MicroRNAs (miRNAs) are short non-coding RNAs, which post-transcriptionally regulate gene expression. miRNAs are important in governing cell differentiation, development and disease. Our work spans the role of miRNA in the development of vascular pathologies associated with remodeling and with the vascular regenerative strategies in ischaemic conditions. We have focused on miRNA in the development of pulmonary arterial hypertension. In consideration of the role played by miRNAs in cell proliferation and vascular remodeling, we evaluated the involvement of the smooth muscle cell-associated miRNAs miR-143 and miR-145 in the development of PAH. Significant dysregulation of these miRNAs in PAH has been observed in animal models and in pathological samples. Manipulation of miR-145 may therefore represent a novel strategy to prevent the development of PAH. Further, miR-21 shows elevation in models of PAH and genetic ablation is detrimental to the development of the pathology. In the setting of vascular regeneration, we have profiled the expression of miRNA during the differentiation of human ES cells to vascular endothelial cells. We have identified a number of miRNA, including miR-181a, miR-181b and miR-99a that are rapidly induced during differentiation. We are implementing intervention strategies to manipulate these miRNA, as well as others, to ascertain their role in vascular differentiation in vitro and the effects on vascular regeneration in vivo.