An estimated prevalence of 1% of people above 60 years old suffer from Parkinson’s disease (PD). PD mainly involves a progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc), which resulting in the corresponding decrease in dopamine neurotransmitter signaling and manifest as motor dysfunctions and clinical symptoms such as resting tremor, bradykinesia, rigidity and postural instability. In addition, Lewy bodies which are enriched with the intracellular inclusion of α-synuclein protein (α-syn) in the neurons of PD patients, are suggested to impair pathways such as vesicle trafficking or activating neuroinflammation (Goh et al., 2019).
The diagnosis of PD is still based on the assessment of clinical criteria mentioned above, which leads to an insufficient diagnostic accuracy. No definitive biomarker so far is available allowing the prediction or diagnosis of the disease course or monitoring the response to therapeutic approaches. Over the past decade, with techniques such as RNA sequencing, microarray and microRNA qPCR profiling, screening studies have been conducted to report that miRNAs expression profile is altered not just in brain tissues, and also peripheral body fluid such as cerebral spinal fluid, blood, or even saliva and urine. miRNAs in periphery might be the promising diagnostic candidates for PD, as they are easily accessible by non- or minimally-invasive procedures and changes in their expression are associated with pathophysiological processes relevant for PD (Roser et al., 2019).

miRNA in blood
Blood and its derivatives are the most extensively studied source fluid. Analysis of miRNA levels in whole blood by PCR arrays revealed a set of differentially expressed miRNAs that permitted the discrimination of PD patients and controls (miR-1-3p, miR-22-5p, and miR-29a-3p), as well as differentiating between Levodopa/Carbidopa-treated and untreated PD groups (miR-16-2-3p, miR-26a-2-3p, and miR30a-5p) (Margis et al., 2011). miR-137-3p and miR-124-3p were found significantly regulated in the serum from PD patients (Li et al., 2017). Ravanidis et al. reported the miRNAs profiling in serum were different between idiopathic and genetic PD, but were very similar between the genetic forms of PD. miR-132-3p (P = 0.083) and hsa-miR-433-3p were significantly upregulated, whereas miR-128-3p (P = 0.01), miR-136-3p, miR-154-5p, miR-323a-3p, (P = 0.055), miR-382-5p, miR-409-3p, miR-410-3p, and miR-485-5p, were significantly downregulated in both the GBA and SNCA mutations PD patients. This suggested that both mutations converge on the same master miRNAs that drive the pathophysiological process in PD.

miRNA in peripheral blood mononuclear cell (PMBC)
Microarray analysis of 19 PD and 13 control cases identified 18 miRNAs altered in PD, including several of the regulated miRNAs found in serum/plasma, miR-335, miR-374a, miR-199a-3p, miR-199b-3p, miR-126, miR-151-3p, miR-151-5p, miR-29b, miR-147, miR-28-5p, miR-30b, miR-374b, miR-19b, miR-30c, miR-29c, miR-301a, miR-26 (Martins et al., 2011). Then, RT-qPCR analysis revealed increased expression of miR-103a-3p, miR-30b-5p, and miR-29a-3p in PBMCs of PD patients (Serafin et al., 2015)

miRNA in cerebrospinal fluid (CSF)
Burgos et al. reporting that the miRNA signature in CSF seems to be slightly more stable (Burgos et al., 2014). The level of miR-132-5p in CSF was observed decreased in PD (Gillardon et al., 2008). Quantitative RT-PCR analysis of 44 PD and 42 controls
identified miR-200a-3p, miR-542-3p, and miR-144-5p upregulated in CSF of PD patients. And these candidates showed a high correlation with disease stages (Mo et al., 2016). Exosome miRNAs isolated from CSF also show differential expression according to disease states. Studies investigating such type of sample revealed miR-1, miR-19b-3p decreased expression in PD, while miR-153, miR-409-3p, miR-10a-5p, and let-7g-3p were found upregulated.

miRNA in saliva
The finding of miRNA in saliva is followed on from the previous work studying the overexpression of haem oxygenase 1 (HO1) in PD. The team led by Hyman Schipper previously found significant elevation of HO1 protein in the saliva of patients with PD so then they further investigated the downstream miRNA of HO1 pathway. They collected saliva from 83 patients with PD and 77 controls with no neurological condition. The samples were analyzed with RT-qPCR to measure levels of miR-153 and miR-223. Salivary levels of both miRNAs were lower in patients with PD than in controls (Cressatti et al. 2019).
 
Already, numerous studies have revealed a number of miRNAs in periphery as potential biomarkers for PD and other Parkinsonian syndromes. However, the overlap among the candidates is low in different studies, and the changes of miRNA in stages of the pathological progression needs to gather more findings. Additionally, fast, reliable, easy-to-handle, and cost-efficient miRNA detection methods are needed to further develop miRNAs as diagnostic biomarker for clinical use.
TOOLS launched a comprehensive list of miRNA assays that covers miRNAs reported in PD studies. The TOOLS miRNA assay system consists of TOOLS miRNA RT Kit, TOOLS miRNA RT-qPCR primer/probe set, and TOOLS Easy 2X probe qPCR mix. All TOOLS miRNA RT-qPCR primer/probe set are pre-designed, well-validated and QC. Customized design and production of miRNA RT-qPCR primer/probe set is also available. TOOLS miRNA assay allows rapid, sensitive, and specific profiling the expression of microRNA (miRNA) within the simple 2-step RT-qPCR procedure. To see the full list of TOOLS miRNA assay and related products, please click TOOLS Life Science Reagents - tools-biotech.com‎.

TOOLS provides well-validated RT-qPCR assay set to PD associated miRNAs.

Product name	miRNA ACC	Product name	miRNA ACC	Product name	miRNA ACC	Product name	miRNA ACC
cel-miR-39-3p	MIMAT0000424	hsa-miR-133a-3p	MIMAT0000086	hsa-miR-193a-5p	MIMAT0000770	hsa-miR-34a-5p	MIMAT0000682
cel-miR-54-3p	MIMAT0000434	hsa-mir-133a-5p	MIMAT0000088	hsa-miR-193b-3p	MIMAT0000451	hsa-miR-3615	MIMAT0004694
hsa-let-7a-5p	MIMAT0000433	hsa-miR-133b	MIMAT0000692	hsa-miR-194-5p	MIMAT0000232	hsa-miR-365a-3p	MIMAT0004585
hsa-let-7b-5p	MIMAT0000435	hsa-miR-135a-5p	MIMAT0000763	hsa-miR-196a-5p	MIMAT0000510	hsa-miR-3688-3p	MIMAT0004762
hsa-let-7d-3p	MIMAT0000437	hsa-miR-135b-5p	MIMAT0000441	hsa-miR-197-3p	MIMAT0004748	hsa-miR-374b-5p	MIMAT0019856
hsa-let-7d-5p	MIMAT0000257	hsa-miR-139-3p	MIMAT0000092	hsa-miR-199a-3p	MIMAT0002816	hsa-miR-4488	MIMAT0031177
hsa-let-7g-5p	MIMAT0000440	hsa-miR-1-3p	MIMAT0000093	hsa-miR-19a-3p	MIMAT0000063	hsa-miR-450a-5p	MIMAT0000442
hsa-miR-100-5p	MIMAT0000461	hsa-miR-140-3p	MIMAT0004600	hsa-miR-200a-3p	MIMAT0003303	hsa-miR-4755-3p	MIMAT0003150
hsa-miR-101-3p	MIMAT0000271	hsa-miR-141-3p	MIMAT0000253	hsa-miR-200c-3p	MIMAT0005881	hsa-miR-4793-3p	MIMAT0000420
hsa-miR-101-5p	MIMAT0000280	hsa-miR-142-3p	MIMAT0000254	hsa-miR-203a-3p	MIMAT0000067	hsa-miR-486-3p	MIMAT0000454
hsa-miR-103a-3p	MIMAT0004570	hsa-miR-142-5p	MIMAT0000428	hsa-mir-204-3p	MIMAT0004597	hsa-miR-499a-5p	MIMAT0000083
hsa-miR-106a-5p	MIMAT0002820	hsa-miR-143-3p	MIMAT0000758	hsa-miR-204-5p	MIMAT0000265	hsa-miR-500a-3p	MIMAT0000269
hsa-miR-106b-3p	MIMAT0004916	hsa-miR-144-3p	MIMAT0000256	hsa-miR-20a-5p	MIMAT0002888	hsa-miR-501-3p	MIMAT0000444
hsa-miR-107	MIMAT0000098	hsa-miR-144-5p	MIMAT0000073	hsa-miR-211-5p	MIMAT0000446	hsa-miR-502-3p	MIMAT0000426
hsa-miR-10a-3p	MIMAT0000101	hsa-miR-145-5p	MIMAT0000074	hsa-miR-215-5p	MIMAT0000259	hsa-miR-506-3p	MIMAT0000693
hsa-miR-10b-3p	MIMAT0000680	hsa-miR-146a-5p	MIMAT0000243	hsa-miR-221-3p	MIMAT0000082	hsa-miR-509-5p	MIMAT0003880
hsa-miR-1180-3p	MIMAT0000443	hsa-miR-148a-3p	MIMAT0000759	hsa-miR-223-3p	MIMAT0004515	hsa-miR-548f-5p	MIMAT0001340
hsa-miR-1229-3p	MIMAT0000068	hsa-miR-148a-5p	MIMAT0005898	hsa-miR-223-5p	MIMAT0000087	hsa-miR-550a-5p	MIMAT0003283
hsa-miR-1238-3p	MIMAT0000417	hsa-miR-151a-3p	MIMAT0000423	hsa-miR-224-5p	MIMAT0006764	hsa-miR-576-5p	MIMAT0000065
hsa-miR-1246	MIMAT0000069	hsa-miR-15a-5p	MIMAT0000449	hsa-miR-22-5p	MIMAT0000753	hsa-miR-615-3p	MIMAT0004703
hsa-miR-1247-5p	MIMAT0000070	hsa-miR-15b-5p	MIMAT0002819	hsa-miR-26a-1-3p	MIMAT0002880	hsa-miR-624-3p	MIMAT0004955
hsa-miR-125a-5p	MIMAT0000261	hsa-miR-16-5p	MIMAT0004767	hsa-miR-27b-3p	MIMAT0003218	hsa-miR-625-3p	MIMAT0004784
hsa-miR-126-3p	MIMAT0000072	hsa-miR-17-5p	MIMAT0000077	hsa-miR-29a-3p	MIMAT0000226	hsa-miR-629-5p	MIMAT0015083
hsa-miR-126-5p	MIMAT0001080	hsa-miR-181a-3p	MIMAT0000078	hsa-miR-29a-5p	MIMAT0000455	hsa-miR-633	MIMAT0001536
hsa-miR-127-3p	MIMAT0000617	hsa-miR-181a-5p	MIMAT0000255	hsa-miR-30a-3p	MIMAT0003393	hsa-miR-664a-3p	MIMAT0000757
hsa-miR-1276	MIMAT0000264	hsa-miR-181b-5p	MIMAT0003339	hsa-miR-30a-5p	MIMAT0004807	hsa-miR-671-5p	MIMAT0019206
hsa-miR-128-3p	MIMAT0000266	hsa-miR-183-5p	MIMAT0000414	hsa-miR-30b-5p	MIMAT0005577	hsa-miR-744-5p	MIMAT0000686
hsa-miR-1291	MIMAT0000076	hsa-miR-184	MIMAT0000275	hsa-miR-3158-3p	MIMAT0004949	hsa-miR-7706	MIMAT0000710
hsa-miR-1307-5p	MIMAT0000278	hsa-miR-185-5p	MIMAT0000416	hsa-miR-324-3p	MIMAT0005953	hsa-miR-92a-3p	MIMAT0001412
hsa-miR-130b-3p	MIMAT0000279	hsa-miR-187-3p	MIMAT0000084	hsa-miR-330-3p	MIMAT0003945	hsa-miR-92b-3p	MIMAT0000762
hsa-miR-130b-5p	MIMAT0000080	hsa-miR-18a-5p	MIMAT0000419	hsa-miR-339-3p	MIMAT0022693	hsa-miR-937-3p	MIMAT0004495
hsa-miR-1322	MIMAT0000081	hsa-miR-18b-5p	MIMAT0000100	hsa-miR-340-5p	MIMAT0001639	hsa-miR-9-3p	MIMAT0000765
hsa-miR-132-3p	MIMAT0004498	hsa-miR-1909-3p	MIMAT0000244	hsa-miR-342-5p	MIMAT0004681	SNORD48	MIMAT0004503

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References

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