We describe methods for longitudinal monitoring of the efficacy of therapeutics for the treatment of colonic pathologies in mice using a rigid endoscope. This protocol can be readily used for the characterization of the therapeutic response of an individual tumor in live mice and also for monitoring potential disease relapse.
Animal models of inflammatory bowel disease (IBD) and colorectal cancer (CRC) have provided significant insight into the cell intrinsic and extrinsic mechanisms that contribute to the onset and progression of intestinal diseases. The identification of new molecules that promote these pathologies has led to a flurry of activity focused on the development of potential new therapies to inhibit their function. As a result, various pre-clinical mouse models with an intact immune system and stromal microenvironment are now heavily used. Here we describe three experimental protocols to test the efficacy of new therapeutics in pre-clinical models of (1) acute mucosal damage, (2) chronic colitis and/or colitis-associated colon cancer, and (3) sporadic colorectal cancer. We also outline procedures for serial endoscopic examination that can be used to document the therapeutic response of an individual tumor and to monitor the health of individual mice. These protocols provide complementary experimental platforms to test the effectiveness of therapeutic compounds shown to be well tolerated by mice.
结肠直肠癌(CRC)是恶性全世界1的4 个最常见的原因。尽管我们对这个疾病的家族基础上的理解显著的进步,遗传易感性不仅有助于对CRC的情况下2〜20%。其余都归因于大量的外在因素和环境因素,包括慢性炎症。在人类中,慢性炎症和结肠直肠癌之间的关联是溃疡性结肠炎(UC)的患者,谁具有显影结肠炎相关结肠癌(CAC)的更大的风险明显,取决于炎性疾病3的持续时间,程度和严重性-5。因此,新的治疗方法是在发展中,以控制的免疫反应和相关的生产的生长促进因子的炎症肿瘤微环境6-8。有适当的临床前动物模型中增加的需求来表征的治疗功效这些药物对发育和疾病的进展。
小鼠模型已经明确证实,炎性微环境有助于CRC进展,即使在没有明显的炎症9,10。这些模型包括使用多糖葡聚糖硫酸钠(DSS)的,在小鼠的饮用水提供到上皮损伤和急性和慢性炎性肠疾病(IBD)的11,12建模。虽然通过该DSS诱导粘膜损伤和结肠炎的机理还不完全清楚,一些研究表明,DSS抑制细胞的逆转录酶和核糖核酸酶活动的细胞内,或促进纳米脂质复合物,与结肠膜导致上皮损伤熔合形成13,14。修改标准DSS的模型还提供显著洞察由结肠上皮细胞维持组织稳态和单组机制晚黏膜免疫反应15。
氧化偶氮甲烷(AOM)的腹腔内给药单独,或与DSS的结合,提供了一个模式用于检查的体细胞突变之间的相互作用,在上皮粘膜和炎症和基质微环境16,17。 AOM是致癌物质1,2-二甲基肼(DMH)不直接导致DNA突变的代谢物。相反,AOM水解methylazoxymethanol(MAM)由细胞色素异构体CYP2E1在肝脏,在那里MAM缀合有葡糖醛酸,然后通过胆汁分泌物18输送到肠。据认为,该细菌β葡糖醛酸酶有助于MAM造成DNA烷基化的降解和突变的上皮细胞19的积累。大多数的AOM诱导的结肠肿瘤窝藏错义突变的基因中的编码β连环蛋白,渲染蛋白耐蛋白酶degradati上,这会导致经典Wnt信号通路20的异常活化。当AOM的活性是结合由DSS诱发的粘膜损伤,随后的伤口愈合反应创建一个微环境有利于的诱变上皮的生长和扩增。在此模型中的一个变型中,AOM的单独一段数周重复给药可用于模拟散发性结直肠癌,在没有DSS诱导的结肠炎的10,17。这两种模式的免费提供实验设置分别进行研究的CAC和零星的CRC,这两者都与一个促炎症肿瘤微环境10相关联。
利用小鼠序列内窥镜是由贝克尔和他的同事21首创,并允许结肠炎和肿瘤进展的纵向监测。在这里,我们提供了三个临床前的协议的基础上DSS诱发的粘膜损伤和/或AOM介导的涂铁道部感应可重复诱导特异性结肠病变。第一个协议描述诱发急性胃黏膜损伤响应DSS管理引发许多与IBD相关的病理特点。所述第二协议是基于DSS给药三个连续的周期,以模仿炎症在IBD患者中观察到的耀斑,并且可以进行结合AOM诱导突变。最终的协议是基于AOM诱导零星上皮突变。对于每一个这些协议中,我们在相关标准程序展开以包括我们已经开发并监控的新药物的疗效的预防和治疗性干预的方法。
The three protocols that are described outline methods of reliable and reproducible induction of colonic disease pathology in mice. When combined with routine endoscopic monitoring and the intervention strategies outlined here, these protocols will provide powerful pre-clinical insight into the efficacy of therapeutics. Our laboratories routinely use all of these protocols to monitor the success of novel therapeutics10,23,24.
There are a number of considerations when choosing a pre-clinical animal model to test new therapeutics. These include relevance of the model to the human disease, and the contribution of the tumor microenvironment to the proposed action of the therapeutic target. Here we provide three protocols for therapeutic intervention in established intestinal disease models. These models are reproducible and the delivery of reagents to induce disease is easy to manage. Importantly, the models are highly relevant to multiple facets and stages of colitis onset, and of tumor initiation and progression. Researchers should take into consideration the genetic background of the mouse strains used when designing experiments, as the susceptibility to disease induced by DSS and/or AOM can vary considerably25. In addition, different microbial communities may have different metabolic capacities in the context of AOM, which is metabolized by bacteria. We caution against using different cohorts of mice that were born into different animal facilities (including commercial vendors) in a single experiment. Similarly, the different microflora in mice used from different facilities may elicit different host responses to DSS-induced epithelial barrier damage11. Moreover, the appropriate analysis of tissue (for example RNA purification) should also be considered, since the ability of DSS to inhibit reverse transcriptase will impact on subsequent molecular analysis26,27.
Mouse endoscopy is a cutting edge technique to repeatedly monitor disease onset and progression in an individual mouse. The ability to record videos and extract still images permits easy monitoring of multiple disease parameters and tumors. In addition to improving animal welfare, endoscopic monitoring also reduces the need for multiple cohorts of experimental mice, which traditionally were culled at different time-points to track disease outcome. The MEICS scoring system is not a substitute for histopathological analysis, but provides an alternative means to monitor animal health and mucosal damage in live mice. Mouse endoscopy is a specialized laboratory technique, and all procedures should be performed by trained personnel to ensure appropriate manipulation and handling of the mice, as well as to provide consistent quality in the images used for disease scoring. In the hands of qualified personal, we have found that endoscopy induces little or no damage to the tumors that would cause intra-tumoral bleeding. For the therapeutic protocols outlined, we consider endoscopy highly advantageous, since it provides a way to determine the initial tumor burden, and allows us to group cohorts of animals with similar tumor burdens prior to the administration of a therapeutic drug. Sequential monitoring of the mice enables researchers to determine the efficacy of novel therapies early on, with the option of terminating unsuccessful experiments in a timely manner.
As our understanding of inflammatory bowel disease and colorectal cancers advance, new targets for therapy will be identified. Appropriate animal models will be integral to ensuring that the most promising new therapies are moved towards clinical trials.
The authors have nothing to disclose.
We would like to thank CSL Ltd. for supporting the purchase of the endoscopy equipment. The research in the laboratory of ME is supported by the Ludwig Institute for Cancer Research, and the laboratories of TP and ME are supported by the Victorian State Government Operational Infrastructure Support and the National Health and Medical Research Council of Australia. ME is an NHMRC Senior Research Fellow.
Name of Material/ Equipment | Company | Catalog Number | Comments/Description |
Dextran Sulfate Sodium (MW 36,000-50,000) | MP Biochemicals | 160110 | Requires batch testing. |
Azoxymethane | Sigma | A5486-100MG | Requires batch testing. |
Vanilla Protein Shake | N/A | N/A | Available from hospital pharmacies. |
Isoflourane | PPC | M60303 | This is a restricted reagent, which should be stored under lock and key. |
70% Ethanol | N/A | N/A | Standard lab reagent. |
Coloview miniendoscopic system | |||
Endovision Tricam | Karl Storz | 20212001-020 | |
Xenon 175 light source with anti-fog pump | Karl Storz | 20134001 | |
HOPKINS straight Forward Telescope | Karl Storz | 64301AA | |
Endoscopic Sheath (total diameter 3 mm) | Kalr Stroz | 61029C | |
Fubre Optic Light Cable | Kalr Stroz | 69495ND | |
Computer and media player software | MAC, imovies | ||
Scale | Any | Any scale suitable for weighing mice. |