PTRF在造血干细胞衰老中的作用

In general, aging is accompanied by a diminished capacity to maintain tissue homeostasis and to repair tissues after injury, suggesting an imbalance in cell loss and renewal. Adult tissue stem cells maintain many tissues through the regulated generation of increasingly committed progenitor cells and ultimately terminally differentiated cells. However, how somatic stem cells change with aging is only beginning to be understood. .Hematopoietic stem cells (HSCs) are the most highly self-renewing cells. Nevertheless, the HSCs does not escape the detrimental effects of the aging process. With aging, HSCs regenerative potential diminishes and skewing from lymphopoiesis toward myelopoiesis occurs. These aging effects are clinically manifested by an increase in the incidence of myeloproliferative diseases, including leukemia, a decline in adaptive immunity and a greater propensity to anemia. However, how HSCs change with aging is not clear. Polymerase I and transcript release factor (PTRF, also known as Cavin-1) has originally been identi?ed as a nuclear factor that regulates transcription and enhances ribosomal RNA synthesis. Recently PTRF is reported to be an essential component in the biogenesis and function of caveolae. We showed that overexpression of PTRF induced features characteristic of cellular senescence in human fibroblast cells. The role of PTRF in cellular senescence is dependent on the caveolae/p53/p21 pathways. But the function of PTRF in HSCs self-renewing, differentiation and senescence remains unknown. In our study, we use PTRF transgenic mice and caveolin-1 knockout mice to investigated the role of PTRF in regulation of stem cell senescence, and in p53/p21 and ROS passways, then explore the effects for tissues and organs aging.

成体干细胞是维持组织稳态的重要因素，并在机体衰老进程中起着关键的作用。造血干细胞衰老会造成造血和免疫系统功能的下降，包括增加白血病发病率，降低机体获得性免疫功能和倾向于贫血等。有关造血干细胞衰老的机理还缺乏深入地研究。我们前期结果证明，PTRF激活caveolae/p53/p21通路诱导了人胚肺成纤维细胞的衰老，在体细胞衰老中有着重要的作用。但是，PTRF在成体干细胞及组织水平上对衰老的作用还没有研究。本项目拟利用已有的PTRF转基因小鼠和caveolin-1敲除小鼠研究PTRF在造血干细胞中对胞膜窖的形成和功能的影响，揭示PTRF对于造血干细胞衰老的分子调控机制，以及对衰老相关的p53/p21通路和ROS通路的调节作用，进而研究PTRF对于机体组织衰老的影响，为研究造血干细胞及相关组织器官的衰老提供基础。

成体干细胞是维持组织稳态的重要因素，并在机体衰老中起着重要的作用。干细胞的功能降低是机体衰老的关键因素，但是干细胞调节机体衰老的机制还不清楚。PTRF对于维持胞膜窖的结构和功能起着重要作用，在体细胞中PTRF诱导人胚肺成纤维细胞的衰老。但是在成体干细胞及组织水平对衰老的影响还不清楚。本研究利用PTRF 转基因和Cav-1敲除小鼠研究PTRF对于造血干细胞衰老及组织衰老的影响。首先，我们发现PTRF转基因小鼠在骨髓中造血干细胞数量增加，同时造血干细胞显示衰老的表型，包括细胞周期停滞在G1期，衰老相关的β-gal半乳糖苷酶阳性细胞增加，细胞内ROS水平增加。接着，我们利用体外成克隆实验和体内竞争性移植实验发现PTRF转基因小鼠的造血干细胞自我更新能力降低，造血重建能力降低。然后，利用real-time PCR检测了与PTRF相关的信号通路，发现造血干细胞中PTRF过表达激活了p16/RB和p53/p21通路。最后，我们利用PTRF转基因小鼠和cav-1敲除小鼠杂交，发现cav-1敲除后，PTRF过表达诱导了造血干细胞衰老表型降低，因此PTRF诱导的造血干细胞衰老主要是通过cav-1/p53/p21通路。本项目的结论是PTRF过表达激活cav-1/p53/p21通路诱导造血干细胞衰老，降低造血干细胞自我更新和造血重建的能力。