Germfree status of mice obtained by embryo transfer in an isolator environment

The technique of embryo transfer has been evaluated for the purpose of changing the mouse stocks to a germfree (GF) status. Our results show reproducible and quality-assured conversion of animals to those which are negative for the presence of microorganisms. Rapid and easy access to GF mice is advantageous for studies of selected microflora and their cross-talks with the host, when applying, e.g. genomic, proteomic and metabolic methodology.The study involved embryo transfer in an isolator environment, thereby allowing implantation of cleansed embryos into GF recipients under well-controlled conditions. The recipient females gave birth normally and took care of the offspring as if they were their own pups, thus enhancing the survival rate. Access to full technical resources required to maintain GF isolators are, however, a prerequisite. In this study, we used stainless steel isolators designed by Gustafsson (1959), on which a stereomicroscope was mounted to facilitate embryo transfer inside the isolator.The use of embryo transfer and isolator techniques will facilitate the availability of various mouse mutant models under different gnotobiotic conditions, GF, monoxenic or polyxenic animals, to enable comparison with conventional animals for physiological and pathophysiological studies.     

Stochastic changes over time and not founder effects drive cage effects in microbial community assembly in a mouse model

Maternal transmission and cage effects are powerful confounding factors in microbiome studies. To assess the consequences of cage microenvironment on the mouse gut microbiome, two groups of germ-free (GF) wild-type (WT) mice, one gavaged with a microbiota harvested from adult WT mice and another allowed to acquire the microbiome from the cage microenvironment, were monitored using Illumina 16S rRNA sequencing over a period of 8 weeks. Our results revealed that cage effects in WT mice moved from GF to specific pathogen free (SPF) conditions take several weeks to develop and are not eliminated by the initial gavage treatment. Initial gavage influenced, but did not eliminate a successional pattern in which Proteobacteria became less abundant over time. An analysis in which 16S rRNA sequences are mapped to the closest sequenced whole genome suggests that the functional potential of microbial genomes changes significantly over time shifting from an emphasis on pathogenesis and motility early in community assembly to metabolic processes at later time points. Functionally, mice allowed to naturally acquire a microbial community from their cage, but not mice gavaged with a common biome, exhibit a cage effect in Dextran Sulfate Sodium-induced inflammation. Our results argue that while there are long-term effects of the founding community, these effects are mitigated by cage microenvironment and successional community assembly over time, which must both be explicitly considered in the interpretation of microbiome mouse experiments.     

Production of germfree mice by embryo transfer.

We applied the embryo transfer technique to germfree (GF) mouse production. Embryos harvested from superovulated mice were transferred aseptically, in a sterile environment, to the uterus of GF recipient females which had been mated with vasectomized GF males. One of the recipients became pregnant and delivered offspring. Sterility tests confirmed that the vasectomized males, newborns, recipient female mice, embryo-containing culture media, and the inside of the vinyl film isolator were germfree. These results suggest that the embryo transfer technique can be successfully applied to the production of GF mice.     

Variation in Taxonomic Composition of the Fecal Microbiota in an Inbred Mouse Strain across Individuals and Time

Genetics, diet, and other environmental exposures are thought to be major factors in the development and composition of the intestinal microbiota of animals. However, the relative contributions of these factors in adult animals, as well as variation with time in a variety of important settings, are still not fully understood. We studied a population of inbred, female mice fed the same diet and housed under the same conditions. We collected fecal samples from 46 individual mice over two weeks, sampling four of these mice for periods as long as 236 days for a total of 190 samples, and determined the phylogenetic composition of their microbial communities after analyzing 1,849,990 high-quality pyrosequencing reads of the 16S rRNA gene V3 region. Even under these controlled conditions, we found significant inter-individual variation in community composition, as well as variation within an individual over time, including increases in alpha diversity during the first 2 months of co-habitation. Some variation was explained by mouse membership in different cage and vendor shipment groups. The differences among individual mice from the same shipment group and cage were still significant. Overall, we found that 23% of the variation in intestinal microbiota composition was explained by changes within the fecal microbiota of a mouse over time, 12% was explained by persistent differences among individual mice, 14% by cage, and 18% by shipment group. Our findings suggest that the microbiota of controlled populations of inbred laboratory animals may not be as uniform as previously thought, that animal rearing and handling may account for some variation, and that as yet unidentified factors may explain additional components of variation in the composition of the microbiota within populations and individuals over time. These findings have implications for the design and interpretation of experiments involving laboratory animals.     

Procurement and Maintenance of Germ-Free Swine for Microbiological Investigations

Germ-free swine were routinely procured by both hysterectomy and hysterotomy (Caesarian section). By means of light-weight portable equipment, piglets could be obtained and transported to the laboratory (without contamination) over distances in excess of 100 miles. The isolators employed in rearing were constructed of stainless steel and flexible plastic film. At weekly intervals, fecal swabs and waste from the floor of the isolator were cultured on blood-agar and in thioglycolate broth, as well as being examined microscopically for the presence of bacteria, yeast, and fungi. The presence of pleuropneumonia-like organisms (PPLO) and viruses in such material was not demonstrable, either by the use of enriched PPLO media or primary porcine-kidney cell cultures. Tissues, body fluids, and cecal contents of piglets sacrificed specifically for microbiological examination were also negative for PPLO, viruses, bacteria, yeast, and fungi. Prenatal infestations by ascarids were not observed. Nutritional problems related to rearing of germ-free piglets, such as hypoglycemia, were not encountered, and the use of an autoclaved commercial sow's milk replacer proved quite satisfactory. The temperature to which piglets were subjected during the first few days of life, however, was very important. The isolator design and application of gnotobiotic techniques to the procurement and rearing of a large germ-free animal such as the pig proved feasible and less difficult than anticipated.     

The Gut Microbiota and Developmental Programming of the Testis in Mice

Nutrients and environmental chemicals, including endocrine disruptors, have been incriminated in the current increase in male reproductive dysfunction, but the underlying mechanisms remain unknown. The gastrointestinal tract represents the largest surface area exposed to our environment and thereby plays a key role in connection with exposure of internal organs to exogenous factors. In this context the gut microbiome (all bacteria and their metabolites) have been shown to be important contributors to body physiology including metabolism, cognitive functions and immunity. Pivotal to male reproduction is a proper development of the testis, including the formation of the blood-testis barrier (BTB) that encapsulates and protects germ cells from stress induced environmental cues, e.g. pathogenic organisms and xenobiotics. Here we used specific pathogen free (SPF) mice and germ-free (GF) mice to explore whether gut microbiota and/or their metabolites can influence testis development and regulation of BTB. Lumen formation in the seminiferous tubules, which coincides with the development of the BTB was delayed in the testes of GF mice at 16 days postpartum. In addition, perfusion experiments (Evans blue) demonstrated increased BTB permeability in these same mice. Reduced expressions of occludin, ZO-2 and E-cadherin in GF testis suggested that the microbiota modulated BTB permeability by regulation of cell-cell adhesion. Interestingly, exposure of GF mice to Clostridium Tyrobutyricum (CBUT), which secrete high levels of butyrate, restored the integrity of the BTB and normalized the levels of cell adhesion proteins. Moreover, the GF mice exhibited lower serum levels of gonadotropins (LH and FSH) than the SPF group. In addition, the intratesticular content of testosterone was lower in GF compared to SPF or CBUT animals. Thus, the gut microbiome can modulate the permeability of the BTB and might play a role in the regulation of endocrine functions of the testis.     

Gene Expression Changes in the Olfactory Bulb of Mice Induced by Exposure to Diesel Exhaust Are Dependent on Animal Rearing Environment

There is an emerging concern that particulate air pollution increases the risk of cranial nerve disease onset. Small nanoparticles, mainly derived from diesel exhaust particles reach the olfactory bulb by their nasal depositions. It has been reported that diesel exhaust inhalation causes inflammation of the olfactory bulb and other brain regions. However, these toxicological studies have not evaluated animal rearing environment. We hypothesized that rearing environment can change mice phenotypes and thus might alter toxicological study results. In this study, we exposed mice to diesel exhaust inhalation at 90 µg/m³, 8 hours/day, for 28 consecutive days after rearing in a standard cage or environmental enrichment conditions. Microarray analysis found that expression levels of 112 genes were changed by diesel exhaust inhalation. Functional analysis using Gene Ontology revealed that the dysregulated genes were involved in inflammation and immune response. This result was supported by pathway analysis. Quantitative RT-PCR analysis confirmed 10 genes. Interestingly, background gene expression of the olfactory bulb of mice reared in a standard cage environment was changed by diesel exhaust inhalation, whereas there was no significant effect of diesel exhaust exposure on gene expression levels of mice reared with environmental enrichment. The results indicate for the first time that the effect of diesel exhaust exposure on gene expression of the olfactory bulb was influenced by rearing environment. Rearing environment, such as environmental enrichment, may be an important contributive factor to causation in evaluating still undefined toxic environmental substances such as diesel exhaust.     

New Ventilated Isolation Cage

A multifunction lid has been developed for a commercially available transparent animal cage which permits feeding, watering, viewing, long-term holding, and local transport of laboratory rodents on experiment while isolating the surrounding environment. The cage is airtight except for its inlet and exhaust high-efficiency particulate air filters, and it is completely steam-sterilizable. Opening of the cage's feed and water ports causes an inrush of high velocity air which prevents back-migration of aerosols and permits feeding and watering while eliminating need for chemical vapor decontamination. Ventilation system design permits the holding in adjacent cages of animals infected with different organisms without danger of cross-contamination; leaves the animal room odor-free; reduces required bedding changes to twice a month or less, and provides investigators with capability to control precisely individual cage ventilation rates. Forty-eight cages can be conveniently placed on a standard NIH "shoebox" cage rack (60 inches wide x 28 inches deep x 74 inches high) fitted with a simple manifold exhaust system. The entire system is mobile, requiring only an electrical power outlet. Principal application of the caging system is in the area of preventing exposure of animal caretakers to pathogenic substances associated with the animal host, and in reducing handling of animals and their exposure to extraneous contamination.     

An autoclavable stainless steel isolator for small scale gnotobiotic experiments (author's transl)

A lightweight stainless steel autoclavable pentagon isolator was designed for experiments using gnotobiotic mice. The chamber, 400 x 450 x 350 mm, has an entry port 200 mm in diameter at the back and a window at the ceiling. The globes and two filters were equipped at the front and each side, respectively. An inner stainless steel cap of the entry lock was sealed by a seamless silicone band. It was possible to ventilate this isolator by either free-flow or blower operation. After autoclaving the isolators 10 to 16 times for a year, none of them was repaired. Five mice can be kept in this isolator for about 1 month without supply of diet, water and wood shaving after the first setting.     

Good design practices for an integrated containment and production system for advanced therapies

Advances in molecular biology and the possibility of differentiating stem cells have opened up new scenarios in therapies that use progenitor or variously differentiated cells. Regardless of the choice of the system, designing a plant for producing advanced therapies requires a clear understanding of the final objective (the product), taking into account all the regulatory, environment, process, risk assessment, asepsis, and validation aspects involved until its implementation. Good Manufacturing Practice (GMP) compliant procedures are a prerequisite for cell production in clinical application, and clean rooms are zones for producing cell therapies. Clean rooms for clinical application require high running and maintenance costs and need trained operators and strict procedures to prepare the rooms and the people involved in the processes. While today production mainly occurs in open systems (clean rooms), there is evidence of processes in closed systems (isolators). The isolator is a Grade A aseptic closed system that requires a controlled environment and at least a Grade D environment in the case of sterile productions (A in D closed system). The use of isolators can ensure a very high level of protection against the risk of product contamination and, at the same time, provide the operators with a very safe working environment. Furthermore, working with closed systems can optimize and facilitate the production of Advanced Therapy Medical Products in GMP environments, by providing an easily reproducible working tool even for large-scale production, with generally lower costs compared to a classical clean room approach. In conclusion, the isolator workstation as a possible alternative to the classic clean room, due to its small size and the simplification of the working and maintenance operational procedures, may represent an interesting solution in the perspective of the increasingly more stringent requests for cost reductions of GMP in clinical application.     

New Ventilated Isolation Cage

A multifunction lid has been developed for a commercially available transparent animal cage which permits feeding, watering, viewing, long-term holding, and local transport of laboratory rodents on experiment while isolating the surrounding environment. The cage is airtight except for its inlet and exhaust high-efficiency particulate air filters, and it is completely steam-sterilizable. Opening of the cage''s feed and water ports causes an inrush of high velocity air which prevents back-migration of aerosols and permits feeding and watering while eliminating need for chemical vapor decontamination. Ventilation system design permits the holding in adjacent cages of animals infected with different organisms without danger of cross-contamination; leaves the animal room odor-free; reduces required bedding changes to twice a month or less, and provides investigators with capability to control precisely individual cage ventilation rates. Forty-eight cages can be conveniently placed on a standard NIH “shoebox” cage rack (60 inches wide × 28 inches deep × 74 inches high) fitted with a simple manifold exhaust system. The entire system is mobile, requiring only an electrical power outlet. Principal application of the caging system is in the area of preventing exposure of animal caretakers to pathogenic substances associated with the animal host, and in reducing handling of animals and their exposure to extraneous contamination.     

SPF大鼠感染金黄色葡萄球菌原因的调查分析

目的连续监测某实验动物饲养场SPF大鼠携带的金黄色葡萄球菌Staphylococcus aureus(SA)情况,结合该饲养场环境、人员等检测结果,查找污染源,为保障和提高实验动物质量提供依据。方法2011—2017年依据《实验动物金黄色葡萄球菌检测方法(GB/T 14926.14-2001)》对SPF大鼠进行SA监测,并采集饲养环境和饲养人员的样本进行检测。对所有分离的SA菌株应用金黄色葡萄球菌A蛋白(SPA)基因分型和脉冲场凝胶电泳(PFGE)分型,分析污染源。结果35份SPF大鼠检出16株SA,检出率45.71%;18份饲养环境和饲养人员样本检出2株SA,检出率11.11%。SPA分型可分成5个型别,T2360为优势型别,主要由2013年和2017年SPF大鼠中的菌株组成。PFGE有5种带型,SA4为主要带型。饲养环境中SA的PFGE带型与2017年SPF大鼠中的完全一致。结论饲养环境中存在的SA与SPF大鼠感染的SA具有紧密联系。     

Effect of gut microbiota on host whole metabolome

Introduction

Recent advances in microbiome research have revealed the diverse participation of gut microbiota in a number of diseases. Bacteria-specific endogenous small molecules are produced in the gut, are transported throughout the whole body by circulation, and play key roles in disease establishment. However, the factors and mechanisms underlying these microbial influences largely remain unknown.

Objectives

The purpose of this study was to use metabolomics to better understand the influence of microbiota on host physiology.

Methods

Germ-free mice (GF) were orally administered with the feces of specific pathogen-free (SPF) mice and were maintained in a vinyl isolator for 4 weeks for establishing the so-called ExGF mice. Comparative metabolomics was performed on luminal contents, feces, urine, plasma, and tissues of GF and ExGF mice.

Results

The metabolomics profile of 1716 compounds showed marked difference between GF and ExGF for each matrix. Intestinal differences clearly showed the contribution of microbiota to host digestive activities. In addition, colonic metabolomics revealed the efficient conversion of primary to secondary metabolites by microbiota. Furthermore, metabolomics of tissues and excrements demonstrated the effect of microbiota on the accumulation of metabolites in tissues and during excretion. These effects included known bacterial effects (such as bile acids and amino acids) as well as novel ones, including a drastic decrease of sphingolipids in the host.

Conclusion

The diverse effects of microbiota on different sites of the host metabolome were revealed and novel influences on host physiology were demonstrated. These findings should contribute to a deeper understanding of the influence of gut microbiota on disease states and aid in the development of effective intervention strategies.

     

Multi-scale ecological filters shape the crayfish microbiome

A general and practical understanding of the processes that drive microbiome assembly and structure are paramount to understanding organismal biology, health, and evolution. In this study of stream-dwelling crayfish, we conceptualized colonization of microbial symbionts as a series of ecological filters that operate at the environment, host, and host microsite levels, and identified key ecological processes at each level. A survey of Cambarus sciotensis in western Virginia, USA, showed that the local environment and host microsites interact to create complex patterns of microbial diversity and composition. An in situ experiment confirmed a prevailing effect of host microsite on microbial composition, and also showed that an ectosymbiotic worm (Annelida; Branchiobdellida) which feeds on biofilms and other symbionts had significant effects on microbial composition of the host carapace, but not gills. Bacterial communities of the carapace were taxonomically rich and even, and correlated with microbial communities of the ambient environment. Conversely, communities on gills were less diverse and dominated by two taxa with potential functional significance: Comamonadaceae and Chitinophagaceae. The bacterial communities of the gills appear to be tightly coupled to host biology, and those of the carapace are mostly determined by environmental context. Our work provides the first characterization of the crayfish microbiome and shows how multi-scale and experimental studies of symbiont community assembly provide valuable insights into how the animal microbiome is structured under conditions of natural complexity. Furthermore, this study demonstrates that metazoan symbiont taxa, i.e., the branchiobdellidans, can alter microbiome assembly and structure.     

Early life experiences affect the adaptive capacity of rearing hens during infectious challenges

This study aimed to investigate whether pre- and early postnatal experiences of rearing hens contribute to the ability to cope with infectious challenges at an older age. In a 2 × 2 factorial arrangement, 352 Lohmann Brown chicks were exposed to either suboptimal or optimized incubation plus hatch conditions, and to cage or enriched rearing from week 0 to 7 of age. After week 7 all rearing conditions were similar until the end of the experiment. The development of adaptive capacity to infectious challenges was investigated by introducing an Eimeria and Infectious Bronchitis (IB) infection on day 53 and day 92, respectively. BW gain and feed intake during the infections, duodenal lesions and amount of positive stained CD4+ T cells, CD8+ T cells and macrophages at day 4 and day 7 after Eimeria infection, as well as the IB antibody titer throughout the experimental period were determined. The results showed a significant interaction between incubation plus hatch and rearing environment. Optimized incubation plus hatch conditions followed by an enriched rearing environment resulted in the least weight loss (P < 0.05) and the highest feed intake (P < 0.01) from day 3 to day 7 after the Eimeria infection (day 56 to 60 of age), compared with all other treatments. In addition, the optimized × enriched chicks had the highest BW gain from day 7 to day 14 after IB infection (day 99 to 106 of age), compared with chicks housed in a cage environment (P < 0.01). Besides the interaction, optimized incubation plus hatch alone resulted in reduced macrophage numbers in the duodenal tissue at day 4 after Eimeria infection, compared with suboptimal incubation plus hatch, whereas the enriched rearing environment stimulated the recovery of intestinal damage caused by Eimeria (P < 0.05) and reduced the production of specific antibodies after IB infection (P < 0.05), compared with the cage environment. In conclusion, this study shows that early life experiences can indeed affect the capacity of rearing hens to cope with an Eimeria and IB infection at an older age, in which performance of chicks is best maintained after optimized incubation plus hatch followed by enriched rearing. This suggests that the development of adaptive capacity to infectious challenges can be influenced with management during a short period in pre- or early postnatal life, but that effects last for a considerable time after cessation of the specific management.     

树鼩独立换气笼具的设计

目的设计研究一种满足于树鼩感染性疾病动物模型实验生物安全要求的独立换气专用隔离笼具。方法根据树驹的生物学特性、实验生物安全要求及有关实验动物笼具标准进行设计。结果该笼舍完全适用于感染性疾病实验树鼢的饲养和实验操作。结论该笼具能达到维护实验动物福利,保证实验动物质量,保障人身健康,保护环境的要求,对于使用树鼩开展人类重大传染病研究具有广泛的应用价值和市场前景。     

The impact of reduced frequency of cage changes on the health of mice housed in ventilated cages

Our purpose in this investigation was to determine if we could reduce cage changing frequency without adversely affecting the health of mice. We housed mice at three different cage changing frequencies: 7, 14, and 21 days, each at three different cage ventilation rates: 30, 60 and 100 air changes per hour (ACH), for a total of nine experimental conditions. For each condition, we evaluated the health of 12 breeding pairs and 12 breeding trios of C57BL/6J mice for 7 months. Health was assessed by breeding performance, weanling weight and growth, plasma corticosterone levels, immune function, and histological examination of selected organs. Over a period of 4 months, we monitored the cage microenvironment for ammonia and carbon dioxide concentrations, relative humidity, and temperature one day prior to changing the cage. The relative humidity, carbon dioxide concentrations, and temperature of the cages at all conditions were within acceptable levels. Ammonia concentrations remained below 25 ppm (parts per million) in most cages, but, even at higher concentrations, did not adversely affect the health of mice. Frequency of cage changing had only one significant effect; pup mortality with pair matings was greater at the cage changing frequency of 7 days compared with 14 or 21 days. In addition, pup mortality with pair matings was higher at 30 ACH compared with other ventilation rates. In conclusion, under the conditions of this study, cage changes once every 14 days and ventilation rates of 60 ACH provide optimum conditions for animal health and practical husbandry.     

Environmental plasticity and colonisation history in the Atlantic salmon microbiome: A translocation experiment

Microbial communities associated with the gut and the skin are strongly influenced by environmental factors, and can rapidly adapt to change. Historical processes may also affect the microbiome. In particular, variation in microbial colonisation in early life has the potential to induce lasting effects on microbial assemblages. However, little is known about the relative extent of microbiome plasticity or the importance of historical colonisation effects following environmental change, especially for nonmammalian species. To investigate this we performed a reciprocal translocation of Atlantic salmon between artificial and semi‐natural conditions. Wild and hatchery‐reared fry were transferred to three common garden experimental environments for 6 weeks: standard hatchery conditions, hatchery conditions with an enriched diet, and simulated wild conditions. We characterized the faecal and skin microbiome of individual fish before and after the environmental translocation, using a BACI (before‐after‐control‐impact) design. We found evidence of extensive microbiome plasticity for both the gut and skin, with the greatest changes in alpha and beta diversity associated with the largest changes in environment and diet. Microbiome richness and diversity were entirely determined by environment, with no detectable effects of fish origin, and there was also a near‐complete turnover in microbiome structure. However, we also identified, for the first time in fish, evidence of historical colonisation effects reflecting early‐life experience, including ASVs characteristic of captive rearing. These results have important implications for host adaptation to local selective pressures, and highlight how conditions experienced during early life can have a long‐term influence on the microbiome and, potentially, host health.     

A new technique to determine hydrogen excreted by gnotobiotic rats

A new system, that allowed the monitoring of hydrogen (H2) excretion by gnotobiotic rats without affecting their defined microbial status, was developed. The system consists of an isolator containing a chamber for an experimental animal, and a life-support system (LSS), with a sampling port outside the isolator connected to it. H2 accumulation in the system was measured by analysing a defined volume of gas after removal. H2 concentrations were determined with an electrochemical cell or by gas chromatography. To validate this technique, H2 excretion by germ-free (GF) and mono-associated rats fed a chemically defined diet was measured after oral application of lactulose. Mono-associated rats had been obtained by colonizing GF rats with a H2-producing Clostridium perfringens type A strain isolated from human faeces of a healthy volunteer. Application of 50 mg lactulose to the mono-associated rats resulted in a significant increase in H2 excretion. The net H2 excretion was 7.82+/-1.28 ml H2 in 12 h corresponding to a net maximal rate of 1.1+/-0.3 ml H2/h. In contrast, in experiments with GF rats, less than 0.13 ml H2 were detectable within 12 h. The technique presented is a useful tool for studying bacterial H2 metabolism in vivo under gnotobiotic conditions.     

Effect of population heterogenization on the reproducibility of mouse behavior: a multi-laboratory study

In animal experiments, animals, husbandry and test procedures are traditionally standardized to maximize test sensitivity and minimize animal use, assuming that this will also guarantee reproducibility. However, by reducing within-experiment variation, standardization may limit inference to the specific experimental conditions. Indeed, we have recently shown in mice that standardization may generate spurious results in behavioral tests, accounting for poor reproducibility, and that this can be avoided by population heterogenization through systematic variation of experimental conditions. Here, we examined whether a simple form of heterogenization effectively improves reproducibility of test results in a multi-laboratory situation. Each of six laboratories independently ordered 64 female mice of two inbred strains (C57BL/6NCrl, DBA/2NCrl) and examined them for strain differences in five commonly used behavioral tests under two different experimental designs. In the standardized design, experimental conditions were standardized as much as possible in each laboratory, while they were systematically varied with respect to the animals' test age and cage enrichment in the heterogenized design. Although heterogenization tended to improve reproducibility by increasing within-experiment variation relative to between-experiment variation, the effect was too weak to account for the large variation between laboratories. However, our findings confirm the potential of systematic heterogenization for improving reproducibility of animal experiments and highlight the need for effective and practicable heterogenization strategies.