Cryopreservation of Insulin-Producing Cells Microencapsulated in Sodium Cellulose Sulfate P.B. Stiegler, V. Stadlbauer, S. Schaffellner, G. Halwachs, C. Lackner, O. Hauser, F. Iberer, and K. Tscheliessnigg ABSTRACT Introduction. Diabetes mellitus may be treated with pancreatic islet cell transplantation. The use of xenogenic islet cells may overcome the shortage of human donor organs. Microencapsulation seems to be a promising method for immunoprotection. Since isolation, purification, encapsulation, and transplantation of islet cells are labor-intensive, cryopreservation has emerged as an attractive system for islet banking. In this study sodium cellulose sulfate (NaCS), a novel method for microencapsulation of islet cells, was tested for its capability to protect cells during cryopreservation. Methods. HIT-T15 cells were microencapsulated in NaCS. Cells were frozen and thawed using three different media containing varying amounts of dimethylsulfoxide (DMSO) and glycerol. Cell viability and cell growth were monitored using 3-(-4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide before freezing and 1 week after thawing. Results. NaCS did not show any negative impact on the growth rates of encapsulated HIT-T15 cells compared with nonencapsulated controls. Nonencapsulated cells were adequately crypreserved by both DMSO- and glycerol-containing freezing media. DMSO was not suitable for cryopreservation of encapsulated HIT-T15 cells, whereas glycerol seemed to produce no considerable cell loss during freezing and thawing. Discussion. Islet banking of cells encapsulated in NaCS was feasible. Microencapsula- tion did not harm islet cell recovery. As NaCS is less immunogenic and more biocompat- ible than other materials used for microencapsulation, it may be a promising method for immunoisolation of islet cells to replace the endocrine pancreas in a physiological way. A T THE MOMENT 150 million people suffer from diabetes mellitus worldwide, a number that will dou- ble to the year 2025. 1 Unfortunately it has become apparent that late complications of diabetes mellitus cannot be totally prevented by exogenous insulin therapy. 2 One of the main limits to treating diabetes with whole organ pancreas transplantation or human islet transplantation is the lack of sufficient numbers of donor organs. 3,4 The use of xenogenic islet cells to replace the endocrine pancreas in a physiolog- ical way seems to be an alternative to alleviate the shortage of donor organs. 5,6 However, xenogenic cells have to be isolated from the host’s immune system to avoid hyperacute rejection. Microencapsulation is an effective method for immunoisolation. 7 Several materials have been used, such as alginates and polyethylene glycol membranes, which all show severe disadvantages. 8 –13 Dautzenberg et al 8 devel- oped a procedure for the preparation of sodium cellulose sulfate (NaCS) microcapsules that seem advantageous over the alginate system. 14,15 NaCS microcapsules are produced in a one-step procedure, 18 do not show any toxicity, 16 do not show a foreign body reaction, 17 and cells survive for a nearly unlimited time span. 18 NaCS has already been tested From the Department of Surgery, Division of Transplantation Surgery (P.B.S., S.S., F.I., K.T.), Graz, Department of Medicine, Division of Gastroenterology and Hepatology (V.S.), Department of Laboratory Medicine (G.H.), and Department of Pathology (C.L.), Medical University Graz, Graz, Austria; and Institution for Virology and Biomedicine (O.H.), University of Veterinary Medi- cine Vienna, Vienna, Austria. Address reprint requests to Philipp B. Stiegler, MD, Depart- ment of Surgery, Division of Transplantation Surgery, Auen- bruggerplatz 29, A-8036 Graz, Austria. E-mail: philipp.stiegler@ klinikum-graz.at 0041-1345/06/$–see front matter © 2006 by Elsevier Inc. All rights reserved. doi:10.1016/j.transproceed.2006.08.188 360 Park Avenue South, New York, NY 10010-1710 3026 Transplantation Proceedings, 38, 3026 –3030 (2006)