The interaction of mesenchymal stromal cells and activated B cells in the context of fibrosis-associated autoimmune diseases, under special consideration of systemic sclerosis and CREST syndrome

系统性硬化症(SSC)是一种罕见的自身免疫性疾病，属于胶原病。SSc的特征是皮肤和内脏的进行性纤维化，在一组患者中，还伴有钙化增加(冠脉综合征)。目前的药物可以延缓纤维化，但并不能真正阻止它。纤维化是SSc病死率的主要决定因素。因此，更好地了解SSc相关的纤维化对于改进治疗方案是至关重要的。活化的免疫细胞和基质细胞(如成纤维细胞)的双向串扰被认为是SSC和其他基质重塑自身免疫性疾病的病理生理学的中心机制。然而，到目前为止，这种相互作用还没有得到充分的研究。具体地说，B细胞在这一过程中的参与一直被认为只包括病理性自身抗体的产生，从而以直接或间接的方式支持纤维化。然而，一些线索表明，B细胞可以通过其他特性积极参与疾病，例如它们分泌细胞因子的能力。例如，患者接受B细胞去除治疗后SSC症状的改善并不一定与抗体效价的降低相平行。我们实验室的体外实验表明，人类B细胞可以通过分泌可溶性因子，如肿瘤坏死因子-α和白介素1，从非炎症环境中激活成纤维细胞。这些被激活的成纤维细胞增加了自身细胞因子的产生，包括IL-8，IL-6和转化生长因子，高达基线浓度的100倍。此外，我们对该项目的未发表的初步工作也揭示了B细胞可以调节多潜能间充质基质细胞(MSC)的功能，包括它们的分化能力。这些结果与其他观察一起，使我们提出假设，激活的B细胞也可能通过分泌细胞因子来促进SSC的发生和/或进展。这一假设的检验包括：1)在特殊考虑SSC特有的条件下，B细胞和真皮成纤维细胞(健康人和SSC病变)的双向相互作用的详细阐述。2)研究激活的B细胞在多大程度上影响成纤维细胞和MSC的分化，从而导致异常纤维化和钙化(冠状综合征)；3)分析成纤维细胞和MSC中B细胞介导的信号通路和潜在的干预选择；4)通过三维皮肤模型证实激活的B细胞对SSC相关纤维化的抗体非依赖性影响。我们的目的是更好地阐明B细胞作为SSC纤维化调节器的概念，SSC是一种自身免疫性疾病，几乎不了解，通常是侵袭性的，几乎没有治疗选择。

Systemic Sclerosis (SSc) is a rare autoimmune disease, belonging to the group of collagenoses. SSc is characterized by progressive fibrosis of skin and internal organs and - in a subgroup of patients- additionally by increased calcifications (CREST syndrome). Current medications can delay fibrosis, however not really stop it. Fibrosis is the main determinant for mortality in SSc. Therefore a better basic understanding of SSc-associated fibrosis is of utmost importance to improve treatment options. The bidirectional cross-talk of activated immune cells and stromal cells, such as fibroblasts is considered a central mechanism in pathophysiology of SSc and other matrix remodeling autoimmune diseases. However, so far this interaction has not been sufficiently investigated. Specifically the participation of B cells in this process has long been considered to merely encompass production of pathological auto-antibodies, thereby supporting fibrosis in a direct or indirect manner. However several hints indicate that B cells can actively take part in the disease by other properties, such as their ability to secrete cytokines. For example improvement of the SSc symptoms upon B cell depleting therapy in patients is not necessarily paralleled by a reduction of antibody titers. And in vitro experiments from our own lab demonstrate that human B cells can activate fibroblasts from a non-inflammatory environment via secretion of soluble factors such as TNF-alpha and IL-1ß. Such activated fibroblasts increase their own cytokine production, including IL-8, IL-6 and TGFß up to 100fold above baseline concentration.Moreover our unpublished preliminary work to this project also revealed that B cells can modulate functions of multipotent mesenchymal stromal cells (MSC), including their differentiation capacity.These results together with additional observations, led us to the hypothesis that activated B cells may also contribute to pathogenesis and/or progression of SSc via their secretion of cytokines.The testing of this hypothesis includes: 1) the detailed elaboration of the bidirectional interaction of B cells and dermal fibroblasts (of healthy individuals and SSc lesions) under special consideration of SSc-specific conditions. 2) the investigation in how far activated B cells influence the differentiation of fibroblasts and MSC, - thereby contributing to aberrant fibrosis and calcification (CREST-syndrome), 3) the analysis of the B cell- mediated signaling pathways in fibroblasts and MSC and potential options for intervention, 4) the confirmation for antibody-independent influence of activated B cells on SSc-associated fibrosis by means of a 3-dimensional skin model. Our aim is to better elucidate the concept of B cells as modulators of fibrosis in SSc, as an autoimmune disease that is hardly understood, often aggressive and with few therapeutic options.