Sertoli cells are specialized cells of the seminiferous tubules that support the production of sperm cells. Together, they form the blood-testes barrier, which divides the seminiferous tubules into two compartments and creates a protective, nourishing environment for spermatogenesis. Sertoli cells also function as phagocytes to remove excess cytoplasm and apoptotic sperm cells from the seminiferous tubules and play a central role in the sexual differentiation of human embryos.
What is a Sertoli Cell?
Sertoli cells are specialized epithelial cells in the seminiferous tubules of the male testes. They are the supporting cells for spermatogenesis, and their primary role is to protect and nourish germ cells as they develop into sperm. They also produce androgen binding protein, which binds and concentrates testosterone in the seminiferous tubules.
Location of Sertoli Cells
Sertoli cells line the epithelium of the seminiferous tubules in the male testes, which is where spermatogenesis takes place.
Functions of Sertoli Cells
Sertoli cells are found in the seminiferous tubules of the male testes, where they have several roles in supporting sperm development.
Support of Spermatogenesis
Sertoli cells are often referred to as ‘nurse cells’ due to their role in supporting the development of sperm cells in the testes. Mature spermatozoa develop via meiosis from germ cells in the seminiferous tubules. Sertoli cells form protective pockets around the germ cells and release nutrients to support their development into spermatozoa.
Sertoli cells also act as phagocytes and remove apoptotic sperm cells and excess cytoplasm from the seminiferous tubules. Residual cytoplasm is a by-product of spermatogenesis, and apoptosis is a fate that affects over half of developing sperm cells before they reach maturity. Therefore, Sertoli cells have an important role in clearing unwanted materials from the seminiferous tubules.
Production of Androgen Binding Protein (ABH)
Another important function of Sertoli cells is to produce androgen binding protein (ABP); a glycoprotein that specifically binds to testosterone. ABP increases the concentration of testosterone in the seminiferous tubules, which is essential for the complete maturation and release of sperm cells. Therefore, ABP is a crucial component of spermatogenesis
Male Embryonic Development
Sertoli cells develop in response to a signal from a gene on the Y chromosome and initiate the development of testes in male embryos. They also secrete a hormone called the Anti-Mullerian Hormone (AMH), which suppresses the development of female sex organs and germ cells.
Leydig cells (another specialized cell of the testes) secrete testosterone, which supports the development of male sexual organs. Therefore, both Sertoli cells and Leydig cells are vital for male embryonic development.
Sertoli Cells and the Blood-testes Barrier
Sertoli cells are connected by continuous tight junctions which form the blood-testes barrier.
The blood-testes barrier divides the seminiferous tubules into two compartments; the basal compartment, and the adluminal compartment. The basal compartment contains spermatogonia (i.e., male germ cells), and the adluminal compartment houses developing sperm cells. Large molecules cannot cross the blood-testes barrier, so the adluminal compartment is effectively isolated from the basal compartment and the blood. This creates a protective microenvironment that supports the development and maturation of sperm cells.