Mechanism of liver regeneration after liver resection and portal vein embolization (ligation) is different?

Whether or not liver regeneration after portal branch embolization (PE) (ligation, PVL) in the non-embolized (ligated) lobe is by the same mechanism as regeneration in the remnant lobe after liver resection has been reviewed. Portal vein branch embolization and heat shock protein are then discussed. Tumor growth accelerated in the remnant liver after hepatectomy. In contrast, PE or PVL resulted in marked contralateral hepatic hypertrophy and significant reduction of tumor growth in the non-embolized (non-ligated) lobes. Follistatin administration significantly increased liver regeneration after hepatectomy in rats. In contrast, regeneration of non-ligated lobes after PVL was not accelerated by exogenous follistatin. Tumor growth also was not accelerated. The liver regeneration rate peaked at 48-72 h in the nonligated lobe after PVL, a delay of 24 h compared with the remnant liver after hepatectomy. In the postoperative early stage, the expression of activin betaA, betaC, and betaE mRNAs was stronger in PVL than in hepatectomy. At 72 h the expression of activin receptor type IIA mRNA reached a peak in hepatectomy, but was significantly lower in PVL. Thus, regulation of activin signaling through receptors is one of the factors determining liver regeneration after hepatectomy and PVL. These serial experimental results imply that the mechanism of liver regeneration after portal branch ligation (embolization) is different from that after hepatectomy. Heat shock protein was induced in the liver experimentally by intermittent ischemic preconditioning and could play some beneficial role in the recovery of liver function after hepatectomy, even in cirrhotic patients. When heat shock protein following right portal vein embolization in both the embolized and non-embolized hepatic lobes was investigated in clinical cases, a two to fourfold increase in HSP70 was induced in the non-embolized lobe compared with the embolized lobe. Oral administration of geranylgeranylacetone (a non-toxic HSP inducer) suppressed inflammatory responses and improved survival after 95% hepatectomy by induction of HSP70 in rats.