Neocartilage derived from transplanted perichondrium: what is it?

The articular surfaces of rabbit patellae were completely eburnated and resurfaced with ear perichondrium or fascia lata or left unresurfaced. Both mature and immature animals were used and were sacrificed at 3, 6, and 12 months postoperatively. Only those joints resurfaced with perichondrium formed neocartilage. The neocartilage was composed of variable amounts of chondroitin sulfate; histologic appearances ranged from hyaline cartilage to fibrocartilage to fibrous tissue. Scanning electron microscopy revealed that the neocartilage surface was irregular, fibrillated, and disorganized. Biochemical analyses documented the variability of the neocartilage, one specimen being quite similar to normal articular cartilage. Cell-culture experiments with isolated rabbit periochondrocytes, chondrocytes, and fibroblasts were conducted to determine whether those cell types could produce cartilage matrix in vitro. The ability of sparse cultures of perichondrocytes to synthesize chondroitin sulfate under serum-free conditions is evidence that these cells are unlike fibroblasts and more like chondrocytes in their in vitro behavior. These in vitro and in vivo studies show that perichondrocytes are relatively differentiated cells with the potential to make cartilage. Elucidation of the factors contributing to the variable results of perichondral transplantation is essential before clinical applications will be predictably successful.