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Micro/nanobubbles

Improving Pancreatic Islet Cell Survival for Transplantation

Sayadi, Lohrasb R. MD*; Alexander, Michael MS; Sorensen, Alexandria M. BS*; Sarantopoulos, Nikolaos BS*; Lau, Hien BS; Klopfer, Michael PhD; Ziegler, Mary E. PhD*; Banyard, Derek A. MD, MBA, MS*; Evans, Gregory R. D. MD, FACS*; Lakey, Jonathan R. T. PhD, MSM; Widgerow, Alan D. MBBCh, MMed, FCS*

doi: 10.1097/SAP.0000000000001954
Transplantation Surgery and Research
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Purpose The preservation of transplantable tissue is directly tied to and limited by the ischemia time. Micro/nanobubbles (MNBs) are miniature gaseous voids that allow for the oxygenation of tissue given their high oxygen-carrying capacity. One of the current limitations of islet cell transplantation for type 1 diabetes is poor islet survival, caused by hypoxia, after harvesting the cells from pancreata. As such, the purpose of this study was to elucidate whether MNBs, when added to standard culture medium, improve islet cell survival postharvest.

Materials and Methods Islet cells were harvested from Sprague-Dawley rat pancreas tissue via a standard collagenase digestion and gradient purification. To create the MNB solution, a shear-based generation system was used to produce both air- and oxygen-filled MNBs in standard Connaught Medical Research Laboratories (CMRL) medium. Four groups, consisting of 500 islet equivalents, were cultured with either the standard CMRL medium, macrobubble-CMRL, MNB (air)-CMRL, or MNB (O2)-CMRL, and they were incubated at 37°C. Each treatment solution was replenished 24 hours postincubation, and after 48 hours of culture, dithizone staining was used to determine the islet cell counts, and the viability was assessed using Calcein AM/propidium iodide staining.

Results Islet cells that were preserved in macrobubble-CMRL, MNB (air)-CMRL, and MNB (O2)-CMRL conditions showed an increased survival compared with those cultured with standard CMRL. The islet cells cultured in the MNB (air)-CMRL condition demonstrated the greatest cell survival compared with all other groups, including the pure oxygen-carrying MNBs. None of the MNB treatments significantly altered the viability of the islet cells compared to the control condition.

Conclusions The addition of MNBs to culture medium offers an innovative approach for the oxygenation of transplantable tissue, such as islet cells. This study demonstrated that MNBs filled with air provided the most optimal addition to the islet cell culture medium for improving islet cell survival amongst the treatment groups we tested. Given these findings, we hypothesize that MNBs may also improve the oxygenation and survival of a variety of other tissues, including fat grafts from lipoaspirate, chronic wounds, and solid organs.

From the *Center for Tissue Engineering, Department of Plastic Surgery

Departments of Surgery and Biomedical Engineering

Biomedical Engineering, University of California, Irvine, Orange, CA.

Received December 4, 2018, and accepted for publication, after revision March 5, 2019.

Conflicts of interest and sources of funding: No conflict of interest from any authors listed.

Reprints: Alan D. Widgerow, MBBCh, MMed, FCS, Center for Tissue Engineering, Department of Plastic Surgery, University of California, Irvine, Suite 108a Bldg 55, 101 S City Dr, Orange, CA 92868. E-mail: awidgero@uci.edu.

Online date: June 20, 2019

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