Pathogenesis of inherited neuropathies: implication of components of the innate and adaptive immune system

Charcot-Marie-Tooth (CMT) 1型疾病是遗传介导的神经病变，其特征是长度依赖性轴突变性、肌肉萎缩和感觉功能障碍，大大降低了生活质量。尽管到目前为止已经发现了80多种致病基因，但没有一种疾病是可以治疗的。在过去的几年中，我们的研究小组已经证明，在已建立的CMT动物模型中，由csf -1激活的巨噬细胞驱动的低级别炎症大大放大了主要的遗传介导的疾病，因此，这是治疗方法的可能切入点。在上一个资助期内，我们可以明确地识别出与P0het突变体（CMT1B已建立的模型）病变神经纤维结合的全身抗体，作为巨噬细胞脱髓鞘过程中功能的轻度调节剂。这是通过在基因上消融产生抗体的细胞，然后重建不同的抗体组分来实现的。两个观察结果得出结论，抗体的影响相对较小：i)抗体不仅是轻微的，而且是短暂的，即只在较年轻的阶段；Ii)在另一个已建立的模型中，抗体虽然修饰病变的神经纤维，但对发病机制没有检测到作用。为了继续这个项目，我们修改了我们的计划，旨在确定突变雪旺细胞、神经内膜成纤维细胞和致病性巨噬细胞之间三方相互作用的假定主要参与者。基于我们全面的前期研究，我们希望在第一种方法（目标1）中研究雪旺细胞源性生长因子PDGF-A或-B是否在成纤维细胞中启动CSF-1表达，从而激活致病性巨噬细胞。为此，我们将使用细胞培养系统和干扰PDGF-R的体内治疗方法。最终，计划在体内进行复杂、及时的诱导和细胞特异性基因敲除实验，以鉴定相关的PDGF亚型。此外，介导致病性雪旺细胞去分化的巨噬细胞衍生因子也引起了人们的关注（目的2）。作为巨噬细胞驱动的雪旺细胞去分化的候选者，我们考虑了细胞因子tnf - α和tgf - β。通过将骨髓从细胞因子缺陷突变体转移到髓磷脂突变体中，实验剥夺了内在巨噬细胞，我们旨在分析细胞因子缺陷巨噬细胞对致病性雪旺细胞去分化的影响。总而言之，我们的项目希望破译导致CMT突变体致病性炎症的主要分子，以制定相应的治疗策略。

Charcot-Marie-Tooth (CMT) type 1 disorders are genetically-mediated neuropathies that are characterized by length-dependent axonal degeneration, muscle atrophy and sensory dysfunction, substantially reducing quality of life. Although more than 80 culprit genes have been identified so far, none of the disorders is treatable. During the last couple of years, our group has shown that in established animal models of CMT, low-grade inflammation driven by CSF-1-activated macrophages substantially amplifies the primarily genetically-mediated disorders and is, thus, a possible access point for therapeutic approaches.During the last funding period, we could unequivocally identify systemic antibodies binding to the diseased nerve fibers of P0het mutants, an established model for CMT1B, as mild modulators of macrophage function in the demyelinating process. This was achieved by an approach ablating the antibody-producing cells genetically, followed by a reconstitution of distinct antibody fractions. Two observations lead to the conclusion that the impact of the antibodies is comparably minor: i) the antibodies are not only mildly, but also transiently involved, i.e., at younger stages, only; ii) in another established model, the antibodies had no detectectable effect on pathogenesis, although decorating diseased nerve fibers. For a continuation of the project, we modified our plans aiming to identify putative major players in the tripartite interaction between mutant Schwann cells, endoneurial fibroblast and pathogenic macrophages. Based on our comprehensive pilot studies, we want in a first approach (Objective 1) to investigate whether the Schwann cell-derived growth factors PDGF-A or -B initiate CSF-1 expression in fibroblasts that activates pathogenic macrophages. For this purpose, we will use cell culture systems and an in vivo treatment approach interfering with PDGF-R. Eventually, sophisticated, timely inducible and cell specific gene knock-out experiments in vivo are planned to identify the responsible PDGF isoforms. Additionally, possible macrophage-derived factors that mediate pathogenic Schwann cell dedifferentiation are of major interest (Objective 2). As candidates for macrophage-driven Schwann cell dedifferentiation, we consider the cytokines TNF-alpha and TGF-beta. By a combination of bone-marrow transfer from cytokine-deficient mutants into myelin mutants experimentally deprived of intrinsic macrophages, we aim to analyse the impact of the cytokine-deficient macrophages on pathogenic Schwann cell dedifferentiation. All in all, our project wants to decipher the major molecular players leading to pathogenic inflammation in CMT mutants, with the aim to develop corresponding treatment strategies.