Potential for using a hermetically-sealed, positive-pressured isocage system for studies involving germ-free mice outside a flexible-film isolator

Abstract

Germ-free mice are used to examine questions about the role of the gut microbiota in development of diseases. Generally these animals are maintained in semi-rigid or flexible-film isolators to ensure their continued sterility or, if colonized with specific microbiota, to ensure that no new species are introduced. Here, we describe the use of a caging system in which individual cages are hermetically sealed and have their own filtered positive airflow. This isopositive caging system requires less space and reduces animal housing costs. By using strict sterile techniques, we kept mice germ-free in this caging system for 12 weeks. We also used this caging system and approach to conduct studies evaluating a) the stability of the microbiome in germ-free mice receiving a fecal transplant and b) the stability of dietary-induced microbiota changes in fecal-transplanted mice. As has been shown in fecal transfer studies in isolators, we found that the transferred microbiota stabilizes as early as 2 weeks post transfer although recipient microbiota did not completely recapitulate those of the donors. Interestingly, we also noted some sex effects in these studies indicating that the sex of recipients or donors may play a role in colonization of microbiota. However, a larger study will be needed to determine what role, if any, sex plays in colonization of microbiota. Based on our studies, an isopositive caging system may be utilized to test multiple donor samples for their effects on phenotypes of mice in both normal and disease states even with limited available space for housing.

CFTR dysregulation drives active selection of the gut microbiome

“…No significant lesions were appreciated on gross examination in any of the mice. All GF mice, regardless of genotype, had markedly dilated ceca with liquid ingesta which is a well characterized finding in GF mice [28], and could account in part for differences observed in body weight between GF and SPF animals ( Fig 1A and 1B). The histologic findings in GF CF mice were consistent with those that we observed in SPF mice and that have been previously reported in this model [23,29].…”

Housing Gnotobiotic Mice in Conventional Animal Facilities

“…Currently, IVC systems can be operated under positive pressure (barrier mode or bioexclusion) or negative pressure (containment or biocontainment mode). Positive pressure ventilation (Arvidsson et al., ; Paik et al., ) is applied to create a barrier that impedes microorganisms from entering the IVC. This is the same principle that applies to isolator ventilation and is the standard when working to prevent contamination of GF animals.…”

“…Positive pressure ventilation (Arvidsson et al, 2012;Paik et al, 2015) is applied to create a barrier that impedes microorganisms from entering the IVC. This is the same principle that applies to isolator ventilation and is the standard when working to prevent contamination of GF animals.…”

Detection of succinate by intestinal tuft cells triggers a type 2 innate immune circuit

“…See also Figure S1. to hermetically-sealed positive pressure isocages as described (Paik et al, 2015) and given autoclaved 150 mM sodium succinate hexahydrate in drinking water ad libitum for 7 days.…”