Proliferative Activity In Vitro and DNA Repair Indicate that Adult Mouse and Human Sertoli Cells Are Not Terminally Differentiated, Quiescent Cells

Sertoli cells isolated from the adult mouse and human testis resume proliferation in culture. After 20 days of culture in Dulbecco modified Eagle medium/Ham F12 (DMEM/F12) medium containing 5% fetal calf serum, about 36% of the mouse Sertoli cells, identified by their immunohistochemical staining for the Sertoli cell marker vimentin, incorporated bromodeoxyuridine (BrdU). The renewed proliferation was associated with a 70% decrease in expression of the cell cycle inhibitor CDKN1B (P27(kip1)) and a 2-fold increase in the levels of the proliferation inducer ID2. In vivo, the balance between cell cycle inhibitors and inducers probably is such that the cells remain quiescent, whereas in culture the balance is disturbed such that Sertoli cells start to proliferate again. The renewed proliferative activity of Sertoli cells in culture was further confirmed by double staining for BrdU and the Sertoli cell marker clusterin (CLU), showing about 25% of the CLU-positive Sertoli cells to be also positive for BrdU after 13 days of culture. Radiobiologically, Sertoli cells are also different from other quiescent somatic cells in the testis because they express several DNA repair proteins (XRCC1, PARP1, and others). Indeed, a comet assay on irradiated Sertoli cells revealed a 70% reduction in tail length and tail moment at 20 h after irradiation. Hence, Sertoli cells repair DNA damage, whereas other quiescent somatic testicular cells do not. This repair may be accomplished by nonhomologous end joining via XRCC1 and PARP1. In conclusion, cell kinetic and radiobiological data indicate that Sertoli cells more resemble arrested proliferating cells than the classic postmitotic and terminally differentiated somatic cells that they have always been assumed to b

Spermatogonial Stem Cell Niche and Spermatogonial Stem Cell Transplantation in Zebrafish

Background Spermatogonial stem cells (SSCs) are the foundation of spermatogenesis, and reside within a specific microenvironment in the testes called “niche” which regulates stem cell properties, such as, self-renewal, pluripotency, quiescence and their ability to differentiate. Methodology/Principal Findings Here, we introduce zebrafish as a new model for the study of SSCs in vertebrates. Using 5′-bromo-2′-deoxyuridine (BrdU), we identified long term BrdU-retaining germ cells, type A undifferentiated spermatogonia as putative stem cells in zebrafish testes. Similar to rodents, these cells were preferentially located near the interstitium, suggesting that the SSC niche is related to interstitial elements and might be conserved across vertebrates. This localization was also confirmed by analyzing the topographical distribution of type A undifferentiated spermatogonia in normal, vasa::egfp and fli::egfp zebrafish testes. In the latter one, the topographical arrangement suggested that the vasculature is important for the SSC niche, perhaps as a supplier of nutrients, oxygen and/or signaling molecules. We also developed an SSC transplantation technique for both male and female recipients as an assay to evaluate the presence, biological activity, and plasticity of the SSC candidates in zebrafish. Conclusions/Significance We demonstrated donor-derived spermato- and oogenesis in male and female recipients, respectively, indicating the stemness of type A undifferentiated spermatogonia and their plasticity when placed into an environment different from their original niche. Similar to other vertebrates, the transplantation efficiency was low. This might be attributed to the testicular microenvironment created after busulfan depletion in the recipients, which may have caused an imbalance between factors regulating self-renewal or differentiation of the transplanted SSCs

Stem Cells, Self-Renewal, and Lineage Commitment in the Endocrine System

The endocrine system coordinates a wide array of body functions mainly through secretion of hormones and their actions on target tissues. Over the last decades, a collective effort between developmental biologists, geneticists, and stem cell biologists has generated a wealth of knowledge related to the contribution of stem/progenitor cells to both organogenesis and self-renewal of endocrine organs. This review provides an up-to-date and comprehensive overview of the role of tissue stem cells in the development and self-renewal of endocrine organs. Pathways governing crucial steps in both development and stemness maintenance, and that are known to be frequently altered in a wide array of endocrine disorders, including cancer, are also described. Crucially, this plethora of information is being channeled into the development of potential new cell-based treatment modalities for endocrine-related illnesses, some of which have made it through clinical trials

Spermatogonial stem cell autotransplantation. Towards clinical application’

In the last three decades, due to progression in diagnosis and treatment of several types of cancer, survival rate in cancer patients increased tremendously. However, long-term adverse effects of cancer treatments influence negatively quality of life in these cancer survivors. One of the most important side-effects is sterility because of gonadotoxic effect of cancer treatment on testis and ovary. In the twenty-first century, fertility preservation has become a very prominent area of interest in reproductive medicine and oncology. This book - in 7 chapters - not only review the last 35 years of literature about gonadotoxic effects of cancer treatments on semen quality and the effectiveness of current techniques to restore fertility in male cancer survivors, but also reports the results of our last 5 years of researches towards the clinical application of a novel procedure to restore fertility in male cancer survivors, i.e. spermatogonial stem cell autotransplantation