A Sertoli cell is a highly specialized cell found in the testes. It plays an important role in the development and maturation of sperm cells, or spermatozoa, within the testes, a process called spermatogenesis. Because a Sertoli cell functions largely to assist the developing sperm cells through their maturation process, it sometimes is referred to as a nurse cell. In addition to secreting numerous important hormones and other substances to trigger proper development, a Sertoli cell also consumes excess material left behind after the sperm cells have completed development. Another function of a Sertoli cell is to control the movement of hormones, nutrients and chemicals into the seminiferous tubules.
Spermatogenesis is a complex process that begins in the seminiferous tubule, a structure within the testicle. Sertoli cells are produced within this structure and line the interior of the tubules. They are activated by follicle-stimulating hormone (FSH), which interacts with the FSH-receptors on Sertoli cells. The full process of spermatogenesis takes about 64 days in the human male. During the course of the development of the spermatozoa, the Sertoli cell triggers several phases of growth by excreting certain substances. For example, spermatogenesis begins when Sertoli cells secrete a protein to increase the concentration of testosterone in the seminiferous tubules.
Puberty triggers the beginning of spermatogenesis, and the process continues throughout a male's lifetime. Overall production of spermatozoa tends to decrease with age but, in a healthy individual, never stops. The number of available spermatozoa, their motility and the individual's overall fertility are determined by the efficiency and proper functioning of spermatogenesis. During spermatogenesis, the germ cells, which are the cells from which mature sperm eventually grow, actually travel along Sertoli cells as their development progresses.
One form of infertility specifically related to the Sertoli cell is Sertoli-cell-only syndrome. In this condition, the seminiferous tubules contain only Sertoli cells, making it impossible for the testes to produce sperm. The condition typically is diagnosed when men who are concerned about their fertility are tested and shown to have no sperm in their ejaculate. Sertoli-cell-only syndrome is very rare, and the cause is unknown.
Sertoli cells are not capable of reproducing themselves, and after spermatogenesis begins in an adolescent male, no more Sertoli cells are produced by the body. Techniques have been developed, however, to grow the cells in laboratory conditions. Some forms of human infertility might be treatable through the use of these cells.