[Influence of BMP4 on Regulation of Cell Cycle and Apoptosis of Hematopoietic Stem Cells/Progenitor Cells and Its Mechanism in Chemotherapy-Induced Myelosuppression].

To explore the effect of bone morphogenetic protein 4(BMP4) on the cell cycle and apoptosis of hemaropoictic stem and progenitor cells (HSPC) in conditions of 5-fluorouracil (5-FU)-inducing bone marrow suppression and stress hemogenesis, and its possible mechanism.The C57BL transgenic mice with BMP4 overexpression were established and were enrolled in transgenic group (BMP4 group), at the same time the wild type mice matching in age, sex and body weight were selected and were enrolled in control group (WT group). The bone marrow suppression was induced by injection with 5-FU in dose of 150 mg/kg, then the nucleated cells were isolated from bone marrow. After the HSPCs were markered with C-kit/sca-1 fluorescent antibodies, the changes of cell cycle and apoptosis of HSPC were detected by Aunexin V/PI and Ki67/DAPI double staining; the cell cycle-essociated hemotopoietic regulatory factors were detected by RT-qPCR.Under physiologic status, there were no significant differences in cell cycle and apoptotic rate of HSPC between WT group and BMP-4 group. After the bone marrow was suppressed, the ratio of HSPC at G0 phase in BMP4 group significantly decreased(P＜0.05); the apoptosis rate of HSPC significantly increased(P＜0.05); the mRNA expression levels of hypoxia-inducing factor Hif-1α and chemotactic factor CXCL12 in stroma of BMP4 group were down-regulated significanfly(P＜0.05).Under non-physiologic conditions such as stress hemogenesis or bone marrow suppression, the up-regulation of BMP4 can promote HSPC into cell cycle and apoptosis of HSPC, moreover, the BMP4 may play a regulatory role for cell cycle of HSPC through direct or indirect down-regulation of Hif-1α and CXCL-12 expressions.化疗抑制下骨髓BMP4对造血干/祖细胞周期、凋亡的调控及其机制.探讨5-氟尿嘧啶（5-FU）诱导的骨髓抑制或应激造血条件下骨形态发生蛋白4（bone morphogenetic protein 4，BMP4）对造血干/祖细胞（HSPC）的周期、凋亡调控的作用及其相关机制.设计构建BMP4过表达的C57BL/6转基因小鼠（transgenec group），选取周龄、性别、体重相匹配的野生型（WT）雌鼠为对照组，各实验重复3次。5-FU以150 mg/kg的剂量诱导骨髓抑制模型，提取骨髓有核细胞。通过c-kit/Sca-1荧光抗体双标HSPC，分别用Annexin V/PI和Ki-67/DAPI双染法观察其凋亡和细胞周期的变化。RT-g-PCR检测周期相关的造血调控因子，探讨BMP4调控HSPC细胞周期的分子机制.生理状态下，野生型组和转基因组HSPC细胞周期和凋亡率无明显差异。骨髓抑制后，BMP4过表达小鼠骨髓中HSPC的G0期比例明显降低（P＜0.01），凋亡率明显上升（P＜0.05）。BMP4过表达小鼠骨髓基质中维持HSPC静息的低氧诱导因子Hif-1α和趋化因子CXCL12水平明显下调（P＜0.01）.在造血应激或骨髓抑制等非生理条件下，BMP4蛋白上调能促进HSPC进入细胞周期，促进其凋亡，且可能通过直接或间接下调Hif-1α和CXCL12表达来发挥对HSPC的周期调控功能.