Matrix Metalloproteinases in Myasthenia Gravis

Abstract

Introduction: Myasthenia gravis (MG) is an autoimmune disease with weakness in striated musculature due to anti-acetylcholine receptor (AChR) antibodies or muscle specific kinase at the neuromuscular junction. A subgroup of patients has periocular symptoms only; ocular MG (OMG). Matrix metalloproteinases (MMP) are increased in several autoimmune diseases, including generalized MG (GMG), and have been suggested to play a role in immune cell infiltration, basement membrane breakdown and autoimmune pathogenesis. Methods: Total levels of MMP2, MMP3 and MMP9 were measured in serum by ELISA. Results: The MG patients had increased serum levels of MMP2 (median values 200.7 vs. 159.7 ng/ml, p < 0.001) and MMP9 (median values 629.6 vs. 386.4 ng/ml, p < 0.001) compared to controls. A subgroup of patients had increased MMP3 concentration (p = 0.001). The differences were not dependent on presence of AChR antibodies. No difference was observed between GMG and OMG patients with regard to MMP2 (p = 0.598), MMP3 (p = 0.450) and MMP9 (p = 0.271). Discussion: The increased MMP levels in our MG patients group and the lack of dependence on anti-AChR antibodies suggest that MMP2, MMP3 and MMP9 play a role in the development of MG. The similarities between GMG and OMG support OMG as a systemic disease.