Dynamic lipid mediator changes support macrophage subtype transitions during muscle regeneration

Muscle damage elicits a sterile immune response that facilitates complete regeneration. Here, we utilized mass spectrometry-based lipidomics to map the mediator lipidome during the transition from inflammation to resolution and regeneration in skeletal muscle injury. We observed the temporal regulation of glycerophospholipids and the production of pro-inflammatory (e.g., leukotrienes, prostaglandins) and specialized pro-resolving (e.g., resolvins, lipoxins) lipid mediators, which were modulated by ibuprofen. These time-dependent profiles were recapitulated in sorted neutrophils and Ly6C(hi) and Ly6C(lo) muscle-infiltrating macrophages, with a distinct pro-resolving signature observed in Ly6C(lo) macrophages. RNA-seq of macrophages stimulated with resolvin D2 (RvD2) showed similarities to transcriptional changes found during the temporal Ly6C(hi) to Ly6C(lo) macrophage transition. In vivo, RvD2 increased Ly6C(lo) macrophages and functional improvement of the regenerating muscle. These results reveal dynamic lipid mediator signatures of innate immune cells and provide a proof-of-concept for their exploitable effector roles in muscle regeneration.