Mechanisms Regulating Megakaryocyte Development

描述（由申请方提供）：巨核细胞（MK）负责产生血小板，对血液稳态有重大影响。MK在血细胞中是独特的，其在血小板生物发生之前获得多倍性状态。不受控制的MK增殖和解除管制的多倍化是一些血细胞病理的标志。我们最近的研究暗示赖氨酰氧化酶（LOX）在MK倍性和增殖的调节。此修订后的竞争性续期申请调查了LOX在这些过程中的作用。LOX是已知的纤维化反应的细胞外调节剂，通过交联基质蛋白起作用。虽然MK释放的生长因子，如血小板衍生生长因子-β（PDGF-ss），在MK白血病相关骨髓纤维化的MK谱系扩展中的作用已被证实，但这种情况的许多方面仍然难以捉摸，目前的治疗方法基本上无效。我们的初步研究结果表明，LOX在正常MK池中以低水平表达，主要是在低倍性细胞中。然而，LOX在与骨髓纤维化相关的炎性MK中是丰富的，并且被PDGF-β上调。我们发现，LOX酶活性的抑制显着减少PDGF-SS结合细胞和PDGF-SS诱导的MKs的扩增。我们还进行了新的观察，即LOX前加工的产物LOX-PP抑制MK多倍化。基于这些发现，我们推测，脂氧合酶在恶性或白血病MK中的上调在MK扩增、抑制多倍体和基质沉积中起关键作用。为了验证这一点，我们提出了三个具体的 目标：1.阐明LOX-PP对MK多倍体化的影响机制; 2.探讨LOX对PDGF-ss诱导的MK扩增的影响机制; 3.确定体内LOX表达改变对MK扩增、多倍性和骨髓纤维化的影响。了解LOX和LOX-PP如何调节MK增殖和多倍化将确定控制这些过程的新目标，为MK相关疾病的新治疗干预措施的开发提供信息，并进一步了解MK倍性和增殖的生理控制。 公共卫生相关性：巨核细胞（MK）负责产生血小板，对血液稳态有重大影响。MK在血细胞中是独特的，其在血小板生物发生之前获得多倍性状态。不受控制的MK增殖和失调的多倍化是血细胞病理学的标志，这项研究提案的重点是MK扩增和多倍化调节的新方面，涉及赖氨酰氧化酶（LOX）作为新发现的这些过程的调节剂。

DESCRIPTION (provided by applicant): Megakaryocytes (MKs) are responsible for the production of platelets, which have a major impact on blood homeostasis. MK is unique among blood cells in attaining states of polyploidy, which precedes platelet biogenesis. Uncontrolled MK proliferation and deregulated polyploidization are hallmarks of some blood cell pathologies. Our recent studies implicate Lysyl Oxidase (LOX) in the regulation of MK ploidy and proliferation. This revised competitive renewal application investigates the role of LOX in these processes. LOX is a known extracellular regulator of the fibrogenic response, acting by cross-linking matrix proteins. Although the role growth factors released by MK, such as Platelet-Derived Growth Factor-ss (PDGF-ss), has been documented in the expansion of the MK lineage in MK leukemia-associated myelofibrosis, many aspects of this condition remain elusive, and current treatments are largely ineffective. Our preliminary findings indicate that LOX is expressed at low levels in a pool of normal MKs, primarily in the low-ploidy cells. However, LOX is abundant in displastic MKs associated with myelofibrosis, and is upregulated by PDGF-ss. We found that inhibition of LOX enzyme activity significantly diminished PDGF-ss binding to cells and PDGF-ss-induced expansion of MKs. We also made the novel observation that LOX-PP, a product of pre- LOX processing, inhibits MK polyploidization. Based on these findings, we hypothesize that upregulated LOX in displastic or leukemic MKs has a pivotal role in MK expansion, inhibition of polyploidy, and matrix deposition. To test this, we propose three specific aims: 1. Elucidate the mechanism of effect of LOX-PP on MK polyploidization; 2. Investigate the mechanism of effect of LOX on PDGF-ss-induced MK expansion; and 3. Determine the consequences of altered LOX expression in vivo on MK expansion, polyploidy and myelofibrosis. Understanding how LOX and LOX-PP regulates MK proliferation and polyploidization will identify new targets for control of these processes, informing the development of new therapeutic interventions for MK-related disorders and providing further insight into the physiological control of MK ploidy and proliferation. PUBLIC HEALTH RELEVANCE: Megakaryocytes (MKs) are responsible for the production of platelets, which have a major impact on blood homeostasis. MKs is unique among blood cells in attaining states of polyploidy, which precedes platelet biogenesis. Uncontrolled MK proliferation and deregulated polyploidization are hallmarks of blood cells pathology, and this research proposal focuses on novel aspects of regulation of MK expansion and polyploidization, involving Lysyl Oxidase (LOX) as a newly identified regulator of these processes.