Characterization of the Effects of Mesenchymal Stromal Cells on Mouse and Human Islet Function

Abstract

Islet transplantation has the potential to cure type 1 diabetes, but current transplantation protocols are not optimal and there is extensive loss of islet β‐cell insulin secretory function during the immediate post‐transplantation period. Studies using experimental models of diabetes have shown that the coculture of islets with mesenchymal stromal cells (MSCs) prior to transplantation improves graft function, but several variables differed among research groups (e.g., type of MSCs used and the treatment conditions). We have therefore assessed the effects of MSCs on mouse and human islets by investigating the importance of tissue source for MSCs, the coculture protocol configuration and length, the effect of activated MSCs, and different β‐cell secretory stimuli. MSCs derived from adipose tissue (aMSCs) were the most effective at supporting β‐cell insulin secretion in both mouse and human islets, in a direct contact coculture configuration. Preculture with aMSCs enhanced both phases of glucose‐induced insulin secretion and further enhanced secretory responses to the non‐nutrients carbachol and arginine. These effects required a coculture period of 48–72 hours and were not dependent on activation of the MSCs. Thus, direct contact coculture with autologous, adipose‐derived MSCs for a minimum of 48 hours before implantation is likely to be an effective addition to human islet transplantation protocols. stem cells translational medicine 2019;8:935&944

Optimizing beta cell function through mesenchymal stromal cell-mediated mitochondria transfer

“…The concentrations of glucose used for basal and glucose‐stimulated OCR measurements mirror those used for our standard static islet insulin secretion assays (Figure C). As shown in Figure C, we consistently observe an MSC‐dependent potentiation of GSIS in both mouse and human islets, and using MSCs derived from multiple tissues including adipose, BM, and kidney . We now demonstrate that the MSC‐mediated improvements in islet insulin secretory function are associated with improved islet mitochondrial bioenergetics.…”

“…Thus, we demonstrated improved graft curative capacity in streptozotocin‐induced diabetic mice transplanted with islets cocultured with MSCs, whether grafted at the experimental renal subcapsular site or at the clinically preferred intraportal route . We, and others, have also demonstrated that these findings translate to clinically relevant human islets and human MSCs …”

“…We used a direct‐contact monolayer configuration to coculture islets with MSCs, as previously described . Briefly, 100 000 mouse MSCs (Cyagen strain C57BL/6 BM‐derived MSCs or Cyagen strain C57BL/6 Adipose‐derived MSCs; Generon, Slough, UK), or human adipose‐derived MSCs (Stempro Human Adipose‐derived stem cells; Life Technologies Ltd, Paisley, UK) were seeded into Nunclon 35 mm petri dishes, or 35 mm ibitreat ibidi μ‐Dish, high (Thistle Scientific Ltd, Glasgow, UK) for confocal imaging, forming a confluent monolayer of cells within 12 hours.…”

“…BacMam mitochondria‐GFP is targeted to the mitochondrial matrix pyruvate dehydrogenase enzyme complex, ensuring fluorescence labeling of MSC‐derived mitochondria. After 20 hours, the BacMam reagent was removed, MSCs washed three times in RPMI and expression of the GFP‐transgene confirmed by fluorescence microscopy, prior to setting up MSC‐islet cocultures, as described above …”

“…Mouse mesenchymal stromal cells (MSCs) derived from multiple tissue sources, including kidney, adipose, and bone marrow (BM), have direct effects on donor islet β‐cells to improve their survival and insulin secretory function during the in vitro culture period prior to transplantation . These in vitro findings correlate with persistent improvements in subsequent islet post‐transplantation function in vivo.…”