Ultrastructure and molecular histology of rabbit hind-limb collateral artery growth (arteriogenesis)

Abstract

Previous studies in the canine heart had shown that the growth of collateral arteries occurs via proliferative enlargement of pre-existing arteriolar connections (arteriogenesis). In the present study, we investigated the ultrastructure and molecular histology of growing and remodeling collateral arteries that develop after femoral artery occlusion in rabbits as a function of time from 2 h to 240 days after occlusion. Pre-existent arteriolar collaterals had a diameter of about 50 microm. They consisted of one to two layers of smooth muscle cells (SMCs) and were morphologically indistinguishable from normal arterioles. The stages of arteriogenesis consisted of arteriolar thinning, followed by transformation of SMCs from the contractile- into the proliferative- and synthetic phenotype. Endothelial cells (ECs) and SMCs proliferated, and SMCs migrated and formed a neo-intima. Intercellular adhesion molecule (ICAM-1) and vascular cell adhesion molecule (VCAM-1) showed early upregulation in ECs, which was accompanied by accumulation of blood-derived macrophages. Mitosis of ECs and SMCs started about 24 h after occlusion, whereas adhesion molecule expression and monocyte adhesion occurred as early as 12 h after occlusion, suggesting a role of monocytes in vascular cell proliferation. Treatment of rabbits with the pro-inflammatory cytokine MCP-1 increased monocyte adhesion and accelerated vascular remodeling. In vitro shear-stress experiments in cultured ECs revealed an increased phosphorylation of the focal contacts after 30 min and induction of ICAM-1 and VCAM-1 expression between 2 h and 6 h after shear onset, suggesting that shear stress may be the initiating event. We conclude that the process of arteriogenesis, which leads to the positive remodeling of an arteriole into an artery up to 12 times its original size, can be modified by modulators of inflammation.

DNA Methyltransferase 1–Dependent DNA Hypermethylation Constrains Arteriogenesis by Augmenting Shear Stress Set Point

“…Here, DNMT1 inhibition increased arteriogenic capacity by ≈44% in nonreversed segments, while there was no effect on reversed flow segments ( P =0.163), indicating that this response is not limited to the C57BL/6 strain. We also sought to determine whether this increased arteriogenic capacity in nonreversed flow segments following DNMT1 inhibition corresponded to altered macrophage recruitment, a necessary component of collateral artery growth45, 46, 47, 48, 49, 50, 52 in vivo. Nonreversed flow collateral segments exhibited a trend ( P =0.057) toward increased pericollateral Mac3 + macrophages in 5AZA‐treated mice (day 17 post FAL, 3 days of 5AZA treatment), corresponding to our previous in vitro results (Figure S7).…”

Arginase inhibition attenuates arteriogenesis and interferes with M2 macrophage accumulation

“…In recent studies, we have shown that Icam1 is differentially expressed during arteriogenesis and that blunted Icam1 expression as well as Icam1 deficiency is associated with less effective arteriogenesis and perivascular accumulation of macrophages. [4][5][6] In the current study, our qRT-PCR results demonstrated that administration of nor-NOHA abolished the differential expression of Icam1 in growing collaterals. These data are in accordance with results from Giri et al 31 showing that downregulation of arginase 2 in human umbilical vein endothelial cells abrogated leukocyte adhesion by blocking the expression of Icam1.…”

“…3 Animal models, mainly for peripheral arteriogenesis, evidenced that increased shear stress results in activation of the arteriolar endothelium with subsequent upregulation of monocyte chemoattractant protein-1 (MCP-1) as well as ICAM1 presenting the prerequisite for monocyte recruitment, adhesion, and extravasation. [4][5][6] After extravasation, monocytes mature to macrophages, whereby M1 as well as M2 macrophages have been described to contribute to vascular remodeling. 7 Interestingly, it has been shown that exogenously administrated nitric oxide (NO) donors promote arteriogenesis.…”

Nonviral monocyte chemoattractant protein-1 gene transfer improves arteriogenesis after femoral artery occlusion

“…Blood flow is redirected through these interconnecting collaterals resulting in the upregulation of endothelial adhesion molecules like intracellular adhesion molecule-1, vascular cell adhesion molecule-1, and selectins 6 as well as monocyte chemoattractant protein-1 (MCP-1). [7][8][9][10] Circulating monocytes activated by MCP-1 attach to endothelium, extravasate, accumulate in the vascular wall and differentiate into macrophages, secreting various cytokines and growth factors (eg basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), tumour necrosis factor-a; granulocytemacrophage colony-stimulating factor (GM-CSF) and MCP-1).…”

“…[7][8][9][10] Circulating monocytes activated by MCP-1 attach to endothelium, extravasate, accumulate in the vascular wall and differentiate into macrophages, secreting various cytokines and growth factors (eg basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), tumour necrosis factor-a; granulocytemacrophage colony-stimulating factor (GM-CSF) and MCP-1). 6,11,12 MCP-1 is a member of the CC-chemokine family. [13][14][15][16][17] It has been shown to stimulate arteriogenesis when applied exogenously as a continuous intra-arterial infusion, resulting in a 2.5-fold increase in the magnitude of the arteriogenic response in a rabbit model 18 and in an approximately two-fold increase in a porcine model of PAOD.…”