Human Germline Stem Cells Research Articles

Mechanisms of Germline Stem Cell Competition across Species.

In this review, we introduce the concept of cell competition, which occurs between heterogeneous neighboring cell populations. Cells with higher relative fitness become "winners" that outcompete cells of lower relative fitness ("losers"). We discuss the idea of super-competitors, mutant cells that expand at the expense of wild-type cells. Work on adult stem cells (ASCs) has revealed principles of neutral competition, wherein ASCs can be stochastically lost and replaced, and of biased competition, in which a winning ASC with a competitive advantage replaces its neighbors. Germline stem cells (GSCs) are ASCs that are uniquely endowed with the ability to produce gametes and, therefore, impact the next generation. Mechanisms of GSC competition have been elucidated by studies in Drosophila gonads, tunicates, and the mammalian testis. Competition between ASCs is thought to underlie various forms of cancer, including spermatocytic tumors in the human testis. Paternal age effect (PAE) disorders are caused by de novo mutations in human GSCs that increase their competitive ability and make them more likely to be inherited, leading to skeletal and craniofacial abnormalities in offspring. Given its widespread effects on human health, it is important to study GSC competition to elucidate how cells can become winners or losers.

O-189 Male fertility restoration by direct transplantation of human infant testicular cells into infertile recipient mouse testis

Abstract Study question Is colonization of human gonocytes and spermatogonial stem cells (SSCs) directly transplanted to seminiferous tubules of busulfan sterilised mice testis during an 8-week period feasible? Summary answer Gonocytes and SSCs from infant boys can settle on the basal membrane and form germline stem cell colonies in the seminiferous tubules of recipient mice. What is known already The neonatal or immature animal provides higher populations of gonocytes and/or SSCs than adults, and the number of transplanted donor SSCs directly affects the colonization rate of the recipient testes. Along with SSC transplantation restoring the recipient’s spermatogenesis, donor gonocyte was also reported to be capable of establishing spermatogenesis in rodents. Study design, size, duration Transplantation of human testicular cells including gonocytes and SSCs into seminiferous tubules of infertile recipient mice. We included 10 infant testis biopsies from which single-cell suspension was transplanted individually into the seminiferous tubules of 10 immunodeficient mice. The immunodeficient mouse testes were injected with busulfan to deplete germ cells. Four weeks later, we did the xenotransplantation. Then after eight weeks, we collected all mouse testes to do further analysis. Participants/materials, setting, methods Testis biopsies were obtained from cryptorchid boys undergoing orchidopexy. After enzymatic digestion of the testis biopsies, dissociated single-cell suspensions were pre-labeled with a green fluorescent dye. Then the single-cell suspensions were transplanted into seminiferous tubules of the infertile recipient mice. Eight weeks later, the presence of gonocytes and SSCs was determined by immunohistochemistry and whole-mount immunofluorescence. Main results and the role of chance Without in vitro propagation, naturally enriched human germline stem cells settled on the basal membrane of seminiferous tubules and survived in the mouse testes at least for two months demonstrating that human gonocytes and SSCs were capable of colonizing the recipient mouse seminiferous tubules. Limitations, reasons for caution The study samples were from infant boys with undescended testes that were more likely to contain gonocytes. It was not possible to determine which germ-cell type at transplantation resulted in the detected gonocytes and SSC colonies after xenotransplantation. Transplantation of gonocytes may include the potential risk of stem cell-related malignancy. Wider implications of the findings Without in vitro propagation, male germline stem cell-based transplantation could provide a relatively safe therapeutic treatment for prepubertal boys with cryptorchidism and boys diagnosed with cancer. This method could also facilitate clinical translation. Trial registration number not applicable

Efficient generation of functional haploid spermatids from human germline stem cells by three-dimensional-induced system

Generation of functional spermatids from human spermatogonial stem cells (SSCs) in vitro is of utmost importance for uncovering mechanisms underlying human germ cell development and treating infertility. Here we report a three-dimensional-induced (3D-I) system by which human SSCs were efficiently differentiated into functional haploid spermatids. Human SSCs were isolated and identified phenotypically. Meiotic chromatin spreads and DNA content assays revealed that spermatocytes and haploid cells were effectively generated from human SSCs by 3D-I system. Haploid cells derived from human SSCs harbored normal chromosomes and excluded Y chromosome microdeletions. RNA sequencing and bisulfite sequencing analyses reflected similarities in global gene profiles and DNA methylation in human SSCs-derived spermatids and normal round spermatids. Significantly, haploid spermatids generated from human SSCs via 3D-I system were capable of fertilizing mouse oocytes, which subsequently enabled the development of hybrid embryos. This study thus provides invaluable human male gametes for treating male infertility.

Detection and characterization of female germline stem cells in menopausal/perimenopausal women and related clinical analysis

To investigate the existence of human germline stem cells in menopausal/perimenopausal women, and to explore the relating characteristics of patients and specimen that may predict the success of subsequent cell culture.

Ovarian germline stem cells

It has long been established that germline stem cells (GSCs) are responsible for lifelong gametogenesis in males, and some female invertebrates (for example, Drosophila) and lower vertebrates (for example, teleost fish and some prosimians) also appear to rely on GSCs to replenish their oocyte reserve in adulthood. However, the presence of such cells in the majority of female mammals is controversial, and the idea of a fixed ovarian reserve determined at birth is the prevailing belief among reproductive biologists. However, accumulating evidence demonstrates the isolation and culture of putative GSCs from the ovaries of adult mice and humans. Live offspring have been reportedly produced from the culture of adult mouse GSCs, and human GSCs formed primordial follicles using a mouse xenograft model. If GSCs were present in adult female ovaries, it could be postulated that the occurrence of menopause is not due to the exhaustion of a fixed supply of oocytes but instead is a result of GSC and somatic cell aging. Alternatively, they may be benign under normal physiological conditions. If their existence were confirmed, female GSCs could have many potential applications in both basic science and clinical therapies. GSCs not only may provide a valuable model for germ cell development and maturation but may have a role in the field of fertility preservation, with women potentially being able to store GSCs or GSC-derived oocytes from their own ovaries prior to infertility-inducing treatments. Essential future work in this field will include further independent corroboration of the existence of GSCs in female mammals and the demonstration of the production of mature competent oocytes from GSCs cultured entirely in vitro.

Repowering the ovary

Massachusetts General Hospital and Harvard Medical School researchers have devised a way to generate viable oocytes from human germline stem cells. The findings have been licensed by OvaScience, which plans to use the oocyte precursor cells to develop several platforms for restoring fertility in vitro and in vivo.

"Waste" Follicular Aspirate from Fertility Treatment–A Potential Source of Human Germline Stem Cells?

Fertility clinics worldwide routinely produce a large volume of 'waste' follicular aspirate, which is potentially an abundant source of immature ovarian follicles. Current attempts to cultivate these further in vitro to yield viable mature oocytes for fertility treatment have not yet achieved much success. Instead, recent lines of evidence have emerged that are suggestive of a potential stem cell niche within such immature ovarian follicles. The recent discovery of follicular renewal and putative germ-line stem cells within the postnatal mammalian ovary shook the foundations of reproductive biology by challenging the established dogma that mammalian females lose the capacity for germ cell renewal during fetal life, such that a fixed reserve of germ cells (oocytes) enclosed within follicles is endowed at birth. More intriguingly, another recent study in the Drosophila model provided compelling evidence that somatic progenies (nurse cells) of germ-line stem cells had the ability to revert back to the stem-cell-like state. This introduces the exciting possibility that within the mammalian ovarian follicle, similar somatic progenies of germ-line stem cells may also possess a greater intrinsic ability to revert back into functional stem cells. If this is the case, then a favored candidate would be the cumulus/granulosa of immature ovarian follicles, since such cells are true homologues of nurse cells found within the Drosophila ovary. The successful elucidation of a human germ-line stem cell niche within immature ovarian follicles is likely to have huge ramifications in stem cell biology and regenerative medicine.