| Research Abstract |
Hepatic stellate cells (HSCs) exhibited a marked change in morphology depending on the extracellular matrix (ECM) component as a substratum, and HSCs were altered to elongate many cellular processes, as seen in vivo, by the culturing using interstirial collagen gel. The results from this study revealed that the process elongation was induced by cell surface integrin binding to ECM components, followed by various intracellular signaling and finally cytoskeleton, particularly, microtubule assembly. As previously reported by Senoo et al., HSCs displayed an alteration not only in morphology, but also in proliferation and collagen synthesis/secretion. The results from gelatin zymography in this study further demonstrated that the conditioned medium from HSC culture on type I collagen gel but not on polystyrene surface and on Matrigel contained an activated form of matrix metalloproteinase (MMP)-2, However, the culture on type I collagen gel also indicated the expression of tissue inhibitor of matrix metalloprotease (TIMP)-2, as detected by reverse transcriptase-polymerase chain reaction (RT-PCR), suggesting the suppression of the activated form of MMP-2. Fluorescence immunostaining and in situ zymography further indicated the presence of MMP- 1 proteins and their activities in the culture on type I collagen gel. Taken together, these results suggest a complicated regulatory mechanism at transcriptional level or at translational/posttranslational stages for reorganization of ECM components such as the basement membrane containing type IV collagen or interstitial matrix components including type I collagen. HSC culture system using various ECM components is, therefore, useful to investigate the mechanism of reorganization of ECM in the liver tissue, and further to explore the possibility to ameliorate liver fibrosis by the control of synthesis and secretion of ECM components including collagen and of MMP expression.
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