Study On The Interstitial Fluid Flowing Along The Venous And Arterial Adventitia And Paravascular Connective Tissue In Mice

Objective The interstitial fluid flowing along the venous and arterial adventitia and paravascular connective tissue of mice were observed in animal experiments and which law was quantitatively described.Materials and Methods(1)The fluorescent sodium solution(FluoNa)or 10 nm CdSe/ZnS was injected into the distal venous and arterial adventitia and paravasculer connective tissues of the lower limbs in BALB /c mice and SD rats.Use a stereoscopic fluorescence microscope to observe and record the dynamic flow data of the interstitial fluid along the vessel walls at the level of the femoral arteriovenous sheath.(2)Using histological analysis methods,and combining with the two-photon laser confocal microscope detecting the vascular tissue specimens obtained from the experimental mice immediately after injecting the FluoNa,to clarify the spatial location and histological structure of the pathways of the interstitial fluid flowing along the venous and arterial adventitia and paravasculer connective tissues.(3)Use the computer to gray-scale the image data collected by the stereo fluorescence microscope,and record the changes in the fluorescence intensity value of the target area of the adventitia of the blood vessels.(4)Use the computer to trace the movement trajectory and the flow velocity field distribution of the FluoNa particle cluster along the adventitia of the venous blood vessels,and finally generate a line graph of the velocity range.(5)Using Spectral CT for in Vivo and ex Vivo Microscopy scan to trace the interstitial fluid flowing pathways along the adventitial with injecting iohexol solution(6)Describe the "backflow" phenomenon of the interstitial fluid when the mice are dying,"Emerging flow" phenomenon in damaged adventitia and the special connection of the adventitia between the branch vein and the main vein shown in FluoNa fluorescence tracer imaging.Summarize and analyze the law of the interstitial fluid flowing along the venous and arterial adventitia and paravascular connective tissue in miceResults By tracking the continuous flow of the interstitial fluid along the venous and arterial adventitia and paravascular connective tissue with injecting FluoNa,we found that:(1)FluoNa from the paravascular connective tissue of the distal veins in the lower limbs flows continuously along the venous adventitia and paravascular connective tissue.(2)FluoNa from paravascular connective tissue of the distal arteries in the lower limbs flows continuously along the arterial adventitia and paravascular connective tissue.(3)FluoNa from paravascular connective tissue of the distal accompanying arteries and veins in the lower limbs flows continuously along the interstitial space between femoral arteriovenous blood vessels.(4)The tissues stained by FluoNa are the adventitia of arteries and veins and the paravascular connective tissue.(5)When a large amount of FluoNa is administered,FluoNa flows along the adventitia of the vein and artery and the interstitial space between them,and at the same time diffuses into the fibrous connective tissue around the adventitia of the blood vessels.(6)The interstitial fluid flowing pathways traced by iohexol solution using Spectral CT for in Vivo and ex Vivo Microscopy is a non-smooth,discontinuous curve.(7)When the experimental mice were dying,the flow velocity of the interstitial fluid along the adventitia of venous vessels ranges from 0.5 um/s to 3.5 um/s.(8)When the experimental mice were dying,"backflow" of the interstitial fluid first appeared along the adventitia of the main venous vessels,and then appeared along the adventitia of branch vessels.(9)When the damaged adventitia forms a "cross-section",the interstitial fluid appears "emerging flow" along the cross-section,indicating that the interstitial fluid flowing along the adventitia is a "non-lumen" flow.(10)The FluoNa tracer imaging shows that the adventitia of the main vein and branch veins are connected in a special way: the adventitia of the branch blood vessels is not directly connected to the main vein at the bifurcation,but at the upper end of the main vein walking for a certain distance,then it gradually merging into the adventitia of the main vein.Conclusions The interstitial fluid flowing along the adventitia of arteries and veins is a "non-lumen" long-range flow.The histological structure of this flowing is fibrous connective tissue.It breaks the traditional physiology’s view that the interstitial fluid is "constrained by extracellular gel and cannot flow".The interstitial fluid is not only flows along the adventitia of the vein and its paravascular connective tissue,but also flows along the adventitia of the artery and its paravascular connective tissue.The interstitial fluid flow along the adventitia and paravascular connective tissue of the veins and arteries in the lower extremities were observed in this study is likely to be a part of the interstitial fluid flowing system along the adventitia of the vascular tree.As observed by the FluoNa tracing method,the flowing along the adventitia and paravascular connective tissue can be divided into two parts: transmission and diffusion.The flow direction of the interstitial fluid is the same direction as the venous blood flow and opposite to the arterial blood flow.This series of phenomena brings new perspectives and ideas to the study of vascular physiology.