Abstract:
Thymus is the main immune organ which is responsible for the production of self-tolerant and functional T cells, but it shrinks rapidly with age after birth. Although studies have researched thymus development and involution in mouse, the critical regulators that arise with age in human thymus remain unclear. We collected public human single-cell transcriptomic sequencing (scRNA-seq) datasets containing 350,678 cells from 36 samples, integrated them as a cell atlas of human thymus. Clinical samples were collected and experiments were performed for validation. We found early thymocyte-specific signaling and regulons which played roles in thymocyte migration, proliferation, apoptosis and differentiation. Nevertheless, signaling patterns including number, strength and path completely changed during aging, Transcription factors (FOXC1, MXI1, KLF9, NFIL3) and their target gene, IGFBP5, were resolved and up-regulated in aging thymus and involved in promoting epithelial-mesenchymal transition (EMT), responding to steroid and adipogenesis process of thymic epithelial cell (TECs). Furthermore, we validated that IGFBP5 protein increased at TECs and Hassall\'s corpuscle in both human and mouse aging thymus and knockdown of IGFBP5 significantly increased the expression of proliferation-related genes in thymocytes. Collectively, we systematically explored cell-cell communications and regulons of early thymocytes as well as age-related differences in human thymus by using both bioinformatic and experimental verification, indicating IGFBP5 as a functional marker of thymic involution and providing new insights into the mechanisms of thymus involution.
摘要:
胸腺是主要的免疫器官,负责产生自我耐受和功能性T细胞,但它在出生后随着年龄的增长迅速缩小。尽管研究已经研究了小鼠胸腺的发育和退化,人类胸腺中随着年龄增长而出现的关键调节因子仍不清楚。我们收集了来自36个样本的350,678个细胞的公共人类单细胞转录组测序(scRNA-seq)数据集,将它们整合为人类胸腺的细胞图谱。收集临床样品并进行实验以进行验证。我们发现早期胸腺细胞特异性信号和调节子在胸腺细胞迁移中起作用,扩散,凋亡和分化。然而,信令模式,包括数字,强度和路径在老化过程中完全改变,转录因子(FOXC1、MXI1、KLF9、NFIL3)及其靶基因,IGFBP5在胸腺衰老过程中表达和上调,并参与促进上皮-间质转化(EMT),对胸腺上皮细胞(TECs)的类固醇和脂肪生成过程的反应。此外,我们验证了IGFBP5蛋白在人和小鼠衰老胸腺的TECs和Hassall小体处增加,IGFBP5的敲除显着增加了胸腺细胞中增殖相关基因的表达。总的来说,我们通过生物信息学和实验验证,系统地探索了早期胸腺细胞的细胞间通讯和调控以及人类胸腺中与年龄相关的差异,表明IGFBP5是胸腺退化的功能标记,并为胸腺退化的机制提供了新的见解。