Male infertility is defined as the inability of a male to impregnate a fertile female. Male infertility is typically characterized by altered sperm motility, concentration, and morphology, as observed in samples collected at one- to four-week intervals.
Furthermore, it may involve abnormal sperm volume and accessory gonadal function. Male infertility may result from congenital or acquired conditions, including genetic abnormalities, hormonal disorders, immune disorders, reproductive tract injury, testicular failure, systemic diseases, cancer, varicocele, lifestyle changes, and exposure to gonadotoxic agents. However, in some cases, the cause remains unknown. Among infertile males, 15-20% exhibit azoospermia, while 10% have a sperm count of less than 1 million/ml of semen. Much effort has been focused on treating non-obstructive azoospermia, as it is the most challenging and treatable cause of male infertility.
Common medical treatments for male infertility include surgical interventions, hormone therapy, and drug therapy. However, due to their limited therapeutic effect, research into new treatment strategies is needed. Currently, significant progress has been made in assisted reproductive technologies (ARTs) for treating male infertility. Semen freezing combined with intracytoplasmic sperm injection (ICSI) is the only technique used to preserve fertility. However, its low success rate, coupled with infertility due to the absence of functional gametes, remains a challenge for current ARTs. Following the discovery of stem cells, scientists have proposed the use of stem cells and their derived follicles as a new therapeutic approach for treating male infertility.
Recently, it has been reported that stem cells and their derived follicles protect and restore sperm fertility during freeze-thaw procedures. The identification and isolation of spermatogenic stem cells (SSCs) has led to the possibility of generating gametes. Furthermore, the production of stem cells from bone marrow stem cells and Ad-MSCs in vitro and in vivo can significantly facilitate fertility restoration in males. Therefore, stem cell transplantation into infertile males with normal genetic backgrounds may be considered a promising approach to restoring fertility.
