Thrombospondin-1 Type 1 Repeats in a Model of Inflammatory Bowel Disease: Transcript Profile and Therapeutic Effects

Thrombospondin-1 (TSP-1) is a matricellular protein with regulatory functions in inflammation and cancer. The type 1 repeats (TSR) domains of TSP-1 have been shown to interact with a wide range of proteins that result in the anti-angiogenic and anti-tumor properties of TSP-1. To ascertain possible functions and evaluate potential therapeutic effects of TSRs in inflammatory bowel disease, we conducted clinical, histological and microarray analyses on a mouse model of induced colitis. We used dextran sulfate sodium (DSS) to induce colitis in wild-type (WT) mice for 7 days. Simultaneously, mice were injected with either saline or one form of TSP-1 derived recombinant proteins, containing either (1) the three type 1 repeats of the TSP-1 (3TSR), (2) the second type 1 repeat (TSR2), or (3) TSR2 with the RFK sequence (TSR2+RFK). Total RNA isolated from the mice colons were processed and hybridized to mouse arrays. Array data were validated by real-time qPCR and immunohistochemistry. Histological and disease indices reveal that the mice treated with the TSRs show different patterns of leukocytic infiltration and that 3TSR treatment was the most effective in decreasing inflammation in DSS-induced colitis. Transcriptional profiling revealed differentially expressed (DE) genes, with the 3TSR-treated mice showing the least deviation from the WT-water controls. In conclusion, this study shows that 3TSR treatment is effective in attenuating the inflammatory response to DSS injury. In addition, the transcriptomics work unveils novel genetic data that suggest beneficial application of the TSR domains in inflammatory bowel disease.血小板反应蛋白1 (Thrombospondin-1, TSP-1)是一种基质细胞蛋白，在炎症与癌症进程中发挥调控功能。TSP-1的1型重复序列 (type 1 repeats, TSR)结构域已被证实可与多种蛋白质结合，从而赋予TSP-1抗血管生成与抗肿瘤的特性。为明确TSR在炎症性肠病中的潜在功能并评估其治疗潜力，本研究针对诱导性结肠炎小鼠模型开展了临床、组织学及微阵列分析。我们采用葡聚糖硫酸钠 (dextran sulfate sodium, DSS)对野生型 (wild-type, WT)小鼠诱导结肠炎，造模周期为7天。同时，对小鼠分别注射生理盐水，或三种重组TSP-1衍生蛋白中的一种：① 包含TSP-1三个1型重复序列的蛋白 (3TSR)，② 仅包含第二个1型重复序列的蛋白 (TSR2)，③ 携带有RFK序列的TSR2蛋白 (TSR2+RFK)。从小鼠结肠中分离得到的总RNA经处理后，与小鼠基因芯片进行杂交。芯片数据通过实时定量聚合酶链反应 (real-time quantitative PCR, qPCR)与免疫组织化学实验进行了验证。组织学与疾病评分结果显示，经TSR类蛋白处理的小鼠其白细胞浸润模式存在差异，且3TSR处理组在减轻DSS诱导结肠炎的炎症反应方面效果最为显著。转录组分析结果显示存在差异表达 (differentially expressed, DE)基因，其中3TSR处理组小鼠与野生型生理盐水对照组的基因表达差异最小。综上，本研究证实3TSR处理可有效减轻DSS诱导损伤引发的炎症反应。此外，本研究的转录组学分析揭示了全新的遗传学数据，提示TSR结构域在炎症性肠病治疗中具有潜在应用价值。