In vitro cartilage formation on porous hydroxyapatite ceramic granules.

Porous hydroxyapatite ceramic granules (diameter 0.5-1 mm) provide an excellent in vitro matrix for cell growth. Canine chondrocytes maintained their collagen (Type II) phenotype up to 11 mo when cultured on these granules. Chondrocytes proliferated throughout the 13 mo of culture. Cells divided and added on to form multilayers around each ceramic granule. By the end of 11 mo, some layers were thicker than the diameter of the granules. Cell number per culture dish increased 240-fold over the original number of cells seeded in 8 mo of culture. Morphologically, chondrocytes remained spherical and formed cohesive multilayers as early as 1 wk. Metachrometric extracellular matrix was evident by the first week and increased through the 13 mo period.