What Are Leydig Cells?

Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.

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You may have heard or read about leydig cells and have a brief idea about them. They're part of the endocrine system in your body, as such are associated with hormones. In this article we look to explain what leydig cells are, their function, location and anatomy. 

What are Leydig Cells?

Scientists at Johns Hopkins Bloomberg School of Public Health recently discovered a new way to study stem cells. Adult testes contain stem cells capable of giving rise to new Leydig cells. These cells produce testosterone, which affects the male reproductive system, muscle mass, cognition, libido, and a variety of other bodily functions. Adult Leydig cells (ALC) rarely die or divide. However, when experimentally depleted, they regenerate. This is due to their ability to remain quiescent, and the cells that surround them.

A common pathology involving Leydig cells is called Klinefelter syndrome. Patients with Klinefelter syndrome have low levels of testosterone and abundant Leydig cells. During puberty, these cells become markedly active and accumulate steroid precursors. However, this does not mean that these cells are caused by any enzyme deficiency or defect. 

The Leydig cell is a type of interstitial cell found adjacent to the seminiferous tubules of the testes. They synthesize testosterone and release a family of hormones. These cells are often related to nerve cells and release hormones. When the Luteinizing hormone (Lh) stimulates cholesterol desmolase activity in Leydig cells, testosterone is secreted. Until puberty, Leydig cells are inactive.

The Leydig cell tumor has no known cause and no risk factors. In young males, the tumor tends to be benign. However, if the tumor develops in a child, precocious puberty may occur. Leydig cell tumors are rare, making up only a small percentage of all testicular tumors. They usually occur in men between the ages of 30 and 60. Most people who develop a leydig cell tumor are young adult males, but sometimes it can occur in children before puberty.

Where Are Leydig Cells Present?

The origin of adult Leydig cells is poorly understood. While we have data on the development of stem cells and precursor cells, very little is known about ALCs. This has limited the study of ALCs. To overcome this problem, this study used rodent and human solute carriers (SLCs) as models. The results show that the cells of the interstitial tissue have a number of characteristics that are similar to those of their human counterparts.

The appearance of Leydig cells is best understood using the Hematoxylin-Eosin staining technique, which helps distinguish different populations of cells. The color of the cells depends on their lipid content and steroid synthesis. The gubernaculum ligament regulates the transabdominal phase of testicular descent. Insulin-like factor 3 allows the testicles to descend towards the scrotum. As a result, the temperature of the scrotum is ideal for spermatogenesis. This can lead to infertility or even cryptorchidism.

Adult Leydig cells are thought to originate from stem cells. They appear as smaller cells during differentiation and remain present throughout an adult. Adult Leydig cells have a smaller number of lipid droplets and persist as testis cord outer layers. In adult testis, Leydig cells are found adjacent to seminiferous tubules. In addition to Leydig cells, the testes produce hormones called androgens. These hormones control sexual behavior in adulthood.

Where Do Leydig Cells Come From?

The origin of Leydig cells is unknown, but they are believed to be myoid and express high amounts of a-actin protein. In postnatal humans, Leydig cells are thought to originate from testicular cells. However, perivascular cells in the interstitial tissue and neural crest cells have also been suggested as possible precursors. Leydig cells express markers common in neuronal and neuroendocrine cells, as well as a phenotype associated with glial cells.

While there is still some uncertainty about their origin, the first step in their development is a better understanding of where they come from. These cells start to differentiate relatively late in the process of testis development, beginning at embryonic day 14.5 in rats and gestational weeks seven to eight in humans. They also appear to develop from undifferentiated mesenchymal cells present in the interstitium.

In the laboratory, stem Leydig cells can be isolated from adult testis tissue by identifyingthe testicular expression CD90, a specific surface marker. CD90 is expressed on seminiferous tubules and myoid cells. These cells differentiate into T and 3bHSD-staining cells. CD90 has been shown to be essential for the differentiation of stem Leydig cells. The research is important because it can be used to limit the incidence of male reproductive pathologies, and it can help with ovarian cysts and melanoma.

Stem Leydig cells have similar gene expression patterns to those of bone marrow stem cells, although the expression of some genes is different. As they undergo differentiation, they differentiate into immature and adult Leydig cells. However, their number does not change as adults. This suggests that their number may be underestimated in the early studies. So, it's unclear how much control these cells have over the process of fetal development.

How Do Leydig Cells Function?

The cell types are derived from the coelomic epithelium, the gonadal ridge, and migrating mesonephric cells. Endothelial cells derived from the mesonephros are important precursors of vascular and peritubular myoid lineages. They may be ancestral cells of fetal Leydig cells. Moreover, they may have evolved from the neural crest or even from slight modifications of fetal adrenal cells.

Further studies are needed to understand the function of Leydig cells and the cyclic gene expressions that they contain. It is important to note that the expression of Leydig cell transcripts varies stage-specifically, whereas the gene expression of seminiferous epithelium cells did not cycle. Nonetheless, these results suggest that Leydig cells function in a heterogeneous way and may have a functional role in spermatogenesis.

In addition to expressing ERa, Leydig cells express estrogen receptor a (ERa). ERa null mice display increased serum testosterone levels and lower sperm counts than wild-type mice. Furthermore, ERa-signalling suppresses androgen production in Leydig cells. Environmental estrogenic compounds are widely found in the environment and are also present in food, water, and air. This may adversely affect reproductive functions in humans.

The study also aims to identify which genes are enriched in Leydig cells. It was found that the enriched genes in Leydig cells were associated with lipid metabolism, signaling, secretion, and extracellular matrix region. However, there is still no direct evidence of their effect on reproductive health. However, new approaches are emerging that aim to stimulate the production of Leydig cells' T. In contrast to exogenous T therapy, direct stimulation of Leydig cells is more favorable, as this approach prevents some of the negative effects.

The Anatomy of Leydig Cells

Leydig cells are the primary source of testosterone in males, and they play an important role in controlling many physiological processes in males. Their primary function is the regulation of male urogenital development, as they induce the development of the Wolffian duct. They also help to prevent the development of female genital structures through the production of anti-Mullerian hormone. Leydig cells also have different gene expression profiles in adulthood, and a variety of functions within the testis.

Histology of Leydig Cells

Histology is important for understanding the biology of Leydig cells, which reside within the interstitial space of the testes. They have rounded nuclei and abundant acidophilic cytoplasm, a hallmark of steroid-secreting cells. They are surrounded by a thin layer of contractile myoid cells, which produce waves of contraction. The presence of Leydig cells does not necessarily indicate their function in spermatogenesis.

Leydig cell tumors are relatively uncommon and occur in younger males. Generally, they follow a benign course. They may be symptomless or cause symptoms of impotence and decreased libido. Although rare, they are most often detected by imaging studies. Reinke's crystals, which are present in less than half of all cases, help to confirm a Leydig cell diagnosis. Standard therapy for Leydig cell tumors is radical orchidectomy.

Leydig cells are polygonal cells found in groups of up to ten. Their cytoplasm is eosinophilic, with a prominent nucleolus. They produce testosterone and produce other hormones essential for human reproduction. They also have significant numbers of mitochondria and tubulovesicular cristae. In addition to these characteristics, Leydig cells exhibit extensive amounts of lipofuscin, which is a form of lipid.

Leydig cells are a major source of androgen in males, and their presence in biopsies is associated with impaired spermatogenesis. In men, Leydig cells are found in the interstitial tissue and produce testosterone under the influence of luteinizing hormone, a type of gonadotropin released by the hypothalamic-pituitary axis. The function of Leydig cells in males is vital for sexual development, and these cells may develop pathological conditions or become cancerous.

Leydig cells are located in clusters around seminiferous tubules. They form groups of as many as ten cells. Their cytoplasm is eosinophilic, and their nucleus has a prominent nucleolus. The cells produce testosterone and have large lipid droplets, as well as a significant number of mitochondria and tubulovesicular cristae. Leydig cells also have a substance known as lipofuscin which resembles a sand-like texture and appears as multiple, irregular bodies.

In humans, the interstitial cells of Leydig form in the connective tissue surrounding the sperm-producing tubules in the testes. Leydig cells are the primary source of androgens and are present in nearly all vertebrates. However, the cells are difficult to distinguish by a naked eye. An electron microscope is needed to visualize Leydig cells. They are located in connective tissues and produce testosterone. The anterior pituitary gland stimulates these cells to produce androgens, including testosterone. 

Leydig Cells in Females

Males and females have different kinds of Leydig cells. These cells differentiate after birth and are unrelated to their fetal counterparts. They derive from undifferentiated precursor cells of the interstitium mesenchymal tissue. Their morphology and function are different, but the same cellular functions are shared. The difference between the male and female Leydig cells is their location. Males have bipotential gonads whereas females have only a single bipotential genital duct.

In females, the location of Leydig cells is important for conception. The gonad grows and becomes larger as the Leydig cells migrate to it. The migration of Leydig cells occurs only after the onset of Sry expression in males. The resulting cells give rise to peritubular myoid cells, male-specific vasculature, and steroidogenic Leydig cells. The cells' migration is mediated by neurotropin-3, hepatocyte growth factor, and platelet-derived growth factor.

Once a germ cell has reached the ovaries, it begins a series of significant genetic changes. It starts expressing essential genes for survival and maturation. The sex of the gonadal niche and the chromosome composition seem to play a greater role in determining the fate of the germ cell. The expression of SRY is responsible for the differentiation of male and female germ cells. If Sry fails to express, the ovary will not form.

What Do Leydig Cells Secrete?

During the development of human fetal Leydig cells, three stages occur. The first is differentiation, which occurs between weeks seven and fourteen of gestation. Weeks 14 and 15 are crucial for the mature stage of the cells. Human Leydig cells contain the maximum number per pair of testes. These cells likely derive from coelomic epitheium, mesenchyme of the gonadal ridge, and migrating mesonephric cells.

The development of Leydig cells is regulated by an intricate cocktail of paracrine and endocrine factors. These factors trigger cellular events and optimize male development. This minireview describes the current state of knowledge about human Leydig cells, including the role of recently discovered regulatory factors. In addition, the review describes the current role of Leydig cells in the development of male fetuses.

Leydig cells secrete testosterone. Testosterone is a male hormone produced by the testicles under the control of the pituitary gland. Testosterone causes several physical changes in the body, and is a crucial hormone for reproduction. Testosterone is also secreted by Sertoli cells in the seminiferous tubules. These cells secrete hormones when sperm counts are high, but do not secrete much of this hormone themselves.

In a mouse model, Leydig cells may have evolved from fetal adrenal tissue. Patients who have chronically elevated levels of ACTH may develop ectopic adrenal tissue, which was failed to separate from the gonad during fetal development. In addition, male hypogonadism is associated with certain development of androgen-sensitive organs. They may also have low numbers of Leydig cells in the testis.

The Difference Between Leydig Cells and Sertoli Cells

Although the distinction between Leydig cells and Sertoli is not clear, they appear to have similar functions. Both promote neuronal differentiation and survival in co-cultures and grafts. It is not yet known what their normal physiological role is. However, they appear to produce trophic factors. 

Sertoli cells are essential for the development of the testis. These cells separate from the coelomic epithelium at embryonic day 11.5 in mice. They are responsible for the formation of seminiferous tubules and the fetal Leydig cell population. Their role is vital for spermatogenesis, maintenance of adult Leydig cells, and normal development of testicular vasculature.

In addition, Sertoli cells form the blood-testis barrier and interact with germ cells. However, conventional light microscopy sections do not show them, as they are embedded within them. Sertoli cells are linked to germ cells through numerous and unique cell junctions. They are joined at the basolateral side by specialized occluding junctions, which function as a protective shield against interstitial macrophages.

In addition, both Sertoli cells and Leydig cell populations are important in the development of male characteristics. The former helps to produce testosterone, which plays a key role in spermatogenesis. This enables males to develop the male genitalia and reproduce. But they also produce insulin-like factor 3, which controls the descent of the transabdominal testis. Insufficient amounts of insulin-like factor 3 may lead to cryptorchidism and infertility in adulthood.

A Brief Overview of Sertoli Cells

Sertoli cells have long been described as being important in spermatogenesis. Enrico Sertoli originally called them "mother cells." Besides forming the microenvironment that promotes spermatogenesis, these cells play an important role in testicular immunity. They control testicular immune responses, suppress inflammatory stimuli, and regulate innate immune activities. Here is a brief overview of some of the research on Sertoli cells.

The genes were detected using RT-PCR. The transcription of Sertoli cell genes was analyzed by comparing their levels with control RNA. ACTB served as a loading control. RNA with or without reverse transcriptase enzyme was used as the negative control. RT-PCR revealed that a significant proportion of genes were expressed in Sertoli cells. Some genes were up-regulated, while others were down-regulated.

Purity of Sertoli cells was greater than 95%. Moreover, less than 5% of cells were positive for antibodies against SMA, CYP11A1, and PCNA. Moreover, the proliferation ability of human Sertoli cells was evaluated using a cytometer. It was found that Sertoli cells can proliferate a great deal. But before applying these techniques to test the viability of a cell line, the scientists should make sure that the cells are viable and are capable of proliferating.

Because human Sertoli cells are difficult to obtain from human testis tissues, there are few studies on the cell's function in a male reproductive system. However, adult human Sertoli cells have been cultured for a long period with a significant increase in number. These cells may eventually be used for basic research and clinical applications. The next steps will be the development of a vaccine or cell therapy aimed at the prevention of infertility and other sexually transmitted diseases.

Do Steroli Cells Produce Testosterone?

The question of do steroli cells produce testosterone has captivated researchers for decades. It is important for our understanding of puberty and spermatogenesis. Sertoli cells are required to produce testosterone, and the responsiveness to androgens was examined for a wide age range, from birth to puberty. Researchers discovered that androgens are essential for the spermatogenic process.

In addition to producing testosterone, the testes also play a vital role in reproduction. Both sperm and egg development depend on the activity of Sertoli cells. This is why spermatogenesis takes place near Sertoli cells. These cells promote the proliferation of other cells in the testis. In males, testosterone is important for sperm quality, and a lack of testosterone can cause a range of reproductive problems.

Sertoli cells secrete various hormones and proteins that are necessary for spermatogenesis. It is also believed that these cells play a role in hormonal regulation of spermatogenesis. The number of Sertoli cells in a man's testes determines the rate at which sperm develop. Although adult men don't produce Sertoli cells, their numbers are determined at puberty.

Sertoli cells serve several important functions in the testis. The Sertoli cells are responsible for the blood-testis barrier, which partitions the interstitial blood compartment from the adluminal compartment of seminiferous tubules. They also perform a number of functions such as DNA repair, phagocytosis, and modulating the immune system. They are critical to male sexual development, as they can't proliferate on their own.