Reliable assessment of hepatic function during liver regeneration is crucial after liver surgery or liver transplantation. 99m Tcgalactosyl human serum albumin ( 99m Tc-GSA) scintigraphy, 99m Tc-mebrofenin hepatobiliary scintigraphy (HBS), the indocyanine green (ICG) clearance test, and the galactose elimination capacity (GEC) are common quantitative liver function tests. However, to our knowledge, comparative analysis between these tests has never been performed during liver regeneration. The aim of this study was therefore to compare 99m Tc-GSA scintigraphy, 99m Tc-mebrofenin HBS, the ICG clearance test, and GEC in the assessment of hepatic function during liver regeneration in rats. Methods: Rats were subjected to 70% partial hepatectomy (PHx). Liver function and functional volume were determined at predefined times after PHx and expressed as a percentage of baseline (pre-PHx) values. Results: During liver regeneration, functional liver volume measured by 99m Tc-GSA SPECT correlated strongly with conventional liver volume based on wet weight. One day after 70% PHx, conventional liver volume overestimated liver function as measured by 99m Tc-mebrofenin uptake and excretion rates, 99m Tc-GSA uptake rate, and ICG clearance. On days 5 and 7, 99m Tc-mebrofenin uptake and ICG clearance had recovered to levels similar to conventional liver volume, whereas 99m Tc-GSA uptake reflected a reduced liver function in relation to conventional liver volume and 99m Tc-mebrofenin uptake. The GEC measurements consistently overestimated liver function during regeneration. Conclusion: Volumetric assessment of the liver should be complemented by liver function-specific assays. Functional regeneration is impaired, compared with volumetric regeneration, in the early phase of liver regeneration. In later stages of liver regeneration, 99m Tc-GSA uptake underestimates hepatic regeneration in comparison to liver volume and 99m Tc-mebrofenin uptake. GEC is of less value because it is only minimally affected by 70% PHx and is influenced by factors not related to liver function. 99m Tc-mebrofenin HBS has the advantage of providing visual and quantitative information regarding both uptake and excretory liver function.

Cholestasis impairs liver regeneration following partial liver resection (PHx). Bile acid receptor farnesoid X-receptor (FXR) is a key mediator of liver regeneration. The effects of FXR agonist obeticholic acid (OCA) on liver (re)growth were therefore studied in cholestatic rats. Animals underwent sham surgery or reversible bile duct ligation (rBDL). PHx with concurrent internal biliary drainage was performed 7 days after rBDL. Animals were untreated or received OCA (10 mg/kg/day) per oral gavage from rBDL until sacrifice. After 7 days of OCA treatment, dry liver weight increased in the rBDL + OCA group, indicating OCA-mediated liver growth. Enhanced proliferation in the rBDL + OCA group prior to PHx concurred with a rise in Ki67-positive hepatocytes, elevated hepatic Ccnd1 and Cdc25b expression, and an induction of intestinal fibroblast growth factor 15 expression. Liver regrowth after PHx was initially stagnant in the rBDL + OCA group, possibly due to hepatomegaly prior to PHx. OCA increased hepatobiliary injury markers during BDL, which was accompanied by upregulation of the bile salt export pump. There were no differences in histological liver injury. In conclusion, OCA induces liver growth in cholestatic rats prior to PHx but exacerbates biliary injury during cholestasis, likely by forced pumping of bile acids into an obstructed biliary tree.

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