Sertoli cells are a distinct cell type located within the seminiferous tubules of the testes, the male reproductive glands responsible for sperm production. These somatic cells support germ cell development. They are a fundamental component of the male reproductive system, creating the environment where sperm mature. Each human testis contains approximately 30-50 million Sertoli cells, which contribute to regulating the conditions necessary for sperm development.
The “Nurse Cells” of the Testes
Sertoli cells are often referred to as “nurse cells” due to their direct involvement in nurturing and supporting developing sperm, a process known as spermatogenesis. Within the seminiferous tubules, these cells provide structural support, enveloping the various stages of germ cells. This physical association is maintained through cytoplasmic processes, forming a network where germ cells reside and develop.
Beyond structural support, Sertoli cells deliver essential nutrients, energy substrates like lactate derived from glucose, and growth factors for germ cell differentiation and maturation. They also facilitate the removal of metabolic waste products, maintaining an optimal environment for sperm development. This interaction allows immature germ cells to progress through their developmental stages, ultimately leading to the formation of fertile spermatozoa.
Other Vital Functions
Beyond their direct nurturing role, Sertoli cells perform additional functions. They establish the blood-testis barrier, formed by tight junctions between adjacent Sertoli cells. This barrier segregates the seminiferous epithelium into two distinct compartments, isolating developing sperm from the bloodstream and protecting them from potential immune attacks or harmful substances. This separation is important because mature sperm cells are recognized as foreign by the male immune system, and the barrier prevents an immune response that could damage them.
Sertoli cells also have endocrine functions, producing and secreting hormones and binding proteins. One such hormone is inhibin B, which helps regulate the hypothalamic-pituitary-gonadal axis by suppressing the release of follicle-stimulating hormone (FSH) from the pituitary gland. Another hormone is anti-Müllerian hormone (AMH), secreted by immature Sertoli cells during fetal development, which causes the regression of Müllerian ducts, structures that would otherwise develop into female reproductive organs. These secretions contribute to the proper development and regulation of the male reproductive system throughout life.
Sertoli Cells and Male Reproductive Health
The combined actions of Sertoli cells are important for maintaining male reproductive health and fertility. Their multifaceted roles ensure the continuous and orderly production of healthy sperm, a process called spermatogenesis. By providing structural support, nourishment, and a controlled microenvironment, Sertoli cells enable germ cells to develop into mature sperm.
The integrity of the blood-testis barrier, maintained by Sertoli cells, shields developing sperm from immune surveillance and toxins, preserving their viability. The hormones produced by Sertoli cells, such as inhibin B and AMH, contribute to the hormonal balance that governs male reproductive function from development through adulthood. Properly functioning Sertoli cells directly support sperm quantity and quality, which are factors for male fertility.
Understanding Sertoli Cell Dysfunction
When Sertoli cells do not function as they should, it can lead to male infertility. Impaired Sertoli cell function often results in disrupted spermatogenesis, leading to reduced sperm count or poor sperm quality. This dysfunction can manifest as problems with sperm development, maturation, or increased oxidative stress and DNA damage within germ cells.
One specific condition linked to severe Sertoli cell dysfunction is Sertoli cell-only syndrome (SCOS), also known as germ cell aplasia. In SCOS, the seminiferous tubules contain only Sertoli cells, with a complete absence of germ cells, resulting in azoospermia. While the exact cause of SCOS is not always clear, proposed factors include genetic abnormalities, exposure to certain chemicals or toxins, radiation therapy, or severe testicular trauma. Metabolic disorders, such as diabetes, can also impair Sertoli cell function by compromising glucose transport and lactate production, thereby affecting energy supply to germ cells.