Geometry-Encoded Microtrenches Stabilize Endothelium on High Shear Biomaterial Surfaces

Maintaining a confluent, antithrombotic endothelium on cardiovascular biomaterial surfaces remains a major barrier to long-term hemocompatibility, as endothelial cells (ECs) rapidly denude under supraphysiological shear in prosthetic devices. Here, we hypothesized that mesoscale surface geometry (∼100-200µm) could reorganize near-wall hemodynamics, preserving endothelial coverage and function under extreme shear. Engineered microtrenches were introduced onto an implant biomaterial to generate spatially defined shear environments. Under supraphysiological near-wall shear (∼250dyn/cm²), microtrenched geometries created attenuated shear and vorticity gradients. Endothelial monolayers were sustained in these flow domains for 120 hours, whereas flat controls rapidly denuded. Endothelial retention in 22.5° angled trenches increased dramatically, from an EC₅₀ of 41 to 90 dyn/cm². 45° angled trenches further increased endothelial shear resistance to an EC₅₀ of 205dyn/cm². Endothelial monolayers demonstrated collective mechano-adaptation to ultra-high shear through VE-cadherin junction thickening and coordinated cytoskeletal and nuclear alignment. Mechanoadapted monolayers exhibited increased eNOS expression correlated with local shear and elevated nitrite production (45°: 50.4 ± 6.1µM; 22.5°: 35.7 ± 3.3µM; 0°: 28.4 ± 6.8µM). In contrast, interfaces with abrupt shear transitions or elevated rotational flow exhibited reduced coverage, junctional thinning, and re-emergence of VCAM-1 and PAI-1, indicating inflammatory and pro-thrombotic activation. Structural, functional, and inflammatory readouts exhibited peak responses within a shared shear-vorticity regime. Multivariate regression identified shear-vorticity coupling as the dominant predictor of endothelial persistence, with optima clustering within a mechanical range (≈0.8-2.9 × 10⁶dyn·cm⁻²·s⁻¹). These findings establish geometry-driven modulation of near-wall flow as a predictive design strategy for endothelialization and vasoprotection of high-shear cardiovascular implants. STATEMENT OF SIGNIFICANCE: Blood-contacting cardiovascular implants remain prone to thrombosis because the protective endothelial cell layer cannot be maintained under extreme flow conditions, necessitating lifelong anticoagulation. Existing approaches rely on coatings or drug delivery but do not address the flow conditions that drive endothelial loss. Here, we demonstrate that mesoscale surface geometry alone can reorganize near-wall flow to stabilize and functionally preserve endothelial layers under high shear. By combining simulations and experiments, we identify flow conditions, specifically the balance of shear and rotation, that predict cell retention, nitric oxide production, and reduced inflammatory signaling. This work establishes a geometry-driven, coating-independent design principle for hemocompatible biomaterials, providing a scalable and durable strategy for engineering cardiovascular implants.