Neuronally enriched microvesicle RNAs are differentially expressed in the serums of Parkinson’s patients

Abstract

BackgroundCirculating small RNAs (smRNAs) originate from diverse tissues and organs. Previous studies investigating smRNAs as potential biomarkers for Parkinson’s disease (PD) have yielded inconsistent results. We investigated whether smRNA profiles from neuronally-enriched serum exosomes and microvesicles are altered in PD patients and discriminate PD subjects from controls.MethodsDemographic, clinical, and serum samples were obtained from 60 PD subjects and 40 age- and sex-matched controls. Exosomes and microvesicles were extracted and isolated using a validated neuronal membrane marker (CD171). Sequencing and bioinformatics analyses were used to identify differentially expressed smRNAs in PD and control samples. SmRNAs also were tested for association with clinical metrics. Logistic regression and random forest classification models evaluated the discriminative value of the smRNAs.ResultsIn serum CD171 enriched exosomes and microvesicles, a panel of 29 smRNAs was expressed differentially between PD and controls (false discovery rate (FDR) < 0.05). Among the smRNAs, 23 were upregulated and 6 were downregulated in PD patients. Pathway analysis revealed links to cellular proliferation regulation and signaling. Least absolute shrinkage and selection operator adjusted for the multicollinearity of these smRNAs and association tests to clinical parameters via linear regression did not yield significant results. Univariate logistic regression models showed that four smRNAs achieved an AUC ≥ 0.74 to discriminate PD subjects from controls. The random forest model had an AUC of 0.942 for the 29 smRNA panel.ConclusionCD171-enriched exosomes and microvesicles contain the differential expression of smRNAs between PD and controls. Future studies are warranted to follow up on the findings and understand the scientific and clinical relevance.

CNS cell-derived exosome signatures as blood-based biomarkers of neurodegenerative diseases

“…There has been debate concerning the presence of L1CAM on the surface of EVs, given multiple processed forms of the protein and recent evidence showing that L1CAM is not associated with EV fractions from plasma and CSF ( Norman et al, 2021 ). Other groups that attempted to isolate L1CAM-positive EVs from plasma demonstrated that EVs indeed expressed L1CAM ( Dutta et al, 2021 , 2023 ; Gomes and Witwer, 2022 ; Aguilar et al, 2023 ). Thus, there is conflicting evidence regarding the presence of L1CAM on EVs and whether or not it can reliably be used as a marker of neuron-derived EVs ( Gomes and Witwer, 2022 ).…”

“…The RNA content of neuron-derived EVs has also been under investigation. Of note, while there is a wealth of studies measuring RNA in total EVs from the blood of patients with neurodegenerative diseases, as discussed elsewhere ( Liu et al, 2019 , 2022 ; Sproviero et al, 2022 ; Bagyinszky et al, 2023 ; Dutta et al, 2023 ; Xu et al, 2024 ), there are fewer studies for neuronal and other CNS-derived EVs ( Cha et al, 2019 ; Banack et al, 2020 , 2022 ; Serpente et al, 2020 ; Zou et al, 2020 ; Durur et al, 2022 ; Li et al, 2022a , b ; Pounders et al, 2022 ; Aguilar et al, 2023 ; Dunlop et al, 2023 ). This likely reflects poor reproducibility of RNA findings from total plasma, serum and CSF EVs due to unstandardized EV isolation techniques, use of different downstream RNA measurement techniques and variations in the patient populations studied ( Liu et al, 2022 ; Dutta et al, 2023 ).…”

“… Zou et al (2020) demonstrated that Linc-POU3F3 was upregulated in L1CAM-positive plasma neuronal exosomes of PD patients compared to healthy controls, positively correlating with PD severity. Aguilar et al (2023) reported a panel of 29 differentially expressed small RNAs in PD compared to matched healthy controls, several of which have previously been implicated as circulating biomarkers of PD or detected in PD brain tissue. These studies used various methods for isolating neuron-derived EVs and quantifying their RNA content, with substantial variability in sample sizes and findings, necessitating validation with a standardized approach.…”