Pro-resolving Annexin A1-derived peptide Ac2-26 reduces nociception and mitigates joint damage in experimental osteoarthritis

Abstract Objectives We investigated whether treatment with Annexin A1 (AnxA1) ameliorated joint nociception and tissue damage in an experimental osteoarthritis (OA) model. Design: OA was induced by injection of collagenase into the tibiofemoral joint of wild-type (WT) and AnxA1-deficient male Balb/c mice. The control group received saline. Groups of WT mice were treated weekly with Ac2-26, an active peptide corresponding to the N-terminal region of AnxA1, in the affected joint. Mechanical nociception was analyzed weekly, and samples were collected 6 weeks after OA induction to analyze histopathology and markers of joint damage by qPCR and flow cytometry. Results The expression of Anxa1 is upregulated in the joints at the 1st and 3rd week and returned to the basal level at the 6th week after OA induction. AnxA1-deficient mice had persistent nociception and increased joint inflammation when compared to WT mice, although both groups had comparable cartilage damage. In WT mice, the treatment with Ac2-26 decreased joint nociception, tissue damage, and the expression of metalloproteinase-3 in the joint tissue, even when started in the 3rd week after induction of OA. Collagenase injection increased the number of FAP⁺CD90⁻ fibroblast-like and CX3CR1⁺macrophage-like synoviocytes expressing RANKL when compared to saline-injected mice. Treatment with Ac2-26 normalized the latter parameters. Conclusions AnxA1 and Ac2-26 are promising molecules that regulate key processes in OA, effectively mitigating tissue damage and dysfunction in a model of OA in mice.