EARLY GENES INDUCED IN HEPATIC STELLATE CELLS DURING WOUND-HEALING

Activation of mesenchymal cells is a central event in the wound healin g response of most tissues. In liver, the mesenchymal element responsi ble for organ fibrosis is the hepatic stellate cell(HSC) (formerly kno wn as lipocyte or Ito cell). The phenotypic cascade of stellate cell a ctivation in liver fibrosis has been well documented and involves both marked morphologic changes and upregulation of several functional com ponents including extracellular matrix, cytokine receptors, contractil e filaments and metalloproteinases. However, the genetic regulation of stellate cell activation is poorly understood. In an attempt to clone genes that are involved in the regulation of HSC activation we have c ombined cDNA library amplification by PCR with subtraction hybridizati on/differential screening, and have successfully identified genes indu ced in vivo during early stellate cell activation in a rat model of li ver fibrosis. The subtracted cDNA library comprised less than 100 uniq ue sequences. Of these, 13 clones with sizes ranging from 322 to 745 w ere sequenced and characterized. Gene induction in HSCs was monitored by RNAse protection assay during early liver injury induced by the hep atotoxin CCl4,. The sequenced cDNAs corresponding to the known genes i ncluded type II transforming growth factor beta receptor, glutathione peroxidase I, transferrin and several clones encoding cellular retrotr ansposons, whose expression was not previously identified in non-paren chymal liver cells. In addition, one partial cDNA predicted a zinc-fin ger motif, suggesting a possible role of a novel transcriptional regul ator. Our approach represents a valuable strategy for clarifying in vi vo regulatory mechanisms of mesenchymal cell activation in wound heali ng. (C) 1997 Elsevier Science B.V.