Sry-type HMG box 18 contributes to the differentiation of bone marrow-derived mesenchymal stem cells to endothelial cells

• VEGF-165 stimulation of MSCs induced prolonged upregulation of Sox9 and Sox18 mRNA and protein levels.
• siRNA-mediated knockdown of Sox18, as opposed to Sox9, diminished VEGF-165-mediated induction of the EC markers vWF, PECAM-1, and VE cadherin.
• Exogenous expression of Sox18 in MSCs caused upregulation of VEGFR-2.
• Pharmacological inhibition of VEGFR-2 prevented VEGF-165-mediated induction of Sox18 and differentiation of MSCs into ECs.
• The VEGF-165—VEGFR-2—Sox18 axis plays a critical role in MSC to EC differentiation.

ObjectiveMesenchymal stem cells (MSC) have shown therapeutic potential to engraft and either differentiate into or support differentiation of vascular endothelial cells (EC), smooth muscle cells and cardiomyocytes in animal models of ischemic heart disease. Following intracoronary or transendocardial delivery of MSCs, however, only a small fraction of cells engraft and the majority of those persist as an immature cell phenotype. The goal of the current study was to decipher the molecular pathways and mechanisms that control MSC differentiation into ECs. Vascular endothelial growth factor (VEGF-165) treatment is known to enhance in vitro differentiation of MSCs into ECs. We tested the possible involvement of the Sry-type HMG box (Sox) family of transcription factors in this process.Method and ResultsMSCs were isolated from the bone marrow of Yucatan microswine and underwent a 10 day differentiation protocol. VEGF-165 (50 ng/ml) treatment of MSCs in vitro induced a significant increase in the protein expression of VEGFR-2, Sox9 and Sox18, in addition to the EC markers PECAM-1, VE-cadherin and vWF, as determined by Western blot or flow cytometry. siRNA-mediated knockdown of Sox18, as opposed to Sox9, in MSCs prevented VEGF-165-mediated induction of EC markers and capillary tube formation. Inhibition of VEGFR-2 signaling (SC-202850) reduced Sox18 and reduced VEGF-165-induced differentiation of MSCs to ECs.ConclusionHere we demonstrate that VEGF-165 mediates MSC differentiation into ECs via VEGFR-2-dependent induction of Sox18, which ultimately coordinates the transcriptional upregulation of specific markers of the EC phenotype.