Increased intimal hyperplasia after carotid endarterectomy in spontaneously hypertensive rats

Association of Serum SorLA with Intimal Hyperplasia after Carotid Endarterectomy Operation: A Retrospective Analysis

BACKGROUND

To study the relevance between serum sorting protein-related receptor containing the low-density lipoprotein receptor class A (SorLA) and intimal hyperplasia (IH) after carotid endarterectomy (CEA) operation.

METHODS

Seventy-nine carotid artery stenosis patients receiving CEA operation from September 2013 to March 2015 were included. Serum SorLA level was detected by enzyme linked immunosorbent assay method preoperatively. All the 79 patients received regular follow-up to diagnose the IH of target lesions, postoperatively. Based on the follow-up data, the patients were divided into IH group (n = 10) and non-IH group (n = 69). Serum SorLA levels were analyzed using t-test. Receiver-operating characteristic curve was applied to determine the value of serum SorLA to predict the occurrence of IH after CEA operation.

RESULTS

Patients in severe IH group had a higher level of serum SorLA than patients in non-IH group (1.648 ± 0.246 ng/mL vs. 1.278 ± 0.281 ng/mL, P < 0.001). When 1.44 ng/mL was designated as the cutoff value of serum SorLA, the predicting value had a sensitivity of 90% and a specificity of 73.5%.

CONCLUSIONS

High serum SorLA level is related to IH after CEA operation. A serum SorLA level of 1.44 ng/mL can be used as a predicting index of postoperative IH.

Effects of Axial Stretch on Cell Proliferation and Intimal Thickness in Arteries in Organ Culture

Intimal hyperplasia (IH) remains the major cause of intermediate and long-term failure of vascular grafts and endovascular interventions. Arteries are subjected to a significant longitudinal stress in addition to the shear stress and tensile stress from the blood flow. The aim of this study was to determine the effect of axial stretch on cell proliferation and IH in arteries. Porcine carotid arteries, intact or endothelial cell (EC) denudated, were maintained ex vivo at different stretch ratios (1.3, 1.5, and 1.8) and flow rates (16 or 160 mL/min) while remaining at physiologic pressure for 7 days. The viability of the arteries was verified with norepinephrine, carbachol, and sodium nitroprusside stimulations, and the cell proliferation was detected using bromodeoxyuridine labeling and immunostaining. Our results showed that the axial stretch ratio did not significantly affect intimal thickness and cell proliferation in normal arteries. However, axial stretch increased the neointimal thickness in EC denudated arteries cultured under low flow conditions. The cell proliferation increased significantly in the intima and inner half of the media of the EC denudated arteries under normal or elevated axial stretch in comparison to intact arteries at the same stretch ratio. These results demonstrated that axial stretch with EC denudation and low flow increases neointimal formation and cell proliferation in the arteries.

Mechanical stress promotes the expression of smooth muscle-like properties in marrow stromal cells

OBJECTIVE

It is poorly understood what kind of factors are involved in lineage commitment and maturation of mesenchymal stem cells. The present study investigates whether mechanical stress promotes expression of smooth muscle cell (SMC)-specific cytoskeletal protein in marrow stromal cells.

METHODS

Fibroblast-like stromal cells expressing STRO-1 antigen were isolated from rat bone marrow by density gradient separation. After preincubation for 7, 14, or 21 days in static condition, cells were exposed to one of three types of fluid flow-induced mechanical forces (flow dominant, pressure dominant, or combined) for 36 hours. The expression of SMC-specific cytoskeletal protein [alpha smooth muscle actin (alphaSMA) and smooth muscle myosin heavy chain (SMMHC)] was evaluated by immunofluorescence staining and Western blotting.

RESULTS

The proportion of SMMHC-positive cells was increased with longer preincubation periods (p < 0.01 vs 7-day incubation) and by any types of mechanical stimulation (p < 0.01 vs static control condition). The SMMHC-positive fraction after exposure to pressure-dominant forces (0.9% +/- 0.2%, 2.9% +/- 0.9%, and 12.6% +/- 0.8% for 7, 14, and 21 days of preincubation) or to combined forces (1.2% +/- 0.2%, 3.1% +/- 1.6%, and 15.5% +/- 2.8%) was higher than after flow-dominant stimulation (0, 1.2% +/- 0.1%, and 7.2% +/- 2.0%) (p < 0.01). In Western blotting, pressure-dominant or combined stimulation upregulated alphaSMA and SMMHC expression compared to static control condition.

CONCLUSION

The long-term cell incubation and subsequent mechanical stimulation, especially compressive strain, promote expression of SMC-specific cytoskeletal protein in marrow stromal cells.

Cigarette smoke increases intimal hyperplasia and homocysteine in a rat carotid endarterectomy

BACKGROUND

Homocysteine and smoking are independent risks for CVD; however their importance in post-CEA intimal hyperplasia is unclear. We performed a CEA in rats exposed to cigarette smoke with the hypothesis that smoking would increase intimal hyperplasia that may be associated with an elevated serum homocysteine. Folic acid (FA) and the homocysteine metabolic enzymes MTHFR and CBS were used to test for the significance of homocysteine elevation.

MATERIALS AND METHODS

Rats underwent an open CEA. N = 13 rats received smoke exposure 2 weeks prior, and 2 weeks post-CEA and N = 12 received no smoke. Each group was divided into either control or an FA-added diet resulting in four groups. Rats were sacrificed at 2 weeks post-CEA; liver, urine, blood, and carotid arteries samples were obtained.

RESULTS

Smoked rats had increased urinary peak and trough cotinine levels versus non-smoke rats, which decreased with FA. Smoke exposure increased intimal hyperplasia versus non-smoke controls by nearly 120% (57.8 +/- 6.2 versus 26.8 +/- 5.4% luminal stenosis, P = 0.005). Smoke-exposed rats had an increased serum homocysteine versus non-smoke controls (8.3 +/- 0.8 versus 5.7 +/- 0.8 microm, P = 0.014). Smoked rats given FA had decreased serum homocysteine compared to the smoke group. Along with reductions in homocysteine, FA eliminated the increase in intimal hyperplasia seen with smoke exposure (33.5 +/- 6.1 versus 57.8 +/- 6.2% luminal stenosis, P = 0.03). CBS activity decreased in smoked rats by nearly 20% versus non-smoke rats. FA supplementation in smoked rats both (1) increased CBS activity and (2) decreased MTHFR compared to control non-smoke-exposure levels.

CONCLUSION

Smoking increases plasma homocysteine and post-CEA intimal hyperplasia. This suggests homocysteine has an etiological role in the intimal hyperplasia increase observed with smoking, since both were negated with FA.