Bone marrow cells have been demonstrated to be useful in the maintenance of pancreatic islet &bgr; cell viability, structure, and/or function in culture for a sustained period. Bone marrow cells were also found to promote &bgr; cell growth while reducing inflammatory cytokine release and reduce apoptosis. Moreover, islet cells co-cultured with bone marrow cells were shown to retain insulin response function and to function in an islet cell transplant in a mouse model of diabetes to restore normal insulin secretion. Cord blood cells and isolated peripheral CD34+ blood cells were unable to support &bgr; islet cell growth or increase survival.