Effect of stretching on inflammation in a subcutaneous carrageenan mouse model analyzed at single‐cell resolution

Abstract Understanding the factors that influence the biological response to inflammation is crucial, due to its involvement in physiological and pathological processes, including tissue repair/healing, cancer, infections, and autoimmune diseases. We have previously demonstrated that in vivo stretching can reduce inflammation and increase local pro‐resolving lipid mediators in rats, suggesting a direct mechanical effect on inflammation resolution. Here we aimed to explore further the effects of stretching at the cellular/molecular level in a mouse subcutaneous carrageenan‐inflammation model. Stretching for 10 min twice a day reduced inflammation, increased the production of pro‐resolving mediator pathway intermediate 17‐HDHA at 48 h postcarrageenan injection, and decreased both pro‐resolving and pro‐inflammatory mediators (e.g., PGE 2 and PGD 2 ) at 96 h. Single‐cell RNA sequencing analysis of inflammatory lesions at 96 h showed that stretching increased the expression of both pro‐inflammatory ( Nos2 ) and pro‐resolution ( Arg1 ) genes in M1 and M2 macrophages at 96 h. An intercellular communication analysis predicted specific ligand–receptor interactions orchestrated by neutrophils and M2a macrophages, suggesting a continuous neutrophil presence recruiting immune cells such as activated macrophages to contain the antigen while promoting resolution and preserving tissue homeostasis.