How Irregular Geometry and Flow Waveform Affect Pulsating Arterial Mass Transfer

Area of Science:

• Neuroscience
• Biomedical Engineering
• Fluid Dynamics

Background:

• Alzheimer's disease is a neurodegenerative disorder characterized by memory impairment.
• Protein accumulation within brain perivascular spaces (PVS) is hypothesized to cause Alzheimer's.
• PVS function as a brain waste removal system, surrounding arteries.

Purpose of the Study:

• To investigate mass transfer dynamics within PVS using computational fluid dynamics (CFD).
• To analyze protein buildup and clearance mechanisms under various flow conditions.
• To compare mass transfer in a mouse PVS model with a simplified cylindrical model.

Main Methods:

• A mouse brain PVS segment was digitized and meshed for CFD simulations.
• CFD models were validated using a cylinder with similar hydraulic resistance.
• Mass transfer was assessed under diverse advection states (no-flow, constant, sinusoidal, asymmetric periodic flow).

Main Results:

• Bulk arterial solute transport is primarily governed by advection.
• Flow pulsation and geometric irregularities (wall curvature) promote protein bolus breakup.
• Despite high Peclet numbers, local concentration reduction can be diffusion-dominated, though advection supports bolus size reduction.

Conclusions:

• Advection plays a critical role in solute transport within PVS.
• Flow dynamics, including pulsation and geometric factors, significantly influence protein clearance efficiency.
• Understanding these mechanisms could inform strategies for mitigating protein aggregation in neurodegenerative diseases.