Acidic fibroblast growth factor attenuates the cytotoxic effects of peroxynitrite in primary human osteoblast precursors

Background: skeletal injury and associated ischemia and inflammation induce the generation of pro-oxidants such as peroxynitrite (ONOO-), which has be en demonstrated to induce apoptosis in several cell lines. Fibroblast growt h factor (FGF-1) is important for coordinating osteogenesis and angiogenesi s of osseous repair. In vitro studies were performed examining the effect o f FGF-1 on human osteoblast progenitor stromal stem (HSS) cell proliferatio n, differentiation, and response to ONOO-. Methods: HSS cells were isolated and growth kinetics determined in the pres ence and absence of FGF-1. The effect of FGF-1 on Hss cell expression of os teoblast-specific osteopontin and osteocalcin mRNA and protein was examined by reverse transcriptase polymerase chain reaction and Western blot techni ques. To determine the sensitivity of HSS cells to ONOO- in the absence and presence of FGF-1 pretreatment, cells were exposed to varying concentratio ns of the oxidant and examined for cell death using quantitative fluorescen ce staining with fluorescein diacetate and propidium diacetate. Results: Treatment of HSS cells with FGF-1 significantly enhanced cellular growth rates by 5 days (4.6 x 10(5) cells/mL vs. 3.1 x 10(5) cells/mL) and induced expression of both osteopontin and osteocalcin mRNA and protein. Ex posure of HSS cells to ONOO- resulted in a dose- and time-dependent delayed cell death that was more characteristic of apoptosis than necrosis, Pretre atment of HSS cells with FGF-1 prevented ONOO- mediated apoptosis. Conclusion: In vitro, treatment of HSS cells with FGF-1 stimulates cell gro wth and induces expression of differentiation markers specific to osteoblas ts. FGF-1 treatment renders osteoblast precursors resistant to the cytotoxi c effects of ONOO-. These results suggest that FGF-1 promotes the progressi on of bone repair mechanisms by increasing the population of osteoblasts an d imparting protection to the cell line from the hostile inflammatory envir onment.