Acetylcholine Receptor Subunit MRNA Expression In Patients With Myasthenia Gravis

Background&Objective: Myasthenia gravis (MG) is an autoimmune disease causedby the action of autoantibodies against the nicotinic acetylcholine receptor (AChR) at theneuromuscular junction. After years of a lot of study found that more than90%of patients inthe serum MG can detect acetylcholine receptors antibodies（AChR-Ab）. It has not yet beenelucidated that the pathogenesis of MG and the role of the thymus in MG pathogenesisit.Basically many early experiments on the genetic level to research the thymus and therelationship of MG are directed the expression of Arch subunits. But their results are notconclusive. We studied12MG thymomas and intercostal muscle to clarify which subunits ofthe AChR are expressed in the human thymoma.Methods: We obtained thymoma tissue and muscle tissue from12MG patients whenthe thymoma was removed as part of their therapeutic management; Normal thymus tissueand muscle tissue was from12subjects with normal immune function who underwentcardiac surgery and in whom access to the heart required removal of thymus tissue. ByRT-PCR method to detecteach m RNA of AChR subunits in thymic tissue and muscle tissue,after RT-PCR we measured gray value for PCR result. According to the pathological types ofthymoma and Osserman type, the tissues were divided into4groups. By comparing these4groups, we investigate the expression of AChR subunit.Results: We detect all the AChR subunits in thymoma and thymus, all the AChRthymus unit has no obvious difference of positive in thymoma and thymus (P>0.05); EveryAChR unit mRNA gray value/a-tublin mRNA gray value in thymoma were lower than thatof the muscle tissue (P <0.05); AChR-γ unit mRNA gray value/a-tublin mRNA gray valuebetween MG muscle and nomal muscle had no difference(P>0.05); Compare with nomalmuscle,other AChR subunits mRNA gray value/a-tublin mRNA gray value in MG musclewere significantly increased(P <0.05);We detect AChR-εmRNA only expression in A typeand AB type thymoma; Expression of each AChR subunit in different Osserman points ofMG with thymoma were no difference obvious (P>0.05).Conclusions: The thymus contains adult AChR-like protein and fetal AChR-likeprotein, antigenically abnormal AChRs in the thymus may play a role in the breakdown of tolerance and start the autoimmune response that causes MG.; the expression of adultAChR-like protein and fetal AChR-like protein in thymoma lower than normal intercostalmuscle and MG intercostal muscle; AChR-ε subunit may be specifically expressed in type Aand type AB thymoma;The relationship between AChR subunits in thymoma and diseaseseverity of MG remains controversial, need to increase the sample size line and further studyidentified.