To study the dynamic changes of alpha 1 (I), alpha 1 (III) and alpha I (IV) procollagen mRNA and collagen-producing cells during CCl4 induced SD rat liver fibrogenesis (20 weeks).The investigations were performed using Northern blot analysis, in situ hybridization and immunohistochemical techniques.The increased expression of alpha 1 (III) procollagen mRNA during fibrogenesis by Northern blot analysis was the most predominant among the three mRNAs studied. However, the increase of alpha 1 (IV) procollagen mRNA expression occurred earlier, while the expression of alpha 1 (I) mRNA did not increase until the middle stage of the experiment. Desmin positive and/or smooth muscle actin positive Ito cells and myofibroblasts (MFs) in and around the necrotic areas expressed alpha 1 (I), alpha 1 (III) and alpha 1 (IV) procollagen mRNA signals detected by in situ hybridization during the early stage of the experiment. All the three procollagen mRNAs were mostly localized in fibroblasts (Fbs) and MFs in the septa during the mid and late stages of fibrosis.Fbs and MFs were considered as important Col I, Col III and Col IV producing cells in liver fibrosis. Sinusoid endothelia were involved in Col IV synthesis in the fibrotic liver.
The study was designed to study the role of fibronectin (FN) receptor alpha 5 beta 1 in liver fibrogenesis.Northern blot analysis and immunohistochemical techniques were used to observe the in vivo and in vitro changes in the expression of FN and its receptor alpha 5 beta 1 in CCl4 induced rat liver fibrosis in Ito cells.(1) alpha 5 beta 1 was mainly detected in the endothelia and some of the desmin (DM) positive cells (Ito cells) of the sinusoids in normal rat liver. The expression of alpha 5 beta 1 of DM positive cells in the experimental groups was enhanced and reached their peaks by the 10th week. The changes in FN was similar to that of alpha 5 beta 1; (2) The expression of FN, alpha 5 and beta 1 mRNA of the liver in the experimental groups detected by Northern blot analysis was increased and reached their peaks by the 6th week. The content of these mRNAs of the cultured Ito cells isolated from the experimental group was increased more than that from normal liver specimens.Ito cells expressed FN receptor alpha 5 beta 1. The activation of Ito cells resulted in the increase of the expression of the three mRNAs during fibrogenesis. It is suggested that the detection of gene transcription of FN and its receptor mRNAs by Northern blot analysis could reveal the activation and proliferation of Ito cells and thereby provides a sensitive signal of liver fibrosis.
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