Six miRNAs in Blood Show Potential as Biomarkers

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by Forest Ray PhD |

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Six microRNAs may serve as biomarkers of Parkinson’s disease progression and early diagnosis, a recent study suggests.

That study, “Several miRNAs derived from serum extracellular vesicles are potential biomarkers for early diagnosis and progression of Parkinson’s disease,” was published in the journal Translational Neurodegeneration.

MicroRNAs (miRNAs) are short RNA fragments that play a regulatory role in translating genetic information. Alongside this role, their relative stability and the availability of well-established methods to isolate and measure them has made them attractive diagnostic targets. They have emerged as potential biomarkers in numerous diseases, including Parkinson’s.

One drawback to using miRNA as a biomarker in Parkinson’s is that they are easily degraded by enzymes in the blood, making it difficult to measure them there. Small cell-like molecules called extracellular vesicles (EVs), however, bud off from cells and contain various components of the source cell, including miRNA. In contrast to naked miRNA, EVs are relatively stable in blood.

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Because EVs from the central nervous system — the brain and spinal cord, where Parkinson’s-related nerve damage occurs — can pass into the bloodstream, researchers from Tangdu Hospital, in Xi’an, China, asked whether these might contain miRNAs relevant to Parkinson’s.

A blood draw also would make for a less invasive diagnostic method than sampling the cerebral spinal fluid directly, which usually involves an injection into the spinal canal.

To this end, they screened 72 people at various stages of Parkinson’s for EV-derived miRNAs that associated both with Parkinson’s in general and with specific stages of the disorder. They compared their findings from this patient group to those of 31 healthy controls.

Once the investigators had isolated miRNA from EVs in the participants’ blood they used a statistical technique called weighted gene co-expression network analysis (WGCNA) to identify those miRNA that most associated with Parkinson’s and its stages.

From a total of 1,486 miRNA, the researchers identified 185 that appeared present at non-random levels. The team used WGCNA to infer which genes these miRNA most likely interacted with — essentially finding their place within networks of genes known to be active or not throughout Parkinson’s.

Because of the regulatory nature of miRNAs, the scientists then could deduce which miRNAs most likely played roles in the disorder.

This analysis revealed four miRNAs commonly associated with all stages of Parkinson’s and 13 that associated with specific stages.

To give them more confidence in their findings, the investigators analyzed these 17 miRNA using two more methods, one statistical and one biochemical.

Six miRNAs continued to correlate with Parkinson’s via both of these methods — two throughout all stages and four specific to different stages.

The researchers noted the results remain preliminary and must be validated in larger studies.

Nonetheless, they concluded their findings “lay foundation for clinical application of blood-based tests in PD diagnosis.”

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