Mutual amplification of Hedgehog and Activator Protein 1 (AP1)-signaling in Systemic Sclerosis - potential therapeutic and prognostic implications

系统性硬化症（SSc）等纤维化疾病的特点是发病率和死亡率高，在西方文明中占死亡人数的45%。由于缺乏有效的治疗选择，对纤维化疾病患者的管理受到限制。此外，虽然疾病进展的危险因素在人群水平上已经有了特征，但个体的病程和疾病进展的风险很难预测。活化的成纤维细胞，即肌成纤维细胞，是纤维化疾病的关键效应细胞。尽管AP/1信号通路和Hedgehog信号通路等促纤维化信号通路已被确定在SSc等纤维化疾病中发挥关键作用，但由于其广泛的细胞功能，特别是在SSc等慢性疾病的长期抑制设置中，对其中枢介质的深度抑制受到了副作用的限制。协同疗法的组合可以提供一种减少单个药物剂量的方法，从而降低毒性，但可以媲美甚至提高疗效。本研究的初步结果为纤维化疾病中AP1-和Hedgehog信号的虚拟扩增提供了第一个证据，这些扩增可能在成纤维细胞异常激活和进行性纤维化组织重塑中发挥核心作用。我们发现，与健康成纤维细胞相比，cJUN和GLI2在SSc成纤维细胞中同时过表达，并相互正向调节。抑制cJUN可降低刺猬诱导的成纤维细胞活化和组织纤维化，联合抑制cJUN/AP1信号和GLI2/hedgehog信号在体内显示出附加的抗纤维化作用。根据目前的应用，我们的目标是进一步表征cJUN/AP1信号和GLI2/Hedgehog信号的联合抑制作为纤维化疾病的潜在治疗策略：我们将分析介导cJUN/AP1-和GLI2/Hedgehog信号联合抑制的附加抗纤维化作用的中心下游机制。我们计划在临床前小鼠模型中进一步评估cJUN/AP1信号和GLI2/Hedgehog信号联合抑制的效果，这进一步反映了SSc的纤维化器官表现和病理生理方面：拓扑异构酶I模型诱导皮肤和肺纤维化。我们的目的是分析cJUN和GLI2在SSc皮肤中的上调是否对个体患者的病程具有预后意义。

Fibrosing disorders such as Systemic Sclerosis (SSc) are characterized by a high morbidity and mortality and contribute to up to 45% of deaths in Western civilizations. The management of patients with fibrosing disorders is limited by the paucity of effective treatment options. Moreover, the individual disease course and risk of disease progression is hard to predict although risk factors for disease progression have been characterized on the population level. Activated fibroblasts, so-called myofibroblasts, are key effector cells in fibrotic diseases. Although profibrotic signaling pathways such AP/1 signaling and Hedgehog signaling have been identified to play a key role in fibrosing disorders such as SSc, the profound inhibition of their central mediators limited by concerns about side effects due to their broad cellular functions in particular in the setting of longterm-inhibition in a chronic disorder such as SSc. Combinations of synergistic therapies could offer a way to reduce the doses of individual drugs, resulting in reduced toxicity, but comparable or even improved efficacy. Our preliminary results for this study provide first evidence for the virtual amplification of AP1- and Hedgehog signaling in fibrotic diseases that might play a central role for aberrant fibroblast activation and progressive fibrotic tissue remodeling. We show that cJUN and GLI2 are simultaneously overexpressed in SSc fibroblasts compared to healthy fibroblasts and positively regulate each other. Inhibition of cJUN reduces Hedgehog-induced fibroblast activation and tissue fibrosis and the combined inhibition of cJUN/AP1 signaling and GLI2/hedgehog signaling shows additive anti-fibrotic effects in vivo. With the current application, we aim to further characterize the combined inhibition of cJUN/AP1-signaling and GLI2/Hedgehog signaling as potential therapeutic strategy in fibrosing disorders: We will analyze the central downstream mechanisms that mediate the additive anti-fibrotic effects of the combined inhibition of cJUN/AP1- and GLI2/Hedgehog signaling. We aim to investigate the effects of the combined inhibition of both pathways in an in vitro clinical trial using precision cut tissue slices and in a humanized three dimensional-skin model We plan to further evaluate the effects of the combined inhibition of cJUN/AP1 signaling and GLI2/Hedgehog signaling in a preclinical mouse model, that reflects further fibrotic organ manifestations and pathophysiological aspects of SSc: the model of Topoisomerase I induced skin and lung fibrosis. We aim to analyze whether the upregulation of cJUN and GLI2 in SSc skin has prognostic implications for the disease course in individual patients.