Formation of Composite Endothelial Cell-Mesenchymal Stem Cell-Islets; a novel approach to promote islet revascularization

Abstract

Objective: Mesenchymal stem cells (MSC) contribute to endothelial cell (EC) migration by producing proteases, thereby paving the way into the tissues for the EC. MSC were added to our previously described composite EC-islets as a potential mean to improve their capacity for islet angiogenesis.

Research Design and Methods: Human islets were coated with primary human bone marrow-derived MSC and dermal microvascular EC. The capacity of EC, with or without MSC, to adhere to and grow into human islets was analyzed. The survival and functionality of these composite islets were evaluated in a dynamic perfusion assay, and their capacity for angiogenesis in vitro was assessed in a three-dimensional fibrin gel assay.

Results: EC proliferated after culture in MSC-conditioned medium and MSC improved the EC coverage 3-fold when compared to EC-islets alone. Islet survival in vitro and the functionality of the composite islets after culture were equal to those of control islets. The EC-MSC-islets showed a 2-fold increase in total sprout formation when compared to EC-islets, and vascular sprouts emanating from the EC-MSC-islet surface showed migration of EC into the islets and also into the surrounding matrix, either alone or in concert with MSC.

Conclusions: EC proliferation, sprout formation, and in-growth of EC into the islets were enhanced by MSC. The use of composite EC-MSC-islets may have beneficial effects on revascularization and immune regulation. The technique presented allows for pre-treatment of donor islets with recipient-derived EC and MSC as a means of improving islet engraftment.