Macrodevices (PEG-RGD/PEGDT) containing 4000 syngeneic islet equivalents were transplanted in the omentum with (VEGF) or without (Control) a vasculogenic hydrogel layer. Subjects were monitored for (a) nonfasting blood glucose and (b) body weight. (c, d) After 30 days, grafts were explanted to evaluate viability of encapsulated islets via live/dead staining (c: low magnification; d: high magnification), where (e) quantification of overall graft live/dead area illustrates the impact of macrodevice vascularization via a degradable vasculogenic layer. (f) Evaluation of live islet area percentage at gel edge vs. gel center demonstrates viability distribution between gel edge and center. Finite element analysis (FEA) theoretically predicted spatial variance (g–h) of oxygen tension within gels in vivo. Blood glucose and body weight evaluated by parametric unpaired t-test. Average area and percent islet area evaluated by two-way ANOVA with Sidak’s multiple comparisons test. N = 5. Error = SEM, scale bars panel C = 500 μm, panel D = 100 μm. * P < 0.05. N.S. = no significance