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Avgoustiniatos ES, Mueller KR, Scott III WE, Kitzmann JP, Suszynski TM, Perrault BE, Falde EJ, Balamurugan AN, Hering BJ, Putnam CW, Papas KK. Silicone rubber membrane devices permit islet culture at high density without adverse effects. Front Bioeng Biotechnol 2024; 12:1401608. [PMID: 39070161 PMCID: PMC11273363 DOI: 10.3389/fbioe.2024.1401608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Accepted: 06/21/2024] [Indexed: 07/30/2024] Open
Abstract
Introduction Conventional culture conditions, such as in T-flasks, require that oxygen diffuse through the medium to reach the islets; in turn, islet surface area density is limited by oxygen availability. To culture a typical clinical islet preparation may require more than 20 T-175 flasks at the standard surface area density of 200 IE/cm2. To circumvent this logistical constraint, we tested islets cultured on top of silicon gas-permeable (GP) membranes which place islets in close proximity to ambient oxygen. Methods Oxygenation of individual islets under three culture conditions, standard low-density, non-GP high density, and GP high density, were first modeled with finite element simulations. Porcine islets from 30 preparations were cultured for 2 days in devices with GP membrane bottoms or in paired cultures under conventional conditions. Islets were seeded at high density (HD, ∼4000 IE/cm2, as measured by DNA) in both GP and non-GP devices. Results In simulations, individual islets under standard culture conditions and high density cultures on GP membranes were both well oxygenated whereas non-GP high density cultured islets were anoxic. Similarly, compared to the non-GP paired controls, islet viability and recovery were significantly increased in HD GP cultures. The diabetes reversal rate in nude diabetic mice was similar for HD GP devices and standard cultures but was minimal with non-GP HD cultures. Discussion Culturing islets in GP devices allows for a 20-fold increase of islet surface area density, greatly simplifying the culture process while maintaining islet viability and metabolism.
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Affiliation(s)
| | - Kate R. Mueller
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
| | - William E. Scott III
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
| | - Jennifer P. Kitzmann
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson, AZ, United States
| | - Thomas M. Suszynski
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
| | - Brian E. Perrault
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
| | - Eric J. Falde
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
| | - A. N. Balamurugan
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
| | - Bernhard J. Hering
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
| | - Charles W. Putnam
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson, AZ, United States
| | - Klearchos K. Papas
- Department of Surgery, Schulze Diabetes Institute, University of Minnesota, Minneapolis, MN, United States
- Department of Surgery, Institute for Cellular Transplantation, University of Arizona, Tucson, AZ, United States
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2
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Torres E, Wang P, Kantesaria S, Jenkins P, DelaBarre L, Cosmo Pizetta D, Froelich T, Steyn L, Tannús A, Papas KK, Sakellariou D, Garwood M. Development of a compact NMR system to measure pO 2 in a tissue-engineered graft. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 357:107578. [PMID: 37952431 PMCID: PMC10787953 DOI: 10.1016/j.jmr.2023.107578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Revised: 10/19/2023] [Accepted: 10/25/2023] [Indexed: 11/14/2023]
Abstract
Cellular macroencapsulation devices, known as tissue engineered grafts (TEGs), enable the transplantation of allogeneic cells without the need for life-long systemic immunosuppression. Islet containing TEGs offer promise as a potential functional cure for type 1 diabetes. Previous research has indicated sustained functionality of implanted islets at high density in a TEG requires external supplementary oxygen delivery and an effective tool to monitor TEG oxygen levels. A proven oxygen-measurement approach employs a 19F oxygen probe molecule (a perfluorocarbon) implanted alongside therapeutic cells to enable oxygen- and temperature- dependent NMR relaxometry. Although the approach has proved effective, the clinical translation of 19F oxygen relaxometry for TEG monitoring will be limited by the current inaccessibility and high cost of MRI. Here, we report the development of an affordable, compact, and tabletop 19F NMR relaxometry system for monitoring TEG oxygenation. The system uses a 0.5 T Halbach magnet with a bore diameter (19 cm) capable of accommodating the human arm, a potential site of future TEG implantation. 19F NMR relaxometry was performed while controlling the temperature and oxygenation levels of a TEG using a custom-built perfusion setup. Despite the magnet's nonuniform field, a pulse sequence of broadband adiabatic full-passage pulses enabled accurate 19F longitudinal relaxation rate (R1) measurements in times as short as ∼2 min (R1 vs oxygen partial pressure and temperature (R2 > 0.98)). The estimated sensitivity of R1 to oxygen changes at 0.5 T was 1.62-fold larger than the sensitivity previously reported for 16.4 T. We conclude that TEG oxygenation monitoring with a compact, tabletop 19F NMR relaxometry system appears feasible.
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Affiliation(s)
- Efraín Torres
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA; Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
| | - Paul Wang
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA; Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
| | - Saurin Kantesaria
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA; Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
| | - Parker Jenkins
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA; Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA.
| | - Lance DelaBarre
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA.
| | - Daniel Cosmo Pizetta
- Centro de Imagens e Espectroscopia por Ressonância Magnética - CIERMag - São Carlos Physics Institute, University of São Paulo - IFSC-USP, São Carlos, Brazil.
| | - Taylor Froelich
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA.
| | - Leah Steyn
- Department of Surgery, The University of Arizona, Tucson, AZ, USA.
| | - Alberto Tannús
- Centro de Imagens e Espectroscopia por Ressonância Magnética - CIERMag - São Carlos Physics Institute, University of São Paulo - IFSC-USP, São Carlos, Brazil.
| | | | | | - Michael Garwood
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, Minneapolis, MN, USA.
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Einstein SA, Steyn LV, Weegman BP, Suszynski TM, Sambanis A, O'Brien TD, Avgoustiniatos ES, Firpo MT, Graham ML, Janecek J, Eberly LE, Garwood M, Putnam CW, Papas KK. Hypoxia within subcutaneously implanted macroencapsulation devices limits the viability and functionality of densely loaded islets. FRONTIERS IN TRANSPLANTATION 2023; 2:1257029. [PMID: 38993891 PMCID: PMC11235299 DOI: 10.3389/frtra.2023.1257029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 10/20/2023] [Indexed: 07/13/2024]
Abstract
Introduction Subcutaneous macroencapsulation devices circumvent disadvantages of intraportal islet therapy. However, a curative dose of islets within reasonably sized devices requires dense cell packing. We measured internal PO2 of implanted devices, mathematically modeled oxygen availability within devices and tested the predictions with implanted devices containing densely packed human islets. Methods Partial pressure of oxygen (PO2) within implanted empty devices was measured by noninvasive 19F-MRS. A mathematical model was constructed, predicting internal PO2, viability and functionality of densely packed islets as a function of external PO2. Finally, viability was measured by oxygen consumption rate (OCR) in day 7 explants loaded at various islet densities. Results In empty devices, PO2 was 12 mmHg or lower, despite successful external vascularization. Devices loaded with human islets implanted for 7 days, then explanted and assessed by OCR confirmed trends proffered by the model but viability was substantially lower than predicted. Co-localization of insulin and caspase-3 immunostaining suggested that apoptosis contributed to loss of beta cells. Discussion Measured PO2 within empty devices declined during the first few days post-transplant then modestly increased with neovascularization around the device. Viability of islets is inversely related to islet density within devices.
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Affiliation(s)
- Samuel A Einstein
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
- Department of Radiology, The Pennsylvania State University, Hershey, PA, United States
| | - Leah V Steyn
- Department of Surgery, University of Arizona, Tucson, AZ, United States
| | - Bradley P Weegman
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
- Sylvatica Biotech Inc., North Charleston, SC, United States
| | - Thomas M Suszynski
- Department of Plastic Surgery, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Athanassios Sambanis
- Department of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States
| | - Timothy D O'Brien
- Veterinary Population Medicine Department, University of Minnesota, Saint Paul, MN, United States
- Department of Medicine, Stem Cell Institute, University of Minnesota, Minneapolis, MN, United States
| | | | - Meri T Firpo
- Department of Medicine, Stem Cell Institute, University of Minnesota, Minneapolis, MN, United States
| | - Melanie L Graham
- Veterinary Population Medicine Department, University of Minnesota, Saint Paul, MN, United States
- Department of Surgery, Preclinical Research Center, University of Minnesota, Saint Paul, MN, United States
| | - Jody Janecek
- Department of Surgery, Preclinical Research Center, University of Minnesota, Saint Paul, MN, United States
| | - Lynn E Eberly
- Division of Biostatistics, University of Minnesota, Minneapolis, MN, United States
| | - Michael Garwood
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
| | - Charles W Putnam
- Department of Surgery, University of Arizona, Tucson, AZ, United States
| | - Klearchos K Papas
- Department of Surgery, University of Arizona, Tucson, AZ, United States
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Puskar A, Saadah B, Rauf A, Kasperek SR, Umair M. A primer on contrast agents for magnetic resonance imaging of post‐procedural and follow‐up imaging of islet cell transplant. NANO SELECT 2023. [DOI: 10.1002/nano.202200147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
Affiliation(s)
- Anessa Puskar
- Carle Illinois College of Medicine Urbana‐Champaign Urbana Illinois USA
| | - Bara Saadah
- Carle Illinois College of Medicine Urbana‐Champaign Urbana Illinois USA
| | - Asad Rauf
- Carle Illinois College of Medicine Urbana‐Champaign Urbana Illinois USA
| | | | - Muhammad Umair
- Department of Radiology Johns Hopkins Baltimore Maryland USA
- Department of Biomedical Engineering University of Illinois Urbana‐Champaign Urbana Illinois USA
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Glieberman AL, Pope BD, Melton DA, Parker KK. Building Biomimetic Potency Tests for Islet Transplantation. Diabetes 2021; 70:347-363. [PMID: 33472944 PMCID: PMC7881865 DOI: 10.2337/db20-0297] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 11/12/2020] [Indexed: 12/12/2022]
Abstract
Diabetes is a disease of insulin insufficiency, requiring many to rely on exogenous insulin with constant monitoring to avoid a fatal outcome. Islet transplantation is a recent therapy that can provide insulin independence, but the procedure is still limited by both the availability of human islets and reliable tests to assess their function. While stem cell technologies are poised to fill the shortage of transplantable cells, better methods are still needed for predicting transplantation outcome. To ensure islet quality, we propose that the next generation of islet potency tests should be biomimetic systems that match glucose stimulation dynamics and cell microenvironmental preferences and rapidly assess conditional and continuous insulin secretion with minimal manual handing. Here, we review the current approaches for islet potency testing and outline technologies and methods that can be used to arrive at a more predictive potency test that tracks islet secretory capacity in a relevant context. With the development of potency tests that can report on islet secretion dynamics in a context relevant to their intended function, islet transplantation can expand into a more widely accessible and reliable treatment option for individuals with diabetes.
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Affiliation(s)
- Aaron L Glieberman
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA
| | - Benjamin D Pope
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA
| | - Douglas A Melton
- Harvard Department of Stem Cell and Regenerative Biology, Cambridge, MA
- Harvard Stem Cell Institute, Cambridge, MA
| | - Kevin Kit Parker
- Disease Biophysics Group, Wyss Institute for Biologically Inspired Engineering, Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA
- Harvard Stem Cell Institute, Cambridge, MA
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Biswas B, Singh PC. The role of fluorocarbon group in the hydrogen bond network, photophysical and solvation dynamics of fluorinated molecules. J Fluor Chem 2020. [DOI: 10.1016/j.jfluchem.2019.109414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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7
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Suszynski TM, Rohrich RJ, Sieber DA, Boyd TG, Thornton JF, Teotia SS, Cunningham BL, Van Beek AL. Bioengineered Approach to the Design of a Fat Graft Based on Mathematical Modeling that Predicts Oxygen Delivery. Plast Reconstr Surg 2019; 143:1648-1655. [DOI: 10.1097/prs.0000000000005626] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Oxygenation strategies for encapsulated islet and beta cell transplants. Adv Drug Deliv Rev 2019; 139:139-156. [PMID: 31077781 DOI: 10.1016/j.addr.2019.05.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 04/19/2019] [Accepted: 05/04/2019] [Indexed: 02/06/2023]
Abstract
Human allogeneic islet transplantation (ITx) is emerging as a promising treatment option for qualified patients with type 1 diabetes. However, widespread clinical application of allogeneic ITx is hindered by two critical barriers: the need for systemic immunosuppression and the limited supply of human islet tissue. Biocompatible, retrievable immunoisolation devices containing glucose-responsive insulin-secreting tissue may address both critical barriers by enabling the more effective and efficient use of allogeneic islets without immunosuppression in the near-term, and ultimately the use of a cell source with a virtually unlimited supply, such as human stem cell-derived β-cells or xenogeneic (porcine) islets with minimal or no immunosuppression. However, even though encapsulation methods have been developed and immunoprotection has been successfully tested in small and large animal models and to a limited extent in proof-of-concept clinical studies, the effective use of encapsulation approaches to convincingly and consistently treat diabetes in humans has yet to be demonstrated. There is increasing consensus that inadequate oxygen supply is a major factor limiting their clinical translation and routine implementation. Poor oxygenation negatively affects cell viability and β-cell function, and the problem is exacerbated with the high-density seeding required for reasonably-sized clinical encapsulation devices. Approaches for enhanced oxygen delivery to encapsulated tissues in implantable devices are therefore being actively developed and tested. This review summarizes fundamental aspects of islet microarchitecture and β-cell physiology as well as encapsulation approaches highlighting the need for adequate oxygenation; it also evaluates existing and emerging approaches for enhanced oxygen delivery to encapsulation devices, particularly with the advent of β-cell sources from stem cells that may enable the large-scale application of this approach.
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Salg GA, Giese NA, Schenk M, Hüttner FJ, Felix K, Probst P, Diener MK, Hackert T, Kenngott HG. The emerging field of pancreatic tissue engineering: A systematic review and evidence map of scaffold materials and scaffolding techniques for insulin-secreting cells. J Tissue Eng 2019; 10:2041731419884708. [PMID: 31700597 PMCID: PMC6823987 DOI: 10.1177/2041731419884708] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 10/04/2019] [Indexed: 12/18/2022] Open
Abstract
A bioartificial endocrine pancreas is proposed as a future alternative to current treatment options. Patients with insulin-secretion deficiency might benefit. This is the first systematic review that provides an overview of scaffold materials and techniques for insulin-secreting cells or cells to be differentiated into insulin-secreting cells. An electronic literature survey was conducted in PubMed/MEDLINE and Web of Science, limited to the past 10 years. A total of 197 articles investigating 60 different materials met the inclusion criteria. The extracted data on materials, cell types, study design, and transplantation sites were plotted into two evidence gap maps. Integral parts of the tissue engineering network such as fabrication technique, extracellular matrix, vascularization, immunoprotection, suitable transplantation sites, and the use of stem cells are highlighted. This systematic review provides an evidence-based structure for future studies. Accumulating evidence shows that scaffold-based tissue engineering can enhance the viability and function or differentiation of insulin-secreting cells both in vitro and in vivo.
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Affiliation(s)
- Gabriel Alexander Salg
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Nathalia A Giese
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Miriam Schenk
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Felix J Hüttner
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Klaus Felix
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Pascal Probst
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Markus K Diener
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Thilo Hackert
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
| | - Hannes Götz Kenngott
- Department of General, Abdominal and Transplantation Surgery, Heidelberg University Hospital, Heidelberg, Germany
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10
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Suszynski TM, Sieber DA, Mueller K, Van Beek AL, Cunningham BL, Kenkel JM. Characterization of Adipose Tissue Product Quality Using Measurements of Oxygen Consumption Rate. Aesthet Surg J 2018; 38:442-447. [PMID: 29045546 DOI: 10.1093/asj/sjx160] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Fat grafting is a common procedure in plastic surgery but associated with unpredictable graft retention. Adipose tissue (AT) "product" quality is affected by the methods used for harvest, processing and transfer, which vary widely amongst surgeons. Currently, there is no method available to accurately assess the quality of AT. OBJECTIVES In this study, we present a novel method for the assessment of AT product quality through direct measurements of oxygen consumption rate (OCR). OCR has exhibited potential in predicting outcomes following pancreatic islet transplant. Our study aim was to reapportion existing technology for its use with AT preparations and to confirm that these measurements are feasible. METHODS OCR was successfully measured for en bloc and postprocessed AT using a stirred microchamber system. OCR was then normalized to DNA content (OCR/DNA), which represents the AT product quality. RESULTS Mean (±SE) OCR/DNA values for fresh en bloc and post-processed AT were 149.8 (± 9.1) and 61.1 (± 6.1) nmol/min/mg DNA, respectively. These preliminary data suggest that: (1) OCR and OCR/DNA measurements of AT harvested using conventional protocol are feasible; and (2) standard AT processing results in a decrease in overall AT product quality. CONCLUSIONS OCR measurements of AT using existing technology can be done and enables accurate, real-time, quantitative assessment of the quality of AT product prior to transfer. The availability and further validation of this type of assay could enable optimization of fat grafting protocol by providing a tool for the more detailed study of procedural variables that affect AT product quality.
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Affiliation(s)
- Thomas M Suszynski
- Department of Plastic Surgery, University of Texas Southwestern, Dallas, TX
| | - David A Sieber
- plastic surgeon in private practice in San Francisco, CA
| | - Kathryn Mueller
- Division of Plastic and Reconstructive Surgery, University of Minnesota, Minneapolis, MN
| | - Allen L Van Beek
- Division of Plastic and Reconstructive Surgery, University of Minnesota, Minneapolis, MN
| | - Bruce L Cunningham
- Division of Plastic and Reconstructive Surgery, University of Minnesota, Minneapolis, MN
| | - Jeffrey M Kenkel
- Department of Plastic Surgery, University of Texas Southwestern, Dallas, TX
- Associate Editor of Aesthetic Surgery Journal
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11
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Einstein SA, Weegman BP, Kitzmann JP, Papas KK, Garwood M. Noninvasive assessment of tissue-engineered graft viability by oxygen-17 magnetic resonance spectroscopy. Biotechnol Bioeng 2017; 114:1118-1121. [PMID: 27869295 PMCID: PMC5459307 DOI: 10.1002/bit.26227] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 10/27/2016] [Accepted: 11/14/2016] [Indexed: 02/05/2023]
Abstract
Transplantation of macroencapsulated tissue-engineered grafts (TEGs) is being investigated as a treatment for type 1 diabetes, but there is a critical need to measure TEG viability both in vitro and in vivo. Oxygen deficiency is the most critical issue preventing widespread implementation of TEG transplantation and delivery of supplemental oxygen (DSO) has been shown to enhance TEG survival and function in vivo. In this study, we demonstrate the first use of oxygen-17 magnetic resonance spectroscopy (17 O-MRS) to measure the oxygen consumption rate (OCR) of TEGs and show that in addition to providing therapeutic benefits to TEGs, DSO with 17 O2 can also enable measurements of TEG viability. Macroencapsulated TEGs containing βTC3 murine insulinoma cells were prepared with three fractional viabilities and provided with 17 O2 . Cellular metabolism of 17 O2 into nascent mitochondrial water (H217 O) was monitored by 17 O-MRS and, from the measured data, OCR was calculated. For comparison, OCR was simultaneously measured on a separate, but equivalent sample of cells with a well-established stirred microchamber technique. OCR measured by 17 O-MRS agreed well with measurements made in the stirred microchamber device. These studies confirm that 17 O-MRS can quantify TEG viability noninvasively. Biotechnol. Bioeng. 2017;114: 1118-1121. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Samuel A Einstein
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, 2021 Sixth Street SE, Minneapolis, Minnesota, 55455
| | - Bradley P Weegman
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, 2021 Sixth Street SE, Minneapolis, Minnesota, 55455
| | | | | | - Michael Garwood
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota, 2021 Sixth Street SE, Minneapolis, Minnesota, 55455
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12
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Einstein SA, Weegman BP, Firpo MT, Papas KK, Garwood M. Development and Validation of Noninvasive Magnetic Resonance Relaxometry for the In Vivo Assessment of Tissue-Engineered Graft Oxygenation. Tissue Eng Part C Methods 2016; 22:1009-1017. [PMID: 27758135 PMCID: PMC5116663 DOI: 10.1089/ten.tec.2016.0106] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 09/26/2016] [Indexed: 11/12/2022] Open
Abstract
Techniques to monitor the oxygen partial pressure (pO2) within implanted tissue-engineered grafts (TEGs) are critically necessary for TEG development, but current methods are invasive and inaccurate. In this study, we developed an accurate and noninvasive technique to monitor TEG pO2 utilizing proton (1H) or fluorine (19F) magnetic resonance spectroscopy (MRS) relaxometry. The value of the spin-lattice relaxation rate constant (R1) of some biocompatible compounds is sensitive to dissolved oxygen (and temperature), while insensitive to other external factors. Through this physical mechanism, MRS can measure the pO2 of implanted TEGs. We evaluated six potential MRS pO2 probes and measured their oxygen and temperature sensitivities and their intrinsic R1 values at 16.4 T. Acellular TEGs were constructed by emulsifying porcine plasma with perfluoro-15-crown-5-ether, injecting the emulsion into a macroencapsulation device, and cross-linking the plasma with a thrombin solution. A multiparametric calibration equation containing R1, pO2, and temperature was empirically generated from MRS data and validated with fiber optic (FO) probes in vitro. TEGs were then implanted in a dorsal subcutaneous pocket in a murine model and evaluated with MRS up to 29 days postimplantation. R1 measurements from the TEGs were converted to pO2 values using the established calibration equation and these in vivo pO2 measurements were simultaneously validated with FO probes. Additionally, MRS was used to detect increased pO2 within implanted TEGs that received supplemental oxygen delivery. Finally, based on a comparison of our MRS data with previously reported data, ultra-high-field (16.4 T) is shown to have an advantage for measuring hypoxia with 19F MRS. Results from this study show MRS relaxometry to be a precise, accurate, and noninvasive technique to monitor TEG pO2 in vitro and in vivo.
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Affiliation(s)
- Samuel A. Einstein
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota
| | - Bradley P. Weegman
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota
| | - Meri T. Firpo
- Department of Medicine, Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota
| | | | - Michael Garwood
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota
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Shao Q, Ashkenazi S. Photoacoustic lifetime imaging for direct in vivo tissue oxygen monitoring. JOURNAL OF BIOMEDICAL OPTICS 2015; 20:036004. [PMID: 25748857 PMCID: PMC4351645 DOI: 10.1117/1.jbo.20.3.036004] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/12/2015] [Indexed: 05/09/2023]
Abstract
Measuring the partial pressure of oxygen (pO₂) in tissue may provide physicians with essential information about the physiological state of tissue. However, currently available methods for measuring or imaging tissue pO₂ have significant limitations, preventing them from being widely used in clinics. Recently, we have reported a direct and noninvasive in vivo imaging modality based on the photoacoustic lifetime which overcomes certain drawbacks of the existing methods. The technique maps the excited triplet state of oxygen-sensitive dye, thus reflecting the spatial and temporal distributions of tissue oxygen. Here, we present two studies which apply photoacoustic lifetime imaging (PALI) to monitor changes of tissue oxygen induced by external modulations. The first study modulates tissue oxygen by controlling the percentage of oxygen a normal mouse inhales. We demonstrate that PALI is able to reflect the change in oxygen level with respect to normal, oxygen-rich, and oxygen-poor breathing conditions. The second study involves an acute ischemia model using a thin thread tied around the hindlimb of a normal mouse to reduce the blood flow. PALI images were acquired before, during, and after the restriction. The drop of tissue pO₂ and recovery from hypoxia due to reperfusion were tracked and observed by PALI.
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Affiliation(s)
- Qi Shao
- University of Minnesota, Department of Biomedical Engineering, 312 Church Street SE, Minneapolis, Minnesota 55455, United States
- Address all correspondence to: Qi Shao, E-mail:
| | - Shai Ashkenazi
- University of Minnesota, Department of Biomedical Engineering, 312 Church Street SE, Minneapolis, Minnesota 55455, United States
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Atchison N, Swindlehurst G, Papas KK, Tsapatsis M, Kokkoli E. Maintenance of ischemic β cell viability through delivery of lipids and ATP by targeted liposomes. Biomater Sci 2014; 2:548-559. [PMID: 24653833 PMCID: PMC3955996 DOI: 10.1039/c3bm60094g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Islet transplantation is a promising treatment for type 1 diabetes, but despite the successes, existing challenges prevent widespread application. Ischemia, occurring during pancreas preservation and isolation, as well as after islet transplantation, decreases islet viability and function. We hypothesized that the liposomal delivery of adenosine triphosphate (ATP) could prevent the loss of cell viability during an ischemic insult. In this work we use a model β cell line, INS-1 to probe the liposome/cell interactions and examined the ability of liposomes functionalized with the fibronectin-mimetic peptide PR_b to facilitate the delivery of ATP to ischemic β cells. We demonstrate that PR_b increases the binding and internalization of liposomes to the β cells. Unexpectedly, when comparing the ability of PR_b liposomes with and without ATP to protect INS-1 cells from ischemia we found that both formulations increased cell survival. By probing the functional activity of ischemic cells treated with PR_b functionalized liposomes with and without ATP we find that both lipids and ATP play a role in maintaining cell metabolic activity after an ischemic insult and preventing cell necrosis. This approach may be beneficial for preventing ischemia related damage to islet cells, especially in the organ preservation stage.
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Affiliation(s)
- Nicole Atchison
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA
| | - Garrett Swindlehurst
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA. Fax: 612- 626-7246; Tel: 612-626-1185
| | | | - Michael Tsapatsis
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA. Fax: 612- 626-7246; Tel: 612-626-1185
| | - Efrosini Kokkoli
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN, USA. Fax: 612- 626-7246; Tel: 612-626-1185
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