Influence of pericyte-like vessel dilation on RBC flux in an In Vitro microvascular network.

Efficient oxygen delivery in the brain relies on a finely tuned balance between vascular architecture and dynamic flow regulation. While red blood cells (RBCs) passively flow through the capillary network, neurovascular coupling ensures that the blood supply adapts to meet the metabolic demands of active neurons. Pericytes, contractile cells embedded in the capillary walls, play a key role in this process by modulating capillary diameter in response to neural signals. While pericytes are believed to enable rapid and localized blood flow regulation, their contributions in time and space remain debated. This study investigates the effects of pericyte-like vessel dilation (i.e., pericyte relaxation) on RBC distribution and flow dynamics using an in vitro microfluidic model. We investigate how pericyte-induced dynamic cross-sectional changes affect RBC distribution and velocity in a capillary network. By employing a programmable pressure pump to simulate gradual variations in capillary diameter, we observed that short-time dilation increased RBC velocity and hematocrit near the dilation site, enhancing localized perfusion. In contrast, prolonged dilation led to a network-wide RBC redistribution minimizing hydraulic resistance, ultimately depleting hematocrit due to the network Fåhræus effect. These findings highlight the dynamic and adaptive nature of capillary blood flow, where sustained localized changes can propagate into systemic effects over time. More broadly, this study provides new insights into the interplay between localized flow regulation and systemic capillary network dynamics, revealing how geometric and dynamic factors govern RBC behavior and perfusion.