Vitreous preservation of articular cartilage from cryoinjury in rabbits

Frozen osteoarticular grafts treated with liquid nitrogen are utilized for joint reconstruction after tumor resection, but the joints may subsequently develop osteoarthritic changes. To preserve articular cartilage from cryoinjury, we modified a vitrification method utilized for embryo cryopreservation and demonstrated in vitro that our vitrification protocol was effective for protecting cartilage from cryoinjury. In this study, we investigated in vivo whether this vitrification method could protect against osteoarthritic changes in articular cartilage. Osteochondral plugs were obtained from the distal femur of rabbits. These grafts were divided into 3 groups: Fresh group (F-group), non-vitrification group (N-group), and vitrification group (V-group). After treatment, the plugs were re-implanted as autografts. Histological findings, chondrocyte viability, and ultrastructural examinations were examined 6, 12, and 24 weeks after implantation. Histological findings of chondrocytes for the V-group showed no significant difference from those of the F-group at any time point except at 24 weeks postimplantation at the non-weight bearing site (p < 0.05). Viability of chondrocyte showed no significant difference from those of the F-group except at 12 weeks postimplantation at the bearing site (p < 0.05). In contrast, viable cells disappeared from the N-group and histology and viability significantly differed between the N-group and the V-group. Transmission electron microscopy demonstrated preservation of chondrocyte structure in the V-group and the F-group, but chondrocytes of the N-group were abnormally electron dense. Our vitrification method was effective in protecting chondrocytes from cryoinjury that might lead to cartilage degeneration. Reconstructing joints with osteoarticular grafts containing living cartilage may help to avert osteoarthritic changes. Our vitrification method could prove useful for reconstruction with frozen tumor-containing autografts and for long-term storage of living cartilage for allografts.