To test whether DCs may contribute to HSC activation and liver fibrogenesis, we first performed selleck a coculture of DCs and HSCs. Similar to HMs, DCs did not activate HSCs but rather up-regulated the expression of NF-κB–dependent genes, and NF-κB–driven luciferase reporter activity through an IL-1– and TNF-dependent manner (Fig. 6B). However, activation of NF-κB was considerably lower than the induction we observed in HM coculture. Based on these

results, we next determined whether DC ablation may have contributed to the reduced fibrogenesis in clodronate-treated mice. In our first approach, we performed BDL in diphtheria toxin-treated or PBS-treated bone marrow–chimeric CD11c-DTR-eGFP mice. Bone marrow chimerism avoids the known side effects of diphtheria toxin treatment observed after long-term Cell Cycle inhibitor treatment in global CD11c-DTR-eGFP mice.[26] We did not observe a significant difference in BDL-induced fibrosis as determined by sirius red staining and qRT-PCR

for the fibrogenic genes α-SMA, Col1a1, and TIMP1 (Fig. 6C-D). We confirmed these data employing CCl4 injection for induction of liver fibrosis, again using bone marrow-chimeric CD11c-DTR-eGFP mice. Similar to the BDL model, we did not observe significant differences in liver fibrosis between PBS and diphtheria toxin-treated mice (Fig. 6E). As a third approach, we used antibody-mediated ablation of pDC. Again, we did not observe a reduction of CCl4-induced liver fibrosis (Fig. 6F). Importantly, we achieved considerable oxyclozanide depletion of cDC and pDC using the above methods (Supporting Fig. 8). Similar to previous studies,[27] we observed neutrophilia in CD11c-DTR mice (Supporting Fig. 9) but consider this unlikely to exert a profound effect on fibrosis based on previous studies.[28] Thus, our data suggest that neither class of DC significantly contributes to liver fibrogenesis in vivo. Hepatic fibrogenesis involves multiple resident and recruited cell populations. HSCs represent the center component of this wound healing response, but

other populations, including macrophages, are known positive modulators of fibrogenesis. Here, we uncover a novel function of macrophages, the promotion of HSC/myofibroblast survival. A second novel finding of our study lies in the discovery that DCs do not contribute to liver fibrosis. Employing microarray and pathway analysis, we discovered that NF-κB, the best-characterized antiapoptotic signaling pathway[29, 30] and an important regulator of liver injury and fibrosis,[31] was a key pathway activated in HSCs by HMs. The relevance and physiologic nature of the employed in vitro coculture system is validated by the finding that this system achieves HSC gene expression patterns highly similar to those found in in vivo–activated HSCs, and that all gene expression changes and functional consequences of NF-κB activation were confirmed in vivo.