琥珀酸在造血干细胞衰老中的作用及机制研究

Hematopoietic stem cells (HSCs) gradually lose their self-renewal and regenerative potential during aging, indicating by an increased tendency of myeloid differentiation and decreased tendency of lymphoid differentiation. Glycolysis and oxidative phosphorylation are important for HSCs during aging. The metabolite succinate is at the hub of the tricarboxylic acid cycle (TCA), which may be classified as metabolic or non-metabolic functions. Succinate is involved in the inflammatory.Responses, succinylation, as a molecular signal and metabolic energy..we compare the metabolites between aging and young HSCs by Ultra liquid chromatography-mass spectrometry. Succinate was the most significant decreased metabolites, and succinate dehydrogenase was increased in aging HSCs. Succinate could significant increase the HSC number during in vitro culture. Succinate supplementation could also increase HSCs number, and decrease myeloid progenitor cells in vivo. What’s more, succinate supplementation could improve the HSC function and decrease myeloid cell differentiation after transplantation. The oxidative phosphorylation also reduced. The succinylation was significantly increased in aging HSCs, Unexpectedly, the expression of SIRT5, as a desuccinylaiton enzyme, was also high. It suggested that high succilyaiton lead to the low level of succinate in aging HSCs, which play important role in aging.We will try to clarify the regulational function of succinate by means of genetic modification mice model, virus transfection, succinate supplemention and HSC transplantation experiments and population data. These will apply potential molecular targets for HSC aging research.

造血干细胞（Hematopoietic stem cell, HSC）衰老表现为自我更新能力下降及倾向性分化（髓系增加、淋系降低）。糖酵解和氧化磷酸化对HSC衰老起着重要调控作用，琥珀酸是TCA循环的中心环节，有代谢和非代谢的两方面作用，在免疫应答、琥珀酰化修饰、信号分子和能量代谢等方面有重要作用。超高灵敏的微量液相色谱-质谱联用技术仅用万级细胞，能准确检测小鼠HSC代谢物谱。年轻年老小鼠HSC代谢物谱证实琥珀酸在年老HSC中含量降低最显著。体内外补充琥珀酸皆抑制HSC髓系分化，提高其移植后造血重建能力，降低HSC氧化磷酸化水平。年老HSC蛋白琥珀酰化水平明显升高，去琥珀酰化酶SIRT5同样升高。琥珀酰化升高可能导致琥珀酸含量降低。琥珀酸含量对HSC衰老有重要调控作用。本项目拟通过基因敲除小鼠和外源补充琥珀酸及人群样本分析，解析琥珀酸代谢对HSC稳态和衰老的调控机制。

造血干细胞具有自我更新和定向分化的特性。稳态下造血干细胞可平衡分化为淋系细胞和髓系细胞，在衰老和疾病状态下，造血干细胞分化向髓系倾斜，造成免疫能力下降和髓系白血病的高发。文献报道，代谢物对造血干细胞干性维持有重要的调控作用，然而，在造血干细胞分化过程中代谢物的改变和调控作用并不明确。本项目采用少量细胞质谱的方法对小鼠体内、外造血干细胞髓系分化过程中的代谢物进行了系统检测，发现三羧酸循环代谢物在髓系分化及衰老状态下出现显著下降，进一步研究表明三羧酸循环关键代谢物琥珀酸可通过琥珀酰化降低异柠檬酸脱氢酶表达，降低代谢物α-酮戊二酸的含量，抑制造血干细胞髓系分化。本项目首次对造血干细胞衰老及髓系分化状态下的代谢物谱改变进行了系统的检测，发现造血干细胞分化中代谢物-表观遗传调控的新机制。该项目成果对于造血系统衰老及髓系分化相关疾病的治疗有非常重要的意义。