Systemic Effects of Vascular Photobiomodulation on Early Macrophage Recruitment During Skeletal Muscle Repair

Muscle injuries involve a complex inflammatory response in which macrophages are essential for proper tissue repair. Dysregulation of this process can impair regeneration. This study investigated the effects of vascular photobiomodulation (VPBM), a non-invasive therapy applied via the caudal vein/artery, on macrophage dynamics in acute skeletal muscle injury. Wistar rats were divided into Control, Injury, Pre-VPBM+Injury, and Injury+Post-VPBM groups. VPBM (780 nm, 40 mW, 3.2 J) was applied preventively or therapeutically. Animals were euthanized on days 1, 2, 5, and 7 post-injury for CD68⁺ and CD206⁺ immunostaining. CD68⁺ cells peaked on day 1 in the Pre-VPBM+Injury group, while the Injury group maintained higher levels at day 7. CD206⁺ cells were elevated early in both VPBM groups, especially Pre-VPBM. On day 7, CD206⁺ remained higher in the Injury group, indicating delayed resolution. In summary, the study demonstrates that preventive VPBM application accelerates macrophage recruitment and promotes a pro-regenerative inflammatory response.