脂肪细胞对造血应激后造血恢复的作用及机制研究

The delay of hematopoietic recovery with a portion of patients received high-dose chemotherapy or bone marrow transplantation is a intractable issue during clinical theatment of Leukemia. So far, the mechanism of delay of hematopoietic recovery remains unclear. Previous researches focused on inducing directly on hematopoietic stem cell proliferation and differentiation,while few studys focus on the change of hematopoietic microenvironment and its intervention. Abnormal proliferation of adipocytes are often found in bone marrow(BM) of hematopoietic aplastic disease.Our previous research investigates that adipogenesis inhibitors promote a higher peripheral WBCs in hematopoiesis stress model mice as well as improve the hypoxia in BM. Thus adipocytes may play an important role on hematopoietic recovery and microenvironment reconstruction. This study explores the role of adipocytes on hematopoiesis by constructing a model induced by hematopoietic stress, as well as investigating the abilities of cell migration and the cell proliferation. The regulation of adipocytes on blood sinus endothelial cells(SECs) reconstitution during hematopoietic recovery is also investiated through the regulation on VEGF/VEGFR2 signal pathways of SECs by adipocytes, thus clarifing the mechanism of hematopoietic suppress by adipocytes which induce a hypoxic niche. Meanwhile, adipogenesis inhibitor and the traditional hematopoietic mobilization agent G-CSF are combinated to investigated the combination effect on hematopoietic recovery. This research is due to domanstrate the functions of BM adipocytes on hematopoietic microenvironment and hematopoietic recovery,expecting a new approach of clinical treatment of hematopoietic recovery.

大剂量化疗后及骨髓移植后部分病人出现造血恢复延迟是临床上白血病治疗的一大难题。迄今为止，造血恢复延迟的机制仍不清楚。既往研究集中于直接刺激造血干细胞增殖分化，而对造血微环境的变化及其干预研究甚少。许多造血障碍性疾病骨髓中常伴随脂肪细胞异常增生，而前期研究发现，脂肪抑制剂可促进造血应激模型小鼠外周白细胞升高，并改善骨髓低氧状态。提示脂肪细胞对造血恢复及微环境改造可能有重要作用。本研究以构建造血应激模型为基础，分别从细胞迁移和细胞增殖俩个方面研究脂肪细胞对造血功能的作用，并通过脂肪细胞对造血恢复时血窦内皮细胞（SECs）VEGF/VEGFR2信号通路的调控研究，探索其对SECs重建的调控机制，阐明脂肪细胞通过诱导低氧微环境来抑制造血的机制。并研究脂肪抑制剂与传统造血动员剂G-CSF联合使用对造血恢复的作用。阐明骨髓脂肪细胞在造血微环境和造血恢复的功能，为临床治疗造血恢复提供新思路。

长期化疗及造血干细胞移植后造血恢复延迟是治疗血液系统恶性疾病的重大难题之一，患者骨髓往往表现为造血增生低下伴脂肪细胞增生。长期以来，骨髓脂肪细胞仅被认为是骨髓中的填充物，近期有研究表明骨髓脂肪细胞可能具有负性造血调控作用，但其功能仍存在争议且相关机制不明。为了研究脂肪细胞在造血应激后造血恢复中的作用及机制，本课题做了以下工作：1）建立骨髓造血应激下脂肪细胞增生动物模型，为后续研究脂肪细胞在造血应激后造血恢复中的作用建立了研究基础。2）脂肪生成抑制剂BADGE可抑制Ara-C诱导的长骨脂肪细胞增生及骨髓中脂肪相关因子的表达，促进化疗后外周血象及骨髓造血功能的恢复。3）脂肪生成激动剂罗格列酮诱导的骨髓脂肪化对稳态造血无影响，可维持LSK细胞的增殖及迁移，抑制粒系形成，罗格列酮诱导的基质细胞脂肪化可明显抑制共培养的髓系祖细胞。4）体内外实验初步验证了细胞内活性氧自由基（ROS）参与了造血应激导致的脂肪细胞增多，而抗氧化剂NAC可以通过清除ROS以减轻造血应激导致的脂肪细胞增多。5）体外实验证明脂肪细胞通过其分泌的脂联素影响造血干祖细胞的增殖及周期，并且通过抗体中和脂联素的作用后可逆转造血干祖细胞相应的改变。6）利用脂肪因子芯片筛选与植入功能不良相关的脂肪因子，初步选定21个有显著表达差异的脂肪因子。首次探讨了脂联素在造血干细胞移植后患者中的表达情况，从临床角度证明了脂联素蛋白水平增高是植入功能不良的危险因素。7）失血性贫血小鼠骨髓间充质干细胞向成骨成脂分化的变化：在骨髓造血功能活跃期小鼠骨髓间充质干细胞向成骨细胞分化能力增强，向脂肪细胞分化能力减弱。本课题以构建造血应激模型为基础，通过脂肪生成激动剂和脂肪抑制剂干预，证明了脂肪细胞对造血应激后造血恢复的负调控作用，且深入探索了造血应激导致脂肪细胞增多的机制及脂肪细胞影响造血的机制，且与临床结合，筛选了植入功能不良相关的脂肪因子并揭示了脂联素蛋白水平增高是植入功能不良的危险因素。该研究有助于揭示大剂量化疗后造血恢复延迟或骨髓移植后植入功能不良的机制，为造血恢复提供新的治疗思路和治疗靶点。