Basic fibroblast growth factor and bone induction in rats.

Bone induction is initiated by bone morphogenetic proteins, but local growth factors present in demineralized bone matrix (DBM) may further regulate the process. We have previously shown that local application of recombinant human basic fibroblast growth factor (bFGF) in a carboxymethyl cellulose gel to DBM implants increases the bone yield, as measured by calcium content. In the present study, similar experiments were evaluated with histomorphometry. The chondrocyte number at 2 weeks was increased by the application of 15 ng bFGF. This increase was due to an increased number of chondrocyte clusters, i.e., cartilage formation was initiated in more places within the implant. The size of the individual chondrocyte clusters was the same as in the controls. Thus, the bFGF had probably stimulated cellular events preceding chondrocyte proliferation. At 3 weeks, the chondrocytes were fewer than in controls, and instead there was more bone. Thus, cartilage formation was increased by bFGF, and its replacement by bone came earlier. However, 1900 ng of bFGF had a profound inhibitory effect on both cartilage and bone formation.