Adenoviral-mediated transfer of p53 or retinoblastoma protein blocks cell proliferation and induces apoptosis in culture-activated hepatic stellate cells

The principal cellular effectors of fibrosis in liver are hepatic stellate cells (HSC). In response to liver injury these quiescent cells undergo a phenotypic change to a myofibroblastic cell type, proliferate and secrete matrix components. Thus, removal of activated HSC should be beneficial for the prognosis of hepatic fibrogenesis and preserve organ function. The purpose of this study was to investigate whether administration of adenoviruses constitutively expressing the p53 tumor suppressor or the retinoblastoma protein (pRb) is sufficient to induce cell arrest or apoptosis in culture-activated HSC. The expression of the transgenes was confirmed by Western blot analysis and immunohistochemistry. Both proteins were expressed mainly in the nucleus and their expression was associated with a marked inhibition of cell proliferation and induction of apoptosis as determined by measurement of phosphatidylserine exposed at the surface, proliferation assay, induction of the p21 cyclin-dependent kinase inhibitor, and an increase of caspase-3 activity. Additionally, electron microscopic analysis confirmed that activation of the p53-mediated pathway in HSC results in chromatin and cytoplasmic condensation, typical features of ongoing apoptosis. Our results indicate that transduction of p53 or pRb offers a feasible approach to induce apoptosis in activated HSC. Thus, targeted transfer of these proteins into HSC may be potentially useful for the treatment of hepatic fibrosis.