What are the functions of sustentocytes (Sertoli cells) in spermatogenesis?

Sustentocytes (Sertoli cells) act as nurse cells that support and regulate spermatogenesis. They nourish spermatogenic cells, remove their debris, and move them toward the tubule lumen. They also form the blood-testis barrier via tight junctions, secrete testicular fluid, phagocytize faulty cells and excess cytoplasm, and produce chemical mediators such as inhibin and androgen-binding protein.

In spermatogenesis, sustentocytes or Sertoli cells perform multiple supporting roles. They are nonreplicating cells that extend from the basal lamina to the lumen and surround the developing spermatogenic cells. As nurse cells, they nourish the spermatogenic cells, remove their debris, and transport them through the tubular wall toward the lumen. Their tight junctions create two compartments and form the blood-testis barrier, which prevents membrane antigens of differentiating sperm from entering the bloodstream and activating an immune response. The tight junctions also open to allow type B daughter cells to pass into the adluminal compartment while protecting developing sperm. In the adluminal compartment, sustentocytes provide nutrients and essential signals to dividing cells, even regulating whether these cells live or die. They secrete testicular fluid that serves as the transport medium for sperm, and they phagocytize faulty spermatogenic cells and excess cytoplasm shed during spermiogenesis. Additionally, they produce chemical mediators, including inhibin and androgen-binding protein, which help regulate spermatogenesis. Androgen-binding protein keeps testosterone concentration high near spermatogenic cells, while inhibin helps control FSH and GnRH release based on sperm counts.