307.7: 3D Bioprinting of Functional Islets With Adipose-derived Stromal Cells in an Alginate/Nanocellulose Scaffold

Abstract

Islet isolation procedure destroys islet vasculature and extra cellular matrix molecules, which can negatively affect islet function post transplantation. Developing scaffold that favors islet micro-environment is one solution to preserve islet function post isolation. 3D bioprinting of islets using hydrogel-based bioinks has been reported previously. However, modifying bioinks and presence of supporting cells such as adipose-derived stromal cells (ASCs) can improve survival and reduce cellular stress in islet scaffolds. We designed an implantable multi-layered 3D bioprinted scaffold for human or mouse islets -/+ human ASCs (1.2 ×106 ASCs/scaffold). Cells were embedded in alginate/nanocellulose bioink and printed with INKREDIBLE 3D Bioprinter from CELLINK AB. Micro-CT was used to study the distribution of islets inside scaffolds. In vitro cell viability and function were assessed using FDA/PI staining and glucose stimulated insulin secretion on day 1, 8 and 14 post print. The level of secreted human- and mouse-specific cytokines, IP-10, MCP-1 and GRO-α were measured on day 1, 8 and 14 post print. Islet scaffolds -/+ ASCs were transplanted intraperitoneal (IP) in diabetic immune-compromised mouse model and followed for 60 days post transplantation. We printed 100 islets/scaffold for in vitro and 400 islets/scaffold for in vivo studies. In vitro viability analysis revealed viable islets and ASCs throughout the studies. However, scaffolds with human and mouse islets + ASCs showed improved insulin secretion in response to glucose compared to the islet alone group on day 1, 8 and 14 post print (selected data points for human islets-day 8: islet+ASC, basal insulin 2387 ± 1262, stimulated insulin 4312 ± 606.8, recovery insulin post stimulation 1637 ± 100.1 pmol/L, * p< 0.05 vs stimulated insulin. Islet alone, basal insulin 2358 ± 887.9, stimulated insulin 1149 ± 352.6, recovery insulin post stimulation 999.0 ± 267.7 pmol/L, n=4). This is followed by significant reduction in the level of both human and mouse IP-10, MCP-1 and GRO-α in islet+ASC group compared to the islet alone group on day 1, 8 and 14 post print. IP transplantation of mouse islets -/+ ASCs to diabetic mice normalizes random blood glucose in both groups starting from day 6 post transplantation for islet+ASC group and day 40 for islet alone group. We detected c-peptide in both groups on day 3 and 13 post transplantation. However, at termination of the studies, the level of c-peptide was significantly higher in islet+ASC compared to the islet alone group (islet+ASC 94.01 ± 14.47 vs. islet alone 27.08 ± 18.93, p<0.05). This study presents a successful multi-layered scaffold design for islets and ASCs. Presence of ASCs in the scaffold can create a favorable micro-environment for the islets, resulting in reduced islet loss and improved islet function.