Expansion of Umbilical Cord Blood Aldehyde Dehydrogenase Expressing Cells Generates Myeloid Progenitor Cells that Stimulate Limb Revascularization

Uncompromised by chronic disease‐related comorbidities, human umbilical cord blood (UCB) progenitor cells with high aldehyde dehydrogenase activity (ALDH(hi) cells) stimulate blood vessel regeneration after intra‐muscular transplantation. However, implementation of cellular therapies using UCB ALDH(hi) cells for critical limb ischemia, the most severe form of severe peripheral artery disease, is limited by the rarity (<0.5%) of these cells. Our goal was to generate a clinically‐translatable, allogeneic cell population for vessel regenerative therapies, via ex vivo expansion of UCB ALDH(hi) cells without loss of pro‐angiogenic potency. Purified UCB ALDH(hi) cells were expanded >18‐fold over 6‐days under serum‐free conditions. Consistent with the concept that ALDH‐activity is decreased as progenitor cells differentiate, only 15.1% ± 1.3% of progeny maintained high ALDH‐activity after culture. However, compared to fresh UCB cells, expansion increased the total number of ALDH(hi) cells (2.7‐fold), CD34(+)/CD133(+) cells (2.8‐fold), and hematopoietic colony forming cells (7.7‐fold). Remarkably, injection of expanded progeny accelerated recovery of perfusion and improved limb usage in immunodeficient mice with femoral artery ligation‐induced limb ischemia. At 7 or 28 days post‐transplantation, mice transplanted with expanded ALDH(hi) cells showed augmented endothelial cell proliferation and increased capillary density compared to controls. Expanded cells maintained pro‐angiogenic mRNA expression and secreted angiogenesis‐associated growth factors, chemokines, and matrix modifying proteins. Coculture with expanded cells augmented human microvascular endothelial cell survival and tubule formation under serum‐starved, growth factor‐reduced conditions. Expanded UCB‐derived ALDH(hi) cells represent an alternative to autologous bone marrow as an accessible source of pro‐angiogenic hematopoietic progenitor cells for the refinement of vascular regeneration‐inductive therapies. Stem Cells Translational Medicine 2017;6:1607–1619