Microglia overexpressing the macrophage colony-stimulating factor receptor are neuroprotective in a microglial-hippocampal organotypic coculture system.
Microglia with increased expression of the macrophage colony-stimulating factor receptor (M-CSFR; c-fms) are found surrounding plaques in Alzheimer's disease (AD) and in mouse models for AD and after ischemic or traumatic brain injury. Increased expression of M-CSFR causes microglia to adopt an activated state that results in proliferation, release of cytokines, and enhanced phagocytosis. To determine whether M-CSFR-induced microglial activation affects neuronal survival, we assembled a coculture system consisting of BV-2 microglia transfected to overexpress the M-CSFR and hippocampal organotypic slices treated with NMDA. Twenty-four hours after assembly of the coculture, microglia overexpressing M-CSFR proliferated at a higher rate than nontransfected control cells and exhibited enhanced migration toward NMDA-injured hippocampal cultures. Surprisingly, coculture with c-fms-transfected microglia resulted in a dramatic reduction in NMDA-induced neurotoxicity. Similar results were observed when cocultures were treated with the teratogen cyclophosphamide. Biolistic overexpression of M-CSFR on microglia endogenous to the organotypic culture also rescued neurons from excitotoxicity. Furthermore, c-fms-transfected microglia increased neuronal expression of macrophage colony-stimulating factor (M-CSF), the M-CSFR, and neurotrophin receptors in the NMDA-treated slices, as determined with laser capture microdissection. In the coculture system, direct contact between the exogenous microglia and the slice was necessary for neuroprotection. Finally, blocking expression of the M-CSF ligand by exogenous c-fms-transfected microglia with a hammerhead ribozyme compromised their neuroprotective properties. These results demonstrate a protective role for microglia overexpressing M-CSFR in our coculture system and suggest under certain circumstances, activated microglia can help rather than harm neurons subjected to excitotoxic and teratogen-induced injury.
Mitrasinovic
Olivera M
OM
Neuroscience Research Laboratories, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305, USA.
Grattan
Alicia
A
Robinson
Christopher C
CC
Lapustea
Nicolae B
NB
Poon
Clara
C
Ryan
Heather
H
Phong
Connie
C
Murphy
Greer M
GM
D000818:Animals; D019470:Biolistics / Q000379:methods; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques / Q000379:methods; D017077:Culture Media, Conditioned / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D005452:Fluoresceins; D015870:Gene Expression / Q000502:physiology; D006624:Hippocampus / Q000166:cytology*; D008070:Lipopolysaccharides / Q000633:toxicity; D016173:Macrophage Colony-Stimulating Factor / Q000172:deficiency / Q000378:metabolism; D051379:Mice; D042282:Microdissection / Q000379:methods; D017628:Microglia / Q000378:metabolism*; D016202:N-Methylaspartate / Q000633:toxicity; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000378:metabolism*; D009924:Organ Culture Techniques; D009930:Organic Chemicals; D011419:Propidium; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013997:Time Factors; D014162:Transfection / Q000379:methods
D017077:Culture Media, Conditioned; D018690:Excitatory Amino Acid Agonists; D005452:Fluoresceins; D008070:Lipopolysaccharides; D018696:Neuroprotective Agents; D009930:Organic Chemicals; D012333:RNA, Messenger; C435731:fluoro jade; D011419:Propidium; D016202:N-Methylaspartate; D016173:Macrophage Colony-Stimulating Factor; D016186:Receptor, Macrophage Colony-Stimulating Factor