Development of a novel microbead applicable to xenogeneic islet transplantation

Abstract

The bioartificial pancreas (BAP) is a promising new means of treatment for patients with type I diabetes. The BAP consists of islets of Langerhans (islets), enclosed in a semipermeable membrane, that are then implanted into a diabetic patient. The islets are protected from immune rejection and can control glucose metabolism for a considerable length of time. We have developed a microbead to be used in xenogeneic islet transplantation. The microbead is composed of a mixture of 5% w/v agarose and 10% w/v poly(styrene sulfonic acid) (PSSa). The microbeads were treated with Polybrene, resulting in the formation of a polyionic complex at the surface of the microbead that suppressed PSSa leakage. The surface of the microbead was also coated with chondroitin sulfate to enhance biocompatibility. One thousand microencapsulated hamster islets were intraperitoneally implanted in streptozotocin-induced diabetic mice, without the administration of immunosuppressive drugs. The graft survival periods of each recipient were 56, 58, 73, > 100, and > 100 days, respectively. The high polymer concentration (15% w/v) of the microbead effectively isolates the xenogeneic islets from the host immune system.