Interaction between gut bacteria and host tissue in a newborn compromised intestine
This 3 year project will be managed by Post doc Malene Cilieborg in collaboration between National Veterinary Institute, Technical University of Denmark and Department of Human Nutitrion, Faculty of Life Sciences, University of Copenhagen, as Malene Cilieborg will be employed as post doc at both universities during the project period.
The project is funded by The Danish Council for Independent research, Technology and Production Sciences.
Project period: January 2011 - December 2013.
Summary
Immediately after birth digestive problems are more common than at any other time in life. This is true for both infants and production animals, particularly when the gut mucosa is compromised by immaturity or mucosal disease. We know that the initial bacterial colonization of the gut is important for intestinal disease and immune development, but it remains unknown how the microbiota, its quantity and composition, affects the local gut host response after birth. The conditions immediately after birth when the intestine is compromised provide a particular sensitive system to study bacterial-host interactions. Using new, advanced techniques (next generation sequencing, laser capture microdissection, and confoal laser scanning microscopy), this project will investigate bacterial colonization in normal newborn pigs and infants, as well as in individuals for which the mucosa is compromized by preterm birth or chemotherapy. This will provide new detailed molecular characterization of the interactions betweeen colonizing bacteria and the intestinal tissue just after birth and will contribute to the understandingt of intestinal inflammatory diseases for both infants and piglets. We will use this advanced understanding of bacterial host-defence mechanisms in early life to propose new nutritional and pharmaceutical strategies to prevent intestinal disease in this critical period of life.
Hypotheses
- Neonatal gut colonization depends on the degree of intestinal maturity, exemplified in a distorted colonization following preterm birth and NEC development.
- Gut colonization depends on the degree of mucosal damage, exemplified in a distorted colonization following chemotherapy in early life, leading to CIM.
- The intestinal response to colonizing bacteria is a key factor in the progression of NEC and CIM.
- Dietary modulation of the host response, using colostrum, will decrease NEC and CIM sensitivity.
Background
Abundant and diverse bacteria colonize the gastrointestinal tract of humans and animals immediately after birth. They stimulate structural, functional and immunological maturation of the intestinal tissue and are essential for normal gut development (Hooper er al. 2003). Homeostasis between host and gut bacteria is ensured through comples molecular interactions and cellular signaling which are initiated when host pattern recognition receptors recognize and bind specific microbial structures (Medzhitov & Janeway, 2002). These interactions are not fully understood but disruption of the homeostasis can lead to uncontrolled inflammation leading to decreased gut barrier function, and bacterial translocation. Necrotizing enterocolitis (NEC), a severe inflammatory intestinal disease in preterm infants and newborn piglets, is an example of a tissue hyper-response to colonizing bacteria (Claud & Walker 2001; Salgild et al. 2006). The disease etiology and exactly how the microbiota is involved remains unclear (Salzman et al. 2007). Chemotherapy-induced mucositis (CIM) is another example of a condition in which tissue degradation and failed gut barrier function leads to increased risk of bacterial infection and sepsis (Vliet er al. 2010). This is related to the fact that chemotherapy particularly affects rapidly dividing cells and epithelia (including bone marrow and gut mucosa). Chemotherapy is routinely required for leukaemia treatment, the most prevalent cancer in children, and CIM is a common complication for these children. Likely chemotherapy alters the microbiota but it remains unclear how this influences the mucosa and thereby contribute to CIM (Vliet et al. 2010. Both NEC and CIM are associated with high morbidity and mortality. Because pigs and humans share similar intestinal characteristics, including anatomy, function, ontogeny and microbiota, the newborn pig is an optimal animal model for studying bacterial dependent intestinal diseases in human infants. In addition the pig is an important production animal for which neonatal bacteria-related digestive disease is an increasing problem (Songer et al. 2005).
Bacteria colonization and the following tissue responses depend on the ontogenetic and health status of the intestine (Cilieborg et al. 2009a) and may be modified by the initial diet (Cilieborg et al. 2009b). Colostrum (the first milk) contains high amounts of growth enhancing, antimicrobial, and immunomodulatory compounds and is reported to modify host responses (Diehl-Jones & Askin 2004). We have in recent years demonstrated the high potential of cow's colostrum to modulate bacteria-host responses in young piglets (Sangild er al. 2006; Bjornvad er al. 2008; Cilieborg et al. 2010; Møller er al. 2010). It is essential to investigate the bacteria-host interactions at a molecular level to understand the balance between adverse responses and tolerance in both normal and compromised states such as NEC and CIM. New advanced molecular techniques, including next generation sequencing (NGS), confocal laser scanning microscopy (CLSM) and laser capture microscopy (LCM) cam provide these novel details in the characterization of neonatal gut colonization, and the molecular interactions with the intestine. This information will form the mechanistic basis for explaining bacteria-induced intestinal disease in early life and facilitate new dietary and therapeutic treatments that modulate this response.
Project participants
National Veterinary Institute, Technical University of Denmark
Malene Cilieborg, PhD, post doc, project manager
Mette Boye, MSc, PhD, Professor
Faculty of Life Sciences, Univesity of Copenhagen
Per T. Sangild, Professor
University of Memphis
Randal Buddington, PhD
University of Pittsburg
David J. Hackam, PhD
Literature cited
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