In the adult bone marrow (BM), endothelial cells (ECs) are an integral component of the hematopoietic stem cell (HSC)-supportive niche, which modulates HSC activity by producing secreted and membrane-bound paracrine signals. Within the BM, distinct vascular arteriole, transitional, and sinusoidal EC subtypes display unique paracrine expression profiles and create anatomically-discrete microenvironments. However, the relative contributions of vascular endothelial subtypes in supporting hematopoiesis is unclear. Moreover, constitutive expression and off-target activity of currently available endothelial-specific and endothelial-subtype-specific murine cre lines potentially confound data analysis and interpretation. To address this, we describe two tamoxifen-inducible cre-expressing lines, Vegfr3-creER^T2 and Cx40-creER^T2, that efficiently label sinusoidal/transitional and arteriole endothelium respectively in adult marrow, without off-target activity in hematopoietic or perivascular cells. Utilizing an established mouse model in which cre-dependent recombination constitutively-activates MAPK signaling within adult endothelium, we identify arteriole ECs as the driver of MAPK-mediated hematopoietic dysfunction. These results define complementary tamoxifen-inducible creER^T2-expressing mouse lines that label functionally-discrete and non-overlapping sinusoidal/transitional and arteriole EC populations in the adult BM, providing a robust toolset to investigate the differential contributions of vascular subtypes in maintaining hematopoietic homeostasis.

Graphical Abstract

中文翻译：

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用于骨髓内皮细胞亚型功能评估的互补和诱导型 creERT2 小鼠模型

在成人骨髓 (BM) 中，内皮细胞 (EC) 是造血干细胞 (HSC) 支持生态位的一个组成部分，它通过产生分泌的膜结合旁分泌信号来调节 HSC 活性。在 BM 内，不同的血管小动脉、移行和正弦 EC 亚型显示出独特的旁分泌表达谱，并创建解剖学上离散的微环境。然而，血管内皮亚型在支持造血功能中的相对贡献尚不清楚。此外，目前可用的内皮特异性和内皮亚型特异性鼠cre系的组成型表达和脱靶活性可能会混淆数据分析和解释。为了解决这个问题，我们描述了两种他莫昔芬诱导的cre表达系，Vegfr3-creER ^T2和Cx40-creER ^T2，它们分别有效地标记成人骨髓中的窦状/移行和小动脉内皮，而在造血或血管周围细胞中没有脱靶活性。利用已建立的小鼠模型，其中cre依赖性重组持续激活成体内皮内的MAPK信号传导，我们将小动脉EC确定为MAPK介导的造血功能障碍的驱动因素。这些结果定义了互补的他莫昔芬诱导的creER ^T2表达小鼠系，这些小鼠系标记了成人BM中功能离散且不重叠的正弦/移行和小动脉EC群体，为研究血管亚型在维持造血稳态中的差异贡献提供了强大的工具集。

图形概要