ABSTRACT
<p><b>OBJECTIVE</b>To investigate the role of activated hepatocyte growth factor (HGF) in apoptosis of hepatic stellate cells (HSCs) and in modulating the Rho signaling pathway.</p><p><b>METHODS</b>HSCs were divided into the following groups: blank control, consisting of HSCs without treatment; two treatment controls, consisting of HSCs exposed to exogenous HGF at 50 ng/ml and HSCs exposed to exogenous HGF activator (HGFA) at 70 ng/ml; three experimental groups, consisting of HSCs exposed to both exogenous HGF and HGFA, HSCs pre-incubated with the HGF inhibitor c-met at 500 ng/ml for 6 hours and then exposed to exogenous HGF and HGFA, and HSCs pre-incubated with the Rho pathway inhibitor Y-27632 at 10 ng/ml and then exposed to exogenous HGF and HGFA. Activation status of the cultured HSCs was determined by change in expression of alpha-smooth muscle actin (SMA). The optimal intervention concentration of Y-27632 was determined by MTT assay. The apoptotic status of HSCs was determined by flow cytometry. Expression of the HGF-alpha chain was detected by immunofluorescence. The expression of RhoA was evaluated by PCR (for mRNA) and by immunohistochemical staining and Western blot analysis (for protein).</p><p><b>RESULTS</b>Exposure to 10 mumol/L Y-27632 led to obvious growth inhibition of HGF + HGFA-induced HSCs, compared with the other concentrations tested (P less than 0.05). HGF + HGFA induced the expression of the HGF-alpha chain in a time-dependent manner (P less than 0.01); however, the increases in expression of HGF-alpha chain induced by HGF alone and HGFA alone were not significantly different from the level in the blank controls (P more than 0.05). Exposure to HGF alone and HGFA alone led to a time-dependent increase in apoptosis (24 h, 48 h, 72 h) but exposure to HGF + HGFA led to the highest levels of apoptosis (P less than 0.05). Exposure to HGF + HGFA led to a time-dependent decrease in RhoA mRNA and protein expression (P less than 0.01).</p><p><b>CONCLUSION</b>Activation of hepatocyte growth factor promotes apoptosis of hepatic stellate cells by suppressing RhoA expression and down-regulating the Rho signaling pathway.</p>
ABSTRACT
<p><b>OBJECTIVE</b>To determine whether apoptosis is induced in rat hepatic stellate cells (HSCs) in response to activation of the hepatocyte growth factor (HGF) by hepatocyte growth factor activator (HGFA) by using a co-culture system of bone marrow mesenchymal stem cells (BMSCs) and HSCs.</p><p><b>METHODS</b>In this study, cells were divided into the following five groups: HSC control group: HSCs co-cultured with fibroblast cells; HSCs blank group: HSCs cultured alone; BMSCs blank group: BMSCs cultured alone; Experimental group: BMSCs + HSCs; HGFA intervention group: HSCs treated with 70 ng/mL of HGFA. The culture systems were established in culture plates with transwell inserts, and cells were assessed at 24, 48, and 72 h of growth. Dynamic changes in cell morphology were observed under an inverted phase contrast microscope. The surface markers of BMSCs and the apoptosis rate of HSCs were detected by Annexin-V-FITC/propidium iodide (PI). Expression of a-smooth muscle actin (SMA) in HSCs was evaluated by immunohistochemistry. The presence of activated HGF (HGF-a chain) was determined by immunofluorescent staining. HSC proliferation was measured by MTT assay, and the concentrations of HGF and HGFA were quantified by enzyme-linked immunosorbent assay (ELISA).</p><p><b>RESULTS</b>MTT results indicated that treatment with HGF alone had no effect on HSC proliferation rate (vs. HSC blank group, P more than 0.05), but that 24 h treatment with HGFA significantly inhibited the proliferation rate (0.26 ± 0.00 vs. blank group: 0.13 ± 0.04, P = 0.02); moreover, this effect was concentration-dependent. Expression of HGF-a was lower in the experimental group than in the HGFA intervention group at 72 h (37.24 ± 1.03 vs. 40.44 ± 0.77, P = 0.04), and both of these groups had higher expression than the control group at all time points examined (P less than 0.05). The apoptosis rate was consistently higher in the experimental group than in the HGFA intervention group, but most robustly at 72 h (40.77 ± 1.16% vs. 33.35 ± 2.04%, P = 0.00); moreover, the apoptosis rate was significantly higher than that in the control group at all time points examined (P less than 0.01). The concentration of HGF in the experimental group and the HGFA intervention group showed a time-dependent reduction, and was consistently lower than that in the HSCs control group (P less than 0.05). Finally, the concentration of HGFA was higher in the experimental group than in the blank group at all time points examined (P less than 0.05).</p><p><b>CONCLUSION</b>The BMSC-HSC co-culture system can promote secretion of HGFA from HSCs and HGF activation, thereby inducing apoptosis of HSCs.</p>