Sertoli cells are the support cells of the testes, often called nurse cells because they look after developing sperm. Because each one can support only a limited number of developing sperm, the number and health of a man’s Sertoli cells quietly sets an upper limit on how much sperm he can make.
Where Sertoli Cells Live and What They Look Like
The testes are packed with tiny coiled tubes where sperm are made. Sertoli cells stand along the wall of these tubes, reaching from the outer edge toward the hollow center. Their cytoplasm sends out branches that cradle developing germ cells, a shape first described about 150 years ago by Enrico Sertoli.1PubMed Central. The Sertoli cell: one hundred fifty years of beauty and plasticity The structure is one of the most complex three-dimensional shapes of any cell, and a large, distinctive structure inside the nucleus is still how they’re recognized under a microscope.2PubMed Central. The Sertoli cell: one hundred fifty years of beauty and plasticity
Stem cells sit near the outer rim, against the base of the Sertoli cells. More mature cells sit higher up, closer to the hollow middle. Finished sperm are released into the center and flow out toward the epididymis.
Between the tubes sit Leydig cells, which make testosterone. Sertoli cells are inside the tubes and do not make testosterone; they respond to it.3PubMed. Testosterone augments FSH signaling by upregulating the expression and activity of FSH-Receptor in Pubertal Primate Sertoli cells
How Sertoli Cells Feed and Move Developing Sperm
Sertoli cells provide the nutrients and structural support germ cells need to develop.4PubMed. Metabolic pathways and male fertility: exploring the role of Sertoli cells in energy homeostasis and spermatogenesis They take in mostly glucose and turn most of it into lactate rather than burning it themselves.5PubMed. Metabolic regulation is important for spermatogenesis Lactate then becomes the main energy source for developing sperm cells and helps keep them from dying off.6PubMed. Metabolic regulation is important for spermatogenesis Even before birth, Sertoli cells store glycogen and pass lactate to early germ cells, at least in mice.7PubMed Central. Glycogen and lactate metabolism in mouse fetal Sertoli cells sustain the germ line
Sertoli cells also hold the sperm stem cells in place and release growth signals.8PubMed Central. Gdnf signaling pathways within the mammalian spermatogonial stem cell niche Those signals let stem cells both renew themselves and produce new cells that become sperm.9PubMed Central. Microenvironment of spermatogonial stem cells: a key factor in the regulation of spermatogenesis
Developing sperm cannot move by themselves at this stage. Sertoli cells carry them up and down through the tube wall using internal tracks made of protein fibres.10PubMed Central. Regulation of actin dynamics and protein trafficking during spermatogenesis – insights into a complex process These tracks and the joints between cells are constantly rebuilt as cells pass through.11PubMed Central. Transport of germ cells across the seminiferous epithelium during spermatogenesis—the involvement of both actin- and microtubule-based cytoskeletons Sertoli cells also clean up leftover cell material shed by maturing sperm, and they control timing by signaling when cells advance.
The Blood-Testis Barrier and Immune Protection
Neighbouring Sertoli cells lock together with tight seals, forming what is called the blood-testis barrier.12PubMed Central. Sertoli Cell Immune Regulation: A Double-Edged Sword This seal blocks even small molecules from leaking across the tube wall.13PubMed Central. Sertoli cells- Immunological sentinels of spermatogenesis It also divides the tube into an outer compartment and an inner one where sperm mature.14PubMed. Blood-testis barrier: a review on regulators in maintaining cell junction integrity between Sertoli cells Yet it opens and reseals in a controlled way to let developing cells pass inward.15PubMed. Blood-testis barrier: a review on regulators in maintaining cell junction integrity between Sertoli cells
The barrier controls what reaches germ cells, keeps out toxins, and prevents the immune system from attacking them.16PubMed Central. Sertoli Cell Immune Regulation: A Double-Edged Sword That last job matters because maturing sperm carry new proteins the body never learned to recognise as “self.” Sertoli cells also use transporters to move chosen substances in and out.17PubMed Central. Sertoli Cell Immune Regulation: A Double-Edged Sword The result is striking: antibody levels inside the tubes are undetectable, and only about 0.2% of blood levels in nearby fluid.18PubMed Central. Sertoli Cell Immune Regulation: A Double-Edged Sword Injury or surgery that breaks the seal can lead to antibodies against sperm, which is one reason testicular trauma can affect fertility.
How Sertoli Cells Respond to Hormones
FSH, follicle-stimulating hormone from the pituitary gland in the brain, acts on Sertoli cells to support sperm production.19PubMed Central. Hormone Regulation in Testicular Development and Function Within the testes, the receptor for FSH sits only on Sertoli cells.20PubMed Central. Hormone Regulation in Testicular Development and Function Testosterone works together with FSH, increasing how strongly Sertoli cells respond to it.21PubMed. Testosterone augments FSH signaling by upregulating the expression and activity of FSH-Receptor in Pubertal Primate Sertoli cells
The signaling runs both ways. Sertoli cells release a hormone called inhibin B, which tells the pituitary to make less FSH and keeps levels in balance.22PubMed Central. Hormone Regulation in Testicular Development and Function When Sertoli cells are few or failing, inhibin B tends to fall and FSH rises.
That is why doctors often check FSH when sperm counts are low. A high FSH can hint that the testes aren’t responding well. Inhibin B is sometimes measured as a more direct readout of Sertoli cell activity. Neither result alone diagnoses the cause; a specialist interprets them together.
Taking testosterone can lower sperm. Extra testosterone signals the brain to cut FSH and LH, so Sertoli cells lose the signals they need, and sperm counts can drop sharply. Men hoping for children should raise this with their doctor before starting it.
Sertoli Cells Make a Fetus Male
The SRY gene on the Y chromosome turns on in early Sertoli cells around week 7 of pregnancy.23PubMed Central. Testicular Sertoli Cell Hormones in Differences in Sex Development It triggers a second gene, SOX9, which drives the formation of testes.24PubMed Central. Unveiling the roles of Sertoli cells lineage differentiation in reproductive development and disorders: a review Without SRY, the same early cells would become ovary support cells instead.25PubMed Central. Unveiling the roles of Sertoli cells lineage differentiation in reproductive development and disorders: a review Once testes form, their hormones shape most male body features.26PubMed Central. Unveiling the roles of Sertoli cells lineage differentiation in reproductive development and disorders: a review
Before any male hormone exists, Sertoli cells organise the other cells into testis cords. They also release a hormone that removes the would-be uterus.
When the switch doesn’t flip normally, changes in these genes can cause differences in sex development. A person can be XY yet develop ovary-like tissue, or the reverse. These conditions are usually found at birth or puberty, and specialist teams handle diagnosis and care.
When Sertoli Cells Fail, Infertility and Sertoli Cell-Only Syndrome
Some men have azoospermia, meaning no sperm in the semen, without any blockage. In some of them, the seals between Sertoli cells are irregular or missing.27PubMed. Evaluation of blood-testis barrier integrity in terms of adhesion molecules in nonobstructive azoospermia In mice, losing a single gene breaks the barrier and halts sperm production.28PubMed Central. The Wilms Tumor Gene, Wt1, Is Critical for Mouse Spermatogenesis via Regulation of Sertoli Cell Polarity and Is Associated with Non-Obstructive Azoospermia in Humans
In Sertoli cell-only syndrome, the tubes contain Sertoli cells but no sperm-making cells. It can only be confirmed by a testicular biopsy.29PubMed Central. Sertoli cell-only syndrome: etiology and clinical management It can come from Klinefelter syndrome, but most men with it have normal chromosomes.30PubMed Central. Sertoli cell-only syndrome: etiology and clinical management So far only two genes, FANCA and FANCM, are convincingly linked to it.31PubMed Central. Sertoli cells-only syndrome: current clinical approaches and ongoing research trends Some men have scattered patches still making sperm, which surgeons can sometimes retrieve for IVF.
The path to diagnosis usually starts with a semen test that shows no sperm, repeated to confirm. Blood tests then check FSH, testosterone and chromosomes, and an ultrasound or exam looks for a blockage. A biopsy finally reveals whether the tubes hold only Sertoli cells.
After that diagnosis, microsurgical sperm extraction can search for small working areas. Success varies and is not guaranteed. If none are found, donor sperm or adoption are alternatives, and genetic counselling helps if a gene cause is suspected.
Sertoli Cell Tumours
Sertoli cell tumours are rare, and most are benign. They come in several subtypes that differ in age of onset, whether both testes are affected, hormone production, and cancer risk.32Urologia Internationalis. Testicular Sertoli Cell Tumours and Relative Sub-Types: Analysis of Clinical and Prognostic Features One subtype, large-cell calcifying tumour, appears in both testes in 20 to 40% of cases, more often with inherited syndromes.33PubMed Central. Large-cell calcifying Sertoli cell tumors of the testes in pediatrics About 17% of that subtype are cancerous, mostly in older men around 39 on average versus 17 for benign ones.34PubMed Central. Large-cell calcifying Sertoli cell tumors of the testes in pediatrics Size over 4 cm and dead tissue inside are warning signs of cancer.35PubMed Central. Large-cell calcifying Sertoli cell tumors of the testes in pediatrics
Any painless lump or swelling in a testicle deserves a prompt doctor visit, and ultrasound is the usual first test. Most testicular lumps are not Sertoli cell tumours. Hormone effects, such as breast swelling in boys, can be a clue that one is present.
What Can Harm Sertoli Cells
Phthalates, cadmium, the weedkiller atrazine, fine air pollution, heat and obesity can all disturb Sertoli cell energy use.36PubMed. Metabolic reprogramming and organelle quality control: The “silent” drivers of Sertoli cell dysfunction under environmental stressors Damage can therefore build long before cells actually die.37PubMed. Metabolic reprogramming and organelle quality control: The “silent” drivers of Sertoli cell dysfunction under environmental stressors In lab dishes, phthalate breakdown products break the seals between Sertoli cells, more so at higher doses.38PubMed. Disruption effects of monophthalate exposures on inter-Sertoli tight junction in a two-compartment culture model
Practical steps are modest. Avoid heating food in soft plastic containers, and limit long hot baths, saunas and laptops on the lap. Reaching a healthier weight can help sperm production. At work, follow protection rules for metals and pesticides.
Most of the evidence comes from lab and animal work, and effects in people depend on dose and duration. Sperm take about two months to regenerate, so improvements show slowly.
How Sertoli Cells Change From Childhood to Old Age
Sertoli cells multiply fastest around age 2 to 2.5 and almost stop by age 6.39PubMed Central. Temporal dynamics of Sertoli and germ cell development in human foetal and prepubertal testis Testosterone signals help them stop dividing and mature.40PubMed Central. Hormone Regulation in Testicular Development and Function Each human Sertoli cell supports only about 3 developing sperm, far fewer than in many animals.41PubMed Central. The Sertoli cell: what can we learn from different vertebrate models? The number made in childhood therefore largely caps adult sperm output.42PubMed Central. The Sertoli cell: what can we learn from different vertebrate models? It is one reason conditions like undescended testes are treated early.
Fish Sertoli cells support 100 to 150 sperm cells each. A chinchilla’s support 14, giving about 60 million sperm per gram daily. Humans make about 4 to 4.5 million per gram.
After the mid-40s, Sertoli cell nuclei enlarge, suggesting the cells work harder to maintain themselves.43PubMed. Ageing in men with normal spermatogenesis alters spermatogonial dynamics and nuclear morphology in Sertoli cells
Sertoli Cells in Medical Research
Sertoli cells’ immune-calming abilities have been tested to protect transplanted cells in diabetes, muscular dystrophy and skin grafts.44PubMed. Sertoli cells for cell transplantation: pre-clinical studies and future perspectives In diabetic mice, adding Sertoli cells extended insulin-cell graft survival from 11 to 32 days.45PubMed. Testicular Sertoli cells exert both protective and destructive effects on syngeneic islet grafts in non-obese diabetic mice Too many Sertoli cells, though, shortened survival to 8 days.46PubMed. Testicular Sertoli cells exert both protective and destructive effects on syngeneic islet grafts in non-obese diabetic mice Separately, lab-grown testis organoids from human stem cells now reproduce a working barrier and hormone response.47PubMed Central. Construction of human pluripotent stem cell-derived testicular organoids and their use as humanized testis models for evaluating the effects of semaglutide
None of this is an approved treatment. Organoids may one day help test how drugs affect fertility, while lab-made sperm for humans remains a future goal.