Immuno-electron-microscopic localization of basic fibroblast growth factor in the dystrophic mdx mouse masseter muscle

Basic fibroblast growth factor (bFGF) is a potent angiogenic polypeptide. It promotes angiogenesis in vivo and in vitro by stimulating migration, proliferation and proteolytic activity of endothelial cells. Whereas several effects of exogenous bFGF on endothelial cells have been described, it has remained unclear how endogenous bFGF produced by vascular endothelial cells regulate angiogenesis.To further investigate functional implications of the distribution of bFGF, we undertook the present study. Our aims were (i) to identify the specific location of bFGF in endothelial cells using electron microscopy immunogold labeling technique (ii) to determine the distribution of bFGF in capillaries of different types of tissues.Tissue samples from sciatic nerve, hippocampus, adrenal gland and kidney of normal adult rats were fixed in 4% paraformaldehyde/1 to 5% glutaraldehyde and embedded in Spurr's resin. Ultrathin sections were labeled with either polyclonal (F3393-Sigma) or monoclonal antibodies (F6162-Sigma, C3316-ZymoGenetics) specific for bFGF using a two-step immunogold labeling method.

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Loss of cytoplasmic basic fibroblast growth factor from physiologically wounded myofibers of normal and dystrophic muscle

Journal of Cell Science ◽

10.1242/jcs.106.1.121 ◽

1993 ◽

Vol 106 (1) ◽

pp. 121-133 ◽

Cited By ~ 5

Author(s):

M.S. Clarke ◽

R. Khakee ◽

P.L. McNeil

Keyword(s):

Plasma Membrane ◽

Growth Factor ◽

Fibroblast Growth Factor ◽

Basic Fibroblast Growth Factor ◽

Plasma Membranes ◽

Mdx Mouse ◽

Storage Site ◽

Fibroblast Growth ◽

Mouse Muscle ◽

Cellular Environment

Using muscle as an in vivo model system, we have tested the hypothesis that basic fibroblast growth factor is released from a cytoplasmic storage site into the extra-cellular environment via diffusion through survivable, mechanically-induced plasma membrane disruptions. Normal and dystrophic (mdx) mouse muscle were studied. Strong immunostaining for bFGF was detected in the cytoplasm of myofibers of uninjured muscle fixed in situ by perfusion. By contrast, myofibers did not stain cytoplasmically for bFGF after suffering lethal disruptions of their plasma membranes caused by freezing and thawing followed by sectioning. Sub-lethal, transient disruptions of myofiber plasma membranes--termed plasma membrane ‘wounds’--were shown to be induced by needle puncture or exercise of muscle. Quantitative image analysis revealed that these wounded fibers contained significantly reduced levels of bFGF. Dystrophic exercised and unexercised muscle was found to possess an approximately 6-fold higher proportion of wounded myofibers than does normal muscle under equivalent conditions. Release of bFGF at a rate that is a direct function of the frequency of myofiber wounding may explain in part how a muscle adjusts its growth to meet changing mechanical demand as well as the pathological hypertrophy characteristic of certain stages of muscular dystrophy.

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