Chimeric Vessel Tissue Engineering Driven by Endothelialized Modules in Immunosuppressed Sprague-Dawley Rats

Abstract

Modular tissue engineering is a means of building functional, vascularized tissues using small (*1 mm long 0.5 mm diameter) components. While this approach is being explored for its utility in adipose and cardiac tissue engineering and in islet transplantation, the initial question in this study was to assess the fate of the endothelial cells (EC) after transplantation delivered on the surface of modules, without an embedded cell. Rat aortic ECcovered collagen gel modules were transplanted into the omental pouch of allogeneic (outbred) Sprague-Dawley rats with and without immunosuppressive drug treatment (atorvastatin and tacrolimus) for 3-60 days. There was a significant increase in vessel density at all time points in the drug treated rats as compared to untreated rats. Green fluorescent protein (GFP)-positive donor rat aortic EC migrated from the surface of the modules and formed primitive vessels by day 7. In the untreated rats, the GFP-positive cells were not seen after day 7. In drugtreated rats, GFP-positive vessels matured over time, accumulated erythrocytes, were supported by host smooth muscle cells, and formed chimeric vessels that survived until day 60. This resulted in the formation of a densely vascularized, perfusable network by day 60. To our knowledge, this is the first study that demonstrates that primary unmodified EC, without the addition of supporting cells, form a chimeric and stable vascular bed in allogeneic, although drug-treated, animals.

Cotransplantation of Adipose-Derived Mesenchymal Stromal Cells and Endothelial Cells in a Modular Construct Drives Vascularization in SCID/bg Mice

“…Hence, our interests in using modular tissue engineering with endothelial cell-coated collagen gel modules to effect vascularized implant sites. [1][2][3][4][5] Beyond nutrient supply, the endothelial cells also influence the fate of cotransplanted cells and the resulting tissue, here, for example, fat.…”

Toward anIn VitroVasculature: Differentiation of Mesenchymal Stromal Cells Within an Endothelial Cell-Seeded Modular Construct in a Microfluidic Flow Chamber

“…9,10 When implanted into rats treated with immunosuppressant drugs (atorvastatin and tacrolimus), donor EC migrated from the surface of modules without embedded cells and formed chimeric perfusable vessels containing host and donor cells that persisted for at least 60 days. 11 Embedding MSC within modules accelerated vessel formation and maturation in vivo, with the MSC appearing to differentiate into smooth muscle actin (SMA)-positive pericyte-like cells that integrated with the new vasculature. 12 The objectives of this article were to assess the remodeling of the MSC + EC modular constructs in vitro over 21 days subject to flow in a microfluidic chamber.…”

Application of an Endothelialized Modular Construct for Islet Transplantation in Syngeneic and Allogeneic Immunosuppressed Rat Models

“…This is consistent with our previous studies where complete vascularization took 2-3 weeks after transplantation of EC modules in allogeneic immune-suppressed recipients. 28 In that study, we showed that donor RAEC migrated from the surface of the modules to form primitive vessels within 1 week; however, donor vessel maturation (erythrocytes in lumen, supporting host smooth muscle cells, perfusable) and overall vessel density (both host and donor derived) peaked at 21 days. The immature vessels in the early transplant period likely did not support islets and presumably, the majority of transplanted islets were lost during this time.…”

“…27 Moreover, transplantation of rat aortic EC (RAEC) covered modules in the omental pouch resulted in the formation of a stable, perfusable vascular construct in immunosuppressed allogeneic recipients. 28 Here, we explored the use of these RAEC endothelialized modules for supporting transplanted islets in both immunosuppressed allogeneic and syngeneic diabetic recipients. In the allogeneic transplantation model, both donor and recipients were of an outbred rat strain (SpragueDawley) and thus received immunosuppression therapy, as before.…”