Characterization of the urethral plate and the underlying tissue defined by expression of collagen subtypes and microarchitecture in hypospadias

Objectives: In hypospadia patients, the urethral plate and the underlying tissue were previously thought to be the main cause of penile curvature and, because of this, they used to be excised to correct the curvature. Currently, they are preserved as they are not thought to cause penile curvature anymore. The aim of the present histology study was to elucidate the characteristic structure of the tissue beneath the urethral plate. Methods: The experimental group consisted of 27 hypospadiac patients with moderately severe penile curvature, who underwent one‐stage urethroplasty after dividing the urethral plate. Excised tissues were observed under light microscopy and transmission electron microscopy (TEM). Furthermore, the presence of collagen subtypes I, III and IV was examined with immunohistochemical staining and western blotting. Results: Light microscopy showed the existence of many massed and intertwined collagen fibers and vessels that resembled those of the cavernous sinus. TEM showed the existence of many collagen fibers, capillary vessels and other structures. Immunohistochemical staining showed collagen subtype I in the interfascicular space and collagen fibers were densely stained. Collagen subtype IV was found in the basement membrane of vessels, but collagen subtype III was not detected. The same results were obtained by western blotting. Conclusions: The tissue beneath the urethral plate was considered to originate from the corpus spongiosum penis. The distribution of collagen subtypes suggests that the presence of the tissue might affect ventral penile curvature. Long‐term follow up is required after one‐stage hypospadias repair with preservation of the urethral plate and the underlying tissue.