Collagen modules for in situ delivery of mesenchymal stromal cell-derived endothelial cells for improved angiogenesis.

Modular tissue engineering is a strategy to create scalable, self-assembling, three-dimensional (3D) tissue constructs. This strategy was used to deliver endothelial-like cells derived from bone marrow mesenchymal stromal cells (EL-MSCs) to locally induce vascularization. First, tissue engineered modules were formed, comprising EL-MSCs and collagen-based cylinders. Seven days of module culture in a microfluidic chamber under continuous flow resulted in the formation of interstices, formed by random packing of the modules, which served as channels and were lined by the EL-MSCs. We observed maintenance of the endothelial phenotype of the EL-MSCs, as demonstrated by CD31 staining, and the cells proliferated well. Next, collagen modules covered with EL-MSCs, with or without embedded MSCs, were implanted subcutaneously in immune-compromised SCID/Bg mice. After 7 days, CD31-positive vessels were observed in the samples. These data demonstrate the feasibility of EL-MSCs coated collagen module as a strategy to locally stimulate angiogenesis and vasculogenesis. Copyright © 2013 John Wiley & Sons, Ltd.

Boosting angiogenesis and functional vascularization in injectable dextran-hyaluronic acid hydrogels by endothelial-like mesenchymal stromal cells.

Angiogenesis and neovascularization are fundamental for the success of clinically relevant-sized tissue-engineered (TE) constructs. The next generation of TE constructs relies on providing instructive materials combined with the delivery of angiogenic growth factors and cells to avoid tissue ischemia. However, the majority of materials and cell types screened so far show limited clinical relevance, either due to insufficient number of cells or due to the use of animal-derived matrixes. Here, we investigated whether endothelial-like cells derived from mesenchymal stromal cells (EL-MSCs) can be used for vascular TE in combination with injectable dextran-hyaluronic acid (Dex-g-HA) hydrogels. These hydrogels can be easily modified, as demonstrated by the incorporation of vascular endothelial growth factor (VEGF). We examined in vitro the reciprocal influences between cells and matrix. Dex-g-HA enabled higher EL-MSC metabolic rates associated with optimal cell sprouting in vitro compared to human umbilical vein endothelial cells. In vivo evaluation demonstrated the absence of an acute inflammatory response, and EL-MSCs incorporated within Dex-g-HA formed a functional vascular network integrated with the host vascular system. This work demonstrates that Dex-g-HA is an efficient delivery method of VEGF to induce angiogenesis. Additionally, functional neovascularization can be achieved in vitro and in vivo by the combination of Dex-g-HA with EL-MSC.

The effect of donor variation and senescence on endothelial differentiation of human mesenchymal stromal cells.

Application of autologous cells is considered for a broad range of regenerative therapies because it is not surrounded by the immunological and ethical issues of allo- or xenogenic cells. However, isolation, expansion, and application of autologous cells do suffer from variability in therapeutic efficacy due to donor to donor differences and due to prolonged culture. One important source of autologous cells is mesenchymal stromal cells (MSCs), which can differentiate toward endothelial-like cells, thus making them an ideal candidate as cell source for tissue vascularization. Here we screened MSCs from 20 donors for their endothelial differentiation capacity and correlated it with the gene expression profile of the whole genome in the undifferentiated state. Cells of all donors were able to form tubes on Matrigel and induced the expression of endothelial genes, although with quantitative differences. In addition, we analyzed the effect of prolonged in vitro expansion on the multipotency of human MSCs and found that endothelial differentiation is only mildly sensitive to expansion-induced loss of differentiation as compared to osteogenic and adipogenic differentiation. Our results show the robustness of the endothelial differentiation protocol and the gene expression data give insight in the differences in endothelial differentiation between donors.