Session III - Combined Meeting with AAST

Thursday, October 12, 2000 Session III, Paper #18, 2:50 pm

Acidic Fibroblast Growth Factor (FGF-1) Protects Human Stromal Cells and Induces Differentiation into the Osteoblast Lineage

Donald A. Reiff, MD; Stacey Kelpke, PhD; John A. Thompson, PhD; University of Alabama, Birmingham, AL

Introduction: Skeletal injury and associated ischemia and inflammation induce generation of pro-oxidants such as peroxynitrite (ONOO-), which has been demonstrated to induce apoptosis in several cell lines. FGF-l is important for coordinating osteogenesis and angiogenesis of osseous repair. In vitro studies were performed examining the effect of FGF-1 on human osteoblast progenitor stromal stem (HSS) cell proliferation, differentiation and response to ONOO-.

Methods: HSS cells were isolated and growth kinetics determined in the presence and absence of FGF-l. The effect of FGF-l on HSS cell expression of osteoblast-specific osteopontin and osteocalcin mRNA and protein was examined by RT-PCR and Western techniques. To determine the sensitivity of HSS cells to ONOO- in the absence and presence of FGF-l pretreatment, cells were exposed to varying concentrations of the oxidant and examined for cell death using quantitative fluorescence staining with fluorescein diacetate and propidium diacetate.

Results: Treatment of HSS cells with FGF-l significantly enhanced cellular growth rates at 5 days (4.6x105 cells/ml vs 3.1x105 cells/ml; P<.O5) and induced expression of osteopontin and osteocalcin mRNA, as well as osteopontin protein. Exposure of HSS cells to ONOO- resulted in a dose-and time-dependent delayed cell death that was more characteristic of apoptosis than of necrosis. Pretreatment of HSS cells with FGF-l prevented ONOO- mediated apoptosis.

Conclusion: in vitro, treatment of HSS cells with FGF-1 stimulates cell growth and induces expression of differentiation markers specific to osteoblast. FGF-l signaling renders osteoblast precursors resistant to the cytotoxic effects of ONOO-. These results suggest that FGF-l promotes the progression of bone repair mechanisms by increasing the population of osteoblasts and imparting protection to the cell line from the hostile inflammatory environment.