THE ISOLATION AND CHARACTERIZATION OF MAGNESIUM WHITLOCKITE CRYSTALS FROM HUMAN ARTICULAR-CARTILAGE

A number of basic calcium phosphate crystals have been demonstrated in human articular tissues. The exact relationship between crystal depos ition and disease remains obscure, although there is evidence supporti ng a rapid degenerative arthropathy within a specific set of patients. Limited reports of 'cuboid' calcium phosphate microcrystals in articu lar cartilage have been made over the last 10 years. In this study the occurrence of such crystals, not apparent by light microscopy, in hum an articular cartilage has been confirmed by transmission electron mic roscopy and X-ray microanalysis of tissue prepared by aqueous and anhy drous processing techniques. A crystal isolation technique involving c ollagenase digestion, centrifugation and sodium hypochlorite treatment was developed enabling crystal characterization by electron and X-ray diffraction. Crystals were identified as magnesium whitlockite; the f irst report of this mineral in articular cartilage. The presence of th is mineral phase in normal and osteoarthritic articular cartilage is d iscussed with consideration given to physical conditions known to favo r whitlockite formation and those extant in articular cartilage.