MIAT-DHX9 spatiotemporal expression drives venous neointimal hyperplasia through nucleolar homeostasis and mitotic progression

Venous neointimal hyperplasia, characterized by the abnormal proliferation of smooth muscle cells (SMCs), represents a critical contributor to vascular stenosis and therapeutic failure in vascular interventions. Here, we identified a novel role of spatiotemporal nucleolar expression of DExH-box helicase 9 (DHX9) and its binding partner, the long non-coding RNA (lncRNA) MIAT in venous neointimal pathogenesis. In normal SMCs, DHX9 transiently localized to nucleoli during the early S phase. Pathologically, endogenous-activated MIAT facilitated nucleolar DHX9 location and its interaction with PARP1. Activated-MIAT induced mitotic spindle pole location of DHX9 which was destroyed by PARP inhibitor. MIAT also drove SMCs proliferation by accelerating cell cycle progression. While depleting MIAT or DHX9 led to remarkable nucleolar subphase disruption, mitotic breakage-fusion-bridge, and DNA damage. Of note, nucleolar-associated morphology phenotypes analyzed with deep learning are determined to be valuable biomarkers for assessing cellular status and disease progress. MIAT was repressed in cultured human veins, reducing SMCs proliferation and vascular intimal hyperplasia. These results establish the MIAT-DHX9 axis as the central regulator of venous SMCs in arteriovenous fistula and venous graft models. Our study may provide a new avenue to destroy the pathologic spatiotemporal function of DHX9 by targeting MIAT in intimal hyperplasia.静脉新内膜增生（Venous neointimal hyperplasia）以平滑肌细胞（smooth muscle cells, SMCs）异常增殖为核心特征，是血管介入治疗后引发血管狭窄及治疗失败的关键致病因素。本研究阐明了DExH盒解旋酶9（DExH-box helicase 9, DHX9）的时空特异性核仁表达及其结合伴侣长链非编码RNA（long non-coding RNA, lncRNA）MIAT在静脉新内膜发病机制中的全新功能。在正常平滑肌细胞中，DHX9会在S期早期暂时性定位于核仁。病理状态下，内源性激活的MIAT可促进DHX9在核仁中的定位，并增强其与PARP1的相互作用。激活态MIAT能够诱导DHX9的有丝分裂纺锤体极定位，该过程可被PARP抑制剂阻断。此外，MIAT还可通过加速细胞周期进程，促进平滑肌细胞增殖。敲低MIAT或DHX9的表达会引发显著的核仁亚期紊乱、有丝分裂断裂-融合-桥现象以及DNA损伤。值得注意的是，通过深度学习分析得到的核仁相关形态学表型，被证实可作为评估细胞状态与疾病进展的有效生物标志物。在体外培养的人体静脉组织中，MIAT的表达被抑制后，平滑肌细胞增殖与血管内膜增生均得到显著缓解。上述研究结果确立了MIAT-DHX9调控轴作为动静脉瘘及血管移植模型中静脉平滑肌细胞增殖的核心调控通路。本研究为通过靶向MIAT干预内膜增生、破坏DHX9的病理性时空功能提供了全新的研究思路。