Extracellular microRNAs have been identified in plasma, and our laboratory specifically studies extracellular microRNAs carried by lipoproteins including high-density lipoprotein (HDL). The goal of our laboratory is to characterize the role of these extracellular microRNAs, particularly to elucidate whether extracellular microRNAs may function as a novel cell-to-cell communication pathway. Within cells, microRNAs are small non-coding RNAs that post-transcriptionally regulate gene expression.