Endothelial cell dynamics under pulsating flows: significance of high versus low shear stress slew rates (d(tau)/dt).
Shear stress modulates endothelial cell (EC) remodeling via realignment and elongation. We provide the first evidence that the upstroke slopes of pulsatile flow, defined as shear stress slew rates (positive d(tau)/dt), affect significantly the rates at which ECs remodel. We designed a novel flow system to isolate various shear stress slew rates by precisely controlling the frequency, amplitude, and time-averaged shear stress (tau(ave)) of pulsatile flow. Bovine aortic endothelial cell (BAEC) monolayers were exposed to three conditions: (1) pulsatile flow (1 Hz) at high slew rate (293 dyn/cm2 s), (2) pulsatile flow (1 Hz) at low slew rate (71 dyn/cm2s), and (3) steady laminar flow at d(tau)/dt = 0. All of the three conditions were operated at tau(ave) = 50 dyn/cm2. BAEC elongation and alignment were measured over 17 h. We were able to demonstrate the effects of shear stress slew rates ((tau)/dt) on EC remodeling at a fixed spatial shear stress gradient (d(tau)/dx). We found that pulsatile flow significantly increased the rates at which EC elongated and realigned, compared to steady flow at d(tau)/dt = 0. Furthermore, EC remodeling was faster in response to high than to low slew rates at a given tau(ave).
Hsiai
Tzung K
TK
Department of Biomedical Engineering and Cardiovascular Medicine, School of Engineering and Keck School of Medicine, University of Southern California, Los Angeles 90089-1451, USA. hsiai@usc.edu
Cho
Sung K
SK
Honda
Henry M
HM
Hama
Susan
S
Navab
Mohamad
M
Demer
Linda L
LL
Ho
Chih-Ming
CM
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000502:physiology; D002417:Cattle; D002482:Cellulose / Q000031:analogs & derivatives*; D004730:Endothelium, Vascular / Q000166:cytology* / Q000502:physiology*; D018056:Hemorheology / Q000295:instrumentation* / Q000379:methods; D040542:Mechanotransduction, Cellular / Q000502:physiology; D011673:Pulsatile Flow / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013780:Tetroses; D013997:Time Factors
D013780:Tetroses; C048468:cellotetraose; D002482:Cellulose