BACKGROUND

Testicular peritubular cells form an ill-characterized cellular compartment of the human testis, which forms a border with Sertoli cells and spermatogonial stem cells (SSCs). A recently developed culture method has identified parts of the secretory repertoire of human testicular peritubular cells (HTPCs), which includes nerve growth factor. Whether peritubular cells produce glial cell line-derived neurotrophic factor (GDNF) and may thus contribute to the stem cell niche is not known.

METHODS

We studied GDNF production in isolated peritubular cells from men with normal spermatogenesis (HTPCs) and impaired spermatogenesis and testicular fibrosis (HTPC-Fs). Human testicular biopsies and peritubular cells in culture were evaluated using immunohistochemistry, laser microdissection (LMD), RT–PCR and measurement of GDNF and cAMP by enzyme-linked immunosorbent assay. We also tested whether GDNF production is regulated by tumour necrosis factor- (TNF-) or tryptase, the products of mast cells or macrophages.

RESULTS

Peritubular wall cells are in close proximity to cells expressing the GDNF family co-receptor-1. GDNF mRNA was detected in LMD samples of the peritubular and tubular but not interstitial compartments. HTPCs and HTPC-Fs lack FSH- and LH-receptors but express receptors for TNF- and tryptase. Importantly, peritubular cells express GDNF and constitutively released GDNF into the medium in comparably high amounts. TNF- and tryptase had no effect on the secretion of GDNF by HTPCs or HTPC-Fs.

CONCLUSIONS

Peritubular cells in testes of normal and sub-/infertile men produce GDNF and are likely constitutive contributors of the SSC niche in the human testis.