Differential expression and activity of matrix metalloproteinases during flow-modulated vein graft remodeling.
OBJECTIVE
While shear stress closely regulates vascular remodeling, the mediators of this process have been only partially elucidated. The current study examined the role of the gelatinases in flow-mediated vein graft intimal hyperplasia. We hypothesized that matrix metalloproteinase (MMP)-2 and MMP-9 expression and protein levels, relative to tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2, are upregulated in a flow-dependent manner during vein graft arterialization.


METHODS
Bilateral common carotid interposition vein grafting was performed in rabbits. Reduction in flow was achieved through unilateral ligation of the internal carotid artery and three of four branches of the external carotid artery. At 28 days grafts were harvested and analyzed for intimal area; MMP-2 and MMP-9, and TIMP-1 and TIMP-2 messenger RNA content, via quantitative reverse transcription polymerase chain reaction; and MMP-2 and MMP-9, and TIMP-1 and TIMP-2 protein concentrations, via both bioactivity assay and zymography.


RESULTS
Branch ligation resulted in a 10-fold difference in mean flow rate and accelerated development of intimal hyperplasia in a low-flow environment. Exposure of the vein graft to arterial hemodynamics induced a marked rise in MMP-9 mRNA levels, whereas only a modest increase in MMP-2 mRNA was observed. MMP-2 protein was 50 to 100 times more abundant than MMP-9, and was significantly upregulated in grafts that demonstrated enhanced intimal thickening. Immunohistochemistry demonstrated that MMP-2 was located throughout the myointima, whereas MMP-9 was localized almost exclusively to the region of endothelium. No differences in TIMP-1 and TIMP-2 mRNA or protein levels were detected between high-flow and low-flow grafts.


CONCLUSIONS
MMP-2 is the predominate gelatinase that regulates early vein graft remodeling. Despite a marked increase in MMP-9 gene expression, development of intimal hyperplasia after a reduction in wall shear rate correlates with an increase in MMP-2 protein levels. These data suggest differential regulatory mechanisms for proteases within the remodeling vein graft wall. Modulation of extracellular matrix biologic features may offer therapeutic strategies for the prevention of vein graft failure.
Berceli
Scott A
SA
Division of Vascular Surgery and the Malcom Randall Veterans Affairs Medical Center, Gainesville, Fla, USA. bercesa@mail.surgery.ufl.edu
Jiang
Zhihua
Z
Klingman
Nina V
NV
Pfahnl
Chun L
CL
Abouhamze
Zaher S
ZS
Frase
Constanza D
CD
Schultz
Gregory S
GS
Ozaki
C Keith
CK
D000818:Animals; D019917:Blood Vessel Prosthesis Implantation; D017536:Carotid Artery, Common / Q000601:surgery; D015870:Gene Expression; D006083:Graft Occlusion, Vascular / Q000473:pathology; D018056:Hemorheology; D006965:Hyperplasia; D007150:Immunohistochemistry; D007601:Jugular Veins / Q000637:transplantation; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism; D017539:Tunica Intima / Q000473:pathology*; D015854:Up-Regulation
D012333:RNA, Messenger; D019715:Tissue Inhibitor of Metalloproteinase-1; D019716:Tissue Inhibitor of Metalloproteinase-2; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9