Class VI intermediate filament protein nestin is induced during activation of rat hepatic stellate cells

Abstract

Hepatic stellate cells are considered to be liver-specific pericytes that play a key role in liver fibrosis. Because these cells express desmin and smooth muscle ␣-actin, they were assumed to be of myogenic origin. This hypothesis became doubtful when it was reported that stellate cells also express glial fibrillary acidic protein and neural cell adhesion molecule. In the present study, we show that activated stellate cells express nestin, a class VI intermediate filament protein originally identified as a marker for neural stem cells. Expression of nestin was first studied during spontaneous activation of stellate cells in culture. Immunohistochemistry showed that nestin-positive stellate cells already appeared at day 3, and nearly all the cells became positive for nestin at day 6 and 15. The immunoreaction was present in filaments except in dividing cells. The presence of messenger RNA transcript for nestin was shown by reverse transcription polymerase chain reaction and sequencing of amplified complementary DNA. We then compared the presence of nestin with that of other intermediate filament proteins and smooth muscle ␣-actin. Immunoblotting showed that the relative concentrations of nestin, desmin, and vimentin increased between day 2 and 6 in primary culture. After the initial increase vimentin leveled off, while nestin and desmin showed a tendency to decrease. This pattern was quite different from that of glial fibrillary acidic protein, which kept declining, and smooth muscle ␣-actin, which increased continuously up to day 13 in culture. We then studied the presence of nestin in normal and CCl 4 -injured rat liver. In normal liver, minimal immunoreaction for nestin was observed within the liver parenchyma. During induction of fibrosis by carbon tetrachloride, nestin-positive stellate cells appeared at 6 weeks, which was late in comparison with the induction of desmin and smooth muscle ␣-actin. We conclude that nestin is induced in stellate cells during transition from the quiescent to the activated phenotype; culture activation is a stronger stimulus than in vivo activation by injection of CCl 4 . Taken Hepatic stellate cells exert specific liver functions: storage of large amounts of retinyl esters, synthesis and breakdown of hepatic extracellular matrix, secretion of a variety of cytokines, and control of the diameter of the sinusoids.

Hedgehog-mediated mesenchymal–epithelial interactions modulate hepatic response to bile duct ligation

“…Such work is likely to be difficult, however, because the origin of both cell types is uncertain. Coexpression of epithelial, mesenchymal, and/or neural markers has been reported in HSC, 12,[67][68][69][70][71] making it difficult to discern their derivation and giving rise to speculation that such cells may undergo mesenchymal-epithelial transitions. 69,71 Gene expression profiles of HSC and other liver fibroblastic cells also change significantly during liver injury, 70 further confounding assessment of cell lineage.…”

Synaptophysin: A Novel Marker for Human and Rat Hepatic Stellate Cells

“…Since Kupffer's first description of Sternzellen (hepatic stellate cells) in liver, using gold chloride staining in search of nerve fibers, 48 indications of neural/neuroendocrine differentiation of hepatic stellate cells have been accumulating. Stellate cells show GFAP reactivity, [25][26][27] N-CAM expression, 28,29 nestin reactivity, 27 and SYN expression. All these can be considered as arguments in favor of a neural/neuroendocrine differentiation or origin.…”

“…24 GFAP was demonstrated to be positive in only a periportal subpopulation of human stellate cells. 27 N-CAM is rather nonspecific in that it also stains reactive bile ductules 41 and nerve endings. 28 Nestin, finally, stains bile duct cells and vascular endothelium in rat livers and has not been tested on human liver biopsies yet.…”

“…In vitro, however, nestin staining of human stellate cells was negative. 27 SYN is immunoreactive in human stellate cells ( Figure 1) and nerve bundles. In vivo, nerve endings and stellate cells can be distinguished by their morphology: stellate cells contain a nucleus that in the resting state is indented by lipid droplets; parenchymal nerve endings as a rule do not contain a nucleus.…”

“…Stellate cells express the intermediate filament glial fibrillary acidic protein (GFAP), [25][26][27] and activated rat stellate cells express the intermediate filament nestin. 27 Human stellate cells are immunoreactive with neural cell adhesion molecule (N-CAM) antibody, 28 whereas rat stellate cells become positive for N-CAM on activation. 29 Synaptophysin (SYN) is a major transmembrane glycoprotein of small (30 -80 nm) electron-translucent (SET) vesicles.…”