Department of Internal Medicine, Yale Cardiovascular Research Center, Section of Cardiovascular Medicine (J.M.D., R.C., A.N., J.S., K.A.M., D.M.G.), Yale University, New Haven, CT.
Department of Genetics (J.M.D., A.N., J.S., D.M.G.), Yale University, New Haven, CT.
Stroke. 2024 Sep;55(9):2340-2352. doi: 10.1161/STROKEAHA.123.045248. Epub 2024 Aug 12.
TGF (transforming growth factor)-β pathway is central to blood-brain barrier development as it regulates cross talk between pericytes and endothelial cells. Murine embryos lacking TGFβ receptor (activin receptor-like kinase 5) in brain pericytes (mutants) display endothelial cell hyperproliferation, abnormal vessel morphology, and gross germinal matrix hemorrhage-intraventricular hemorrhage (GMH-IVH), leading to perinatal lethality. Mechanisms underlying how ALK5 signaling in pericytes noncell autonomously regulates endothelial cell behavior remain elusive.
Transcriptomic analysis of human brain pericytes with ALK5 silencing identified differential gene expression. Brain vascular cells isolated from mutant embryonic mice with GMH-IVH and preterm human IVH brain samples were utilized for target validation. Finally, pharmacological and genetic inhibition was used to study the therapeutic effects on GMH-IVH pathology.
Herein, we establish that the TGFβ/ALK5 pathway robustly represses ANGPT2 (angiopoietin-2) in pericytes via epigenetic remodeling. TGFβ-driven SMAD (suppressor of mothers against decapentaplegic) 3/4 associates with TGIF1 (TGFβ-induced factor homeobox 1) and HDAC (histone deacetylase) 5 to form a corepressor complex at the promoter, resulting in promoter deacetylation and gene repression. Moreover, murine and human germinal matrix vessels display increased ANGPT2 expression during GMH-IVH. Isolation of vascular cells from murine germinal matrix identifies pericytes as a cellular source of excessive ANGPT2. In addition, mutant endothelial cells exhibit higher phosphorylated TIE2 (tyrosine protein kinase receptor). Pharmacological or genetic inhibition of ANGPT2 in mutants improves germinal matrix vessel morphology and attenuates GMH pathogenesis. Importantly, genetic ablation of in mutant pericytes prevents perinatal lethality, prolonging survival.
This study demonstrates that TGFβ-mediated ANGPT2 repression in pericytes is critical for maintaining blood-brain barrier integrity and identifies pericyte-derived ANGPT2 as an important pathological target for GMH-IVH.
转化生长因子 (TGF)-β 通路在血脑屏障发育中起核心作用，因为它调节周细胞和内皮细胞之间的串扰。大脑周细胞中缺乏 TGFβ 受体（激活素受体样激酶 5）的小鼠胚胎（突变体）表现出内皮细胞过度增殖、血管形态异常和广泛的脑实质出血-脑室出血 (GMH-IVH)，导致围产期死亡。ALK5 信号在周细胞中非细胞自主调节内皮细胞行为的机制仍不清楚。
用 ALK5 沉默对人脑周细胞进行转录组分析，确定差异基因表达。利用具有 GMH-IVH 的突变体胚胎小鼠和早产儿 IVH 脑样本分离的脑血管细胞进行靶标验证。最后，使用药理学和遗传学抑制来研究对 GMH-IVH 病理的治疗效果。
在此，我们通过表观遗传重塑建立了 TGFβ/ALK5 途径通过强烈抑制周细胞中的 ANGPT2（血管生成素-2）。TGFβ 驱动的 SMAD（抑制母亲对抗 decapentaplegic）3/4 与 TGIF1（TGFβ 诱导因子同源盒 1）和 HDAC（组蛋白去乙酰化酶）5 结合形成启动子上的核心抑制复合物，导致启动子去乙酰化和基因抑制。此外，鼠和人脑实质血管在 GMH-IVH 期间显示出 ANGPT2 表达增加。从鼠脑实质中分离血管细胞可鉴定出周细胞是过量 ANGPT2 的细胞来源。此外，突变体的内皮细胞表现出更高的磷酸化 TIE2（酪氨酸蛋白激酶受体）。在突变体中抑制 ANGPT2 的药理学或遗传学可改善脑实质血管形态并减轻 GMH 发病机制。重要的是，突变体周细胞中缺失可预防围产期死亡，延长生存时间。
本研究表明，TGFβ 介导的周细胞中 ANGPT2 抑制对于维持血脑屏障完整性至关重要，并确定周细胞衍生的 ANGPT2 是 GMH-IVH 的一个重要病理靶点。
