Spermatogonial stem cell-based cellular therapy for non-obstructive azoospermia: a narrative review

Spermatogonial stem cells (SSCs) constitute the foundation of male sperm production and fertility. SSCs are characterised by their capacity for self-renewal and differentiation into spermatozoa throughout a male's reproductive life, thereby transmitting genetic information to subsequent generations. During embryonic development, SSCs are derived from postnatal testicular gonocytes, which originate from long-lived primordial germ cells. A large proportion of men's infertility is detected by sperm analysis. Unusual sperm parameters include sperm concentration, morphology and motility. Male infertility is mainly due to hormone deficits, physical causes, sexually transmitted diseases, environment, lifestyle and hereditary factors. The most severe form of male infertility is non-obstructive azoospermia (NOA), which is defined as no sperm in the ejaculate because of spermatogenesis failure. The first-line treatment for these individuals has been testicular sperm extraction under an operating microscope (micro-TESE). SSCs are also considered a promising pathway for regenerating impaired or damaged spermatogenesis. This review addresses SSC transplantation as a potential method for treating male infertility and restoring spermatogenesis in patients with degenerative diseases such as cancer, radiotherapy and chemotherapy.