Knee immobilization reproduces key arthrofibrotic phenotypes in mice

Abstract

Aims As has been shown in larger animal models, knee immobilization can lead to arthrofibrotic phenotypes. Our study included 168 C57BL/6J female mice, with 24 serving as controls, and 144 undergoing a knee procedure to induce a contracture without osteoarthritis (OA). Methods Experimental knees were immobilized for either four weeks (72 mice) or eight weeks (72 mice), followed by a remobilization period of zero weeks (24 mice), two weeks (24 mice), or four weeks (24 mice) after suture removal. Half of the experimental knees also received an intra-articular injury. Biomechanical data were collected to measure passive extension angle (PEA). Histological data measuring area and thickness of posterior and anterior knee capsules were collected from knee sections. Results Experimental knees immobilized for four weeks demonstrated mean PEAs of 141°, 72°, and 79° after zero, two, and four weeks of remobilization (n = 6 per group), respectively. Experimental knees demonstrated reduced PEAs after two weeks (p < 0.001) and four weeks (p < 0.0001) of remobilization compared to controls. Following eight weeks of immobilization, experimental knees exhibited mean PEAs of 82°, 73°, and 72° after zero, two, and four weeks of remobilization, respectively. Histological analysis demonstrated no cartilage degeneration. Similar trends in biomechanical and histological properties were observed when intra-articular violation was introduced. Conclusion This study established a novel mouse model of robust knee contracture without evidence of OA. This was appreciated consistently after eight weeks of immobilization and was irrespective of length of remobilization. As such, this arthrofibrotic model provides opportunities to investigate molecular pathways and therapeutic strategies. Cite this article: Bone Joint Res 2023;12(1):58–71.

AdipoRon reduces TGFβ1‐mediated collagen deposition in vitro and alleviates knee stiffness in vivo

“…While our group has developed arthrofibrosis models in rabbits (Nesterenko et al, 2009), rats (Owen, Dagneaux, et al, 2021), and mice (Dagneaux et al, 2023), the present investigation evaluated the therapeutic potential of AdipoRon in mice due to established therapeutic regimens (i.e., dose, interval, and route of administration) (Lee et al, 2021;Nicolas et al, 2018Nicolas et al, , 2020Sun et al, 2023;Takenaga et al, 2021;Tarkhnishvili et al, 2022;Zheng et al, 2019).…”

“…We recently developed a mouse model of robust knee contracture that reproduces key arthrofibrotic phenotypes (i.e., knee stiffness) (Dagneaux et al, 2023). Our model involves a percutaneous technique to immobilize the experimental knee in 150° of flexion with a nonabsorbable suture for a period of time (typically 4–8 weeks).…”

“…Alternatively, mice can be sacrificed immediately after the immobilization period (i.e., no remobilization period), suture removed postmortem , and subjected to phenotyping. As described in our original work (Dagneaux et al, 2023), both surgical interventions are performed under general anesthesia using isoflurane. Cefazolin (30 mg/kg) and buprenorphine ER‐LAB (1.0 mg/kg) are administered subcutaneously as antibiotic prophylaxis and preoperative analgesia, respectively.…”

“…Each treatment group ( n = 16) was then further divided into a no remobilization cohort (i.e., 6 weeks of immobilization and 0 weeks of remobilization, n = 8 per group) and a 4‐week remobilization group (i.e., 6 weeks of immobilization and 4 weeks of remobilization, remobilization cohort, n = 8 per group). As highlighted in the original mouse knee contracture model (Dagneaux et al, 2023), a power analysis revealed that six mice were required in each group to detect an effect difference of 10° with a standard deviation (SD) of 8°. Due to potential complications from daily vehicle and AdipoRon injections, two additional mice were included in each group.…”

“…At sacrifice, biomechanical data were collected on the limbs using a dynamic load cell device that captures the PEA at a torque of 0.4 N cm (Dagneaux et al, 2023). To confirm knee stiffness in our mouse model, the PEAs of experimental (right) and contralateral (left) knees of vehicle-injected groups were compared in the no remobilization cohort (6 weeks immobilization + 0 weeks remobilization) and the remobilization cohort (6 weeks immobilization + 4 weeks remobilization) (Figure 8).…”