[Effects of transforming growth factor beta1 on the proliferation and type I collagen expression at different differential rat hepatic stellate cells]

Abstract

Objectives: To investigate the biological responses of cultured hepatic stellate cells (HSC) at different differentiated stages on exotic transforming growth factor (TGF-beta1).

Methods: HSC was isolated from rat and primarily cultured in uncoated disc for 1 d, 4 d and 7 d, when the cells were at quiescent, intermediate activated and full activated stages respectively. The cells were incubated with 10 pmol/L to 500 pmol/L TGF-beta1 for 24 h, cell proliferation was measured with [3H] TdR incorporation, alpha-smooth muscle actin (alpha-SMA) and type I collagen protein were assayed with Western blot, and total protein secretion in the culture supernatant was analyzed by [3H] proline pulse and collagenase digestion. HSC was treated with 100 pmol/L TGF- beta1 for 15 min to 90 min, and type I pro-collagen mRNA level was assayed by Northern blot.

Results: TGF-beta1 remarkably inhibited d1 HSC proliferation, the percentage of [3H] TdR incorporation at 10 pmol/L to 500 pmol/L TGF-beta1 was 52.8% to 16.8% of the control, q value was 5.44 to 10.37 and P<0.01 vs control. But TGF-beta1 had no influence on d4 and d7 HSC. As the cells cultivation prolonged and activated, the basal levels of alpha-SMA, type I collagen and gene expression increased gradually. TGF-beta1 increased the above protein and gene expression. The basal and TGF-beta1 stimulated total protein secretion levels at d1-d7 HSC were 804+/-274 vs 1200+/-708; 2966+/-1701 vs 6160+/-1123, t=3.84, P<0.01; 2580+/-767 vs 4583+/-1467, t=2.96, P<0.05. While d4 HSC showed the strongest response of total protein secretion and alpha-SMA expression.

Conclusions: TGF-beta1 remarkably inhibited quiescent HSC proliferation, and promoted HSC collagen production at both quiescent and activated HSC. Intermediate HSC had the strongest response to TGF-beta1, while activated HSC lost the response to TGF-beta1 inhibitory growth, and TGF-beta1 exerted divergent actions on HSC as the cells activated.