New Strategy for Liver Failure by Regulating Hepatic Extracellular Matrix

(1)肝功能衰竭患者血清IV型胶原水平及肝组织学改变的意义：对慢性肝损伤患者和非慢性肝损伤患者围手术期进行IV型胶原检测，以探讨IV型胶原在肝脏急性应激反应中的变化及其对肝切除手术风险的预测价值。肝硬变患者血清IV型胶原水平明显升高。在术后发生肝功能衰竭的患者中，手术前和术后的血清IV型胶原水平均显著高于无并发症的患者。尸检发现肝脏有明显的IV型胶原沉积在Disse间隙。在几项术前肝功能测试中，IV型胶原被发现是术后肝功能衰竭的独立危险因素。因此，围手术期血清IV型co…的测定肝星状细胞与肝细胞相互作用的体外研究：利用共培养模型和条件培养液观察星状细胞对肝细胞增殖和白蛋白合成的影响。当与星状细胞共培养时，即使在无血清条件下，肝细胞的DNA合成也是增强的。HGF浓度低于6 ng/ml的条件培养液可促进肝细胞的增殖。肝细胞与星状细胞之间的细胞接触可能是肝细胞DNA合成的一个额外因素。白蛋白产量不受共培养的影响。另一方面，即使在无血清状态下，与肝细胞共培养也能促进星状细胞的增殖。肝细胞条件培养液和共培养可刺激星状细胞DNA合成。抗IGF-1中和抗体可部分减弱条件培养液的促有丝分裂活性，提示肝细胞和星状细胞的DNA合成可能受单个细胞来源的某些因素的调节，肝细胞和星状细胞之间的细胞接触可能在其增殖和分化中起作用。(3)N-乙酰半胱氨酸抑制肝星状细胞的增殖和肝纤维化：N-乙酰半胱氨酸呈剂量依赖性地阻断原代培养的肝星状细胞由血小板衍生生长因子诱导的DNA合成和信号转导，包括MAPK和Akt。体外降解实验表明，N-乙酰-L-半胱氨酸等还原剂可增强组织蛋白酶B的催化活性，并触发细胞外血小板衍生生长因子受体的蛋白分解，从而导致细胞对血小板衍生生长因子-B的脱敏。此外，免疫印迹显示肝星状细胞分泌成熟的组织蛋白酶B进入培养基内，而血管平滑肌细胞不分泌组织蛋白酶B。较少

(1) SIGNIFICANCE OF SERUM LEVELS OF TYPE IV COLLAGEN AND MICROSCOPICAL CHANGE IN LIVER TISSUE IN PATIENT WITH LIVER FAILURE : Type IV collagen, one of serum markers for hepatic fibrosis, was measured perioperatively in patients with and without chronic liver damage in order to investigate whether this parameter changes responding to acute stress to the liver and can predict surgical risk of hepatic resection. The serum type IV collagen level was significantly elevated in cases with liver cirrhosis. In cases with postoperative liver failure, serum type IV collagen levels were significantly higher both pre-and postoperatively as compared to those of uneventful cases. Microscopic findings of the liver obtained from autopsy indicated marked amount of deposition of type IV collagem in Disse space. Among several preoperative liver function tests, type IV collagen revealed to be an independent risk factor for postoperative liver failure. Thus, perioperative measurement of the serum type IV co … More llagen levels seemed to be useful for the prediction of the risk of hepatic resection in cases with chronic liver damage.(2)INVESTIGATION OF INTERACTION WITH HEPATOCYTES AND STELLATE CELLS USING IN VITRO CO-CULTURE SYSTEM : Effect of stellate cells on proliferation and albumin synthesis of hepatocytes was investigated using co-culture models and conditioned mediums. When co-cultured with stellate cells, hepatocyte DNA synthesis was enhanced even under a serum-free condition. Conditioned medium, in which HGF concentration was below 6 ng/ml, stimulated the proliferation of hepatocytes. Cell contact between hepatocytes and stellate cells may be an additional factor for DNA synthesis of hepatocytes. Albumin production was not affected by co-culture. On the other hand, stellate cell proliferation was enhanced by co-culture with hepatocytes even under a serum-free status. Conditioned medium of hepatocytes and co-culture stimulated DNA synthesis of stellate cells. Such a mitogenic activity of conditioned medium was partially attenuated by anti-IGF-1 neutralizing antibody Thus, DNA synthesis of hepatocytes and stellate cells may be regulated by some factors derived from individual cells and cell-cell contact between hepatocytes and stellate cells may play a role in their proliferation and differentiation.(3)ACTION OF NAC (N-ACETYL CYSTEINE) TO SUPPRESS PROLIFERATION OF HEPATIC STELLATE CELL AND LIVER FIBROSIS : N-acetyl-L-cysteine dose-dependently blocked platelet-derived growth factor-induced DNA synthesis and signal transduction, including MAPK and Akt, inprimary-cultured hepatic stellate cell. In vitro degradation assay with various protease inhibitors showed that reducing agents, including N-acetyl-L-cysteine, enhanced the catalytical activity of cathepsin B and triggered extracellular proteolysis of platelet-derived growth factor receptor, thereby leading to desensitization of the cell to platelet-derived growth factor-BB.Moreover, western blot showed that hepatic stellate cell secreted mature-cathepsin B into the culture medium, while vascular smooth muscle cell did not secrete cathepsin B.This mechanism was demonstrated in in vivo liver fibrosis models. Less