Efeito da fotobiomodulação associada ao uso de dexametasona na sensibilidade e resistência mecânica da cartilagem do joelho, em modelo experimental de artrite reumatoide

Abstract

Rheumatoid arthritis (RA) is a chronic, autoimmune, systemic, and progressive disease that causes irreversible joint damage. The conventional treatment is pharmacological, typically involving anti-inflammatory drugs, though these are often associated with adverse effects. Photobiomodulation therapy (PBM) has been linked to the modulation of inflammation and pain and represents a potential therapeutic alternative for RA. This study aimed to evaluate the effects of PBM on pain modulation—through mechanical allodynia—tissue repair, assessed by collagen proportion, and functional recovery, evaluated via biomechanical analysis of cartilage, in an experimental model of RA induced in rats. Methodology: Male Wistar rats were divided into five groups: healthy controls without RA (CTL), RA-induced without treatment (NT), RA treated with PBM applied locally to the knee (PBM), RA treated with dexamethasone (DEX), and RA treated with a combination of PBM and dexamethasone (PBM+DEX). RA was induced using injections of type II collagen and Freund’s adjuvant. Treatments were administered three times per week for one month: PBM (808 nm; 4 J; 100 mW) applied locally or intraperitoneal dexamethasone. Mechanical allodynia was assessed weekly. At the end of the treatment, animals were euthanized, and cartilage was harvested for biomechanical and histological analyses. Results: All RA groups showed a significant reduction in resistance and deformation capacity compared to the CTL group (p < 0.001). Only the PBM group exhibited a significant improvement in deformation capacity compared to the NT group. All treated groups showed an increased proportion of total collagen compared to the NT group (p < 0.05). The PBM group was the only one to show consistent improvement in mechanical allodynia across all time points compared to the other RA groups (p < 0.01). Conclusion: Local PBM irradiation promotes the maintenance of collagen proportion and improves the tissue’s deformation capacity. While combined PBM+DEX therapy maintained the collagen proportion, it did not provide additional benefits regarding mechanical properties or pain sensitivity as assessed by the mechanical allodynia test.