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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.

We investigated the histological and immunohistochemical changes within and around the cervical intervertebral discs in symptomatic myeloradiculopathy and myelopathy patients. A total of 163 cervical intervertebral discs, 100 herniated discs and 63 spondylotic discs, were harvested en bloc during anterior decompressive surgeries and histological examination was performed, focusing on nucleus pulposus, annulus fibrosus, cartilaginous endplate, and ligamentous enthesis. There was a close relationship between MRI grade and histological degenerative changes. Histological features of the herniated intervertebral discs were the presence of granulation tissue, newly-developed blood vessels and infiltration of CD68-positive cells, which surrounded the herniated tissue in the outer layer of the annulus fibrosus. Marked vascular invasion was detected in 67% of herniated discs and 54% of spondylotic discs. Immunohistochemically, chondrocytes positive for matrix metalloproteinase (MMP)-3, tumor necrosis factor (TNF)-α, basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) were detected in both herniated and spondylotic discs. Our results indicate that the neoangiogenesis process is associated with overexpression of bFGF and VEGF, and suggest that intervertebral disc degradation is enhanced by macrophage infiltration, which is regulated by MMP-3 and TNF-α. The expression of these proteins may be enhanced by the tear of annulus fibrosus.

We investigated histopathological and immunohistochemical properties of the ligamentum flavum of the lumbar spine with calcium crystal deposition. Ligamentum flavum of the lumbar spine containing calcium deposits were harvested from 41 surgical cases. Sections of the ligaments were immunostained for estrogen receptor (ER), progesterone receptor (PR), and transforming growth factor (TGF)-β. The results were compared with those of ligaments without calcium deposits. The elastic fibers of the ligament with calcium deposits showed marked degeneration (irregular arrangement and fragmentation of fiber bundles) and nodular lesions. Deposits of calcium crystals were present in these areas where elastic fibers were degenerated. Immunostaining for ER was positive in these areas, and PR as well as TGF-β-containing chondrocytes were detected around and within the calcified areas. TGF-β, ER and PR-containing chondrocytes appeared to precipitate deposition of calcium crystals in the nodular lesions of the degenerated lumbar ligamentum flavum. Our results suggest that TGF-β and sex hormones play a role in the calcification of the lumbar ligamentum flavum.