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

Abstract

The bioartificial pancreas encapsulating pancreatic islets in immunoprotective hydrogel is a promising therapy for Type 1 diabetes. As pancreatic islets are highly metabolically active and exquisitely sensitive to hypoxia, maintaining O2 supply after transplantation remains a major challenge. In this study, we address the O2 limitation by combining silicone‐encapsulated CaO2 (silicone‐CaO2) to generate O2 with an extracellular hemoglobin O2‐carrier coencapsulated with islets. We showed that the hemoglobin improved by 37% the O2‐diffusivity through an alginate hydrogel and displayed antioxidant properties neutralizing deleterious reactive O2 species produced by silicone‐CaO2. While the hemoglobin alone failed to maintain alginate macroencapsulated neonate pig islets under hypoxia, silicone‐CaO2 alone or combined to the hemoglobin restored islet viability and insulin secretion and prevented proinflammatory metabolism (PTGS2 expression). Interestingly, the combination took the advantages of the two individual strategies, improved neonate pig islet viability and insulin secretion in normoxia, and VEGF secretion and PDK1 normalization in hypoxia. Moreover, we confirmed the specific benefits of the combination compared to silicone‐CaO2 alone on murine pseudo‐islet viability in normoxia and hypoxia. For the first time, our results show the interest of combining an O2 provider with hemoglobin as an effective strategy to overcome O2 limitations in tissue engineering.

Collagen and Endothelial Cell Coculture Improves β-Cell Functionality and Rescues Pancreatic Extracellular Matrix

“…Hypoxia experiments were performed under the following conditions: 37°C, 5% CO 2 and 1% O 2 , which were chosen according to literature. [14][15][16] In detail, pseudoislets were seeded in overnight preincubated hypoxia medium. Media was changed every other day.…”

Optimization of An O2-Balanced Bioartificial Pancreas for Type 1 Diabetes Using Statistical Design of Experiment.

“…Of particular interest, the interaction between HEMOXCell and silicone-CaO 2 showed a positive synergistic effect on the viability of MPI in the BAP. This could be explained by the anti-oxidant properties of the hemoglobin neutralizing the ROS produced by the silicone-CaO 2 disk and by its capacity to increase the O 2 diffusivity in the alginate hydrogel, thereby preventing hyperoxia 24 was only 375 IEQ/cm 2 . Although the presence of HEMOXCell increased the viability of MPIs in the device, the tested concentrations of hemoglobin did not signi cantly affect the percentage of viable islets in the BAP.…”

“…Many strategies have been developed to address O 2 limitations in the BAP. They include use of hypoxiaresistant cells 20 , increased vascularization induction around the device 11,21,22 , increased O 2 diffusivity through the encapsulating biomaterial 23,24 , and an exogenous O 2 source [24][25][26][27] . One of the most promising strategies uses a gas delivery system developed by Beta O 2 Technologies (Rosh-Haayin, Israel).…”

Our Steps toward Subcutaneous Transplantation of Macro-Encapsulated Islets

“…In order to improve its histocompatibility or control pore size, surface modification with the polylysine-polyethyleneimine [6], lysine/alginate [7], poly-L-ornithine-alginate [8], carboxy methylcellulose, and others [9] were used. Regarding the concern of hypoxia, hemoglobin cross-linking [10], coencapsulation of photosynthetic oxygen generators [11], and use of CaO 2 and hemoglobin [12] were reported. In addition to alginate-based micro-encapsulation, agarose-based hydrogel was also reported [13].…”