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Chronic Vasodilation Induces Matrix Metalloproteinase 9 (MMP‐9) Expression during Microvascular Remodeling in Rat Skeletal Muscle
Author(s) -
GIESON ERIC J.,
SKALAK THOMAS C.
Publication year - 2001
Publication title -
microcirculation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.793
H-Index - 83
eISSN - 1549-8719
pISSN - 1073-9688
DOI - 10.1111/j.1549-8719.2001.tb00155.x
Subject(s) - prazosin , microvessel , matrix metalloproteinase , blot , vasodilation , microcirculation , immunolabeling , skeletal muscle , endocrinology , medicine , chemistry , anatomy , immunohistochemistry , biology , receptor , antagonist , biochemistry , gene
Objective : The process of microvessel growth and remodeling depends on the presence of matrix metalloproteinases (MMPs) in a specific spatial pattern of expression. This study characterizes the spatial distribution of metalloproteinase‐9 (MMP‐9) expression during microvascular remodeling in the rat spinotrapezius muscle. Methods : Female Sprague‐Dawley rats (4 weeks old) were administered the α 1 ‐adrenergic blocker prazosin for 7 days to induce chronic vasodilation and associated increases in capillary and arteriolar density. MMP‐9 expression was analyzed by Western blotting analysis of microdissected regions of muscle and immunolabeling of muscle sections. Results : Capillary density expressed as both capillary‐to‐fiber ratio (C/F) and capillaries per mm 2 increased significantly ( p < 0.01) due to prazosin administration. Western blotting on microdissected regions of spinotrapezius muscle showed that there was an increase in MMP‐9 expression in prazosin‐treated animals. Additionally, the Western blots showed a presence of the activated form of MMP‐9 in regions of spinotrapezius muscle containing vessels on the order of capillaries and small arterioles. Immunohistochemistry demonstrated that MMP‐9 significantly increased in the muscles of treated animals in areas within the vessel walls of microvessels greater than 20 µm in diameter. However, interstitial MMP‐9 expression did not significantly increase with prazosin administration. Conclusions : These results demonstrate that the expression of MMP‐9 increases during in vivo microvascular remodeling in adult skeletal muscle. The MMP‐9 expression is limited to larger (>20‐µm diameter) microvessels, suggesting a role for MMP‐9 in the remodeling of such vessels during prazosin‐induced vasodilation and the subsequent capillary proliferation.