Peritubular myoid cell

Last updated
Peritubular myoid cell
Histological structure of seminiferous tubules in the adult mouse testes..jpg
Peritubular myoid cells in the adult mouse testis
Details
System Reproductive, muscular
LocationTestis
FunctionContraction and transport of spermatoza through the tubules of the testis
Anatomical terms of microanatomy

A peritubular myoid (PTM) cell is one of the smooth muscle cells which surround the seminiferous tubules in the testis. [1] [2] These cells are present in all mammals but their organization and abundance varies between species. [2] The exact role of PTM cells is still somewhat uncertain and further work into this is needed. However, a number of functions of these cells have been established. They are contractile cells which contain actin filaments and are primarily involved in transport of spermatozoa through the tubules. [2] They provide structural integrity to the tubules through their involvement in laying down the basement membrane. [3] This has also been shown to affect Sertoli cell function and PTM cells also communicate with Sertoli cells through the secretion of growth factors and ECM (extra-cellular matrix) components. [3] [2] Studies have shown PTM cells to be critical in achieving normal spermatogenesis. [3] Overall, PTM cells have a role in both maintaining the structure of the tubules and regulating spermatogenesis through cellular interaction. [2] [1]

Contents

Structure

PTM cells are endothelial cells which are understood to have derived from mesonephric cells. [4] The structure and organization between PTM cells have been observed to be distinctly different between mammalian species. In humans, PTM cells are spindle shaped and form several thin elongated layers, approximately 5-7 cell layers, and surround Sertoli cells.

These are detected in the lamina propria of the seminiferous tubule and immunohistochemical studies have shown functional distinctions between these layers. The inner layers have been shown to express desmin, a smooth muscle phenotype, whereas the outer layers express vimentin, a connective tissue phenotype. [2]

In rodents, PTM cells are one layer thick. Both human and rodent PTM cells are joined by junctional complexes. [2]

Function

Contractile

Peritubular myoid cells are responsible for the contractile nature of the seminiferous tubule. This contraction helps move the spermatozoa and fluid to the rete testes. [5] There are a number of mediators involved in the regulation of contraction. Oxytocin produced by leydig cells has been shown to be a driving factor in the contractions by acting on peritubular myoid cells. [6] As no oxytocin receptors are found on the peritubular myoid cells it is thought the oxytocin causes the activation of the vasopressin receptors. However, the full mechanisms behind the contractibility are unknown. Other factors including transforming growth factor b, prostaglandins and nitric oxide are also thought to be involved. [2]

Spermatogonial stem cell self-renewal

Peritubular myoid cells play a crucial role in the self-renewal and maintenance of the spermatogonial stem cell (SSC) population. For those SSCs destined to form differentiating progenitor A1 spermatogonia (and hence spermatozoa), this is initiated at a defined stage during the spermatogenic cycle. [7] The precise location of SSCs throughout various staged cohorts of the seminiferous tubule determines their renewal function, to continuously produce progeny. [1] During stages II and IV of spermatogenesis, GDNF is secreted by peritubular myoid cells upon testosterone binding the androgen receptor (in contrast to GDNF secretion by the Sertoli cells during stages IX and I). [1] Following this, GDNF binds GFRA1 on spermatogonial stem cells, and RET co-receptor (a transmembrane tyrosine kinase) is consequently signalled throughout all undifferentiated spermatogonia. Thus, SFK signalling is upregulated and genes encoding key transcription factors (bcl6b, brachyury, Id4, Lhx1) become activated. [1] The histochemical marker, alkaline phosphatase (stimulated by testosterone and retinol) has been useful for investigating peritubular myoid cell function and differentiation, as it has been shown to have activity in the peritubular myoid cell of the rat. [2]

Differentiation

PTMs become recognisable at 12 weeks gestation in humans, and 13.5 days post conception in mice. [8] However, where they arise from is currently unclear. Previous studies suggested that PTMs originate from a group of cells called mesonephric cells, which migrate into the developing gonad from an adjacent area called the mesonephric primordia. [3] It was thought that the mesonephric cells would then have one of three fates: becoming Leydig cells, vascular tissue or myoid cells. Those becoming myoid cells would sit on a basement membrane surrounding the developing seminiferous tubules. [3]

However, more recent evidence has found that mesonephric cells do not give rise to PTMs but instead have only a vascular fate, [8] leaving more uncertainty over where PTMs come from. The main difficulty in studying the development of PTMs is the lack of a molecular marker specific to them that is visible during early differentiation of the testis. [8]

Current knowledge suggests that PTMs arise from cells within the developing gonad itself, or alternatively from a layer of cells surrounding the outside of the gonad, called coelomic epithelium, by a process named epithelial-mesenchymal transition. [8]

PTMs acquire androgen receptors during their development, enabling them to respond to androgens which help them to maintain seminiferous tubule function. [3]

History

PTMs were first observed in 1901, when Claudius Regaud made a detailed study of the histology and physiology of the seminiferous tubules in rats. [9] He described the PTMs as a single layer of flattened cells, which enclose the seminiferous tubules, and called them ‘’modified connective tissue cells’’.

In 1958, Yves Clermont made a further investigation of the cells by electron microscopy. He found that these cells have a cytological resemblance to smooth muscle cells – they contain actin filaments, have invaginations at the cell surface and their organelles are located in the centre of the cell. He also suggested that these cells are responsible for the tubular contraction and referred to them as ‘’interlamellar cells’’. [2]

Subsequently, in 1967, Michael Ross studied the fine structure of these cells in mice and proved that the smooth muscle-like cells are contractile. He called them ‘’peritubular contractile cells’’. In 1969, Don Wayne Fawcett et al. termed these cells ‘’peritubular myoid cells’’, because of their similarities to smooth muscle cells. [2]

Etymology

As PTMs became better characterized, the associated nomenclature underwent a series of changes.

In very early literature these cells may be referred to as ‘modified connective tissue cells’ or ‘interlamellar cells’. Subsequent experiments resulted in renaming these cells to better reflect their contractile nature. The term ‘peritubular contractile cells’ was first used in 1967. [2]

In 1969, Don Fawcett labelled these cells as ‘peritubular myoid cells’. ‘Peritubular’ refers to their anatomical location: adjacent to the seminiferous tubule. ‘Myoid’ stems from the Greek ‘myo’ (/ˈmʌɪəʊ/), which means relating to muscle. (PTMs resemble smooth muscle cells under an electron microscope). [2]

Related Research Articles

Testicle Internal organ in the male reproductive system

A testicle or testis is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testosterone. Testosterone release is controlled by the anterior pituitary luteinizing hormone, whereas sperm production is controlled both by the anterior pituitary follicle-stimulating hormone and gonadal testosterone.

Androgen Any steroid hormone that promotes male characteristics

An androgen is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes the embryological development of the primary male sex organs, and the development of male secondary sex characteristics at puberty. Androgens are synthesized in the testes, the ovaries, and the adrenal glands.

Germ cell Gamete-producing cell

A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm. Unlike animals, plants do not have germ cells designated in early development. Instead, germ cells can arise from somatic cells in the adult, such as the floral meristem of flowering plants.

Epididymis Tube that connects a testicle to a vas deferens

The epididymis is a tube that connects a testicle to a vas deferens in the male reproductive system. It is present in all male reptiles, birds, and mammals. It is a single, narrow, tightly-coiled tube in adult humans, 6 to 7 meters in length connecting the efferent ducts from the rear of each testicle to its vas deferens.

Spermatogenesis Production of sperm

Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules. These cells are called spermatogonial stem cells. The mitotic division of these produces two types of cells. Type A cells replenish the stem cells, and type B cells differentiate into primary spermatocytes. The primary spermatocyte divides meiotically into two secondary spermatocytes; each secondary spermatocyte divides into two equal haploid spermatids by Meiosis II. The spermatids are transformed into spermatozoa (sperm) by the process of spermiogenesis. These develop into mature spermatozoa, also known as sperm cells. Thus, the primary spermatocyte gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa and four haploid cells.

Seminiferous tubule Location of meiosis and creation of spermatozoa

Seminiferous tubules are located within the testes, and are the specific location of meiosis, and the subsequent creation of male gametes, namely spermatozoa.

Sertoli cell

A Sertoli cell is a "nurse" cell of the testicles that is part of a seminiferous tubule and helps in the process of spermatogenesis, the production of sperm.

Spermatocyte Sperm precursor cell that undergoes meiosis

Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules. There are two types of spermatocytes, primary and secondary spermatocytes. Primary and secondary spermatocytes are formed through the process of spermatocytogenesis.

Male reproductive system Reproductive system of the human male

The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction. These organs are located on the outside of the body and within the pelvis.

Spermatogonium Undifferentiated male germ cell

A spermatogonium is an undifferentiated male germ cell. Spermatogonia undergo spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testis.

Spermiogenesis Final stage of spermatogenesis, involving spermatid maturation

Spermiogenesis is the final stage of spermatogenesis, which sees the maturation of spermatids into mature spermatozoa. The spermatid is a more or less circular cell containing a nucleus, Golgi apparatus, centriole and mitochondria. All these components take part in forming the spermatozoon.

Blood–testis barrier A physical barrier between the blood vessels and the seminiferous tubules of the animal testes

The blood–testis barrier is a physical barrier between the blood vessels and the seminiferous tubules of the animal testes. The name "blood-testis barrier" is misleading in that it is not a blood-organ barrier in a strict sense, but is formed between Sertoli cells of the seminiferous tubule and as such isolates the further developed stages of germ cells from the blood. A more correct term is the "Sertoli cell barrier" (SCB).

Androgen-binding protein (ABP) is a glycoprotein (beta-globulin) produced by the Sertoli cells in the seminiferous tubules of the testis that binds specifically to testosterone (T), dihydrotestosterone (DHT), and 17-beta-estradiol.

Spermatogenesis arrest is known as the interruption of germinal cells of specific cellular type, which elicits an altered spermatozoa formation. Spermatogenic arrest is usually due to genetic factors resulting in irreversible azoospermia. However some cases may be consecutive to hormonal, thermic, or toxic factors and may be reversible either spontaneously or after a specific treatment. Spermatogenic arrest results in either oligospermia or azoospermia in men. It is quite a difficult condition to proactively diagnose as it tends to affect those who have normal testicular volumes; a diagnosis can be made however through a testicular biopsy.

Stem-cell niche refers to a microenvironment, within the specific anatomic location where stem cells are found, which interacts with stem cells to regulate cell fate. The word 'niche' can be in reference to the in vivo or in vitro stem-cell microenvironment. During embryonic development, various niche factors act on embryonic stem cells to alter gene expression, and induce their proliferation or differentiation for the development of the fetus. Within the human body, stem-cell niches maintain adult stem cells in a quiescent state, but after tissue injury, the surrounding micro-environment actively signals to stem cells to promote either self-renewal or differentiation to form new tissues. Several factors are important to regulate stem-cell characteristics within the niche: cell–cell interactions between stem cells, as well as interactions between stem cells and neighbouring differentiated cells, interactions between stem cells and adhesion molecules, extracellular matrix components, the oxygen tension, growth factors, cytokines, and the physicochemical nature of the environment including the pH, ionic strength and metabolites, like ATP, are also important. The stem cells and niche may induce each other during development and reciprocally signal to maintain each other during adulthood.

The development of the gonads is part of the prenatal development of the reproductive system and ultimately forms the testes in males and the ovaries in females. The gonads initially develop from the mesothelial layer of the peritoneum.

Sertoli cell-only syndrome is a disorder characterized by male sterility without sexual abnormality. It describes a condition of the testes in which only Sertoli cells line is present in seminiferous tubules.

Gonocytes are the precursors of spermatogonia that differentiate in the testis from primordial germ cells around week 7 of embryonic development and exist up until the postnatal period, when they become spermatogonia. Despite some uses of the term to refer to the precursors of oogonia, it was generally restricted to male germ cells. Germ cells operate as vehicles of inheritance by transferring genetic and epigenetic information from one generation to the next. Male fertility is centered around continual spermatogonia which is dependent upon a high stem cell population. Thus, the function and quality of a differentiated sperm cell is dependent upon the capacity of its originating spermatogonial stem cell (SSC).

Spermatogonial stem cell Spermatogonium that does not differentiate into a spermatocyte

A spermatogonial stem cell (SSC), also known as a type A spermatogonium, is a spermatogonium that does not differentiate into a spermatocyte, a precursor of sperm cells. Instead, they continue dividing into other spermatogonia or remain dormant to maintain a reserve of spermatogonia. Type B spermatogonia, on the other hand, differentiate into spermatocytes, which in turn undergo meiosis to eventually form mature sperm cells.

In vitro spermatogenesis is the process of creating male gametes (spermatozoa) outside of the body in a culture system. The process could be useful for fertility preservation, infertility treatment and may further develop the understanding of spermatogenesis at the cellular and molecular level. 

References

  1. 1 2 3 4 5 Potter, Sarah J.; DeFalco, Tony (April 2017). "Role of the testis interstitial compartment in spermatogonial stem cell function". Reproduction (Cambridge, England). 153 (4): R151–R162. doi:10.1530/REP-16-0588. ISSN   1741-7899. PMC   5326597 . PMID   28115580.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 Maekawa, M.; Kamimura, K.; Nagano, T. (March 1996). "Peritubular myoid cells in the testis: their structure and function". Archives of Histology and Cytology. 59 (1): 1–13. doi: 10.1679/aohc.59.1 . ISSN   0914-9465. PMID   8727359.
  3. 1 2 3 4 5 6 H., Johnson, M. (2007). Essential reproduction. Everitt, Barry J. (6th ed.). Malden, Mass.: Blackwell Pub. ISBN   9781405118668. OCLC   76074156.
  4. ↑ Virtanen, I.; Kallajoki, M.; Närvänen, O.; Paranko, J.; Thornell, L. E.; Miettinen, M.; Lehto, V. P. (May 1986). "Peritubular myoid cells of human and rat testis are smooth muscle cells that contain desmin-type intermediate filaments". The Anatomical Record. 215 (1): 10–20. doi:10.1002/ar.1092150103. ISSN   0003-276X. PMID   3518542. S2CID   37224676.
  5. ↑ Díez-Torre, A.; Silván, U.; Moreno, P.; Gumucio, J.; Aréchaga, J. (2011-08-01). "Peritubular myoid cell-derived factors and its potential role in the progression of testicular germ cell tumours". International Journal of Andrology. 34 (4pt2): e252–e265. doi: 10.1111/j.1365-2605.2011.01168.x . ISSN   1365-2605. PMID   21623832.
  6. ↑ H., Johnson, M. (2013). Essential reproduction. Johnson, M. H. (Seventh ed.). Chichester, West Sussex: Wiley-Blackwell. ISBN   9781444335750. OCLC   794603121.
  7. ↑ de Rooij, Dirk G; Grootegoed, J Anton (1998). "Spermatogonial stem cells". Current Opinion in Cell Biology. 10 (6): 694–701. doi:10.1016/s0955-0674(98)80109-9. PMID   9914171.
  8. 1 2 3 4 Svingen, Terje; Koopman, Peter (2013-11-15). "Building the mammalian testis: origins, differentiation, and assembly of the component cell populations". Genes & Development. 27 (22): 2409–2426. doi:10.1101/gad.228080.113. ISSN   0890-9369. PMC   3841730 . PMID   24240231.
  9. ↑ Del Regato, Juan A. (1993). Radiological oncologists : the unfolding of a medical specialty. Reston, VA: Radiology Centennial. ISBN   9781559031356. OCLC   28968122.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.