Nylon Mesh Device for Vitrification of Large Quantities of Rat Pancreatic Islets

The practical requirements of islet transplantation necessitate that a large quantity of pancreatic islets be cryopreserved for a long period of time in a simple and convenient manner. We cryopreserved rat islets (size range 101-150 mu m in mean diameter) by vitrification with either a Cryotop((R)) device or a empty set = 57-mu m nylon mesh device in units of 10 islets, or by conventional freezing with a Bicell((R)) vessel in units of 50 islets. Postwarm/thaw survival rates of the islets were 68.1%+/- 5.9%, 64.1%+/- 3.5%, and 47.7 +/- 1.2% following Cryotop vitrification, nylon mesh vitrification, and Bicell freezing, respectively (p < 0.05). Glucose-stimulated insulin secretion in the two vitrification groups (stimulus index [SI] = 3.1-3.9) was superior to that in the freezing group (SI = 0.8). Additional experiments involved scaling-up the cryopreservation process using the nylon mesh device in units of 10, 50, or 100 islets. Increased numbers of islets per device had no adverse effects on cryosurvival (58.6%-68.5%) or insulin secretion potential (SI = 2.8-4.2). As the nylon mesh device does not require the handling of individual islets with glass pipettes, pre-and postvitrification islet treatment is less complicated. Therefore, nylon mesh can serve as a simple cryodevice for the vitrification of large quantities of rat pancreatic islets.