The effects of hyaluronan on tissue healing after meniscus injury and repair in a rabbit model

To assess the effect of hyaluronan on meniscus injury and repair, we had 35 mature New Zealand White rabbits undergo bilateral meniscus injury and rep air (19 in the peripheral region, and 16 in the inner region). A longitudin al tear was created in the medial meniscus and repaired with horizontally p laced nylon sutures. The left knee joint received intraarticular injections of hyaluronan 1 week after surgery and once a week for 5 weeks. The right knees were injected with phosphate-buffered saline (the carrier vehicle of the hyaluronan). Twelve weeks after repair, tears in the peripheral region showed gross and histologic evidence of healing, with no difference between the vehicle- and hyaluronan-treated menisci. Biochemically, the ratio of r educible collagen cross-links in the hyaluronan-treated menisci was signifi cantly higher than in the vehicle-treated menisci, indicating greater level of collagen remodeling. Biomechanically the vehicle- and hyaluronan-treate d menisci demonstrated similarly high tearing load and fracture toughness. In the inner region, poor healing response was observed grossly and histolo gically in both treatment groups. Water content in the hyaluronan-treated m enisci was significantly lower than in the vehicle-treated menisci, indicat ing a lower level of swelling. Hyaluronan treatment stimulated collagen rem odeling in the peripheral region and inhibited swelling of the meniscus rep aired in the inner region.