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The activated mesangial cell: a glomerular "myofibroblast"?
R J Johnson1, J Floege, A Yoshimura
1Department of Medicine, University of Washington, Seattle.
Abstract:
The glomerular mesangial cell may have several important beneficial functions in the normal glomerulus. These include the production of growth factors to allow normal cell turnover, the provision of structural support for the capillaries via the production of mesangial matrix, and the modulation of glomerular hemodynamics via their contractile properties. However, in various types of glomerular injury, the mesangial cell may acquire characteristics of a "myofibroblast", which may in fact be injurious to the glomerulus. These "activated" mesangial cells can be shown to be proliferating by one or more mechanisms that are mediated by platelets and that also involve the local production of platelet-derived growth factor. Like myofibroblasts in other tissues, the mesangial cell acquires smooth muscle cell-like properties, characterized by the de novo expression of alpha-smooth muscle actin, and by the development of fibroblast-like properties, characterized by the production of interstitial collagens in addition to normal mesangial matrix constituents. Identifying therapeutic strategies that prevent this phenotypic modulation of the mesangial cell may provide new ways to treat golmerular diseases.
Insights
Glomerular mesangial cells normally support kidney function but can become injurious when activated during injury. Targeting this harmful "myofibroblast" transformation offers new therapeutic avenues for glomerular diseases.
Area of Science:
- Nephrology
- Cell Biology
- Pathology
Background:
- Glomerular mesangial cells perform vital functions in normal glomeruli, including growth factor production, structural support via matrix synthesis, and hemodynamic modulation.
- In glomerular injury, mesangial cells can transform into a detrimental myofibroblast-like phenotype.
Purpose of the Study:
- To investigate the phenotypic modulation of glomerular mesangial cells during injury.
- To identify mechanisms driving mesangial cell activation and potential therapeutic targets.
Main Methods:
- Analysis of mesangial cell characteristics in glomerular injury models.
- Investigation of platelet-mediated proliferation and growth factor involvement.
- Assessment of alpha-smooth muscle actin expression and collagen production.
Main Results:
- Activated mesangial cells exhibit myofibroblast-like properties, including proliferation.
- Platelet-derived growth factor mediates mesangial cell proliferation.
- Transformed cells express alpha-smooth muscle actin and produce interstitial collagens.
Conclusions:
- The phenotypic switch of mesangial cells to a myofibroblast-like state contributes to glomerular injury.
- Preventing this mesangial cell modulation presents a potential therapeutic strategy for glomerular diseases.