Human testicular peritubular cells: more than meets the eye

Abstract

In healthy men, several layers of inconspicuously flat cells and extracellular matrix (ECM) proteins build the wall of the seminiferous tubules. The cells of this wall, peritubular cells, are not well characterized. They are smooth-muscle-like and contractile and transport immotile sperm, a function important for male fertility. However, their full functional importance, especially their potential contribution to the paracrine regulation of the male gonad, is unknown. In men with impaired spermatogenesis, the architecture of the tubular wall is frequently altered. Deposits of ECM and morphological changes of peritubular cells imply that functions of peritubular cells may be fundamentally altered. To be able to study human peritubular cells and their functions, a culture method was established. It is based on small biopsies of patients with obstructive azoospermia but normal spermatogenesis (human testicular peritubular cells, HTPCs) and non-obstructive azoospermia, impaired spermatogenesis, and testicular fibrosis (HTPCFs). Results obtained from cellular studies and parallel examinations of biopsies provide insights into the repertoire of the secretion products, contractile properties, and plasticity of human peritubular cells. They produce ECM components, including the proteoglycan decorin, which may influence paracrine signaling between testicular cells. They may contribute to the spermatogonial stem cell niche via secreted factors. They are regulated by mast cell and macrophage products, and in response produce factors that can fuel inflammatory changes. They possess a high degree of plasticity, which results in hypertrophy and loss of contractile abilities. The data collectively indicate important roles of inconspicuous testicular peritubular cells in human male fertility and infertility.Reproduction (2013) 145 R107-R116

Testicular defense systems: immune privilege and innate immunity

“…MPCs secrete numerous cytokines, including pro-inflammatory and anti-inflammatory factors, under physiological and inflammatory conditions. 22,68 The functions of MPCs that are involved in regulating testicular immunity are worthy of further investigation.…”

Cyclooxygenase and prostaglandins in somatic cell populations of the testis

“…For instance, in rodents, the tubular wall is composed of a single cell layer and a tiny extracellular matrix. However, in the human testis, the seminiferous tubule wall is composed of the following components: an internal acellular basal membrane adjacent to the germinal epithelium containing collagen fibers, laminin, glycoproteins, and hyaluronic acid; a middle cellular zone made of spindle-shaped and contractile cells (called myoid cells or myofibroblasts); and an external cellular zone consisting of collagen-producing fibroblasts (Pop et al 2011, Mayerhofer 2013. Disturbances in testicular function and decreased or no spermatogenic activity are associated with a thickening of the seminiferous tubule wall, which becomes fibrotically remodeled.…”

“…Disturbances in testicular function and decreased or no spermatogenic activity are associated with a thickening of the seminiferous tubule wall, which becomes fibrotically remodeled. Fibroblasts, together with smooth muscle cells, mediate tissue fibrosis and collagen deposition (Mayerhofer 2013). This frequent change is observed irrespective of the causes of male infertility and is regarded as a hallmark of male infertility (Frungieri et al 2002a, Weinbauer et al 2010.…”

“…Human testicular peritubular cells were isolated from very small testicular tissue samples from adult patients with obstructive azoospermia but normal spermatogenesis (HTPCs), as well as from biopsies of men with non-obstructive azoospermia, impaired spermatogenesis, and testicular fibrosis (HTPCFs) (Albrecht et al 2006, Schell et al 2008, Spinnler et al 2010, Mayerhofer 2013.…”

Testis peritubular myoid cells increase their motility and express matrix‐metalloproteinase 9 (MMP‐9) after interaction with embryonal carcinoma cells

“…In addition to their structural function, these cells behave as active agents in the regulation of testicular homeostasis, through the secretion of different factors, including ECM components (Ailenberg et al, 1988;Dıez-Torre et al, 2011). For instance, it has been shown that these smooth muscle-like cells play important roles in human male fertility, in the paracrine regulation of the male gonad and in the establishment of the spermatogonial stem cell (SSC) niche (Albrecht et al, 2006;Mayerhofer, 2013;Flenkenthaler et al, 2014). Nevertheless, the potential of PTCs as a part of the TGCT together with the tumor reactive stroma, to be a source of proinvasive factors, remains unknown.…”