Impact of Intestinal Motility, Mucosal Inflammation and Fecal Microflora on Transplant Intestine Function

Abstract

Background: Alterations in intestinal motility, fecal microflora and mucosal inflammatory microenvironment may impact allograft intestinal function. Methods: In a cross sectional study, stool samples, intestine biopsies were collected and gastrointestinal scintigraphy using a 6-hour modified gastric emptying test were performed prospectively in adult intestine/multivisceral transplant recipients with (n=10) and without (n=10) excessive diarrhea. Mucosal biopsies were stained for CD163+, CD4+ and CD8+ cells to assess mucosal cellular infiltration. Fecal microorganisms were characterized using shotgun paired-end metagenomic sequencing on the Illumina HiSeq platform. Fecal samples from 6 healthy controls were also compared. Results: Colonic transit time ranged from as short as 1 hour to >6 hours. Overall intestinal motility was within normal limits [1] in 14 (70%) patients, rapid in 5 (25%) patients [Figure 1] and slow in 1(5%) patient, with no correlation between intestinal motility and excessive diarrhea. There were no differences in the mucosal cellular infiltration between the two groups. Overall there were more macrophage infiltration than CD8+ and CD4+ T cells in the mucosal biopsies [Figure 2]. Taxonomic classification of the fecal microflora sequences revealed that, 7 bacterial taxa at the genus level were significantly different in the diarrhea group, including Veillonella (p-value < 0.001), Bifidobacterium (p-value < 0.02), Alistipes (p-value < 0.02), Enterococcus (p-value < 0.02), Odoribacter (p-value < 0.02), Streptococcus (p-value < 0.05), and Lactobacillus (p-value < 0.05) [Figure 3a]. The diversity measured by the Bray-Curtis dissimilarity for the microbial communities in the fecal samples from patients with diarrhea was significantly lower than that in the healthy control samples at the genus level (p-value < 0.05), although the difference between diarrhea and non-diarrhea samples was not statistically significant [Figure 3b]. Conclusions: Excessive diarrhea in intestine transplant recipients without rejection may be a result of less diverse fecal microflora, whereas intestinal motility and mucosal inflammation may not play a significant role. Manipulation of fecal microflora may be useful in controlling chronic diarrhea after intestine transplantation. A study with larger sample size may better define fecal microbial alterations in the setting of intestine transplantation.FigureFigureFigure