Maresin 1 Repletion Improves Muscle Regeneration After Volumetric Muscle Loss

The acute traumatic or surgical loss of skeletal muscle, known as volumetric muscle loss (VML), is a devastating type of injury that results in exacerbated and persistent inflammation followed by fibrosis. The mechanisms that mediate the magnitude and duration of the inflammatory response and ensuing fibrosis after VML remain understudied, and as such, the development of regenerative therapies has been limited. To address this need, we profiled how lipid mediators, which are potent regulators of the immune response after injury, varied with VML injuries that heal or result in fibrosis. We observed that non-healing VML injuries displayed increased pro-inflammatory eicosanoids and a lack of pro-resolving lipid mediators. Treatment of VML with a pro-resolving lipid mediator synthesized from docosahexaenoic acid, called Maresin 1, ameliorated fibrosis through reduction of neutrophils and macrophages and enhanced recovery of muscle strength. These results expand our knowledge of the dysregulated immune response that develops after VML and identify a novel immuno-regenerative therapeutic modality in Maresin 1. Overall design: Bilateral 2mm biopsy punch defects were administered to the tibialis anterior muscles of young mice, then treated with maresin 1 or vehicle on days 1, 3, and 5 post injury. At 7 days post injury, mice were humanely euthanized, TAs extracted, pooled according to treatment, digested into single cell suspensions, labeled with 10x genomics cell multiplexing oligos (one per treatment), pooled, FACSed to remove debris and dead cells (7-AAD positive), then analyzed by single cell RNA sequencing. TA muscles from mice were given a VML injury and treated with either Maresin 1 or Vehicle at 1,3,5 dpi. Muscles were collected at 7 dpi and digested into single cell suspensions and processed for single cell sequencing.