Coculturing Human Islets with Proangiogenic Support Cells to Improve Islet Revascularization at the Subcutaneous Transplantation Site

Abstract

While subcutaneous tissue has been proposed as a clinically relevant site for pancreatic islet transplantation, a major issue of concern remains, which is its poor vascular state. In an effort to overcome this limitation, we present an efficient and reproducible method to form human composite islets (CIs) with proangiogenic cell types in a controlled manner using nonadherent agarose microwell templates. In this study, we assessed the three-dimensional structure, function, and angiogenic potential of human CIs with human mesenchymal stromal cells (hMSCs), with or without human umbilical vein endothelial cells (HUVECs), and preconditioned hMSCs (PC-hMSCs) in EGM-2 under shear stress. Distinct cellular rearrangements could be observed in CIs, but islet functionality was maintained. In vitro angiogenesis assays found significantly enhanced sprout formation in case of CIs. In particular, the number of sprouts emanating from CIs with PC-hMSCs was significantly increased compared to other conditions. Subsequent in vivo assessment confirmed the proangiogenic potential of CIs. However, in contrast to our in vitro angiogenesis assays, CIs with hMSCs and HUVECs exhibited a higher in vivo angiogenic potential compared to control islets or islets combined with hMSCs or PC-hMSCs. These findings highlight the importance and necessity of verifying in vitro studies with in vivo models to reliably predict, in this case, revascularization outcomes. Regardless, we demonstrate here the therapeutic potential of CIs with proangiogenic support cells to enhance islet revascularization at a clinically relevant, although poorly vascularized, transplantation site.

Modular tissue engineering for the vascularization of subcutaneously transplanted pancreatic islets

“…The primary challenge of the s.c. site for the transplantation of pancreatic islets is ensuring proper vascularization. Other groups have attempted to use the s.c. site with different systems, but these typically need excess islets to achieve glycemic control due to poor vascularization and a corresponding lack of direct integration with the host (28,30,31). For example, Hirabaru et al (30) used an MSC sheet to s.c. transplant 2,000 rat islets to rectify diabetes in SCID/bg mice for 28 d, but they were unable to achieve a therapeutic effect with a lower dosage of islets.…”

Stimulation of vascularization of a subcutaneous scaffold applicable for pancreatic islet‐transplantation enhances immediate post‐transplant islet graft function but not long‐term normoglycemia

“…Several strategies have been proposed to enhance vascularization. This includes cotransplantation of vascular-inductive cell types, 15,16 delivery of angiogenic genes, 17,18 or growth factor injections. 19,20 Some of these proposed systems are not applicable for islets.…”

Tissue‐engineering approaches in pancreatic islet transplantation

“…Agarose is another polysaccharide polymer extracted from seaweed that has been used in islet transplantation for 3 decades (Iwata et al, ). This biomaterial has been tested alone (Gazda et al, ; Kobayashi et al, ; Kobayashi et al, ; Magariños et al, ; Sato et al, ) or in combination with other synthetic and natural materials such as polystyrene sufonic acid (Kin et al, ; Tashiro et al, ; W. Wang et al, ) or chitosan (H. K. Yang et al, ), as well as with human complement receptor 1 (sCR1; Luan, Teramura, & Iwata, ), or even with supporting cells such as Treg cells (Takemoto, Konagaya, Kuwabara, & Iwata, ) or MSCs (Buitinga et al, ) both in vitro and in vivo. In most of the in vivo studies, agarose encapsulation protected islet grafts from the host immune response and improved engraftment.…”

“…Moreover, these cells have been shown to increase graft revascularization and thus islet survival and glycemic control when simply cotransplanted with islets (Kang et al, ; Oh et al, ; Pan et al, ; Penko et al, ; Quaranta et al, ; H. J. Song et al, ) in micro‐ (Buitinga et al, ) and macro‐encapsulation approaches (Gupta & Sefton, ; Y. Li et al, ) or even when using EPCs as a cell sheet (Barba‐Gutierrez et al, ). Similar metabolic results were obtained when human blood outgrowth endothelial cells ( BOECs ) derived from the in vitro expansion of peripheral blood mononuclear cells were combined with islets (Coppens et al, ; Coppens et al, ).…”

“…During the last few years, MSCs have been the cell type most frequently used in islet transplantation approaches, due to their proangiogenic and immunomodulatory paracrine effects (Hematti, Kim, Stein, & Kaufman, ; Sakata, Goto, Yoshimatsu, Egawa, & Unno, ; T. Wu, Liu, Wang, & Li, ). MSCs, which are obtained from different tissues, such as bone marrow, adipose tissue, or Wharton’s Jelly, have been shown to enhance graft immune tolerance (reducing or even avoiding the use of immunosuppressive drugs), while increasing the vascular density and reducing islet cell apoptosis when simply cotransplanted with islets (Ben Nasr et al, ; Berman et al, ; Borg et al, ; Cao, Li, Sun, Ge, & Liu, ; Cavallari et al, ; Ding et al, ; Figliuzzi et al, ; Ito et al, ; Jacobson, Kumagai‐Braesch, Tibell, Svensson, & Flodström‐Tullberg, ; Ohmura et al, ; Unsal et al, ; H. Wu, Wen, & Mahato, ; Xu et al, ; Yoshimatsu et al, ) in several tissue‐engineering approaches using micro‐ (Buitinga et al, ; Kerby, Jones, Jones, & King, ; Vériter et al, ) and macro‐encapsulation (Borg et al, ; Davis et al, ; Hamilton et al, ; Pérez‐Basterrechea et al, ; Vériter et al, ) or even when using MSCs as a cell sheet (Hirabaru et al, ), mainly at extrahepatic sites.…”