Cryopreservation with dimethyl sulfoxide sustains partially the biological function of osteochondral tissue

The clinical routine use of bone allograft transplants dates back to the discovery that grafts devitalized by freezing bear a reduced antigenicity. Graft failures, caused by a host versus graft reaction, however, remain a clinical problem. Previous investigations on pancreatic islet allografts revealed improved survival and biological function when fast cryopreservation (-70 degrees C/min) was performed in the presence of dimethyl sulfoxide (DMSO). The aim of this study was to determine the effect of fast freezing using DMSO on the biological function of osteochondral tissues. Organ culture was performed with neonatal femora of mice, untreated, rapidly frozen (-70 degrees C/min) with DMSO, or frozen without DMSO. After the culture, tissue morphology, cellular proliferation, osteoblast function, osteoclasts, and the presence of antigen-presenting cells were investigated. In untreated control femora histology appeared normal and proliferating and collagen-synthesizing osteoblasts, osteoclasts, and B-cells and macrophages were present. In frozen femora (with and without DMSO) a disintegration of the periosteum and the epiphyseal growth plate were observed and no active osteoblasts could be detected. Osteoclasts were partially detached from the bone surface. Cell proliferation was fully blocked in femora frozen in the absence of DMSO, while freezing in the presence of DMSO preserved cell proliferation in the medullary canal. The proliferating cells do not express epitopes present on the cells of the B-cell or macrophage lineages. Although the biological function of osteoblasts and osteoclasts was lost upon freezing of osteochondral tissue, DMSO included in freezing protocols preserves some residual cell viability which may be of importance for early graft revascularization as has been previously demonstrated by our group.