The aim of the present study was to investigate the quantity and quality of hydroxyapatite (HA) in the zone of calcified cartilage of articular cartilage and underlying subchondral bone by Fourier transform infrared microscopy (FTIRM). We hypothesized that the amount of HA deposited in osteoarthritis (OA) might differ from normal cartilage, and that such differences might be significant in the pathology of OA. The tibial epiphysis of the male Hartley strain for the spontaneous OA model and the control Strain 13 guinea pigs (12-month old) were examined. The mineral:matrix ratio was determined by integrating areas of υ1, υ3 bands at 900-1200 cm-1 to Amid 1 band at 1585-1725 cm -1. The CO3:PO4 ratio was determined by integrating areas of υ2 carbonate band at 850-900 cm-1 to υ1, υ3 bands. In Hartley strain, the mean mineral:matrix ratio of the medial side was significantly lower than the lateral side at the zone of the calcified cartilage and subchondral bone. The mean CO3:PO 4 ratio was significantly higher in the medial side than the lateral one at the zone of the calcified cartilage and subchondral bone. In contrast, the results obtained from Strain 13 showed no significant differences between the two sides. Our results showed diminished deposition and increased maturation of HA in Hartley strain. These findings may correlate with the pathological process of knee OA, and indicate that FTIRM is a useful tool for determining the variability of HA in OA.
2004 By the Japan Society of Histochemistry and Cytochemistry