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Standardized Histomorphometric Evaluation of Osteoarthritis in a Surgical Mouse Model
Published on: May 6, 2020
Post-Traumatic Osteoarthritis in Mice Following Mechanical Injury to the Synovial Joint
Muhammad Farooq Rai1,2, Xin Duan1, James D Quirk3
1Department of Orthopaedic Surgery, Musculoskeletal Research Center, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, MO, USA.
Abstract:
We investigated the spectrum of lesions characteristic of post-traumatic osteoarthritis (PTOA) across the knee joint in response to mechanical injury. We hypothesized that alteration in knee joint stability in mice reproduces molecular and structural features of PTOA that would suggest potential therapeutic targets in humans. The right knees of eight-week old male mice from two recombinant inbred lines (LGXSM-6 and LGXSM-33) were subjected to axial tibial compression. Three separate loading magnitudes were applied: 6N, 9N, and 12N. Left knees served as non-loaded controls. Mice were sacrificed at 5, 9, 14, 28, and 56 days post-loading and whole knee joint changes were assessed by histology, immunostaining, micro-CT, and magnetic resonance imaging. We observed that tibial compression disrupted joint stability by rupturing the anterior cruciate ligament (except for 6N) and instigated a cascade of temporal and topographical features of PTOA. These features included cartilage extracellular matrix loss without proteoglycan replacement, chondrocyte apoptosis at day 5, synovitis present at day 14, osteophytes, ectopic calcification, and meniscus pathology. These findings provide a plausible model and a whole-joint approach for how joint injury in humans leads to PTOA. Chondrocyte apoptosis, synovitis, and ectopic calcification appear to be targets for potential therapeutic intervention.
Insights
Mechanical knee injury in mice causes post-traumatic osteoarthritis (PTOA) features, including cartilage damage and inflammation. This study identifies chondrocyte apoptosis, synovitis, and ectopic calcification as potential therapeutic targets for PTOA.
Area of Science:
- Orthopedics
- Biomedical Engineering
- Musculoskeletal Research
Background:
- Post-traumatic osteoarthritis (PTOA) develops after joint injury.
- Understanding PTOA's early molecular and structural changes is crucial for developing treatments.
- Existing models may not fully capture the whole-joint pathology of PTOA.
Purpose of the Study:
- To investigate the spectrum of lesions characteristic of PTOA in the knee joint following mechanical injury.
- To determine if altered knee joint stability in mice reproduces molecular and structural features of PTOA relevant to human therapeutics.
- To identify potential therapeutic targets for PTOA.
Main Methods:
- Mechanical axial tibial compression was applied to mouse knee joints at varying forces (6N, 9N, 12N).
- Histology, immunostaining, micro-CT, and MRI were used to assess whole knee joint changes over 56 days.
- Anterior cruciate ligament rupture was induced by loading, except at 6N.
Main Results:
- Tibial compression disrupted joint stability, causing anterior cruciate ligament rupture and initiating PTOA features.
- Observed PTOA features included cartilage matrix loss, chondrocyte apoptosis (day 5), synovitis (day 14), osteophytes, ectopic calcification, and meniscus pathology.
- A temporal and topographical cascade of PTOA lesions was documented across the entire joint.
Conclusions:
- This study presents a plausible whole-joint model for PTOA development after mechanical injury.
- Chondrocyte apoptosis, synovitis, and ectopic calcification are identified as key pathological events and potential therapeutic targets.
- The findings support further investigation into interventions targeting these specific pathways for PTOA treatment.
