Effectiveness of stem cell therapy for male infertility restoration: A systematic review

Cell therapy has emerged as a prominent leader in regenerative medicine, offering potential solutions for various disorders, including infertility. Half of all infertility cases are related to male factors. The objective of this study is to systematically summarize the existing knowledge regarding studies on stem cell-based therapy for the regeneration of impaired spermatogenesis. Initial searching was performed through main databases (e.g., PubMed, Scopus, Cochrane Library, and Embase) until December 2023. Articles conducted on stem cell transplantation into the testis of infertile models were considered. The titles and abstracts of articles were carefully evaluated and screened by independent authors. Nonrelated articles were deleted. The desired outcomes of infertility treatment after stem cell transplantation were attentively evaluated in the final selected articles. In the primary search, 3237 published studies were identified. Finally, 39 studies were included based on the eligibility criteria. In all studies except for two articles, all the outcomes considered, including germ cells/spermatogonia stem cell differentiation, spermatogenesis restoration, defective testicular tissue regeneration, improved sperm quality parameters, and hormonal levels, as well as increased expression of fertility-related markers and fertility rate, were observed after stem cell transplantation. Transplantation of stem cells, especially MSCs could be a safe and effective method for the treatment of male infertility patients, such as azoospermic cases. Further research to investigate the efficiency of different stem cell sources, providing nutrient conditions for the isolation and differentiation of stem cells, and exploring the paracrine effects of MSCs in male infertility therapy, could be useful.