Department of Immunology and Infection, Biomedical Research Institute, Hasselt University, 3590, Diepenbeek, Belgium.
Department of Neurosciences, Biomedical Research Institute, Hasselt University, 3590, Diepenbeek, Belgium.
J Neuroinflammation. 2022 Apr 29;19(1):102. doi: 10.1186/s12974-022-02458-2.
Spinal cord injury (SCI) elicits a robust neuroinflammatory reaction which, in turn, exacerbates the initial mechanical damage. Pivotal players orchestrating this response are macrophages (Mφs) and microglia. After SCI, the inflammatory environment is dominated by pro-inflammatory Mφs/microglia, which contribute to secondary cell death and prevent regeneration. Therefore, reprogramming Mφ/microglia towards a more anti-inflammatory and potentially neuroprotective phenotype has gained substantial therapeutic interest in recent years. Interleukin-13 (IL-13) is a potent inducer of such an anti-inflammatory phenotype. In this study, we used genetically modified Mφs as carriers to continuously secrete IL-13 (IL-13 Mφs) at the lesion site.
Mφs were genetically modified to secrete IL-13 (IL-13 Mφs) and were phenotypically characterized using qPCR, western blot, and ELISA. To analyze the therapeutic potential, the IL-13 Mφs were intraspinally injected at the perilesional area after hemisection SCI in female mice. Functional recovery and histopathological improvements were evaluated using the Basso Mouse Scale score and immunohistochemistry. Neuroprotective effects of IL-13 were investigated using different cell viability assays in murine and human neuroblastoma cell lines, human neurospheroids, as well as murine organotypic brain slice cultures.
In contrast to Mφs prestimulated with recombinant IL-13, perilesional transplantation of IL-13 Mφs promoted functional recovery following SCI in mice. This improvement was accompanied by reduced lesion size and demyelinated area. The local anti-inflammatory shift induced by IL-13 Mφs resulted in reduced neuronal death and fewer contacts between dystrophic axons and Mφs/microglia, suggesting suppression of axonal dieback. Using IL-4Rα-deficient mice, we show that IL-13 signaling is required for these beneficial effects. Whereas direct neuroprotective effects of IL-13 on murine and human neuroblastoma cell lines or human neurospheroid cultures were absent, IL-13 rescued murine organotypic brain slices from cell death, probably by indirectly modulating the Mφ/microglia responses.
Collectively, our data suggest that the IL-13-induced anti-inflammatory Mφ/microglia phenotype can preserve neuronal tissue and ameliorate axonal dieback, thereby promoting recovery after SCI.
脊髓损伤 (SCI) 会引发强烈的神经炎症反应，进而加剧初始的机械损伤。调控这一反应的关键角色是巨噬细胞 (Mφ) 和小胶质细胞。SCI 后，炎症环境主要由促炎型 Mφ/小胶质细胞主导，它们会导致继发性细胞死亡，并阻碍再生。因此，近年来，将 Mφ/小胶质细胞重编程为具有更强抗炎和潜在神经保护表型的方法引起了广泛的治疗关注。白细胞介素 13 (IL-13) 是诱导这种抗炎表型的有效物质。在本研究中，我们使用基因修饰的 Mφ 作为载体，在损伤部位持续分泌白细胞介素 13 (IL-13 Mφ)。采用 qPCR、Western blot 和 ELISA 对 Mφ 进行表型特征分析。为了分析治疗潜力，我们在雌性小鼠半横断 SCI 后将 IL-13 Mφ 注射到损伤周围区域。采用 Basso 小鼠步态评分和免疫组织化学评估功能恢复和组织病理学改善情况。采用不同的细胞活力测定法，在鼠和人神经母细胞瘤细胞系、人神经球以及鼠器官型脑片培养物中研究了 IL-13 的神经保护作用。
与用重组白细胞介素 13 预刺激的 Mφ 相比，在 SCI 后将 IL-13 Mφ 移植到损伤周围区域可促进小鼠的功能恢复。这种改善伴随着损伤体积减小和脱髓鞘面积减少。IL-13 Mφ 诱导的局部抗炎转变导致神经元死亡减少，轴突变性与 Mφ/小胶质细胞之间的接触减少，提示轴突回缩受到抑制。通过使用 IL-4Rα 缺陷型小鼠，我们证明了白细胞介素 13 信号通路对这些有益作用是必需的。虽然白细胞介素 13 对鼠和人神经母细胞瘤细胞系或人神经球培养物没有直接的神经保护作用，但白细胞介素 13 可挽救鼠器官型脑片免受细胞死亡，可能是通过间接调节 Mφ/小胶质细胞的反应。
综上所述，我们的数据表明，白细胞介素 13 诱导的抗炎 Mφ/小胶质细胞表型可以保护神经元组织并改善轴突回缩，从而促进 SCI 后的恢复。
