“…Ultrastructurally, plenty of matrix vesicles (MVs; Anderson, 1967Anderson, , 1969Bonucci, 1967Bonucci, , 1970 are found in these zones. These are the TNAP-rich MVs first described by Matsuzawa and Anderson (1971) and later confirmed for both types of cartilage (Akisaka & Gay, 1985;Takagi & Toda, 1979;Takechi & Itakura, 1995a, 1995b. When these TNAP-rich MVs are isolated and cultured in mineralizing solutions, they show mainly extravesicular apatite deposition (Boskey et al, 1994).…”