Liver homeostasis is maintained by midlobular zone 2 hepatocytes.
Liver homeostasis is maintained by midlobular zone 2 hepatocytes.
复制标题
DOI：
10.1126/science.abb1625
复制
发表时间：
2021-02-26
期刊：
影响因子：
--
通讯作者：
Zhu H
中科院分区：
文献类型：
--
作者：
Wei Y;Wang YG;Jia Y;Li L;Yoon J;Zhang S;Wang Z;Zhang Y;Zhu M;Sharma T;Lin YH;Hsieh MH;Albrecht JH;Le PT;Rosen CJ;Wang T;Zhu H
自古以来，肝脏在受伤后保持适当组织质量的显着能力就已为人所知。然而，关于有助于组织生长、维持和再生的新肝细胞的来源存在相当大的争论。多项研究报告称，肝脏中不同的细胞群作为罕见的干细胞，而其他人则提出，无论位置或功能如何，大多数肝细胞的再生活性都是相似的。虽然肝细胞在组织学上表现为同质性，但肝小叶实际上被组织成同心区域或环，其中肝细胞在血液流经的门静脉-中央静脉轴上表达不同的代谢酶。最近，单细胞分析丰富了我们对肝细胞非凡多样性的理解，但这种“区域”异质性尚未在组织稳态的背景下进行功能性探讨，因为关键的遗传标记工具尚未可用。以前的努力，以确定最再生的肝细胞没有明确解决的基本问题，再生活动是否在空间上限制在特定区域内，或是否罕见或常见的肝细胞亚群负责。这种不确定性部分是因为仅对少数肝细胞亚群进行了命运图谱分析，没有进行并行比较。我们试图通过产生一组11个新的CreER基因敲入小鼠模型来系统地解决有关新肝细胞来源的基本问题，这些小鼠模型标记了整个肝小叶的带状亚群。通过使用这些工具与三个现有的CreER线，组织的维护和再生作为功能的分区位置进行了评估。与小叶中所有肝细胞对再生的贡献相等的想法相反，我们确定了来自不同位置的肝细胞之间的主要差异。在稳态期间，门静脉附近的1区细胞的数量随着时间的推移而减少，小叶另一端中央静脉附近的3区细胞也是如此。然而，由铁调素抗微生物肽2（Hamp 2）基因标记的小叶中2区肝细胞在很大程度上负责稳态再增殖。2区细胞也受到保护，不受影响小叶两端的毒性损伤，因此在这些损伤后很好地定位于促进再生。为了确定这些谱系追踪结果的机制基础，使用单细胞和批量RNA测序转录组学来确定在区域2中特异性上调或下调的基因。然后，我们使用体内CRISPR敲除和活化筛选来鉴定调节2区增殖的功能重要途径。这些方法揭示了2区的再增殖是由胰岛素样生长因子结合蛋白2-雷帕霉素-细胞周期蛋白D1（IGFBP 2-mTOR-CCND 1）轴的机制靶点驱动的。肝小叶的不同区域在其对肝细胞周转的贡献方面表现出差异，并且2区是稳态和再生期间新肝细胞的重要来源。这些结果挑战了门静脉或中央静脉附近的干细胞具有最高的肝脏再生率的观点，但它们也支持肝细胞生物学中存在重要区域差异的原则。这项研究协调了多个小组的发现，并提供了一个更统一的肝细胞再生的观点。2区肝细胞作为再生群体的鉴定对慢性疾病发病机制、癌症发展和再生医学策略的细胞基础具有深远的影响。命运图谱菌株标记肝小叶的不同区域。来自谷氨酰胺2（Gls 2）-CreER报告小鼠的肝叶的横截面图像，其中来自不同代谢区的肝细胞被标记。面板从左到右：（i）细胞核的4′，6-二脒基-2-苯基吲哚（DAPI）染色（蓝色），（ii）邻近中央静脉的肝细胞的谷氨酰胺合成酶染色（绿色），（iii）标记1区中表达Gls 2的肝细胞的番茄荧光（红色），以及（iv）所有三个通道的合并合成图像。该报告菌株是用于追踪肝脏中代谢异质性肝细胞的14种报告菌株之一。总的来说，这些菌株用于了解不同肝细胞亚型在稳态和损伤条件下的再生能力。肝脏被组织成肝细胞表达不同代谢酶的区域。最负责肝脏再增殖和再生的细胞仍然不确定，因为仅对少数肝细胞亚群进行了命运定位。在此，使用14种小鼠命运图谱菌株系统地比较不同的肝细胞亚群。在稳态期间，门静脉周围区1和中央周围区3的细胞数量收缩，而小叶中区2的细胞数量增加。2区内的细胞，这是从普通的伤害庇护，也有助于再生后，中央和门静脉周围损伤。2区的再增殖由胰岛素样生长因子结合蛋白2-雷帕霉素-细胞周期蛋白D1（IGFBP 2-mTOR-CCND 1）轴的机制靶点驱动。因此，小叶的不同区域在其对肝细胞周转的贡献方面表现出差异，并且2区是稳态和再生期间新肝细胞的重要来源。
The liver’s remarkable capacity to maintain proper tissue mass after injury has been known since ancient times. However, there has been considerable debate about the source of new liver cells that contribute to tissue growth, maintenance, and regeneration. Multiple studies have reported that disparate cell populations in the liver serve as rare stem cells, whereas others have proposed that most hepatocytes are similar in their regenerative activity regardless of position or function. Although hepatocytes appear histologically homogeneous, the liver lobule is actually organized into concentric zones, or rings, in which hepatocytes express different metabolic enzymes across the portal vein–to–central vein axis through which blood flows. Recently, single-cell profiling has enriched our understanding of the extraordinary diversity of hepatocytes, but this “zonal” heterogeneity has not been functionally interrogated in the context of tissue homeostasis, because the critical genetic labeling tools have not been available. Previous efforts to identify the most-regenerative hepatocytes have not definitively resolved fundamental questions about whether regenerative activity is spatially restricted within particular zones or whether rare or common subsets of hepatocytes are responsible. This uncertainty was in part because fate mapping had only been performed on a few hepatocyte subsets and without side-by-side comparisons. We sought to systematically address fundamental questions about the source of new liver cells by generating a panel of 11 new CreER knock-in mouse models that label zonal subpopulations across the liver lobule. By using these tools in tandem with three existing CreER lines, tissue maintenance and regeneration as a function of zonal position were assessed. In contrast to the idea that all hepatocytes across the lobule contribute equally to regeneration, we identified major differences between hepatocytes from different locations. During steady-state homeostasis, zone 1 cells near the portal vein decreased in number over time, as did zone 3 cells near the central vein on the opposite end of the lobule. However, midlobular zone 2 hepatocytes marked by the hepcidin antimicrobial peptide 2 (Hamp2) gene were in large part responsible for homeostatic repopulation. Zone 2 cells were also shelteredfrom toxic injuries affecting either end of the lobule and thus were well positioned to contribute to regeneration after these insults. To define the mechanistic basis of these lineage-tracing results, single-cell and bulk RNA sequencing transcriptomics were used to define genes that were specifically up- or down-regulated in zone 2. We then used in vivo CRISPR knock-out and activation screening to identify functionally important pathways that regulate zone 2 proliferation. These methods revealed that zone 2 repopulation is driven by theinsulin-like growth factor binding protein 2–mechanistic target of rapamycin–cyclin D1 (IGFBP2-mTOR-CCND1) axis. Different regions of the liver lobule exhibit differences in their contributions to hepatocyte turnover, and zone 2 is an important source of new hepatocytes during homeostasis and regeneration. These results challenge the idea that stem cells near the portal or central veins have the highest rates of liver repopulation, but they also support the principle that there are important zonal differences in hepatocyte biology. This study reconciles findings from multiple groups and offers a more unified view of hepatocyte repopulation. The identification of zone 2 hepatocytes as a regenerative population has far-reaching implications for the cellular basis of chronic disease pathogenesis, cancer development, and regenerative medicine strategies. Fate-mapping strains label different zones across the liver lobule. Cross-sectional images of a liver lobe from a glutamines 2 (Gls2)–CreER reporter mouse in which hepatocytes from different metabolic zones are labeled. Panels from left to right: (i) 4′,6-diamidino-2-phenylindole (DAPI) staining (blue) of cell nuclei, (ii) glutamine synthetase staining (green) of hepatocytes adjacent to central veins, (iii) Tomato fluorescence (red) that labels Gls2-expressing hepatocytes in zone 1, and (iv) a merged composite image of all three channels. This reporter strain is one of 14 used to track metabolically heterogeneous hepatocytes in the liver. Collectively, these strains were used to understand the regenerative capacity of different liver cell subtypes under homeostatic and injury conditions. The liver is organized into zones in which hepatocytes express different metabolic enzymes. The cells most responsible for liver repopulation and regeneration remain undefined, because fate mapping has only been performed on a few hepatocyte subsets. Here, 14 murine fate-mapping strains were used to systematically compare distinct subsets of hepatocytes. During homeostasis, cells from both periportal zone 1 and pericentral zone 3 contracted in number, whereas cells from midlobular zone 2 expanded in number. Cells within zone 2, which are sheltered from common injuries, also contributed to regeneration after pericentral and periportal injuries. Repopulation from zone 2 was driven by the insulin-like growth factor binding protein 2–mechanistic target of rapamycin–cyclin D1 (IGFBP2-mTOR-CCND1) axis. Therefore, different regions of the lobule exhibit differences in their contribution to hepatocyte turnover, and zone 2 is an important source of new hepatocytes during homeostasis and regeneration.
登录
查看更多内容
影响因子：
64.8
作者：
Halpern KB;Shenhav R;Matcovitch-Natan O;Toth B;Lemze D;Golan M;Massasa EE;Baydatch S;Landen S;Moor AE;Brandis A;Giladi A;Avihail AS;David E;Amit I;Itzkovitz S
通讯作者：
Itzkovitz S
影响因子：
16.6
作者：
MacParland SA;Liu JC;Ma XZ;Innes BT;Bartczak AM;Gage BK;Manuel J;Khuu N;Echeverri J;Linares I;Gupta R;Cheng ML;Liu LY;Camat D;Chung SW;Seliga RK;Shao Z;Lee E;Ogawa S;Ogawa M;Wilson MD;Fish JE;Selzner M;Ghanekar A;Grant D;Greig P;Sapisochin G;Selzner N;Winegarden N;Adeyi O;Keller G;Bader GD;McGilvray ID
通讯作者：
McGilvray ID
影响因子：
1.5
作者：
Means, Anna L.;Xu, Yanwen;Gu, Guoqiang
通讯作者：
Gu, Guoqiang
DOI：
10.1007/978-1-59745-019-5_13
发表时间：
2010-01-01
期刊：
MOUSE CELL CULTURE: METHODS AND PROTOCOLS
影响因子：
--
作者：
Li, Wan-Chun;Ralphs, Kate L.;Tosh, David
通讯作者：
Tosh, David
影响因子：
6
作者：
Fickert, Peter;Stoeger, Ulrike;Trauner, Michael
通讯作者：
Trauner, Michael