Therapeutic angiogenesis by transplantation of induced pluripotent stem cell-derived Flk-1 positive cells.

BACKGROUND: Induced pluripotent stem (iPS) cells are the novel stem cell population induced from somatic cells. It is anticipated that iPS will be used in the expanding field of regenerative medicine. Here, we investigated whether implantation of fetal liver kinase-1 positive (Flk-1+) cells derived from iPS cells could improve angiogenesis in a mouse hind limb model of ischemia. RESULTS: Flk-1+ cells were induced from iPS cells after four to five days of culture. Hind limb ischemia was surgically induced and sorted Flk-1+ cells were directly injected into ischemic hind limbs of athymic nude mice. Revascularization of the ischemic hind limb was accelerated in mice that were transplanted with Flk-1+ cells compared with control mice, which were transplanted with vehicle, as evaluated by laser Doppler blood flowmetry. Transplantation of Flk-1+ cells also increased expression of VEGF mRNA in ischemic tissue compared to controls. CONCLUSIONS: Direct local implantation of iPS cell-derived Flk-1+ cells would salvage tissues from ischemia. These data indicate that iPS cells could be valuable in the therapeutic induction of angiogenesis.

Bidirectional induction toward paraxial mesodermal derivatives from mouse ES cells in chemically defined medium.

Embryonic stem cells (ESCs) are a renewable cell source of tissue for regenerative therapies. The addition of bone morphogenetic protein 4 (BMP4) to serum-free ESC cultures can induce primitive streak-like mesodermal cells. In differentiated mouse ESCs, platelet-derived growth factor receptor-alpha (PDGFR-alpha) and E-cadherin (ECD) are useful markers to distinguish between paraxial mesodermal progenitor cells and undifferentiated and endodermal cells, respectively. Here, we demonstrate methods for BMP4-mediated induction of paraxial mesodermal progenitors using PDGFR-alpha and ECD as markers for purification and characterization. Serum-free monolayers of ESCs cultured with BMP4 could efficiently promote paraxial mesodermal differentiation akin to embryonic mesodermal development. BMP4 treatment alone induced paraxial mesodermal progenitors that could differentiate into osteochondrogenic cells in vitro and in vivo. Furthermore, early removal of BMP4 followed by lithium chloride (LiCl) promoted the differentiation to myogenic progenitor cells. These myogenic progenitors were able to differentiate further in vitro into mature skeletal muscle cells. Thus, we successfully induced the efficient bidirectional differentiation of mouse ESCs toward osteochondrogenic and myogenic cell types using chemically defined conditions.