血液血管干细胞双向分化促进放射损伤造血重建的机制研究

The therapy of acute radiation disease (hematopoietic type) hasn't made progress and very few extremely heavy cases can survive over a long period of time. The present therapeutic regimen is confined to the recovery of bone marrow hematopoietic cells. However, blood vessel destruction is almost simultaneous with blood cell necrosis in bone marrow, so accelerating blood vessel renovation is critical to bone marrow hematopoietic reconstitution. The hemangioblast is defined as a precursor cell with the potential to differentiate into both hematopoietic and endothelial cell lineages. So it is certainly of dominant advantage of reconstructing marrow failure induced by radiation. This study intends to imitate embryo hematopoiesis of aorta-gonad-mesonephros (AGM) region, separate and cultivate hemangioblasts from mouse AGM region, and establish the hemangioblast transplantation mouse model after marrow injury induced by radiation, in order to analyze the rules of hemangioblasts reconstructing marrow hematopoiesis and vessels. Our previous research showed that shh (sonic hedgehog) protein regulates the function of hemangioblasts in autocrine and paracrine way，so it will be illustrated that specific actions of shh signaling pathway on regulating the proliferation and differentiation of hemangioblasts by intervening shh pathway in vitro and in vivo, in order to explore the potential clinical value of exogenous shh peptide to hematopoietic radiation injury. The study will provide an effective way to treat marrow injury induced by radiation and accelerate the hematopoietic reconstitution progress.

急性骨髓型放射病的治疗一直未取得突破性进展，极重度患者极少长期存活。目前其救治手段局限于骨髓造血细胞的恢复，而放射损伤时骨髓血管系统的破坏与造血细胞退变坏死同步发生，因此，加速微血管系统的修复对促进骨髓造血重建起关键作用。血液血管干细胞是造血细胞和血管内皮细胞的共同祖先，具有双向分化的潜能，对重建放射性骨髓衰竭具有先天的优势。本研究拟模仿胚胎主动脉-性腺-中肾（AGM）区的造血发生，分离培养小鼠AGM区血液血管干细胞，建立放射损伤骨髓衰竭血液血管干细胞移植模型，解析该干细胞重建骨髓造血及血管系统的规律。申请者前期研究表明，Shh蛋白通过自分泌及旁分泌机制调节血液血管干细胞的功能，据此本研究还通过体内外正反向干预Shh信号通路，阐明其在调控血液血管干细胞增殖分化中的具体作用，探讨外源性Shh肽在骨髓型放射病治疗中的临床应用价值。本研究将为治疗放射损伤骨髓衰竭提供新策略，加快患者造血重建进程。

急性骨髓型放射病的治疗一直未取得突破性进展，极重度患者极少长期存活。目前其救治手段局限于骨髓造血细胞的恢复，而放射损伤时骨髓血管系统的破坏与造血细胞退变坏死同步发生，因此，加速微血管系统的修复对促进骨髓造血重建起关键作用。血液血管干细胞是造血细胞和血管内皮细胞的共同祖先，具有双向分化的潜能，对重建放射性骨髓衰竭具有先天的优势。本研究分离培养了小鼠胚胎主动脉-性腺-中肾(AGM)区血液血管干细胞，建立了放射损伤骨髓衰竭血液血管干细胞移植模型，从亚致死剂量（6Gy）和致死剂量（7.5Gy）两个辐射剂量组实验结果来看，血液血管干细胞移植能有效促进放射损伤骨髓衰竭小鼠骨髓造血系统和血管系统的重建。本研究还通过正反向干预Shh信号通路，阐明了其在调控血液血管干细胞增殖分化中的具体作用，探讨了外源性Shh肽在骨髓型放射病治疗中的临床应用价值。在存在AGM区基质细胞的微环境条件下，外源性Shh活性肽可使血液血管干细胞长久地保持旺盛的增殖状态，并不诱导血液血管干细胞的凋亡与分化，同时还可促进细胞迁移，说明Shh细胞通路对血液血管干细胞的作用存在时空的差异，细胞外环境信号对Shh信号通路具有整合和调试的作用。本研究将为治疗放射损伤骨髓衰竭提供新策略，加快患者造血重建进程。

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