The hepatic stellate cell (HSC), following a fibrogenic stim-The hepatic stellate cell (HSC), following a fibrogenic ulus, undergoes an activation process in which changes occur stimulus, is transformed from a quiescent to an actiin cellular morphology, cellular metabolism, and in the patvated cell. HSC activation results in numerous changes tern of gene expression. These changes include morphological in cellular morphology, cellular metabolism, and in the changes to a myofibroblast-like cell with the appearance of pattern of gene expression. Many of the changes that are smooth muscle a-actin, a loss in cellular retinol stores, and an observed in activated HSCs in animal models of hepatic increase in the rough endoplasmic reticulum. [1][2][3][4][5] In addition, fibrosis are also seen when these cells are activated by activation of HSCs in vivo results in the induction of plateletculturing on plastic. These changes include morphologiderived growth factor b receptors, 6 transforming growth faccal changes to a myofibroblast-like cell with the appeartor b, 7-9 and multiple extracellular matrix proteins, including ance of smooth muscle a-actin, a loss of the retinol proteoglycans and type I collagen. 1,3,[10][11][12] Metabolic changes stores, an increase in the rough endoplasmic reticulum, include an increase in DNA synthesis and in cellular proliferand increases in extracellular matrix production, ination. cluding a dramatic increase in type I collagen. To iden-Many of the morphological and metabolic changes associtify additional genes that are induced or suppressed durated with HSC activation in animal models of fibrosis also ing HSC activation, we used the differential polymerase occur when these cells are grown in culture on plastic. In chain reaction (PCR) display technique. Using this techculture, HSCs show alterations in cellular morphology, innique, we isolated a complementary DNA (cDNA) fragcluding an increase in the appearance of rough endoplasmic ment for the intercellular adhesion molecule 1 (ICAM-1). reticulum, a loss of the retinol stores, and an increase in Northern blotting confirmed that the ICAM-1 messenger the proliferation rate. 13,14 Cultured HSCs also initiate the RNA (mRNA) was expressed in HSCs activated by culsynthesis of smooth muscle a-actin, and the expression of ture, but not in quiescent, freshly isolated HSCs. The new receptors, including the platelet-derived growth factor presence of ICAM-1 protein was demonstrated in culb receptor 6 and transforming growth factor b receptors I and ture-activated HSCs, but not in quiescent cells by West-II. 15 The expression of several extracellular matrix proteins ern blot analysis and immunohistochemical staining. A is increased, including several proteoglycans 16 and type I colfunctional assay was performed, demonstrating that lagen synthesis at both the messenger RNA (mRNA) and lymphocytes will adhere to activated HSCs and that protein levels. 13,14,[17][18][19][20][21][22][23][24][25] treatment of these cells with tumor necrosis factor a Differential polymerase chain reaction (PCR) display 26,27 is (TNF-a) increases lymphocyte adherence. Furthermore, a technique that displays mRNAs from different cell types ICAM-1 mRNA levels were increased in HSCs activated after reverse transcriptase-PCR amplification. This method in rats in vivo after 1 week of bile duct ligation (BDL). has been used successfully to isolate differentially expressed Together, these data indicate that ICAM-1 expression is mRNAs from numerous cell types. [28][29][30][31] We have used the difinduced following HSC activation and that the HSC may ferential PCR display technique to select complementary have a direct role in the transmigration of leukocytes DNAs (cDNAs) that are differentially expressed in quiescent from the hepatic sinusoid to sites of tissue damage durand activated HSCs. ing the inflammatory response in the liver. (HEPATOLOGY In this study, we have isolated a cDNA fragment from acti-1996;24:670-676.)
vated HSCs that corresponds to the rat intercellular adhesion molecule 1 (ICAM-1) mRNA. ICAM-1 belongs to the immunoglobulin superfamily and is expressed on the cell surface. This molecule is believed to contribute to cellular adhesion Abbreviations: HSC, hepatic stellate cell; mRNA, messenger RNA; PCR, polymerase and transmigration of leukocytes through the vascular cell chain reaction; cDNA, complementary DNA; ICAM-1, intercellular adhesion molecule 1; wall via interactions with b2 integrins. ICAM-1 expression BDL, bile duct ligation; PBS, phosphate-buffered saline; SDS, sodium dodecyl sulfate; TNFis increased during inflammatory disease processes in both a, tumor necrosis factor a; RPMI, Roswell Park Memorial Institute; RT, reverse transcripvascular and nonvascular cell types. 32 Adhesion molecules tion; LPS, lipopolysaccharide; MCP-1, monocyte chemotactic protein-1.