Local injection of TGF-beta increases the strength of tibial fractures in the rat.

The effect of Transforming Growth Factor beta (TGF-beta) administered locally around the fracture line of healing rat tibial fractures was investigated after 40 days of healing. TGF-beta in a dose of 4 ng or 40 ng was injected every second day during the healing period. The strength, stiffness, energy absorption and deflection of the fractures were measured in a materials-testing machine. Compared with placebo-treated animals, the ultimate load of the fractures increased in the group injected with 40 ng of TGF-beta, but not in those injected with 4 ng. TGF-beta induced a dose-dependent increase in the cross-sectional area of the callus and bone at the fracture line. Consequently, local treatment of fractures with TGF-beta increases the callus formation and strength. The energy absorption and deflection capacities of the healing fractures are preserved.