Time-sequential changes in biomechanical and morphological properties of articular cartilage in cryopreserved osteochondral allografting.

This study examined time-sequential changes in the biomechanical and morphological properties of articular cartilage that had received cryopreserved osteochondral allografting. Osteochondral blocks obtained from the femurs of 18 rabbits were cryopreserved with dimethylsulfoxide (DMSO), using a two-step freezing method, and allografted to the femurs of another 18 rabbits. Specimens for biomechanical and morphological examinations were prepared at the second, fourth, and twelfth weeks after allografting (n = 18). In 12 allografted rabbits, biomechanical features were examined with an indentation test apparatus, and histological changes were studied with a light microscope (second week, n = 4; fourth week, n = 4; twelfth week, n = 4). In the other 6 allografted rabbits, cartilage surfaces were studied with a scanning electron microscope (second week, n = 2; fourth week, n = 2; twelfth week, n = 2). For controls, fresh, DMSO-treated, or DMSO-treated + cryopreserved specimens were examined biomechanically and morphologically. In the time-sequential examination of biomechanical features, both the parameter for elasticity (i.e., ratio of instant elastic strain to maximum strain) and the parameter for viscosity (i.e., average retardation time) significantly changed. Light microscopy showed chronological decreases in safranin-O staining intensity in the matrix, and progression of degeneration. On scanning electron microscopy, disruption of the cartilage surface was also recognized. Therefore, changes in biomechanical properties due to cryopreservation could cause irreversible changes in the cartilage in cryopreserved osteochondral allografting.

Antigenicity of desamido-insulin and monocomponent insulin.

No consensus about the antigenicity of monocomponent insulin has yet been reached. We have therefore administered different insulin preparations to rabbits and rats to determine IgG and IgE antibody production. The preparations used were porcine monocomponent insulin, conventional bovine and porcine insulin powders, porcine b-component and synthesized porcine mono-desamido-insulin and hexa-desamido-insulin. In rabbits, porcine b-component was the most antigenic preparation, followed by conventional bovine and porcine insulins. No antibody production was observed with the other preparations. In rats the 60 h passive cutaneous anaphylaxis test showed virtually no insulin IgE antibody production in response to porcine monocomponent insulin. However, if porcine b-component or porcine hexa-desamido-insulin was employed both for sensitisation and as the challenging antigen, positive skin reactions were observed with demonstration of insulin IgE antibodies. Our results confirm the low antigenicity of the pharmaceutical preparation of porcine monocomponent insulin and suggest that porcine hexa-desamido-insulin and porcine b-component administration may result in the production of reagin-type antibodies.