Special Pathologic Features of Adolescent Idiopathic Scoliosis: Could There be a New Type of Muscular Dystrophinopathy?

Abstract Background: Adolescent idiopathic scoliosis (AIS) is characterized by vertebral rotation and lateral curvature of the spine and affects 2-4% of the population throughout the world and the cause of the disease is still controversial. Recent researches suggest that there is an internal correlation between certain neuromuscular diseases and AIS. This study aims to characterize the paraspinal muscles of AIS patients, and to further explore the its etiology.Methods: Eighteen AIS patients treated with posterior scoliosis correction surgery were included and had biopsies taken from the paraspinal muscle at the apex vertebra region. Serial sections with conventional H&E staining and histochemical staining were obtained, and immunohistochemical examinations were employed to detect Dystrophin-1, -2, -3, Myosin, MHC-1, CD4, CD8, CD20, and CD68 or CD163 antibodies. Biopsy samples were grouped according to the subjects’ Cobb angle and Nash-Moe’s classification respectively, and the corresponding pathological changes were compared between groups. Results: The immunohistochemical staining results showed significant differences in the expression pattern of Dystrophin-2 (P=0.023) and Dystrophin-total (P=0.018) between the mild and severe scoliosis groups, with the expression of Dystrophin more abnormal or absent in the severe scoliosis group. There were also significant differences in the expression pattern of Dystrophin-2 (P=0.035) between the Nash-Moe classification subgroups. The expression of Dystrophin-3 was absent to various extent in all patients. Besides, we observed an infiltration of CD4+ and CD8+ cells in the paraspinal muscles and tendons. In all patients, the expression of MHC-1 on myolemma was present in some muscle fibers.Conclusions: The expression of dystrophin protein was significantly reduced and was correlated with the severity of scoliosis, suggesting that dystrophin protein dysfunctions contribute to the development of scoliosis. Meanwhile, the inflammatory changes of AIS mainly manifested in T cell activation and infiltration, and there seemed to be certain correlations between the expression of MHC-1 and the abnormal expression of dystrophin protein. Further studies along these results may open up new ideas for the diagnosis of scoliosis and the treatment for paraspinal myopathy.