Gene Therapy for Follistatin Mitigates Systemic Metabolic Inflammation and Post-Traumatic Osteoarthritis in High-Fat Diet-Induced Obese Mice

Obesity-associated inflammation and loss of muscle function play critical roles in the development of osteoarthritis (OA); thus, therapies that target muscle tissue may provide novel approaches to restoring metabolic and biomechanical dysfunction associated with obesity. Recent studies indicate that follistatin (FST), a protein which binds myostatin and activin, may have the potential to enhance muscle formation while neutralizing inflammation induced by these proteins. Here, we hypothesized that adeno-associated virus (AAV9) delivery of FST will enhance muscle formation and mitigate metabolic inflammation and knee OA caused by a high fat diet in mice. Obese mice receiving AAV-mediated FST delivery exhibited decreased inflammatory adipokines and cytokines systemically in the serum as well as locally in the joint synovial fluid. Regardless of diet, mice receiving FST gene therapy were protected from post-traumatic OA and bone remodeling induced by joint injury. While obesity disrupted the mitochondrial oxidative phosphorylation (OXPHOS) system in adipocytes, gene therapy for FST restored the key proteins involved in mitochondrial biogenesis, such as PPAR{gamma} coactivator 1 and AKT protein kinase 1, leading to the browning of white adipose tissue. Taken together, these findings suggest that FST gene therapy may provide a multifactorial therapeutic approach for injury-induced OA and metabolic inflammation in obesity.