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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.
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Objective:To observe the peripapillary atrophy (PPA) and peripapillary choroidal vascularity index (CVI) in patients with different degrees of myopia and to analyze their correlations.Methods:A cross-sectional clinical study. From September 2021 to December 2021, 281 mypoic patients of 281 eyes treated in Eye Hospital of Wenzhou Medical University at Hangzhou were included in this study, and the right eye was used as the treated eye. There were 135 eyes in 135 males and 146 eyes in 146 females. The age was 28.18±5.78 years. The spherical equivalent refraction (SE) was -5.13±2.33 D. The patients were divided into three groups: low myopia group (group A, -3.00 D <SE≤-0.50 D), moderate myopia group (group B, -6.00 D≤SE≤-3.00 D);high myopia group (group C, SE<-6.00 D). The spherical equivalent refraction was statistically different among the three groups ( H=241.353, P<0.05). All of the affected eyes were examined by swept-source optical coherence tomography. Combined with B-scan image,assessment and area measurement of β area, γ area (β-PPA and γ-PPA) were carried out on the en-face image. After binarization of the collected images, the nasal, superior, temporal and inferior CVI of the optic disc were calculated. For comparison between groups, one-way ANOVA was used for continuous variables with normal distribution, Kruskal-Wallis test was used for continuous variables with abnormal distribution, and categorical variables were used χ2 inspection. Linear regression analysis was used for the relationship between β-PPA and γ-PPA area and peripapillary CVI of different regions. Linear regression analysis was used to evaluate the relationships between the area of peripapillary atrophy and peripapillary choroidal vascularity index in different regions. Results:There was no statistical difference in the incidence of β-PPA among the three groups ( χ2=4.672, P=0.097). The incidence of γ-PPA in group A was lower than that in group B anc C, and the difference was statistically different ( χ2=33.053, P<0.001), in which both group A was lower than group B and C. Among the three groups, the area of β-PPA and γ-PPA was statistically significant ( H=36.535, 39.503; P<0.001, 0.001); the β-PPA area of group A and B was lower than that of group C; the γ-PPA area was group A <group B <group C. Peripapillary CVI of different regions in group A, group B and group C was statistically significant ( F=11.450, 5.037, 6.018, 4.489; P<0.05). The temporal CVI in group C was lower than that in group A and B; The inferior CVI of group C was lower than that of group A, and the superior and nasal CVI of group B and C were lower than that of group A. In multivariate analysis, SE ( β=0.374, P<0.001), temporal CVI ( β=-0.299, P<0.001) were correlated with the area of β-PPA (adjusted R2=296, P<0.001); AL ( β=0.452, P<0.001), temporal CVI ( β=-0.220, P<0.001) were correlated with the area of γ-PPA (adjusted R2=0.309, P<0.001). Conclusions:The incidence and area of γ-PPA are increased in the higher degree of myopia group. The area of γ-PPA is positively correlated with the axial length, and both the area of β-PPA and γ-PPA are negatively correlated with temporal CVI.