

Pagliuca et al. (2014) conducted a study centered on the generation of functional glucose-responsive stem-cell-derived pancreatic beta-like cells from hPSCs [53]. Pagliuca and her team employed a novel differentiation protocol for beta-like cell generation, and findings revealed a similarity in characteristics between the generated beta-like cells and those of primary human beta cells. The cells secreted insulin at comparable levels to adult human beta cells and exhibited normal calcium flux in response to glucose stimulation [53] – a hallmark of normal beta cell function. The generated beta-like cells expressed critical beta cell markers [53], in particular NKX6-1 [54], soi1 [55], and C-peptide – additional evidence underscoring their similarity to native beta cells. Structural analysis revealed granules of insulin within the stem-cell-derived beta-like cells [53], which bear a resemblance to those found in primary beta cells. It is important to note that despite these structural similarities, the beta-like cells lacked the full functional maturity of native beta cells, particularly in terms of appropriate dynamic glucose-stimulated insulin secretion. In a separate study published the same year by Rezania et al., using pancreatic progenitors or hESC-derived insulin-secreting cells and a 7-stage protocol, similar functional outcomes were reported, highlighting satisfactory insulin secretion and even diabetes reversal upon transplantation into diabetic mice [56]. Mitutsova et al. [57] discovered that adult muscle-derived stem cells (MDSCs) integrate and differentiate into mature insulin-secreting cells in the pancreatic islets of diabetic mice. This differentiation was observed not only in vitro in culture media but also in vivo following systemic injection of MDSCs in streptozotocin-induced diabetic mice. This discovery presents an alternative approach to treating beta cell deficiencies.

A more recent study, such as that by Nair et al. (2019), optimized differentiation protocols to yield more mature beta-like cells, by replicating endocrine cell clustering during in vitro differentiation of stem-cell-derived beta-like cells into islet-sized enriched beta clusters (eBCs) [38]. Nair and his team further reported that eBCs enabled the formation of cells with features more closely resembling endogenous human islets. These features included glucose-stimulated insulin secretion, dynamic calcium flux responses to glucose, and increased mitochondrial activity [38]. These studies collectively represent advances in the generation of functional beta-like cells with improved potential for therapeutic application. However, there are only a few animal studies, and more studies are required to translate these findings into human clinical trials.

In addition to animal studies, researchers have made notable progress in the in-vitro generation of functional beta-like cells. Some scientists have even gone so far as to reprogram hepatocytes into functional beta-like cells, as reported by Chang et al. [58] in their study. By combining two transcription factors (Pdx1 and Ngn3) and adding a growth factor (PDGF-AA), they achieved efficient reprogramming of both mouse and human hepatocytes. Transplanting these reprogrammed cells into diabetic mice improved glycemic control, offering a potential new treatment for T1DM. A similar study by Galivo et al. [59] also reprogrammed human gallbladder cells into insulin-secreting beta-like cells.

The in vitro functional beta-like cell production and reversal of beta cell dysfunction in animal models form a foundational basis for future clinical exploration. It is worth mentioning that these results are yet to be consistently translated into human studies.

Summary of studies and stem cell types used for beta-like cell generation

Table 1 provides an overview of 13 clinical trials investigating the safety and efficacy of stem cell-based therapies for T1 and T2DM. The included trials employed various stem cells, including mesenchymal stromal cells, hematopoietic stem cells (HSCs), and pancreatic endoderm cells. These trials shared a primary objective of assessing the ability of stem cell-based therapies to improve glycemic control in diabetic patients. Results from some of the trials reported notable improvements in glycemic control, as assessed by reductions in HbA1c levels and increments in C-peptide levels. For example, Dantas et al. [60] reported optimized basal C-peptide levels. They reduced HbA1c levels in patients with T1DM treated with adipose tissue-derived stromal/stem cells and vitamin D. Other trials have recorded reductions in insulin requirements or improvements in insulin sensitivity. Bhansali et al. [61] observed improved insulin sensitivity and reduced insulin requirements in patients with type 2 diabetes mellitus (T2DM) treated with autologous bone marrow-derived mesenchymal stem cells.

The researchers also reported varying safety profiles, with primarily mild and short-lasting adverse events, with the most common ones being injection site reactions, fever, and nausea. There were no reports of severe adverse events, systemic immune responses, or tumor formation in most studies, thus suggesting the safety and viability of stem-cell-based therapy as a treatment option for diabetes. Another notable discovery from these trials was the ability of stem cell-based therapies to lower insulin requirements in diabetic patients. Several trials reported significant reductions in insulin doses [62], with some patients even achieving insulin independence [63].

Aside from its potential therapeutic potential, stem-cell-based therapies can also provide enlightening perspectives into diabetes pathophysiology. Some trials have reported improvements in immune modulation [61, 64] and beta cell function [60, 63], suggesting that these therapies may potentially impact disease progression and severity. The improvements in immune modulation also indicate that these stem cell-based therapies may have anti-inflammatory effects, further contributing to their therapeutic benefits, especially in treating autoimmune conditions such as T1DM, where the immune system mistakenly attacks and destroys insulin-producing pancreatic beta cells. The improvements in beta cell function reported in several trials are suggestive of a strong potential for addressing the underlying cause of diabetes, hence restoring insulin production in diabetic patients, enabling improved blood sugar management, reducing insulin requirements, and ultimately improving the quality of life of patients living with diabetes.

The available data from the studies included in Table 1 suggest that these therapies may offer potential benefits for patients with diabetes. However, further studies are needed to confirm this finding and establish its long-term effectiveness.

Although the findings in Table 1 show the potential of stem-cell-based therapies in improving the glycemic control and beta cell function in both T1DM and T2DM, caution must be taken in their overall interpretation as notable limitations still exist. For instance, in the studies by Ramzy et al., 2021 and Keymeulen et al., 2024, it is imperative to clarify that the goal of the intervention was to replace lost insulin-producing cells, rather than to enhance or regenerate existing beta cell activity [62, 65]. The designs of the clinical trial, selection of patients, type of stem cells, and outcome measures vary with significant heterogeneity. Additionally, although some studies report improvements in C-peptide levels, HbA1c, or insulin requirements, the effects are often short-lived, modest, or dependent on adjunctive therapies such as immunosuppressants or vitamin D supplementation. Insulin independence was not common and primarily limited to early-phase trials or case reports with limited scalability.

Challenges and considerations in stem cell therapy for diabetes

Immunogenicity and transplantation

To trigger an immune response, the recipient’s immune system recognizes the transplanted stem cells, such as ESCs from an unrelated donor, as foreign due to mismatched major histocompatibility complex and/or minor histocompatibility complex antigens [73]. While the induced pluripotent stem cells demonstrate lower levels of immunogenicity compared to the embryonic stem cells, the potential for residual expression of embryonic antigens on the cells and the use of viral or non-viral plasmid-based approaches in reprogramming may alter the expression of several other genes [73]. To mitigate this challenge, the stem cell may be encapsulated in an immuno-isolation device, or immunosuppression therapy may be used [74, 75]. However, a major concern associated with encapsulation is the possibility of limited diffusion of oxygen and nutrients into the cells which may lead to cell hypoxia and impair the cells’ viability and function [66]. To address this limitation, studies such as the one conducted by ViaCyte have demonstrated that the survival and functionality of the grafted islets can be ensured during encapsulation by using semi-permeable immunoprotective polymer devices as they support vascularization [49]. These advanced designs enable the exchange of essential molecules while shielding the cells from immune attack. On the other hand, the lifelong use of immunosuppressive agents poses significant risks - increased susceptibility to opportunistic infections [76] and diabetogenic effects that can worsen glycemic control [77]. Hence, the choice of an immunoprotective strategy must balance of immune evasion, cell viability and clinical safety.

Ethical considerations

Human embryonic stem cells can differentiate into cell types derived from all three germ layers – ectoderm, mesoderm, and endoderm - offering immense potential in regenerative medicine, such as pancreatic beta cell regeneration for the treatment of diabetes mellitus [78, 79]. However, ethical concerns arise because traditional methods of deriving hESCs involve the use of human embryos, raising debates about the moral implications [79]. These ethical considerations have resulted in legislative restrictions or outright bans on hESC research in various countries, thereby limiting scientific progress and delaying potential therapeutic advancements [79].

Comparison with other therapies

Stem cell therapy vs. insulin therapy

Exogenous insulin has been a core component of type 1 diabetes management [80]. The rationale behind this strategy is to regulate blood glucose levels while attempting to reduce the risk of complications associated with diabetes, such as diabetic ketoacidosis [81, 82]. Insulin therapy has become relatively accessible over the years, with advancements in strategies such as insulin pumps and continuous glucose monitors enabling personalized treatment with more predictable outcomes [83]. Despite these advancements, insulin therapy does not replicate the natural, dynamic regulation of blood glucose by pancreatic beta cells [84, 85]. While insulin helps prevent micro- and macrovascular complications, limitations such as frequent glucose monitoring, the need for regular insulin injections, risks of hypoglycemia, and weight gain present significant burdens on patients [86–88]. These challenges are compounded by severe economic disparities in insulin access. In the U.S., insulin list prices rose 15–17% annually from 2012 to 2016, with current gross prices 9.7 times higher than in 33 OECD nations [89]. Over 14% of U.S. insulin users spend ≥ 40% of their post-subsistence income on the drug, disproportionately impacting Medicare recipients because of gaps in coverage [90]. Even with the Inflation Reduction Act’s 435/month cap, affordability remains doubtful for low-income populations. Globally, 35% of patients in low- and middle-income countries (LMICSs) pay out-of-pocket for insulin, often opting for less effective human insulin over pricier analogues (6 times cost difference) [91]. Only 13.6% of high-income countries face similar cost burdens.

Stem cell therapy in diabetes mellitus is being investigated as a potential alternative to insulin therapy, aiming to restore the body’s endogenous insulin secretion. However, the currently available data are primarily preclinical or early-phase clinical trials [85]. This approach targets the root cause of type 1 diabetes and type 2 diabetes, focusing on beta cell exhaustion, rather than simply managing its symptoms [85]. While it aspires to decrease the need for lifelong medications, clinical evidence to support such outcomes in humans is still evolving [85].

However, stem cell therapy is not without challenges. Differentiated beta cell protocols cost $25,000-$50,000 [92], while LMIC clinics offer treatments at $8,000-$12,000. This is still prohibitive where per-capita health spending is low [93]. By contrast, annual U.S. insulin expenses average $4,800-$6,000, creating a cost-efficacy tradeoff between recurring payments and potential one-time cures [90].

The host’s immune system may reject transplanted stem cells, a significant hurdle [94]. Tumorigenesis, additionally, remains a concern, though mitigated by transplanting only differentiated cells [95]. Furthermore, scaling up the production of functional beta-like cells is complex and costly, posing barriers to the widespread adoption of stem cell-derived pancreatic beta-like cell therapy. Insulin access is limited by pricing inequalities, while stem cell therapy, which still remains largely uninsured and experimental, excludes LMIC populations entirely. Immune rejection and tumorigenesis have been raised in the context of stem cell therapies as concerns, especially with regard to integrating reprogramming methods. However, current evidence indicates that stem cells derived using non-integrative reprogramming methods are generally safe for therapeutic use [29, 30].

Stem cell therapy vs. islet transplantation

Islet transplantation is another experimental approach to diabetes treatment that has shown encouraging outcomes [87]. It involves the transfer of healthy, donor-derived pancreatic islets containing beta cells into the liver of a diabetic patient [96]. The success rate of islet transplants improves when sourced from multiple donors, allowing a sufficient number of beta cells to restore glucose regulation [96].

In select experimental models, normoglycemia has been achieved, occasionally without the need for exogenous insulin. However, such results are only preliminary, and consistent replication in human clinical trials is needed [94]. However, some downsides are associated with islet cell transplantation, including the limited supply of cadaveric donors, high costs, and limited procedure availability, which makes it a less scalable approach [85, 86].

Furthermore, transplanted islets are typically recognized as foreign by the recipient’s immune system, necessitating immunosuppression to prevent near-certain rejection [97]. Immune suppressants commonly used in whole organ transplants are also employed to reduce graft rejection [96]. Despite the protective effect of immunosuppressants against rejection, their use compromises the immune system, thereby increasing the risk of opportunistic infections [96].

Over time, graft mass and function have been observed to decrease, likely due to factors such as high metabolic demands, stress, and the effects of immune suppressants [97]. These limitations have prompted the search for renewable sources of beta cells [84].

Stem cell therapy, while not without its setbacks, addresses many of the challenges posed by islet transplantation, particularly by mitigating the need for donor islets [88]. Stem cells can be expanded indefinitely, providing an unlimited supply for transplantation [35, 98]. Advances in genetic engineering have further enhanced the functionality and survival of stem cells. Additionally, encapsulation technologies are being explored to protect these cells from immune attacks [84]. Stem cell encapsulation could reduce tissue immunogenicity and improve the patient’s quality of life by reducing the need for immune suppressants [98]. If successful, this approach could potentially eliminate the need for systemic immunosuppression. Although the clinical application of stem cells is still in its infancy, investigations into long-term outcomes are ongoing, and further refinement is needed to differentiate stem cells into fully functional beta-like cells. While the concept holds potential, it’s premature to consider it a definitive treatment for type 1 diabetes [85].

Future directions

Advancements in protocols: new developments in improving beta cell differentiation efficiency and functionality

There has been progress seen over the years in developing protocols that differentiate stem cells into pancreatic beta-like cells. However, improving efficiency and functionality remains paramount. Over the past decade, the directed differentiation of human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) into stem cell islets (SC-islets) has been extensively studied, and researchers have reported progress toward this goal [99]. A key challenge in the direct differentiation of hiPSCs into beta cells lies in the precise generation of a single cell type from approximately 210 somatic cell types [100]. This stems from the complexity of mimicking the intricate developmental signaling pathways involved in the differentiation process [99]. During embryogenesis, beta cell formation is guided by a highly coordinated series of spatiotemporal cues, including specific growth factors, transcription factors, and microenvironmental signals. In vitro replication of this process would require accurate control of the mentioned factors to ensure that hiPSCs progress through the stages without generating undesired cell types [101]. Recent work, however, has focused on characterizing cell surface markers to isolate specific populations during hPSC differentiation, using cell reaggregation to enhance cell functionality, and identifying Hippo signaling as a critical regulator of endocrine cell formation [102]. Using cell surface markers to enrich progenitor populations is based on the principle that, as early as the definitive endoderm stages, cells have been committed to either the pancreatic or hepatic lineage and can be distinguished by the cell surface protein CD177 and CD275, respectively [103]. Isolating CD177 + cells during the endoderm stage promotes differentiation into beta cells with greater insulin content and enhanced glucose-stimulated insulin secretion [94]. To identify a more specific marker for pancreatic progenitors, microarray analysis was conducted on two populations: pancreatic progenitors (PDX1 + NKX6-1+) and posterior foregut cells (PDX1 + NKX6-1-), generated using distinct differentiation protocols [104]. The analysis revealed that Glycoprotein 2 (GP2), a cell-surface protein, was significantly enriched in PDX1 + NKX6-1 + pancreatic progenitors derived from human pluripotent stem cells (hPSCs) and in human fetal embryonic tissue. Further sorting of GP2^high and GP2^low populations demonstrated that the GP2^high population produced a higher proportion of C-peptide + cells, which exhibited a twofold increase in insulin secretion compared to the GP2^low population [104].

Islet morphology is vital for beta cell maturation and function [105], and studies in adult rat pancreatic islets reveal that single islet cells have impaired function compared to intact islet cells [106]. This suggests that islet cell coupling is essential for insulin secretion, and hence, stem cell scientists have focused on cell aggregation and clustering to improve differentiation protocols. Reaggregating pancreatic progenitor cells and culturing them overnight in suspension enhanced the expression of islet endocrine cell genes and increased human C-peptide levels [107]. Another recent development in improving beta-like cell differentiation efficiency and functionality is the identification of the role of Hippo signaling. Researchers found that by confining pancreatic progenitors to single cells on special glass slides, they were able to maintain high PDX1 expression and promote the expression of NEUROG3 while lowering YAP1 levels [108]. YAP1, a key factor in the Hippo signaling pathway, controls the growth and formation of pancreatic progenitors. As progenitors differentiate into endocrine cells, YAP1 is downregulated, and altering its activity can enhance the formation and function of beta-like cells [91, 92]. However, overexpression of a stabilized form of YAP (YAPS6A) impairs endocrine cell development, which can be corrected by inhibiting YAP [109].

Clinical translation

The clinical translation of hPSC-derived beta-like cells faces two major challenges that remain substantial obstacles: generating functional, fully mature beta-like cells suitable for transplantation and safeguarding these cells from immune attack [102]. Although there is recorded improvement in the quality of beta-like cells generated by in vitro differentiation protocol, there remains a need to create functional beta-like cells that exhibit insulin secretion very similar to primary human beta cells. Velazco-Cruz et al. observed, when they carried out a comparative study of their earlier and updated differentiation protocols, that hPSC-derived beta-like cells produced using the revised protocol showed improved first- and second-phase insulin secretion, suggesting better cell functionality [110]. Despite this, insulin secretion levels remain lower than those of primary human islets, indicating that further optimization is still possible. Another drawback hindering the clinical translation of hPSC-derived beta-like cells is the challenge of preventing both allo- and autoimmunity. Protecting transplanted cells with lifelong immunosuppression can lead to serious side effects, such as a higher risk of cancer and infections [111]. Several approaches can be employed to prevent immune responses, including encapsulating cells in protective capsules, utilizing Treg cell therapy, or editing the genome to remove HLA molecules [112]. Although using patient-specific induced pluripotent stem cells to create beta-like cells seems promising, adapting protocols for each individual would be challenging, making it harder to achieve on a large scale [102]. Despite these challenges, ongoing research continues to refine differentiation protocols and develop strategies to address immune-related difficulties, as achieving clinical translation of hPSC-derived beta-like cells has the potential to revolutionize diabetes treatment [113]. A recent comprehensive review by Sali et al. (2025) provides a detailed account of the development and refinement of hPSC-derived islet differentiation protocols, outlining key advances and ongoing challenges in achieving mature, glucose-responsive β cells and translating these protocols into clinical application [114].

Recently, large-scale efforts have been embarked on to translate stem-cell-derived beta-like therapies into clinical applications. Vertex Pharmaceuticals initiated clinical trials with VX-880. T1DM patients were infused with stem cells alongside immunosuppressive therapy [115]. Preliminary results reported insulin production and a reduction in the need for exogenous insulin use in some recipients. Additionally, a follow-up product VX-264, was developed to address the need for immune protection [116]. These trials represent a step forward in the clinical translation of regenerative therapies.

Conclusion

Stem cell-derived pancreatic beta-like cells are being actively explored as potential therapeutic options for diabetes. Despite the progress observed in generating beta-like cells that are fairly functional, some obstacles remain. Challenges such as achieving full maturation, improving scalability, and overcoming immune rejection present serious barriers to attaining clinical translation. However, with sustained research efforts, stem cell therapy has the potential to pave the way for long-term, sustainable solutions and new models for diabetes treatment.

Abbreviations

DM

Diabetes mellitus

DPP4i

Dipeptidyl peptidase-4 inhibitor

SGLT2

Sodium-glucose cotransporter-2

GLP

Glucagon-like peptide

PSCs

Pluripotent stem cells

ESCs

Embryonic stem cells

iPSCs

Induced pluripotent stem cells

FACT

Facilitates chromatin transcription complex

OCT4

Octamer-binding transcription factor 4

SOX

SRY-box transcription factor

NANOG

Nanog homeobox

KLF4

Kruppel-like factor 4

MYC

Myelocytomatosis viral oncogene homolog

ASCs

Adult stem cells

KGF

Keratinocyte growth factor

GSIS

Glucose-stimulated insulin secretion

BMPs

Bone morphogenetic proteins

FGFs

Fibroblast growth factors

TGFβ

Transforming growth factor beta

IGF-1

Insulin-like growth factor 1

rMAPC

Rat multipotent adult progenitor cells

SC-islets

Stem cell-derived islets

hESCs

Human embryonic stem cells

hiPSCs

Human induced pluripotent stem cells

PdBu

Phorbol 12,13-dibutyrate

Author contributions

IJO conceptualized the study and reviewed the final manuscript. CSA conducted the literature search. KL prepared Table 1; IJO prepared Figure (1) AA conducted the literature search and prepared Figure (2) All authors (IJO, CEA, VOA, CSA, JCO, CKN, MCA, KL, OLA, OA, SQE, OEO, SAJ, ISB) reviewed and approved the final manuscript.

Funding

No funding was received for this study.

Data availability

All data generated or analysed during this study are included in this published article.

Code availability

Not applicable.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.