Prostatic ductal system in rats: changes in regional distribution of extracellular matrix proteins during...

The extracellular matrix (ECM) is an intricate network composed of an array of molecules that play an integral role in the regulation of cell function, differentiation, and tissue-specific gene expression in various epithelia. In the present study, we examined the distribution of collagen type IV and laminin along the rat ventral prostatic duct before and after castration.

Mature Sprague-Dawley rats were castrated and their prostates processed for immunocytochemistry of ECM proteins, laminin, and collagen type IV. Tissue sections were also processed for apoptosis staining, using the 3' end-labeling technique. To examine the effect of ECM proteins on epithelial growth, rat ventral epithelial cells were cultured on ECM-coated surfaces.

In the intact rat, laminin was localized in the basement membrane along all regions of the ventral prostate ductal system. Collagen type IV was found to be distributed evenly in the basement membrane of the distal and intermediate regions but was absent or poorly organized in the proximal region, where apoptosis in the epithelium occurs at a high rate. In the regressing prostate after castration, there was a shift in apoptosis from the proximal region to the distal intermediate regions of the prostatic duct. Associated with the shift was a remodeling of basement membrane proteins due to the specific loss of collagen type IV in the distal and intermediate regions. Collagen type IV reappeared underneath the epithelium 7 days after castration, when apoptosis in the epithelium stopped. In vitro, collagen type IV enhanced the growth of ventral prostatic epithelial cells, as assessed by cell number.

Collagen basement membrane type IV mediates growth of rat ventral prostate epithelium, and its loss during tissue remodeling after castration is associated with cell death.