Modified subcutaneous tissue with neovascularization is useful as the sitefor pancreatic islet transplantation

The success rate of subcutaneous transplantation of pancreatic islets has b een extremely low. Insufficient oxygen supply to the grafted islets is one possible major obstacle to the preservation of graft function. This study a ttempted to use basic fibroblast growth factor (bFGF) in subcutaneous trans plantation to induce neovascularization and a sufficient blood flow around the space formed for grafted islets in the subcutaneous tissues. A bFGF-rel easing device was designed enclosing bFGF in a polyethylene terephthalate m esh bag coated with polyvinylalcohol hydrogel. In the vascularized group (n = 5), two bFGF-releasing devices were implanted bilaterally into the subcu taneous tissue of the back of streptozotocin-induced diabetic Lewis rats. O ne week after implantation, isolated rat islets (5000) were syngeneically t ransplanted subcutaneously after the removal of the devices. In the control group (n = 5), no devices were implanted and the same number of rat islets was transplanted directly. One week after the implantation of the devices into the test animals, a thick, well-vascularized capsule was observed in t he subcutaneous site. All vascularized recipient rats showed significant de creases in nonfasting blood glucose and maintained normoglycemia for more t han 1 month after islet transplantation. However, in the control group, all rats failed to achieve normoglycemia after transplantation. This study pro vides evidence that the subcutaneous tissue is a promising site for pancrea tic islet transplantation, offering convincing advantages in acceptability for diabetic recipients. Establishment of this subcutaneous islet transplan tation technique will afford some new perspectives on successful clinical i slet transplantation.