Mesenchymal stem cells and platelet rich plasma in the treatment of premature ovarian insufficiency: a scoping review

Abstract

Premature ovarian Insufficiency (POI) is characterized by amenorrhea, hypergonadotropic hypogonadism, estrogen deficiency, and reduced follicle counts leading to infertility under the age of 40. It occurs in 1 to 3% of women. Several therapeutic strategies have been explored in clinic for POI. Platelet Rich Plasma (PRP) a blood product applied in regenerative medicine, which is based on the releasing of the growth factors present in platelet. Mesenchymal Stem Cells derived from Bone marrow, adipose tissue or cord blood tissue are undifferentiated cells with a potential for self-renewal and differentiation into multiple mature cell type. Mesenchymal stem cells secretome can stimulate cellular process and activate multipotent stem cells to generate new younger tissue and blood vessels relevant to ovarian rejuvenation and endometrial regeneration. This review provides a critical analysis on novel treatments that have not achieve routine clinical practice status yet but have recently emerged as promising potential therapy.

Introduction

Premature Ovarian Failure (POF) is the state of menopause before the age of 40 where a women’s ovaries stop functioning as they would normally [1]. It is characterized by menopause, an increase in gonadotropin, and a decrease in estrogen levels before 40 years of field [2]. In essence, POF can be seen as a more severe form of POI (primary ovarian insufficiency), where ovarian function is completely lost, however, both terms are used to describe the same underlying condition of early ovarian dysfunction. This condition is also referred to as premature ovarian insufficiency or premature menopause and involves 1% of women under 40 years old and 0.1% of them under 30 years old [3]. POF is multifactorial and is presented as an idiopathic disease. It is correlated to diverse entities mainly genetic flaws, chemotherapy injury, autoimmunity disorders, ovarian surgery or trauma, and infections such as mumps parotitis or tuberculosis. Recent studies propose that premature ovarian aging is among the causal effects of POF, according to some findings [4]. The risk factors associated with POF are diverse, and some of them can be considered causal factors. Among the contributing factors are family history, genetic disorders (particularly those related to the X chromosome like Turner syndrome and Fragile X syndrome), autoimmune disorders, exposure to toxins or environmental pollutants, iatrogenic exposures such as chemotherapy, and certain infectious diseases [5]. POF is diagnosed through several criteria including most importantly:

1. amenorrhea for at least 4–6 months before the age of 40,

2. a high blood level of the follicle-stimulating hormone (FSH) (higher than 40mIU/mL) on at least two blood draws separated by a month [6], low estradiol levels of less than 30ng/L, and post-menopausal signs (hot flashes, vaginal dryness, night sweats, etc.).

In addition, further testing should be performed to rule out a presumed diagnosis. Karyotyping, for instance, is done to evaluate the possibility of genetic disorders such as Turner syndrome. Imaging through transvaginal ultrasound of the woman’s reproductive tract is referred to when ascertaining structural abnormalities in the fallopian tubes, ovaries, or even the absence of the uterus. Additionally, hormonal testing in order to rule out any other condition having a similar profile as POF [7].

POF has both immediate and enduring effects incorporating symptoms (such as hot flushes and night sweats, heart palpitations or headaches) akin to those experienced during natural menopause. It can also lead to osteoporosis, infertility, insomnia, forgetfulness, and poor concentration [8]. Consequently, it is imperative to evaluate and follow-up of the concerned patient, particularly in terms of monitoring their bone density, cardiovascular factors, and lipid profiles. Similarly important are regular gynecological examinations and breast cancer screenings [9, 10].

For diagnosis of POI, a pregnancy test is performed and both serum FSH and estradiol are measured weekly for a duration of 2–4 weeks [11]. Recent guidelines based on the Current European Society of Human Reproduction and Embryology (ESHRE), defines POI as an increased FSH level > 25 IU/L measured twice within a four-week interval [12]. An elevation in the FSH after 1 month supports the diagnosis of primary ovarian insufficiency. The initial diagnosis was made in karyotypically normal women under 35 years old age. Subsequent, amenorrhea and oligomenorrhea that persist for at least 4 months in the absence of hormonal preparations such as oral contraceptives is considered as an indicator of POI [13]. A study was performed by examining 26 patients with presumptive premature ovarian failure. They have irregular menses or amenorrhea based on any single serum FSH concentration > 40 mIU/ml. Three patients complained of thyroiditis. Results showed that FSH levels are not reliable in diagnosing irreversible ovarian failure and indicate in some affected individuals the possibility of ovulation and pregnancy [14]. We should note that it is crucial to exclude the secondary causes of amenorrhea: hormonal disturbance, physical damage to the endometrium and obstruction of the outflow path of the menstrual blood [5] and that when the FSH levels favor the diagnosis of POI, further investigation should be performed in the absence of clear iatrogenic causes [12]. Jiao et al. conducted a study to characterize the ovarian reserve indicators for premature ovarian failure at different stages of the disease with various underlying etiologies. They recruited women with normal ovarian reserve, precursor stage of POI, early POI, and premature ovarian failure. Results have shown that the quantitative changes and cutoff values of AMH (antimullerian hormone) and AFC (antral follicle count) could provide new insights into the prediction and early diagnosis of the POI [15]. The production of AMH occurs exclusively in small ovarian follicles, and its blood levels are utilized to identify diminished ovarian reserve. Normally, the hormone blood level ranges between 1.5 and 4.0 ng/ml therefore, low levels suggest decreased ovarian reserve [11]. Cai et al. conducted a study to investigate the sensitivity of AMH for patients with premature ovarian insufficiency and premature ovarian failure. They recruited a group of 125 women with menstrual disorders. Their results showed that the serum level of AMH decreased gradually in patients with POI and obviously in patients with POF. Hence, AMH can be used as a potential sensitive index for early diagnosis of the two diseases [16].

Rashad et al. performed a study to estimate the role of AMH in predicting the development of POI in women with autoimmune thyroiditis and in assessing the prevalence of thyroid dysfunction in different menopausal stages. The findings indicated a higher prevalence of thyroid dysfunction among all women included in the study, with decreased levels of AMH observed in both naturally and prematurely postmenopausal participants. Therefore, measuring the levels of AMH is recommended as it is considered as a potential sensitive marker for routine screening of POI in patients with autoimmune thyroiditis [17].

Furthermore, a decrease in estradiol levels less than 50 pg/ml indicates hypoestrogenism. Once the levels of FSH levels and estradiol favors the diagnosis of POI, further investigation is needed to investigate possible etiologies including karyotype, adrenal antibodies, FMR1 (Fragile X Messenger Ribonucleoprotein 1) premutation, and pelvic ultrasonography [18]. Baronchelli et al., recruited 269 patients affected by POF to conduct a standard cytogenetic analysis. The karyotype is performed if a patient, who is diagnosed with primary ovarian insufficiency, is < 35 years old or if the FMR2 premutation is suspected [11]. It is done to exclude Turner syndrome and other chromosomal abnormalities. When the karyotype is normal, FMR1 premutation testing should be done to determine the Fragile X premutation carrier status [12]. Structural and numerical chromosomal abnormalities including the X chromosome and other autosomes were found in 27 patients. In 47 patients with 46,XX karyotypes, they used the Interphase Chromosome Flow-FISH technique to identify X chromosome mosaicism rate. The patient group showed a higher rate of aneuploidy compared to the control group. These findings highlight the importance of the X chromosome in the etiology of POF and the potential role of low-level sex chromosome mosaicism in ovarian aging that may lead to premature onset of menopause [19].

Patients diagnosed with POI should annually monitor their HT (hormone therapy) signs and symptoms of thyroid disease and adrenal insufficiency. Based on guidelines, TSH levels should be checked every 3–5 years and every year for patients with positive test of anti-peroxidase antibody. Despite normal adrenal function tests and positive adrenal antibodies results during the annual checkup, it is recommended to conduct an annual ACTH (Adrenocorticotropic Hormone) stimulation test for women as they are at a high risk of developing adrenal insufficiency. Conversely, patients experiencing secondary ovarian failure caused by underlying hypothalamic/pituitary issues should undergo regular monitoring to detect any progression of space-occupying lesions and the development or worsening of hypopituitarism [20]. Hence, studies are performed to investigate the correlation between ovarian antibodies and the diagnosis of premature ovarian failure.

To exemplify, a study was performed to assess an ovarian antibody test system for the diagnosis of autoimmune premature ovarian failure. This was done using a cynomolgus monkey ovary. The study involved 26 young women with 46,XX spontaneous premature ovarian failure, 26 control women with regular menstrual cycles, and 26 control men. The findings revealed that young women with POF exhibited thyroid and gastric parietal cell autoimmunity. Ovarian antibodies, as determined by a commercially available test, were detected in nearly one-third of the normal control women. Additionally, these antibodies were present in half of the young women with POF and were absent in men. Thus, the study indicated that the commercialized ovarian antibodies demonstrate low specificity [21].

Another study was performed to assess the rarity of ovarian antibodies in idiopathic premature ovarian failure. Three groups were recruited. A group of 30 idiopathic POF patients, a group consisting of 12 patients with POF plus an associated autoimmune disease, and a group of 38 controls. Using both ELISA and IFL techniques, the study aimed to define the prevalence of ovarian autoimmunity in these groups. Results have shown that the presence of ovarian antibodies is not a reliable marker for autoimmune POF [22].

In addition, it was found in another study that patients with primary gonadal failure may be part of multiple disorders. Idiopathic Addison’s disease occupies an integral part of these disorders. 5 of 77 patients with idiopathic adrenal insufficiency were positive for antibodies reactive to the theca interna of the ovary, the interstitial cells of the testis, and the adrenal cortex. Results have shown that idiopathic Addison’s disease is an integral part of the underlying polyendocrinopathy of primary gonadal failure [23].

Conventional treatments

Several conventional treatments are put into place for POF. Hormone replacement therapy (HRT) is the primary treatment option for women with POF to alleviate menopausal symptoms including hot flashes, night sweats, sleep disturbances, and vaginal dryness [24]. This treatment option also aims at preventing long-term complications including osteoporosis, cardiovascular disease, and mood changes [25]. Hormone therapy should be individualized based on the patient’s age, symptoms, and preferences, and the type of hormone therapy used should be carefully considered [26].

Overall, women with POF, who have a uterus, should receive both estrogen and progestin, while those without a uterus can receive estrogen alone. Regular monitoring and reassessment of treatment are important to ensure the safety and effectiveness of the treatment [27].

Concerning the hormonal therapies mentioned above, a systematic review examined the use of estrogen-based hormones as a promising therapy for POF [28]. This review suggests that estrogen-based therapy can be a beneficial option for managing menopausal symptoms and preventing complications in women with primary ovarian insufficiency. The review found that this treatment effectively reduced hot flashes and vaginal dryness. It also helped prevent bone loss and decreased the risk of developing cardiovascular disease. However, there was limited evidence on the long-term safety of estrogen-based therapy in this population, and the potential risk of breast cancer should be considered [29].

As previously mentioned, women with an intact uterus need both estrogen and progestin replacement for protection of the endometrium [24]. However, the side effects of this dual therapy must be taken into consideration [30].

In a randomized controlled trial, the Women’s Health Initiative (WHI) assessed the risks and benefits of estrogen plus progestin in healthy postmenopausal women [31]. The trial found that estrogen plus progestin therapy significantly increased the risk of breast cancer, heart disease, stroke, and blood clots in the legs and lungs. On the other hand, it decreased the risk of hip fractures and colorectal cancer. These findings suggest that the use of estrogen plus progestin in healthy postmenopausal women should be carefully considered, weighing the potential risks and benefits on an individual basis [31].

Regarding the effect of POF on bone density, the estrogen-deficient state in women with POF was found to decrease bone mineral density, leading to a decrease in bone mass [32]. Besides lifestyle modifications and calcium and vitamin D supplementation, the first line of treatment for decreased bone mineral density is a systemic hormone replacement therapy that mimics normal ovarian function [33].

In another study, a three-year randomized controlled trial examined the effect of physiological transdermal estradiol and testosterone replacement on bone mineral density in young women with primary ovarian insufficiency (POI). Furthermore, an enzyme-linked immunosorbent assay disclosed that plasma estradiol levels improved and plasma follicle stimulating hormone levels decreased with time in a group of mice treated with a medium dose of Growth Hormone (GH) (0.8 mg/kg) when compared with the POF model group (P < 0.05) [34]. GH may promote ovarian tissue repair, estrogen release and oocyte maturation via activation of the Notch-1 signaling pathway in ovarian tissue.

The trial found that dual hormone replacement therapy effectively increased bone mineral density in the spine and hip, reducing the risk of osteoporosis. The combination of estradiol and testosterone was more effective than estradiol alone in improving bone density. The therapy was well-tolerated with no major safety concerns observed. The results suggest that hormone replacement therapy can be a beneficial treatment option for preserving bone health in young women with POI [24].

Another method to treat women with POF would be the normalization of serum LH levels in women with 46, XX spontaneous primary ovarian insufficiency. In a study done on 137 women with spontaneous POF, a regimen of transdermal E2 for 3 months normalized the LH levels in around one-half of the patients. Theoretically, achieving normal LH levels in these women will improve follicle function [35].

Gonadotropin-releasing hormone (GnRH) antagonists were also found to be effective in managing infertility in women with POF by normalizing LH levels. A case report of a 29-year-old woman with a diagnosis of premature menopause successfully achieved pregnancy through ovulation induction with cetrorelix, a gonadotropin-releasing hormone (GnRH) antagonist. The patient had previously failed multiple attempts of in vitro fertilization (IVF) due to poor ovarian response [36]. Cetrorelix was used to suppress endogenous GnRH secretion. This has led to a decrease in luteinizing hormone (LH) levels and an increase in follicle-stimulating hormone (FSH) levels, which resulted in the recruitment of multiple follicles. The patient was then stimulated with gonadotropins to induce ovulation, resulting in a successful fertilization and hence achieved a pregnancy. The report suggests that cetrorelix may be a potential option for ovulation induction in women with premature menopause who have previously failed IVF due to poor ovarian response field. Dehydroepiandrosterone (DHEA) shown to promote a polycystic environment in the ovaries, with increased levels of active oocytes and decreased atretic effects [37].

Another approach to the pharmacological treatment of POF is related to the mitochondria, as it was found to be closely related to the oocyte quality and the development of the embryo [38]. Coenzyme Q10 (CoQ10), resveratrol, melatonin, and rapamycin are mitochondrial nutrients that have been studied for the improvement of oocytes [39]. Resveratrol, for example, has been shown to halt ovarian aging and aid in oocyte maturation [40]. However, this treatment has not been routinely used in practice because it was found to have anti-acidogenic effects, reducing the rates of pregnancy [41].

Platelet-Rich Plasma (PRP) has been studied as a potential treatment for POF. PRP is a autologous plasma rich in platelets gathered from the patient’s serum [42]. Growth differentiation factor 9 is an oocyte-derived growth factor that is mutated in patients with POF and happens to be found in PRP [43]. Studies have shown that intra-infusion of PRP is said to boost the growth of primary ovarian follicles [44]. Moreover, PRP has been found to have a protective effect against follicular atresia and death in rats with POF [45].

Primary ovarian failure is described as a state of decline in ovarian function resulting in early menopause [46]. This condition seriously impairs fertility due to follicular depletion. It is said in the literature, around 75% of females with primary ovarian failure still have residual dormant follicles in the ovaries [47]. This allowed scientists to develop a new approach to infertility named in vitro activation (IVA) [48]. IVA aims at stimulating the PTEN/PI3K/Akt/FOXO3 pathway that plays a role in the activation of primordial follicles [49]. In this way, patients with POF can have children of their own, using their eggs [38].

Infertility plays a major life-changing role in the lives of patients with POF [6]. Assisted reproductive techniques used in infertile females are also considered in females with POF due to the availability of dormant viable follicles. A woman diagnosed with POF at 35 years of age was able to conceive and deliver a healthy baby after receiving physiologic hormone replacement therapy with intrauterine insemination [50].

In Vitro Fertilization is another widely used assisted reproductive technique that shows promising results in couples struggling with conception [51]. Women with POF can benefit from IVF with donor oocytes, with success rates reaching 50–60% of attempts per embryo transfer, leading to healthy live births [52]. However, patients should be monitored for signs of ovarian hyperstimulation such as nausea, vomiting, and abdominal distension [51]. The risk of this life-threatening condition was approximately 0.2 to 1%, as measured by the WHO [53]. An interesting case regarding the use of IVF as a solution for POF infertility was found in Ireland. A woman received oocytes from her twin sister which were later fertilized by the husband’s sperm via intracytoplasmic injection, and two embryos were implanted in her uterus leading to a healthy twin pregnancy it is important to mention that special ethical considerations exist with sibling gamete donation that do not apply in anonymous oocyte donation [54].

Hormone replacement therapy alone is not effective in inducing pregnancy in women with POF, as compared to a 5.8% rate of live births where IVF cycles and embryo implantation were attempted [55]. Nonetheless, in patients with POF, in vitro fertilization (IVF) using autologous oocytes has yielded discouraging outcomes primarily due to reduced ovarian reserve and inadequate oocyte recruitment and activation. This poses a significant challenge for patients seeking to conceive embryos with their own genetic material [52].

Infertility post premature ovarian failure

Premature ovarian failure is a serious gynecological condition that impairs women’s ability to naturally conceive [56]. It is characterized by a deficiency in sex hormones that leads to a depletion in the ovarian reserve and hence induces pre-term menopause [57]. Females with POF tend to be in a hypoestrogenic state which causes menstrual cycle irregularities and pregnancy failure [5].

In premature ovarian failure, women experience menstrual abnormalities that reduce their fertility, making the occurrence of spontaneous pregnancy extremely rare. Nonetheless, some people with idiopathic POI can have intermittent ovarian activity, which increases their likelihood of becoming pregnant spontaneously and without complications by about 5% [58]. A case of a 27-year-old female patient with a history of premature ovarian failure reported a spontaneous pregnancy only 6 months after hormone replacement therapy [59].

The cause of infertility in POF is still undefined. However, the pathogenesis of the disease itself is the major contributing factor [60]. Women with POF are found to have Follicle-stimulating hormone levels in the menopausal range with a low estradiol level. This state of hypogonadotropic hypogonadism (HH) has multiple etiologies and it is characterized by ovulation disorders. When the condition is acquired, it is usually characterized by functional amenorrhea with low estrogen levels in women leads to suppressed ovarian function [61]. FSH menopausal levels are defined as an FSH level of more than 40IU/L measured two times, 4 weeks apart [15]. Genetic studies have shown that a mutation on the follicle-stimulating hormone receptor gene is directly correlated to the state of high FSH, due to decreased binding capacity and signal transduction, leading to a hypogonadotropic ovarian malfunction [62].

POF is described as a state of ovarian exhaustion that leads to a decrease in the ovary’s ability to grow mature follicles and produce hormones including estrogen [1]. This low level of estrogen has a detrimental effect on women’s ability to conceive. Patients with a low level of estradiol tend to have a significantly higher rate of miscarriage and a lower birth rate compared to women with normal estradiol levels [63]. Estrogen plays a crucial role in preparing the uterus for implantation. Estrogen stimulates the hypertrophy and growth of the uterine spiral arteries. The latter will support the pregnancy and the growth of the fetus [64].

A major cause of infertility in POF is the obvious fact that ovaries has rare number of antral follicles, leading to missed ovulation and amenorrhea [65]. Although the cause can be idiopathic and spontaneous, several factors may trigger POF. Genetics plays a major role in causing infertility in POF. Several genes on the X chromosome have been identified. These genes were found to coordinate the development of germ stem cells to the primordial follicular stage [66]. Any mutation in these genes will impair normal maturation and in turn, decrease fertility.

Autoimmunity is one of the causes of some forms of POF, leading to a significant decline in fertility. There is current evidence that some antigens in the ovary tend to be mistaken for “oneself” antigens and attacked by one’s immune system [65]. Autoimmune-induced POF is characterized by the inflammatory infiltration of the follicles with immune cells and anti-ovarian antibodies leading to irreversible atrophy of the follicles [67].

Although POF presents many challenges in conception, efforts have been made to preserve fertility in women suffering from infertility due to POF.

Embryo cryopreservation is the most common and most effective method of fertility preservation to date. It consists of stimulating the ovaries, retrieving the activated follicles, and inducing fertilization using sperm in the lab. The embryo is then preserved at very low temperatures to be later on thawed and transferred to the uterus by IVF for implantation [68]. This method is specifically feasible in patients at risk of induced primary ovarian failure because of gonadotoxic agents such as chemotherapy [69]. Healthy oocytes are harvested before treatment initiation and reimplanted as embryos later.

Another similar method includes oocyte cryopreservation, which also involves the stimulation of ovaries to produce multiple eggs. These eggs will be collected and preserved for later use [70]. This method is a different choice available to individuals who do not have a partner yet or do not want to use sperm donor, with a mean survival rate of 47%, fertilization rate of 52%, and pregnancy rate per thawed oocyte of 1.52% [71].

This technique has been tested in younger girls with Turner syndrome. Turner syndrome is a chromosomal disorder that affects females and can result in premature ovarian failure, making it difficult to achieve pregnancy. Fertility preservation options can be considered in women with Turner syndrome. Success rates may be lower compared to chromosomally normal females due to reduced ovarian reserve and decreased egg quality [72]. Nonetheless, a study including 3 girls with Turner syndrome showed promising results despite low ovarian reserve. 4–11 mature oocytes have been preserved after ovarian stimulation without any complications [73]. Even though fertility preservation may be feasible in girls with cancer or other conditions that require gonadotoxic treatments during childhood, each case should be considered on its own. The efficacy of fertility preservation techniques in prepubertal girls is currently limited, but research into methods such as ovarian tissue cryopreservation is ongoing. The safety of fertility preservation techniques in prepubertal girls is also a concern, particularly due to the risk of re-implanting cancer cells during transplantation. The authors suggest that multidisciplinary teams, including oncologists, fertility specialists, and pediatricians, should work together to determine the feasibility and safety of fertility preservation options in individual cases [74].

Another method for fertility preservation in females struggling with infertility is ovarian tissue cryopreservation and transplantation. This method not only preserves the reproductive function of the ovary but its endocrine function as well, which can restore the entire reproductive cycle, giving promising results [75]. Among the 12 women who underwent total hysterectomies followed by transplantation of the complete ovarian cortex, 11 patients experienced reestablished ovulation, and 9 out of 12 maintained regular ovulation for a period of two years post-graft [76]. This method includes surgical removal of ovarian tissue, cryopreserving the tissue, and re-transferring it for fertility preservation [77]. Ovarian tissue cryopreservation followed by transplantation or follicular in vitro maturation is an experimental approach for females who still do not have a partner and prepubertal girls who cannot undergo ovarian stimulation [78]. After thawing the frozen ovarian tissue, it can either be transplanted back into the ovarian fossa, orthotopic transplantation, or placed subcutaneously, heterotopically [79]. The heterotopic tissue was able to achieve a 4-cell embryo but live pregnancies have not been recorded in humans yet [28, 29]. On the other hand, there has been evidence of live births resulting from ovarian tissue transplanted orthotopically [80], but the risk of malignant tissue reseeding is still on the line, in patients with toxin-induced POF [68].

Another area of investigation includes the in vitro maturation of ovarian follicles from the ovarian tissues retrieved during surgery to produce eggs ready for fertilization. However, this method is still under investigation [81].

An interesting study combined several methods mentioned above to study the success rate of fertility preservation in women with POI. Participants underwent ovariectomy for the retrieval of ovarian tissue and preservation. After thawing, the tissue was treated with AKT stimulators, known to activate follicular growth, and retransplanted in the pelvis. Almost half of the patients showed residual follicles on histology after transplantation, with around 24 follicles retrieved from 6 of these patients. After in vitro fertilization and embryo transfer into 4 patients, three of these women developed a pregnancy leading to two viable pregnancies and one miscarriage [82]. Although this method shows promising results, numerous factors still need to be considered.

These techniques have changed the face of infertility in women with POF. Some of these techniques have been used for decades. The process of thawing and freezing is well-developed and reliable. However, the process of ovarian stimulation, egg retrieval, and transfer can be emotionally and physically draining [83].

The success rate of embryo cryopreservation is higher compared to oocyte preservation. However, in embryo cryopreservation, donor sperm or a male partner should be present whereas in oocyte freezing, the female may choose to use them whenever she is ready to [84]. The main issue with fertility in patients with POF is the limited number of ovarian reserves and the low quality of eggs which still poses a limitation for the various fertility preservation techniques mentioned above, which is why there is still some uncertainty in the success of such procedures and the rate of pregnancies [85]. When it comes to ovarian tissue preservation, the method is still considered an experimental technique that has not been approved yet for clinical use. It is important to emphasize the risk of reimplantation of cancer cells when transferring ovarian tissue back into patients with chemotherapy-induced POF [86]. Finally, a major limitation is the financial burden these procedures put on the individual’s [87].

Mesenchymal stem cells and secretome

Mesenchymal stem cells (MSCs) are multipotent cells that were initially found mainly in bone marrow, other sources include adipose tissue, bone marrow, dental pulp, mobilized peripheral blood, and umbilical cord [88]. MSCs differentiate in a variety of cells including osteoblasts, chondrocytes, and adipocytes. It is noteworthy that MSCs can be obtained and grown in clinical settings from various tissue sources using minimally invasive techniques, which can help to address ethical concerns surrounding the use of human stem cells in clinical research [89].

Moreover, MSCs can differentiate into multiple cell types, which can provide diverse therapeutic benefits when utilized in medical treatments [90].

To address the complexity of characterizing hMSCs from various biological sources, the International Society for Cellular Therapy (ISCT) has established three essential criteria to verify the stemness characteristics of MSCs. These criteria include the ability to adhere to plastic surfaces when cultured in vitro, expression of surface antigen markers CD73, CD90, and CD105 while downregulating the expression of CD34, CD45, CD14 or CD11b, CD79α or CD19, and HLA-DR markers, and the capacity to differentiate into different mesodermal cell types such as adipocytes, chondrocytes, and osteoblasts in vitro or in vivo [91].

Furthermore, the ISCT has proposed three supplementary conditions in 2019 to enhance the terminology used for MSCs and prevent ambiguity between mesenchymal stem cells and mesenchymal stromal cells [92].

MSCs exhibit a high capacity for regeneration by releasing a range of bioactive trophic factors that activate neighboring parenchymal cells necessary for initiating the healing process in damaged tissues [93]. This mechanism contrasts the traditional MSC differentiation and cell replacement approach. These bioactive factors regulate the local immune system, promote angiogenesis, prevent cell death, and encourage the growth, multiplication, and specialization of resident cells specific to the tissue [94]. Consequently, MSCs are regarded as promoters of tissue repair and regeneration through the secretion of trophic mediators [94].

The secretome, a collection of trophic factors produced by mesenchymal stem cells (MSCs), plays a crucial role in various biological functions, particularly in dermatological applications [95]. It has been utilized as an active ingredient in cosmetics and anti-aging products, demonstrating its ability to diminish wrinkles and enhance skin moisture [9, 10]. Furthermore, the secretome promotes hair growth, accelerates skin healing, and facilitates scarless recovery by stimulating the proliferation and movement of dermal fibroblasts. It also exhibits antimicrobial effects against S. aureus and E. coli, which are essential for healing the skin [96]. Additionally, the secretome acts as a protective agent against UV radiation-induced photoaging. It reduces cell death and DNA damage in keratinocytes, and when combined with platelet-rich plasma, it can slow down the progression of osteoarthritis [97]. The use of MSCs’ secretome also accelerates the regeneration of subchondral bone vasculature, leading to faster repair of damaged bone [98]. The secretome of MSCs has been the focus of much research in recent years, as it has been found to have many potential therapeutic applications. Studies have shown that the secretome of MSCs can promote angiogenesis, reduce inflammation, and improve tissue repair and regeneration [99]. The use of MSC secretome for therapeutic purposes, also known as conditioned medium, has shown potential in a variety of applications, including wound healing, tissue engineering, and autoimmune diseases [95, 100, 101].

Overall, an advantage of using MSCs and their secretome in therapy is that they are relatively easy to isolate and expand in vitro [90]. Furthermore, they are safe and well-tolerated in a variety of clinical settings [102]. While there are still some concerns about the potential for MSCs to form tumors or cause immune rejection, these issues have been largely addressed through careful cell sourcing and processing [103], by avoiding prolonged in vitro expansion, the risk of malignant transformation is decreased. A meta-analysis spanning 15 years concluded that MSC administration is safe across diverse populations, with no significant increase in adverse events compared to control groups [104]. Additionally, MSCs are known for their low immunogenicity, due to the minimal expression of major histocompatibility complex (MHC) molecules. This characteristic enables them to evade detection by the host’s immune system, reducing the risk of rejection [105].

Mesenchymal stem cells and their secretome in stem cell therapy especially in gynecology

Mesenchymal stem cells were first discovered in bone marrow making this source the gold standard for clinical research [106]. The determination of which source to use in the clinical trial is based on both practicalities of use and in vitro characteristics of different resources [89]. BM-derived stem cells (BM-SC) have the advantage of differentiating into hepatocytes, expressing cytochrome P450, and being safe and effective in clinical trials yet at the cost of painful extraction procedures, increased infection rate at the site of extraction and the potential for differentiation being influenced by the donor [107]. Adipose tissue-derived stem cells have the advantage of being more abundant with a higher isolation capacity as compared to BM-SC secreting several angiogenic and antiapoptotic cytokines with strong immunosuppressive properties. However, those cells have a less prominent osteogenic and chondrogenic potential [108]. On the other hand, dental polyps are easily accessible with higher colony-forming cell potential, yet the extraction is invasive and affected by surrounding periodontal tissues [109]. Umbilical cord stem cells are highly available and lack any invasive procedure or ethical concerns with higher engraftment capacity, yet this source has allowed adipogenicity potential [110]. According to Umer et al. (2023), a unique characteristic of the umbilical cord stem cells is the ability to self-renew preserving their multipotency capacity [6, 7]. Mesenchymal stem cells can be obtained from alternative sources, including fetal tissues such as the chorionic plate and amniotic fluid. Among these, amniotic membrane-derived MSCs demonstrate a greater ability to differentiate into bone-forming cells (osteogenic differentiation potency), while chorionic plate-derived MSCs have a stronger capacity to induce the development of fat cells (adipogenicity induction potency) [111]. The use of mesenchymal stem cell therapy in several gynecological disorders including cancer has been well established where mesenchymal stem cells’ use has been implicated in ovarian cancer therapy where once recruited to the site of tumor cells, they induce BMP inhibition [9, 10]. Furthermore, the application of mesenchymal stem cells has demonstrated remarkable pathological improvement in cases of polycystic ovary syndrome (PCOS), a reproductive endocrine disorder. Multiple studies have shown that the use of mesenchymal stem cells in PCOS patients leads to an upregulation of anti-inflammatory markers (IL-10) and a downregulation of pro-inflammatory markers, including IFN-γ, TNF-α, and IL-1β [112, 113]. This reduction in pro-inflammatory markers diminishes their impact on the local ovarian and uterine tissues [11–14]. Moreover, secretory factors also known as the secretome of the mesenchymal cells contain one protein that could inhibit androgen-producing genes thus targeting PCOS therapeutically via decreasing testosterone levels which is a key player in symptomatic manifestations [15–17] (Fig. 1).

Fig. 1.

Injection of MSC and Secretome and PRP in POI

Autologous and allogeneic stem cell therapy in POF based on clinical trials

The integration of mesenchymal stem cells in the treatment regimen of several gynecological disorders has exhibited an increased research interest due to its potential therapeutic outcomes, especially in the treatment of female infertility [114]. To access its efficacy, several criteria were monitored including levels of estrogen, progesterone, FSH, LH, and anti-mullerian hormone in addition to morphological changes in the ovarian follicles. The mechanism of action of mesenchymal stem cells includes their migration to the injured ovarian cell site supporting follicular or stromal cells in recovery [115]. Their therapeutic potential lies in their secretome which is hypothesized to contain bioactive molecules such as growth factors including insulin-like growth factors and vascular endothelial growth factors [116]. For example, vascular endothelial growth factors and anti-apoptotic molecules can regenerate damaged endometrium leading to a drastic drop in their rate of apoptosis, whereas, other signaling molecules regulate CSF expression on granulosa cells also decreasing their apoptotic rate [117]. To assess the mechanism by which mesenchymal stem cells exert their function, several studies were conducted on rat models aiming to assess follicular morphology and proliferation, ovarian function, hormone secretion, and granulosa cell apoptosis in the context of premature ovarian failure [2]. It was shown that ovarian function was restored in rats that were injected with mesenchymal stem cells enhancing follicular growth with a marked increase in the serum levels of the anti-Mullerian hormone, estradiol E2, and progesterone P4 measured via western blot and immunohistochemistry because mesenchymal stem cells secrete growth factors functioning in a paracrine manner rather than differentiation into germ cells thus exerting an antiapoptotic mode of action on the granulosa cells inducing follicular restoration to maintain ovarian function [118]. With the higher incidence of breast cancer in young females and with the detrimental effect of chemotherapy on ovarian function, mesenchymal stem cell transplantation on chemotherapy-induced ovarian failure exhibited substantial results in restoring ovarian function [119]. The ovarian mass in BALB/c mice cyclophosphamide-induced premature ovarian failure was significantly higher in mice receiving human umbilical cord mesenchymal stem cell injections [120]. Subsequently, multiple stem cell injections compared to single injections in mice with ovarian failure induced via busulfan and cyclophosphamide injections showed a higher rate of ameliorating outcomes in the ovarian function where anti-Mullerian hormone levels and hormone receptor expression were higher [4]. However, according to Chen et al., the stability of mesenchymal stem cells declines after isolation and thus pre-handling interventions of the sample by heat shock treatment showed even higher success rates of post-transplant effect with an increased number of follicles and decreased FSH levels and granulosa cells apoptosis rate in a premature ovarian failure model [121]. Moreover, micro-vesicles isolated from mesenchymal stem cells and transplanted alone showed also faster and more efficient recovery of the disruptive estrous cycle [122]. Several signaling pathways were implicated in the effect of transplantation of the mesenchymal stem cells in the restoration of ovarian failure and those were accessed via RNA sequencing analysis which showed the protective mechanism conferred by CSF/PI3K/PKB pathway in granulosa cells and the anti-apoptotic NGF/TrkA signaling pathway [123]. It is important to note that mesenchymal stem cells’ mode of action is via a paracrine fashion; therefore, isolation of those factors from the stem cells into what is known as conditioned media was found to have better therapeutic results in addition to a decrease in the side effects of using stem cells such as the risk of the stem cells differentiating into other stromal cells. Liu et al., 2014, have explored the homing and migration of MSCs to elucidate the underlying therapeutic mechanism in POI. The administration of bone marrow MSCs (BMSCs) through intravenous route mainly migrate to the ovarian hilum and medulla. BMSCs potentially settled in the interstitial of the ovary to restore the function of follicles by their secretion function. Ovarian hilum and medulla are rich in blood vessels, and this may explain the unbalanced distribution of BMSCs in the ovary [123]. An example of the latter is the ability of the multipotent human umbilical cord mesenchymal stem cells to differentiate under conditioned media to any type of cell including oocyte-like structures [124].

Platelet rich plasma: another alternative treatment and part of stem cell therapy for POF

Platelet-rich plasma, or PRP, refers to the portion of blood containing a high concentration of platelets in plasma. It is obtained from autologous blood by phlebotomy, centrifugation, and then isolation from red cells and immune cells [125]. For over 30 years, autologous PRP has been established in the field of regenerative medicine [126]. The latter is an interdisciplinary field that combines life science doctrines and engineering to try to regenerate and restore tissues or organs that have been injured or diseased [127]. Injecting a highly concentrated portion of plasma, by PRP, at the site of an injury, would initiate tissue repair due to the release of active factors. These factors include cytokines, growth factors, lysosomes, and adhesion proteins. The latter proteins initiate the hemostatic cascade, revascularization, and the synthesis of new connective tissues [126]. And of course, cell adhesion plasma proteins are present in PRP including fibronectin, fibrinogen, and prothrombin. In a nutshell, the process of healing happens as follows: α-granules present in platelets are activated and thus fuse to the platelets’ cell membranes. At this level, secretory proteins, such as TGF-beta, are bioactivated when adding carbohydrate and histone side chains. The active proteins will then be secreted and will bind to the target cells’ transmembrane receptors. These cells include fibroblasts, epidermal cells, osteoblasts, and mesenchymal cells. This binding activates intracellular signal proteins which induce the expression of gene sequences that are responsible for tissue repair and regeneration [128]. In brief, PRP depends predominantly on their α-granule content, the release of cell proliferating and differentiation bioactive proteins, and the release of hormones and growth factors responsible for angiogenesis, anabolism, and inflammation control. PRP enhances the healing and regeneration of tissues [38].

PRP has been introduced to the field of regenerative medicine with an emphasis on recovering endometrial growth and pregnancy following IVF. Interestingly, the infusion of endometrial PRP has proven to be promising and has been able to manage chronic endometriosis resulting in live births. Concerning infertility and POI, autologous intraovarian PRP ovaries infusion is encouraging in managing ovarian insufficiency [43]. PRP is seen to restore ovarian function in POI, the injection of PRP is done by laparoscopy in which 0.5 mL of PRP was injected into each ovary, 2 mL were injected into the cervix, and 7 mL intra-uterus [129]. Of utmost importance, the growth differentiation factor 9, GDF-9, is associated with the potential maturation of oocysts and is mutated in POI women. It has been shown that it is present in PRP. In addition, many studies have shown that PRP can develop primitive and primary follicles in the previous stage. Moreover, PRP could restore the microenvironment of ovaries [38].

The application of PRP in ovarian function restoration has been first introduced by Sfakianoudis et al. and Sills et al. [130]. Over the last few years, numerous case series and case reports have been conducted to better understand the introduction of autologous PRP to women with POF. One of the important studies is the one conducted by Pantos et al., 2019, which represents the first report in menopausal and POF literature. In his case series, two women having POF have been able to conceive naturally after PRP administration. The results are presented as follows: the women first have had their menstruation restored and then their hormonal profiles have shown significant improvements. The latter includes an increase in the Anti-Mullerian Hormone AMH and a decrease in FSH [131].

To date, Cakiroglu et al. conducted the largest study on POI women administered an intraovarian injection of autologous PRP with a population of 311 women with POI. Overall, on 311 women, 36 pregnancies have been reported, and 8% of sustained pregnancies or live birth rates. These results can be considered quite promising [132]. Moreover, a systematic review has been conducted over electronic databases by Panda et al., to evaluate the efficiency of intra-ovarian infusion of autologous PRP. The study highlights the implication of the PRP infusion on the improvement of ovarian reserve parameters: increase in AMH or antral follicle count and decrease in serum FSH [133].

The exact mechanism of PRP in ovarian rejuvenation is yet to be understood. Some explanations may support this mechanism. For instance, some platelet cytokines are shown to be part of the regulation of follicle development. It is hypothesized that PRP could be part of proliferative, proangiogenic (through cytokine VEGF), and pro-inflammatory factors, which thus can initiate follicle maturation and/or de novo oogenesis [125]. More studies and especially RCTs are needed to explore more in-depth the use of autologous PRP for POF women [134].

Perspective and outcome

The perspective and outcome of research on POF treatments are promising. However, further studies are needed to establish the exact mechanism and efficacy of these potential treatments. More research is needed to optimize treatment protocols and determine their long-term outcomes [6, 31].

The potential impact of stem cell therapy and PRP in the field of gynecology is significant [135]. These regenerative medicine approaches have the potential to revolutionize the treatment of POF by generating a complete oogenesis process and other gynecological conditions [136]. Stem cell therapy using MSCs has shown promising results in preclinical and clinical studies, with the potential to restore ovarian function and improve fertility outcomes in women with POF [40, 41]. PRP therapy also holds a potential alternative or complementary treatment for POF, as it has been shown to improve ovarian function and hormone levels in several studies [137].

There are however several challenges for stem cell therapy in POF patients. One of the main challenges is optimizing its therapeutic mechanism, dosing, and delivery methods. It is also of the utmost importance to ensure its safety and efficacy in long-term follow-up studies. That is why defining systematic standards and quality standards for MSCs, beginning from culture until reaching actual application, is crucial [138].

A personalized and multidisciplinary approach to POF management is also essential to optimize outcomes and improve the quality of life of POF women. This involves tailoring treatment plans based on individual patient characteristics. It also requires a team of specialists including gynecologists, endocrinologists, and reproductive specialists, to provide comprehensive care and management of symptoms and complications. Regular monitoring and follow-up are also critical to ensure that patients receive the most appropriate and effective treatments for their specific needs [50].

As research in this area continues to expand, it is expected that these treatments will become more widely available and play an increasingly important role in the management of the POF [38].

Conclusion

To date, there is no treatment to restore fertility, and thus no definitive cure for POF [139]. However, with medical innovations, the living conditions of POF women have gained more importance in the last few years, putting as the main target to relieve patients’ symptoms and improve their quality of life [140]. Hormone replacement therapy (HRT) is the mainstay of POF treatment and consists of restoring the normal serum estrogen concentrations relative to the age of the concerned woman. In prepubertal girls, HRT aims to induce puberty and achieve good bone density. And most importantly, HRT works to prevent osteoporosis and cardiovascular diseases [141]. Moreover, it has been shown that HRT helps in relieving symptoms such as hot flashes, and vaginal and urinary symptoms [27]. For several years now, in vitro fertilization (IVF) and oocyte donation have been used as ways to help young women with POF conceive [142]. Complementary and alternative medicine (CAM) is helpful for women with POF. CAM is a combination of health practices that are independent of Western medicine such as psychotherapy, exercise therapy, and dietary supplementation [143]. Awareness should be advocated for better lifestyles to reduce the risks coming with POF, such as cardiac illnesses, by exercising regularly, eating healthy, and avoiding smoking [60].

Stem cell therapy, specifically mesenchymal stem cells (MSCs) is a promising novel treatment for POF. MSCs can differentiate into various embryonic lineages including ovarian cells [115]. Their secretome has been shown to promote tissue regeneration and reduce inflammation. Clinical trials have demonstrated the safety and efficacy of MSC therapy in POF patients. More research is still required to optimize dosing and delivery methods [144].

Platelet-rich plasma (PRP) therapy is another emerging and potential treatment for POF. PRP is a source of growth factors thus promoting tissue regeneration [145]. It improves ovarian function and hormone levels in animal studies. However, more research is needed to confirm its safety and efficacy in humans [146]. In clinical practice, a multidisciplinary approach combining gynecologists, endocrinologists, and reproductive specialists, is advised to support comprehensive care for women with POF. Regular follow-up and monitoring are essential to managing symptoms, preventing complications, and optimizing fertility options [147]. Further research must be focused on developing individualized treatments for POF based on personalized patient characteristics and investigating the potential of regenerative medicine approaches such as MSC therapy and PRP therapy [38]. Understanding the underlying mechanisms of POF, mainly the processes of primordial follicle activation, and identifying new targets for treatment can also lead to novel therapeutic interventions and improved outcomes for women with POF [148].

Author contributions

JG, FH, FK, DT, MY, YS, DC, AI, AA, KA, MY, AC and CK wrote the manuscript. CK, FH, MCH and ACH reviewed the final version of the manuscript.

Funding

Not applicable.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

All authors declare and approved the manuscript for publication.

Competing interests

The authors declare no competing interests.