title: Transdifferentiation of human fibroblasts to endothelial cells: role of innate immunity.
abstract: BACKGROUND
  Cell fate is fluid and may be altered experimentally by the forced expression of master regulators mediating cell lineage. Such reprogramming has been achieved with the use of viral vectors encoding transcription factors. We recently discovered that the viral vectors are more than passive vehicles for transcription factors because they participate actively in the process of nuclear reprogramming to pluripotency by increasing epigenetic plasticity. On the basis of this recognition, we hypothesized that small-molecule activators of toll-like receptor 3, together with external microenvironmental cues that drive endothelial cell (EC) specification, might be sufficient to induce transdifferentiation of fibroblasts into ECs (induced ECs).
  
  
  RESULTS
  We show that toll-like receptor 3 agonist Poly I:C, combined with exogenous EC growth factors, transdifferentiated human fibroblasts into ECs. These induced ECs were comparable to human dermal microvascular ECs in immunohistochemical, genetic, and functional assays, including the ability to form capillary-like structures and to incorporate acetylated low-density lipoprotein. Furthermore, induced ECs significantly improved limb perfusion and neovascularization in the murine ischemic hindlimb. Finally, using genetic knockdown studies, we found that the effective transdifferentiation of human fibroblasts to ECs requires innate immune activation.
  
  
  CONCLUSIONS
  This study suggests that manipulation of innate immune signaling may be generally used to modify cell fate. Because similar signaling pathways are activated by damage-associated molecular patterns, epigenetic plasticity induced by innate immunity may play a fundamental role in transdifferentiation during wound healing and regeneration. Finally, this study is a first step toward development of a small-molecule strategy for therapeutic transdifferentiation for vascular disease.
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Nazish
authors.initials: N
authors.lastname: Sayed
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Wing Tak
authors.initials: WT
authors.lastname: Wong
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Frank
authors.initials: F
authors.lastname: Ospino
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Shu
authors.initials: S
authors.lastname: Meng
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Jieun
authors.initials: J
authors.lastname: Lee
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Arshi
authors.initials: A
authors.lastname: Jha
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Phillip
authors.initials: P
authors.lastname: Dexheimer
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.).
authors.forename: Bruce J
authors.initials: BJ
authors.lastname: Aronow
authors.affiliation: From the Department of Cardiovascular Sciences, Houston Methodist Research Institute, Houston, TX (N.S., W.T.W., F.O., S.M., J.P.C.); Division of Cardiovascular Medicine, Stanford University, Stanford, CA (J.L., A.J.); and Division of Biomedical Informatics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH (P.D., B.J.A.). jpcooke@houstonmethodist.org.
authors.forename: John P
authors.initials: JP
authors.lastname: Cooke
mesh_terms: D000818:Animals; D054338:Cell Transdifferentiation / Q000502:physiology*; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology*; D055879:Gene Knock-In Techniques; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D011897:Random Allocation
keywords: endothelial cell; endothelial function; immune system; stem cell; transdifferentiation