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.