G-CSF-induced evacuation of sinusoidal NK cells and the facilitation of liver regeneration in a partial hepatectomy

Since liver regeneration after partial hepatectomy (PHx) is known to improve by pretreatment with recombinant human G-CSF (rhG-CSF), we investigated the mechanism by evaluating the distribution and activity of sinusoidal NK cells. F344 rats were treated with rhG-CSF (250 μg/kg/day) for 5 days before PHx. Pretreatment with rhG-CSF improved the serum ALT levels and DNA biosynthesis of the remnant liver tissues at 20 h after PHx. Notably, the rhG-CSF pretreatment decreased the number of NK cells in the liver determined by immunohistochemistry using anti-NKR-P1A mAb before and at 20 h after PHx with no significant change in the NK activity per cell base, while also increasing the number of NK cells in the peripheral blood detected by flow cytometry. The rhG-CSF induced a pre-PHx downregulation of the IL-12p70 protein levels, while also promoting the post-PHx reduction of the protein levels of IL-12p70 and IFN-γ. Conversely, rhG-CSF had no effect on the pre-PHx mRNA levels or the PHx-induced upregulation of mRNA levels of TNF-α, IL-1β, IL-6, TGF-β, IL-10, HGF, and c-Met determined by real-time RT-PCR. These results strongly suggest that rhG-CSF-induced facilitation of liver regeneration is achieved by immunoregulation through the intrahepatic IL-12 downregulation and evacuation of sinusoidal NK cells.