Combined angiogenic and hypertrophic gene therapy enhances skeletal muscle growth

Skeletal muscle atrophy in response to pathophysiological stimuli or disuse includes loss of muscle mass and strength. Targeting signaling pathways regulating muscle growth can counteract muscle loss, but also unwanted side effects on muscle vascularization, oxidative metabolism, and exercise tolerance have been reported. Here, we investigated whether combined induction of angiogenesis and muscle hypertrophy can promote physiological muscle growth and improve muscle function to overcome the limitations of current hypertrophic treatments. We used myostatin propeptide (Pro-MSTN) and vascular endothelial growth factor B (VEGF-B) gene therapies to increase muscle size and angiogenesis, respectively. Intramuscular and systemic adeno-associated viral vector (AAV) delivery was used to study their effects alone and in combination in healthy and diabetic mice. Single-cell RNA sequencing was used to investigate the effects on different cell types and on intercellular communication in the healthy mice. We demonstrate that in the healthy mice, the intramuscular delivery of VEGF-B rescued Pro-MSTN-induced capillary rarefaction and enhanced muscle growth in the combination group (VEGF-B + Pro-MSTN). The systemic combination treatment also improved body composition in the healthy mice and increased muscle mass and grip strength in the diabetic mouse model. The single-cell RNA sequencing data showed that among the nonmyocytes, endothelial cells and pericytes responded the most to both treatments resulting in enhanced intercellular communication. Our findings demonstrate beneficial effects of the combined gene delivery of Pro-MSTN and VEGF-B on muscle growth and body composition. The results also decipher the contribution of various cell types and their cross talk in skeletal muscle growth.NEW & NOTEWORTHY We used intramuscular and systemic adeno-associated viral vector (AAV) gene delivery of myostatin propeptide (Pro-MSTN) and vascular endothelial growth factor B (VEGF-B) to induce muscle growth and angiogenesis in skeletal muscle. The intramuscular delivery of VEGF-B and Pro-MSTN in combination enhanced skeletal muscle growth and rescued vascularization when compared with Pro-MSTN alone. Single-cell RNA sequencing data showed that the treatments had the greatest effect on endothelial cells and pericytes. The combination treatment also improved body composition and muscle mass in diabetic mice, when delivered systemically.