In vitro fusion of human inguinal hernia with associated epithelial transformation

The processus vaginalis (PV) is a peritoneal diverticulum which forms to al low descent of the fetal testis to the scrotum. During human development fu sion and obliteration of the PV often fails to occur with the result that i nguinal hernias are the most prevalent congenital abnormality requiring sur gery in childhood. Androgen is proposed to regulate testicular descent via the genitofemoral nerve which releases the neuropeptide calcitonin gene-rel ated peptide (CGRP). It is possible that subsequent fusion of the PV and ti ssue remodelling following descent is indirectly controlled by androgen via CGRP action. An organ culture assay was developed to assess fusion of the PV taken from inguinal herniotomy in infants. Fusion was induced in vitro b y CGRP but not by CGRP 8-37, CGRP 27-37 or dihydrotestosterone in equimolar concentrations. Fusion was accompanied by transformation of the epithelium , as shown by staining of intermediate filament proteins, cytokeratin and v imentin. Localization studies for CGRP receptors on 25 specimens indicated CGRP acts on mesenchymal fibroblasts but not directly on PV epithelium sugg esting an indirect pathway. Hepatocyte growth factor/scatter factor was fou nd to induce fusion of PV and may be involved as an intermediate molecule i n the fusion cascade. This study represents the first approach to understan ding the humoral control and underlying mechanism by which the PV fuses. Co pyright (C) 2000 S. Karger AG, Basel.