华勒氏变性早期IL-1β对雪旺细胞去分化的影响及其机制

The ultimate goal of regenerative medicine research is to enable replacement of lost or damaged tissues or organs. Regeneration can potentially be accomplished using the processes of de-differentiation, trans-differentiation or reprogramming. Humans have a limited capacity to regenerate tissues or organs, including liver and the peripheral nervous system (PNS). In some cases, the process of regeneration involves de-differentiation of mature cells. De-differentiation is a mechanism in which terminally-differentiated cells revert to a less-differentiated stage within the same lineage and allows cells to proliferate before re-differentiating, leading to the replacement of lost cells..Schwann cells (SCs), myelinated glial cells of the PNS, de-differentiate and revert to an immature phenotype in Wallerian degeneration (WD) following nerve injury and, by doing so, can actively promote nerve repair and functional recovery. Following de-differentiation, SCs contribute to macrophage-mediated myelin removal and re-enter the cell cycle, proliferate, and then form bands of Büngner, which support and direct outgrowing axons to sites of innervation. Moreover, these cells express and secrete axonal growth promoting factors, then re-differentiate and myelinate regenerated axons, which eventually leads to substantial functional recovery. This sequence emphasizes the central function of SC de-differentiation in PNS regeneration..WD can be considered an innate-immune response of the PNS to traumatic nerve injury. PNS injury induces immune and non-immune cells to produce cytokines and develop an efficient cytokine network during WD. Before macrophage recruitment, injured PNS product IL-1β and other inflammatory cytokines. IL-1β induces macrophage recruitment and then aids myelin clearance, which facilitates axonal outgrowth. In addition to a role in immune responses, IL-1β direct and indirect promotes neuronal survival. Moreover IL-1β promotes SCs proliferation and increases nerve growth factor synthesis by SCs. Previous in vivo studies indicate that these effects of IL-1β on WD are supposed to provide sciatic nerve regeneration. These suggest that IL-1β plays an important role during PNS regeneration. On top of that, IL-1β can influence de-differentiation in some types of terminally differentiated cells. For example, IL-1β induces chondrocyte de-differentiation. However, whether IL-1β promotes SCs de-differentiation during WD remains to be clearly determined. To demonstrate hypothesis that, in addition to a role in immune responses, IL-1β participates in SC de-differentiation, proliferation and apoptosis, and promotes regeneration of PNS, we used a rodent in vitro & vivo model investigate effect and mechanism of IL-1β on schwann cells dedifferentiation at early phase of Wallerian Degeneration.

成体细胞通过去分化、转分化及重编程获得分化潜能是再生医学研究热点之一。在神经再生过程中，“华勒氏变性”及“雪旺细胞去分化”都是其至关重要的环节。IL-1β是华勒氏变性早期的重要参与因素之一，具有促进神经元的存活，神经突生长等多种生物活性，而IL-1β对雪旺细胞去分化作用却鲜有报道。在前期实验研究中，我们通过大鼠坐骨神经华勒氏变性体外模型，发现华勒氏变性早期IL-1β具有通过c-Jun/AP-1通路促进雪旺细胞去分化的作用（详见预实验研究）。本课题将构建坐骨神经华勒氏变性体外模型以及坐骨神经损动物模型，进一步研究IL-1β在周围神经华勒氏变性早期对雪旺细胞去分化的影响，阐明IL-1β对雪旺细胞去分化关键通路c-Jun/AP-1的作用，并探索调控机制，为解决神经损伤修复再生过程中“新生组织的细胞来源”问题提供新的理论依据。

成体细胞通过去分化、转分化及重编程获得分化潜能是再生医学研究热点之一。在神经再生过程中，“华勒氏变性”及“雪旺细胞去分化”都是其至关重要的环节。IL-1β是华勒氏变性早期的重要参与因素之一，具有促进神经元的存活，神经突生长等多种生物活性，而IL-1β对雪旺细胞去分化作用却鲜有报道。项目通过改进后的大鼠坐骨神经体外华勒氏变性模型，进一步确认该模型的可靠性，并以该模型为基础，研究表明体外华勒氏变性模型是研究周围神经系统华勒氏变性过程中干预雪旺细胞去分化影响因素的有效模型。通过该模型，我们研究进一步证实华勒氏变性早期雪旺细胞IL-1β mRNA表达量升高，IL-1β蛋白分泌量增多，华勒氏变性可视为外周神经系统应对神经损伤的固有免疫反应。通过该模型给予相应干预，我们研究发现适当浓度的IL-1β具有促进华勒氏变性过程中雪旺细胞去分化的作用，以及促进华勒氏变性过程中雪旺细胞清除髓鞘碎片，从而促进周围神经再生，而过高浓度的IL-1β对华勒氏变性过程中雪旺细胞去分化以及髓鞘碎片的清除并无促进作用。本研究证实华勒氏变性早期适当浓度的IL-1β具有促进雪旺细胞转录因子c-Jun mRNA表达量，以及促进雪旺细胞的细胞核内转录因子c-Jun的高表达，并促进雪旺细胞内AP-1活化；并认为华勒氏变性早期IL-1β通过c-Jun/AP-1通路促进雪旺细胞去分化，以及促进雪旺细胞清除髓鞘碎片，从而促进周围神经再生。本研究证实华勒氏变性早期适当浓度的 IL-1β 具有促进雪旺细胞增殖，以及增加 Bcl-2 表达量，减低 Bax 表达量，升高 Bcl-2/Bax 比值，抑制雪旺细胞凋亡的积极作用；并认为 IL-1β 通过促进 c-Jun/AP-1 通路活化促进雪旺细胞增殖，通过 Bcl-2/Bax 通路抑制雪旺细胞凋亡。本项目研究为解决神经损伤修复再生过程中“新生组织的细胞来源”问题提供新的理论依据。