Matrix metalloproteinase activity is required for activity-induced angiogenesis in rat skeletal muscle.
Proteolysis of the capillary basement membrane is a hallmark of inflammation-mediated angiogenesis, but it is undetermined whether proteolysis plays a critical role in the process of activity-induced angiogenesis. Matrix metalloproteinases (MMPs) constitute the major class of proteases responsible for degradation of basement membrane proteins. We observed significant elevations of mRNA and protein levels of both MMP-2 and membrane type 1 (MT1)-MMP (2.9 +/- 0.7- and 1.5 +/- 0.1-fold above control, respectively) after 3 days of chronic electrical stimulation of rat skeletal muscle. Inhibition of MMP activity via the inhibitor GM-6001 prevented the growth of new capillaries as assessed by the capillary-to-fiber ratio (1.34 +/- 0.08 in GM-6001-treated muscles compared with 1.69 +/- 0.03 in control 7-day-stimulated muscles). This inhibition correlated with a significant reduction in the number of capillaries with observable breaks in the basement membrane, as assessed by electron microscopy (0.27 +/- 0.27% in GM-6001-treated muscles compared with 3.72 +/- 0.65% in control stimulated muscles). Proliferation of capillary-associated cells was significantly elevated by 2 days and remained elevated throughout 14 days of stimulation. Capillary-associated cell proliferation during muscle stimulation was not affected by MMP inhibition (80.3 +/- 9.3 nuclei in control and 63.5 +/- 8.5 nuclei in GM-6001-treated animals). We conclude that MMP proteolysis of capillary basement membrane proteins is a critical component of physiological angiogenesis, and we postulate that capillary-associated proliferation precedes and occurs independently of endothelial cell sprout formation.
Haas
T L
TL
Department of Pathology, Yale University, New Haven, Connecticut 06515, USA. thaas@yorku.ca
Milkiewicz
M
M
Davis
S J
SJ
Zhou
A L
AL
Egginton
S
S
Brown
M D
MD
Madri
J A
JA
Hudlicka
O
O
D000818:Animals; D002196:Capillaries / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D002455:Cell Division / Q000187:drug effects; D004151:Dipeptides / Q000494:pharmacology; D004558:Electric Stimulation; D007150:Immunohistochemistry; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D011480:Protease Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats
D004151:Dipeptides; D061965:Matrix Metalloproteinase Inhibitors; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D011480:Protease Inhibitors; D012333:RNA, Messenger; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2