Cyclophosphamide's lack of hematopoietic stem cell toxicity and its unique effects on the immune system have prompted several investigators to explore its potential for the prevention of graft-versus-host disease (GVHD). In haploidentical hematopoietic stem cell transplants, post-transplant cyclophosphamide together with standard prophylaxis reduces the incidence of GVHD to acceptable rates without the need for T cell depletion. In matched related and unrelated donor settings, cyclophosphamide alone has produced encouraging results. In particular, the low incidence of chronic GVHD is noteworthy. Here, we present a review of the current understanding of the mechanism of action of post-transplant cyclophosphamide and summarize the clinical data on its use for the prevention of GVHD.

BM stem cells may have regenerative effects on islet function through angiogenesis. Human islets (100 islet equivalent/mL) were cultured alone (control) or co-cultured (experimental group) with whole human BM (1 × 106 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.