Abstract
This study examined the effect of dextran-induced RBC aggregation on the venular flow in microvasculature. We utilized the laser speckle contrast imaging (LSCI) as a wide-field imaging technique to visualize the flow distribution in venules influenced by abnormally elevated levels of RBC aggregation at a network-scale level, which was unprecedented in previous studies. RBC aggregation in rats was induced by infusing Dextran 500. To elucidate the impact of RBC aggregation on microvascular perfusion, blood flow in the venular network of a rat cremaster muscle was analyzed with a stepwise reduction of the arterial pressure (100 → 30 mmHg). The LSCI analysis revealed a substantial decrease in the functional vascular density after the infusion of dextran. The relative decrease in flow velocity after dextran infusion was notably pronounced at low arterial pressures. Whole blood viscosity measurements implied that the reduction in venular flow with dextran infusion could be due to the elevation of medium viscosity in high shear conditions (> 45 s-1). In contrast, further augmentation to the flow reduction at low arterial pressures could be attributed to the formation of RBC aggregates (< 45 s-1). This study confirmed that RBC aggregation could play a dominant role in modulating microvascular perfusion, particularly in the venular networks.
Highlights
Microvasculature provides a large area that allows the exchange of substances between the blood stream and surrounding tissues
This study aimed to elucidate how the blood flow in venules at the network level is altered by the arterial pressure reduction and/or the aggregation induced by Dextran 500
Durussel et al [5] reported a positive relation between red blood cell (RBC) velocity and vessel diameter for venules up to 150 μm with corresponding velocities of up to 4 mm/s which was observed in this study (Fig 3B), validating the measurements of venular velocity using our laser speckle contrast imaging (LSCI) system
Summary
Microvasculature provides a large area that allows the exchange of substances between the blood stream and surrounding tissues. Impaired tissue perfusion can potentially result from abnormal alteration in the rheological properties including red blood cell (RBC) aggregation, deformability and hematocrit. Among these factors, RBC aggregation has gathered great attention [1,2,3,4,5] due to its clinical relevance to various disease conditions [6,7,8,9]. It is important to understand the relation between RBC aggregation and flow resistance in the microvascular network since the latter is inversely proportional to the perfusion
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