Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham , Birmingham, Alabama.
Am J Physiol Gastrointest Liver Physiol. 2018 Jun 1;314(6):G677-G689. doi: 10.1152/ajpgi.00381.2017. Epub 2018 Mar 15.
Hepatorenal fibrocystic disease (HRFCD) is characterized by cysts in the kidney and liver with associated fibrosis and is the result of defects in proteins required for cilia function or assembly. Previous reports indicate that macrophages, mainly M2-like macrophages, contribute to HRFCD, although the origin of these cells (yolk sac-derived resident macrophages vs. bone marrow-derived infiltrating macrophages) and their contribution to the observed phenotypes are unknown. We utilize a congenital model of cilia dysfunction (IFT88) to study the importance of macrophages in HRFCD. Our data show a rapid expansion of the bile duct region and development of fibrosis between 2 and 4 wk of age. Immunofluorescence microscopy analysis reveals an accumulation of F4/80 macrophages in regions exhibiting biliary hyperplasia in IFT88 mice. Flow cytometry data show that cilia dysfunction leads to an accumulation of infiltrating macrophages (CD11b, F4/80) and a reduction of resident macrophage (CD11b, F4/80) number. A majority of the infiltrating macrophages are Ly6c profibrogenic macrophages. Along with the accumulation of immune cells, expression of proinflammatory and profibrotic transcripts, including TGF-β, TNF-α, IL-1β, and chemokine (C-C) motif ligand 2, is increased. Quantitative RT-PCR analysis of flow-sorted cells shows enhanced expression of CCL2 in cholangiocytes and enhanced expression of VEGF-A and IL-6 in Ly6c macrophages. Genetic inhibition of Ly6c macrophage accumulation in IFT88 FVB CCR2 mice reduced biliary fibrosis but did not affect epithelial expansion. Collectively, these studies suggest that biliary epithelium with defects in primary cilia preferentially recruits Ly6c infiltrating macrophages, which promote fibrotic progression in HRFCD pathogenesis. NEW & NOTEWORTHY These studies are the first to address the contribution of the infiltrating and resident macrophage niche during progression of hepatorenal fibrocystic disease (HRFCD). We show that the number of infiltrating macrophages is significantly upregulated in HRFCD mouse models. Finally, we show that prevention of Ly6c infiltrating macrophage accumulation significantly reduces biliary fibrosis, but not biliary hyperplasia, suggesting that this population may be responsible for the fibrotic progression of the disease in HRFCD patients.
肝-肾纤维囊性疾病（HRFCD）的特征是肾脏和肝脏中有囊肿，伴有相关纤维化，这是纤毛功能所需蛋白缺陷的结果。先前的报告表明，巨噬细胞（主要是 M2 样巨噬细胞）有助于 HRFCD，尽管这些细胞的来源（卵黄囊衍生的常驻巨噬细胞与骨髓衍生的浸润巨噬细胞）及其对观察到的表型的贡献尚不清楚。我们利用纤毛功能障碍的先天性模型（IFT88）来研究巨噬细胞在 HRFCD 中的重要性。我们的数据显示，在 2 至 4 周龄时，胆管区域迅速扩张，并出现纤维化。免疫荧光显微镜分析显示，在 IFT88 小鼠的胆汁增生区域，F4/80 巨噬细胞积聚。流式细胞术数据显示，纤毛功能障碍导致浸润巨噬细胞（CD11b、F4/80）的积累和常驻巨噬细胞（CD11b、F4/80）数量的减少。大多数浸润巨噬细胞是 Ly6c 致纤维化巨噬细胞。随着免疫细胞的积累，包括 TGF-β、TNF-α、IL-1β 和趋化因子（C-C）基序配体 2 在内的促炎和致纤维化转录本的表达增加。对经流式细胞术分选的细胞进行定量 RT-PCR 分析显示，在胆管细胞中 CCL2 的表达增强，在 Ly6c 巨噬细胞中 VEGF-A 和 IL-6 的表达增强。在 IFT88 FVB CCR2 小鼠中遗传抑制 Ly6c 巨噬细胞的积累减少了胆管纤维化，但不影响上皮细胞的扩张。总的来说，这些研究表明，具有初级纤毛缺陷的胆管上皮细胞优先募集 Ly6c 浸润巨噬细胞，促进 HRFCD 发病机制中的纤维化进展。新观点和值得注意之处：这些研究首次探讨了在肝-肾纤维囊性疾病（HRFCD）进展过程中浸润性和常驻巨噬细胞龛的贡献。我们显示 HRFCD 小鼠模型中浸润性巨噬细胞的数量显著上调。最后，我们表明预防 Ly6c 浸润性巨噬细胞的积累可显著减少胆管纤维化，但不减少胆管增生，这表明该群体可能负责 HRFCD 患者疾病的纤维化进展。
