In vitro co-culture models of peripheral blood derived cells and endothelial cells in angiogenesis

Abstract

Poor vascularization of tissue-engineered constructs is a common challenge in regenerative medicine and there is a need to find an optimal cell source that is proangiogenic and aids in the neovascularization process.

Endothelial progenitor cells (EPCs) are cells that participate in new blood vessel formation and regeneration of blood vessel endothelium in ischemic and hypoxic conditions. Two major types of EPCs are Myeloid Angiogenic Cells (MACs) and Endothelial Colony Forming Cells (ECFCs). MACs promote formation of new blood vessels via a paracrine mode of action.

Co-cultures of mesenchymal stem cells (MSCs) with peripheral blood derived mononuclear cells (MNCs) have been shown to possess angiogenic differentiation potential by inducing the differentiation of MACs.

This project aimed to test the functionality of MACs in a co-culture model with human umbilical vein endothelial cells (HUVECs). MACs with surface markers CD14 and CD31 were isolated from MSC-MNC co-cultures using magnetic-activated cell sorting and allowed to grow in a Transwell® setup with HUVECs. Optimisation of culture conditions with MSCs and HUVECs was also done to see if tube formation is affected by fibronectin coating and the type of culture media used.

Results show that co-cultures of MACs and HUVECs give rise to looping and branching tubular structures, such as those seen in de novo vascularization and that tube formation is favoured when cells were cultured in Endothelial Growth Media and on fibronectin coated surfaces.

These kind of in vitro assays will aid in assessing the proangiogenic capabilities of MACs. Further studies elucidating which paracrine vasoactive factors affect tube formation in angiogenesis will help in producing clinically applicable tissue-engineered constructs with better vascularization.