Human milk oligosaccharides impact cellular and inflammatory gene expression and immune response

Authors: ROSA, FERNANDA - Arkansas Children'S Nutrition Research Center (ACNC); SHARMA, ASHOK - Cedars-Sinai Medical Center; GURUNG, MANOJ - Arkansas Children'S Nutrition Research Center (ACNC); CASERO, DAVID - Cedars-Sinai Medical Center; MATAZEL, KATELIN - Arkansas Children'S Nutrition Research Center (ACNC); BODE, LARS - University Of California, San Diego; SIMECKA, CHRISTY - University Arkansas For Medical Sciences (UAMS); ELOLIMY, AHMED - Arkansas Children'S Nutrition Research Center (ACNC); TRIPP, PATRICIA - Arkansas Children'S Nutrition Research Center (ACNC); RANDOLPH, CHRISTOPHER - Arkansas Children'S Hospital; HAND, TIMOTHY - University Of Pittsburgh School Of Medicine; WILLIAMS, KEITH - University Arkansas For Medical Sciences (UAMS); LEROITH, TANYA - Virginia Polytechnic Institution & State University; FOX, RENEE - Arkansas Children'S Nutrition Research Center (ACNC); Yeruva, Laxmi

Submitted to: Frontiers in Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2022
Publication Date: 6/29/2022
Citation: Rosa, F., Sharma, A.K., Gurung, M., Casero, D., Matazel, K., Bode, L., Simecka, C., Elolimy, A.A., Tripp, P., Randolph, C., Hand, T.W., Williams, K.D., Leroith, T., Fox, R., Yeruva, V. 2022. Human milk oligosaccharides impact cellular and inflammatory gene expression and immune response. Frontiers in Immunology. https://doi.org/10.3389/fimmu.2022.907529.
DOI: https://doi.org/10.3389/fimmu.2022.907529

Interpretive Summary: Human milk contains several bioactives that support infant growth and development. Human milk oligosaccharides (HMOs) are the third most abundant bioactive component present in human milk. HMOs have been shown to change intestinal microbiota (i.e., gut milieu) composition, and prevent pathogenic bacteria binding to the gut by serving as decoy receptors. However, the direct effect of HMOs in the absence of the gut microbiota on intestinal function and immunity remains to be elucidated. To address this knowledge gap, we used a germ-free mouse model, measured gut and immune system outcomes. Gut epithelial layer length (i.e., villi and crypt) was reduced in HMOs treated group in comparison to controls. In addition, in the small intestine, HMOs treated mice showed gene changes involved in the transport and absorption of nutrients relative to controls. HMOs also up-regulated genes involved in the mucus layer and enzymes in the large intestine. Furthermore, immune cell composition data from lymphoid tissues in the gastrointestinal tract (i.e., mesenteric lymph nodes) and spleen indicated increased anti-inflammatory and antigen-presenting cells (i.e., T regulatory, dendritic and type 2 innate lymphoid cells) and decreased inflammatory immune cells (i.e., macrophages, Th17) in HMOs treated group. These data demonstrate that HMOs have a direct effect on the gastrointestinal tract metabolism and immune system even in the absence of host microbiota.

Technical Abstract: Human milk harbors complex carbohydrates such as human milk oligosaccharides (HMOs), which are the third most abundant component after lactose and lipids. HMOs have been shown to impact intestinal microbiota, modulate the intestinal immune response, and prevent pathogenic bacteria binding to the gut by serving as decoy receptors. However, the direct effect of HMOs in the absence of the gut microbiota on intestinal function and immunity remains to be elucidated. To address this knowledge gap, we used 21-day old germ-free mice (C57BI/6) (n=10/group) that were housed in sterile flexible film isolators with ad libitum access to sterilized food and water. Mice were orally gavaged with 15mg/day of pooled-HMOs for 7 or 14 days and euthanized at day 28 or 35. A set of mice were maintained until day 50 to determine the persistent effects of HMOs. Control groups were maintained in the isolators for 28, 35, or 50 days of age. At the respective endpoints, small (SI) and large (LI) intestinal tissues were subjected to histomorphometric, transcriptome and flow cytomtry analysis. Small intestinal crypt was reduced after HMO treatment relative to control at day 28 and 35. While SI villus height and LI gland depth were decreased in the HMO treated mice relative to the control at day 35. We report significant HMO-induced and location-specific gene expression changes in host intestinal tissues. Differential expression analysis in the HMO group vs control revealed genes involved in the transport, absorption, and secretion (i.e., defensins, REG3A, FABP6) in the SI tissue. In the LI, HMOs treatment significantly up-regulated genes involved in the mucus layer and enzymes (i.e., FUT2). In addtion, Tregs, ILC-2's and dendritic cells were increased while macrophages, Th17 and ILC1's were decreased in HMO group relative to control. Our findings suggest that HMOs have a direct effect on the gastrointestinal tract metabolism and immune system even in the absence of host microbiota.