Identification Of Serum MiRNA Expression Profile Of Pakinson’s Disease

Background:Pakinson’s Disease, characterized by resting tremor, bradykinesia, cogwheel rigidity, and postural instability, is the second most common and age-related neurodegenerative disorder after Alzheimer’s disease. In industrialized countries, the prevalence of PD is estimated at 0.3% of the entire population and 1% of people over 60 years old. The incidence rates of PD are 8-18 per 100,000 per year. PD diagnosis depends on clinical manifestation using Unified Pakinson’s Disease Rating Scale and modified Hoehn-Yahr stage. PD clinical manifestation doesn’t appear until 50%-70% dopaminergic neurons lost, making patients miss early treatment. MicroRNA (miRNA), an abundant class of small non-coding RNA, mainly cause the degradation or translational supperession of target mRNA. It’s reported that cancer patients and healthy controls have significantly different tissue miRNA profiles and serum/plasma miRNA profiles, therefore these miRNAs are considered as novel cancer biomarkers and potential therapy targets. Unlike cancer tissues, brain tissues of neurodegenerative disorders are from autopsy, so we supposed there was a unique serum miRNA expression profile in PD patients can be a new indicator. The aim of this study was to investigate the profile of serum miRNAs to explore its clinical value as novel biomarkers for Pakinson’s Disease.Methods:We collected serum samples of 106 sporadic PD patients and 115 age/ gender-matched healthy controls. Serum miRNAs were analyzed by Solexa Sequencing followed by a qRT-PCR assay. The qRT-PCR assay, which was divided into two phases, was used to further confirm the expression of miRNAs screened by Solexa Sequencing. ROC curve analysis and clustering analysis were conducted to determine the diagnostic usefulness of 5 selected miRNAs for PD.Results:Solexa Sequencing showed 159 miRNAs and 138 miRNAs were detected in PD samples and control samples, respectively. We selected 15 miRNAs into further screening.qRT-PCR assay identified five serum miRNAs(miR-195,miR-185,miR-15b, miR-221,miR-181 a) that could distinguish 45 PD samples from 36 controls (p< 0.01).miR-195 was up-regulated and other four were down-regulated in the serum of PD patients. This result was further confirmed in another 69 PD samples and 79 controls (p<0.01). The area under the receiver operating characteristic(ROC) curve ranged from 0.65 to 0.83 for each selected miRNA:miR-195 (AUC=0.65, 95%CI=0.57-0.79), miR-185 (AUC=0.80,95%CI=0.74-0.86), miR-221(AUC=0.81, 95%CI=0.75-0.86), miR-15b (AUC=0.83,95%CI=0.77-0.89), miR-181a (AUC= 0.74, 95%CI=0.67-0.80). Using the optimal cut-off value, the sensitivity and specificity were 50% and 69% for miR-195,60% and 77% for miR-185,64% and 81% for miR-221,66% and 82% for miR-15b,50% and 77% for miR-181a, respectively. Furthermore, this panel of five miRNAs can clearly distinguish PD from controls by unsupervised clustering method. In the training set,91.1% of 45 PD samples and 88.9% of 36 controls were classfied correctly. The rates were 85.2% and 49.4% in validation set of 61 PD samples and 79 controls.Conclusions:The serum of PD patients has rich and stable miRNAs, and its miRNA profile is different from healthy controls; In this study, we identified a profile of 5 serum miRNAs, miR-195 was up-regulated while miR-185, miR-15b, miR-221, miR-181a were down-regulated. This five-miRNA group can be used as a potential serum-based biomarker for the disgnosis of PD.