Relationship between cartilage and subchondral bone lesions in repetitive impact trauma-induced equine osteoarthritis
To correlate degenerative changes in cartilage and subchondral bone in the third carpal bone (C3) of Standardbred racehorses with naturally occurring repetitive trauma-induced osteoarthritis. Fifteen C3, collected from Standardbred horses postmortem, were assessed for cartilage lesions by visual inspection and divided into Control (CO), Early Osteoarthritis (EOA) and Advanced Osteoarthritis (AOA) groups. Two osteochondral cores were harvested from corresponding dorsal sites on each bone and scanned with a micro-computed tomography (CT) instrument. 2D images were assembled into 3D reconstructions that were used to quantify architectural parameters from selected regions of interest, including bone mineral density and bone volume fraction. 2D images, illustrating the most severe lesion per core, were scored for architectural appearance by blinded observers. Thin sections of paraffin-embedded decalcified cores stained with Safranin O-Fast Green, matched to the micro-CT images, were scored using a modified Mankin scoring system. Subchondral bone pits with deep focal areas of porosity were seen more frequently in AOA than EOA but never in CO. Articular cartilage damage was seen in association with a reduction in bone mineral and loss of bone tissue. Histological analyses revealed significant numbers of microcracks in the calcified cartilage of EOA and AOA groups and a progressive increase in the score compared with CO bones. The data reveal corresponding, progressive degenerative changes in articular cartilage and subchondral bone, including striking focal resorptive lesions, in the third carpal bone of racehorses subjected to repetitive, high impact trauma.
[Show abstract] [Hide abstract] ABSTRACT: Background Vitamin D appears to play an important role in bone and cartilage metabolism since its receptors are widely found in human articular chondrocytes. Thus, effects of variation of vitamin D may directly impact cartilage and bone biology. Questions/Purposes The aims of this study are to compare (1) articular cartilage structure and composition and (2) trabecular and cortical bone microstructure in rats with normal versus insufficient vitamin D levels. Methods Twenty-five mature, male Sprague-Dawley rats were allocated to two groups: (1) control arm (vitamin D replete—12 rats) and (2) an experimental arm (vitamin D deficient—13 rats). Vitamin D deficiency was induced using a vitamin D-deficient diet and UV light restriction. Rats were sacrificed after 4 weeks vitamin D deficiency was confirmed. The right knee was harvested for analysis of both the medial (MFC) and lateral femoral condyles (LFC). A region of interest was established on both condyles to correlate subchondral bone architecture and the overlying cartilage. Histological analysis was performed and graded using the modified Mankin score. Subchondral and cortical bony architecture was evaluated with micro-CT. Results After 4 weeks, the vitamin D-deficient group had statistically significant changes in cartilage structure in both the MFC and LFC [1.55 ± 0.6 vs. 4.23 ± 4.1 (p = 0.035) and 1.55 ± 0.6 vs. 3.53 ± 2.4 (p = 0.009), respectively]. Micro-CT analysis revealed no correlation between subchondral bone values and the overlying cartilage Mankin score (p = 0.460). No significant difference was evident between the subchondral bone of the control and study group. Conclusions Low levels of vitamin D have a deleterious effect on the cartilage. Given the high prevalence of vitamin D deficiency in the general population, these findings raise important questions about the potential role of vitamin D in articular cartilage health.
- "Future studies evaluating MMP and VDR, in this same animal model, will be necessary to better understand the role of vitamin D on articular cartilage. Different studies have shown subchondral bone changes in osteoarthritis [12, 19]. In our study, we did not observe significant differences in the subchondral bone between the groups. "
[Show abstract] [Hide abstract] ABSTRACT: We studied changes in articular calcified cartilage (ACC) and subchondral bone (SCB) in the third carpal bones (C3) of Standardbred racehorses with naturally-occurring repetitive loading-induced osteoarthritis (OA). Two osteochondral cores were harvested from dorsal sites from each of 15 post-mortem C3 and classified as control or as showing early or advanced OA changes from visual inspection. We re-examined X-ray micro-computed tomography (µCT) image sets for the presence of high-density mineral infill (HDMI) in ACC cracks and possible high-density mineralized protrusions (HDMP) from the ACC mineralizing (tidemark) front (MF) into hyaline articular cartilage (HAC). We hypothesized and we show that 20-µm µCT resolution in 10-mm diameter samples is sufficient to detect HDMI and HDMP: these are lost upon tissue decalcification for routine paraffin wax histology owing to their predominant mineral content. The findings show that µCT is sufficient to discover HDMI and HDMP, which were seen in 2/10 controls, 6/9 early OA and 8/10 advanced OA cases. This is the first report of HDMI and HDMP in the equine carpus and in the Standardbred breed and the first to rely solely on µCT. HDMP are a candidate cause for mechanical tissue destruction in OA.
- "Tissue was harvested at a local abattoir from Standardbred racehorses with a previous racing career, as previously described . A scoring system of the macroscopic cartilage degeneration in the third carpal bones was used to create control (C), early osteoarthritis (EOA) and advanced OA (AOA) groups. "
[Show abstract] [Hide abstract] ABSTRACT: High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline articular cartilage (HAC) were first described in Thoroughbred racehorse fetlock joints and later in Icelandic horse hock joints. We now report them in human material. Whole femoral heads removed at operation for joint replacement or from dissection room cadavers were imaged using magnetic resonance imaging (MRI) dual echo steady state at 0.23 mm resolution, then 26-μm resolution high contrast X-ray microtomography, sectioned and embedded in polymethylmethacrylate, blocks cut and polished and re-imaged with 6-μm resolution X-ray microtomography. Tissue mineralisation density was imaged using backscattered electron SEM (BSE SEM) at 20 kV with uncoated samples. HAC histology was studied by BSE SEM after staining block faces with ammonium triiodide solution. HDMP arise via the extrusion of an unknown mineralisable matrix into clefts in HAC, a process of acellular dystrophic calcification. Their formation may be an extension of a crack self-healing mechanism found in bone and articular calcified cartilage. Mineral concentration exceeds that of articular calcified cartilage and is not uniform. It is probable that they have not been reported previously because they are removed by decalcification with standard protocols. Mineral phase morphology frequently shows the agglomeration of many fine particles into larger concretions. HDMP are surrounded by HAC, are brittle, and show fault lines within them. Dense fragments found within damaged HAC could make a significant contribution to joint destruction. At least larger HDMP can be detected with the best MRI imaging ex vivo.
- "ndrocyte death associated with mechanically injured regions (Lewis et al. 2003; K€ uhn et al. 2004; Novakofski et al. 2014). In a series of in vitro studies of bovine cartilage, Broom and his colleagues have shown that the mode of fracture of HAC and ACC under high loading rates is influenced by previous static creep loading (Thambyah et al. 2012). Lacourt et al. (2012) used both microtomography and decalcified section to quantify cracks in the equine third carpal bone as a natural model of repetitive injuryinduced arthritis. X-ray microtomography was introduced to the bone field by Elliott & Dover (1982, 1984). Although there have been several relevant XMT studies of equine and human joints to date, n"