title: Glial cell line-derived neurotrophic factor is constitutively produced by human testicular peritubular cells and may contribute to the spermatogonial stem cell niche in man.
abstract: 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-alpha (TNF-alpha) 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-alpha1. 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-alpha and tryptase. Importantly, peritubular cells express GDNF and constitutively released GDNF into the medium in comparably high amounts. TNF-alpha 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.
authors.affiliation: Institute for Cell Biology, Anatomy and Center for Integrated Protein Science Munich (CIPSM), Ludwig Maximilian University, Biedersteiner Strasse 29, D-80802 Munich, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Spinnler
authors.forename: F M
authors.initials: FM
authors.lastname: Köhn
authors.forename: U
authors.initials: U
authors.lastname: Schwarzer
authors.forename: A
authors.initials: A
authors.lastname: Mayerhofer
mesh_terms: D018070:Biological Specimen Banks; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D005355:Fibrosis; D015870:Gene Expression; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007248:Infertility, Male / Q000378:metabolism; D008297:Male; D042282:Microdissection; D009845:Oligospermia / Q000378:metabolism; D009928:Organ Specificity; D012333:RNA, Messenger / Q000378:metabolism; D012671:Seminiferous Tubules / Q000378:metabolism / Q000473:pathology; D013093:Spermatogonia / Q000378:metabolism*; D055153:Stem Cell Niche / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D053802:Tryptases / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: C495039:GDNF protein, human; C494987:GFRA1 protein, human; D051100:Glial Cell Line-Derived Neurotrophic Factor; D051097:Glial Cell Line-Derived Neurotrophic Factor Receptors; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D000242:Cyclic AMP; D053802:Tryptases