Intestinal organoids model human responses to infection by commensal and Shiga toxin producing <i>Escherichia coli</i>

Infection with Shiga toxin (Stx) producing Escherichia coli O157:H7 can cause the potentially fatal complication hemolytic uremic syndrome, and currently only supportive therapy is available. Lack of suitable animal models has hindered study of this disease. Induced human intestinal organoids (iHIOs), generated by in vitro differentiation of pluripotent stem cells, represent differentiated human intestinal tissue. We show that iHIOs with addition of human neutrophils can model E. coli intestinal infection and innate cellular responses. Commensal and O157:H7 introduced into the iHIO lumen replicated rapidly achieving high numbers. Commensal E. coli did not cause damage, and were completely contained within the lumen, suggesting defenses, such as mucus production, can constrain non-pathogenic strains. Some O157:H7 initially co-localized with cellular actin. Loss of actin and epithelial integrity was observed after 4 hours. O157:H7 grew as filaments, consistent with activation of the bacterial SOS stress response. SOS is induced by reactive oxygen species (ROS), and O157:H7 infection increased ROS production. Transcriptional profiling (RNAseq) demonstrated that both commensal and O157:H7 upregulated genes associated with gastrointestinal maturation, while infection with O157:H7 upregulated inflammatory responses, including interleukin 8 (IL-8). IL-8 is associated with neutrophil recruitment, and infection with O157:H7 resulted in recruitment of human neutrophils into the iHIO tissue.产志贺毒素（Shiga toxin, Stx）的大肠杆菌O157:H7感染可引发潜在致命的溶血性尿毒症综合征并发症，目前仅可采用支持疗法。缺乏合适的动物模型阻碍了该疾病的相关研究。由多能干细胞体外分化获得的诱导型人类肠道类器官（induced human intestinal organoids, iHIOs）可模拟分化后的人类肠道组织。本研究证实，加入人类中性粒细胞的iHIOs可用于建模大肠杆菌肠道感染及先天细胞应答反应。将共生大肠杆菌与O157:H7导入iHIO管腔后，二者均可快速增殖并达到较高载量。共生大肠杆菌未造成组织损伤，且完全被限制在管腔内，这提示肠道黏液产生等防御机制可约束非致病性菌株。部分O157:H7最初与细胞肌动蛋白共定位；感染4小时后，可观察到肌动蛋白丢失及上皮完整性受损。O157:H7会以丝状形式增殖，这与细菌SOS应激反应的激活相一致。SOS反应可由活性氧（reactive oxygen species, ROS）诱导，而O157:H7感染会增加ROS的产生。转录组测序（RNAseq）分析显示，共生大肠杆菌与O157:H7均可上调与胃肠道成熟相关的基因；而O157:H7感染则会激活炎症应答，包括白细胞介素8（interleukin 8, IL-8）的表达上调。IL-8与中性粒细胞招募相关，O157:H7感染可促使人类中性粒细胞向iHIO组织内迁移。