Stromal Cell Identity Influences the In Vivo Functionality of Engineered Capillary Networks Formed by Co-delivery of Endothelial Cells and Stromal Cells

Abstract

A major translational challenge in the fields of therapeutic angiogenesis and tissue engineering is the ability to form functional networks of blood vessels. Cell-based strategies to promote neovascularization have been widely explored, and have led to the consensus that co-delivery of endothelial cells (ECs) (or their progenitors) with some sort of a supporting stromal cell type is the most effective approach. However, the choice of stromal cells has varied widely across studies, and their impact on the functional qualities of the capillaries produced has not been examined. In this study, we injected human umbilical vein ECs alone or with normal human lung fibroblasts (NHLFs), human bone marrow-derived mesenchymal stem cells (BMSCs), or human adipose-derived stem cells (AdSCs) in a fibrin matrix into subcutaneous pockets in SCID mice. All conditions yielded new human-derived vessels that inosculated with mouse vasculature and perfused the implant, but there were significant functional differences in the capillary networks, depending heavily on the identity of the co-delivered stromal cells. EC-alone and EC-NHLF implants yielded immature capillary beds characterized by high levels of erythrocyte pooling in the surrounding matrix. EC-BMSC and EC-AdSC implants produced more mature capillaries characterized by less extravascular leakage and the expression of mature pericyte markers. Injection of a fluorescent tracer into the circulation also showed that EC-BMSC and EC-AdSC implants formed vasculature with more tightly regulated permeability. These results suggest that the identity of the stromal cells is key to controlling the functional properties of engineered capillary networks.

Stem Cells Derived from Tooth Periodontal Ligament Enhance Functional Angiogenesis by Endothelial Cells

“…In this model, we have previously demonstrated that MSC cotransplantation with ECs yields less permeable and more mature vessels than those formed from EC transplantation alone. 20,21 In the present study, fluorescent staining showed more dextran contained within the vessels where either MSCs or PDLSCs were cotransplanted, relative to the condition where only ECs were tranplanted (Fig. 5A).…”

“…19 Therefore, a 70-kDa Texas Red-conjugated dextran (k ex/em of 595/615 nm; Invitrogen) was chosen as a functionally defining tracer as described previously. 20,21 This dextran molecule contains free lysines, which are fixable in 4% paraformaldehyde (PFA). Before implant retrieval, mice were placed in a restraint device and 100 mL of a 5 mg/mL dextran solution in PBS was then injected through the tail vein.…”

Placental Mesenchymal Stromal Cells Derived from Blood Vessels or Avascular Tissues: What Is the Better Choice to Support Endothelial Cell Function?

“…In a subsequent in vivo study it is planned to compare both subsets of cells with respect to capillary formation and wound healing to support the hypothesis of this article. It has been shown that MSCs derived from different sources regulate angiogenesis via distinct mechanisms and that their identity also influences the functional properties of in vivo vessel implants [69,70]. In our study, we investigated MSCs isolated from a perivascular as well as an avascular niche, and could show that both have angiogenic properties.…”

Dual-Phase Osteogenic and Vasculogenic Engineered Tissue for Bone Formation

“…22 After sedation as previously described, mice were imaged in triplicate. A region of interest was drawn over the implant area and the mean perfusion through each implant was calculated.…”