To develop new methods for the diagnosis and treatment of such a widespread disease as steatosis, there is still a lack of fundamental biological knowledge about various aspects of the functioning of the liver tissue at the cellular level. In our work, we assessed the metabolic state of hepatocytes, as well as the collagen content in the liver tissue with induced steatosis using the modern label-free minimally invasive methods of multiphoton laser scanning microscopy with TPEF mode (Two-Photon Excited Fluorescence) and SHG mode (Second Harmonic Generation), equipped with FLIM (Fluorescence-Lifetime Imaging Microscopy). Using multiphoton microscopy, it was shown that during the development of steatosis, it is possible to identify areas with a reduced NAD(P)H autofluorescence signal in damaged hepatocytes. Using SHG we showed a gradual accumulation of collagen in the liver tissue with induced steatosis, however, extensive areas of fibrosis were not detected even at the advanced stages of the pathology. Using FLIM, we studied the specific features of the energy metabolism of hepatocytes based on data on the lifetimes of various forms of NAD(P)H and their relative contributions. It has been revealed that there is a gradual decrease in the intensity of oxidative phosphorylation, accompanied by the rise in the intensity of lipogenesis in the liver tissue with induced steatosis. Such results are consistent with the data of histological analysis. The results obtained in this work can be useful for developing new criteria for express intraoperative assessment of liver pathology at the cellular level in the clinic.
One of the promising approaches to the treatment of injured tissue is the application of bioengineering techniques based on the introduction of cells into the damage area. An application of cells alone does not provide a complete replacement of the tissue defect. Therefore, scaffolds are used allowing organization of the cells into a structure, which is capable of the total reproduction of the damaged tissue integrity. Great number of factors, which influence the cell behavior and tissue formation at the injury site when using scaffolds are known. Here, we analyzed the effect of structural heterogeneity of scaffolds on cellular behavior and metabolism. All scaffolds were obtained by two-photon polymerization technic. It was found that colonization of heterogeneous scaffolds was insignificant less than homogeneous ones. However, there were not dead cells on heterogeneous matrix. We found that the level of free and bound NAD(P)H for the cells on the heterogeneous and homogeneous scaffolds was differ. This can indicate a different contribution of glycolysis and oxidative phosphorylation intensity in stem cells seeded on two types of scaffolds.
We analyzed the structural and functional state of liver tissue in normal state and during regeneration using multiphoton microscopy in combination with the time-of-flight secondary ions mass spectrometry (TOF-SIMS). The induction of regeneration process was performed on 30% and 70% hepatectomy models of rats. The FLIM method has shown an increase in the contribution of the bound form of NADH, as well as the contribution of NADPH in hepatocytes, which indicates a growth in the contribution of oxidative phosphorylation and biosynetic processes during liver regeneration. Using the TOF-SIMS method, it has been shown that the signal from fragments of fats, fatty acids, phosphotidylcholine, and sphingomyelin is increased, combined with a decline in the signal from amino acid’s fragments in the regenerating liver. The results will make it possible to identify criteria for assessing the regenerative potential of the liver during resection in order to reduce the risk of developing of the postoperative liver failure.
Conventional techniques are insufficient to precisely describe the internal structure, heterogeneous cell populations and the dynamics of biological processes of the diseased liver during and after surgery. There is a need for a rapid and safe method for the successful diagnosis of liver disease to plan surgery, efficacy of regeneration and avoid postoperative liver failure. Here, we analyze acute and chronic liver pathology (cholestasis, cirrhosis, fatty liver disease) during progression by multiphoton microscopy with FLIM and SHG modes and chemical analysis by TOF-SIMS to obtain new data about hepatocyte pathological changes at the cellular and molecular level. All of these techniques enable to study cellular metabolism, lipid composition and collagen structure without sample staining and incorporation of fluorescent or another markers that may allow to use these methods in clinic. Complex of multiphoton microscopy and mass spectrometry provides complete information about the liver structure and function that could not be assessed using each method individually. The data can be used for both to obtain new criteria for the identification of hepatic pathology and to develop a rapid technique of liver quality analysis to plan surgery and avoid postoperative liver failure in clinic.
Conventional techniques are insufficient precisely to describe the internal structure, the heterogeneous cell populations, and the dynamics of biological processes occurring in diseased liver during surgery. There is a need for a rapid and safe method for the successful diagnosis of liver disease in order to plan surgery and to help avoid postoperative liver failure. We analyze the progression of both acute (cholestasis) and chronic (fibrosis) liver pathology using multiphoton microscopy with fluorescence lifetime imaging and second-harmonic generation modes combined with time-of-flight secondary ion mass spectrometry chemical analysis to obtain new data about pathological changes to hepatocytes at the cellular and molecular levels. All of these techniques allow the study of cellular metabolism, lipid composition, and collagen structure without staining the biological materials or the incorporation of fluorescent or other markers, enabling the use of these methods in a clinical situation. The combination of multiphoton microscopy and mass spectrometry provides more complete information about the liver structure and function than could be assessed using either method individually. The data can be used both to obtain new criteria for the identification of hepatic pathology and to develop a rapid technique for liver quality analysis in order to plan surgery and to help avoid postoperative liver failure in clinic.
Cirrhosis is defined as the histological development of regenerative nodules surrounded by fibrous bands in response to chronic liver injury that leads to portal hypertension and end stage liver disease. Conventional techniques are insufficient to precisely describe the internal structure, heterogeneous cell populations and the dynamics of biological processes of the diseased liver. Currently, multiphoton microscopy with fluorescence lifetime imaging is actively introduced to biomedical research. This technic is extremely informative and non-destructive that allows studying of a large number of processes occurring inside cells and tissues, analyzing molecular cellular composition, as well as evaluating the state of connective tissue fibers due to their ability to generate a second optical harmonic. In this study we investigated metabolic changes and collagen fibers formation in the rat liver with induced cirrhosis based on the fluorescence of the metabolic co-factors (NAD(P)H, FAD) and a second harmonic signal by multiphoton microscopy with FLIM and SHG mode. Moreover we studied ex vivo liver samples of patients with cirrhosis. We presented a separate analysis of NADH and NADPH to estimate the contribution of energy metabolism and lipogenesis in the metabolic changes. The data can be used to develop new criteria for the identification of hepatic pathology at the level of hepatocyte changes directed to personalized medicine in the future.
A cholestatic liver disease presents one of the most common liver diseases and can potentially progress to cirrhosis or even cholangiocarcinoma. Conventional techniques are insufficient to precisely describe the complex internal structure, heterogeneous cell populations and the dynamics of biological processes of the liver. Currently, the methods of multiphoton and fluorescence lifetime imaging microscopy are actively introducing to biomedical research. Those methods are extremely informative and non-destructive that allows studying of a large number of processes occurring inside cells and tissues, analyzing molecular cellular composition, as well as evaluating the state of connective tissue fibers due to their ability to generate a second optical harmonic. Multiphoton and FLIM microscopy do not need additional staining of samples or the incorporation of any markers to study metabolism, lipid composition, microstructure analysis, evaluation of fibrous structures. These parameters have pronounced changes in hepatocytes of liver with common pathological diseases. Thereby in this study we investigated metabolic changes in the healthy and cholestatic liver based on the fluorescence of the metabolic co-factors NAD(P)H and FAD by multiphoton microscopy combined with FLIM. To estimate the contribution of energy metabolism and lipogenesis in the observed changes of the metabolic profile, a separate analysis of NADH and NADPH was presented. The data can be used to develop new criteria for the identification of hepatic pathology at the level of hepatocyte changes directed to personalized medicine in the future.
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