Epidermal growth factor mitigates radiation-induced hematopoietic failure

描述（由申请人提供）：造血功能衰竭是急性放射病的主要死因。不幸的是，很少有疗法能有效减轻辐射引起的造血系统损伤。我们假设骨髓微环境中的细胞，特别是内皮细胞（EC），调节辐射损伤后的造血再生。作为检验这一假设的手段，我们产生了在Tie 2+内皮细胞内具有细胞凋亡的内在介导物巴克和Bax缺失的小鼠（Tie 2Cre;巴克-/-; Tie Fl/-小鼠），并发现在Tie 2 + EC中具有巴克和Bax缺失的小鼠对致死剂量辐射具有辐射保护作用，而在Tie 2 + EC中保留Bax的1个等位基因的小鼠保持高度的辐射敏感性。我们对来自放射保护的Tie 2Cre;巴克-/-; BIFl/-小鼠的骨髓血清进行了细胞因子阵列分析，并鉴定了与放射敏感小鼠相比在放射保护小鼠中显著上调的几种分泌蛋白。鉴定的一种蛋白质是表皮生长因子（EGF），其不知道是造血干细胞（HSC）的生长因子，但与对照小鼠相比，辐射保护小鼠的BM血清中的浓度增加了18倍。因此，我们在初步研究中测试了在照射的小鼠骨髓HSC的培养物中加入EGF是否引起对HSC或祖细胞的辐射损伤的减轻。我们的初步结果表明，EGF促进照射后造血干细胞和祖细胞在体外的恢复显着增加。此外，我们发现全身照射（TBI）后全身给予EGF的小鼠与照射对照小鼠相比，小鼠存活率显着增加。基于这些初步结果，我们假设EGF是急性放射病的候选缓解剂，特别是急性放射损伤后引起的造血功能衰竭。为了验证我们的假设，我们提出了以下具体目的：1）确定全身施用EGF是否可以加速辐射损伤后小鼠的造血恢复并改善其存活率。2)确定EGF减轻造血干细胞辐射损伤的细胞和信号传导机制。3)确定表皮生长因子治疗是否可以改善恒河猴全身照射后的造血恢复。我们在这项提案中的广泛目标是提供一种新的，可翻译的和有效的缓解辐射诱导的造血损伤。除了其作为急性放射损伤缓解剂的潜在作用外，EF还具有潜在的双重用途，可作为治疗剂加速接受骨髓抑制化疗和/或放疗的患者和接受人脐带血移植的患者的造血恢复，其中血液学恢复经常延迟。

DESCRIPTION (provided by applicant): Hematopoietic failure is the major cause of death in Acute Radiation Sickness. Unfortunately, few therapies exist that are effective at mitigating radiation-induced damage to the hematopoietic system. We hypothesized that cells within the bone marrow microenvironment, specifically endothelial cells (ECs), regulate hematopoietic regeneration following radiation injury. As a means to test this hypothesis, we generated mice bearing deletion of the intrinsic mediators of apoptosis, Bak and Bax, within Tie2+ endothelial cells (Tie2Cre;Bak-/-;BaxFl/- mice) and found that mice with deletion of Bak and Bax in Tie2+ ECs were radioprotected from lethal dose irradiation, whereas mice retaining 1 allele of Bax in Tie2+ ECs remained highly radiosensitive. We performed a cytokine array analysis of bone marrow serum from radioprotected Tie2Cre;Bak-/-;BaxFl/- mice and identified several secreted proteins which were significantly upregulated in radioprotected mice compared to radiosensitive mice. One protein identified was epidermal growth factor (EGF), which is not known to be a growth factor for hematopoietic stem cells (HSCs), but was 18-fold increased in concentration in the BM serum of radioprotected mice compared to control mice. We therefore tested in preliminary studies whether the addition of EGF to cultures of irradiated murine BM HSCs caused the mitigation of radiation injury to HSCs or progenitor cells. Our preliminary results indicate that EGF promotes a significant increase in the recovery of HSCs and progenitor cells in vitro following irradiation. Furthermore, we found that systemic administration of EGF to mice following total body irradiation (TBI) caused a significant increase in mice survival compared to irradiated, control mice. Based on these preliminary results, we hypothesize that EGF is a candidate mitigator of acute radiation sickness and specifically the hematopoietic failure which ensues following acute radiation injury. In order to test our hypothesis, we propose the following Specific Aims: 1) Determine whether systemic administration of EGF can accelerate hematopoietic recovery and improve the survival of mice following radiation injury. 2) Determine the cellular and signaling mechanisms through which EGF mitigates radiation damage to hematopoietic stem cells. 3) Determine whether EGF treatment can improve hematopoietic recovery in rhesus macaques following total body irradiation. Our broad objective in this proposal is to deliver a novel, translatable and potent mitigator of radiation-induced hematopoietic injury. In addition to its potential role as a mitigator of acute radiation injury, EF also has potential dual use as a therapeutic to accelerate hematopoietic recovery in patients receiving myelosuppressive chemotherapy and/or radiotherapy and those undergoing human cord blood transplantation, in which hematologic recovery is frequently delayed.