PECAM-1 expression by mesenchymal stromal cells is regulated by Notch signalling

• Main Author: Roberts, Samantha
• Published: University of Manchester 2014
• Subjects: 616.02
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.634864

Mesenchymal stromal cells (MSCs) reside within the perivascular niche and have been shown in vivo to facilitate vascular repair. Previous in vitro studies, have demonstrated the potential of MSCs to differentiate towards an endothelial lineage, when cultured at high cell density; but the characterisation of these cells and the mechanisms directing this important differentiation effect are ill-defined. To resemble a three-dimensional (3D) cellular environment, MSCs were cultured as spheroids and the endothelial characteristics of these cells determined. MSCs cultured as spheroids significantly increased their expression of the endothelial markers; PECAM-1, Tie2, VE-cadherin and vWF, when compared to MSCs cultured in close cell contact as a two-dimensional (2D) monolayer. In addition, MSCs cultured as 3D spheroids behaved as functional endothelial cells in vitro; including the ability to uptake low-density lipoproteins, secretion of nitric oxide and the ability to form network-like structures. MSC spheroids exhibited significantly increased levels of Notch signalling, compared to 2D MSCs in close cell contact, which caused a significant decrease in the endothelial characteristics when inhibited. Conversely, activation of Notch signalling caused a significant and specific increase in the expression of PECAM-1, which was regulated by the Notch ligands Jagged1 and DLL4. Thus, Notch signalling is a crucial pathway that controls PECAM-1 expression and regulates the angiogenic fate of MSCs within spheroids. This study has therefore identified an efficient culture model and key signalling mechanism which may be used to induce MSCs towards an angiogenic fate for vascular repair and regeneration therapies.