Name: Mouse Liver Operation and Perfusion for Studying Hepatic Metabolism
Uploaded: 2023-10-06T15:00:00
Description: Watch this Scientific Journal Video about Mouse Liver Operation and Perfusion for Studying Hepatic Metabolism at JoVE.com

mouse liver operation and perfusion for studying hepatic metabolism 

In Situ Mouse Liver Perfusion Model to Study Metabolic Responses to Substrates

The liver is an essential organ in metabolism. It plays a key role in the control of whole-body energy balance by regulating glucose, lipid, and amino acid metabolism. The increase in liver diseases worldwide is emerging as a major global health burden, and more knowledge is needed about the pathophysiology and its consequences for liver functions.
Various in vitro models have been developed for research on the liver to complement in vivo studies. Isolated and cultured primary hepatocytes from rodents and humans are widely used. Non-parenchymal cells can be separated from hepatocytes using differential and gradient centrifugation, and the co-culture of different cell types is useful for studying intercellular crosstalk1. Although primary human hepatocytes are considered the golden standard for testing drug toxicity, several studies have shown that the hepatocytes rapidly dedifferentiate in tissue culture resulting in loss of hepatic functions2,3,4. Hepatocyte culture in a 3D spheroid system ameliorates the dedifferentiation, is more stable, and appears to mimic the liver in vivo to a higher degree than the traditional 2D culture systems5. Precision-cut liver slices are another well-established in vitro model that keeps the tissue architecture intact and contains the non-parenchymal cells present in the liver6. More advanced in vitro models include liver-on-a-chip7 and liver organoids8. However, with all these approaches, there is a loss of structural integrity and flow dynamics, including vectorial portal-hepatic vein flow, which likely impacts the generalizability.
The isolated perfused rat liver was first described by Claude Bernard in 18559, and is still used in various scientific fields for studies of liver biology, toxicology, and pathophysiology. Advantages of the perfused liver compared to the above-mentioned in vitro models include the maintenance of the hepatic architecture, the vascular flow, the hepatocyte polarity and zonation, and the interactions between hepatocytes and non-parenchymal cells. Compared to in vivo studies, the perfused liver allows the study of liver metabolism in an isolated manner avoiding extra-hepatic factors carried by the blood and with complete control over the experimental conditions. Several modifications have been made to improve the rat liver perfusion model over the years10,11,12,13. Although mice have been used for isolated perfused liver studies, less literature is available. Here, we present a method for in situ perfusion of the mouse liver by cannulation of the portal vein and the suprahepatic vena cava inferior to study the acute and direct metabolic responses to metabolic substrates and hormones as measured in the hepatic venous effluent from the mouse liver in real-time.

Author Spotlight: Investigating Hepatic Adaptations and Prediabetic Progression in Liver Diseases 

Hepatic Glucose Production, Ureagenesis, and Lipolysis Quantified using the Perfused Mouse Liver Model

In our lab, we investigate how the liver responds to common, as well as rare liver diseases, and how these adaptation may predispose to a pre-diabetogenic state. The liver responds to changes in nutrient availability and concentrations of hormones with increased transcription of relevant genes, but importantly also, with acute and non-transcriptional regulation. With the perfused liver, we can quantify all aspects of metabolism, including the release of metabolites in a minute to minute resolution.Advantages of this technique compared to other in vitro models are that the liver is left in situ with an intact hepatic architecture. And that the liver is viable for at least three hours, allowing each mouse liver to be its own control. Lastly, increasing the translational relevance.Using the mouse perfused liver system, we are able to identify and characterize novel signaling cascade of the hormone glucagon. This may be important as glucagon, as well as other hormone, may play a vital role in the dysmetabolic conditions of the liver in patients with fatty liver disease and diabetes.

Watch this Scientific Journal Video about Mouse Liver Operation and Perfusion for Studying Hepatic Metabolism at JoVE.com

Mouse Liver Operation and Perfusion for Studying Hepatic Metabolism   

To begin, place the anesthetized C57 Black/6 JRj mouse. Supine on a heated operation table. Confirm the absence of reflex responses to toe pinching.Spray the mouse with 70%ethanol to prevent hair from sticking to the scissors. Using scissors, make an abdominal incision at the base, cutting upwards on both sides to the rib cage to expose the abdominal cavity. Use a cotton swab to move the intestines to the right, exposing the portal vein.Using curved forceps, place two ligatures under the portal vein and loosely tie each ligature. Next, insert a 0.7-millimeter catheter into the portal vein. When perforated, remove the needle from the catheter and guide the catheter through the vein until the tip of the catheter is close to the liver.Then, tighten the ligatures. Observe the liver. Set the flow rate from the roller pump and attach the profusion tube.Initiate the profusion of the liver at 37 degrees Celsius. Once the liver turns pale, use scissors to cut the rib cage and diaphragm. Then, using fine point forceps, place ligature under the suprahepatic inferior vena cava.Next, insert a catheter into the suprahepatic inferior vena cava through the right atrium of the heart. When perforated, remove the needle and guide the catheter through the vein closer to the liver. Then, tighten the ligature.Attach a tube for the collection of perfusion effluent and secure all tubes with waterproof tape. Using a vessel clamp adapter, place a vessel clamp across the infrahepatic vena cava immediately above the right renal vein to prevent dead mixture. Next, increase the perfusion flow rate to 3.5 milliliters per minute.Start the timer and pressure recording. Cover the liver with a sterile drape moistened with saline, equilibrate for 30 minutes, and measure the volume of effluent. After 30 minutes of equilibration, initiate the experiment for the first baseline sample collection in the fraction collector.Monitor the bubble trap regularly and refill with perfusion buffer when close to empty. Collect a buffer sample via a three-way stopcock immediately before it enters the organ and from the collecting catheter inserted in the inferior vena cava. Using a blood gas analyzer, measure the collected sample to confirm that the organ is metabolically active.After 15 minutes of baseline perfusion, using a syringe pump, start the first stimulation by infusing a test substance through a three-way stopcock at desired flow rate. After the simulation, collect baseline samples for 20 to 30 minutes before starting the second stimulation. The production of urea in the perfused liver with steady baseline periods preceding each of two stimulation periods suggested that the response of urea to two consecutive stimulations with mixed amino acids is consistent.A steady basal release of glucose and non-esterified fatty acids was observed. Before a robust increase in glucose and non-ED fatty acids during the glucagon infusion. The mean value at the basal state and during the glucagon infusion suggests that glucagon rapidly stimulates hepatic glycogenolysis and lipolysis.However, without steady basal periods, it becomes impossible to distinguish one urea response from the next.

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Research

JoVE Journal

Medicine

The liver has numerous functions, including nutrient metabolism. In contrast to other in vitro and in vivo models of liver research, the isolated perfused liver allows the study of liver biology and metabolism in the whole liver with an intact hepatic architecture, separated from the influence of extra-hepatic factors. Liver perfusions were originally developed for rats, but the method has been adapted to mice as well. Here we describe a protocol for in situ perfusion of the mouse liver. The liver is perfused antegradely through the portal vein with oxygenated Krebs-Henseleit bicarbonate buffer, and the output is collected from the suprahepatic inferior vena cava with clamping of the infrahepatic inferior vena cava to close the circuit. Using this method, the direct hepatic effects of a test compound can be evaluated with a detailed time resolution. Liver function and viability are stable for at least 3 h, allowing the inclusion of internal controls in the same experiment. The experimental possibilities using this model are numerous and may infer insight into liver physiology and liver diseases.

Here, we present a robust method for in situ perfusion of the mouse liver to study the acute and direct regulation of liver metabolism without disturbing the hepatic architecture but in the absence of extra-hepatic factors.

The liver has numerous functions, including nutrient metabolism. In contrast to other in vitro and in vivo models of liver research, the isolated perfused ...