Impact of Pancreatic Rat Islet Density on Cell Survival during Hypoxia

Abstract

In bioartificial pancreases (BP), the number of islets needed to restore normoglycaemia in the diabetic patient is critical. However, the confinement of a high quantity of islets in a limited space may impact islet survival, particularly in regard to the low oxygen partial pressure (PO2) in such environments. The aim of the present study was to evaluate the impact of islet number in a confined space under hypoxia on cell survival. Rat islets were seeded at three different concentrations (150, 300, and 600 Islet Equivalents (IEQ)/cm2) and cultured in normal atmospheric pressure (160 mmHg) as well as hypoxic conditions (15 mmHg) for 24 hours. Cell viability, function, hypoxia-induced changes in gene expression, and cytokine secretion were then assessed. Notably, hypoxia appeared to induce a decrease in viability and increasing islet density exacerbated the observed increase in cellular apoptosis as well as the loss of function. These changes were also associated with an increase in inflammatory gene transcription. Taken together, these data indicate that when a high number of islets are confined to a small space under hypoxia, cell viability and function are significantly impacted. Thus, in order to improve islet survival in this environment during transplantation, oxygenation is of critical importance.

Extracellular hemoglobin combined with an O2‐generating material overcomes O2 limitation in the bioartificial pancreas

“…Of potential interest, we described that hypoxia did not induce increased IL-6 and MCP1 proinflammatory factor release by NPIs, unlike previous studies using rat (de Groot et al, 2003;Rodriguez-Brotons et al, 2016a), adult pig (Goto et al, 2010) and human (Brandhorst et al, 2016;Hals, Rokstad, Strand, Oberholzer & Grill, 2013) pancreatic islets under hypoxia. This weak impact of hypoxia on IL-6 and MCP1 secretion by NPIs could be related to their immaturity and relative resistance to hypoxic damages (Emamaullee, 2006).…”

“…The effect of the proposed O 2 supply strategies was also assessed in normoxia on the islet oxidative stress response (HO‐1), metabolic shift from an aerobic mitochondrial pathway to an anaerobic fermentation (PDK1, Kim, Tchernyshyov, Semenza & Dang, ) and proinflammatory responses (PTGS2, Rodriguez‐Brotons et al, ; Vivot et al, ). HEMOXCell alone did not significantly modify HO‐1, PDK1 and PTGS2 mRNA expression in encapsulated NPIs compared to Ct‐N (Figures a,b) except a slight decrease in PTGS2 mRNA level on Day 5 ( p < 0.05, Figure c).…”

“…HEMOXCell hemoglobin (Hemarina, Morlaix, France) was mixed with the alginate before crosslinking into alginate macrobeads. In accordance with the literature (Rodriguez-Brotons et al, 2016a;Le Pape et al, 2017a, 2017b, we screened concentrations of 50, 125, and 250 µg/ml of HEMOXCell on their ability to increase O 2 diffusivity.…”

“…This lack of O 2 is critical during the period preceding the neovascularization around the capsules, which occurs approximately 1 to 2 weeks post‐transplantation (Jansson & Carlsson, ; Jones et al, ; Morini et al, ). Low O 2 tension has been shown to induce hypoxia‐related oxidative stress (Rodriguez‐Brotons et al, ) and metabolic changes (Sato et al, ; Sato, Inoue, Yoshizawa & Yamagata, ) in islets resulting in insulin secretion impairment (Dionne, Colton & Yarmush, ), proinflammatory factor secretion (Brandhorst, Brandhorst, Mullooly, Acreman & Johnson, ), and finally islet cell death (de Groot et al, ; Sato et al, ). In these conditions, designing a BAP without adequate O 2 supply is likely to lead to long‐term graft failure and therapeutic inefficiency.…”

A factorial design to identify process parameters affecting whole mechanically disrupted rat pancreata in a perfusion bioreactor

“…The effect of oxygen on islets has been investigated by multiple researchers. Globally, severe hypoxia, akin to the oxygen environment transplanted islets initially encounter, has been shown to negatively impact islet yield, viability, and functionality . However, moderate hypoxia may have a beneficial effect on islet function …”