CXCL4抑制血管新生促进慢性放射性肠炎纤维化的机制研究

Angiopathy and interstitial fibrosis are major pathologic features of chronic radiation enteritis (CRE), but the mechanism of their interactions is unclear. It is known that vascular injury may initiate the fibrotic process in CRE, which is regulated by transforming growth factor β (TGF-β) and subsequent pathway. In previous studies, we have found significant microvascular damages in the tissue of CRE, as well as the imbalance between promoting and inhibiting signals for angiogenesis. Moreover, there is a persistent high expression of the angiostatic chemokine CXCL4, hypoxia-inducible factor 1α, and TGF-β in the tissue of CRE. As a result, we propose a scientific hypothesis that the persistent high expression of CXCL4 leads to inhibition of angiogenesis and subsequent hypoxia, and thereby aggravates the fibrosis of CRE. This project aims to confirm the correlation between CXCL4 expression and fibrosis in CRE, and to demonstrate the effect of CXCL4 on angiostasis, chronic hypoxia, and progressive fibrosis in CRE, using human tissue assessments and animal model experiments. Furthermore, the project plans to clarify the mechanism how CXCL4 inhibits angiogenesis in CRE, using primary cell culture and functional analysis in vitro. This project would be constructive to the revelation of underlying process of angiopathy and fibrosis in CRE. Its implementation will enrich the theoretic evidence in fibrosis of CRE and lighten a new path for future management.

血管病变与间质纤维化是慢性放射性肠炎（CRE）的主要病理特征，但两者之间的作用机制尚不清楚。已知血管损伤是CRE纤维化的始动因素，后者受TGF-β及下游信号通路调控。我们前期发现，CRE组织存在显著微血管病变，合并调控血管新生的促/抑信号失衡，起抑制血管新生作用的趋化因子CXCL4持续高表达，缺氧诱导因子HIF-1α与促纤维化因子TGF-β表达上调。由此，我们提出“CXCL4持续高表达导致血管新生受抑制，继发组织慢性缺氧，促进CRE纤维化”的科学假设。本课题拟通过人体组织检测和动物实验明确CXCL4表达水平与CRE中血管新生抑制、组织纤维化的相关性，验证CXCL4抑制血管新生、诱发缺氧机制并启动促纤维化通路的功能，并通过原代细胞培养和体外功能实验阐明CXCL4在CRE中抑制血管新生的具体分子机制。本课题将有助于深入认识CRE血管病变与纤维化发展的内在机制，为临床防治提供理论依据和新的思路。

血管病变与间质纤维化是慢性放射性肠炎（CRE）的主要病理特征，但两者之间的作用机制尚不清楚。已知血管损伤是CRE纤维化的始动因素，后者受TGF-β及下游信号通路调控。我们前期发现，CRE组织存在显著微血管病变，合并调控血管新生的促/抑信号失衡，起抑制血管新生作用的趋化因子CXCL4持续高表达，缺氧诱导因子HIF-1α与促纤维化因子TGF-β表达上调。由此我们提出“CXCL4持续高表达导致血管新生受抑制，继发组织慢性缺氧，促进CRE纤维化”的科学假设，项目基于此开展。我们通过构建可靠的CRE小鼠模型和细胞系开展实验，发现单一炎症因子CXCL4无法解释CRE纤维化中的血管新生抑制及纤维化进程。虽然趋化因子CXCL4在CRE组织中持续高表达，且与CRE组织血管新生状态、纤维化程度有关，但采用CXCR3B中和抗体或敲除CXCL4基因，无法延长CRE模型动物的生存或缓解CRE纤维化表现。由于CXCL4的受体CXCR3亦受NLRP3炎症小体通路调控，遂探索通过天然代谢产物3-羟基丁酸（3-HB）抑制NLRP3炎症小体通路改善CRE纤维化的现象与机制。我们首先验证了NLRP3炎症小体通路相关因子在CRE小鼠模型中表达增高，口服3-HB能够抑制NLRP3炎症小体的活化，且降低小鼠受照射肠段巨噬细胞浸润及相关炎症因子的表达。我们进一步确认，3-HB能够延长照射后小鼠生存时间，改善小鼠照射后体重下降及内镜表现，降低小鼠受照射肠段放射性损伤病理评分，并减轻肠壁纤维化程度。该研究结果为CRE的预防和治疗提供了新的思路和潜在方法。此外，我们通过临床病例分析发现CRE预后特点、病变特征、预测因素和治疗效果，宏观印证血管新生抑制和纤维化的病理机制，为从宏观大体表现到微观分子机制的探索提供价值的信息。