CHONDROCYTE-FIBRIN MATRIX TRANSPLANTS FOR RESURFACING EXTENSIVE ARTICULAR-CARTILAGE DEFECTS

Cartilage resurfacing by chondrocyte implantation, with fibrin used as a vehicle, was examined in large (12 mm) full-thickness articular car tilage defects in horses. Articular chondrocytes, isolated from a 9-da y-old foal, were mixed with fibrinogen-and injected with thrombin, in a 1:1 mixture, into 12 mm circular defects on the lateral trochlea of the distal femur of eight normal horses. The contralateral femoropatel lar (knee) joint served as a control in which the defect was left empt y. Synovial fluid from the femoropatellar joints was sampled on days 0 , 4, 7, 30, 120, and 240 postoperatively. Groups of four horses were k illed at 4 or 8 months postoperatively, and the repair tissue was eval uated by gross and histologic examination with use of hematoxylin and eosin and safranin 0 staining and by autoradiography. Biochemical anal yses included quantitation of proteoglycan, total collagen, and type-I I collagen in the repair tissue. Grossly, grafted defects had improved filling of the cartilage lesions; histologically, these areas consist ed of differentiated chondrocytes in the deep and middle zones. The ce llular arrangement in these zones resembled that of hyaline cartilage. The control defects contained poorly attached fibrous tissue througho ut. Grafted tissue at 8 months had increased proteoglycan synthesis ev ident by both safranin O staining and autoradiography. Glycosaminoglyc an quantitation by dye-binding assay confirmed a significantly elevate d glycosaminoglycan content in grafted defects (58.8 mu g/mg of dry we ight) compared with control defects (27.4 mu g/mg; p < 0.05). Similarl y: the levels of chondroitin sulfate/dermatan sulfate was significantl y elevated in the grafted defects, and this was the predominant glycos aminoglycan epitope present. There was a statistically significant (p < 0.05) increase in type-II collagen in the grafted tissue at 8 months (61.2% grafted; 25.1% control). This resurfacing attempt with use of allograft chondrocytes, secured in large full-thickness articular defe cts with polymerized fibrin, resulted in an improved cartilage surface in comparison with the control defects, a significantly greater aggre can level, and a significantly higher proportion of type-II collagen.