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患者死亡的主要原因。不幸的是，很少有治疗方法可以有效地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（ECs），在辐射损伤后调节造血再生。为了验证这一假设，我们在Tie2+内皮细胞（Tie2Cre;Bak-/-；BaxFl/-小鼠）中产生了缺失凋亡内在介质Bak和Bax的小鼠（Tie2Cre;Bak-/-；BaxFl/-小鼠），发现在Tie2+ ECs中缺失Bak和Bax的小鼠可以免受致死剂量的辐射保护，而在Tie2+ ECs中保留1个Bax等位基因的小鼠仍然高度辐射敏感。我们对Tie2Cre；Bak-/-；在BaxFl/-小鼠中发现了几种分泌蛋白，与放射敏感小鼠相比，放射保护小鼠的分泌蛋白显著上调。鉴定出的一种蛋白质是表皮生长因子（EGF），它不是已知的造血干细胞（hsc）的生长因子，但与对照小鼠相比，放射性保护小鼠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受辐照的小鼠骨髓造血干细胞培养物中添加EGF是否会减轻造血干细胞或祖细胞的辐射损伤。我们的初步结果表明，EGF促进体外辐照后造血干细胞和祖细胞的恢复显著增加。此外，我们发现全身照射（TBI）后的小鼠全身给予EGF，与受照射的对照组小鼠相比，小鼠的存活率显著增加。基于这些初步结果，我们假设EGF是急性辐射病的候选缓解剂，特别是急性辐射损伤后的造血功能衰竭。为了验证我们的假设，我们提出以下具体目标：1)确定全身给药EGF是否能加速辐射损伤小鼠的造血功能恢复，提高其存活率。2)确定EGF减轻辐射对造血干细胞损伤的细胞和信号机制。3)确定EGF治疗是否能改善恒河猴全身照射后的造血恢复。我们的主要目标是提供一种新的、可翻译的、有效的缓解辐射诱导的造血损伤的药物。除了作为减轻急性辐射损伤的潜在作用外，EF还具有潜在的双重用途，可用于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，这些患者的血液恢复经常延迟。

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.