Next Generation Experimental Models of Venous Physiology and Pathology: Examining Human Relevance in Recapitulating Lower Extremity Flow and Valve Function in New Approach Methods (NAMs).

Venous return depends on compliant vessels, competent valves, and auxiliary pumps such as the calf and thoracic muscles. Disruption of these mechanisms, through immobility, valve dysfunction, or inflammation, creates disturbed flow and heterogeneous shear that drive venous dysfunction and disease progression. Traditional animal models, though informative, fail to replicate human venous geometry and hemodynamics. This review critically evaluates current in vitro and in silico venous models, highlighting their capabilities and limitations in reproducing physiological flow, endothelial responses, and thrombus dynamics. By systematically comparing design parameters, cellular configurations, and flow regimes, we identify key gaps limiting the translational relevance of current NAMs. Building on this analysis, we propose future directions emphasizing hybrid patient-specific modeling, where imaging-derived geometries and digital twins are integrated with venous NAMs to capture individualized hemodynamics and immune-endothelial interactions. We further outline validation strategies linking NAM outputs with clinical and animal benchmarks to establish predictive fidelity. Together, these perspectives position venous NAMs as next-Generation tools to mechanistically dissect thrombosis, advance personalized risk assessment, and accelerate the development of targeted venous therapeutics.