Regenerating rib cartilage tentatively used as a source of chondrocytes for transplantation

In search for cartilage which could serve as a source of chondrocytes for autogeneic transplantation in mature individuals we studied the morphological appearance and digestibility of normal rib cartilage and regenerated cartilage formed after subperichondrial removal of the former in adult dogs. Cells liberated after collagenase digestion were transplanted intramuscularly to see whether they will reconstruct cartilage similarly as it happens after transplantation of fetal chondrocytes. Chondrocytes in normal rib cartilage were arranged in three zones and lay in large isogenous groups. Collagenase dissolved only the peripheral zone. Isolated cells did not reconstruct cartilage after transplantation. No distinct zones could be seen in regenerated cartilage. Chondrocytes lay singly or in pairs but were not numerous. Regenerated cartilage could be completely dissolved by collagenase, but the yield of cells was low owing to their low content in digested material. After transplantation chondrocytes from regenerated cartilage reconstructed cartilage in one out of ten transplants. The possibility of increasing the cellularity of regenerated cartilage by stimulation of the perichondrium with factors known to promote chondrocyte growth in vitro is discussed.