Temporal dynamics of Sertoli and germ cell development in human foetal and prepubertal testis

Correct development of the testis serves as a springboard for male fertility in adult life, yet our understanding of the timing of human Sertoli and germ cell maturation and their dynamics is incomplete. To map the developmental timeline of germ cells and Sertoli cells, we analysed an extensive set of human foetal and prepubertal testicular samples [n=48, spanning from 7 post conception weeks (PCW) to 13.5 years of age]. Octamer binding transcription factor (OCT)3/4+ gonocytes were identified as the main source of proliferative germ cells during foetal development, while melanoma associated antigen (MAGE)-A4+ (pre)spermatogonia divided at a slow rate both in utero and during childhood. In samples aged between 4 and 10 years, anti-Müllerian hormone (AMH) expression is reduced and androgen receptor (AR) expression is increased, consistent with maturation of testicular Sertoli cells. Sertoli cell proliferation peaked at 2-2.5 years and gradually declined through early childhood, becoming minimal from the age of 6, coinciding with lumen formation. These data suggest that Sertoli cell maturation precedes the initiation of spermatogenesis well before the start of puberty. Ultimately, this human testicular developmental timeline serves as a reference for the development of in vitro gametogenesis models and paves the way for fertility preservation and restoration for those at risk of infertility.