Sertoli cell

Sertoli cells arise from the sex-determining region Y (SRY) gene expression in the genital ridge and are analogous to granulosa cells in females (both derived from primitive gonadal cells). They line the seminiferous tubules and perform several key functions: (1) Form tight junctions between adjacent Sertoli cells creating the blood-testis barrier, which protects developing germ cells from autoimmune attack by isolating haploid antigens from the immune system; (2) Support and nourish developing spermatogonia/spermatocytes/spermatids via paracrine signaling; (3) Secrete androgen-binding protein (ABP) to maintain high local testosterone concentration needed for spermatogenesis; (4) Produce inhibin B, which exerts negative feedback on FSH secretion from the anterior pituitary; (5) Secrete Anti-Müllerian Hormone (AMH/Müllerian Inhibiting Factor) during embryogenesis, causing regression of the Müllerian ducts in males; (6) Mediate the actions of FSH and testosterone on spermatogenesis (Sertoli cells have FSH and androgen receptors, while Leydig cells have LH receptors for testosterone production). Clinically, Sertoli cells are relevant in: Klinefelter syndrome (dysfunctional Sertoli cells leading to low inhibin, elevated FSH, small firm testes); Sertoli cell-only syndrome (germ cell aplasia causing infertility with normal virilization); Sertoli-Leydig cell tumors (rare sex cord-stromal tumors, may cause virilization); and as a target of environmental toxins/heat affecting fertility. The HPG axis regulation: GnRH stimulates LH and FSH; FSH acts on Sertoli cells to support spermatogenesis and stimulate inhibin B secretion; inhibin B negatively feeds back on FSH release specifically (not LH), which is a key USMLE testing point distinguishing Sertoli cell (FSH-inhibin axis) from Leydig cell (LH-testosterone axis) physiology.