Messenger RNA profiling of human platelets by microarray hybridization

Platelets are generally believed to be inactive in terms of de novo protein synthesis. On the other hand, the presence of ribo-somes and mRNA molecules is well established. Many studies have used reverse transcriptase (RT) -PCR for detection of gene transcripts in platelets. As RT-PCR is a very sensitive meth-od, any leukocyte contamination of platelet preparations can lead to false results. We performed three filtration procedures to minimize leukocyte contamination of pooled buffy-coat platelet concentrates prior to RNA isolation. Furthermore, by applying a genomic PCR approach with 50 amplification cycles we demonstrated that nucleated cells were not detectable. Microarray hybridization was used to analyze 9,850 individual human genes in RNA from purified platelets. In total we iden-tified 1,526 (15.5%) positive genes.The data were confirmed in six individual experiments each performed on a PC pooled from four individual blood donations. Genes specific for nucle-ated blood cells such as CD4, CD83 and others were negative and verified the purity of PC. Overrepresentation of positive genes was found in the functional categories of glycopro-teins/ integrins (22.6% vs. 15.5%, p=0.029) and receptors (20.7% vs. 15.5%, p