Paneth cells promote angiogenesis and regulate portal hypertension in response to microbial signals.

Paneth cells (PCs) synthesize and secrete antimicrobial peptides that are key mediators of host-microbe interactions establishing a balance between intestinal microflora and enteric pathogens. We observed that their number increases in experimental portal hypertension and aimed to investigate the mechanisms by which these cells can contribute to the regulation of portal pressure.We first treated Math1Lox/LoxVillcreERT2mice with tamoxifen to induce the complete depletion of intestinal PCs. Subsequently, we performed partial portal vein or bile duct ligation. We then studied the effects of these interventions on hemodynamic parameters, proliferation of blood vessels and the expression of genes regulating angiogenesis. Intestinal organoids were cultured and exposed to different microbial-derived products to study the composition of their secreted products by proteomics and their effects on the proliferation and tube formation of endothelial cells (ECs). In vivo confocal laser endomicroscopy was used to confirm the findings on blood vessel proliferation.Portal hypertension was significantly attenuated in PC-depleted mice compared to control mice and was associated with a decrease in portosystemic shunts. Depletion of PCs also resulted in a significantly decreased density of blood vessels in the intestinal wall and mesentery. Furthermore, we assessed the expression of intestinal genes regulating angiogenesis in Paneth cell depleted mice using arrays and next generation sequencing. Tube formation and wound healing responses were significantly decreased in ECs treated with conditioned media from PC-depleted intestinal organoids exposed to intestinal microbial-derived products. Proteomic analysis of conditioned media in the presence of PCs revealed an increase in factors regulating angiogenesis and additional metabolic processes. In vivo endomicroscopy showed decreased vascular proliferation in absence of PCs.The in vivo and in vitro results presented here suggest that intestinal flora and microbial-derived factors positively regulate PCs to secrete not only antimicrobial peptides, but also pro-angiogenic signalling molecules, thereby promoting intestinal and mesenteric angiogenesis and regulating portal hypertension.

Click here to read the full article @ Journal of Hepatology