Urine-derived stem cells in kidney disease: progress, challenges, and future directions

Abstract

Chronic kidney disease (CKD) is a major global health burden with limited treatment options that address the underlying causes of fibrosis or promote regeneration. Urine-derived stem cells (USCs) have emerged as a promising tool in regenerative nephrology, offering a non-invasive and accessible source of multipotent cells with therapeutic potential. Sharing key properties with mesenchymal stem cells, USCs demonstrate paracrine activity, immunomodulation, and efficient extracellular vesicle (EV) production, and have shown anti-fibrotic, anti-inflammatory, and pro-regenerative effects in preclinical models of acute and chronic kidney injury. Recent advances in biomaterials and delivery technologies, including scaffold-free cell sheets and engineered EVs, have further enhanced the potential of USC-based therapies. However, challenges remain, particularly regarding functional integration, delivery optimization, and donor variability. This review summarizes the current progress in USC-based kidney therapy, identifies key limitations, and outlines future directions to support the translation of USC-based interventions into clinical practice.

Introduction

Chronic kidney disease (CKD) is a leading cause of mortality worldwide, with a global prevalence approaching 10% [1]. CKD can arise from a variety of causes, including diabetes and hypertension, and is characterized by progressive and irreversible pathological changes affecting both kidney structure and function. Tubulointerstitial inflammation and fibrosis are central features of CKD, contributing to the progressive disruption of renal architecture and function [2, 3]. Fibrosis is driven by the activation of myofibroblasts and the accumulation of extracellular matrix (ECM) proteins, which impair tissue organization and promote the loss of peritubular capillaries [4]. The resulting decline in renal perfusion and oxygen delivery exacerbates injury, while sustained activation of profibrotic signaling pathways accelerates nephron loss and functional decline [4, 5].

Current treatment strategies primarily aim to slow disease progression by modulating hemodynamic and metabolic pathways. While these therapies have demonstrated efficacy in delaying CKD progression [6, 7], they do not target the underlying mechanisms of fibrosis or promote kidney regeneration. In advanced stages of CKD, renal replacement therapies, such as dialysis, are often required. However, dialysis offers limited improvements in quality of life and does not halt disease progression. Kidney transplantation remains the most effective treatment for end-stage renal failure, yet it is constrained by a severe shortage of donor organs, risk of immune rejection, and the need for lifelong immunosuppressive therapy. Given these limitations, there is a growing interest in regenerative medicine approaches that can address the underlying pathology and restore kidney function.

In mammals, the kidney possesses an innate but limited capacity for regeneration, capable of restoring some tubular function but not replacing lost nephrons. Stem cell-based therapies have therefore gained significant interest as a potential strategy to support kidney repair by modulating immune responses, promoting epithelial recovery, and preserving vascularization. Various stem cells, including mesenchymal stem cells (MSCs) [8], induced pluripotent stem cells (iPSCs) [9], and embryonic stem cells (ESCs) [10], have been investigated for their potential to counteract CKD progression. MSCs, derived from bone marrow (BM-MSCs), adipose tissue (AD-MSCs), or umbilical cord (UC-MSCs), have demonstrated therapeutic benefits through their paracrine effects, including the secretion of anti-inflammatory and anti-fibrotic factors [11]. Similarly, ESCs and iPSCs hold promise due to their ability to differentiate into renal cell types, although ethical concerns, particularly regarding the use of embryos in ESC derivation, and tumorigenicity risks remain significant barriers to clinical translation [12].

Among the various stem cell sources, urine-derived stem cells (USCs) have emerged as a compelling candidate for nephrology applications due to their accessibility, non-invasive collection, and regenerative potential [13]. First identified as a subpopulation of progenitor cells present in voided urine [14], USCs have been proposed to originate from the urinary tract and possibly the renal epithelium [15, 16]. Some studies suggest that USCs may derive particularly from glomerular parietal epithelial cells [15], however, the precise origin of USCs remains debated. Because urine contains a heterogeneous population of exfoliated cells derived from multiple regions of the urinary tract, and composition varies with donor health status, including the presence of inflammation or kidney injury [15, 17], caution is warranted in assigning the origin to USC populations. Further molecular and functional studies are needed to clarify the identity and lineage of USCs. Regardless of this uncertainty, USCs share key properties with MSCs, including multipotency, self-renewal capacity [15, 18], and immunomodulatory capabilities [16, 19–21]. Increasing evidence suggests that many of the therapeutic effects attributed to stem cells are mediated through paracrine mechanisms [22, 23]. Extracellular vesicles (EVs) represent a central component of this paracrine communication. EVs are nano-sized lipid bilayer-enclosed particles released by cells that transfer bioactive cargo, including proteins, lipids, and nucleic acids, to recipient cells [24]. Accordingly, EVs derived from USCs have gained attention as a potential cell-free strategy for kidney repair [25–29]. Taken together, the cellular properties of USCs and their EV-mediated paracrine effects underscore their potential as therapeutic tools in kidney repair.

This review aims to provide a comprehensive assessment of the current progress in USC-based therapies for kidney disease, including emerging evidence on USC-derived EVs as a potential cell-free therapeutic approach. In addition, we compare USCs with other MSC sources to contextualize their biological properties and therapeutic potential. The review will focus on evaluating current applications, identifying key challenges, and outlining essential next steps to translate USCs from preclinical research to clinical applications. By addressing knowledge gaps and proposing strategies to enhance the therapeutic potential of USCs, this review aims to contribute to ongoing efforts in regenerative nephrology.

Literature search strategy and study selection

A structured literature search was conducted to identify relevant studies on USCs and their EVs. The databases PubMed and Web of Science were searched using combinations of keywords and, where applicable, Medical Subject Headings (MeSH), including terms related to “urine-derived stem cells,” “urine stem cells,” “urinary stem cells,” “extracellular vesicles,” “exosomes”, and kidney-related terms such as “kidney,” “renal,” “fibrosis,” “acute kidney injury,” and “chronic kidney disease.” Searches included articles published up to August 31 st, 2025.

Original research articles published in English were considered for inclusion. Studies were included if they addressed the isolation, characterization, biological function, or therapeutic application of USCs or USC-derived EVs in a renal context. Studies were excluded if they were not directly relevant to the biological or therapeutic focus of the review, focused exclusively on non-renal applications, or lacked primary scientific content (e.g. editorials or commentaries). Records retrieved from the databases were merged and deduplicated. In addition, reference lists of included publications were manually screened to identify further relevant literature.

Origin and biological properties of USCs

Voided urine contains a heterogeneous population of cells, including epithelial cells from the renal tubules, ureters, bladder, and urethra, as well as a small fraction of USCs. These USCs can be isolated and expanded in vitro under defined conditions. After collection, urine samples are centrifuged to pellet cells, which are then washed and seeded onto culture dishes in a defined medium. The culture medium typically consists of Dulbecco’s Modified Eagle Medium/nutrient mixture F12 (DMEM/F12) and keratinocyte serum-free medium (Thermo Fisher) supplemented with human recombinant epidermal growth factor and bovine pituitary extract, together with fetal bovine serum and pen/strep. Under these conditions, USCs attach and form colonies within 3 to 7 days. USCs exhibit varying morphological growth patterns, with individual cells appearing as spindle-shaped, rice-grain-like, or cobblestone-like [18, 19, 30–33], while their colonies have been categorized as normal, swarm, and tissue-like phenotypes based on growth patterns and organization [34].

Consistent with the International Society for Cellular Therapy (ISCT) minimal criteria for MSCs [35], USCs express cluster of differentiation (CD)73, CD90, and CD105, and are negative for hematopoietic and endothelial markers, including CD45, CD34, CD11b, CD14, CD19, CD79a, and Human Leukocyte Antigen-DR isotype (HLA-DR) [14–16, 36]. Additionally, they express the pluripotency-associated markers POU class 5 homeobox 1 (POU5F1/Oct3/4), SRY-box transcription factor 2 (Sox2) and MYC proto-oncogene, bHLH transcription factor (c-Myc) as well as Stage-specific embryonic antigen-4 (SSEA4), tumor-rejection antigen (TRA)−1−60 and TRA-1–81, which are typically expressed in ESCs [32, 37]. Unlike MSCs from other sources, such as BM-MSCs and UC-MSCs, which typically undergo around 25–30 doublings before entering senescence [38], USCs exhibit robust proliferative capacity with a doubling time of approximately 21–24 h and the ability to undergo up to 70 population doublings before entering senescence [15]. Furthermore, karyotype analyses have shown that USCs maintain chromosomal stability under standard culture conditions, with normal diploid complements and no detectable structural abnormalities reported from early to mid-passages (P4-P6) [14, 18, 30, 39], and extending up to at least passage 15 [40]. They also exhibit high telomerase activity, which may contribute to their long-term proliferative capacity [15, 39, 41].

USCs have been shown to differentiate into osteoblasts, chondrocytes, and adipocytes under appropriate induction conditions [32], meeting the trilineage criterion for MSCs [35]. Chen et al. further observed two USC subpopulations, one favoring osteogenic and adipogenic differentiation, and the other favoring chondrogenic differentiation [32]. However, reported differentiation capacity varies; one study reported osteogenic and chondrogenic differentiation, but was unable to induce adipogenic differentiation [33], whereas a separate study demonstrated a broader lineage potential, including adipogenic, endothelial, skeletal myogenic, neurogenic, and bladder-associated cell types such as functional urothelial and smooth muscle cells [15]. This suggests that lineage potential may vary depending on cell phenotype, experimental protocols, or donor variability. An overview of USC isolation, marker profile, and differentiation potential is illustrated in Fig. 1.

Fig. 1.

Overview of USC isolation, characterization, and differentiation potential. This schematic illustrates the process of isolating urine-derived stem cells (USCs) from voided urine, followed by expansion and characterization. Urine samples are collected non-invasively from donors and processed to isolate USC populations, which are subsequently expanded in vitro under defined culture conditions. USC morphology is monitored by microscopy, revealing heterogeneous colony-forming phenotypes. Immunophenotypic characterization of USCs displays a defined mesenchymal marker profile, including surface cluster of differentiation (CD)73, CD90, CD105, pluripotency-associated POU class 5 homeobox 1 (POU5F1/Oct3/4), SRY-box transcription factor 2 (Sox2) and MYC proto-oncogene, bHLH transcription factor (c-Myc), and embryonic markers Stage-specific embryonic antigen-4 (SSEA4), tumor-rejection antigen (TRA)−1−60, TRA-1–81, while lacking expression of hematopoietic and endothelial markers. Upon expansion, USCs exhibit distinct morphologies and can differentiate into multiple cell types, including adipocytes, osteoblasts, chondrocytes, neurons, endothelial cells, renal cells, and urothelial cells. USCs can also be reprogrammed into induced pluripotent stem cells (iPSCs) for downstream differentiation. Created with Biorender.com

Although the precise origin of USCs has not been definitively established, current evidence suggests that at least a subset of USCs may be shed from renal structures [15, 42]. Sex-mismatched kidney transplant studies have demonstrated that USCs isolated from female recipients of male donor kidneys contain the Y-chromosome, supporting that some urinary cells can originate from the transplanted kidney rather than the urinary tract [15]. Moreover, USCs express CD224, CD13, nuclear receptor subfamily 3 group C member 2 (NR3C2), paired box (PAX) 2, and PAX8, which are genes associated with the renal tubules, as well as markers typical of glomerular parietal epithelial cells and podocytes, such as synaptopodin and podocin [15]. Furthermore, CD146 is consistently expressed by USCs and has been shown to localize to glomerular parietal epithelial cells and podocytes, but not to renal tubular epithelial cells and the ureteral mucosa (15,42). Notably, CD146 is also expressed in other MSC populations, where it has been associated with an immunosuppressive and potent modulatory subpopulation [43, 44]. Together, these observations suggest that USCs may originate from specialized transitional cells within the glomerulus that share characteristics of both parietal epithelial cells and podocytes. However, these data do not exclude contributions from other regions of the urinary tract, and the overall heterogeneity of cells recovered from urine remains an important consideration. The potential diversity in cellular origin could help explain the heterogeneity observed in vitro, where multiple subpopulations with distinct morphological features have been described.

Stem/progenitor cells in the adult kidney: current debate and implications for USCs

The presence of a validated adult renal stem cell population remains uncertain and widely debated. Early studies by Romagnani and colleagues identified CD133⁺CD24⁺ renal progenitor cells in Bowman’s capsule and proposed that this resident embryonic-derived progenitor population is involved in renal repair [45, 46]. Complementary lineage-tracing, including studies of Six2⁺ nephron progenitors, has shown that renal repair is largely mediated by self-duplication of surviving differentiated cells, rather than by a dedicated stem cell pool [47–52]. To date, no self-renewing population capable of generating nephron structures has been definitively demonstrated after nephrogenesis, and fetal nephron progenitors remain the only confirmed renal stem cells.

Within this context, the classification of USCs must be interpreted carefully. In this review, we use the term “USCs” according to established field nomenclature, based on their in vitro clonogenicity, self-renewal, and multipotent differentiation. However, these properties do not indicate the existence of adult renal stem cells. Current evidence instead suggests that USCs represent a heterogeneous, MSC-like population with renal/urogenital lineage potential, rather than a direct reflection of a resident renal stem cell population.

We therefore emphasize that USCs should not be interpreted as evidence of adult renal stem cells but rather as a translationally useful cell source whose origins remain incompletely defined. Future studies incorporating standardized donor metadata, multi-omics profiling, and rigorous functional assays will be essential to clarify the biological nature of USCs and to resolve the broader controversy surrounding adult kidney stem/progenitor cells.

USCs and USC-derived EVs in kidney disease models

Several studies have demonstrated the renoprotective effects of USCs and their EVs in preclinical models of kidney disease, including ischemia-reperfusion injury, diabetic nephropathy, and cisplatin-induced toxicity (Table 1). As summarized in Table 1, these studies vary substantially in terms of species, injury model, sample size, dosing and route of administration. Across the preclinical studies, USC doses ranged from 1 × 10⁵ to 5 × 10⁶ cells per animal, whereas USC-derived EVs were administered at 20–100 µg EV protein. Delivery routes included intravenous, intrarenal, and intraperitoneal injection, either with single or repeated dosing over several weeks. Despite this administration variability, most studies reported improvements in renal function, as shown by reductions in serum creatinine and blood urea nitrogen, together with improved renal histology characterized by decreased tubular injury, inflammation, and fibrosis, demonstrating a robust therapeutic potential [26, 53–59]. However, it is important to note that the majority of available studies rely on acute injury models with relatively short follow-up periods, which limit conclusions regarding long-term efficacy, durability of response, and relevance to progressive CKD. In addition, sample sizes are often modest, and direct comparisons between studies are challenged by differences in injury severity, outcome measures, and timing of intervention.

Table 1.

Studies investigating the effects of urine-derived stem cells (USCs) and their extracellular vesicles (EVs) in preclinical animal models of kidney disease

Disease model	Induction method	Sample size	Dose (#cells or µg EVs)	Route	Frequency	Key findings	Refs.
USCs
Diabetic nephropathy	High-fat diet followed by STZ-injection (Rat)	Ctrl n = 24 DN Veh n = 24 DN USC n = 24	2 × 106	IV	Every other week, six doses over 12 weeks	Modestly improved cardiac and bladder function while reducing glomerular damage, fibrosis, and kidney dysfunction.	[53]
AKI	Ischemia-reperfusion injury (Rat)	Ctrl n = 6 AKI Veh n = 15 AKI USC n = 15	1 × 105	IR	Once	Reduced serum creatinine and BUN, reduced tubular injury, decreased apoptosis, and increased proliferation. IL-10 and TGF-β were elevated, while IFN-γ and IL-1β were reduced. GFP-labelled USCs were detected at day 7.	[54]
AKI	Cisplatin-induced (Rat)	Ctrl n = 10 AKI Veh n = 10 AKI USC n = 10	2 × 106	IV	Once	Reduced serum creatinine, BUN, and histological damage, increased cell proliferation, and decreased apoptosis. Inflammation and apoptosis-related markers were reduced, while BCL-2 levels were increased. Few USCs were detected in the kidney on days 2 & 4.	[55]
AKI	Ischemia-reperfusion injury (Rat)	No ctrl AKI Veh n = 19 AKI USC n = 19	2 × 106	IV	Once	Improved survival rate, reduced serum creatinine, BUN, histological damage, apoptosis, inflammatory cell infiltration, and oxidative stress.	[26]
Diabetic nephropathy	STZ-injection (Mouse)	Ctrl n = 8 DN Veh n = 8 DN USC n = 8	2 × 106	ICV (1st & 2nd) & IV (3rd)	Once a week for three weeks	Lowered blood glucose, reduced serum creatinine and BUN, improved renal histology, decreased collagen accumulation, macrophage infiltration, and α-SMA expression, while increasing PEDF and reducing NADPH oxidase activity.	[56]
CKD	Ischemia-reperfusion injury & gentamicin (Rat)	Ctrl n = 9 CKD Veh n = 9 CKD USC n = 9	5 × 106	IR	Once	Reduced serum creatinine, improved GFR, reduced collagen deposition and monocyte infiltration, decreased TGF-β expression, and increased SOD-1 expression.	[57]
AKI	Glycerol injection (Mouse)	No ctrl AKI Veh n = 5 AKI USC n = 10	5 × 105	IV	Once	Reduced serum creatinine and BUN, fewer tubular casts, reduced necrosis and apoptosis, and improved renal histology	[58]
AKI	Glycerol injection (Mouse)	No control AKI Veh n = 5–10 AKI USC n = 5–10	1 × 106	IP	Once	USCs detected in kidneys at 3 h, 24 h, and 48 h; localized to tubules and glomeruli. Reduced tubular dilation, protein deposits, and KIM1 + cells; increased Ki67 + cells. No changes in BUN, creatinine, or pathology score.	[59]
AKI	Ischemia-reperfusion injury (Mouse)	No ctrl AKI Veh n = 3–7 AKI USC n = 3–7	1 × 106	IP	Once	USCs detected in kidneys at 3 h, 24 h, and 48 h. No change in KIM1 + cells; increased Ki67 + cells. Pathology score unchanged.	[59]
EVs
Diabetic nephropathy	STZ-injection (Rat)	Ctrl n = 10 DN Veh n = 10 DN EV n = 10	100 µg	IV	Once a week for 12 weeks	Reduced urine volume and microalbumin excretion, reduced apoptosis, and ameliorated mesangial matrix expansion, glomerular hypertrophy, and intraglomerular cell numbers.	[29]
Diabetic nephropathy	STZ-injection (Rat)	Ctrl n ≥ 10 DN Veh n ≥ 10 DN EV n ≥ 10	100 µg	IV	Once a week for 12 weeks	Lowered blood glucose, reduced serum creatinine and BUN, increased podocyte numbers, and decreased apoptotic cell numbers.	[25]
AKI	Ischemia-reperfusion injury (Rat)	Ctrl n = 4 AKI Veh n = 4 AKI EV n = 4	20, 40, or 80 µg	IV	Once	Reduced serum creatinine and BUN levels, decreased tubular cell apoptosis, interstitial fibrosis, and inflammatory cell infiltration, with no observed dose-effect relationship.	[27]
AKI	Ischemia-reperfusion injury (Rat)	No ctrl AKI Veh n = 19 AKI EV n = 6	20 µg	IV	Once	Increased survival rate and reduced serum creatinine and BUN levels.	[26]
AKI	Ischemia-reperfusion injury (Mouse)	Ctrl n = 6 AKI Veh n = 6 AKI EV n = 6	20 µg	IV	Once	Reduced serum creatinine and BUN, improved renal injury score, and decreased apoptosis.	[28]

AKI, acute kidney injury; BCL-2, B-cell lymphoma 2; BUN, blood urea nitrogen; CKD, chronic kidney disease; Ctrl, Control; EV, extracellular vehicle; GFP, green fluorescent protein; GFR, glomerular filtration rate; ICV, intracerebroventricular; IFN, interferon; IL, interleukin; IR, intra-renal; IV, intravenous; IP, intraperitoneal; NADPH, nicotinamide adenine dinucleotide phosphate; NF-κB, Nuclear factor kappa B; PEDF, pigment epithelium-derived factor; SMA, smooth muscle actin; SOD, superoxide dismutase; STZ, streptozotocin; TGF, transforming growth factor; TNF, tumor necrosis factor; USC, urine-derived stem cell; Veh, vehicle

Mechanistically, the therapeutic effects of USCs appear to be primarily mediated through endocrine and paracrine signaling, as USCs secrete a variety of soluble factors, including growth factors and cytokines, as well as EVs, that together modulate the injury microenvironment [20, 33, 60]. This is further supported by the limited detection of transplanted cells within renal tissue and by the comparable therapeutic effects observed with USC-derived EVs, which improve renal function, apoptosis, and attenuate inflammatory infiltration (Table 1). The cargo of these EVs, including regulatory miRNAs, cytokines, and growth factors, likely plays a key role in modulating the injury microenvironment [25–29]. This has led to increasing interest in USC-derived EVs as a defined, cell-free therapeutic platform. The biological properties, molecular cargo, and translational considerations of USC-derived EVs are discussed in detail in a dedicated section below.

While most studies support paracrine mechanisms as the primary driver, recent findings suggest USCs may also integrate into and contribute directly to renal structures. Using luciferase-tagged USCs in murine models of acute kidney injury (AKI), Bejoy et al. demonstrated rapid and selective localization to both glomerular and tubular structures [59]. In human iPSC-derived kidney organoids, USCs were incorporated into the organoid structures and co-expressed NEPHRIN and Lotus tetragonolobus lectin (LTL), indicating differentiation toward podocyte- and proximal tubule-like phenotypes (59). These findings challenge the view that USC effects are purely paracrine and suggest that USCs may exhibit injury-responsive plasticity with the potential for direct structural contribution. Such integration has the potential to support renal regeneration, which to date has not been achieved and would likely rely on autologous stem cell sources as differentiated cells are expected to express HLA-DR and become susceptible to immune recognition [61]. Whether such integration can be functional or durable remains to be determined and will require long-term lineage-tracing studies combined with functional readouts of renal integration and contribution.

USC treatment has also been associated with improvements in systemic markers such as blood glucose and oxidative stress in models of diabetic nephropathy [56]. These findings highlight the multifaceted therapeutic potential of USCs, combining local kidney repair with broader immunomodulatory and metabolic effects. Further work is needed to define the specific molecular mediators involved and evaluate optimal dosing and delivery strategies. Notably, most of the preclinical studies have been conducted in AKI models [26–28, 54, 55, 58, 59], with fewer focusing on diabetic nephropathy [25, 29, 53, 56] and CKD [57]. Given the progressive and irreversible nature of fibrosis in CKD, expanding USC research into chronic models is essential to determine whether their benefits extend beyond acute injury, and can modify disease progression.

Comparison with other MSCs within the kidney field

This section focuses on studies directly comparing USCs to other MSC types in the context of kidney therapy, highlighting their distinct functional properties. In a comparative study, USCs exhibited a higher proliferation rate and colony-forming ability compared to AD-MSCs from the same donors [16]. Additionally, USCs demonstrated a stronger differentiation potential toward myogenic, neurogenic, and endothelial lineages. In contrast, AD-MSCs exhibited a preference for adipogenic, osteogenic, and chondrogenic differentiation. Furthermore, USCs demonstrated stronger inhibition of peripheral blood mononuclear cell (PBMC) activation compared to AD-MSCs, indicating a more potent immunomodulatory capacity [16]. In a glycerol-induced AKI model, both USCs and BM-MSCs reduced serum creatinine and BUN levels, with BM-MSCs exhibiting slightly greater efficacy in the early recovery of renal function. However, histological analysis demonstrated comparable levels of renal structural recovery in both treatment groups. Notably, a higher number of USCs were detected within the kidney tissue, and they remained present at later time points compared to BM-MSCs (18 days vs. 9 days for BM-MSCs), indicating improved retention or homing capacity [58]. This suggests that while BM-MSCs may accelerate short-term recovery, USCs may persist longer within injured tissue, potentially supporting sustained repair.

A notable feature of USCs is their expression of Klotho, a protein implicated in kidney protection and regeneration [62]. In CKD, circulating Klotho levels decline markedly with disease progression [63, 64], contributing to increased oxidative stress, inflammation, and fibrosis [65]. The loss of Klotho exacerbates renal dysfunction by promoting pro-fibrotic signaling pathways, such as transforming growth factor (TGF)-β-mediated epithelial-mesenchymal transition (EMT), which drives fibrosis and ECM deposition [66, 67]. USCs have been shown to express significantly higher levels of Klotho compared to MSCs derived from adipose tissue, bone marrow, and umbilical cord, indicating a unique mechanism for renal protection [68]. Notably, USC-derived Klotho has been shown to suppress fibrosis in vitro by inhibiting EMT, further supporting its potential therapeutic role [68]. Additionally, a cell culture method was developed to enhance Klotho expression in USCs, in which cells were maintained in a customized Klotho activation medium supplemented with factors known to stimulate Klotho expression; however, the exact formulation was not disclosed for patent-related reasons [69]. This suggests that optimizing culture conditions may further enhance their renoprotective effects.

These properties position USCs as a promising candidate for kidney therapy, offering advantages such as strong proliferation, a tendency toward renal-like differentiation, and high expression of Klotho. While BM-MSCs may contribute more effectively to early functional recovery, the intrinsic Klotho expression in USCs could provide a longer-term benefit by mitigating fibrosis and preserving kidney structure. Together, these features suggest that USCs may represent a superior or more versatile alternative to traditional MSC sources for CKD treatment.

Translational and clinical considerations

The pathway from preclinical promise to clinical application involves balancing the inherent strengths of USCs with the challenges of manufacturing, safety, and regulation. Figure 2 provides an overview of these key factors, which are discussed in the following subsections.

Fig. 2.

Translational and clinical considerations for USC-based therapies. This figure summarizes key factors influencing the clinical translation of urine-derived stem cell (USC)–based therapies. Advantages include non-invasive sampling of USCs from urine, urological origin, low immunogenicity, and a diverse secretory profile as well as consistent, high-yield extracellular vesicle (EV) production with characteristic size distributions and EV marker expression across different studies. Challenges include phenotypic cellular heterogeneity, donor-to-donor variability related to age and disease status, the translational gap between preclinical models and clinical application, and issues related to scalability and long-term tracking after administration. Regulatory aspects summarize considerations for clinical translation, including gene editing approaches, the need for GMP-compliant manufacturing and standardization, regulatory classification, and the potential of USC-derived EVs as a scalable and lower-risk alternative to live cell therapies. Created with BioRender.com

Advantages and challenges of USCs

The translation of USC-based therapies depends on both their intrinsic biological properties and the feasibility of robust, standardized, large-scale production. Several characteristics make USCs an attractive cell source; however, these advantages must be balanced against practical and biological challenges that may affect their consistency, potency and clinical performance.

One of the primary advantages of USCs is the non-invasive nature of collection, which enables repeated sampling and facilitates the potential use of autologous cells. Moreover, USCs retain stemness characteristics over multiple passages, with robust proliferative and differentiation capacities [15]. Their differentiation potential toward relevant lineages, including endothelial, myogenic, and neurogenic, further underscores their applicability in regenerative strategies, especially toward kidney-specific treatments [37]. As previously mentioned, USCs exhibit chromosomal stability and sustained telomerase activity under standard culture conditions, features that support their proliferative potential and suitability for in vitro expansion [14, 15, 18, 30, 39, 40]. However, ensuring that these characteristics are consistently maintained during large-scale manufacturing remains a key translational challenge. Evidence from MSC-based research indicates that prolonged in vitro culture can lead to phenotypic drift, including morphological changes, reduced differentiation potential, and increased senescence markers [70], which may compromise therapeutic efficacy [71]. These observations highlight the need for standardized, GMP-compatible expansion protocols, defined passage limits, validated release criteria, long-term storage, and post-transplantation stability to ensure reproducible cell quality and functionality.

For translational manufacturing, xeno-free and chemically defined culture systems will be essential to meet regulatory requirements and minimize batch-to-batch variability. Differences in media formulations and culture supplements may limit reproducibility across laboratories. Future efforts should therefore prioritize transparent, standardized media formulations and harmonized manufacturing workflows. In addition, the development of potency assays remains a critical unmet need. For USC-based products, feasible potency readouts may include in vitro assays assessing immunomodulatory capacity (e.g., suppression of T-cell proliferation or PBMC suppressor assay [72]), anti-fibrotic activity, measured by attenuation of TGF-β–induced collagen in renal fibroblasts, and cytoprotective effects, evaluated using injured renal epithelial cells exposed to hypoxia, cisplatin, or oxidative stress. Additional readouts may include defined secretome or EV cargo profiles, for example, reproducible miRNA or protein signatures associated with functional activity [73].

Like other MSC sources, USCs exhibit low immunogenicity, making them a promising candidate for both autologous and allogeneic applications. They do not express HLA-DR, a key class II HLA glycoprotein responsible for triggering immune reactions [16, 34], and secrete immunomodulatory factors that actively shape immune responses. In line with this, USCs have been shown to suppress immune cell proliferation and are less susceptible to immune-mediated cytotoxicity compared to BM-MSCs [19, 20]. Together, these findings suggest that USCs not only evade immune recognition but also actively modulate immune responses, supporting their suitability for allogeneic applications in paracrine- or EV-based strategies. By contrast, applications involving differentiation into renal cells for structural regeneration would necessitate autologous sources, as HLA-DR expression following differentiation makes them vulnerable to immune detection [61]. However, if autologous USCs cannot be consistently expanded or reprogrammed to achieve sufficient potency, the establishment of standardized allogeneic USC platforms may represent a more scalable translational alternative.

Preclinical safety assessments further support their translational potential, with no reported adverse effects on mortality, general health, or organ function following USC administration [69], and tumorigenicity assays indicate that USCs do not form tumors post-transplantation, reinforcing their safety profile [15, 69]. However, it should be noted that these safety assessments were conducted in immunodeficient murine models, which lack functional T-cells and therefore may not fully recapitulate immune responses in immunocompetent hosts. These findings may underestimate risks related to immune activation, ectopic engraftment or long-term persistence. Biodistribution studies indicate that USCs transiently localize to injured kidney tissue, but their retention in the kidney is short-lived (2 h to 1 day) [69], although one study observed persistence up to 18 days [58]. Discrepancies across studies likely reflect differences in experimental design, including variation in animal species, strain, age, injury model, and delivery route. It is therefore uncertain whether these differences reflect true biological variation or technical factors such as immune status, organ size, or tracking sensitivity. Notably, pulmonary entrapment has been observed after systemic IV administration [69], highlighting the need to explore targeted delivery approaches, such as intrarenal injection, and to assess thromboembolic risk in future studies. More comprehensive preclinical safety programs should therefore include immunocompetent and large-animal models, long-term follow-up, sensitive cell-tracking approaches, and systematic evaluation of biodistribution and immune responses. In this context, studies employing same-species USCs in large-animal models would be particularly valuable to better capture immunological and translational relevance. Consistent with this direction, a recent porcine kidney perfusion study evaluated EVs derived from porcine USCs in a matched species setting, in which the EVs were administered directly to porcine kidneys during machine perfusion [74]. Importantly, this work demonstrates the feasibility of isolating and expanding USCs from pigs, thereby enabling same-species studies in large-animal models rather than relying on xenogeneic human-to-rodent systems.

Donor characteristics, including health status and age, may also influence USC quality and therapeutic performance. While USCs from patients with certain disease conditions, such as end-stage liver disease, retain their morphology and functional properties [75], USCs derived from patients with diabetes and advanced CKD exhibit impaired telomerase activity and differentiation capacity, as well as increased levels of inflammatory markers, apoptosis, and oxidative stress [39]. These findings suggest that while USCs might maintain their proliferative and differentiation capacities across a broad range of conditions, disease status may influence their therapeutic potential, particularly in CKD settings. Age-related declines in proliferative capacity and differentiation potential, along with increased senescence markers, have also been reported [76]. Nonetheless, one study demonstrated that USCs can still be successfully isolated and expanded from elderly individuals with a chronic illness. Notably, USCs from patients over 70 years old with end-stage liver disease retained typical morphology, proliferative capacity, surface marker expression, and differentiation potential. Furthermore, their antifibrotic effect in preclinical models of acute and chronic liver injury was comparable to that of USCs from healthy donors [75]. These findings highlight the importance of defining donor eligibility criteria and quality control parameters, particularly for allogeneic applications.

Collectively, the favorable immunogenicity profile, lack of tumorigenicity, and encouraging preclinical efficacy support the translational promise of USCs. However, successful clinical translation will require standardized manufacturing pipelines, validated potency assays, and expanded safety assessment beyond short-term immunodeficient models.

Ethical and regulatory aspects

The development of USC-based therapies is expected to follow the regulatory frameworks established for advanced therapy medicinal products (ATMPs). To date, no completed clinical trials investigating USCs or USC-derived EV therapies have been reported; however, an ongoing study evaluating autologous USCs in patients with CKD (ClinicalTrials.gov identifier NCT06071143) will provide an important translational reference point. Clinical studies of MSC- and EV-derived products have progressed to early-phase clinical testing in AKI and CKD, providing established benchmarks for GMP-compliant manufacturing, quality control, and safety evaluation.

USCs present a strong ethical advantage for clinical use, as their collection from urine avoids the destruction of embryos associated with ESCs, a long-standing source of controversy [77]. Similar to other MSC sources, USC procurement does not raise major ethical concerns. However, ethical acceptability alone is not sufficient for clinical translation. Compliance with GMP standards, including the use of xeno-free, chemically defined media, standardized culture expansion protocols, batch-to-batch reproducibility and validated quality control measures, remains essential [77, 78]. To address some of the regulatory and logistical challenges associated with cell therapies, increasing attention has turned toward EVs. USC-derived EVs may offer a scalable and potentially safer alternative, as cell-free products potentially reduce risks related to immune compatibility, long-term engraftment, or tumorigenicity [79]. USC-derived EVs as a cell-free therapeutic approach is discussed further in a later section.

The incorporation of gene-editing strategies introduces additional regulatory considerations. Under existing ATMP and gene therapy frameworks, products involving stable genetic modification require extensive safety assessment, including evaluation of genomic stability, off-target effects, and long-term risk. At the same time, the regulatory classification of engineered EV-based products remains less clearly defined, as current frameworks were primarily developed for cell- and gene-based therapies rather than cell-derived vesicle therapeutics [80]. Consequently, engineered EV products may face increased expectations regarding product characterization and manufacturing, including demonstration of identity, purity, potency, cargo loading consistency, and batch-to-batch comparability. This evolving regulatory landscape may therefore introduce additional complexity for the clinical translation of engineered EV-based therapies.

Recent technological innovations

Building on the biological properties of USCs, recent work has concentrated on technological innovations that aim to translate these cells into practical applications. In this review, we focus on advances in delivery strategies, the development of EV–based approaches, and applications in disease modeling (Fig. 3).

Fig. 3.

Recent technological innovations in USC-based applications. This figure highlights three major areas of innovation in urine-derived stem cell (USC)-based applications. First, strategies for USC delivery aimed at improving renal targeting include systemic administration as well as localized approaches such as subcapsular, intrarenal, and intra-arterial injection, in addition to scaffold-, hydrogel-, or cell sheets-based platforms. Second, USC-derived extracellular vesicles (EVs) represent a promising cell-free therapeutic alternative; these vesicles express characteristic surface markers (e.g., tetraspanins and adhesion molecules) and carry bioactive cargo, including RNAs, miRNAs, and proteins, that can attenuate inflammation, fibrosis, oxidative stress, and apoptosis. Third, beyond therapeutic applications, USCs can be used for disease modelling, either through direct differentiation into renal lineages or by reprogramming into induced pluripotent stem cells (iPSCs) to generate kidney organoids, enabling personalized and mechanistic studies of kidney disease. Created with BioRender.com

Delivery

Effective delivery remains a key challenge in realizing the therapeutic potential of stem cell-based approaches for kidney disease. Most insights into delivery routes, biodistribution, and retention come from studies using BM- or AD-derived MSCs in preclinical rodent models [81]. In these studies, intravenous injection is the most common route, but it often results in entrapment of cells in the lungs and liver, limiting kidney-specific localization. In comparison, local delivery methods, including intra-arterial, subcapsular injection, and scaffold-supported implantation, have been shown to improve renal retention and, in some cases, therapeutic efficacy [81]. In contrast to the broader MSC literature, no studies have investigated optimal delivery strategies for USCs in preclinical models of kidney disease. As summarized in Table 1, most USC studies have relied on systemic administration in small animal models. Only a limited number of reports have explored localized delivery routes, such as intrarenal injection [54, 57]. This gap underscores the need for future studies that incorporate delivery innovations developed in the broader MSC field, including bioengineered scaffolds and kidney-targeted administration.

Biomaterial-based approaches, such as injectable hydrogels and scaffolds, have shown encouraging results in preclinical MSC models by improving cell survival, retention, and local integration within injured tissues [82]. However, scaffold-based strategies may be better suited for structurally defined tissues such as bone, where architectural support is essential. In contrast, the kidney’s soft, highly vascularized microenvironment presents challenges for integrating rigid or long-lasting scaffolds and may instead benefit from more adaptable or scaffold-free delivery systems [83]. Scaffold-free cell sheet technology has shown encouraging results in preclinical models of AKI. In one study, genome-engineered MSCs were delivered to the kidney surface in mice as a cell sheet using a temperature-responsive polymer. This scaffold-free approach resulted in superior protective effects compared to intravenous delivery [84]. These findings suggest that local delivery platforms preserving the extracellular matrix may enhance therapeutic outcomes in renal applications.

USC-derived EVs as a cell-free therapeutic approach

USC-derived EVs have emerged as a complementary or alternative therapeutic strategy. EVs may capture many aspects of the paracrine and immunomodulatory effects of their parent cells while avoiding risks associated with stem cell therapies, such as tumor formation or vascular occlusion [79]. USCs represent a particularly robust platform for generating EVs as production can be achieved under serum-free conditions while maintaining high viability, efficient transfection capacity, and consistent EV output with defined size and marker expression. In contrast, AD-MSCs show significantly reduced viability under comparable conditions [34]. Furthermore, USCs can be efficiently gene-edited using low-cost, non-viral methods, allowing for the generation of engineered EVs without compromising proliferative capacity [34]. Multiple preclinical studies have reported that USC-derived EVs exhibit beneficial effects in models of AKI and diabetic nephropathy (Table 1). However, the underlying mechanisms behind these effects remain incompletely understood. EV enrichment protocols, dose reporting and characterization vary widely across studies, complicating comparisons and interpretation. As a result, most conclusions rely on associations between EV cargo composition and observed functional outcomes rather than direct causal validation.

Table 2 provides an overview of molecules identified in USC-derived EVs that have been associated with effects in kidney injury models. USC-derived EVs contain a multitude of growth factors, cytokines, and regulatory RNAs that influence pathways involved in apoptosis, angiogenesis, inflammation, and fibrosis. Several miRNAs enriched in USC-derived EVs, including miR-16-5p, miR-146a-5p, and miR-216a-5p have been associated with reduced apoptosis and inflammation and cell survival through modulation of key signaling cascades, including vascular endothelial growth factor (VEGF), Interleukin-1 Receptor-Associated Kinase 1 (IRAK1)/Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB), and Phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling [25–27]. In addition to miRNAs, the long non-coding RNA taurine upregulated gene 1 (TUG1), enriched in EV cargo, has been associated with inhibition of ACSL4-mediated ferroptosis through interaction with the splicing factor Serine/Arginine Splicing Factor 1 (SRSF1), indicating that multiple RNA-mediated mechanisms may contribute to the observed cytoprotective effects [28]. Soluble factors such as VEGF, bone morphogenic protein (BMP)−7, and angiogenin (ANG) have been detected within USC-derived EVs and have been suggested to contribute to cytoprotection and attenuation of fibrotic responses [29]. USC-derived EVs have also been reported to contain cytokines and immunoregulatory proteins, including the B-cell stimulating factors, B-cell activating factor (BAFF), a proliferation-inducing ligand (APRIL), interleukin (IL)−6, and CD40L [85]. Proteomic profiling has also been applied to characterize USC-derived EV cargo. For example, Chen et al. used quantitative proteomic analysis to identify proteins enriched in USC-derived EVs compared with their parental cells, including proteins associated with angiogenesis and wound healing [86]. However, the presence of candidate miRNAs and proteins within EV cargo does not establish causality. Definitive mechanistic validation will require loss- and gain-of-function experiments, including targeted manipulation of EV cargo, use of EV-depleted or cargo-deficient controls, and orthogonal validation methods to confirm pathway engagement in recipient cells. It should be noted, however, that EVs are complex structures containing thousands of different biologically active components, which may have synergistic or opposing effects, thereby complicating the identification of specific causative molecules. While complete molecular deconvolution of EV cargo may not be required for clinical translation, a robust understanding of safety, reproducibility, and functional efficacy remains essential.

Table 2.

Selected mediators identified in USC-derived extracellular vesicles (EVs) and their proposed functions in kidney injury

Mediator/miRNA	Primary target	Main pathway	Reported effect	Refs.
miR-16-5p	VEGFA	VEGF/apoptosis	Protects podocytes, reduces apoptosis and fibrosis	[25]
miR-146a-5p	IRAK1	NF-κB	Suppresses inflammation and cytokine release	[26]
miR-216a-5p	PTEN	PI3K/Akt	Promotes cell survival, reduces apoptosis	[27]
LncRNA TUG1	SRSF1	ACSL4-mediated ferroptosis	Inhibition of ACSL4-mediated ferroptosis	[28]
BMP-7	–	TGF-β/Smad	Inhibition of podocyte apoptosis	[29]
VEGF, angiogenin, and TGF-β	–	Angiogenesis	Increase in glomerular endothelial cell proliferation and glomerular angiogenesis	[29]
BAFF, APRIL, IL-6, and CD40L	B-cell and cytokine receptors	Immune modulation	Induction of B-cell proliferation and IgM antibody secretion	[85]

ACSL4, acyl-CoA synthetase long-chain family member 4; APRI, a proliferation-inducing ligand; BAFF, B-cell activating factor; BMP-7, bone morphogenetic protein 7; CD40L, CD40 ligand; IL-6, interleukin-6; IRAK1, interleukin-1 receptor-associated kinase 1; lncRNA, long non-coding RNA; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells; PI3K/Akt, phosphoinositide 3-kinase/protein kinase B; PTEN, phosphatase and tensin homolog; SRSF1, serine/arginine-rich splicing factor 1; TGF-β, transforming growth factor beta; TUG1, taurine upregulated gene 1; VEGF, vascular endothelial growth factor

As EV-based approaches advance toward clinical application, consistency in media composition, scalability, and enrichment strategies is critical. Incorporation of Quality by Design (QbD) principles is therefore important to ensure that experimental findings remain translatable, while accounting for scale-up challenges, and GMP-compliant production. In parallel, adherence to the Minimal Information for Studies of Extracellular Vesicles (MISEV) guidelines [73] is essential to confirm observed effects can be attributed to EVs rather than contaminating cellular or media-derived components, and to support the appropriate dose-response evaluation.

Compared with live cell therapies, USC-derived EVs offer several advantages, including therapeutic efficacy with lower immunological and safety risks. However, EVs do not fully replicate the dynamic and complex signaling repertoire of live cells. Unlike transplanted cells, EVs cannot respond to microenvironmental cues or engage in sustained crosstalk with surrounding tissues. This lack of feedback-driven modulation may limit their ability to orchestrate complex repair processes, particularly in chronic or multifactorial kidney diseases. On the other hand, although EV composition can vary depending on the originating cell population and culture conditions, the molecular content of a given EV preparation remains fixed after administration [87]. This defined composition may be advantageous, as EVs provide a controlled therapeutic signal without the risk of transplanted cells dynamically altering their behavior in response to the microenvironment. Moreover, their molecular payload can be strategically optimized through cell conditioning or engineering during production, enabling the development of more consistent and fine-tuned EV-based therapeutics [88]. The defined and controllable composition of EV-based products may facilitate standardization and regulatory evaluation, potentially facilitating clinical translation compared with live cell therapies.

USCs in disease modelling

USCs have gained interest as a platform for disease modeling, particularly through their potential to generate iPSCs from a non-invasive cell source [13]. Urine-derived iPSC lines have been established from patients with AKI [89], Alport syndrome [90], and polycystic kidney disease [91], and differentiated into kidney organoids that closely resemble those generated from conventional iPSC sources [92]. These models provide valuable tools for studying disease mechanisms and evaluating therapeutic responses in a personalized context.

Recent studies have specifically explored the use of USCs as a starting population for iPSC reprogramming toward renal lineages. Notably, one study reported that organoids derived from USC-iPSCs exhibited a higher abundance of proximal tubule cells compared to those derived from PBMCs, suggesting a potential advantage in modeling renal epithelial function [93]. While multiple somatic cell types can be reprogrammed into pluripotent states, the cellular origin may influence differentiation trajectories, possibly through residual epigenetic signatures or lineage-specific preferences [94]. This raises the possibility that USCs might possess an inherent bias toward nephron-relevant differentiation.

The functional relevance of these organoids has been demonstrated through their application in modeling kidney injury in vitro, where induced damage replicated pathophysiological features of renal disease [95]. USC-derived iPSCs have also been used to generate patient-specific organoids carrying individual risk alleles. While this approach has only been applied in other disease contexts, such as Duchenne Muscular Dystrophy [96], it underscores the broader applicability of USCs as a non-invasive source for personalized iPSC models.

Beyond reprogramming-based approaches, USCs have also been directly differentiated into renal tubular cells and podocytes [97]. More recent studies have shown that USCs can form kidney organoids, exhibiting renal morphology, expression of tubular markers, and responsiveness to nephrotoxic compounds such as acetone and cisplatin, and displaying structural and molecular features comparable to organoids from tissue-derived kidney cells [98, 99]. This reprogramming-free approach may offer advantages for disease modeling, as it could help preserve disease-relevant phenotypic or epigenetic features that may be lost during iPSC reprogramming.

The ability to derive renal structures from a non-invasive cell source provides a valuable tool for investigating disease mechanisms and screening therapeutic compounds. However, challenges remain, including optimizing differentiation protocols, improving functional maturation, and validating these models against human kidney pathology. In particular, batch-to-batch variation in organoid maturation has been identified as a major confounding factor in disease modeling studies, as it can obscure true differences between patient- and control-derived organoids and reduce the power to detect disease-specific mechanisms [100]. Efforts to reduce variability will be essential for improving the interpretability of patient-specific models and strengthening the utility in identifying disease-associated mechanisms.

Conclusion and future directions

In this review, we have summarized the current progress and applications of USCs in kidney therapy and disease modeling. USCs have emerged as a non-invasive, patient-derived cell source with demonstrated regenerative, immunomodulatory, and anti-fibrotic effects across multiple preclinical models. Their ease of collection, expandability, and para-/endocrine activity position them as a versatile platform for both therapeutic intervention and personalized disease modeling, as well as a supplementary tool that may reduce reliance on animal studies.

Ongoing debate remains regarding the existence of adult renal stem or progenitor cells. Despite studies of progenitor-like populations in the adult kidney, no self-renewing, nephron-forming stem cell type has been definitively established post-nephrogenesis. Consequently, urinary cells should not be interpreted as evidence of a persistent renal stem cell population. USC cultures are heterogeneous, and their composition is likely influenced by donor health status, age, urinary tract origin, and in vitro in vitro expansion conditions. This heterogeneity requires caution when assigning tissue origin or assuming differentiation potential.

While preclinical data increasingly support the therapeutic potential of USCs in kidney disease, several key knowledge gaps remain. The precise origin and cellular identity of USCs are incompletely defined; elucidating these aspects may refine our understanding of their differentiation potential and inform therapeutic applications. Further studies are needed to elucidate the mechanisms underlying USC-mediated effects, including the relative contributions of transient engraftment, para-/endocrine signaling, release of signaling molecules, and/or immunomodulation, as well as how these effects are shaped by donor characteristics, delivery method, and disease context.

Single-cell RNA sequencing (scRNA-seq) represents a promising tool to address several of these questions. High-resolution transcriptional profiling can resolve heterogeneity within USC cultures and enable mapping of USC signatures onto reference kidney and urothelial atlases, thereby providing insight into cellular origin. Comparative transcriptomic or proteomic fingerprinting may further contribute to distinguishing USC subpopulations and identifying markers associated with therapeutic activity, including the phenotypic heterogeneity reported in some cultures [34]. Such approaches could clarify whether morphologically and functionally distinct USC phenotypes represent stable subtypes or culture-induced states. Importantly, systematic functional comparison of defined USC subpopulations in renal disease models will be necessary to determine whether phenotypic heterogeneity translates into differences in therapeutic efficacy. Establishing standardized characterization criteria and linking molecular or phenotypic signatures to functional potency could therefore be critical for identifying the most therapeutically relevant USC populations.

Realizing the clinical potential of USCs will require the implementation of standardized, reproducible methodologies for cell isolation, characterization, and expansion under GMP-compliant conditions. Establishing robust quality-control criteria, including defined release parameters and biologically relevant potency assays, will be essential to ensure batch-to-batch consistency and reproducibility across laboratories and production sites. Early-phase safety and biodistribution studies should be prioritized to assess short- and long-term effects and to inform subsequent clinical translation.

Importantly, these considerations are equally relevant for USC-derived EVs. As EV preparations reflect the biological state and manufacturing conditions of the parent USC population, reproducible EV-based therapies will require rigorous characterization and standardization of both the cells and the resulting vesicle products. Thus, advances in USC quality control and potency assessment will directly influence the clinical reliability of EV-based approaches.

From a translational perspective, continued progress toward clinical application will benefit from a structured, stepwise roadmap. Short-term priorities include further standardization of USC isolation, culture, and characterization protocols, together with the development of robust potency assays and well-defined release criteria. Medium-term efforts should focus on addressing remaining mechanistic questions, conducting systematic biodistribution analyses, and validating findings in large-animal models that more closely recapitulate human kidney disease. Long-term objectives include GMP-compliant scale-up, regulatory alignment, and the initiation of early-phase clinical studies to assess safety and feasibility. Establishing such a prioritized translational framework will be critical for bridging the gap between preclinical evidence and the clinical application of USC- and USC-derived EV-based therapies in kidney disease.

Abbreviations

AD-MSC

Adipose-derived mesenchymal stem cell

AKI

Acute kidney injury

ATMPs

Advanced therapy medicinal products

BM-MSC

Bone marrow-derived mesenchymal stem cell

BUN

Blood urea nitrogen

CKD

Chronic kidney disease

DMEM/F12

Dulbecco’s Modified Eagle Medium/Nutrient Mixture F12

ECM

Extracellular matrix

EMT

Epithelial-to-mesenchymal transition

ESC

Embryonic stem cell

EV

Extracellular vesicle

GMP

Good Manufacturing Practice

HLA-DR

Human leukocyte antigen–DR isotype

MISEV

Minimal information for studies of extracellular vesicles

iPSC

Induced pluripotent stem cell

ISCT

International society for stem cell therapy

MSC

Mesenchymal stem cell

PBMC

Peripheral blood mononuclear cell

QbD

Quality by design

scRNA-seq

Single-cell RNA sequencing

UC-MSC

Umbilical cord-derived mesenchymal stem cell

USC

Urine-derived stem cell

USC-EV

Urine-derived stem cell extracellular vesicles

Author contributions

JCLA conceptualized the review, conducted the literature search, and drafted the manuscript. ATB contributed to the literature review and critical revision of the manuscript. RN supervised the work, guided the overall structure and content, and critically revised the manuscript. All authors have read and approved the final manuscript.

Funding

JCLA and ATB are funded by the Novo Nordisk Foundation (grant number NNF19OC0054481). The funder had no role in the design, writing, or decision to submit this manuscript.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Competing interests

The authors declare no competing interests.