Clinical-like cryotherapy improves gait function and reduces synovial inflammation in rats with knee osteoarthritis

Abstract

Purpose: To evaluate the effects of clinical-like cryotherapy on gait function and synovial inflammation in rats with knee osteoarthritis (KOA) induced by anterior cruciate ligament transection (ACLT). Methods: The experimental protocol was in accordance with the National Guide for the Care and Use of Laboratory Animals (National Research Council, 1996). All procedures were approved by the institutional Ethics Committee and conducted by trained professionals blinded to the identity of the experimental groups. Two-month-old male Wistarrats (n=32; 297±25 g) were studied. The animals were housed in pathogen-free conditions at 24ºC±1°C under a reverse light cycle (12/12 light/dark) with free access to standard rat chow and water. Animals were randomly allocated into four groups (n=8 per group): Control (without surgery and intervention); ACLT knee surgery (KOA); ACLT knee surgery submitted to ice pack (KOA+Cryotherapy), and ACLT knee surgery submitted to a sand pack (KOA+Placebo). An adapted ACLT-induced KOA model was used. The groups were analyzed one day before and 60 days after ACLT surgery from the least to the most stressful tests: skin temperature (thermography), gait test (paw print), thermal response threshold (hotplate) and swelling (digital caliper). Next, both the KOA+Cryotherapy and KOA+Placebo groups underwent the interventions (ice pack or sand pack) twice a day, for 20 min each, over five consecutive days (from the 61st to the 65th days). The four groups were then assessed on the 66th day, and after euthanasia, the synovial fluid (account of leukocytes and cytokine levels) and synovial membrane (histopathological analysis) were collected (Figure 1). Results: Among the KOA groups, only the Cryotherapy group increased their paw contact area (P=0.004; 14%) after interventions, with no difference in relation to the Control group [Figure 2(A)]. Cryotherapy decreased the number of leukocytes (P<0.001; ≥95.0%; Figure 3) and cytokine levels (P<0.001; ≥55%; Figure 4) in synovial fluid in relation to the KOA and Placebo groups. There were no differences in synovial score and fibrosis in the synovial membrane of KOA groups. Conclusions: Clinical-like cryotherapy improves the gait function and reduces the number of leukocytes and inflammatory cytokines in synovial fluid of rats with ACLT-induced KOA. These results provide new evidence of the beneficial effects of cryotherapy and suggest it can be used as a non-pharmacological and complementary treatment to control joint inflammation of KOA.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)