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Updated: Jun 21, 2025
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Quantitative and Temporal Control of Oxygen Microenvironment at the Single Islet Level
Published on: November 17, 2013
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Hypoxia within subcutaneously implanted macroencapsulation devices limits the viability and functionality of densely
Samuel A Einstein1,2, Leah V Steyn3, Bradley P Weegman1,4
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States.
Frontiers in Transplantation
|July 12, 2024
Summary
Subcutaneous islet macroencapsulation shows low oxygen levels (PO2) within devices, impacting islet viability. Higher islet density leads to lower viability, suggesting apoptosis is a key factor in cell loss.
Area of Science:
- Biomedical Engineering
- Islet Transplantation
- Biomaterials
Background:
- Subcutaneous macroencapsulation offers an alternative to intraportal islet therapy.
- Achieving a curative dose necessitates dense islet packing within devices.
- Oxygen availability is critical for densely packed islet survival.
Purpose of the Study:
- To measure internal oxygen levels in subcutaneous macroencapsulation devices.
- To model oxygen availability and islet viability within these devices.
- To assess the impact of islet density on viability in implanted devices.
Main Methods:
- Noninvasive 19F-MRS was used to measure partial pressure of oxygen (PO2) in empty devices.
- A mathematical model predicted internal PO2 and islet viability based on external PO2.
- Islet viability was assessed by oxygen consumption rate (OCR) in explanted devices at varying densities.
Main Results:
- Internal PO2 in empty devices was ≤12 mmHg, even with vascularization.
- Islet viability was lower than predicted by the model.
- Apoptosis, indicated by caspase-3 co-localization, contributed to beta cell loss.
Conclusions:
- Oxygen levels within subcutaneous macroencapsulation devices are limited.
- Islet viability is inversely proportional to cell density within the device.
- Strategies to improve oxygenation are needed for successful islet macroencapsulation.
