Yuki Bekki1, Tomoharu Yoshizumi1, Shinji Shimoda2, Shinji Itoh1, Norifumi Harimoto1, Toru Ikegami1, Atsushi Kuno3, Hisashi Narimatsu3, Ken Shirabe4, Yoshihiko Maehara1. 1. Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan. 2. Department of Medicine and Biosystemic Science, Graduate School of Medical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan. 3. Research Center for Medical Glycoscience (RCMG), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan. 4. Department of Hepatobiliary and Pancreatic Surgery, Gunma University, Maebashi, Gunma, Japan.
Abstract
BACKGROUND AND AIM: Hepatic stellate cells (HSCs) play a central role in hepatic fibrosis and are regulated by Kupffer cells (KCs). Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA+ -M2BP) was recently identified as a serum marker for hepatic fibrosis. Although WFA+ -M2BP was identified as a ligand of Mac-2, the function of WFA+ -M2BP in hepatic fibrosis remains unclear. METHODS: Liver specimens were obtained from five patients with cirrhosis, five with chronic hepatitis, and five without hepatic fibrosis. WFA+ -M2BP kinetics were evaluated histologically and in subpopulations of liver cells such as HSCs, KCs, endothelial cells, biliary epithelial cells, and hepatocytes in in vitro culture. The function of WFA+ -M2BP in activated HSCs was evaluated using immunoblot analysis. RESULTS: Numbers of WFA+ -M2BP-positive cells in liver tissues increased with fibrosis stage. There were significant differences in WFA+ -M2BP levels between fibrosis stages F0 and F1-2 (P = 0.012) and between fibrosis stages F1-2 and F3-4 (P < 0.001). HSCs were the source of WFA+ -M2BP secretion in in vitro cultures of liver cells, as determined by sandwich immunoassay. Cells of the human HSC line LX-2 also secreted WFA+ -M2BP. Histologically, tissue sections showed that WFA+ -M2BP was located in Mac-2-expressing KCs. In vitro assays showed that exogenous WFA+ -M2BP stimulation enhanced Mac-2 expression in KCs and that HSCs co-cultured with KCs increased α-smooth muscle actin expression. Finally, Mac-2-depleted KCs with short interfering RNA had reduced α-smooth muscle actin expression following co-culturing with HSCs. CONCLUSIONS: WFA+ -M2BP from HSCs induces Mac-2 expression in KCs, which in turn activates HSCs to be fibrogenic.
BACKGROUND AND AIM: Hepatic stellate cells (HSCs) play a central role in hepatic fibrosis and are regulated by Kupffer cells (KCs). Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA+ -M2BP) was recently identified as a serum marker for hepatic fibrosis. Although WFA+ -M2BP was identified as a ligand of Mac-2, the function of WFA+ -M2BP in hepatic fibrosis remains unclear. METHODS: Liver specimens were obtained from five patients with cirrhosis, five with chronic hepatitis, and five without hepatic fibrosis. WFA+ -M2BP kinetics were evaluated histologically and in subpopulations of liver cells such as HSCs, KCs, endothelial cells, biliary epithelial cells, and hepatocytes in in vitro culture. The function of WFA+ -M2BP in activated HSCs was evaluated using immunoblot analysis. RESULTS: Numbers of WFA+ -M2BP-positive cells in liver tissues increased with fibrosis stage. There were significant differences in WFA+ -M2BP levels between fibrosis stages F0 and F1-2 (P = 0.012) and between fibrosis stages F1-2 and F3-4 (P < 0.001). HSCs were the source of WFA+ -M2BP secretion in in vitro cultures of liver cells, as determined by sandwich immunoassay. Cells of the humanHSC line LX-2 also secreted WFA+ -M2BP. Histologically, tissue sections showed that WFA+ -M2BP was located in Mac-2-expressing KCs. In vitro assays showed that exogenous WFA+ -M2BP stimulation enhanced Mac-2 expression in KCs and that HSCs co-cultured with KCs increased α-smooth muscle actin expression. Finally, Mac-2-depleted KCs with short interfering RNA had reduced α-smooth muscle actin expression following co-culturing with HSCs. CONCLUSIONS: WFA+ -M2BP from HSCs induces Mac-2 expression in KCs, which in turn activates HSCs to be fibrogenic.