Archive | 2021
Autoantigen characterization in the lower esophageal sphincter muscle of patients with achalasia.
Abstract
OBJECTIVE: To characterize in sera anti-myenteric autoantibody profiles and in tissues MMP-9 proteoforms towards the identification of possible autoantigenic proteins in the muscle of the lower esophageal sphincter (LES) of achalasia patients. METHODS: Biopsies of the LES muscle from 36 achalasia patients, 6 esophagogastric junction outflow obstruction (EGJOO) patients, and 16 transplant donors (TD) were compared in a blind cross-sectional study. Histological characteristics such as inflammation, fibrosis, presence of ganglion cells, cells of Cajal, GAD65, PNMA2, S100, P substance, and MMP-9 proteforms in tissue were assessed by H&E and Picro-Sirius Red stainings, and immunohistochemistry analysis. Antineuronal antibodies (amphiphysin, CV2, and PNMA2 (Ma2/Ta)), onconeural antigens (Ri, Yo, and Hu), recoverin, SOX-1, titin, zic4, GAD65, and Tr (DNER) were evaluated by immunoblot/line assay. RESULTS: Tissue of achalasia patients had heterogeneous inflammatory infiltrates with fibrosis and contrasting higher levels of activated MMP-9 compared with EGJOO and TD. Moreover, lower ganglion cell percentages and cell of Cajal percentages were determined in esophageal tissues of achalasia patients vs. TD. In addition, tissue of achalasia patients had higher GAD65 and PNMA2 protein expression vs. EGJOO. Unexpectedly, these proteins were absent in TD tissue. S100 and P substance had similar expression levels in tissues of achalasia patients vs.TD and EGJOO. Most of the achalasia sera had anti-GAD65 (83%) and anti-PNMA2 (90%) autoantibodies vs. EGJOO (17% and 33%, respectively) and healthy volunteers (10% and 0%, respectively). CONCLUSION: Tissue-specific ectopic expression of GAD65 and PNMA/Ta2 and active MMP-9, associated with the presence of specific autoantibodies directed against these proteins, might participate in the pathophysiology of achalasia triggering and/or perpetuating autoimmune disease.