Mj. Ott et Bj. Ballermann, SHEAR STRESS-CONDITIONED, ENDOTHELIAL CELL-SEEDED VASCULAR GRAFTS - IMPROVED CELL ADHERENCE IN RESPONSE TO IN-VITRO SHEAR-STRESS, Surgery, 117(3), 1995, pp. 334-339
Background. Prosthetic vascular grafts with adherent endothelial cell
monolayers may prove useful for small-caliber vessel bypass. However,
endothelial cells adhere poorly to prosthetic graft material, and they
are stripped when exposed to in vivo shear stress. This study sought
to determine whether in vitro shear stress conditioning improves endot
helial cell adhesion and decreases thrombogenicity of endothelial cell
-seeded grafts. Methods. The lumens of 1.5 mm (inside diameter) spun;b
olyurethane polymer vascular grafts were seeded with bovine aortic end
othe[ial cells and cultured in vitro for 6 days with or without contin
uous laminar shear stress, first at I to 2 dynes/cm(2) for 3 days, the
n at approximately 25 dynes/cm(2) for 3 days. Grafts preconditioned by
shear stress and the static control grafts were then exposed to arter
ial shear stress at 25 dynes/cm(2) for 25 seconds. The number of dislo
dged cells was counted, and the grafts were examined by light and scan
ning electron microscopy. Whole blood clotting time in the grafts was
also determined. Results. Exposure of grafts to acute shear stress dis
lodged 1.35 x 10(6) +/- 0.44 x 10(6) cells from static grafts compared
with 1.05 x 10(4) +/- 0.16 x 10(4) cells from grafts preconditioned b
y shear stress. By light and electron microscopy an intact endothelial
monolayer was observed to cover the lumen of shear stress-conditioned
grafts, whereasfew cells remained on the luminal surface of grafts no
t previously exposed to shear stress. The clotting time in shear stres
s-conditioned grafts was significantly prolonged in relation to grafts
not exposed to shear stress. Conclusions. These findings show that en
dothelial cell adhesion and retention on vascular grafts in vitro is m
arkedly enhanced by preconditioning the seeded endothelial cell monola
yer with long-term shear stress. Consequently, vascular grafts contain
ing shear stress-conditioned endothelial monolayers are less thromboge
nic in vitro than small-caliber vascular grafts without intact endothe
lial cell monolayers.