Prox1-Dependent Stimulation of Lymphatic Function Ameliorates Mesenteric Lesions and Modifies the Composition of Microbiota in Experimental Crohn's Disease

Abstract

Background: Prox1 is a transcription factor necessary for lymphatic function. The main aim of the current study was to investigate the potential role of Prox1 in lymphangiogenesis and lymphatic function, and analyze Prox1-dependent stimulation of lymphatic function on mesenteric lesions and the composition of microbiota in Crohn’s disease. Methods: Prox1flox/+, Tie2-CreERT2 and IL-10 KO mice were included. Disease activity and enterocolitis inflammation were assessed using a grading system. Lymphatic vessel density and lymphatic function were analyzed using immunohistochemistry and lymphangiography. The potential mechanism of Prox1 was analyzed. The effects of lymphatic function on mesenteric adipose tissue (MAT) and the composition of microbiota were evaluated. Results: Systemic delivery of AAV-Prox1 reduced disease activity index and the severity of chronic inflammation in IL-10 KO mice. Without compensatory response of Prox1, IL-10 KO+Prox1 KO mice developed serious inflammation in the colon. For lymphatic vessel, IL-10 KO+Prox1 KO mice showed lower lymphatic vessel density and less functional lymphatic vessels. IL-10 KO+AAV-Prox1 mice showed significantly increased lymphatic vessel density. Delivery of AAV-Prox1 also promoted lymphatic drainage function. The Prox1/VEGFC/VEGFR3 pathway played an important role in lymphangiogenesis and lymphatic function. Additionally, Prox1-dependent stimulation of lymphatic function ameliorated hypertrophy of MAT in IL-10 KO mice. Delivery of AAV-Prox1 also modified the composition of microbiota, the proportion of Firmicutes increased and Bacteroidetes decreased in IL-10 KO+AAV-Prox1 mice compared with IL-10 KO mice. An increase in the diversity of gut microbiota in IL-10 KO+ AAV-Prox1 mice was observed. Conclusions: Our findings demonstrated that Prox1 played the critical role in the lymphangiogenesis and lymphatic function. Additionally, Prox1-dependent stimulation of lymphatic function could ameliorate hypertrophy of MAT and modify the composition of microbiota in experimental Crohn’s disease. Funding Statement: This work was partly supported by National Natural Science Foundation of China (Grant 81670471, 81770556 and 81570500). Declaration of Interests: The authors declare that they have no conflicts of interests. Ethics Approval Statement: All animal protocols were approved by the Institutional Ethics Committee of the Jinling Hospital, Medical School of Nanjing University, Nanjing, China.