Pathology of the Calcified Zone of Articular Cartilage in Post-Traumatic Osteoarthritis in Rat Knees

Abstract

ObjectivesThis study aimed to investigate the pathology occurring at the calcified zone of articular cartilage (CZC) in the joints afflicted with post-traumatic osteoarthritis (PTOA).MethodsRats underwent bilateral anterior cruciate ligament (ACL) transection and medial meniscectomy to induce PTOA. Sham surgery was performed on another five rats to serve as controls. The rats were euthanized after four weeks of surgery and tibial plateaus were dissected for histology. The pathology of PTOA, CZC area and the tidemark roughness at six pre-defined locations on the tibial plateaus were quantified by histomorphometry.ResultsPTOA developed in the knees, generally more severe at the medial plateau than the lateral plateau, of rats in the experimental group. The CZC area was unchanged in the PTOA joints, but the topographic variations of CZC areas that presented in the control knees were reduced in the PTOA joints. The tidemark roughness decreased in areas of the medial plateau of PTOA joints and that was inversely correlated with the Mankin’s score of PTOA pathology.ConclusionReduced tidemark roughness and unchanged CZC area differentiate PTOA from primary osteoarthritis, which is generally believed to have the opposite pathology at CZC, and may contribute to the distinct disease progression of the two entities of arthropathy.

3D morphometric analysis of calcified cartilage properties using micro-computed tomography

“…First, the high frequency roughness disappears (entrapment of the chondrocytes), then the low frequency undulations start to appear (uneven increase in calcification) and in the end (after the cartilage is eroded), the tidemark is completely smoothed by physical force of the bones grinding together. When comparing our results with the literature, similar results with TMR have been reported in histomorphometric analyses of rat CC in a post-traumatic OA model 31 . This previous study found that the TMR decreased in tibial plateaus of rats with increasing OA progression (Mankin et al 45 score).…”

“…To date, most studies investigating the tidemark or channels through the calcified layer are done from 5 mm thick histological sections 13,30,31 . For instance, studies have been conducted to assess how the tidemark roughness (TMR) is altered as a function of OA 30,31 . Roughness of a 2D surface can be easily calculated as a ratio between the true length of the surface and the projected length of that surface, where the minimum value of one defines a perfectly smooth surface 32 .…”

Controlling joint instability delays the degeneration of articular cartilage in a rat model

“…Sample scores were evaluated by two independent observers. Moreover, we performed an analysis of histological characteristics, including cartilage thickness, roughness, and relative staining intensity, using Safranin O and fast green 25 . For details see Supplementary material and methods.…”

Use of pre‐clinical surgically induced models to understand biomechanical and biological consequences of PTOA development

“…Meniscal injuries are highly prevalent and often treated by arthroscopic meniscal debridement or Mx . Mx increases the relative risk for PTOA in humans sixfold and in animal models has been validated to lead to PTOA . The Mx model is used to study biomechanical destabilization and biological changes to the contact surfaces.…”