Transforming growth factor-β1 regulates cell growth and causes downregulation of SMemb/non-muscle myosin heavy chain B mRNA in human prostate stromal cells

Abstract

Objectives. SMemb/non-muscle myosin heavy chain B (SMemb/NMMHC-B) is most abundantly expressed in proliferating smooth muscle cells and correlates with phenotypic changes from a contractive to a proliferative type. The stromal cells of the prostate play a crucial role in the regulation of prostatic growth and function. The aim of this study was to investigate the effects of the multifunctional cytokine transforming growth factor-β1 (TGF-β1) on SMemb/NMMHC-B mRNA expression and stromal cell growth. The expression of the SM2 isoform of smooth muscle myosin heavy chain (SMMHC) mRNA was also examined. Material and methods. Primary cultures of prostate stromal cells were established by means of an explant method from eight normal prostates. The effects of TGF-β1 on stromal cell growth were determined by means of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide conversion assay. SMemb/NMMHC-B and SM2 mRNA expression were analyzed quantitatively by means of real-time polymerase chain reaction. Results. In the absence of TGF-β1, cells expressed α-smooth muscle actin and vimentin. After TGF-β1 treatment, the expression of α-smooth muscle actin increased and cells also expressed desmin. TGF-β1 at concentrations of 1.0, 5.0 and 10 ng/ml suppressed cell growth by 72%, 62% and 56%, respectively, downregulated SMemb/NMMHC-B mRNA expression by 71%, 52% and 38%, respectively and upregulated SM2 mRNA expression 2.1-, 3.0- and 5.3-fold, respectively. Conclusions. These results demonstrate that TGF-β1 modulates the smooth muscle cell phenotype from a proliferative to a contractile type and that the inhibitory effects of TGF-β1 on stromal cell growth correlate with downregulation of the SMemb/NMMHC-B gene.

• Human prostate stromal cell culture
• SM2
• SMemb/non-muscle myosin heavy chain B
• transforming growth factor-β1