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Macrophage colony-stimulating factor mRNA and protein in atherosclerotic lesions of rabbits and humans
M E Rosenfeld1, S Ylä-Herttuala, B A Lipton
1Department of Medicine, University of California, San Diego, La Jolla 92093.
Abstract:
In this study, the authors demonstrate the expression of mRNA and the presence of protein for macrophage colony-stimulating factor (MCSF) in atherosclerotic lesions from humans and rabbits. In situ hybridization of serial sections of human fatty streaks demonstrated expression of MCSF mRNA by cells dispersed throughout the lesions. Immunocytochemical staining with a panel of MCSF-specific antibodies showed extensive cell-associated staining of all of the cell types in the lesions. Immunocytochemical studies of atherosclerotic lesions from Watanabe heritable hyperlipidemic (WHHL) and cholesterol-fed rabbits demonstrated a similar cell-associated pattern of staining. There was no MCSF-specific staining of aortas from normal rabbits or of cultured aortic smooth muscle cells from either humans or rabbits. Macrophage-derived foam cells (MFC) were isolated from the aortas of ballooned, cholesterol-fed rabbits. A Northern blot demonstrated that RNA isolated from the MFC hybridized with a human cDNA probe for MCSF. RNA from alveolar macrophages isolated simultaneously from the same rabbits did not hybridize with the MCSF probe. Conditioned media from an 18- to 24-hour incubation of the MFC contained colony-stimulating activity as demonstrated in a mouse bone marrow culture assay. Most of this colony-stimulating activity was neutralized by preincubating the conditioned media with an MCSF-specific antibody.
Insights
Macrophage colony-stimulating factor (MCSF) is expressed in human and rabbit atherosclerotic lesions. Macrophage-derived foam cells in these lesions produce MCSF, contributing to atherosclerosis progression.
Area of Science:
- Cardiovascular Biology
- Immunology
- Molecular Biology
Background:
- Atherosclerosis is a chronic inflammatory disease characterized by lipid accumulation and plaque formation in arteries.
- The role of specific growth factors, such as macrophage colony-stimulating factor (MCSF), in atherogenesis is not fully understood.
Purpose of the Study:
- To investigate the expression and cellular localization of MCSF in human and rabbit atherosclerotic lesions.
- To determine if macrophage-derived foam cells (MFC) in atherosclerotic lesions produce MCSF and exhibit colony-stimulating activity.
Main Methods:
- In situ hybridization to detect MCSF mRNA in human fatty streaks.
- Immunocytochemical staining using MCSF-specific antibodies in human and rabbit atherosclerotic lesions.
- Isolation of MFC from rabbit aortas and RNA analysis (Northern blot) for MCSF expression.
- Colony-stimulating activity assay of conditioned media from MFC.
Main Results:
- MCSF mRNA and protein were detected in various cell types within human and rabbit atherosclerotic lesions.
- No MCSF expression was observed in normal aortas or cultured smooth muscle cells.
- Isolated MFC from rabbits expressed MCSF mRNA and secreted colony-stimulating activity, which was neutralized by an MCSF-specific antibody.
Conclusions:
- MCSF is expressed within atherosclerotic lesions by multiple cell types, including macrophage-derived foam cells.
- MFC in atherosclerotic lesions are a source of MCSF, suggesting a role in promoting lesion progression and macrophage accumulation.