Effect of Osteopathic Manipulation on Interstitial Concentrations of Inflammatory Markers

Abstract

Little is known about the physiology underlying the benefits of osteopathic manipulative treatment (OMT). In vitro studies demonstrate a potential anti-inflammatory effect of OMT. PURPOSE: This research investigated the effects of OMT on inflammatory markers in rat skeletal muscle interstitial fluid, in vivo. METHODS: Inflammation was stimulated via bilateral, intra-articular injection of sodium iodoacetate into the knee joints of adult Sprague Dawley rats (n=8) to induce osteoarthritis. Animals were randomized to OMT or sham treatment four weeks post-injection. OMT included modified muscle energy treatments consisting of two techniques: 1) a practitioner restrained the rat's body and forelimbs. The rat extended its hindlimbs in an attempted escape maneuver, during which the hindlimb pushed against the practitioner's finger; and 2) the hindlimb was pulled into maximal extension. Light pressure applied to the foot evoked a reflexive flexion, against which the practitioner provided slight resistance. Passive myofascial stretching was conducted by applying light tensile force to the extended hindlimb. This force was held until a release was detected. Indirect techniques were held for 20 seconds, and direct techniques were repeated 3 times. Microdialysis probes were placed in the biceps femoris to collect cytokines from the muscular interstitium for 2 hours during each condition (pre-arthritis, post-arthritis, and post-OMT). Interstitial cytokine concentrations were determined using Luminex xMAP technology. RESULTS: Compared with baseline interstitial cytokine concentrations, IL-1 beta was significantly higher in the arthritis condition (p < 0.05). IL-6 and IL-13 tended to be higher in the arthritic condition, but did not reach statistical significance (IL-6, p=0.066, IL-13, p=0.08). However, in the subset of four animals that received OMT, IL-13 was significantly higher in both the arthritis conditions and post-OMT conditions, compared with baseline (p < 0.05). CONCLUSIONS: These preliminary findings suggest that certain cytokines measured in skeletal muscle interstitial fluid are elevated in response to induction of osteoarthritis, and that at least one cytokine, IL-13, continues to increase in response to OMT, suggesting a potential pathway by which OMT may elicit its purported effects.