Articular cartilage preservation and storage. III. Quantitative zonal analysis of cytoplasmic components of stored versus in vivo articular cartilage chondrocytes.

Abstract

The cytoplasmic components of chondrocytes in the various zones of articular cartilage of the medial femoral condyle of six-week-old male New Zealand white rabbits stored in tissue culture medium at 37 degrees in 5% CO2 and air were quantitated from electron micrographs, and the results were compared statistically with the cytoplasmic components of chondrocytes in the corresponding zones of in vivo articular cartilage. The major changes that occurred during storage were: (1) an increase in the amount of lipid bodies in chondrocytes in the tangential, transitional, and calcified zones; (2) a decrease in the number of holes in the cytoplasm of chondrocytes in the radial and calcified zones; (3) a decrease in the amount of endoplasmic reticulum in the radial and calcified zones; and (4) an increase in cell size and cytosol area in the tangential and transitional zones but a significant decrease in cell size and cytosol area in the calcified zone. Stored articular cartilage chondrocytes demonstrated cellular changes associated with aging, whereas in vivo articular cartilage chondrocytes demonstrated changes associated with degeneration. The matrix of stored articular cartilage in the tangential, transitional, and upper part of the radial zones showed a decrease in opacity due to a decrease in the number of collagen fibers per unit area of matrix, a condition termed "chondroporosis." This study demonstrates that articular cartilage stored in standard tissue culture medium under ideal physiological conditions is morphologically abnormal. Based on these findings, one would not expect such stored cartilage to remain functionally intact when transplanted to replace articular cartilage loss.