Post-traumatic Osteoarthritis Model Research Articles

Potential mechanism of alendronate inhibition of osteophyte formation in the rat model of post-traumatic osteoarthritis: evaluation of elemental strontium as a molecular tracer of bone formation

To employ elemental Strontium as a tracer of bone turnover, in the presence (or absence) of the bisphosphonate drug Alendronate, in order to spatially map osteophytogenesis and other bone turnover in rats developing post-traumatic secondary osteoarthritis (PTOA). PTOA was induced in rats by medial meniscectomy surgery. We utilized in-vivo microfocal computed tomography (CT) to follow bony adaptations in groups for 8 weeks after surgery, either with or without alendronate treatment. Electron probe microanalysis (EPMA) was used to detect Strontium incorporation in mineralizing tissues. Histologic studies were conducted on the same samples using Safranin-O/fast green and Tetrachrome staining of decalcified sections to examine articular cartilage health and osteophyte formation at the sites of elemental Strontium deposition. EPMA revealed uniform incorporation of Strontium over actively remodeling trabecular surfaces in normal control rats. That pattern was significantly altered after meniscectomy surgery resulting in greater Strontium signal at the developing osteophyte margins. Alendronate treatment inhibited osteophyte development by 40% and 51% quantified by micro-CT volumetric measurements at 4 and 8 weeks after surgery, respectively. Osteophytes in the alendronate group were more cartilaginous in composition [i.e., lower bone mineral density (BMD)] compared to the untreated group. Histological analysis confirmed the osteophyte inhibitory effect of alendronate, and also verified reduced degeneration of the articular cartilage compared to untreated rats. Our study confirmed that alendronate administration will reduce osteophyte formation in a rat model of post-traumatic osteoarthritis, partially through the inhibition of secondary remodeling of osteophytes. Our study is the first to employ elemental Strontium as a tracer of bone turnover in the pathogenesis of osteoarthritis and to assess the efficacy of bisphosphonate antiresorptive drug interventions on osteophytogenesis.

Improved assessment by quantitative digital histomorphometry of histopathological changes of articular cartilage in a surgical model of post-traumatic osteoarthritis of the knee joint in rats

Purpose: The goal of the study is to evaluate the development of the histopathological changes over time in a model of surgically-induced osteoarthritis of the knee joint in rats and to compare the most frequently used subjective semi-quantitative scoring of joint damage with computerized quantitative digital histomorphometry. Methods: Male skeletally mature Lewis rats (12 weeks of age, n = 10-12 animals/group) were subjected to unilateral transection of the Anterior Cruciate Ligament plus 25% removal of the Medial Meniscus (ACLTpMx model) or sham operated. Three, 7, 28, 56 and 84 days following ACLTpMx the animals were sacrificed and in Hematoxylin-Eosin- and Safranin-O-stained (SO) coronal paraffin sections the degree of joint damage was evaluated by two observers in a blinded fashion using a modified histopathological Mankin-score. For quantitative histomorphometry digital images of the joint were analyzed using the digital image analysis software Integrator VIS System Version Nr. 3.0.15.0 (http://www.visiopharm.com Denmark). The degree of cartilage destruction and subchondral bone sclerosis was quantified by measuring the following parameters: 1. cartilage surface irregularity, 2. cartilage area, 3. chondrocyte number, 4. area of proteoglycan-containing (SO-stained) cartilage and 5. area of sclerotic subchondral bone. Results: The histopathological changes (cartilage fibrillation and erosion, chondrocyte loss, proteoglycan depletion and subchondral bone sclerosis) developed rapidly with increasing severity over time. Already 28 days after ACLTpMx moderate to severe signs of OA were observed. Sham-operated animals did not develop significant OA pathology at any time point. The histomorphometric parameters showed a significant correlation with the corresponding Mankin-subscores. Conclusions: The ACLTpMx model of OA in rats shows similar features as human knee OA regarding anatomical location and the specific histopathological morphology. Quantitative digital histomorphometry of cartilage destruction and subchondral bone sclerosis offers a more objective and less time consuming assessment of OA histopathology in this experimental model than classical histopathological scoring, thus facilitating the preclinical pharmacological testing of potential disease-modifying drugs.

Streaming Potential-Based Arthroscopic Device is Sensitive to Cartilage Changes Immediately Post-Impact in an Equine Cartilage Injury Model

Models of post-traumatic osteoarthritis where early degenerative changes can be monitored are valuable for assessing potential therapeutic strategies. Current methods for evaluating cartilage mechanical properties may not capture the low-grade cartilage changes expected at these earlier time points following injury. In this study, an explant model of cartilage injury was used to determine whether streaming potential measurements by manual indentation could detect cartilage changes immediately following mechanical impact and to compare their sensitivity to biomechanical tests. Impacts were delivered ex vivo, at one of three stress levels, to specific positions on isolated adult equine trochlea. Cartilage properties were assessed by streaming potential measurements, made pre- and post-impact using a commercially available arthroscopic device, and by stress relaxation tests in unconfined compression geometry of isolated cartilage disks, providing the streaming potential integral (SPI), fibril modulus (Ef), matrix modulus (Em), and permeability (k). Histological sections were stained with Safranin-O and adjacent unstained sections examined in polarized light microscopy. Impacts were low, 17.3 ± 2.7 MPa (n = 15), medium, 27.8 ± 8.5 MPa (n = 13), or high, 48.7 ± 12.1 MPa (n = 16), and delivered using a custom-built spring-loaded device with a rise time of approximately 1 ms. SPI was significantly reduced after medium (p = 0.006) and high (p<0.001) impacts. Ef, representing collagen network stiffness, was significantly reduced in high impact samples only (p < 0.001 lateral trochlea, p = 0.042 medial trochlea), where permeability also increased (p = 0.003 lateral trochlea, p = 0.007 medial trochlea). Significant (p < 0.05, n = 68) moderate to strong correlations between SPI and Ef (r = 0.857), Em (r = 0.493), log(k) (r = -0.484), and cartilage thickness (r = -0.804) were detected. Effect sizes were higher for SPI than Ef, Em, and k, indicating greater sensitivity of electromechanical measurements to impact injury compared to purely biomechanical parameters. Histological changes due to impact were limited to the presence of superficial zone damage which increased with impact stress. Non-destructive streaming potential measurements were more sensitive to impact-related articular cartilage changes than biomechanical assessment of isolated samples using stress relaxation tests in unconfined compression geometry. Correlations between electromechanical and biomechanical methods further support the relationship between non-destructive electromechanical measurements and intrinsic cartilage properties.