Umbilical Cord Blood-Derived Aldehyde Dehydrogenase-Expressing Progenitor Cells Promote Recovery from Acute Ischemic Injury

Umbilical cord blood (UCB) represents a readily available source of hematopoietic and endothelial precursors at early ontogeny. Understanding the proangiogenic functions of these somatic progenitor subtypes after transplantation is integral to the development of improved cell-based therapies to treat ischemic diseases. We used fluorescence-activated cell sorting to purify a rare (<0.5%) population of UCB cells with high aldehyde dehydrogenase (ALDHhi) activity, a conserved stem/progenitor cell function. ALDHhi cells were depleted of mature monocytes and T- and B-lymphocytes and were enriched for early myeloid (CD33) and stem cell-associated (CD34, CD133, and CD117) phenotypes. Although these cells were primarily hematopoietic in origin, UCB ALDHhi cells demonstrated a proangiogenic transcription profile and were highly enriched for both multipotent myeloid and endothelial colony-forming cells in vitro. Coculture of ALDHhi cells in hanging transwells promoted the survival of human umbilical vein endothelial cells (HUVEC) under growth factor-free and serum-free conditions. On growth factor depleted matrigel, ALDHhi cells significantly increased tube-like cord formation by HUVEC. After induction of acute unilateral hind limb ischemia by femoral artery ligation, transplantation of ALDHhi cells significantly enhanced the recovery of perfusion in ischemic limbs. Despite transient engraftment in the ischemic hind limb, early recruitment of ALDHhi cells into ischemic muscle tissue correlated with increased murine von Willebrand factor blood vessel and CD31+ capillary densities. Thus, UCB ALDHhi cells represent a readily available population of proangiogenic progenitors that promote vascular regeneration. This work provides preclinical justification for the development of therapeutic strategies to treat ischemic diseases using UCB-derived ALDHhi mixed progenitor cells. STEM Cells2012;30:22482260