title: Symmetry recovery of cell-free layer after bifurcations of small arterioles in reduced flow conditions: effect of RBC aggregation.
abstract: Heterogeneous distribution of red blood cells (RBCs) in downstream vessels of arteriolar bifurcations can be promoted by an asymmetric formation of cell-free layer (CFL) in upstream vessels. Consequently, the CFL widths in subsequent downstream vessels become an important determinant for tissue oxygenation (O2) and vascular tone change by varying nitric oxide (NO) availability. To extend our previous understanding on the formation of CFL in arteriolar bifurcations, this study investigated the formation of CFL widths from 2 to 6 vessel-diameter (2D-6D) downstream of arteriolar bifurcations in the rat cremaster muscle (D = 51.5 ± 1.3 μm). As the CFL widths are highly influenced by RBC aggregation, the degree of aggregation was adjusted to simulate levels seen during physiological and pathological states. Our in vivo experimental results showed that the asymmetry of CFL widths persists along downstream vessels up to 6D from the bifurcating point. Moreover, elevated levels of RBC aggregation appeared to retard the recovery of CFL width symmetry. The required length of complete symmetry recovery was estimated to be greater than 11D under reduced flow conditions, which is relatively longer than interbifurcation distances of arterioles for vessel diameter of ∼50 μm. In addition, our numerical prediction showed that the persistent asymmetry of CFL widths could potentially result in a heterogeneous vasoactivity over the entire arteriolar network in such abnormal flow conditions.
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore;
authors.forename: Yan Cheng
authors.initials: YC
authors.lastname: Ng
authors.affiliation: Department of Biomedical Engineering, National University of Singapore, Singapore;
authors.forename: Bumseok
authors.initials: B
authors.lastname: Namgung
authors.affiliation: Department of Hematology, Singapore General Hospital, Singapore; and.
authors.forename: Sim Leng
authors.initials: SL
authors.lastname: Tien
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore;
authors.forename: Hwa Liang
authors.initials: HL
authors.lastname: Leo
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore; Department of Biomedical Engineering, National University of Singapore, Singapore; Department of Surgery, National University of Singapore, Singapore bieks@nus.edu.sg.
authors.forename: Sangho
authors.initials: S
authors.lastname: Kim
mesh_terms: D000818:Animals; D001160:Arterioles / Q000378:metabolism / Q000473:pathology*; D002449:Cell Aggregation; D004903:Erythrocyte Aggregation; D004912:Erythrocytes; D008297:Male; D008833:Microcirculation; D009569:Nitric Oxide / Q000378:metabolism*; D009929:Organ Size; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009569:Nitric Oxide; D010100:Oxygen
keywords: asymmetric flow; hemodynamics; microcirculation; wall shear stress