IDENTIFICATION OF CONNECTIVE-TISSUE GENE TRANSCRIPTS IN FRESHLY ISOLATED PARENCHYMAL, ENDOTHELIAL, KUPFFER AND FAT-STORING CELLS BY NORTHERN HYBRIDIZATION ANALYSIS

The aim of the present study was to identify the cell types that expre ss collagen alpha1(I), alpha1(III) and alpha1(IV), fibronectin and lam inin B1 genes in normal rat liver. Parenchymal, sinusoidal endothelial , Kupffer and fat-storing (Ito) cells were isolated and purified. Tota l RNA of the freshly isolated cells was subjected to Northern hybridiz ation analysis. We also compared the steady state levels of specific m RNAs in freshly isolated fat-storing cells to the levels in myofibrobl ast-like cells obtained from purified fat-storing cells cultured for t wo passages. The average purity of each cell preparation, and the perc entage of contaminating cells, were determined by transmission electro n microscopy and by examining the presence of vitamin A-autofluorescen t cells. Fibronectin and collagen alpha1(III) mRNAs were detected in t otal RNA of purified parenchymal cells. In poly(A)+ enriched RNA, smal l amounts of collagen alpha1(I) mRNA were also present. In total RNA o f freshly isolated fat-storing cells, collagen alpha1(III), alpha1(IV) , and laminin B1 transcripts were found, whereas collagen alpha1(I) an d fibronectin mRNAs were not detected. Cultured fat-storing cells, how ever, did contain high levels of collagen alpha1(I) and fibronectin mR NAs. The molecular size of the latter transcript was larger than the f ibronectin transcript found in parenchymal cells and the whole liver. Endothelial cells contained small amounts of alpha1(IV) mRNA. Kupffer cells,did not contain the investigated transcripts. We conclude that n ormal parenchymal, fat-storing and endothelial cells each express a ty pical pattern of connective tissue molecules. When fat-storing cells a re allowed to differentiate into myofibroblast-like cells, they expres s high levels of collagen alpha1(I) and fibronectin mRNAs, in addition to collagen alpha1(III) and alpha1(IV), and laminin B1 chain mRNAs.