McDaniel C Griffin, Fox Dermot, Pastura Patricia, Alharbi Sara, Huppert Stacey S, Cras Timothy D Le
Division of Pulmonary Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
Division of Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, Cincinnati Children's Hospital Medical Center and University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
Pediatr Blood Cancer. 2025 Mar;72(3):e31492. doi: 10.1002/pbc.31492. Epub 2024 Dec 26.
Kaposiform lymphangiomatosis (KLA) is a complex lymphatic anomaly associated with a somatic activating NRAS p.Q61R (NRAS) mutation. KLA is characterized by malformed lymphatic vessels that can lead to effusions and coagulopathy. The goal of this study was to generate an in vivo mouse model to determine if prenatal expression of the Nras mutation in lymphatic endothelial cells induces disease characteristics found in KLA patients.
A Cre-loxP system was used to conditionally express Nras in cells expressing lymphatic vessel endothelial hyaluronan receptor 1 (Lyve1), a marker of lymphatic and other types of endothelial cells that starts being expressed at embryonic day (E) 7.5. Because pups did not survive birth, embryos were collected at E14.5, E15.5, and E18.5 for gross analysis, histology and immunostaining, and organ whole-mounts.
Staining for NRAS demonstrated robust recombination in the Nras mutant embryos and localization of Nras at sites of vascular abnormalities. Nras mutant embryos had significant edema and dysmorphic jugular lymph sacs with abnormal Lyve1-positive cellular masses. The lymphatic vessel network in the back skin of the Nras mutant embryos had fewer branch points and increased vessel diameter. Nras mutant embryos had severe hepatic defects characterized by disordered and enlarged vessels. By E18.5, Nras mutant embryos were dead.
Conditional expression of Nras in Lyve1-positive cells caused edema, abnormal lymphatic development, and hepatic vascular defects in mouse embryos. These findings further support the role of NRAS as a driver of the lymphatic overgrowth, vessel enlargement, and dysfunction in the pathophysiology of KLA.
卡波西样淋巴管瘤病（KLA）是一种复杂的淋巴管异常疾病，与体细胞激活型NRAS p.Q61R（NRAS）突变相关。KLA的特征是淋巴管畸形，可导致积液和凝血病。本研究的目的是建立一种体内小鼠模型，以确定淋巴管内皮细胞中Nras突变的产前表达是否会诱发KLA患者所具有的疾病特征。
使用Cre-loxP系统在表达淋巴管内皮透明质酸受体1（Lyve1）的细胞中条件性表达Nras，Lyve1是淋巴管及其他类型内皮细胞的标志物，在胚胎第7.5天开始表达。由于幼崽出生后无法存活，因此在胚胎第14.5天、15.5天和18.5天收集胚胎，进行大体分析、组织学和免疫染色以及器官整体装片观察。
NRAS染色显示Nras突变胚胎中有强烈的重组，且Nras定位于血管异常部位。Nras突变胚胎有明显水肿，颈淋巴囊畸形，伴有异常的Lyve1阳性细胞团。Nras突变胚胎背部皮肤的淋巴管网络分支点减少，血管直径增加。Nras突变胚胎有严重的肝脏缺陷，其特征是血管紊乱和扩张。到胚胎第18.5天，Nras突变胚胎死亡。
在Lyve1阳性细胞中条件性表达Nras会导致小鼠胚胎出现水肿、淋巴管发育异常和肝脏血管缺陷。这些发现进一步支持了NRAS在KLA病理生理学中作为淋巴管过度生长、血管扩张和功能障碍驱动因素的作用。
