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Gene expression analysis of macrophages derived from ankylosing spondylitis patients reveals interferon-gamma
Judith A Smith1, Michael D Barnes, Dihua Hong
1Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
Objective:
To determine whether macrophages, a type of cell implicated in the pathogenesis of ankylosing spondylitis (AS), exhibit a characteristic gene expression pattern.
Methods:
Macrophages were derived from the peripheral blood of 8 AS patients (median disease duration 13 years [range <1-43 years]) and 9 healthy control subjects over 7 days with the use of granulocyte-macrophage colony-stimulating factor. Cells were stimulated for 24 hours with interferon-gamma (IFN gamma; 100 units/ml), were left untreated for 24 hours, or were treated for 3 hours with lipopolysaccharide (LPS; 10 ng/ml). RNA was isolated and examined by microarray and real-time quantitative reverse transcription-polymerase chain reaction analysis.
Results:
Microarray analysis revealed 198 probe sets detecting the differential expression of 141 unique genes in untreated macrophages from AS patients compared with healthy controls. Clustering and principal components analysis clearly distinguished AS patients and controls. Of the differentially expressed genes, 78 (55%) were IFN-regulated, and their relative expression indicated a "reverse" IFN signature in AS patient macrophages, where IFN gamma-up-regulated genes were underexpressed and down-regulated genes were overexpressed. Treatment of macrophages with exogenous IFN gamma normalized the expression of these genes between patients and controls. In addition, the messenger RNA encoded by the IFN gamma gene was approximately 2-fold lower in AS patient macrophages at baseline (P = 0.004) and was poorly responsive to LPS (P = 0.018), as compared with healthy controls.
Conclusions:
Our findings reveal consistent differences in gene expression in macrophages from AS patients, with evidence of a striking "reverse" IFN signature. Together with poor expression and responsiveness of the IFN gamma gene, these results suggest that there may be a relative defect in IFN gamma gene regulation, with autocrine consequences and implications for disease pathogenesis.
Insights
Macrophages from ankylosing spondylitis patients show a distinct gene expression pattern, including a reversed interferon-gamma (IFN-γ) signature. This suggests a potential defect in IFN-γ gene regulation contributing to AS pathogenesis.
Area of Science:
- Immunology
- Genetics
- Rheumatology
Background:
- Macrophages play a role in ankylosing spondylitis (AS) pathogenesis.
- Understanding macrophage gene expression in AS is crucial for elucidating disease mechanisms.
Purpose of the Study:
- To investigate whether macrophages from AS patients exhibit a unique gene expression profile.
- To identify specific gene expression patterns associated with AS in macrophages.
Main Methods:
- Macrophages were differentiated from peripheral blood of AS patients and healthy controls.
- Cells were stimulated with interferon-gamma (IFN-γ) or lipopolysaccharide (LPS) or left untreated.
- Gene expression was analyzed using microarray and quantitative reverse transcription-polymerase chain reaction (qRT-PCR).
Main Results:
- 141 unique genes showed differential expression in AS patient macrophages compared to controls.
- A
- reverse
- interferon-gamma (IFN-γ) signature was observed, with altered expression of IFN-γ-regulated genes.
- IFN-γ gene expression was lower and less responsive to LPS in AS patient macrophages.
Conclusions:
- Macrophages from AS patients display consistent gene expression differences, characterized by a reverse IFN-γ signature.
- A potential defect in IFN-γ gene regulation in AS patients may contribute to disease pathogenesis.
- These findings highlight the role of macrophage dysfunction in AS.
