Selective portal vein embolization and ligation trigger different regenerative responses in the rat liver.

UNLABELLED: Two strategies are clinically available to induce selective hypertrophy of the liver: portal vein embolization (PVE) and portal vein ligation (PVL). The aim of this study was to compare the impact of PVE and PVL on liver regeneration. Rats were subjected to 70% PVL, 70% PVE, 70% partial hepatectomy (PH) (positive control), or sham operation (negative control). PVL and PVE of liver segments were validated by portography and histology, demonstrating obstruction of the involved portal branches. Liver weight and markers of regeneration were assessed at 24, 48, and 72 hours, and 7 days after surgery (n = 5). Sinusoidal perfusion was examined by intravital microscopy. The weight of the regenerating liver segments increased continuously in all groups, with the highest weight gain after PH, which also disclosed the strongest proliferative activity. In Ki-67 and PCNA stainings, hepatocyte proliferation after PVL was more pronounced than after PVE (P = 0.01). Volumetric blood flow and functional sinusoidal density were lower after PVE than after PVL (P = 0.006, P = 0.02, respectively). The accumulation of Kupffer cells 24 hours after the intervention was highest after PH. Transcript levels of cytokines (interleukin-1beta, tumor necrosis factor-alpha, interleukin-6) peaked at 24 hours and were highest after PH. The embolized part of the liver after PVE showed prominent foreign body reaction in the portal triad with accumulation of macrophages.
CONCLUSION: PVL is superior to PVE in inducing a regenerative response of the remnant liver. The impairment of liver regeneration after PVE may be a consequence of macrophage trapping in the occluded segment due to a foreign body reaction. Lower blood flow and lower accumulation of macrophages, particularly Kupffer cells, in the regenerating part of the liver likewise causes impaired liver regeneration after PVE.