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Quant Imaging Med Surg. 2018 Mar;8(2):114-122. doi: 10.21037/qims.2018.02.06.

Magnetic particle imaging of islet transplantation in the liver and under the kidney capsule in mouse models.

Author information

1
Molecular Imaging Laboratory, MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
2
Precision Health Program, Department of Radiology, Michigan State University, East Lansing, MI, USA.
3
Department of Bioengineering, University of California at Berkeley, Berkeley, CA, USA.
4
Magnetic Insight, Inc., Alameda, CA, USA.
5
Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
6
Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA.
7
Institute for Quantitative Health Science and Engineering, Department of Biomedical Engineering, Michigan State University, East Lansing, MI, USA.

Abstract

Background:

Islet transplantation (Tx) represents the most promising therapy to restore normoglycemia in type 1 diabetes (T1D) patients to date. As significant islet loss has been observed after the procedure, there is an urgent need for developing strategies for monitoring transplanted islet grafts. In this report we describe for the first time the application of magnetic particle imaging (MPI) for monitoring transplanted islets in the liver and under the kidney capsule in experimental animals.

Methods:

Pancreatic islets isolated from Papio hamadryas were labeled with superparamagnetic iron oxides (SPIOs) and used for either islet phantoms or Tx in the liver or under the kidney capsule of NOD scid mice. MPI was used to image and quantify islet phantoms and islet transplanted experimental animals post-mortem at 1 and 14 days after Tx. Magnetic resonance imaging (MRI) was used to confirm the presence of labeled islets in the liver and under the kidney capsule 1 day after Tx.

Results:

MPI of labeled islet phantoms confirmed linear correlation between the number of islets and the MPI signal (R2=0.988). Post-mortem MPI performed on day 1 after Tx showed high signal contrast in the liver and under the kidney capsule. Quantitation of the signal supports islet loss over time, which is normally observed 2 weeks after Tx. No MPI signal was observed in control animals. In vivo MRI confirmed the presence of labeled islets/islet clusters in liver parenchyma and under the kidney capsule one day after Tx.

Conclusions:

Here we demonstrate that MPI can be used for quantitative detection of labeled pancreatic islets in the liver and under the kidney capsule of experimental animals. We believe that MPI, a modality with no depth attenuation and zero background tissue signal could be a suitable method for imaging transplanted islet grafts.

KEYWORDS:

Diabetes; iron oxide nanoparticle; islet transplantation (Tx); magnetic particle imaging (MPI); pancreatic islet

Conflict of interest statement

Conflicts of Interest: Dr. Patrick Goodwill, Prof. Steven Conolly, Dr. Daniel Hensley, Dr. Prachi Pandit and Dr. Jeff Gaudet hold equity interest in Magnetic Insight, Inc. In addition, Dr. Goodwill, Dr. Hensley, Dr. Pandit, and Dr. Gaudet receive income from Magnetic Insight, Inc.

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