During the isolation process, the highly specialized islet vascular connections are severed (33). Immediately after transplantation, the islet graft is avascular and it takes several days to several weeks to re-establish blood flow through construction of new capillaries (34, 35), and there is decreased oxygen tension for up to 9 months post-transplantation (36). As a result, the graft is receiving much less than it’s normal oxygen requirements. Furthermore, the graft is only supplied with portal venous blood, which contains only 85% oxygen saturation, whereas arterial blood contains 96% oxygen saturation (42). This has deleterious effects on the islets, and inadequate blood supply in the post-transplant period is likely a major contributor
