GDF8 inhibition enhances musculoskeletal recovery and mitigates posttraumatic osteoarthritis following joint injury

The Efficacy of Blood Flow Restriction Training to Improve Quadriceps Muscle Function after Anterior Cruciate Ligament Reconstruction

BACKGROUND

Blood flow restriction training (BFRT) is a popular rehabilitation intervention after anterior cruciate ligament reconstruction (ACLR). However, there are a lack of clinical trials establishing the efficacy of using BFRT during rehabilitation to improve quadriceps muscle function.

PURPOSE

The purpose of this study is to evaluate the efficacy of blood flow restriction training to improve quadriceps muscle strength, morphology, and physiology, and knee biomechanics in individuals after ACLR in a double-blind, randomized, placebo-controlled clinical trial (NCT03364647).

METHODS

Forty-eight athletes (20 females/28 males) were randomly assigned to low-load strength training with active BFRT or standard of care strength training with a sham unit. Treatment occurred for 1-month pre-surgery and 4 to 5 months post-surgery with both groups following the same standard rehabilitation protocol. Outcome variables were measured at baseline and 4 to 5 months post-surgery. Quadriceps muscle strength (isometric and isokinetic peak torque and rate of torque development) was measured on an isokinetic dynamometer. Quadriceps muscle morphology (physiological cross-sectional area, fibrosis) was determined using magnetic resonance imaging. Quadriceps muscle physiology (fiber type, fiber cross-sectional area, satellite cell abundance, collagen content, fibrogenic/adipogenic progenitor cells) was evaluated with muscle biopsies of the vastus lateralis. Knee extensor moment and knee flexion angle were measured via three-dimensional gait analysis. Change scores were calculated as: post-intervention - baseline. Two-sample t -tests were then used to assess between-group differences for each outcome variable.

RESULTS

No significant between-group differences were found for any outcome variable.

CONCLUSIONS

The addition of BFRT to a rehabilitation program for athletes pre- and post-ACLR was no more effective than standard rehabilitation for improving quadriceps muscle function. Clinicians should consider the value of BFRT relative to the cost, time, and discomfort for patients in light of these results.

CSF1-R inhibition attenuates posttraumatic osteoarthritis and quadriceps atrophy following ligament injury

Knee osteoarthritis contributes substantially to worldwide disability. Post-traumatic osteoarthritis (PTOA) develops secondary to joint injury, such as ligament rupture, and there is increasing evidence suggesting a key role for inflammation in the aetiology of PTOA and associated functional deficits. Colony stimulating factor 1 receptor (CSF1-R) has been implicated in the pathogenesis of musculoskeletal degeneration following anterior cruciate ligament (ACL) injury. We sought to assess the efficacy of CSF1-R inhibition to mitigate muscle and joint pathology in a mouse model of PTOA. Four-month-old mice were randomized to receive a CSF1-R inhibitor and studied for 7 or 28 days after joint injury. Additionally, we profiled synovial fluid samples for CSF1-R from patients with injury to their ACL. Transcriptomic analysis of quadriceps muscle and articular cartilage in CSF1-R inhibitor-treated animals at 7 days after injury revealed elevated chondrocyte differentiation within articular cartilage and enhanced metabolic and contractile gene expression within skeletal muscle. At 28 days post-injury, CSF1-R inhibition attenuated PTOA severity and mitigated skeletal muscle atrophy. Patient synovial fluid CSF1-R levels correlated with matrix metalloproteinase 13, a prognostic marker and molecular effector of PTOA. Our findings support an opportunity for CSF1-R targeting to mitigate the severity of PTOA and muscle atrophy after joint injury. KEY POINTS: Posttraumatic osteoarthritis (PTOA) of the knee commonly results from direct injury to the joint, which is characterized by pain, weakness, and disability. Induction of colony stimulating factor one receptor (CSF1-R) is positively associated with knee trauma severity, and the initial acute inflammatory state suppresses muscle recovery and degrades articular cartilage. Skeletal muscle and articular cartilage transcriptomic response following direct joint injury in a murine model of PTOA is rescued by pharmacological inhibition of CSF1-R. CSF1-R inhibition mitigated skeletal muscle atrophy and attenuated PTOA severity and synovitis. Patient synovial fluid CSF1-R levels correlated with matrix metalloproteinase 13, a prognostic marker and molecular effector of PTOA, offering further evidence for CSF1-R as a therapeutic target across musculoskeletal tissues after injury.

Obesity, Osteoarthritis, and Myokines: Balancing Weight Management Strategies, Myokine Regulation, and Muscle Health

Obesity and osteoarthritis (OA) are increasingly prevalent conditions that are intricately linked, with each exacerbating the other's pathogenesis and worsening patient outcomes. This review explores the dual impact of obesity on OA, highlighting the role of excessive weight in aggravating joint degeneration and the limitations OA imposes on physical activity, which further perpetuates obesity. The role of muscle tissue, particularly the release of myokines during physical activity, is examined in the context of OA and obesity. Myokines such as irisin, IL-6, and myostatin are discussed for their roles in metabolic regulation, inflammation, and tissue repair, offering insights into their potential therapeutic targets. This review emphasizes the importance of supervised weight management methods in parallel with muscle rehabilitation in improving joint health and metabolic balance. The potential for myokine modulation through targeted exercise and weight loss interventions to mitigate the adverse effects of obesity and OA is also discussed, suggesting avenues for future research and therapy development to reduce the burden of these chronic conditions.

ACL injury management: a comprehensive review of novel biotherapeutics

The anterior cruciate ligament (ACL) is integral to the stability of the knee joint, serving to limit anterior tibial translation and regulate rotational movements. ACL injuries are among the most common and debilitating forms of knee trauma, often resulting in joint effusion, muscular atrophy, and diminished athletic capabilities. Despite the established efficacy of ACL reconstruction as the standard treatment, it is not uniformly successful. Consequently, there is a growing interest in novel biotherapeutic interventions as potential alternatives. This comprehensive review examines the latest advancements in ACL biotherapy, encompassing the application of hyaluronic acid, self-assembled short peptides, growth factors, stem cell therapy, gene therapy, platelet-rich plasma therapy, bone marrow aspirate concentrate cells, extracorporeal shock wave, electrical stimulation and cross bracing protocol. The collective aim of these innovative treatments is to facilitate the restoration of the ACL's native biological and biomechanical integrity, with the ultimate goal of enhancing clinical outcomes and the functional recovery of affected individuals.

Overexpression of manganese superoxide dismutase mitigates ACL injury-induced muscle atrophy, weakness and oxidative damage

Oxidative stress has been implicated in the etiology of skeletal muscle weakness following joint injury. We investigated longitudinal patient muscle samples following knee injury (anterior cruciate ligament tear). Following injury, transcriptomic analysis revealed downregulation of mitochondrial metabolism-related gene networks, which were supported by reduced mitochondrial respiratory flux rates. Additionally, enrichment of reactive oxygen species (ROS)-related pathways were upregulated in muscle following knee injury, and further investigation unveiled marked oxidative damage in a progressive manner following injury and surgical reconstruction. We then investigated whether antioxidant protection is effective in preventing muscle atrophy and weakness after knee injury in mice that overexpress Mn-superoxide dismutase (MnSOD+/-). MnSOD+/- mice showed attenuated oxidative damage, atrophy, and muscle weakness compared to wild type littermate controls following ACL transection surgery. Taken together, our results indicate that ROS-related damage is a causative mechanism of muscle dysfunction after knee injury, and that mitochondrial antioxidant protection may hold promise as a therapeutic target to prevent weakness and development of disability.