Introduction: Local application of growth factors to stimulate wound and fracture healing is attracting increasing interest. We studied the effect of local application of a potent angiogenic growth factor, basic fibroblast growth factor (bFGF), on resistance to local infection after soft tissue trauma.
Methods: For in-vitro and in-vivo experiments, we used recombinant human bFGF. The in-vitro investigations were performed by isolation of human leukocyte fractions, cytokine analysis, phagocytosis assay, flow cytometry, and LDH assay. For the in-vivo investigation, a paired comparison of infection rates was carried out on Sprague-Dawley rats after standardized, closed soft tissue trauma and local, percutaneous bacterial inoculation of different concentrations of Staphylococcus aureus (2 x 10(4) to 2 x 10(7) colony-forming units (cfu)). The lower leg was treated with 1, 10 or 100 ng bFGF (16 animals for each concentration) and without bFGF (16 animals).
Results: Cytotoxic reactions due to the concentrations of bFGF used could be excluded in the in-vitro tests since incubations of isolated peripheral blood mononuclear cells (PBMCs) with increasing concentrations of bFGF for 24 h did not lead to an increase in the release of lactate dehydrogenase in the culture supernatants compared to corresponding control incubations without any bFGF added. A significant increase in cytokine release was observed after the co-incubation of PBMCs with 100 or 200 ng of the same bFGF that was used for the animal experiments. Furthermore, the capacity of phagocytes in whole blood to phagocytose bacteria was suppressed in the presence of 100 ng exogenously added bFGF. We found continuously reduced granulocytic phagocytosis in FGF-supplemented blood compared to non-supplemented blood. In the in-vivo investigation, the infection rate for the group without bFGF was 0.25. In the groups with 1, 10 and 100 ng bFGF, the infection rates were 0.5, 0.7 and 0.8, respectively. A dose-dependent increase in infection rate was observed after local application of bFGF, compared to the untreated control group. The difference in infection rates for the groups in which 10 and 100 ng bFGF was used, relative to the group without bFGF, was statistically significant.
Interpretation: If these initial results are confirmed for other potent angiogenic growth factors, then the local use of growth factors for stimulation of wound and bone healing--a main focus of current research in traumatology--will have to be reconsidered and preceded with a strict evaluation of the risks and benefits.