The Effect Of Exogenous IGFBPrP1 On Liver Tissue In Mice

Background:Insulin-like growth factor binding protein-related protein 1(IGFBPrP1) is a soluble secreted protein, Lixin Liu discovered that IGFBPrP1 was a new pathogenic factor in the formation of liver fibrosis. In liver tissue of patients with liver fibrosis and cirrhosis, the expression of IGFBPrP1 was high. HSC could be activated by IGFBPrPl in vitro, The synthesis of ECM was increased by IGFBPrPl. Anti-IGFBPrP1 antibody can decrease the expression of CollagenⅠin the HSC with TGFβ1. Also it can suppresses the progression of hepatic fibrosis through many ways, including inhibiting the activation of HSC and reducing the expressions of CollagenⅠand FN. And it can suppresses the progression of hepatic fibrosis through reducing hepatocyte apoptosis and so on.If IGFBPrP1 as an independent factor directly on the liver tissue in vivo animal will have what effects? Mechanism for what? This study will going to clarify this issue.Objective:To investigate the effect and mechanism of the exogenous IGFBPrP1 on the liver tissue in mice.Methods:Twenty-four male C57BL/6 wild-type mice were randomly divided into three groups: normal control group (n=8), injected with phosphate buffer saline; rmIGFBPrP1 2 weeks group (n=8),injected with rmIGFBPrP1,0.015mg/kg,7 times per week, lasting 2 weeks; rmIGFBPrP1 4 weeks group (n=8),injected with rmIGFBPrP1,0.015mg/kg,7 times per week, lasting 4 weeks. (1) The morphological changes of liver fibrosis were observed with eyes.(2) The morphological changes of the liver tissue were observed with both HE stain and picric acid-Sirius red staining.(3) Examine the expression of CollagenⅢ, transforming growth factor-beta 1(TGFβ1) p-Smad2/3 and Smad3 of the liver tissue by the immunohistochemistry. (4)Examine the expression of IGFBPrPl,fibronectin (FN), CollagenⅠ, TGFβ1, p-Smad2/3 and Smad3 in the liver tissue by Western blot. The relationships of IGFBPrP1 with FN, CollagenⅠ, TGFβ1, p-Smad2/3 and Smad3 were analyzed.Results:(1) The picric acid-Sirius red staining analysis:Exogenous IGFBPrP1 can cause the marked increase of collagen content in rmIGFBPrP1 2 weeks group and rmIGFBPrP1 4 weeks group, the level in 4 weeks group was higher than that in 2 weeks group. (0.45%±0.15% vs 0.21%±0.11%,1.02%±0.33% vs 0.45%±0.15%, P<0.05).(2) The protein expression of CollagenⅢ, TGFβ1, Smad3 and p-Smad2/3 in liver tissues was significantly increased after rmIGFBPrP1 injected in a time-dependent manner by immunohistochemistry (CollagenⅢ:F=221.858, P<0.01; TGFβ1:F=280.571, P<0.01; Smad3:F=292.114, P<0.01; p-Smad2/3:F=114.251, P<0.01).(3) The protein expression of IGFBPrP1,CollagenⅠ, FN, TGFβ1, Smad3 and p-Smad2/3 was gradually increased after rmIGFBPrP1 injecting for 2 weeks and 4 weeks by Western blot (F=20.136,F=6.029,F=17.282, F=7.484,F=20.957,F=87.713, P<0.01). The expression of IGFBPrP1 has positive correlation with that of FN(r=0.890, P<0.01),CollagenⅠ(r=0.921, P<0.01),TGFβ1(r=0.726, P<0.01),Smad3 (r=0.977, P<0.01) and p-Smad2/3 (r=0.809, P<0.01) in liver tissue.Conclusions:(1) Exogenous IGFBPrP1 can cause the excessive deposition of ECM in liver tissue through many ways, including increasing the expressions of CollagenⅠ,Ⅲand FN. It can result in the progression of hepatic fibrosis.(2) The possible mechanism relates to the TGFβ1/Smad3 signal path.