Benefits of electroacupuncture and a swimming association when compared with isolated protocols in an osteoarthritis model

Abstract

Background and aim: Osteoarthritis (OA) is characterized by pain and inflammation. Electroacupuncture (EA) and swimming (SW) are non-pharmacological interventions recommended for treating OA. The study evaluated the benefits of electroacupuncture (EA) and swimming (SW) association when compared with isolated protocols in an OA rodent model. Experimental.

Procedures: An ankle monoarthritis model was induced in rats by applying Complete Freund's Adjuvant (CFA). After seven days of induced OA, the groups were submitted to EA (ST36 and the GB 30 Acupoint), SW, or the EA + SW protocol. The nociceptive behavior was measured by the Von Frey test, the Cold Stimulation test, and the Paw Flick Immersion test. Inflammatory activity was evaluated by measuring TNF levels, myeloperoxidase, NAGase, immunological parameters and the histology from the subcutaneous tissue.

Results: Compared to CFA group, EA decreased the nociceptive scores in the cold stimulation test (p < 0.05), and it also increased the latency time in thermal cold (p < 0.01) and heat hyperalgesia (p < 0.001). Also, EA reduced NAGase (p < 0.01). SW reduced the edema (p < 0.05) and did not increase the inflammatory infiltrates or congestion, neither in the histological measurements nor by analyzing the levels of TNF. The association of EA + SW decreased the neutrophils and the monocytes, MPO (p < 0.05), and the glutamate levels in the cerebrospinal fluid (CSF, p < 0.001).

Conclusion: There were statistical differences between combination therapy and monotherapy as seen by the inflammatory parameters, which could be associate to the delay of the chronification osteoarthritis retardation. However, EA + SW did not show benefits when compared to isolated protocols in nociceptive behavior.

Keywords: Electroacupuncture; Non-pharmacological approaches; Pain behavior; Swimming; osteoarthritis.

Graphical abstract

Fig. 1

General schedule of the behavioral assessment that was used in the present study. The nociceptive behavior was evaluated at the baseline, at the acute phase (7th day), and at the chronic phase (20th day), when evaluating the ankle osteoarthritis model. EA: electroacupuncture; SW: swimming.

Fig. 2

Effects of EA, SW, and the associated treatments in the paw edema (a); mechanical allodynia (b); cold allodynia (c) and heat hyperalgesia (d). The measurements were done after 10 intervention sessions of EA, SW, and the associated treatments. (∗∗∗, ∗∗, ∗) indicate a significant difference compared to the saline group (p < 0.001, p < 0.01, p < 0.05). (+++, ++, +) indicates a significant difference compared to the CFA group (p < 0.001, p < 0.01, p < 0.05). (ooo) indicates a significant difference compared to the EA group (p < 0.001). ($$) indicates a significant difference compared to the EA + SW group (p < 0.01). Each column represents the mean and SEM values that were obtained from 6 animals. Statistical analyses were performed using Two-Way ANOVA, followed by Bonferroni's post-hoc test.

Fig. 3

Glutamate levels in CSF (a); Myeloperoxidase (b); NAGase values (c) after 10 intervention sessions of eletroacupuncture (EA), swimming (SW) or the association. (∗∗∗, ∗∗, ∗) indicates a significant difference compared to the saline group (p < 0.001, p < 0.01, p < 0.05). (ooo, o) indicates a significant difference compared to the EA group (p < 0.001, p < 0.05). ($$$, $) indicates a significant difference compared to the EA + SW group (p < 0.001, p < 0.05). (&&&) indicates a significant difference compared to the SW group (p < 0.001). Each column represents the mean ± standard error of 6 animals. One-Way ANOVA was used, followed by Dunnett's Multiple Comparison Test.

Fig. 4

Results of the qualitative analysis of the immunohistochemical expression of proinflammatory cytokine TNF in the subcutaneous tissue in the different groups that were evaluated at the end of the experiments. The arrows indicate the areas of concentration of the TNF. Saline Group (A), CFA (B), EA Group (C), SW Group (D), and EA + SW Group (E). Scale bar 50 μm.

Fig. 5

Histological section of the subcutaneous left ankle tissue of the animals after 10 sessions of interventions: Saline (A_1,2,3), CFA (B_1,2,3), EA (C_1,2,3), SW (D_1,2,3), and EA + SW (E_1,2,3). The black arrows indicate the infiltrate, and the empty arrows indicate congestion. 1 = 4x, 2 = 10x, and 3 = 40x magnification by the HE coloration.