Human BM stem cells initiate angiogenesis in human islets in vitro

BM stem cells may have regenerative effects on islet function through angiogenesis. Human islets (100islet equivalent/mL) were cultured alone (control) or co-cultured (experimental group) with whole human BM (1 × 10(6) cells/mL) for 210 days. A protein array measuring angiogenesis factors found upregulated (experimental vs control, day 210) proteins levels of VEGF-a (535 vs 2 pg/mL), PDGF (280.79 vs 0 pg/mL), KGF (939 vs 8 pg/mL), TIMP-1 (4592 vs 4332 pg/mL) and angiogenin (506 vs 97 pg/mL). Lower protein levels of angiopoietin-2 (5 vs 709 pg/mL) were observed. Depletion of pro-angiogenesis factors in co-culture decreased the effects of BM-induced islet vascularization. Depletion of VEGF-a, eKGF and PDGF significantly reduced islet vascularization but individual depletion of KGF and PDGF had less effects overall on vessel formation. BM-induced vascularization showed significant endothelial cell distribution. Islet vascularization was linked to islet growth. A decrease in islet size indicated poor vascularization. Insulin release was evident in the tissues generated from human islet-BM co-culture throughout the entire culture period. Significant increase in insulin (28.66-fold vs control) and glucagon (24.4-fold vs control) gene expression suggest BM can induce endocrine cell regeneration. In conclusion, BM promotes human islet tissue regeneration via regulation of angiogenesis factors.