To investigate cartilage response to fibroblast growth factor-2 (FGF-2) with increasing age in vivo, we examined the effect of FGF-2 on partial thickness defects of immature and mature rabbits.
Sixty-nine Japanese white rabbits (34 immature rabbits, 35 mature rabbits) were examined. We made experimental partial thickness defects in articular cartilage of the knees. Then, we injected FGF-2 into the knees eight times, immediately after surgery and every 2 days for 2 weeks. A single dose of FGF-2 was 10 ng/0.1 ml or 100 ng/0.1 ml. In the control group, 0.1 ml saline was injected on the same time schedule. The rabbits were sacrificed at intervals following surgery that ranged from 2 to 48 weeks. The specimens were stained with toluidine blue and examined microscopically. We used a modified semiquantitative scale for evaluating the histological appearance of repair.
In immature rabbits, the cartilage repair in the FGF-2 (100 ng)-treated group was significantly better than that of the other groups. The defects were almost completely repaired with chondrocytes that showed a round to polygonal morphology, and large amounts of extracellular matrix with intense metachromatic staining. In mature rabbits, however, there was apparently no effect from FGF-2 in either group.
Application of FGF-2 facilitated cartilage repair in partial thickness defects in immature rabbits, but not in mature ones.