2025- MMT-induced Osteoarthritis in Rats- Behavioral Phenotype- Cohort 001

Assessment of the behavioral pain phenotype in rats following medial meniscal transection (MMT) model of osteoarthritis. Baseline measures were collected in weight bearing, Von Frey, and catwalk tests. Starting 7 weeks after injury, rats were tested for signs of pain or motor dysfunction in the same tests. For the weight bearing assay (Dynamic Weight Bearing, Bioseb), rats were placed on the sensor for 5 min and the amount of pressure (g) and paw area (cm2) was measured for each paw. For Von Frey (handheld electronic Von Frey, Ugo Basile), 3 measurements were taken from each paw (max g of force) and averaged for analysis. For catwalk (Catwalk XT, Noldus), rats traversed the glass catwalk 5 times and values were averaged for analysis. These tests were repeated up to 17 weeks post-surgery. No notable pain or motor phenotype was detected. Sprague Dawley rats were relatively young when the surgery was performed (~275-300 grams), and we hypothesize that they all recovered from the surgery prior to the onset of testing, and therefore no chronic pain phenotype was detected. Future testing will involve using older rats at the time of surgery to minimize the potential healing observed in the younger rats.