title: Human iPS cell-derived astrocyte transplants preserve respiratory function after spinal cord injury.
abstract: Transplantation-based replacement of lost and/or dysfunctional astrocytes is a promising therapy for spinal cord injury (SCI) that has not been extensively explored, despite the integral roles played by astrocytes in the central nervous system (CNS). Induced pluripotent stem (iPS) cells are a clinically-relevant source of pluripotent cells that both avoid ethical issues of embryonic stem cells and allow for homogeneous derivation of mature cell types in large quantities, potentially in an autologous fashion. Despite their promise, the iPS cell field is in its infancy with respect to evaluating in vivo graft integration and therapeutic efficacy in SCI models. Astrocytes express the major glutamate transporter, GLT1, which is responsible for the vast majority of glutamate uptake in spinal cord. Following SCI, compromised GLT1 expression/function can increase susceptibility to excitotoxicity. We therefore evaluated intraspinal transplantation of human iPS cell-derived astrocytes (hIPSAs) following cervical contusion SCI as a novel strategy for reconstituting GLT1 expression and for protecting diaphragmatic respiratory neural circuitry. Transplant-derived cells showed robust long-term survival post-injection and efficiently differentiated into astrocytes in injured spinal cord of both immunesuppressed mice and rats. However, the majority of transplant-derived astrocytes did not express high levels of GLT1, particularly at early times post-injection. To enhance their ability to modulate extracellular glutamate levels, we engineered hIPSAs with lentivirus to constitutively express GLT1. Overexpression significantly increased GLT1 protein and functional GLT1-mediated glutamate uptake levels in hIPSAs both in vitro and in vivo post-transplantation. Compared to human fibroblast control and unmodified hIPSA transplantation, GLT1-overexpressing hIPSAs reduced (1) lesion size within the injured cervical spinal cord, (2) morphological denervation by respiratory phrenic motor neurons at the diaphragm neuromuscular junction, and (3) functional diaphragm denervation as measured by recording of spontaneous EMGs and evoked compound muscle action potentials. Our findings demonstrate that hiPSA transplantation is a therapeutically-powerful approach for SCI.
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: ke.li@jefferson.edu.
authors.forename: Ke
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: elham.javed@jefferson.edu.
authors.forename: Elham
authors.initials: E
authors.lastname: Javed
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: Daniel.scura@jefferson.edu.
authors.forename: Daniel
authors.initials: D
authors.lastname: Scura
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: tamara.hala@jefferson.edu.
authors.forename: Tamara J
authors.initials: TJ
authors.lastname: Hala
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: suneil.seetharam@jefferson.edu.
authors.forename: Suneil
authors.initials: S
authors.lastname: Seetharam
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: aditi.falnikar@jefferson.edu.
authors.forename: Aditi
authors.initials: A
authors.lastname: Falnikar
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 855N. Wolfe St., Rangos 250, Baltimore, MD 21205, United States. Electronic address: jricha68@jhmi.edu.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Richard
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: Ashley.chorath@jefferson.edu.
authors.forename: Ashley
authors.initials: A
authors.lastname: Chorath
authors.affiliation: Department of Neurology, Johns Hopkins University School of Medicine, 855N. Wolfe St., Rangos 250, Baltimore, MD 21205, United States. Electronic address: nmaragak@jhmi.edu.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Maragakis
authors.affiliation: Department of Biology, Arcadia University, 450S. Easton Rd., 220 Boyer Hall, Glenside, PA 19038, United States. Electronic address: wright@arcadia.edu.
authors.forename: Megan C
authors.initials: MC
authors.lastname: Wright
authors.affiliation: Department of Neuroscience, Farber Institute for Neurosciences, Sidney Kimmel Medical College at Thomas Jefferson University, 900 Walnut Street, JHN 469, Philadelphia, PA 19107, United States. Electronic address: angelo.lepore@jefferson.edu.
authors.forename: Angelo C
authors.initials: AC
authors.lastname: Lepore
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001253:Astrocytes / Q000502:physiology* / Q000637:transplantation; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D003964:Diaphragm / Q000503:physiopathology; D004195:Disease Models, Animal; D027342:Excitatory Amino Acid Transporter 2; D005260:Female; D005786:Gene Expression Regulation; D050491:Glutamate Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000502:physiology* / Q000637:transplantation*; D051379:Mice; D008810:Mice, Inbred C57BL; D009469:Neuromuscular Junction / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000473:pathology / Q000601:surgery*
chemical_list: D027342:Excitatory Amino Acid Transporter 2; D050491:Glutamate Plasma Membrane Transport Proteins; C493397:SLC1A2 protein, human; D049452:Green Fluorescent Proteins
keywords: Astrocyte; Cervical spinal cord contusion; Glial progenitor; Glutamate transporter; Induced pluripotent stem cells