Signaling of stem cell factor/c-kit receptor in the regulation of microglia
| dc.contributor.committeeMember | Fedoroff, Sergey | en_US |
| dc.creator | Zhang, Su-Chun | en_US |
| dc.date.accessioned | 2004-10-21T00:08:10Z | en_US |
| dc.date.accessioned | 2013-01-04T05:03:25Z | |
| dc.date.available | 1996-01-01T08:00:00Z | en_US |
| dc.date.available | 2013-01-04T05:03:25Z | |
| dc.date.created | 1996-01 | en_US |
| dc.date.issued | 1996-01-01 | en_US |
| dc.date.submitted | January 1996 | en_US |
| dc.description.abstract | Signaling between sum cell factor (SCF) produced by stroma cells and its receptor, encoded by c-kit, expressed by stem cells or progenitor cells, is required for the normal development of hematopoietic, melanogenic, and gametogenic cell lineages. SCF and c-kit are also expressed in the nervous system, but their role in the nervous system is unknown. Using immunocytochemistry, I found that SCF was produced mainly by neurons, whereas the c-kit receptor was expressed by some neurons that often make synapses with the SCF-producing neurons and by glial cells, suggesting that SCF/c-kit receptor plays a role in neuron-neuron interaction and in a paracrine interaction between the SCF-producing neurons and the c-kit-expressing glia. Microglia, isolated from neopallial cell cultures, expressed c-kit mRNA, as shown by Northern blot analysis, and protein, shown by Western blot and immunocytochemistry. The expression of c-kit receptor in microglia in culture was found to be subject to regulation by cytokines such as SCF, colony-stimulating factor-1 (CSF-1) and interferon γ (IFN-γ). Microglia in culture also expressed SCF, as demonstrated by Northern blot and immunocytochemistry. Stimulation of microglia by IFN-γ or CSF-1 upregulated SCF expression. Thus, an autocrine action through SCF and its c-kit receptor may occur in microglia, especially when microglia are stimulated by IFN-γ or CSF-1. Microglia in culture require CSF-1 for survival. Withdrawal of CSF-1 from culture medium causes microglial cell death, whereas I found that microglia were partially rescued by the addition of SCF. Moreover, at a high dosage, SCF maintained microglia in a bipolar or tripolar shape, a relatively quiescent state. Addition of SCF to microglia in culture increased the expression of mRNAs of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and ciliary neurotrophic factor (CNTF), whereas it did not affect mRNA expression of inflammatory cytokines, interleukin 1 (IL-1), tumor necrosis factor α (TNFα), and IL-6. Using a neuron-microglia co-culture system, I demonstrated that SCF-treated microglia supported cerebral cortical neuron survival and neurite outgrowth. These observations suggest that SCF maintains microglia in a quiescent state and that microglia in this state are trophic to neurons. Stimulation of microglia in culture by CSF-1 results in microglial proliferation. I found that SCF suppressed CSF-1-induced microglial proliferation in a dose-dependent manner. Stimulation of microglia by lipopolysaccharide (LPS) or IFN-γ induced significant mRNA expression of the inflammatory cytokines IL-1, TNFα, and IL-6. Addition of SCF together with IFN-γ suppressed the induction of IL-1 and TNFα mRNAs, but addition of SCF to microglia cultures increased the production of lipocortin-1 (LC-1), an anti-inflammatory cytokine. Hence, SCF in cultures of microglia suppresses the production of inflammatory cytokines and at the same time increases the production of anti-infammmatory cytokine. | en_US |
| dc.identifier.uri | http://hdl.handle.net/10388/etd-10212004-000810 | en_US |
| dc.language.iso | en_US | en_US |
| dc.title | Signaling of stem cell factor/c-kit receptor in the regulation of microglia | en_US |
| dc.type.genre | Thesis | en_US |
| dc.type.material | text | en_US |
| thesis.degree.department | Anatomy and Cell Biology | en_US |
| thesis.degree.discipline | Anatomy and Cell Biology | en_US |
| thesis.degree.grantor | University of Saskatchewan | en_US |
| thesis.degree.level | Doctoral | en_US |
| thesis.degree.name | Doctor of Philosophy (Ph.D.) | en_US |