Regional differences in the healing potential of the meniscus-an organ culture model to eliminate the influence of microvasculature and the synovium.

Meniscal healing is well known to be region-specific, and this is thought to be mainly due to its specific vascularity. The purpose of this study was to assess regional differences in the intrinsic healing potential of the meniscus, using an organ culture model to eliminate the influence of microvasculature and the synovium. A full-thickness circular defect, 1.5 mm in diameter, was created in the inner avascular zone in meniscal explants from rabbits. As a control, a column of 1.5 mm in diameter was removed then replanted in the area where it had been obtained (Group C). In the experimental group, a 1.5 mm-diameter meniscal graft obtained from the peripheral zone of the same specimen was implanted in the damaged area (Group T). These meniscal explants were cultured for 2, 4 or 6 weeks, and the relationship between the recipient tissue and the graft was examined using both gross and histological semiquantitative scoring. The 6-week gross-examination showed that the openings were more apparent in Group C, and the score of Group T was significantly higher than that of Group C (P=0.0152). Histologically, the healing responses after both 4 and 6 weeks of incubation were significantly better in Group T than in Group C (P=0.0237, 0.0281). These results using organ culture demonstrate that intrinsic healing potential differs even without the influence of vascular supply and the synovium, indicating that the superior healing potential in the peripheral zone may contribute to the good meniscal healing in this location.