Simulation Of Tumor Vascular Structure Based On Microfluidic Chips And Its Application On Vasculogenic Mimicry Research

The research of blood vessel and hemodynamics in tumor is an important content in the hemorheology.Usually,the growth and development of tumors are accompanied by angiogenesis and vasculogenic mimicry.However,the vascular structure of the tumor is different from that of normal blood vessels,which leads to abnormal blood flow and tumor microenvironment.It is important to study the effects of tumor vasculature and blood flow on tumor growth,invasion and metastasis.However,the mechanism of characteristic structure of tumor vascular,such as multiple bifurcation,bending,narrow diameter and damaged tube,affects the flow behavior and growth behavior of blood and tumor cells in it is not clear.Moreover,the mechanism of the response of tumor cells to mechanical factors is not clear.In clinic,imaging technology is usually used to detect tumor vascular structure and blood flow,but no cell exploration is carried out.Lately,the use of microfluidic technology and commercial software for computational fluid dynamics to construct tumor vasculature experimental models and tumor vascular remodeling are the main methods for studying tumor vascularity and hemodynamics.Therefore,it is a simple way to explore the mechanism of tumor vascular structure and tumor cell interaction by constructing a model that can simulate the actual tumor blood vessels and blood flow in vitro and study the effect of tumor blood vessel characteristics on blood flow and cells.Based on the previous research results of the research group,this paper designed and fabricated a blood vessel network structural model based on microfluidic technology with the characteristics of tumor blood vessels,and established an experimental platform that can simulate blood flow in vivo.The effects of tumor vascular characteristics on the flow field and the movement and growth behavior of HepG2 cells were investigated.Then,the computational fluid dynamics commercial software was used to simulate and calculate the tumor vascular network structure and its fluid flow.The effects of flow velocity,pressure,vorticity,and shear stress on the flow field and cells were quantitatively analyzed.In addition,microfluidic chips and prepared micro-porous matrix matrigel materials were used to simulate the flow of tissue microdistributions in solid tumors.The effects of tissue micro-porous flow on the spreading,sprouting and formation of angiogenic mimicry of HepG2 cells in three-dimensional environment were investigated.The results of this study haveimportant implications and value in the understanding of the interaction between hemorheological properties and vascular structures,blood flow,and tumor cells in solid tumors.The main contents and results of present study are as follows:(1)Three types of microfluidic chips with different microposts were fabricated using the SU-8,vacuum-bonded and heat-pressing packaging method.Using the fabricated microfluidic chips and Matrigell,tumor vascular models with bifurcation,bending,stenosis,and vessel damage were established.By constructing a sustainable and stable flow perfusion experimental platform,various types of blood flow within the tumor blood vessels are approximately simulated.The constructed microfluidic experimental platform can be used for the simulation of blood flow in tumor blood vessels and the study of cells in it flow behavior.The fabrication of the microfluidic chip and the construction of the experimental platform are very simple.The peripheral liquid flow control devices are inexpensive.The experimental conditions are well controllable,easy to operate and to repeat.(2)Cell suspensions composed of HepG2 cells and DMEM was used to simulate blood containing tumor cells in tumor blood vessels.By means of cell tracing,the trajectory of cells flowing through different tumor vascular structures is observed under a microscope.The flows of tumor vasculature were then simulated and calculated using the Gambit and Fluent software.Through experimental simulation and software simulation,the effects of various morphological characteristics of tumor blood vessels on blood flow and flow behavior of HepG2 cells were investigated and evaluated.The single factors such as the bifurcation angle of tumor vessels,the number of bifurcations,the diameter of the channel,and the concave-convex structure formed by the damage vessel have significant effects on the flow behavior of HepG2 cells.The effects of strong vortex flow and tangential flow on the flow field and the flow behavior of HepG2 cells are more prominent.But,when the influencing factors caused by multiple vascular structures are superimposed,the effect of a single factor will be reduced.(3)Within the constructed tumor vasculature,an experimental model was designed in which HepG2 cells adhered to two different substrates suffer from shear stress formed by blood flow in vitro.The flow field was simulated and calculated by using the Gambit and Fluent software.The effects of fluid shear stress on the spreading and formation of vasculogenic mimicry of adherent HepG2 cells in a tumor vascular structural model were investigated and evaluated in two flow types: two-bifurcationflows and non-bifurcation flows.In the shear force range below the physiological conditions of blood circulation,relatively high shear stress can promote the formation of lumen-like structures in HepG2 cells.However,the shear stress within the physiological conditions of blood circulation can only promote the spreading of HepG2 cells in a short time,but it can not promote the formation of vascular-like structures in HepG2 cells.(4)A tissue micro-porous flow model of tumor was established based on a microfluidic chip.The effects of tissue micro-porous on the spreading,budding and vasculogenic mimicry of HepG2 cells was investigated by two-dimensional and three-dimensional dynamic and static experiments in vitro.Also,the response of HepG2 cells to tissue micro-porous flow formed by Matrigel with different hardness was evaluated.The results indicate that the hardness of the Matrigel or the protein content in the Matrigel does not form a linear inverse relationship with the ability of HepG2 cells to vasculogenic mimicry.The hardness of the Matrigel is only an important factor in the formation of lumen-like structures of HepG2 cells.Matrigel gel formed in the ratio range of 1:2 to 1:3 between Matrigel and DMEM was significant in promoting vasculogenic mimicry of HepG2 cells.In addition,the force and direction of the tissue micro-porous flow between the matrigel gaps have a significant effect on the vasculogenic mimicry of HepG2 cells,and the influence of the shear stress is related to the force and direction of the micro-porous flow.In summary: Around that the interaction mechanism between tumor vascular structure and blood flow and HepG2 cell behavior,tumor vascular structural model and blood flow model were designed and manufactured based on microfluidic technique.This approach is combined with biological experiments in vitro and simulations and calculations using commercial computational fluid dynamics software,the quantitative analysis of the effects of bifurcation angle,number of bifurcations,narrow diameter,damaged vessel wall,and micro porous flow of tumor vessels on the retention,adhesion,spreading,sprouting,and angiogenesis mimicry of HepG2 cells by the it.The design of this article provides a new way of thought and an effective way to study tumor vascular and hemorheological properties in vitro.The preliminary conclusions have certain reference implications and value in the understanding of the interaction between malignant tumor metastasis and tumor vascular structures in solid tumors.