Study of serum exosome miRNA as a biomarker for early onset adult ouclar myastthenia gravis.

Background: By extracting and sequencing miRNAs from serum exosomes of patients with early-onset ocular myasthenia gravis (OMG), generalized myasthenia gravis (GMG) and healthy controls, we screened differentially expressed miRNAs and explored the possibility as potential biomarkers for early-onset OMG.

Methods: Peripheral blood samples were collected from patients with early-onset OMG, early-onset GMG, and age-matched healthy subjects, with 6 samples in each group. All these patients were diagnosed as MG for the first time and did not undergo any treatment. Exosomes miRNAs were extracted from the serum and performed deep sequencing; the differentially expressed miRNAs were compared and analyzed between OMG, GMG, and healthy control groups using edgeR. The differential expression standard was set to | log2FC |>1, p < 0.05. Target prediction of mRNAs were performed using miRTarBase, TargetScan, and miRDB databases, and a protein-protein interaction (PPI) network was constructed subsequently. The miRNAs with a significant difference were validated using RT-qPCR (10 early-onset OMG patients, 10 early-onset GMG patients and 10 age-sex-matched healthy subjects), and the value of the area under the ROC curve (AUC) was used to assess the diagnostic accuracy and evaluate clinical prognostic value.

Results: In total, one upregulated (miR-130a-3p) miRNA was obtained through the upregulated intersection between control vs OMG and OMG vs GMG; four downregulated (miR-4712-3p; miR-6752-5p; miR-320d; miR-3614-3p) miRNAs were obtained through the downregulated intersection between control vs OMG and OMG vs GMG. A total of 408 target genes were predicted for the five differentially expressed miRNAs. The mTOR signaling pathway and Rap1 signaling pathway were significantly enriched based on the enrichment results. RT-qPCR findings revealed that for the OMG, the expression of miR-320d, miR-4712-3p and miR-3614-3p was markedly up-/down-regulated as compared to GMG and healthy control group. The AUC for the three miRNAs between OMG and healthy control groups were 0.78, 0.79 and 0.79 respectively; the AUC between OMG and GMG was 0.84.

Conclusions: The present study identified three novel miRNAs as candidate biomarkers for early-onset OMG patients and it was expected to provide a possibility and a new orientation for serum exosomal miRNAs as OMG diagnostic biomarkers.