title: Activation of Epac stimulates integrin-dependent homing of progenitor cells.
abstract: Cell therapy is a novel promising option for treatment of ischemic diseases. Administered endothelial progenitor cells (EPCs) are recruited to ischemic regions and improve neovascularization. However, the number of cells that home to ischemic tissues is restricted. The GTPase Rap1 plays an important role in the regulation of adhesion and chemotaxis. We investigated whether pharmacologic activation of Epac1, a nucleotide exchange protein for Rap1, which is directly activated by cAMP, can improve the adhesive and migratory capacity of distinct progenitor cell populations. Stimulation of Epac by a cAMP-analog increased Rap1 activity and stimulated the adhesion of human EPCs, CD34(+) hematopoietic progenitor cells, and mesenchymal stem cells (MSCs). Specifically, short-term stimulation with a specific Epac activator increased the beta2-integrin-dependent adhesion of EPCs to endothelial cell monolayers, and of EPC and CD34(+) cells to ICAM-1. Furthermore, the Epac activator enhanced the beta1-integrin-dependent adhesion of EPCs and MSCs to the matrix protein fibronectin. In addition, Epac1 activation induced the beta1- and beta2-integrin-dependent migration of EPCs on fibronectin and fibrinogen. Interestingly, activation of Epac rapidly increased lateral mobility of beta1- and beta2-integrins, thereby inducing integrin polarization, and stimulated beta1-integrin affinity, whereas the beta2-integrin affinity was not increased. Furthermore, prestimulation of EPCs with the Epac activator increased homing to ischemic muscles and neovascularization-promoting capacity of intravenously injected EPCs in the model of hind limb ischemia. These data demonstrate that activation of Epac1 increases integrin activity and integrin-dependent homing functions of progenitor cells and enhances their in vivo therapeutic potential. These results may provide a platform for the development of novel therapeutic approaches to improve progenitor cell homing.
authors.affiliation: Molecular Cardiology, Department of Internal Medicine III, J. W. Goethe University of Frankfurt, Theodor Stern-Kai 7, Frankfurt, Germany.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Carmona
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Chavakis
authors.forename: Ulrike
authors.initials: U
authors.lastname: Koehl
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Zeiher
authors.forename: Stefanie
authors.initials: S
authors.lastname: Dimmeler
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D018821:CD18 Antigens / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects; D051379:Mice; D008819:Mice, Nude; D018919:Neovascularization, Physiologic / Q000187:drug effects; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects
chemical_list: C473217:8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate; D018952:Antigens, CD34; D018821:CD18 Antigens; D016326:Extracellular Matrix Proteins; D020662:Guanine Nucleotide Exchange Factors; D018960:Hyaluronan Receptors; D019012:Integrin beta1; C116122:RAPGEF3 protein, human; D000242:Cyclic AMP