CD44 connects autophagy decline and aging in the vascular endothelium. CD44 connects autophagy decline and aging in the vascular endothelium

The decline of endothelial autophagy is closely related to vascular senescence and disease, although the molecular mechanisms connecting these outcomes in vascular endothelial cells (VECs) remain unclear. Here, we identify a crucial role for CD44, a multifunctional adhesion molecule, in controlling autophagy and aging in VECs. The CD44 intercellular domain (CD44ICD) negatively regulates autophagy by reducing PIK3R4 and PIK3C3 levels and disrupting STAT3-dependent PtdIns3K complexes. CD44 and its homologue clec-31 are increased in aging vascular endothelium and Caenorhabditis elegans, respectively, suggesting that an age-dependent increase in CD44 induces autophagy decline and aging phenotypes. Accordingly, CD44 knockdown ameliorates age-associated phenotypes in VECs. The endothelium-specific CD44ICD knock-in mouse is shorter-lived, with VECs exhibiting obvious premature aging characteristics associated with decreased basal autophagy. Autophagy activation suppresses the premature aging of human and mouse VECs overexpressing CD44ICD, function conserved in the CD44 homologue clec-31 in C. elegans. Our work describes a mechanism coordinated by CD44 function bridging autophagy decline and aging. Overall design: We knock-down CD44 in HUVECs by siRNA (S1, S2). We then analyzed the differentially expressed autophagy related genes compared with control (SC) using the Affymetrix Human GeneChip® Gene1.0 ST platform. Array data was processed by Affymetrix Exon Array Computational Tool. No techinical replicates were performed.

内皮细胞自噬（endothelial autophagy）的衰退与血管衰老及血管疾病密切相关，尽管目前尚不清楚连接血管内皮细胞（vascular endothelial cells, VECs）中这些表型的分子机制。本研究明确了CD44——一种多功能黏附分子——在调控VECs自噬与衰老过程中的关键作用。CD44胞内结构域（CD44 intercellular domain, CD44ICD）通过降低PIK3R4与PIK3C3的表达水平，并破坏依赖STAT3的磷脂酰肌醇3-激酶复合物（STAT3-dependent PtdIns3K complexes），对自噬产生负调控作用。在衰老血管内皮组织中CD44表达上调，而在秀丽隐杆线虫（Caenorhabditis elegans）中其同源基因clec-31的表达亦升高，这提示CD44的年龄依赖性上调会诱导自噬衰退及衰老表型。相应地，敲低CD44可改善VECs的衰老相关表型。内皮细胞特异性CD44ICD敲入小鼠的寿命更短，其VECs表现出明显的早衰特征，且伴随基础自噬水平降低。自噬激活可抑制过表达CD44ICD的人源及小鼠VECs的早衰表型，这一功能在秀丽隐杆线虫的CD44同源基因clec-31中保守存在。本研究阐明了一条由CD44介导、连接自噬衰退与衰老的分子调控机制。

实验设计概述：我们通过小干扰RNA（siRNA）在人脐静脉内皮细胞（human umbilical vein endothelial cells, HUVECs）中敲低CD44（分为实验组S1、S2），并以阴性对照siRNA（SC）作为对照，利用Affymetrix Human GeneChip® Gene1.0 ST 芯片平台分析差异表达的自噬相关基因。芯片数据通过Affymetrix Exon Array Computational Tool进行处理，未设置技术重复。