Study On Clinical Feature, Pathology And Proteomics Of Sporadic Inclusion Body Myositis

Objective:1. Explore chinical and pathologic features of sporadic inclusion body myositis;2. Study the pathogenesis of sporadic inclusion body myositis by identification of specific proteins of sIBM.Methods:1. Profile of 28 sIBM patients were analyzed by retrospective study.2. Investigate the pathological features of sIBM by using enzymohistochemistry method.3. By using two-dimensional gel electrophoresis and MALDI-TOF-MS, we identifed the proteins which were expressed differently within two groups. Online analysis of differently expressed proteins functions were proceeded with data analysis tools of DAVID database. Expression of above-mentioned proteins were assayed by Real-time fluorescent quantitative PCR and Western Blot.Results:1. Among 4099 suspected myopathy cases,28 cases in which 20 male patients and 8 female patients were diagnosed as sIBM. The incidence rate was 0.68%. The average onset age of sIBM was 51.39±7.83years old. Initial symptoms were majored in weakness of lower limb followed by four limbs, and then for the upper limb weakness. Clinical features were described as follow: weakness of both proximal lower limbs(100%), weakness of distal upper limbs (78.6%), neck weakness(32.1%), while only 5 for quadriceps atrophy(17.9%). Creatase were normal or mildly elevated. CK value of sIBM patients with below 5 years duration was significant higher than that of patients with longer duration(544.82±376.34 Vs.272.61±109.78)IU/L(t=0.04, P＜0.05). LDH value of neck involved patients was significantly higher than that of patients without neck involved (254.78±80.15 Vs.196.27±41.84)IU/L(t=2.363, P＜0.05).2. The pathological feature of sIBM were as below. Atrophic fibers appeared small angular or irregular shape (81.43%) and small round shape(17.86%); Rimmed vacuoles appeared crack shape (67.86%) or round (32.14%); Inclusion body shapes were sand-like particles (78.57%) and coarse particles(21.43%); 2 for non-necrotic muscle fibers infiltrated by mononuclear cell (7.14%), while 10 for necrotic muscle fibers infiltrated by mononuclear cell (35.71%); 15 for inflammatory cell infiltration (53.57%), while 13 for without inflammatory cell infiltration(46.43%); 9 for accumulation of inflammatory cells around blood vessels(32.14%), while 19 for without accumulation of inflammatory cells(67.86%); 3 for being seen RRF with GMT staining. (10.71%); ORO staining showed 3 cases were positive (10.71%); ATP staining showed 2 types of muscle fibers evenly distributed for 85.71%, while theⅠtype muscle fibers dominant only in 3 cases, accounting for 10.71% andⅡtype muscle fibers dominant only in one case, accounting for 3.57%.3.29 differently expressed protein spots were identified among which 16 up-regulated and 13 down-regulated. Their biological function were versatile, mostly focused on construction of cytoskeleton, muscle contraction, oxidative stress response, apoptosis regulation and local adhesion. The proteins participated 19 signal paths, which involved in tight junction pathway, muscle contraction pathway, etc. Cellular localization analysis:cytoplasm proteins(31.8%), cytoskeleton proteins(31.8%), neucleoproteins (13.6%) and intracellular organelle proteins(22.7%). Chromosome locations were most numerous in chromosome 1 and 11 for 5 genes each.4. Both mRNA and protein expression of aB-crystallin and APP in sIBM group were significantly higher than that of control group(P<0.05).Conclusions:1. The incidence rate of sIBM was 0.68% in China. Initial symptom of sIBM was mainly both lower limbs weakness. Clinical manifestation mostly showed up as proximal lower limbs and distal upper limbs weakness. However, only 17.9% cases for quardriceps atrophy. Creatase were normal or mildly elevated, most notable in early stage of disease and not significant in later stage.2. The pathological features of sIBM followed as below. The shape of atrophic mucle fiber were mostly appeared as small angle or irregular forms; The shape of rimmed vacuoles mainly were like crack and the inclusion grains were mainly small sand-like particles; There were few mononuclear infiltration of non-necrotic muscle fiber, while more for necrotic muscle fibers; Half cases showed inflammatory cell infiltration, and one third of the cases showed infiltration of inflammatory cells around small blood vessels.3.29 differently expressed proteins were identified in sIBM muscles. Among them, expression of APP and aB-crystallin were significantly increased both in gene and protein level, indicating their intimate correlation with pathogenesis of sIBM.