Context: Fibrotic remodeling, especially of the tubule wall, in testes of infertile men is common, but reasons or consequences of these striking changes are not known. Based on cell culture and ex vivo studies, we previously suggested that mast cells via their products tryptase and histamine are involved in the development of fibrosis. However, studies in a relevant human testicular model are required to further test this hypothesis and the mechanisms of testicular fibrosis in general.

Objective: Isolation, culture and characterization of adult human testicular peritubular cells.

Patients and interventions: Peritubular cells were obtained from biopsies of men suffering from obstructive azoospermia (n = 8) and varicocele (n = 2), but displaying normal spermatogenesis.

Results: Explant cultures were obtained from all biopsies. Immunostaining of the cultured cells and corresponding paraffin embedded tissues with antibodies against markers of fibroblasts (CD90/Thy-1) and smooth muscle cells (-smooth muscle actin) clearly proved their origin from the peritubular region. These cells displayed morphological features of myo-fibroblasts and gene array analyses, as well as immunohistochemistry, revealed the predominant expression of extracellular matrix genes and genes coding for basement membrane components. The cultured cells retain receptors for the major mast cell products histamine (H1) and tryptase (PAR2). The addition of histamine (100 µM) and of the PAR2 agonist peptide SLIGKV (10 µM) resulted in a transient increase in intracellular calcium levels, confirming the functionality of the receptors.

Conclusions: We conclude that human peritubular cells are a novel model for the investigation of paracrine, including mast cell initiated, interactions in the human testis which will allow to study fibrotic processes underlying male idiopathic infertility.