Immunophenotypical characterization of contractile cells in caput epididymidis of men affected by congenital or post-inflammatory obstructive azoospermia.

Myoid cells of the human caput epididymidis are replaced by large cells with ultrastructural features of smooth muscle cells (SMC) in chronic obstruction of the male genital tract. To evaluate whether these cellular changes are associated with different functional phenotypes we analysed the immunohistochemical expression of myosin heavy chain isoforms and of extracellular matrix (EM) components in the human caput epididymidis contractile cells in normal and in obstructed epididymides. Normal caput epididymidis myoid cells expressed a scattered immunostaining for SM2, marker of differentiated contractile SMC, while no staining was detected for SMemb (the non-muscle-type myosin heavy chain isoform) and for its transcription factor BTEB2, markers of undifferentiated proliferating SMC. A faint immunoreaction (IR) for EM was observed in the peritubular wall of the normal caput. In the contractile wall of the obstructed caput epididymidis a strong IR was detected for all myosin heavy chain isoforms as well as for collagen type IV and for fibronectin, markers for a secretory function of SMC. These findings, unknown in other models of SMC pathophysiology, suggest that myoid cells resume the molecular machinery of both mature SMC and of differentiating/secretory cells in the chronic obstruction of the human caput. Contractile cells of the epididymal duct represent a unique model to study the plasticity of SMC.