Density dependent differentiation of mesenchymal stem cells to endothelial cells

Abstract

Scientific abstract of thesis submitted by Jemima Lois Whyte for the degree of Doctor of Philosophy entitled 'Density dependent differentiation of mesenchymal stem cells to endothelial cells' September 2010.The differentiation of mesenchymal stem cells (MSCs) to endothelium is a critical but poorly understood feature of tissue vascularisation and considerable scepticism still remains surrounding this important differentiation event. Defining features of endothelial cells (ECs) are their ability to exist as contact-inhibited polarised monolayers that are stabilised by intercellular junctions, and the expression and activity of endothelial markers. During vasculogenesis, communication between MSCs and differentiated ECs or vascular smooth muscle cells, or between MSCs themselves is likely to influence MSC differentiation. In this study, the possibility that cell density can influence MSC differentiation along the EC lineage was examined. High density plating of human bone marrow-derived MSCs induced prominent endothelial characteristics including cobblestone-like morphology, enhanced endothelial networks, acetylated-low density lipoprotein uptake, vascular growth and stimulated expression of characteristic endothelial markers. Mechanistically, this density-dependent process has been defined. Cell-cell contact-induced Notch signalling was a key initiating step regulating commitment towards an EC lineage, whilst VEGF-A stimulation was required to consolidate the EC fate. Thus, this study not only provides evidence that MSC density is an essential microenvironmental factor stimulating the in vitro differentiation of MSCs to ECs but also demonstrates that MSCs can be differentiated to a functional EC. Taken together, defining how these crucial MSC differentiation events are regulated in vitro, provides an insight into how MSCs differentiate to ECs during postnatal neovascularisation and an opportunity for the therapeutic manipulation of MSCs in vivo, enabling targeted modulation of neovascularisation in ischaemia, wound healing and tumourigenesis.

Date of Award	1 Aug 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Catherine Kielty (Supervisor)