Growth factor treatment and genetic manipulation stimulate neurogenesis and oligodendrogenesis by endogenous neural progenitors in the injured adult spinal cord.
Neurons and oligodendrocytes are highly vulnerable to various insults, and their spontaneous replacement occurs to only a limited extent after damage in the adult spinal cord. The environment of injured tissue is thus thought to restrict the regenerative capacity of endogenous neural stem/progenitor cells; strategies for overcoming such restrictions remain to be developed. Here, we combined growth factor treatment and genetic manipulation to stimulate neurogenesis and oligodendrogenesis by endogenous progenitors in vivo. The recombinant retrovirus pMXIG, which was designed to coexpress green fluorescent proteins (GFPs) and a neurogenic/gliogenic transcription factor, was directly injected into the injured spinal cord parenchyma to manipulate proliferative cells in situ. We found that cells expressing Olig2, Nkx2.2, and NG2 were enriched among virus-infected, GFP-positive (GFP+) cells. Moreover, a fraction of GFP+ cells formed neurospheres and differentiated into neurons, astrocytes, and oligodendrocytes in vitro, demonstrating that GFP retroviruses indeed infected endogenous neural progenitors in vivo. Neuronal differentiation of control virus-infected cells did not occur at a detectable level in the injured spinal cord. We found, however, that direct administration of fibroblast growth factor 2 and epidermal growth factor into lesioned tissue could induce a significant fraction of GFP-labeled cells to express immature neuronal markers. Moreover, retrovirus-mediated overexpression of the basic helix-loop-helix transcription factors Neurogenin2 and Mash1, together with growth factor treatment, enhanced the production and maturation of new neurons and oligodendrocytes, respectively. These results demonstrate that endogenous neural progenitors can be manipulated to replace neurons and oligodendrocytes lost to insults in the injured spinal cord.
Ohori
Yasuo
Y
Division of Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio 45229-3039, USA.
Yamamoto
Shin-ichi
S
Nagao
Motoshi
M
Sugimori
Michiya
M
Yamamoto
Naoya
N
Nakamura
Kozo
K
Nakafuku
Masato
M
D000818:Animals; D000941:Antigens / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D015316:Genetic Therapy / Q000379:methods; D005822:Genetic Vectors / Q000627:therapeutic use*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000494:pharmacology* / Q000627:therapeutic use; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D000076104:Oligodendrocyte Transcription Factor 2; D009836:Oligodendroglia / Q000166:cytology / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012190:Retroviridae / Q000235:genetics; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D013119:Spinal Cord Injuries / Q000503:physiopathology / Q000628:therapy*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism; D016896:Treatment Outcome; D029961:Zebrafish Proteins; D000099216:Chondroitin Sulfate Proteoglycan 4
D000941:Antigens; D051792:Basic Helix-Loop-Helix Proteins; D004815:Epidermal Growth Factor; D016222:Fibroblast Growth Factor 2; D049452:Green Fluorescent Proteins; D000090322:Homeobox Protein Nkx-2.2; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D000076104:Oligodendrocyte Transcription Factor 2; D011509:Proteoglycans; D014157:Transcription Factors; D029961:Zebrafish Proteins; D000099216:Chondroitin Sulfate Proteoglycan 4; C499318:Ascl1 protein, rat; C102938:Neurog2 protein, mouse; C000715627:Nkx2-2 protein, mouse; C000715628:Nkx2-2 protein, rat; C512773:Olig2 protein, mouse; C485184:enhanced green fluorescent protein; C000715630:nkx2.2b protein, zebrafish