Division of Diabetes and Nutritional Sciences
King's College London
Effects of activated mesenchymal stromal cells on islet secretory function and cellular overgrowth on microencapsulated islets
Ahmed Arzouni1, Andreia E Vargas1, Rahul Krishnan2, Jonathan RT Lakey3, Shanta Persaud1, Peter M Jones1, Aileen J King1.
1Division of Diabetes and Nutritional Sciences, King’s College London, London, United Kingdom; 2Department of Surgery, University of California, Irvine, Orange, CA, United States; 3Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, United States
Background: Mesenchymal stromal cells (MSCs) have been shown to be beneficial to islet transplantation outcome. However, previous studies have used quiescent MSCs. In an inflammatory environment MSCs become activated to show extensive immunomodulatory properties. This study aimed to determine whether activation of MSCs by exposure to pro-inflammatory cytokines affects their ability to influence islet function. In addition, we investigated whether co-transplantation of activated MSCs can reduce cellular overgrowth on microencapsulated islets.
Methods: Adipose-derived MSCs and mouse pancreatic islets were isolated from C57BL/6 and ICR mice. Islets isolated from juvenile pre-weaned Yorkshire pigs at the University of California Irvine were also used. Activation of MSCs was achieved by incubation (37 °C, 8 hrs) in the presence of the inflammatory cytokines TNF-α and IFN-γ (20ng/ml respectively), and confirmed by measuring the relative expression of mRNAs for nitric oxide synthase (NOS2) and chemokine C-X-C motif ligand 9 (CXCL9). Islets were cultured alone or in a direct-contact configuration with either quiescent or activated MSCs for 48 hrs before assessment of glucose-stimulated insulin secretion (GSIS). Piglet islets were microencapsulated in high G alginate microcapsules cross-linked with barium and calcium. They were transplanted intraperitoneally into normoglycaemic C57BL/6 mice either alone or together with free (non-encapsulated) activated MSCs. Microcapsules were recovered 5 days post-transplant and were subjectively scored for overgrowth in a blinded fashion. Scores 0 to 4 were used; 0 indicating no overgrowth and 4 indicating substantial overgrowth.
Results: Effect of activated MSCs on islet function: Culturing MSCs for 8 hrs in the presence of TNF-α and IFN-γ was sufficient to activate MSCs as assessed by increased mRNA expression levels of NOS2 (1x10-4 ;quiescent MSCs, 1x10-1 ;activated MSCs) and CXCL9 (3.4x ;quiescent MSCs, 6 x10-1 ;activated MSCs) relative to GAPDH expression. Islets cultured alone (IA) for 48 hours responded to a stimulatory concentration of glucose with increased insulin secretion (0.07 ± 0.05 ng/islet/h; 2mmol/L, 0.73±0.14 ng/islet/h; 20mmol/L). Glucose-induced insulin secretion was potentiated in islets that had been co-cultured with quiescent or activated MSCs compared to IA (20mmol/l 4.99± 1.1 ng/islet/h; quiescent-MSCs, 20mmol/l 3.50 ± 0.82 ng/islet/h; activated MSCs, p <0.05). However, activated MSCs did not further enhance insulin secretion above the level induced by co-culture of islets with quiescent MSCs. Effect of activated MSCs on inflammatory response to encapsulated pig islets: the inflammatory response to encapsulated pig islets was not reduced when activated MSCs were co-transplanted (average overgrowth score: control:1.52 ± 0.2 vs. activated MSCs: 1.25 ± 0.2, p=0.083)
Conclusion: Both quiescent and activated MSCs enhanced glucose-induced insulin secretion from islets when co-cultured in a direct co-culture configuration in vitro. MSC activation by cytokine treatment did not further enhance insulin secretion above the level induced by quiescent MSCs. Activated MSCs did not reduce inflammatory responses to encapsulated porcine islets.
15:30 - 16:30
|Zeroing in on the Perfect Encapsulation and Immunoisolation Device||Effects of activated mesenchymal stromal cells on islet secretory function and cellular overgrowth on microencapsulated islets||Room 110|