229. Identification of transforming growth factor beta2 (TGF-β2) and its receptors TGF-βRI and TGF-βRII in the possum (Trichosurus vulpecula) prostate: evidence of seasonal changes

Abstract

Benign Prostatic Hyperplasia is an enlargement of the prostate affecting the ageing male population. The common Brushtail possum (Trichosurus vulpecula) has been identified as a possible model to study factors regulating prostate growth because its prostate grows and regresses seasonally. Transforming growth factor Beta 2 (TGF-β2) is present in human prostatic tissue. In vitro, TGF-β inhibits epithelial cell, but stimulates stromal cell proliferation (Mori et al. 1990). TGF-β2 binds to TGF-β receptor II (TGF-βRII), which then recruits the type 1 receptor (TGF-βRI) (Saez et al. 1998) The aim of this study was to identify any seasonal changes in expression of TGF-β2 and its receptors in the possum prostate. Six wild-caught possums were sacrificed in each of the months of January, March, May, July, September and November. The prostates were divided into a cranial and caudal region and immunohistochemistry and Western Blot analysis performed. In each animal the glandular and periurethral areas of the caudal and cranial prostates were examined separately. Immunohistochemistry identified the presence of TGF-β2 in both the stromal and epithelial cells of the glandular and periurethral areas of the cranial and caudal regions. In the cranial tissue, more immuno-positive stromal cells than epithelial cells were present, whereas in the caudal tissue immuno-reactivity was predominantly localised to the epithelial cells. Analysis of the western blots suggested that TGF-β2 expression was lowest immediately before and during the breeding season (March, May). Both TGF-βRI and TGF-βRII were identified in all regions of the prostate. Furthermore, immunohistochemistry revealed that the receptors were co-localised in the epithelial and stromal cells in all areas. TGF-β2 and its receptors are present in the possum prostate. TGF-β2 localisation varies between the caudal and cranial regions and as predicted from in vitro experiments TGF-β2 expression decreases during prostate growth. (1) Mori H. et al. (1990). The Prostate, 16, 71 - 80. (2) Saez C. et al. (1998). The Prostate, 37, 84 - 90.