Correlating Chemical Changes in Subchondral Bone Mineral due to Aging or Defective Type Ⅱ Collagen by Raman Spectroscopy

摘要

We show that early indicators of osteoarthritis are observed in Raman spectroscopy by probing femur surfaces excised from mouse models of early-onset osteoarthritis. Current clinical methods to examine arthritic joints include radiological examination of the joint, but may not be capable of detecting subtle chemical changes in the bone tissue, which may provide the earliest indications of osteoarthritis. Recent research has indicated that the subchondral bone may have a more significant role in the onset of osteoarthritis than previously realized. We will report the effect of age and defective type Ⅱ collagen on Raman band area ratios used to describe bone structure and function. The carbonate-to-phosphate ratio is used to assess carbonate substitution into the bone mineral and the mineral-to-matrix ratio is used to measure bone mineralization. Mineral-to-matrix ratios indicate that subchondral bone becomes less mineralized as both the wild-type and Dell (+/-) transgenic mice age. Moreover, the mineral-to-matrix ratios show that the subchondral bone of Dell (+/-) transgenic mice is less mineralized than that of the wild-type mice. Carbonate-to-phosphate ratios from Dell (+/-) transgenic mice follow the same longitudinal trend as wild-type mice. The ratio is slightly higher in the transgenic mice, indicating more carbonate content in the bone mineral. Raman characterization of bone mineralization provides an invaluable insight into the process of cartilage degeneration and the relationship with subchondral bone at the ultrastructural level.