Role of Brain Macrophages in the Pathogenesis and Treatment of Globoid Cell Leukodystrophy

球样细胞脑白质营养不良（GLD）或Krabbe是一种致命的儿科神经退行性疾病， GALC突变。它之所以如此命名，是由于球形细胞巨噬细胞的出现。主要障碍是 治愈GLD是治疗中枢神经系统（CNS）病理。造血干细胞移植 是唯一的治疗方法，但不能治愈，必须在婴儿早期症状前给药。HSCT 被认为是通过供体巨噬细胞的治疗性植入和球状细胞的替代来起作用，但在 大脑，效率低下。尽管是GLD的特异性特征，但对大脑中的球状细胞知之甚少 - 它们的功能、起源和形成。球状细胞是否起源于胚胎组织尚不清楚 常驻小胶质细胞或HSC衍生的浸润性巨噬细胞，它们致病的程度，以及它们是否 更换是GLD治疗的关键。这是一个关键的知识差距，限制了更多人的进步。 有效的GLD疗法，是本提案的重点。我们的中心假设是球状细胞是 独特的反应性小胶质细胞和“真正的”小胶质细胞的强大替代足以治疗GLD CNS 神经病理学我们是通过小鼠直接CNS移植研究脑巨噬细胞的专家。的 Twitcher（GALCKO）小鼠是广泛接受的GLD模型。我们创造了新的方法来1）区分 小胶质细胞、浸润性巨噬细胞和移植的供体巨噬细胞彼此分离，以及2）替代宿主 脑巨噬细胞与直接注射的细胞在高效率没有HSCT，包括通过工程的第一个 CSF1R的小分子受体抗性变体，CSF1R是脑巨噬细胞的存活受体。在这一提议中， 我们将在GALCKO模型中应用这些新方法来确定脑巨噬细胞在GLD中的作用 发病机制和治疗。在目标1中，我们将定义所有反应性脑的起源和转录组学身份， 巨噬细胞，包括球状细胞，在GALCKO，包括HSCT后。这些知识有望揭示新的 GLD的治疗目标。在目标2中，我们将检验GALCKO小胶质细胞的直接替代 与健康的替代物消除了球状细胞，并推动了HSCT的神经治疗效果。如果这是真的， 这种方法具有巨大的转化潜力，可以最大限度地提高植入效率， 细胞治疗的窗口。最后，在目标3中，我们将确定HSC衍生的细胞是否是有效的小胶质细胞， 考虑到CNS中非小胶质细胞巨噬细胞的独特功能，这将指导今后的工作， 提高细胞疗法治疗脑部疾病的疗效。这些目标的实现将填补长期以来 关于小胶质细胞和其他巨噬细胞在发病机制和治疗中的作用的知识差距 小儿神经退行性疾病

Globoid cell leukodystrophy (GLD), or Krabbe, is a fatal pediatric neurodegenerative disease caused by mutations in GALC. It is so-named due to the appearance of globoid cell macrophages. The major hurdle to curing GLD is treatment of central nervous system (CNS) pathology. Hematopoietic stem cell transplant (HSCT) is the only treatment, but is not curative, and must be administered presymptomatically in early infancy. HSCT is thought to work by therapeutic engraftment of donor macrophages and replacement of globoid cells, but in the brain, does so inefficiently. Despite being pathognomonic for GLD, little is known about globoid cells in the brain - their function, origin, and formation. It is unknown if globoid cells arise from embryonically-derived tissue resident microglia or HSC-derived infiltrating macrophages, the degree to which they are pathogenic, and if their replacement is key to GLD treatment. This is a critical knowledge gap that has limited the advancement of more effective GLD therapies and is the focus of this proposal. Our central hypothesis is that globoid cells are unique reactive microglia and that robust replacement by “true” microglia is sufficient to treat GLD CNS neuropathology. We are experts in the study of brain macrophages by direct CNS transplantation in mice. The twitcher (GALCKO) mouse is a widely accepted model of GLD. We created new methods to 1) distinguish microglia, infiltrating macrophages, and transplanted donor macrophages from each other and 2) replace host brain macrophages with directly injected cells at high efficiency without HSCT, including by engineering the first small molecule inhibitor-resistant variant of CSF1R, a survival receptor for brain macrophages. In this proposal, we will apply these new methods in the GALCKO model to determine the role of brain macrophages in GLD pathogenesis and treatment. In Aim 1, we will define the origin and transcriptomic identity of all reactive brain macrophages, including globoid cells, in GALCKO, including after HSCT. This knowledge promises to reveal new therapeutic targets for GLD. In Aim 2, we will test the hypothesis that direct replacement of GALCKO microglia with healthy surrogates eliminates globoid cells and drives the neurotherapeutic effects of HSCT. If true, this approach has great translational potential to maximize engraftment efficiency and broaden the therapeutic window for cell therapy. Finally in Aim 3, we will determine if HSC-derived cells are effective microglial surrogates, given the distinct functions of non-microglial macrophages in the CNS. This will guide future work to enhance the efficacy of cell therapies for brain diseases. Completion of these aims will fill longstanding knowledge gaps about the role of microglia and other macrophages in the pathogenesis and treatment of pediatric neurodegenerative diseases.