Levels of Specific MicroRNA a Potential Biomarker for Myasthenia Gravis, Study Shows

Blood levels of a microRNA called miR-150-5p have been identified as a potential biomarker for AChR-positive myasthenia gravis, after surgical treatment was found to reduce its levels in a study.

The study, “Thymectomy lowers the myasthenia gravis biomarker miR-150-5p,” was published in the journal Neurology — Neuroimmunology Neuroinflammation.

The thymus, a gland that controls immune function, plays a fundamental role in the development of myasthenia gravis.

Because many myasthenia gravis patients who have autoantibodies against AChR (nicotinic acetylcholine receptor) also display abnormalities in this gland, surgical removal of the thymus, or thymectomy, is considered an option for these patients.

MicroRNAs (miRNAs) are small noncoding RNA molecules that act as powerful regulators of gene expression. These small molecules can be secreted from cells as extracellular circulating miRNAs, supporting their use as potential biomarkers for many diseases.

Previous studies showed the levels of two specific miRNAs  — called miR-150-5p and miR-21-5p — are increased in the blood of AChR-positive myasthenia gravis patients.

Researchers analyzed the effect of thymectomy on the presence and pattern of these two miRNAs, which are thought to be potential biomarkers for this disease.

They collected blood samples from 80 patients who were enrolled in the MGTX trial (NCT00294658), out of which 38 were randomized for a thymectomy plus treatment with Deltasone (prednisone), an immunosuppressant therapy, while 42 patients received only the prednisone.

They then assessed the levels of expression of miR-150-5p and miR-21-5p in each group with a technique called real-time polymerase chain reaction.

Researchers did this analysis at the starting point and at 12, 24 and 36 months after randomization.

Results showed that, at 24 months, patients who had a thymectomy had lower levels of miR-150-5p  compared with initial values and the prednisone group. In fact, they found no change in miRNA levels in the prednisone group.

The reduction in miR-150-5p levels followed clinical improvements after a thymectomy, further evidence of this miRNA’s potential as a biomarker for myasthenia gravis.

These results show that thymectomy decreases the levels of circulating miR-150-5p, regardless of clinical differences in the AChR-positive study group, supporting “its value as a disease biomarker but also is yet another piece of evidence supporting the clinical effect of thymectomy in patients with MG [myasthenia gravis],” according to the study.