A morphologic, biochemical, and biomechanical assessment of short-term effects of osteochondral autograft plug transfer in an animal model.

PURPOSE: The objective of this study was to assess the short-term changes that occur after an osteochondral autograft plug transfer from the femoral trochlea to the medial femoral condyle in a goat model. TYPE OF STUDY: Articular cartilage repair animal study. METHODS: Six adult male goats were used in this study. Two 4.5-mm osteochondral plugs were transferred from the superolateral femoral trochlea to 2 recipient sites in the central portion of the medial femoral condyle for a survival period of 12 weeks. Postmortem, the global effects of the procedure were assessed by gross morphologic inspection and by analyzing the synovial DNA for inflammatory response. The recipient sites were also evaluated histologically and biomechanically. Metabolic activity was determined by (35)SO(4) uptake, and viability was assessed using a live/dead stain and by confocal laser microscopy. RESULTS: There was no evidence of significant gross morphologic or histologic changes in the operative knee as a result of the osteochondral donor or recipient sites. The patella, tibial plateau, and medial meniscus did not show any increased degenerative changes as a result of articulating against the donor or recipient sites of the osteochondral autografts. Analysis of synovial DNA revealed no inflammatory response. Biomechanically, 6- to 7-fold greater stiffness was noted in the cartilage of the transferred plugs compared with the control medial femoral condyle. Furthermore, on histologic examination, the healing subchondral bone interface at the recipient site had increased density. Glycosaminoglycan synthesis as determined by (35)SO(4) uptake was upregulated in the transplanted cartilage plug relative to the contralateral control, showing a repair response at the site of implantation. And finally, confocal microscopy showed 95% viability of the transferred plugs in the medial femoral condyle region. CONCLUSIONS: Our findings demonstrate the ability to successfully transfer an osteochondral autograft plug with maintenance of chondrocyte cellular viability. The transferred cartilage is stiffer than the control medial femoral condyle cartilage, and there is concern regarding the increased trabecular mass in the healing subchondral plate, but these do not result in increased degenerative changes of the opposing articular surfaces in the short term.

Donor cell fate in tissue engineering for articular cartilage repair.

Articular cartilage repair is a clinical challenge because of its limited intrinsic healing potential. Considerable research has focused on tissue engineering and transplantation of viable chondrogenic cells to enhance cartilage regeneration. However, the question remains: do transplanted allogenic cells survive in the repair with time? This study assessed donor cell fate after transplantation of male New Zealand White rabbit perichondrium cell and polylactic acid constructs into osteochondral defects created in the medial femoral condyles of female New Zealand White rabbits. Repair tissue was harvested at 0, 1, 2, 3, 7, and 28 days after implantation and was evaluated for cell viability and total cell number using confocal microscopic analysis. The number of donor cells in each sample was estimated using quantitative polymerase chain reaction targeting a gender-specific gene present on the Y-chromosome, the sex-determining region Y gene, and a control deoxyribonucleic acid present in male and female cell deoxyribonucleic acid, the matrix metalloproteinase-1 gene promoter. Average cell viability was found to be 87% or more at all times. Donor cells were present in repair tissue for 28 days after implantation. However, the number of donor cells declined from approximately 1 million at Time 0 to approximately 140,000 at 28 days. This decline in donor cells was accompanied by a significant influx of host cells into the repair tissue. This study shows that the sex-determining region Y gene is a valuable marker for tracking the fate of transplanted allogenic cells in tissue engineering.