miRNAs in Blood Microvesicles Figure 4. Expression profile of common miRNAs. Heat-maps demonstrating the expression profile for microvesicles (A) and PBMC (B) were generated for miRNAs that were commonly expressed. (C) The number of shared and specific miRNAs for each sample group is shown. doi:10.1371/journal.pone.0003694.g004 these common predicted miRNA targets are amino acid and lipid metabolic pathways, among others (Table 2). We next examined miRNAs that were differentially expressed between plasma microvesicles and PBMC. We found 22 miRNAs had more than a two-fold increase in expression in the PBMC fraction compared to the plasma microvesicles samples, and among them, 15 miRNAs had more than 3-fold changes compared to PBMC (Table 3, Table S3). Interestingly, none of these differentially expressed miRNAs in plasma microvesicles were identified as tissue-specific miRNAs. As shown in Table 3, miR-486 is the highest differentially expressed miRNA in the plasma microvesicles compared to PBMC. The canonical pathways predicted to be regulated by miR-486 are phenylalanine and cyanoamino acid metabolism, insulin receptor signaling, antigen presentation, and pentose phosphate pathways. Comparison of miRNA expression in platelet and plasma microvesicles Since the majority of plasma microvesicles were platelet- derived, we also isolated platelets from several of the donors (n = 6) to profile miRNA expression. We found 52 co-expressed miRNAs in plasma microvesicles and platelets, while there were many more miRNAs unique to the plasma microvesicles compared to platelets (Figure 5). As shown in Table 4, there are many similarities between the platelets and the plasma microves- icles and PBMC. One striking observations is that miR-223 is also PLoS ONE | www.plosone.org 6 November 2008 | Volume 3 | Issue 11 | e3694