成骨细胞BMP信号通路参与SLE患者造血损伤的机制研究

The treatment of systemic lupus erythematosus (SLE) patients with pancytopenia is extremely challenging. Loss of support for hematopoietic stem cells (HSCs) by marrow stromal cells is believed to be one of the mechanisms for impaired hematopoiesis in SLE patients. It has been shown that BMP signaling of osteoblasts (OB) in bone marrow regulates the adhesion of HSCs to osteoblasts and also hematostasis via N-cadherin. We previously found that BMP signaling in OB of SLE patients was suppressed, and the level of N-cadherin expression by OB was higher than control. Moreover, osteoblastic differentiation of bone marrow-derived mesenchymal stem cells from SLE patients was inhibited and there were more immature hematological cells detained in bone marrow as well. Up-regulation of BMP signaling resulted in decreased N-cadherin expression on OB and improved blood cells counts in SLE mice model. Based on those findings, we proposed that BMP signaling of OB is involved in the development of pancytopenia in SLE, and down-regulation of BMP signaling in OB may result in abnormal adhesion of HSC to OB and impaired hematopoiesis. To clarify this hypothesis, we intended to explore how BMP signaling of OB regulate N-cadherin expression on OB, and also how BMP signaling of OB regulation HSC adhesion to OB and hematopoiesis. We expect that it will give us a deep insight on the mechanism why pancytopenia and impaired hematopoiesis occur in SLE, and it will also clarify the role of BMP signaling of OB in dysregulated hematopoieis. By achieving those aims, we will have a better understanding in the etiology of pancytopenia in SLE and possibly find novel target for the treatment of SLE with pancytopenia.

伴有全血细胞减少的系统性红斑狼疮(SLE)患者，目前临床缺乏有效治疗方法。SLE患者骨髓基质受损，不能有效支持造血干细胞(HSC)是其机制之一。研究显示，骨髓中成骨细胞(OB)可调控HSC功能，其BMP信号通路可调节OB的N-cadherin表达，介导HSC粘附和调节造血。我们前期研究发现，SLE骨髓OB的BMP信号通路受抑制，N-cadherin表达增加，骨髓间充质干细胞成骨分化减弱并伴有骨髓幼稚血细胞潴留；上调BMP通路后OB的N-cadherin表达下降，狼疮鼠骨髓幼稚血细胞潴留减少，外周血细胞数目增加。故提出以下假设：SLE OB的BMPs信号通路异常，通过影响N-cadherin表达，导致HSC与OB的粘附和造血异常，参与了SLE的全血细胞减少发生。本课题拟研究OB的BMP信号通路对HSC与OB的粘附和骨髓血液生成的影响，为SLE全血细胞减少提供新的理论依据，为治疗提供新的靶点。

系统性红斑狼疮(Systemic lupus erythematosus, SLE)是一种累及多脏器、多组织的自身免疫疾病，患者体内存在大量自身抗体、造成心、肝、肺、肾等多个脏器的损伤。血液系统是狼疮常累及系统之一，其治疗以糖皮质激素和免疫抑制剂为主，但仍有部分严重的患者虽经大剂量糖皮质激素和免疫抑制冲击治疗，全血细胞仍进行性下降，病人死于严重的出血或感染。因此寻找更加有效的治疗方法是目前治疗SLE严重的血液系统损伤的迫切需要。. 骨髓是成人造血干细胞(HSCs)定植的主要场所，近年来有研究表面SLE患者HSCs存在多种异常。本研究立足于研究HSCs所处的骨髓微环境中成骨细胞(OB)对其分化的影响。我们1、研究了MRL/lpr狼疮鼠和SLE患者外周血、骨髓和/或脾脏的红系、粒系及髓系的分布情况。2、分离狼疮鼠和患者骨髓间充质干细胞(BMMSCs)，在体外诱导分化成OB，研究其对HSC分化的影响。3、比较狼疮鼠与C57鼠OB N-cadherin 表达，并干扰狼疮BMMSCs N-cadherin的,观察其对HSCs B系分化的影响。4、探讨炎症因子TNF-α、BMP信号通路对N-cadherin的调控的机制。5、用正常及下调N-cadherin的BMMSCs输注MRL/lpr狼疮鼠，观察狼疮鼠血液系统的损伤恢复情况。.课题组研究结果显示：1、，狼疮患者和MRL/lp狼疮鼠共性为外周血的细胞减少；外周血、骨髓及脾脏总B淋巴细胞减少，浆细胞比例增加。2、狼疮HSCs本身存在向B系祖细胞分化的障碍。3、狼疮OB N-cadherin高于正常，其负向调控 BMMSC成骨分化，通过抑制成骨增加HSCs向B祖细胞分化 4、狼疮OB 高表达的N-cadherin与狼疮骨髓浆细胞增高有关。5、BMP-2 处理狼疮鼠BMMSCs 后N-cadherin 的水平下降，而在Noggin 处理后N-cadherin 表达则上调，BMP信号通路可能参与OB N-cadherin的调控；TNF-α对N-cadherin的表达水平有影响，可能与ERK1/2通路有关。6、BMMSCs输注可降低外骨髓脾脏的浆细胞比例，改善外周血小板数量。.本研究阐明狼疮骨髓微环境中OB N-cadherin异常参与B淋巴细胞异常的机制，为治疗难治性狼疮提供新的思路和理论依据。