Erythropoiesis - Injury and Recovery

描述（由申请人提供）：我们每秒从骨髓中合成和释放超过200万个红细胞，以维持循环稳态水平。红细胞生成系统的大量输出使其成为一个对正常生理功能至关重要的过程，但也是一个对辐射等直接损伤非常敏感的过程。辐射损伤为研究红细胞系损伤、恢复和调节机制提供了一个独特的模型，并允许更深入地了解红细胞生成作为一个动态过程。该建议的总体目标是更好地理解亚致死辐射模拟的异种毒性暴露后红系系损伤和恢复的机制。通过传统的集落试验和新的多光谱成像流式细胞术（MIFC）分析获得的初步数据表明，红系祖细胞和前体细胞在4灰色照射后48小时内严重耗尽，然后在照射后5天开始迅速增加。目的1研究将进一步确定红系祖细胞和前体群体的放射敏感性差异和恢复的时间过程，并探索亚致死辐射损伤后红系丧失的潜在凋亡机制。有趣的是，初步研究结果表明，晚期红系祖细胞（CFU-E）可能独立于更不成熟的祖细胞（BFU-E）恢复。基于这些数据，我们假设晚期红细胞祖细胞在一种改良的应激红细胞生成反应中增殖，这是辐射后红细胞恢复波的原因。因此，Aim 2将研究在传统应激红系反应中重要的内源性化合物，如促红细胞生成素（EPO）、干细胞因子（SCF）和糖皮质激素，以及它们各自的信号通路，在红系辐射恢复过程中对CFU-E细胞的刺激和随后的增殖的作用。最后，Aim 3将结合Aim 1损伤和Aim 2恢复的潜在机制，确定外源性细胞因子（如EPO和SCF）是否可以减少损伤并促进红系的恢复。总的来说，这些实验将通过研究其对辐射的潜在敏感性和损伤后恢复反应的机制，为正常造血提供更全面的了解。这些研究将最终导致新的治疗方法，以保护和减轻造血系统免受致裂剂，如放疗和化疗。

DESCRIPTION (provided by applicant): We synthesize and release more than 2 million red blood cells per second from our bone marrow to maintain circulating steady-state levels. This massive output of the erythropoietic system makes it a process that is essential for normal physiological function but also one that is exquisitely sensitive to direct injury such as radiation. Radiation injury provides a unique model for study of erythroid lineage injury, recovery, and regulation mechanisms and allows for a more thorough understanding of erythropoiesis as a dynamic process. The overall aim of this proposal is to better understand the mechanisms of injury and recovery of the erythroid lineage following xenotoxic exposure as modeled by sublethal radiation. Preliminary data obtained through traditional colony assays in combination with a novel multispectral imaging flow cytometry (MIFC) analysis indicate that erythroid progenitors and precursors are severely depleted at 48 hours post 4 Grey irradiation followed by a rapid increase beginning at 5 days post- irradiation. Aim 1 studies will further define the time course of differential radiosensitivity and recovery of erythroid progenitor and precursor populations as well as explore potential apoptotic mechanisms underlying erythroid loss following sublethal radiation injury. Interestingly, preliminary findings suggest that late-stage erythroid progenitors (CFU-E) may recover independent of more immature (BFU-E) progenitors. Based on these data, late-stage erythroid progenitors are hypothesized to proliferate in a modified stress erythropoiesis response that is responsible for the wave of erythroid recovery post-radiation. Therefore, Aim 2 will investigate the role of endogenous compounds important in the traditional stress erythroid response, such as erythropoietin (EPO), stem cell factor (SCF), and glucocorticoids, and their respective signaling pathways on the stimulation and subsequent proliferation of CFU-E cells during the recovery of the erythroid lineage from radiation. Finally, Aim 3 will combine proposed mechanisms underlying injury in Aim 1 and recovery in Aim 2 by determining if exogenous administration of cytokines such as EPO and SCF can reduce injury and enhance recovery of the erythroid lineage. Overall, these experiments will provide a more thorough understanding of normal hematopoiesis by investigating both its underlying sensitivity to radiation and the mechanisms of its recovery response following injury. These studies will ultimately lead to new treatments to protect and mitigate the hematopoietic system from clastogenic agents such as radiation and chemotherapy.