Use of cultured embryonal chick epiphyseal chondrocytes as grafts for defects in chick articular cartilage.

Full-thickness defects in articular cartilage were repaired with cultured homologous embryonic chick epiphyseal chondrocytes embedded in a biological resorbable immobilization vehicle (BRIV). This graft was successfully transplanted in mechanically induced defects in the surface of condylar articular cartilage of the tibiotarsal joint of four-month-old roosters. Healing of the defects was observed macroscopically, histologically, and histochemically and with the use of biochemical analyses for six months. Chondrocyte proliferation was seen 48 hours after implantation, and a hyaline cartilage matrix surrounding the cells was present two weeks later. Within eight weeks, the defects were completely filled with hyaline cartilage, which integrated smoothly with the neighboring cartilage without the formation of fibrous tissue at the interface. The cell content and rate of proteoglycan synthesis remained high for four months, then declined slowly to the level of the surrounding cartilage. Six months after transplantation, the cartilaginous tissue in the wound at levels below the ossification front showed penetration by vascular elements and young bone trabeculae at the margins of the reparative tissue. No signs of immunogenic rejection of the implants were observed. These results may be related to the employment of a capable source of cells, i.e., cultured chondrocytes characterized by a high mitotic rate and an early stage of development. The transplanted cells grew well and maintained their initial rate of proliferation, with definite maturation and transformation. The resulting cartilage was structurally reorganized according to the host pattern and under the influence of multitudinous environmental conditions. The articular zone preserved its cartilaginous phenotype, whereas the subchondral regions were transformed into bone.