High shear stress suppresses proliferation and migration but promotes apoptosis of endothelial cells co-cultured with vascular smooth muscle cells via down-regulating MAPK pathway.

Background: Early neointimal hyperplasia of vein graft may be ameliorated via enhancing intravenous surface shear stress. Cellular processes including proliferation, apoptosis and migration of endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) may play very important roles in the process of neointimal hyperplasia of vein graft; and mitogen-activated protein kinase (MAPK) pathways including extracellular signal-regulated kinase (ERK1/2) and p38 pathways play vital roles in regulating a large variety of cellular processes. This study evaluated the impacts of shear stress and MAPK pathways on cellular processes of ECs in a co-culture system with VSMCs, and aimed to test the hypothesis that high shear stress suppresses proliferation and migration but promotes apoptosis of ECs co-cultured with VSMCs via down-regulating MAPK pathway.

Methods: Primary ECs and VSMCs derived from porcine great saphenous vein were collected, respectively. 4-7 generation of cells were used as work cells. ECs and VSMCs were co-cultured and synchronized under high and low shear stress using Parallel-Plate Flow Chamber system. And then, ECs co-cultured with VSMCs were incubated with U0126 (ERK1/2 inhibitor) or PD98059 (p38 inhibitor) under different shear stress. Proliferation, apoptosis and migration of ECs in a co-culture system with VSMCs were detected by 4,5-dimethyl-2-thiazolyl (MTT) assay and bromodeoxyuridine (BrdU) assay, fluorescent-activated cell sorting (FACS) technique, and Transwell assay separately. Each test repeated 3 times. Additionally, protein expressions of ERK1/2 and p38 MAPK were detected by using Western blot, respectively.

Results: Under higher level of shear stress condition, proliferation and migration of ECs co-cultured with VSMCs were suppressed, while cell apoptosis was promoted. And blocking ERK1/2 pathway by U0126 or blocking p38 pathway by PD98059, proliferation and migration of ECs co-cultured with VSMCs were further suppressed, while cell apoptosis was further promoted. Additionally, protein expressions of phosphorylation of ERK1/2 and p38MAPK were decreased under higher level of shear stress condition, and were further reduced by blocking ERK1/2 or p38 pathway under shear stress condition.

Conclusions: High shear stress may suppress proliferation and apoptosis of ECs in a co-culture system with VSMCs but promote cell migration via down-regulating ERK1/2 and p38 MAPK pathways.