Thy-1+ cells isolated from adult human testicular tissues express human embryonic stem cell genes OCT3/4 and NANOG and may include spermatogonial stem cells

SDF-1/CXCR4 axis maintains porcine prospermatogonia undifferentiated state through regulation of transcription suppressor PLZF

Prospermatogonia (ProSGs), the progenitors of spermatogonial stem cells in neonatal testes, undergo critical migration to the testicular microenvironment-a fundamental process for testicular development and subsequent spermatogenic capacity. The SDF-1/CXCR4 chemokine axis serves as an essential molecular guidance mechanism, directing ProSGs toward the basal membrane of seminiferous tubules. Nevertheless, the precise molecular mechanisms governing this axis remain incompletely understood. Utilizing a porcine in vitro model system, this investigation elucidated the molecular mechanisms underlying the SDF-1/CXCR4 axis in ProSGs fate determination. Through integrated molecular and transcriptomic analyses, we investigated the consequences of CXCR4 inhibition on ProSG cellular dynamics. Our findings demonstrated that the SDF-1/CXCR4 axis exerts regulatory control over ProSGs differentiation via the PI3K-AKT-AP-1 signaling cascade. This regulation significantly influences the transcriptional landscape of ProSGs, particularly modulating the expression of PLZF, a crucial suppressor of spermatogonial differentiation, and DMRT1, an essential mediator of germ cell differentiation. These findings elucidate the molecular mechanisms orchestrating ProSGs homing and emphasize the significance of maintaining male reproductive competence. Furthermore, this research could enhance our understanding of ProSGs biology and its relationship to boar fertility, while potentially facilitating the development of innovative reproductive technologies and sustainable livestock management strategies.

Development, Characterization, and Pluripotency Analysis of Buffalo (Bubalus bubalis) Embryonic Stem Cell Lines Derived from In Vitro-Fertilized, Hand-Guided Cloned, and Parthenogenetic Embryos

We present the derivation, characterization, and pluripotency analysis of three buffalo embryonic stem cell (buESC) lines, from in vitro-fertilized, somatic cell nuclear-transferred, and parthenogenetic blastocysts. These cell lines were developed for later differentiation into germ lineage cells and elucidation of the signaling pathways involved. The cell lines were established from inner cell masses (ICMs) that were isolated manually from the in vitro-produced blastocysts. Most of the ICMs (45-55%) resulted in formation of primary colonies that were subcultured after 8-10 days, leading subsequently to the formation of three buESC lines, one from each blastocyst type. All the cell lines expressed stem cell markers, such as Alkaline Phosphatase, OCT4, NANOG, SSEA1, SSEA4, TRA-1-60, TRA-1-81, SOX2, REX1, CD-90, STAT3, and TELOMERASE. They differentiated into all three germ layers as determined by ectodermal, mesodermal, and endodermal RNA and protein markers. All of the cell lines showed equal expression of pluripotency markers as well as equivalent differentiation potential into all the three germ layers. The static suspension culture-derived embryoid bodies (EBs) showed greater expression of all the three germ layer markers as compared to hanging drop culture-derived EBs. When analyzed for germ layer marker expression, EBs derived from 15% fetal bovine serum (FBS)-based spontaneous differentiation medium showed greater differentiation across all the three germ layers as compared to those derived from Knock-Out Serum Replacement (KoSR)-based differentiation medium.

THY1 as a reliable marker for enrichment of undifferentiated spermatogonia in the goat

Spermatogonial stem cells are unique cells of testes that can restore fertility upon transplantation into recipient testes. However, use of suitable markers for enrichment of these cells have important potential application. THY1, is an established conserved marker of spermatogonial stem cells in bovine, rodents, and primates, but there is no information available in goats. After three rounds of enzymatic digestion of prepubertal goat testicular tissues, undifferentiated spermatogonia positive for THY1 were isolated by magnetic-activated cell sorting and were used for immunocytochemistry, real-time polymerase chain reaction analysis for gene expression, protein expression, and transplantation into recipient mice. Immunocytochemical analyses showed that significantly higher percentage of THY1(+) cells were positive for PLZF and VASA when compared with unselected population. This result for PLZF was further confirmed at the protein level. Real-time polymerase chain reaction analysis revealed that expression of THY1, PLZF, VASA, BCL6B, and UCHL1 as SCCs characteristic genes in THY1(+) cells was significantly higher than in the initial population. Finally, transplantation of PKH26-labeled cells revealed that THY1(+) cells had higher capacity for colony formation when compared with unselected cells. In conclusion, the results provide indications that THY1 surface marker can be reliably used for enrichment of undifferentiated spermatogonial in the goats.

Establishment and in vitro culture of porcine spermatogonial germ cells in low temperature culture conditions

The objective of this study was to establish a porcine spermatogonial germ cell (pSGC) line and develop an in vitro culture system. Isolated total testicular cells (TTCs) from 5-day-old porcine testes were primary cultured at 31, 34, and 37°C. Although the time of colony appearance was delayed at 31°C, strong alkaline phosphatase staining, expressions of pluripotency marker genes such as OCT4, NANOG, and THY1, and the gene expressions of the undifferentiated germ cell markers PLZF and protein gene product 9.5 (PGP9.5) were identified compared to 34 and 37°C. Cell cycle analysis for both pSGC and feeder cells at the three temperatures revealed that more pSGCs were in the G2/M phase at 31°C than 37°C at the subculture stage. In vitro, pSGCs could stably maintain undifferentiated germ cell and stem cell characteristics for over 60days during culture at 31°C. Xenotransplantation of pSGCs to immune deficient mice demonstrated a successful colonization and localization on the seminiferous tubule basement membrane in the recipient testes. In conclusion, pSGCs from neonatal porcine were successfully established and cultured for long periods under a low temperature culture environment in vitro.

Stem cell research for male infertility

Stem cells have the ability both to differentiate into numerous tissues and to self-renew. Because of these unique properties, stem cells are promising candidates for use in regenerative medicine. Among stem cell types, embryonic stem (ES) cells have been the most studied; however, alternatives such as induced pluripotent stem cells or other adult stem cells are now being established. In this review, we focus on stem cell research that may have applications in treating male infertility. Stem cells with ES-like properties have been generated from adult human testis tissue. We expect that breakthroughs in stem cell research will increase our understanding of male infertility and lead to treatments in the near future.

Reprogramming of adult human testicular cells by four transcription factors (OCT4, SOX2, KLF4, and C-MYC)

Purpose

Induced pluripotent stem (iPS) cells have been generated from mouse and human fibroblasts by several groups; however, transplanted mouse iPS cells can cause teratomas, depending on their tissue of origin. Therefore, human iPS cells are preferable, and various tissues are being evaluated for their potential to generate human iPS cells.

Methods

We examined whether adult human testicular tissue had undergone reprogramming by introducing four transcription factors, OCT4, SOX2, KLF4, and C-MYC, using lentiviral vectors.

Results

We obtained embryonic stem (ES)-like cells derived from human testicular tissue by introducing four cDNAs, encoding the transcription factors OCT4, SOX2, KLF4, and C-MYC, using lentiviral vectors. We showed that DAZL and VASA were expressed in testicular cells but down-regulated in ES-like cells, indicating that the cells had undergone reprogramming. ES-like cells could develop tumors, which is a hallmark of pluripotency, when SCID mice were injected with these cells.

Conclusions

We induced iPS cells from adult human testicular tissue by introducing four transcription factors, OCT4, SOX2, KLF4, and C-MYC, using lentiviral vectors. Future studies on these cells may elucidate the causes of male infertility, and eventually lead to treatments with autologous testicular tissue-derived iPS cells.

Newer insights into premeiotic development of germ cells in adult human testis using Oct-4 as a stem cell marker

The transcription factor octamer-binding transforming factor 4 (Oct-4) is central to the gene regulatory network responsible for self-renewal, pluripotency, and lineage commitment in embryonic stem (ES) cells and induced pluripotent stem cells (PSCs). This study was undertaken to evaluate differential localization and expression of two major transcripts of Oct-4, viz. Oct-4A and Oct-4B, in adult human testis. A novel population of 5- to 10-μm PSCs with nuclear Oct-4A was identified by ISH and immunolocalization studies. Besides Oct-4, other pluripotent markers like Nanog and TERT were also detected by RT-PCR. A(dark) spermatogonial stem cells (SSCs) were visualized in pairs and chains undergoing clonal expansion and stained positive for cytoplasmic Oct-4B. Quantitative PCR and Western blotting revealed both the transcripts, with higher expression of Oct-4B. It is proposed that PSCs undergo asymmetric cell division and give rise to A(dark) SSCs, which proliferate and initiate lineage-specific differentiation. The darkly stained nuclei in A(dark) SSCs may represent extensive nuclear reprogramming by epigenetic changes when a PSC becomes committed. Oct-4B eventually disappeared in mature germ cells, viz. spermatocytes, spermatids, and sperm. Besides maintaining normal testicular homeostasis, PSCs may also be implicated in germ cell tumors and ES-like colonies that have recently been derived from adult human testicular tissue.