Effect of vessel number on computational fluid dynamics in vascular networks / 中国组织工程研究

BACKGROUND:Mechanical factors can affect the angiogenic ability of vascular endothelial cells.How the vessel number affects the hydrodynamic properties of microvessels remains to be clarified. OBJECTIVE:To investigate the influence of vessel number on the hydrodynamics of vascular networks based on computational fluid dynamics. METHODS:Three three-dimensional models of vascular network with different vessel numbers were constructed using the Geometry module of ANSYS 19.0 software,and then the vascular network was meshed to tetrahedral elements in Mesh module.The vascular network was assumed to rigid wall without slip,and the blood was assumed to laminar,viscous,and incompressible Newtonian fluid.Blood density,velocity,and a series of blood viscosity coefficients were also established.The Navier-Stokes equation was used for calculation.Hydrodynamic properties of different parts of vascular network with different vessel numbers were analyzed and compared. RESULTS AND CONCLUSION:The streamline,velocity,and mass flow all had the same trend in the vascular network,that is,the outlet and inlet were higher and the middle junction of vascular network was lower.The more the number of vessels,the thinner the blood flow lines in each part of the vascular network.Also,the velocity,mass flow,and wall shear decreased with the increase of the number of blood vessels.Therefore,the changes in vessel number could influence the hydrodynamic environment in the vascular network.Computational fluid dynamics indicates that the changes in vessel numbers can influence the hydrodynamic properties of blood,and provides a new idea for treating bone hypoperfusion-induced diseases(fracture nonunion,bone defect,osteoporosis,etc.)through tonifying kidney and activating blood circulation based on the coupling between angiogenesis and osteogenesis.

Real-time conformational dynamics of SARS-CoV-2 spikes on virus particles

SARS-CoV-2 spike (S) mediates entry into cells and is critical for vaccine development against COVID-19. Structural studies have revealed distinct conformations of S, but real-time information that connects these structures, is lacking. Here we apply single-molecule Forster Resonance Energy Transfer (smFRET) imaging to observe conformational dynamics of S on virus particles. Virus-associated S dynamically samples at least four distinct conformational states. In response to hACE2, S opens sequentially into the hACE2-bound S conformation through at least one on-path intermediate. Conformational preferences of convalescent plasma and antibodies suggest mechanisms of neutralization involving either competition with hACE2 for binding to RBD or allosteric interference with conformational changes required for entry. Our findings inform on mechanisms of S recognition and conformations for immunogen design.