THE EFFECTS OF HYALURONAN ON THE MENISCUS AND ON THE ARTICULAR-CARTILAGE AFTER PARTIAL MENISCECTOMY

The effect of hyaluronan (molecular weight = 8 x 10(5)) on the meniscu s and on the articular cartilage was assessed after partial meniscecto my in a rabbit model, On gross examination, remodeled meniscus appeare d as newly synthesized translucent tissue, and was seen in both vehicl e-and hyaluronan-treated menisci, Histologically, safranin O staining revealed the strong presence of glycosaminoglycans in the newly remode led tissue, and polarized light demonstrated the absence of mature col lagen architecture, Hydration of the hyaluronan-treated menisci was si gnificantly less than that of the vehicle-treated menisci, and the red ucible collagen cross-link dihydroxylysinonorleucine was significantly increased in the hyaluronan-treated menisci compared with the vehicle -treated menisci, indicative of a greater degree of collagen remodelin g, In situ hybridization of vehicle-and hyaluronan-treated menisci rev ealed a high level of type I procollagen mRNA expression and minor exp ressions of types II and III mRNA, Expression of the type collagen gen e appeared to be more pronounced in the hyaluronan-treated menisci tha n in the vehicle-treated menisci, The tibial plateaus revealed mild ca rtilage fibrillation after partial meniscectomy, A statistically signi ficant difference between vehicle-and hyaluronan-treated cartilage was not demonstrated in the present study because of the slow development (i,e,, 12 weeks) of osteoarthritis after partial meniscectomy in the rabbit model, These results suggest that in the rabbit model, hyaluron an enhances collagen remodeling and inhibits meniscal swelling after p artial meniscectomy in the avascular region.