78&#37; liver resection technique for hepatic regeneration assessment

Mouse Extended Hepatectomy Model for Liver Regeneration Studies

Mouse and rat surgical liver resection models, first described in 1931, are the most common experimental models utilized to study the molecular basis of liver regeneration. They could also be useful in translational science research to test and develop strategies to improve outcomes following extended liver resection or transplantation of suboptimal liver grafts1,2,3,4. Partial hepatectomies (PH) in mice entail the removal of approximately 2/3 (66%) of the total liver mass (TLM), which when performed in healthy animals have exceptional outcomes5. The procedure is short in duration, easily reproducible due to little variation in mouse liver anatomy, and postoperative survival typically nears 100%1.
Partial 2/3 hepatectomy encompassing the resection of the left lobe (LL) and median lobe (ML) allows for the residual lobes to regenerate relatively unimpeded by lobar inflammation or restriction of hepatic inflow and outflow. Rather, increased portal venous flow and subsequently shear stress on liver sinusoidal endothelial cells following PH result in sustained upregulation of endothelial nitric oxide synthase (eNOS) expression and subsequent nitric oxide (NO) release, which contribute to the priming of hepatocytes for proliferation and liver regeneration3. Outcomes commonly studied after 2/3 PH in disease models such as non-alcoholic fatty liver disease or in specific genetic backgrounds include risk of acute liver failure, qualitative and quantitative measures of the liver regenerative capacity, and other biologic responses to stress or traumatic injury1,3.
However, a mouse model mimicking functional or anatomical small-for-size syndrome, as it occurs following extended liver resection for cancer or transplantation of marginal (steatosis or prolonged ischemic time) or partial (split or from living donor liver) liver grafts, remains to be well-established. To address this need, models of more extensive liver resections that extend beyond the maintenance of a minimal (and functional) liver mass are required to model small-for-size liver syndrome and the heightened mortality that is associated with this syndrome6,7.
Mouse liver anatomy exhibits minimal variation. The mouse liver is comprised of five lobes, each accounting for the following percentage of the total liver mass: left lobe (LL; 34.4 &#177; 1.9%), median lobe (ML; 26.2 &#177; 1.9%), right upper (also called right superior) lobe (RUL; 16.6 &#177; 1.4%), right lower (also called right inferior) lobe (RLL; 14.7 &#177; 1.4%), and caudate lobe (CL, 8.1 &#177; 1.0%)1,5. Each lobe is supplied by a portal triad, including a branch of the hepatic artery, a branch of the portal vein, and a bile duct5. Historically, several techniques were described to perform a 2/3 PH by resecting the LL and the ML. These include 1) the classical technique that consists of a single ligature en bloc at the base of each of the resected lobes; 2) the hemostatic clip technique, using titanium clips applied at the base of the resected lobes; 3) a vessel-oriented parenchyma-preserving technique, using piercing sutures proximal to the clamp; and 4) a vessel-oriented microsurgical technique, whereby the portal vein and hepatic artery branches are ligated prior to lobe resection1. While each technique has relative strengths and weaknesses, none yields higher lethality1,8,9.
In this study, we present a novel method for extended 78% PH in mice. In this model, three of five liver lobes, including the LL, ML, and RUL, are removed separately using a ligature technique (Figure 1). This procedure results in the resection of approximately 78% (77.2 &#177; 5.2%) of the total liver mass. Our choice of removing the LL and ML separately, and not &#34;en bloc&#34; as in the classical PH technique, minimizes complications that are associated with en bloc resection of these two lobes, such as suprahepatic vena cava stenosis and heightened risk of necrosis of the remaining lobes when the single ligature is applied too close to the vena cava1,10,11,12,13,14. This is crucial before moving to the final step of this procedure to remove the RUL. This extensive hepatectomy in 8-12 weeks old, wild-type C57BL/6 mice causes 50% lethality within 1 week of surgery due to failed liver regeneration causing fulminant liver failure15,16. This mouse model of heightened lethality following extended 78% hepatectomy appropriately recapitulates the pathophysiology of small-for-size syndrome and enables the development and testing of novel strategies to improve outcomes.

Author Spotlight: Evaluating Therapeutic Strategies to Enhance Liver Regeneration

Extended 78&#37; Hepatectomy in a Mouse Surgical Model

The scope of our research is to evaluate therapeutic strategies to enhance liver regeneration and repair that could aid in improving patients'outcomes in the setting of liver transplantation using marginal liver graft, as well as extended liver resection for cancer that are at higher risk for primary non-function and acute hepatic failure. Our team utilizes genomic, proteomic, and metabolomic platforms to study liver regeneration and identify novel therapeutic targets to improve outcomes. The focus of our laboratories is to develop state-of-the-art gene therapy platforms to deliver the hepatoprotective and liver regenerative gene A20.We uncovered a potent hepatoprotective function for A20, also called TNFAIP3, through its combined anti-inflammatory, anti-apoptotic, and proliferative functions in hepatocytes. Liver targeted A20 gene therapies protected from lethality in mouse models of toxic hepatitis, extended 78%and lethal radical hepatectomies 90%and also prolonged liver ischemia. Recent promising pre-translational studies in large animal prelude clinical translation of this therapy.This protocol offers a unique surgical model designed for investigating small for size syndrome, as well as assessing therapeutic strategies to improve outcomes of extensive hepatectomies for cancer, and increase successful rates of marginal and extended criteria liver grafts. When the 78%hepatectomy is performed correctly, this procedure results in approximately 50%postoperative survival as opposed to nearly 100%survival associated with the classical 2/3 partial hepatectomy in healthy mice.

78&#37; Liver Resection Technique for Hepatic Regeneration Assessment

Research

JoVE Journal

Biology

Partial 2/3 hepatectomy in mice is used in research to study the liver's regenerative capacity and explore outcomes of liver resection in a number of ...