R. Gander, G. Untergasser, H. Rumpold, E. Plas, L. Tadic, P. Berger

Previous reports emphasize that oxidative stress-induced premature senescence (SIPS) of human diploid fibroblasts (HDFs) is mainly triggered by transforming growth factor beta 1 (TGF-b1). In the human prostate TGF-b1 mediates the differentiation of fibroblasts to myofibroblasts within a gradual process leading to a reactive stroma that favours epithelial cell tumorigenesis. In this study, we wanted to elucidate the role of oxidative stress via in vitro application of tert-butylhydroperoxide (t-BHP) and recombiant TGF-b1 on proliferation, differentiation and senescence of primary isolated human prostatic stromal fibroblasts (PrSC). SIPS was evaluated by SA-beta-galactosidase (SA-b-gal) staining after 3 days of TGF-b1 and t-BHP treatment. Moreover, stromal differentiation markers (SMC-a-actin, calponin, vimentin, JM-27), cell cycle regulators (p53, p27KIP1, p21Cip1, p16ink4A, p15ink4B, Id-1) and senescence associated genes (IGFBP-3, dkk3, PTHrP) were evaluated by quantitative PCR, western blot analysis and immunofluorescence. Neither TGF-b1 nor t-BHP treatment significantly induced SA-b-gal, p16inK4A or a terminal irreversible growth arrest in PrSC. t-BHP led to a loss of proliferative activity, induction of p21Cip1, but no signs of differentiation into myofibroblast. In contrast, TGF-b1 stimulation was responsible for growth arrest by induction of p15ink4B and IGFBP-3 as well as down-regulation of Id-1, and induced differentiation into myofibroblasts by increased expression levels of calponin, SMC-a-actin tenascin and JM-27.

Conclusive, oxidative stress did not support transdifferentiation of PrSC and thus tissue-remodelling in favour to reactive stroma. Moreover, TGF-b1, a presumable executor molecule of oxidative stress, acted completly distinct by supporting myofibroblast differentiation, reactive stroma and expression of the benign prostatic hyperplasia marker JM-27 in PrSC.

Keywords (Optional): 
cellular senescence
oxidative stress
prostate fibroblasts