Subcutaneous transplantation promotes organ formation of the fetal rat urogenital sinus

The aim of this study is to develop a novel experimental model of the subcutaneous transplantation of fetal urogenital sinus (UGS) into normal and castrated adult male rats for the pathophysiological investigation of the normal and developing prostate. Fetal UGS obtained from 20-day-old male rat embryos was subcutaneously transplanted into 7-week-old normal and castrated male rats. We observed the growth pattern, histopathological characteristics and immunohistochemical localization of cytokeratin 5 (CK 5), cytokeratin 8 (CK 8) and androgen receptor (AR) in the transplanted tissues. Almost all of the transplanted UGS organs gradually increased in weight over time in the non-castrated recipient animals, and the histopathological observations and immunohistochemical analysis of CK 5 and CK 8 revealed that the morphological changes in the tissues were in accordance with the features of normal prostate development. The histological characteristics included glandular epithelial dominant and stromal dominant area, with an increase in the glandular epithelial dominant areas over time and resemblance among a portion of the transplanted tissues within a certain period during the developmental course to the histopathology of human benign prostatic hyperplasia (BPH). The effects of androgens and resemblance in the immunohistochemical localization pattern changes in AR to that observed in the normal differentiating rat prostate were also noted. We conclude that the subcutaneous space provides an adequate microenvironment for UGS growth.