Effects of shear stress on morphology, adhesion and proliferation of human umbilical cord blood mesenchymal stem cells

Abstract

Objective To explore the effects of shear stress on morphology, adhesion and proliferation of human umbilical cord blood mesenchymal stem cells(hUC-MSCs). Methods The hUC-MSCs were cultured in vitro until confluence and then placed in a flow system.The cells were subjected to different shear stress (1, 2, 3, 4 dye/cm2) for 2 hours and 6 hours, and no shear stress treatment cells served as a static control.The morphological changes of hUC-MSCs in different groups were analyzed by phase contrast microscopy and immunofluorescence.The mRNA expression levels of intercellular adhesion molecule-1 (ICAM-1) and Ki67 were detected by real-time PCR. Results Compared with the static control group, the hUC-MSCs cells were arranged in the direction of fluid after treated with shear stress.The immunofluorescence results showed that the cytoskeletal protein F-actin filaments was prolonged after shear stress.The cytoskeleton was further elongated in the 2 dye/cm2 for 6 hours group when compared with 2 dye/cm2 for 2 hours group, and the cytoskeleton was loosened when time extended to 6 hours.Real-time PCR results showed that the relative expressions of ICAM-1 mRNA and Ki67 mRNA in the static control group and different gradient shear stress groups were significantly different, with significant differences among them (F=17.141, P=0.000; F=11.336, P=0.001). The relative expression of ICAM-1 mRNA in the 1, 2, 3, 4 dye/cm2 shear stress group was 2.74±0.32, 9.77±1.19, 6.70±0.92 and 5.69±0.72, respectively, which was significantly higher than 1.00±0.28 in the static control group, with significant differences between them (all at P<0.05). The relative expression of Ki67 mRNA in the 3 dye/cm2 and 4 dye/cm2 shear stress group was 0.39±0.09 and 0.04±0.02, respectively, which was significantly lower than 1.00±0.24 in the static control group, with statistically significant differences between them (both at P<0.05). Conclusions After treated with fluid shear stress, hUC-MSCs are arranged in the direction of fluid.Shear stress can promote the adhesion of hUC-MSCs.As the increase of shear stress intensity, cell proliferation is inhibited. Key words: Fluid shear stress; Human umbilical cord blood mesenchymal stem cells; Corneal endothelial cells; Intercellular adhesion molecule-1