Macrophages come on tap for liver fibrosis therapy

Infusion of Kupffer Cells Expanded in Vitro Ameliorated Liver Fibrosis in a Murine Model of Liver Injury

Transfer of exogenous macrophages represents an alternative technique to treat liver fibrosis. At present, bone marrow-derived monocytes and stem cells are the main sources for exogenous macrophages. Kupffer cells (KCs) are the resident macrophages in the liver and play a critical role in the liver homeostasis and diseases. It is unclear whether infusion of KCs can treat liver fibrosis. In this study, we observed that granulocyte-macrophage colony stimulating factor (GM-CSF) could improve the purity of cultured KCs and significantly up-regulate the expression of Cluster of Differentiation 11b (CD11b). The most important point is that GM-CSF could significantly promote the proliferation of KCs in vitro. KCs expanded in vitro still had the potential of M1/M2 polarization and phagocytosis. Furthermore, infusion of these KCs could ameliorate liver fibrosis induced by carbon tetrachloride (CCl₄) in mice. Together, our results suggest that KCs are likely to be another source for macrophage therapy.

Deletion of Protein Kinase D3 Promotes Liver Fibrosis in Mice

BACKGROUND AND AIMS

Liver fibrosis (LF) is a central pathological process that occurs in most types of chronic liver diseases. Advanced LF causes cirrhosis, hepatocellular carcinoma, and liver failure. However, the exact molecular mechanisms underlying the initiation and progression of LF remain largely unknown.

APPROACH AND RESULTS

This study was designed to investigate the role of protein kinase D3 (PKD3; gene name Prkd3) in the regulation of liver homeostasis. We generated global Prkd3 knockout (Prkd3^-/- ) mice and myeloid-cell-specific Prkd3 knockout (Prkd3^∆LysM ) mice, and we found that both Prkd3^-/- mice and Prkd3^∆LysM mice displayed spontaneous LF. PKD3 deficiency also aggravated CCl₄ -induced LF. PKD3 is highly expressed in hepatic macrophages (HMs), and PKD3 deficiency skewed macrophage polarization toward a profibrotic phenotype. Activated profibrotic macrophages produced transforming growth factor beta that, in turn, activates hepatic stellate cells to become matrix-producing myofibroblasts. Moreover, PKD3 deficiency decreased the phosphatase activity of SH2-containing protein tyrosine phosphatase-1 (a bona-fide PKD3 substrate), resulting in sustained signal transducer and activator of transcription 6 activation in macrophages. In addition, we observed that PKD3 expression in HMs was down-regulated in cirrhotic human liver tissues.

CONCLUSIONS

PKD3 deletion in mice drives LF through the profibrotic macrophage activation.