Stem Cells

[Michael Scally MD]

Yang C, Du YK, Wang J, Luan P, Yang QL, et al. Transplanted Adipose-Derived Stem Cells Ameliorate Testicular Dysfunction In A D-Galactose-Induced Aging Rat Model. J Cell Physiol. 2015;230(10):2403-14. http://onlinelibrary.wiley.com/doi/10.1002/jcp.24970/abstract

Glycation product accumulation during aging of slowly renewing tissues may be an important mechanism underlying aging of the testis.

Adipose-derived stem cells (ADSCs) have shown promise in a novel tissue regenerative technique and may have utility in treating sexual dysfunction. ADSCs have also been found to be effective in antiaging therapy, although the mechanism underlying their effects remains unknown. This study was designed to investigate the anti-aging effect of ADSCs in a D-galactose (D-gal)-induced aging animal model and to clarify the underlying mechanism.

Randomly selected 6-week-old male Sprague-Dawley rats were subcutaneously injected with D-gal daily for 8 weeks. Two weeks after completion of treatment, D-gal-induced aging rats were randomized to receive caudal vein injections of 3 x 10(6) 5-bromo 2'deoxy-uridine-labeled ADSCs or an equal volume of phosphate-buffered saline.

Serum testosterone level, steroidogenic enzymes (3-beta-hydroxysteroid dehydrogenase), and superoxide dismutase (SOD) activity decreased significantly in aging rats compared with the control group; serum lipid peroxidation, spermatogenic cell apoptosis, and methane dicarboxylic aldehyde (MDA) expression increased significantly.

ADSCs increased the SOD level and reduced the MDA level in the aging animal model and restored levels of serum testosterone, steroidogenic enzymes, and spermatogenic cell apoptosis.

These results demonstrate that ADSCs can contribute to testicular regeneration during aging. ADSCs also provide functional benefits through glycation suppression and antioxidant effects in a rat model of aging. Although some ADSCs differentiated into Leydig cells, the paracrine pathway seems to play a main role in this process, resulting in the reduction of apoptosis.

 

[Michael Scally MD]

Transplanted Human p75-Positive Stem Leydig Cells Replace Disrupted Leydig Cells For Testosterone Production

Previous studies have demonstrated that rodent stem Leydig cell (SLC) transplantation can partially restore testosterone production in Leydig cell (LC)-disrupted or senescent animal models, which provides a promising approach for the treatment of hypogonadism. Here, we isolated human SLCs prospectively and explored the potential therapeutic benefits of human SLC transplantation for hypogonadism treatment.

In adult human testes, p75 neurotrophin receptor positive (p75+) cells expressed the known SLC marker nestin, but not the LC lineage marker hydroxysteroid dehydrogenase-3beta (HSD3beta). The p75+ cells which were sorted by flow cytometry from human adult testes could expand in vitro and exhibited clonogenic self-renewal capacity. The p75+ cells had multi-lineage differentiation potential into multiple mesodermal cell lineages and testosterone-producing LCs in vitro.

After transplantation into the testes of ethane dimethane sulfonate (EDS)-treated LC-disrupted rat models, the p75+ cells differentiated into LCs in vivo and secreted testosterone in a physiological pattern. Moreover, p75+ cell transplantation accelerated the recovery of serum testosterone levels, spermatogenesis and reproductive organ weights.

Taken together, we reported a method for the identification and isolation of human SLCs on the basis of p75 expression, and demonstrated that transplanted human p75+ SLCs could replace disrupted LCs for testosterone production. These findings provide the groundwork for further clinical application of human SLCs for hypogonadism.

Zhang, M., J. Wang, et al. "Transplanted human p75-positive stem Leydig cells replace disrupted Leydig cells for testosterone production." Cell Death Dis 2017;8(10) e3123. Cell Death and Disease - Transplanted human p75-positive stem Leydig cells replace disrupted Leydig cells for testosterone production

 

[Thaistick]

That could really help out a lot of men.

 

[Michael Scally MD]

[OA] Exploiting science? A systematic analysis of complementary and alternative medicine clinic websites’ marketing of stem cell therapies.

Objective To identify the frequency and qualitative characteristics of stem cell-related marketing claims made on websites of clinics featuring common types of complementary and alternative medicine practitioners. The involvement of complementary and alternative medicine practitioners in the marketing of stem cell therapies and stem cell-related interventions is understudied.

This research explores the extent to which they are involved and collaborate with medical professionals. This knowledge will help with identifying and evaluating potential policy responses to this growing market.

Design Systematic website analysis.

Setting Global. US and English-language bias due to methodology.

Main outcome measures Representations made on clinic websites in relation to practitioner types, stem cell therapies and their targets, stem cell-related interventions. Statements about stem cell therapies relating to evidence of inefficacy, limited evidence of efficacy, general procedural risks, risks specific to the mode of therapy, regulatory status, experimental or unproven nature of therapy. Use of hype language (eg, language that exaggerates potential benefits).

Results 243 websites offered stem cell therapies. Many websites advertised stem cell transplantation from multiple sources, such as adipose-derived (112), bone marrow-derived (100), blood-derived (28), umbilical cord-derived (26) and others. Plant stem cell-based treatments and products (20) were also advertised.

Purposes for and targets of treatment included pain, physical injury, a wide range of diseases and illnesses, cosmetic concerns, non-cosmetic ageing, sexual enhancement and others. Medical doctors (130), chiropractors (53) and naturopaths (44) commonly work in the clinics we found to be offering stem cell therapies.

Few clinic websites advertising stem cell therapies included important additional information, including statements about evidence of inefficacy (present on only 12.76% of websites), statements about limited evidence of efficacy (18.93%), statements of general risks (24.69%), statements of risks specific to the mode(s) of therapy (5.76%), statements as to the regulatory status of the therapies (30.86%) and statements that the therapy is experimental or unproven (33.33%). Hype language was noted (31.69%).

Conclusions Stem cell therapies and related interventions are marketed for a wide breadth of conditions and are being offered by complementary and alternative practitioners, often in conjunction with medical doctors. Consumer protection and truth-in-advertising regulation could play important roles in addressing misleading marketing practices in this area.


Murdoch B, Zarzeczny A, Caulfield T. Exploiting science? A systematic analysis of complementary and alternative medicine clinic websites’ marketing of stem cell therapies. BMJ Open 2018;8. http://bmjopen.bmj.com/content/8/2/e019414.abstract

 

[Spooby]

Transplanted Human p75-Positive Stem Leydig Cells Replace Disrupted Leydig Cells For Testosterone Production

Previous studies have demonstrated that rodent stem Leydig cell (SLC) transplantation can partially restore testosterone production in Leydig cell (LC)-disrupted or senescent animal models, which provides a promising approach for the treatment of hypogonadism. Here, we isolated human SLCs prospectively and explored the potential therapeutic benefits of human SLC transplantation for hypogonadism treatment.

In adult human testes, p75 neurotrophin receptor positive (p75+) cells expressed the known SLC marker nestin, but not the LC lineage marker hydroxysteroid dehydrogenase-3beta (HSD3beta). The p75+ cells which were sorted by flow cytometry from human adult testes could expand in vitro and exhibited clonogenic self-renewal capacity. The p75+ cells had multi-lineage differentiation potential into multiple mesodermal cell lineages and testosterone-producing LCs in vitro.

After transplantation into the testes of ethane dimethane sulfonate (EDS)-treated LC-disrupted rat models, the p75+ cells differentiated into LCs in vivo and secreted testosterone in a physiological pattern. Moreover, p75+ cell transplantation accelerated the recovery of serum testosterone levels, spermatogenesis and reproductive organ weights.

Taken together, we reported a method for the identification and isolation of human SLCs on the basis of p75 expression, and demonstrated that transplanted human p75+ SLCs could replace disrupted LCs for testosterone production. These findings provide the groundwork for further clinical application of human SLCs for hypogonadism.

Zhang, M., J. Wang, et al. "Transplanted human p75-positive stem Leydig cells replace disrupted Leydig cells for testosterone production." Cell Death Dis 2017;8(10) e3123. Cell Death and Disease - Transplanted human p75-positive stem Leydig cells replace disrupted Leydig cells for testosterone production

That's awesome news for many people. Go science!

 

[Bleeding heart]

I can't understand anything he posts.

 

[Michael Scally MD]

[Mice] Subcutaneous Leydig Stem Cell Autograft: A Promising Strategy to Increase Serum Testosterone

Exogenous testosterone therapy can be used to treat testosterone deficiency; however, it has several adverse effects including infertility due to negative feedback on the hypothalamic-pituitary--gonadal (HPG) axis. Leydig stem cell (LSC) transplantation could provide a new strategy for treating testosterone deficiency, but clinical translatability of injecting stem cells inside the testis is not feasible.

Here, we explore the feasibility of subcutaneously autografting LSCs in combination with Sertoli and myoid cells to increase testosterone. We also studied whether the grafted LSCs can be regulated by the HPG axis and the molecular mechanism behind this regulation.

LSCs were isolated from the testes of 12-week-old C57BL/6 mice, and subcutaneously autografted in combination with Sertoli cells and myoid cells. We found that LSCs alone were incapable of self-renewal and differentiation. However, in combination with Sertoli cells and myoid cells, LSCs underwent self-renewal as well as differentiation into mature Leydig cells. As a result, the recipient mice that received the LSC autograft showed testosterone production with preserved luteinizing hormone.

We found that testosterone production from the autograft was regulated by hedgehog (HH) signaling. Gain of function and loss of function study confirmed that Desert HH (DHH) agonist increased and DHH antagonist decreased testosterone production from autograft. This study is the first to demonstrate that LSCs, when autografted subcutaneously in combination with Sertoli cells and myoid cells, can increase testosterone production. Therefore, LSC autograft may provide a new treatment for testosterone deficiency while simultaneously preserving the HPG axis. Stem Cells Translational Medicine 2018.

Arora H, Zuttion M, Nahar B, Lamb D, Hare JM, Ramasamy R. Subcutaneous Leydig Stem Cell Autograft: A Promising Strategy to Increase Serum Testosterone. Stem cells translational medicine 2018. https://stemcellsjournals.onlinelibrary.wiley.com/doi/full/10.1002/sctm.18-0069

 

[Michael Scally MD]

[OA] [Rat] Differentiation of Human Induced Pluripotent Stem Cells into Leydig-Like Cells with Molecular Compounds

Leydig cells (LCs) play crucial roles in producing testosterone, which is critical in the regulation of male reproduction and development. Low levels of testosterone will lead to male hypogonadism. LC transplantation is a promising alternative therapy for male hypogonadism. However, the source of LCs limits this strategy for clinical applications.

Thus far, others have reported that LCs can be derived from stem cells by gene transfection, but the safe and effective induction method has not yet been reported. Here, we report that Leydig-like cells can be derived from human induced pluripotent stem cells (iPSCs) using a novel differentiation protocol based on molecular compounds.

The iPSCs-derived Leydig-like cells (iPSC-LCs) acquired testosterone synthesis capabilities, had the similar gene expression profiles with LCs, and positively expressed Leydig cell lineage-specific protein markers LHCGR, STAR, SCARB1, SF-1, CYP11A1, HSD3B1, and HSD17B3 as well as negatively expressed iPSC-specific markers NANOG, OCT4, and SOX2.

When iPSC-LCs labeled with lipophilic red dye (PKH26) were transplanted into rat testes that were selectively eliminated endogenous LCs using EDS (75 mg/kg), the transplanted iPSC-LCs could survive and function in the interstitium of testes, and accelerate the recovery of serum testosterone levels and testis weights.

Collectively, these findings demonstrated that the iPSCs were able to be differentiated into Leydig-like cells by few defined molecular compounds, which may lay the safer groundwork for further clinical application of iPSC-LCs for hypogonadism.

Chen X, Li C, Chen Y, et al. Differentiation of human induced pluripotent stem cells into Leydig-like cells with molecular compounds. Cell Death & Disease 2019;10:220. https://doi.org/10.1038/s41419-019-1461-0

 

[Michael Scally MD]

Directing Differentiation of Human Induced Pluripotent Stem Cells Toward Androgen-Producing Leydig Cells Rather Than Adrenal Cells

Our results suggest that both androgen- and cortisol-producing human Leydig and adrenal cells can be induced from human induced pluripotent stem cells.

This bidirectional approach offers insights into the events specifying different steroidogenic cell populations sharing developmental origins.

More importantly, our study provides a way to generate possible transplantation materials for clinical therapies.

Human Leydig-like cells could also be useful for in vitro studies of testicular development and pathologies of testis-relevant diseases, and for the discovery of new drugs inducing androgen formation for hypogonadism treatment.

Lu Li el al., "Directing differentiation of human induced pluripotent stem cells toward androgen-producing Leydig cells rather than adrenal cells," PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1908207116

Reduced serum testosterone (T), or hypogonadism, affects millions of men and is associated with many pathologies, including infertility, cardiovascular diseases, metabolic syndrome, and decreased libido and sexual function. Administering T-replacement therapy (TRT) reverses many of the symptoms associated with low T levels. However, TRT is linked to side effects such as infertility and increased risk of prostate cancer and cardiovascular diseases.

Thus, there is a need to obtain T-producing cells that could be used to treat hypogonadism via transplantation and reestablishment of T-producing cell lineages in the body. T is synthesized by Leydig cells (LCs), proposed to derive from mesenchymal cells of mesonephric origin. Although mesenchymal cells have been successfully induced into LCs, the limited source and possible trauma to donors hinders their application to clinical therapies. Alternatively, human induced pluripotent stem cells (hiPSCs), which are expandable in culture and have the potential to differentiate into all somatic cell types, have become the emerging source of autologous cell therapies.

We have successfully induced the differentiation of hiPSCs into either human Leydig-like (hLLCs) or adrenal-like cells (hALCs) using chemically defined culture conditions. Factors critical for the development of LCs were added to both culture systems. hLLCs expressed all steroidogenic genes and proteins important for T biosynthesis, synthesized T rather than cortisol, secreted steroid hormones in response to dibutyryl-cAMP and 22(R)-hydroxycholesterol, and displayed ultrastructural features resembling LCs. By contrast, hALCs synthesized cortisol rather than T. The success in generating hiPSC-derived hLLCs with broad human LC (hLC) features supports the potential for hiPSC-based hLC regeneration.

 

[Sworder]

I would be down for some research using axolotl blood

 

[Michael Scally MD]

Directing Differentiation of Human Induced Pluripotent Stem Cells Toward Androgen-Producing Leydig Cells Rather Than Adrenal Cells

Our results suggest that both androgen- and cortisol-producing human Leydig and adrenal cells can be induced from human induced pluripotent stem cells.

This bidirectional approach offers insights into the events specifying different steroidogenic cell populations sharing developmental origins.

More importantly, our study provides a way to generate possible transplantation materials for clinical therapies.

Human Leydig-like cells could also be useful for in vitro studies of testicular development and pathologies of testis-relevant diseases, and for the discovery of new drugs inducing androgen formation for hypogonadism treatment.

Lu Li el al., "Directing differentiation of human induced pluripotent stem cells toward androgen-producing Leydig cells rather than adrenal cells," PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1908207116

Reduced serum testosterone (T), or hypogonadism, affects millions of men and is associated with many pathologies, including infertility, cardiovascular diseases, metabolic syndrome, and decreased libido and sexual function. Administering T-replacement therapy (TRT) reverses many of the symptoms associated with low T levels. However, TRT is linked to side effects such as infertility and increased risk of prostate cancer and cardiovascular diseases.

Thus, there is a need to obtain T-producing cells that could be used to treat hypogonadism via transplantation and reestablishment of T-producing cell lineages in the body. T is synthesized by Leydig cells (LCs), proposed to derive from mesenchymal cells of mesonephric origin. Although mesenchymal cells have been successfully induced into LCs, the limited source and possible trauma to donors hinders their application to clinical therapies. Alternatively, human induced pluripotent stem cells (hiPSCs), which are expandable in culture and have the potential to differentiate into all somatic cell types, have become the emerging source of autologous cell therapies.

We have successfully induced the differentiation of hiPSCs into either human Leydig-like (hLLCs) or adrenal-like cells (hALCs) using chemically defined culture conditions. Factors critical for the development of LCs were added to both culture systems. hLLCs expressed all steroidogenic genes and proteins important for T biosynthesis, synthesized T rather than cortisol, secreted steroid hormones in response to dibutyryl-cAMP and 22(R)-hydroxycholesterol, and displayed ultrastructural features resembling LCs. By contrast, hALCs synthesized cortisol rather than T. The success in generating hiPSC-derived hLLCs with broad human LC (hLC) features supports the potential for hiPSC-based hLC regeneration.

[OA] An approach that someday may boost testosterone biosynthesis in males with late-onset hypogonadism.

The elegant studies of Li et al. provide a bidirectional approach to specify different steroidogenic cell populations that share developmental origins, which in the future may provide a source of human Leydig-like cells to be used for transplantation for the clinical therapy of male hypogonadism. Transplantation of human autologous Leydig-like cells for androgen supplementation in males would revolutionize the treatment of male hypogonadism. Directing differentiation of human induced pluripotent stem cells toward androgen-producing Leydig cells rather than adrenal cells

…

Despite this revolutionary advance, more research is required to translate this work from the “bench to the bedside.” It remains to be demonstrated that these Leydig-like cells can ever fully function as normal human Leydig cells and maintain long-term steroidogenesis.

Importantly, it would be expected that the transplanted cells would be part of a system under the control of the hypothalamic–pituitary–gonadal/“Leydig cell” axis resulting in normal, but not elevated levels of circulating testosterone, yet stimulation of these Leydig-like cells by LH remains to be shown.

In all likelihood, these Leydig-like cells are not fully differentiated adult Leydig cells as the response to cAMP administration and their ultrastructural morphology suggest that further differentiation is required. Nevertheless, it appears that the quest to develop an autologous human Leydig cell for research, clinical, and drug discovery applications is close to completion

Lamb DJ. An approach that someday may boost testosterone biosynthesis in males with late-onset hypogonadism (low testosterone). Proceedings of the National Academy of Sciences of the United States of America 2019. An approach that someday may boost testosterone biosynthesis in males with late-onset hypogonadism (low testosterone)

A look toward the future: Potential applications of human Leydig-like cells derived from human induced pluripotent stem cells.

A. A shows the bidirectional differentiation of human adrenal-like cells that secreted aldosterone and cortisol and human Leydig-like cells secreting testosterone.

B. B depicts the potential rejuvenation of testosterone biosynthesis in males with primary hypogonadism with transplantation of the human Leydig-like cells directly into the interstitial compartment of the testis or at a more readily accessible exogenous site.

C. C shows the use of the Leydig-like cells for studies of testicular development and to help define the etiologies of specific testis-relevant diseases.

D. D highlights the potential use of Leydig-like cells for drug discovery and testing of candidate drugs that enhance androgen biosynthesis.

 

[proken]

Would spot injections work at the site of the injury? Broke my leg (tib/fib) 18 months ago. Bone knitted up quickly but Achilles tendon is only 50%. Can trot but not run. The calf muscle has atrophied. I would spend the money on stem cell therapy if it would speed up the healing process.

 

[Michael Scally MD]

Leydig Cells in the Adult Testis: Characterization, Regulation and Potential Applications

Androgen deficiency (hypogonadism) affects males of all ages. Testosterone replacement therapy (TRT) is effective in restoring serum testosterone and relieving symptoms. TRT, however, is reported to have possible adverse side-effects in part because testosterone is administered, not produced in response to the hypothalamic-pituitary-gonadal (HPG) axis.

Progress in stem cell biology offers potential alternatives for treating hypogonadism. Adult Leydig cells (ALCs) are generated by stem Leydig cells (SLCs) during puberty. SLCs persist in the adult testis. Considerable progress has been made in the identification, isolation, expansion and differentiation of SLCs in vitro.

In addition to forming ALCs, SLCs are multipotent, with the ability to give rise to all three major cell lineages of typical mesenchymal stem cells, including osteoblasts, adipocytes, and chondrocytes. Several regulatory factors, including desert hedgehog and platelet-derived growth factor, have been reported to play key roles in the proliferation and differentiation of SLCs into the Leydig lineage.

In addition, stem cells from several non-steroidogenic sources including embryonic stem cells, induced pluripotent stem cells, mature fibroblasts, and mesenchymal stem cells (MSCs) from bone marrow, adipose tissue, and umbilical cord have been transdifferentiated into Leydig-like cells (LLCs) under a variety of induction protocols. ALCs generated from SLCs in vitro, and LLCs, have been successfully transplanted into ALC-depleted animals, restoring serum testosterone levels under HPG control.

However, important questions remain, including:
· For how long will the transplanted cells continue to function?
· Which induction protocol is safest and most effective?

For translational purposes, more work is needed with primate cells, especially human.

Chen P, Zirkin BR, Chen H. Leydig Cells in the Adult Testis: Characterization, Regulation and Potential Applications. Endocr Rev 2019. https://academic.oup.com/edrv/advance-article/doi/10.1210/endrev/bnz013/5610863

 

[SaneDog]

Very interesting read. Thank you, this interests me.

 

[Michael Scally MD]

[Rats] Leydig-Like Cells Derived from Reprogrammed Human Foreskin Fibroblasts by CRISPR/dCas9 Increase the Level of Serum Testosterone

In the past few years, Leydig cell (LC) transplantation has been regarded as an effective strategy for providing physiological patterns of testosterone in vivo. Recently, we have successfully converted human foreskin fibroblasts (HFFs) into functional Leydig-like cells (iLCs) in vitro by using the CRISPR/dCas9 system, which shows promising potential for seed cells. However, it is not known whether the reprogrammed iLCs can survive or restore serum testosterone levels in vivo.

Therefore, in this study, we evaluate whether reprogrammed iLCs can restore the serum testosterone levels of castrated rats when they are transplanted into the fibrous capsule.

We first developed the castrated Sprague Dawley rat model through bilateral orchiectomy and subsequently injected extracellular matrix gel containing transplanted cells into the fibrous capsule of castrated rats.

Finally, we evaluated dynamic serum levels of testosterone and luteinizing hormone (LH) in castrated rats, the survival of implanted iLCs, and the expression levels of Leydig steroidogenic enzymes by immunofluorescence staining and Western blotting.

Our results demonstrated that implanted iLCs could partially restore the serum testosterone level of castrated rats, weakly mimic the role of adult Leydig cells in the hypothalamic-pituitary-gonadal axis for a short period, and survive and secrete testosterone, through 6 weeks after transplantation. Therefore, this study may be valuable for treating male hypogonadism in the future.

Huang H, Zhong L, Zhou J, et al. Leydig-like cells derived from reprogrammed human foreskin fibroblasts by CRISPR/dCas9 increase the level of serum testosterone in castrated male rats [published online ahead of print, 2020 Mar 11]. J Cell Mol Med. 2020;10.1111/jcmm.15018. doi:10.1111/jcmm.15018 Error - Cookies Turned Off

 

[BirdieNumNum]

Wow.

 

[Michael Scally MD]

Endosialin Defines Human Stem Leydig Cells with Regenerative Potential

Study question: Is endosialin a specific marker of human stem Leydig cells (SLCs) with the ability to differentiate into testosterone-producing Leydig cells (LCs) in vitro and in vivo?

Summary answer: Endosialin is a specific marker of human SLCs which differentiate into testosterone-producing LCs in vitro and in vivo.

What is known already: Human SLCs have been identified and isolated using the marker platelet-derived growth factor receptor α (PDGFRα) or nerve growth factor receptor (NGFR). However, the specificity was not high; thus, LCs and germ cells could be mistakenly sorted as SLCs if PDGFRα or NGFR was used as a marker for human SLCs isolation.

Study design, size, duration: Firstly, we re-evaluated the specificity of PDGFRα and NGFR for SLCs in adult human testes. Then we analysed the previously published single-cell sequencing data and found that endosialin may identify human SLCs. Subsequently, we sorted endosialin+ cells from four human donors and characterized their self-renewal and multipotent properties.

To assess whether endosialin+ cells have the potential to differentiate into functional LCs in vitro, these cells were stimulated by differentiation-inducing medium. We next assessed the in vivo regenerative potential of human endosialin+ cells after xenotransplantation into the testes of immunodeficient mice.

Participants/materials, setting, methods: Single-cell sequencing analysis, immunofluorescence and flow cytometry were used to characterize human testis tissues. In vitro colony formation, multipotent differentiation (adipogenic, osteogenic and chondrogenic) and Leydig cell-lineage induction were used to assess stem cell activity.

Xenotransplantation into 3-week-old immunodeficient mice was used to determine in vivo regenerative potential. Endpoint measures included testosterone measurements, cell proliferation, immunofluorescence, flow cytometry and quantitative RT-PCR.

Main results and the role of chance: The results indicate that endosialin is a specific marker of SLCs compared with PDGFRα and NGFR. Additionally, endosialin+ cells isolated from human testes show extensive proliferation and differentiation potential in vitro: their self-renewal ability was inferred by the formation of spherical clones derived from a single cell. Moreover, these cells could differentiate into functional LCs that secreted testosterone in response to LH in a concentration-dependent manner in vitro.

These self-renewal and differentiation properties reinforce the proposal that human testicular endosialin+ cells are SLCs. Furthermore, transplanted human endosialin+ cells appear to colonize the murine host testes, localize to peritubular and perivascular regions, proliferate measurably and differentiate partially into testosterone-producing LCs in vivo.

Large scale data: NA.

Limitations, reasons for caution: Owing to the difficulty in collecting human testis tissue, the sample size was limited. The functions of endosialin on SLCs need to be elucidated in future studies.

Wider implications of the findings: A discriminatory marker, endosialin, for human SLCs purification is a prerequisite to advance research in SLCs and logically promote further clinical translation of SLCs-based therapies for male hypogonadism.

Xia K, Ma Y, Feng X, et al. Endosialin defines human stem Leydig cells with regenerative potential [published online ahead of print, 2020 Sep 20]. Hum Reprod. 2020;deaa174. doi:10.1093/humrep/deaa174 Endosialin defines human stem Leydig cells with regenerative potential

 

[Michael Scally MD]

Insights into the Regulation on Proliferation and Differentiation of Stem Leydig Cells

Male hypogonadism is a clinical syndrome caused by testosterone deficiency. Hypogonadism can be caused by testicular disease (primary hypogonadism) or hypothalamic-pituitary dysfunction (secondary hypogonadism). The present strategy for treating hypogonadism is the administration of exogenous testosterone. But exogenous testosterone is reported to have negative side effects including adverse cardiovascular events and disruption of physiological spermatogenesis probably due to its inability to mimic the physiological circadian rhythm of testosterone secretion in vivo.

In recent years, a growing number of articles demonstrated that stem Leydig cells (SLCs) can not only differentiate into functional Leydig cells (LCs) in vivo to replace chemically disrupted LCs, but also secrete testosterone in a physiological pattern. The proliferation and differentiation of SLCs are regulated by various factors. However, the mechanisms involved in regulating the development of SLCs remain to be summarized.

Factors involved in the regulation of SLCs can be divided into

environmental pollutants,
growth factors,
cytokine and
hormones.

Environmental pollutants such as Perfluorooctanoic acid (PFOA) and Triphenyltin (TPT) could suppress SLCs proliferation or differentiation. Growth factors including FGF1, FGF16, NGF and activin A are essential for the maintenance of SLCs self-renewal and differentiation. Interleukin 6 family could inhibit differentiation of SLCs. Among hormones, dexamethasone suppresses SLCs differentiation, while aldosterone suppresses their proliferation.

The present review focuses on new progress about factors regulating SLC's proliferation and differentiation which will undoubtedly deepen our insights into SLCs and help make better clinical use of them. Different factors affect on the proliferation and differentiation of stem Leydig cells.

Firstly, each rat was intraperitoneally injected EDS so as to deplete Leydig cells from the adult testis. Secondly, the CD51+ or CD90+ cells from the testis of rats are SLCs, and the p75+ cells from human adult testes are human SLCs. These SLCs in the testis start to proliferate and some of them differentiate into LCs. Thirdly, during the SLCs regeneration period, researchers could explore different function of those factors (pollutants, growth factors, cytokines and hormones) towards SLCs.

Liu ZJ, Liu YH, Huang SY, Zang ZJ. Insights into the Regulation on Proliferation and Differentiation of Stem Leydig Cells. Stem Cell Rev Rep. 2021 Feb 17. doi: 10.1007/s12015-021-10133-x. Epub ahead of print. PMID: 33598893. Insights into the Regulation on Proliferation and Differentiation of Stem Leydig Cells