FELASA recommendations for the health monitoring of mouse, rat, hamster, guinea pig and rabbit colonies in breeding and experimental units

Pneumocystis murina lesions in lungs of experimentally infected Cd40l-/- mice

The Cd40l-/- mouse is a well-established model of X-linked hyper-immunoglobulin M (IgM) syndrome, an immunodeficiency disorder of human beings characterized by the lack of expression of the CD40 ligand (CD40L) on activated T-cells, predisposing to infections with opportunistic pathogens like Pneumocystis jirovecii. The aim of our study was to describe the pulmonary lesions in Cd40l-/- mice experimentally infected with Pneumocystis murina, in comparison with naturally infected severe combined immunodeficient (SCID) mice. Formalin-fixed paraffin-embedded lungs from 26 Cd40l-/-, 11 SCID, and 5 uninfected Cd40l-/- mice were examined by histology and immunohistochemistry for the presence of the pathogen and for leukocyte populations (CD3, CD4, CD45R/B220, CD8a, Iba-1, Ly-6G, CD206, MHC II, and NKp46/NCR1). Infection was confirmed by immunohistochemistry in 18/26 (69%) Cd40l-/- mice and in 11/11 (100%) SCID mice. Fourteen out of 26 (54%) Cd40l-/- mice had interstitial pneumonia. Twenty-three out of 26 (88%) Cd40l-/- mice had peribronchiolar/perivascular lymphoplasmacytic infiltrates, rich in B-cells and Mott cells. Acidophilic macrophage pneumonia was additionally found in 20/26 (77%) Cd40l-/- mice. Only 4/11 (36%) SCID mice had interstitial pneumonia, but no peribronchiolar/perivascular infiltrates or acidophilic macrophage pneumonia were observed in this strain. This study represents the first description of pulmonary histopathological lesions in Cd40l-/- mice infected with P. murina. We speculate that the singular characteristics of the inflammatory infiltrates observed in Cd40l-/- mice could be explained by the specific immune phenotype of the model.

Preclinical Evaluation of virus-like particle Vaccine Against Carbonic Anhydrase IX Efficacy in a Mouse Breast Cancer Model System

Carbonic anhydrase IX (CAIX) is a cancer-associated membrane protein frequently overexpressed in hypoxic solid tumours leading to enhanced tumour cell survival and invasion, and it has been proposed to be an attractive tumour-specific molecule for antibody-mediated targeting. This study aimed to generate a virus-like particle (VLP)-based CAIX vaccine candidate and evaluate its efficacy in a mouse model of breast cancer. The prototype murine vaccine was developed based on the ssRNA bacteriophage Qbeta VLPs with chemically coupled murine CAIX protein catalytic domains on their surfaces. The vaccine was shown to efficiently break the natural B cell tolerance against autologous murine CAIX and to induce high-titre Th1-oriented IgG responses in the BALB/c mice. This vaccine was tested in a therapeutic setting by using a triple-negative breast cancer mouse model system comprising 4T1, 4T1-Car9KI and 4T1-Car9KO cells, the latter representing positive and negative controls for murine CAIX production, respectively. The humoural immune responses induced in tumour-bearing animals were predominantly of Th1-type and higher anti-mCAIXc titres correlated with slower growth and lung metastasis development of 4T1 tumours constitutively expressing mCAIX in vivo in the syngeneic host.

SNX27: A trans-species cognitive modulator with implications for anxiety and stress susceptibility

Sorting Nexin 27 (SNX27) is a brain-enriched endosome-associated cargo adaptor that shapes excitatory control, being relevant for cognitive and reward processing, and for several neurological conditions. Despite this, SNX27's role in the nervous system remains poorly explored. To further understand SNX27 function, we performed an extensive behavioral characterization comprising motor, cognitive and emotional dimensions of SNX27+/- mice. Furthermore, attending on the recently described association between SNX27 function and cellular stress signaling mechanisms in vitro, we explored SNX27-stress interplay using a Caenorhabditis elegans Δsnx-27 mutant and wild-type (WT) rodents after stress exposure. SNX27+/- mice, as C. elegans Δsnx-27 mutants, present cognitive impairments, highlighting a conserved role for SNX27 in cognitive modulation across species. Interestingly, SNX27 downmodulation leads to anxiety-like behavior in mice evaluated in the Elevated Plus Maze (EPM). This anxious phenotype is associated with increased dendritic complexity of the bed nucleus of the stria terminalis (BNST) neurons, and increased complexity of the basolateral amygdala (BLA) pyramidal neurons. These findings highlight the still unknown role of SNX27 in anxiety regulation. Moreover, we uncovered a direct link between SNX27 dysfunction and stress susceptibility in C. elegans and found that stress-exposed rodents display decreased SNX27 levels in stress-susceptible brain regions. Altogether, we provided new insights on SNX27's relevance in anxiety-related behaviors and neuronal structure in stress-associated brain regions.

Perspectives of FTIR as Promising Tool for Pathogen Diagnosis, Sanitary and Welfare Monitoring in Animal Experimentation Models: A Review Based on Pertinent Literature

Currently, there is a wide application in the literature of the use of the Fourier Transform Infrared Spectroscopy (FTIR) technique. This basic tool has also proven to be efficient for detecting molecules associated with hosts and pathogens in infections, as well as other molecules present in humans and animals' biological samples. However, there is a crisis in science data reproducibility. This crisis can also be observed in data from experimental animal models (EAMs). When it comes to rodents, a major challenge is to carry out sanitary monitoring, which is currently expensive and requires a large volume of biological samples, generating ethical, legal, and psychological conflicts for professionals and researchers. We carried out a survey of data from the relevant literature on the use of this technique in different diagnostic protocols and combined the data with the aim of presenting the technique as a promising tool for use in EAM. Since FTIR can detect molecules associated with different diseases and has advantages such as the low volume of samples required, low cost, sustainability, and provides diagnostic tests with high specificity and sensitivity, we believe that the technique is highly promising for the sanitary and stress and the detection of molecules of interest of infectious or non-infectious origin.

Optimizing environmental enrichment for Sprague Dawley rats: Exemplary insights into the liver proteome

BACKGROUND

Considering the expected increase in the elderly population and the growing emphasis on aging-related biomedical research, the demand for aged laboratory animals has surged, challenging established husbandry practices. Our objective was to establish a cost-effective method for environmental enrichment, utilizing the liver as a representative organ to assess potential metabolic changes in response to differing enrichment levels.

METHODS

We conducted a six-month study involving 24 male Sprague Dawley rats, randomly assigned to four environmental enrichment groups. Two groups were housed in standard cages, while the others were placed in modified rabbit cages. Half of the groups received weekly playtime in an activity focused rat housing unit. We evaluated hormone levels, playtime behavior, and subjective handling experience. Additionally, liver tissue proteomic analysis was performed.

RESULTS

Initial corticosterone levels and those after 3 and 6 months showed no significant differences. Yet, testosterone levels were lower in the control group by the end of the study (p = 0.007). We observed 1871 distinct proteins in liver tissue, with 77% being common across groups. In gene ontology analysis, no specific pathways were overexpressed. In semiquantitative analysis, we observed differences in proteins associated in lipid metabolism such as Apolipoprotein A-I and Acyl-CoA 6-desaturase, which were lower in the control group (p = 0.024 and p = 0.009). Rats in the intervention groups with weekly playtime displayed the least amount of reported distress during inspection or upon room entry and were less prone to accepting treats. Removing animals from their enclosure was most effortless for those in the large cage group. Over time, there was a decrease in conflicts among rats that interacted only twice weekly during playpen time.

DISCUSSION

In summary, refining husbandry practices for aging rats is both simple and budget-friendly, with no apparent adverse effects on stress levels, animal development, or relevant metabolic changes in the liver.

Trivalent mRNA vaccine-candidate against seasonal flu with cross-specific humoral immune response

Seasonal influenza remains a serious global health problem, leading to high mortality rates among the elderly and individuals with comorbidities. Vaccination is generally accepted as the most effective strategy for influenza prevention. While current influenza vaccines are effective, they still have limitations, including narrow specificity for certain serological variants, which may result in a mismatch between vaccine antigens and circulating strains. Additionally, the rapid variability of the virus poses challenges in providing extended protection beyond a single season. Therefore, mRNA technology is particularly promising for influenza prevention, as it enables the rapid development of multivalent vaccines and allows for quick updates of their antigenic composition. mRNA vaccines have already proven successful in preventing COVID-19 by eliciting rapid cellular and humoral immune responses. In this study, we present the development of a trivalent mRNA vaccine candidate, evaluate its immunogenicity using the hemagglutination inhibition assay, ELISA, and assess its efficacy in animals. We demonstrate the higher immunogenicity of the mRNA vaccine candidate compared to the inactivated split influenza vaccine and its enhanced ability to generate a cross-specific humoral immune response. These findings highlight the potential mRNA technology in overcoming current limitations of influenza vaccines and hold promise for ensuring greater efficacy in preventing seasonal influenza outbreaks.

Impact of the day/night cycle on functional connectome in ageing male and female mice

To elucidate how time of day, sex, and age affect functional connectivity (FC) in mice, we aimed to examine whether the mouse functional connectome varied with the day/night cycle and whether it depended on sex and age. We explored C57Bl6/J mice (6♀ and 6♂) at mature age (5 ± 1 months) and middle-age (14 ± 1 months). Each mouse underwent Blood Oxygen-Level-Dependent (BOLD) resting-state functional MRI (rs-fMRI) on a 7T scanner at four different times of the day, two under the light condition and two under the dark condition. Data processing consisted of group independent component analysis (ICA) and region-level analysis using resting-state networks (RSNs) derived from literature. Linear mixed-effect models (LMEM) were used to assess the effects of sex, lighting condition and their interactions for each RSN obtained with group-ICA (RSNs-GICA) and six bilateral RSNs adapted from literature (RSNs-LIT). Our study highlighted new RSNs in mice related to day/night alternation in addition to other networks already reported in the literature. In mature mice, we found sex-related differences in brain activation only in one RSNs-GICA comprising the cortical, hippocampal, midbrain and cerebellar regions of the right hemisphere. In males, brain activity was significantly higher in the left hippocampus, the retrosplenial cortex, the superior colliculus, and the cerebellum regardless of lighting condition; consistent with the role of these structures in memory formation and integration, sleep, and sex-differences in memory processing. Experimental constraints limited the analysis to the impact of light/dark cycle on the RSNs for middle-aged females. We detected significant activation in the pineal gland during the dark condition, a finding in line with the nocturnal activity of this gland. For the analysis of RSNs-LIT, new variables "sexage" (sex and age combined) and "edges" (pairs of RSNs) were introduced. FC was calculated as the Pearson correlation between two RSNs. LMEM revealed no effect of sexage or lighting condition. The FC depended on the edges, but there were no interaction effects between sexage, lighting condition and edges. Interaction effects were detected between i) sex and lighting condition, with higher FC in males under the dark condition, ii) sexage and edges with higher FC in male brain regions related to vision, memory, and motor action. We conclude that time of day and sex should be taken into account when designing, analyzing, and interpreting functional imaging studies in rodents.

A dual-omics approach on the effects of fibroblast growth factor-2 (FGF-2) on ventral tegmental area dopaminergic neurons in response to alcohol consumption in mice

Harmful alcohol consumption is a major socioeconomic burden to the health system, as it can be the cause of mortality of heavy alcohol drinkers. The dopaminergic (DAergic) system is thought to play an important role in the pathogenesis of alcohol drinking behaviour; however, its exact role remains elusive. Fibroblast growth factor 2 (FGF-2), a neurotrophic factor, associated with both the DAergic system and alcohol consumption, may play an important role in DAergic neuroadaptations during alcohol abuse. Within this study, we aimed to clarify the role of endogenous FGF-2 on the DAergic system and whether there is a possible link to alcohol consumption. We found that lack of FGF-2 reduces the alcohol intake of mice. Transcriptome analysis of DAergic neurons revealed that FGF-2 knockout (FGF-2 KO) shifts the molecular fingerprint of midbrain dopaminergic (mDA) neurons to DA subtypes of the ventral tegmental area (VTA). In line with this, proteomic changes predominantly appear also in the VTA. Interestingly, these changes led to an altered regulation of the FGF-2 signalling cascades and DAergic pathways in a region-specific manner, which was only marginally affected by voluntary alcohol consumption. Thus, lack of FGF-2 not only affects the gene expression but also the proteome of specific brain regions of mDA neurons. Our study provides new insights into the neuroadaptations of the DAergic system during alcohol abuse and, therefore, comprises novel targets for future pharmacological interventions.

Characterization of Different Inflammatory Skin Conditions in a Mouse Model of DNCB-Induced Atopic Dermatitis

The mouse model of 2,4-dinitrochlorbenzene (DNCB)-induced human-like atopic dermatitis (hlAD) has been widely used to test novel treatment strategies and compounds. However, the study designs and methods are highly diverse, presenting different hlAD disease patterns that occur after sensitization and repeated challenge with DNCB on dorsal skin. In addition, there is a lack of information about the progression of the disease during the experiment and the achieved pheno- and endotypes, especially at the timepoint when therapeutic treatment is initiated. We here examine hlAD in a DNCB-induced BALB/cJRj model at different timepoints: (i) before starting treatment with dexamethasone, representing a standard drug control (day 12) and (ii) at the end of the experiment (day 22). Both timepoints display typical AD-associated characteristics: skin thickening, spongiosis, hyper- and parakeratosis, altered cytokine and gene expression, increased lipid mediator formation, barrier protein and antimicrobial peptide abnormalities, as well as lymphoid organ hypertrophy. Increased mast cell infiltration into the skin and elevated immunoglobulin E plasma concentrations indicate a type I allergy response. The DNCB-treated skin showed an extrinsic moderate sub-acute hlAD lesion at day 12 and an extrinsic mild sub-acute to chronic pheno- and endotype at day 22 with a dominating Th2 response. A dependency of the filaggrin formation and expression in correlation to the disease severity in the DNCB-treated skin was found. In conclusion, our study reveals a detailed classification of a hlAD at two timepoints with different inflammatory skin conditions and pheno- and endotypes, thereby providing a better understanding of the DNCB-induced hlAD model in BALB/cJRj mice.

Bactericidal/permeability-increasing protein instructs dendritic cells to elicit Th22 cell response

Neutrophil-derived bactericidal/permeability-increasing protein (BPI) is known for its bactericidal activity against gram-negative bacteria and neutralization of lipopolysaccharide. Here, we define BPI as a potent activator of murine dendritic cells (DCs). As shown in GM-CSF-cultured, bone-marrow-derived cells (BMDCs), BPI induces a distinct stimulation profile including IL-2, IL-6, and tumor necrosis factor expression. Conventional DCs also respond to BPI, while M-CSF-cultivated or peritoneal lavage macrophages do not. Subsequent to BPI stimulation of BMDCs, CD4+ T cells predominantly secrete IL-22 and, when naive, preferentially differentiate into T helper 22 (Th22) cells. Congruent with the tissue-protective properties of IL-22 and along with impaired IL-22 induction, disease severity is significantly increased during dextran sodium sulfate-induced colitis in BPI-deficient mice. Importantly, physiological diversification of intestinal microbiota fosters BPI-dependent IL-22 induction in CD4+ T cells derived from mesenteric lymph nodes. In conclusion, BPI is a potent activator of DCs and consecutive Th22 cell differentiation with substantial relevance in intestinal homeostasis.

Sovateltide (ILR-1620) Improves Motor Function and Reduces Hyperalgesia in a Rat Model of Spinal Cord Injury

BACKGROUND

Spinal cord injury (SCI) presents a major global health challenge, with rising incidence rates and substantial disability. Although progress has been made in understanding SCI's pathophysiology and early management, there is still a lack of effective treatments to mitigate long-term consequences. This study investigates the potential of sovateltide, a selective endothelin B receptor agonist, in improving clinical outcomes in an acute SCI rat model.

METHODS

Thirty male Sprague-Dawley rats underwent sham surgery (group A) or SCI and treated with vehicle (group B) or sovateltide (group C). Clinical tests, including Basso, Beattie, and Bresnahan scoring, inclined plane, and allodynia testing with von Frey hair, were performed at various time points. Statistical analyses assessed treatment effects.

RESULTS

Sovateltide administration significantly improved motor function, reducing neurological deficits and enhancing locomotor recovery compared with vehicle-treated rats, starting from day 7 post injury. Additionally, the allodynic threshold improved, suggesting antinociceptive properties. Notably, the sovateltide group demonstrated sustained recovery, and even reached preinjury performance levels, whereas the vehicle group plateaued.

CONCLUSIONS

This study suggests that sovateltide may offer neuroprotective effects, enhancing neurogenesis and angiogenesis. Furthermore, it may possess anti-inflammatory and antinociceptive properties. Future clinical trials are needed to validate these findings, but sovateltide shows promise as a potential therapeutic strategy to improve functional outcomes in SCI. Sovateltide, an endothelin B receptor agonist, exhibits neuroprotective properties, enhancing motor recovery and ameliorating hyperalgesia in a rat SCI model. These findings could pave the way for innovative pharmacological interventions for SCI in clinical settings.

Automated analysis of gray matter damage in aged mice reveals impaired remyelination in the cuprizone model

Multiple sclerosis is a chronic autoimmune disease of the central nervous system characterized by myelin loss, axonal damage, and glial scar formation. Still, the underlying processes remain unclear, as numerous pathways and factors have been found to be involved in the development and progression of the disease. Therefore, it is of great importance to find suitable animal models as well as reliable methods for their precise and reproducible analysis. Here, we describe the impact of demyelination on clinically relevant gray matter regions of the hippocampus and cerebral cortex, using the previously established cuprizone model for aged mice. We could show that bioinformatic image analysis methods are not only suitable for quantification of cell populations, but also for the assessment of de- and remyelination processes, as numerous objective parameters can be considered for reproducible measurements. After cuprizone-induced demyelination, subsequent remyelination proceeded slowly and remained incomplete in all gray matter areas studied. There were regional differences in the number of mature oligodendrocytes during remyelination suggesting region-specific differences in the factors accounting for remyelination failure, as, even in the presence of oligodendrocytes, remyelination in the cortex was found to be impaired. Upon cuprizone administration, synaptic density and dendritic volume in the gray matter of aged mice decreased. The intensity of synaptophysin staining gradually restored during the subsequent remyelination phase, however the expression of MAP2 did not fully recover. Microgliosis persisted in the gray matter of aged animals throughout the remyelination period, whereas extensive astrogliosis was of short duration as compared to white matter structures. In conclusion, we demonstrate that the application of the cuprizone model in aged mice mimics the impaired regeneration ability seen in human pathogenesis more accurately than commonly used protocols with young mice and therefore provides an urgently needed animal model for the investigation of remyelination failure and remyelination-enhancing therapies.

Herpes simplex virus type 1 modifies the protein composition of extracellular vesicles to promote neurite outgrowth and neuroinfection

The highly prevalent herpes simplex virus type 1 (HSV-1) causes a range of diseases, including cold sores, blinding keratitis, and life-threatening encephalitis. HSV-1 initially replicates in epithelial cells, enters the peripheral nervous system via neurites, and establishes lifelong infection in the neuronal cell bodies. Neurites are highly dynamic structures that grow or retract in response to attractive or repulsive cues, respectively. Here, we show that infection with HSV-1, but not with a mutant virus lacking glycoprotein G (gG), reduced the repulsive effect of epithelial cells on neurite outgrowth and facilitated HSV-1 invasion of neurons. HSV-1 gG was required and sufficient to induce neurite outgrowth by modifying the protein composition of extracellular vesicles, increasing the amount of neurotrophic and neuroprotective proteins, including galectin-1. Antibodies directed against galectin-1 neutralized the capacity of extracellular vesicles released from HSV-1-infected cells to promote neurite outgrowth. Our study provides new insights into the neurotropism of HSV-1 and identifies a viral protein that modifies the protein composition of extracellular vesicles to stimulate neurite outgrowth and invasion of the nervous system.IMPORTANCEHerpes simplex virus type 1 (HSV-1) must infect neurites (or nerve endings) to establish a chronic infection in neurons. Neurites are highly dynamic structures that retract or grow in the presence of repulsive or attractive proteins. Some of these proteins are released by epithelial cells in extracellular vesicles and act upon interaction with their receptor present on neurites. We show here that HSV-1 infection of epithelial cells modulated their effect on neurites, increasing neurite growth. Mechanistically, HSV-1 glycoprotein G (gG) modifies the protein composition of extracellular vesicles released by epithelial cells, increasing the amount of attractive proteins that enhance neurite outgrowth and facilitate neuronal infection. These results could inform of therapeutic strategies to block HSV-1 induction of neurite outgrowth and, thereby, neuronal infection.

Microbial, proteomic, and metabolomic profiling of the estrous cycle in wild house mice

Symbiotic microbial communities affect the host immune system and produce molecules contributing to the odor of an individual. In many mammalian species, saliva and vaginal fluids are important sources of chemical signals that originate from bacterial metabolism and may act as honest signals of health and reproductive status. In this study, we aimed to define oral and vaginal microbiomes and their dynamics throughout the estrous cycle in wild house mice. In addition, we analyzed a subset of vaginal proteomes and metabolomes to detect potential interactions with microbiomes. 16S rRNA sequencing revealed that both saliva and vagina are dominated by Firmicutes and Proteobacteria but differ at the genus level. The oral microbiome is more stable during the estrous cycle and most abundant bacteria belong to the genera Gemella and Streptococcus, while the vaginal microbiome shows higher bacterial diversity and dynamics during the reproductive cycle and is characterized by the dominance of Muribacter and Rodentibacter. These two genera cover around 50% of the bacterial community during estrus. Proteomic profiling of vaginal fluids revealed specific protein patterns associated with different estrous phases. Highly expressed proteins in estrus involve the keratinization process thus providing estrus markers (e.g., Hrnr) while some proteins are downregulated such as immune-related proteins that limit bacterial growth (Camp, Clu, Elane, Lyz2, and Ngp). The vaginal metabolome contains volatile compounds potentially involved in chemical communication, for example, ketones, aldehydes, and esters of carboxylic acids. Data integration of all three OMICs data sets revealed high correlations, thus providing evidence that microbiomes, host proteomes, and metabolomes may interact.IMPORTANCEOur data revealed dynamic changes in vaginal, but not salivary, microbiome composition during the reproductive cycle of wild mice. With multiple OMICs platforms, we provide evidence that changes in microbiota in the vaginal environment are accompanied by changes in the proteomic and metabolomics profiles of the host. This study describes the natural microbiota of wild mice and may contribute to a better understanding of microbiome-host immune system interactions during the hormonal and cellular changes in the female reproductive tract. Moreover, analysis of volatiles in the vaginal fluid shows particular substances that can be involved in chemical communication and reproductive behavior.

Evaluating rearing behaviour as a model-specific pain indicator in mouse osteotomy models

To assess pain in mouse models of bone fractures, currently applied assessment batteries use combinations of clinical signs with spontaneous behaviours and model-specific behaviours, including walking and weight-bearing behaviour. Rearing behaviour - an upright position on the hindlimbs - has a motivational and an ambulatory component. Thus, rearing behaviour might have the potential to be an indicator for model-specific pain in mouse fracture models. To date, the assessment of rearing behaviour in bone fracture models using mice is only scarcely described. In this study, we aimed to determine whether the duration of rearing behaviour is affected by osteotomy of the femur in male and female C57BL/6N mice with external fixation (rigid vs. flexible) and could be an additional sign for model-specific pain, such as the presence of limping. Rearing duration was significantly decreased after osteotomy in male and female mice at 24 h, 48 h and 72 h, but was not affected by anaesthesia/analgesia alone. In male mice, the relative rearing duration increased over 72 h (both fixations) and at 10 days in the rigid fixation group but remained significantly lower in the flexible fixation group. In contrast, in female mice, no increase in rearing duration was observed within 72 h and at 10 days post-osteotomy, independent of the fixation. We did not identify any association between relative rearing time and presence or absence of limping. In summary, our results do not provide sufficient evidence that altered rearing behaviour might be an indicative sign for pain in this model.

Krishnan L, Abelson KSP. Refinement of the motorised laminectomy-assisted rat spinal cord injury model by analgesic treatment

Usage and reporting of analgesia in animal models of spinal cord injury (SCI) have been sparse and requires proper attention. The majority of experimental SCI research uses rats as an animal model. This study aimed to probe into the effects of some commonly used regimens with NSAIDs and opioids on well-being of the rats as well as on the functional outcome of the model. This eight-week study used forty-two female Wistar rats (Crl: WI), randomly and equally divided into 6 treatment groups, viz. I) tramadol (5mg/kg) and buprenorphine (0.05mg/kg); II) carprofen (5mg/kg) and buprenorphine (0.05mg/kg); III) carprofen (5mg/kg); IV) meloxicam (1mg/kg) and buprenorphine (0.05mg/kg); V) meloxicam (1mg/kg); and VI) no analgesia (0.5 ml sterile saline). Buprenorphine was administered twice daily whereas other treatments were given once daily for five days post-operatively. Injections were given subcutaneously. All animals underwent dental burr-assisted laminectomy at the T10-T11 vertebra level. A custom-built calibrated spring-loaded 200 kilodynes force deliverer was used to induce severe SCI. Weekly body weight scores, Rat Grimace Scale (RGS), and dark-phase home cage activity were used as markers for well-being. Weekly Basso Beattie and Bresnahan (BBB) scores served as markers for functionality together with Novel Object Recognition test (NOR) at week 8 and terminal histopathology using area of vacuolisation and live neuronal count from the ventral horns of spinal cord. It was concluded that the usage of analgesia improved animal wellbeing while having no effects on the functional aspects of the animal model in comparison to the animals that received no analgesics.

T-cell stimulating vaccines empower CD3 bispecific antibody therapy in solid tumors

CD3 bispecific antibody (CD3 bsAb) therapy is clinically approved for refractory hematological malignancies, but responses in solid tumors have been limited so far. One of the main hurdles in solid tumors is the lack of sufficient T-cell infiltrate. Here, we show that pre-treatment vaccination, even when composed of tumor-unrelated antigens, induces CXCR3-mediated T-cell influx in immunologically 'cold' tumor models in male mice. In the absence of CD3 bsAb, the infiltrate is confined to the tumor invasive margin, whereas subsequent CD3 bsAb administration induces infiltration of activated effector CD8 T cells into the tumor cell nests. This combination therapy installs a broadly inflamed Th1-type tumor microenvironment, resulting in effective tumor eradication. Multiple vaccination formulations, including synthetic long peptides and viruses, empower CD3 bsAb therapy. Our results imply that eliciting tumor infiltration with vaccine-induced tumor-(un)related T cells can greatly improve the efficacy of CD3 bsAbs in solid tumors.

Gut microbiota depletion delays somatic peripheral nerve development and impairs neuromuscular junction maturation

Gut microbiota is responsible for essential functions in human health. Several communication axes between gut microbiota and other organs via neural, endocrine, and immune pathways have been described, and perturbation of gut microbiota composition has been implicated in the onset and progression of an emerging number of diseases. Here, we analyzed peripheral nerves, dorsal root ganglia (DRG), and skeletal muscles of neonatal and young adult mice with the following gut microbiota status: a) germ-free (GF), b) gnotobiotic, selectively colonized with 12 specific gut bacterial strains (Oligo-Mouse-Microbiota, OMM12), or c) natural complex gut microbiota (CGM). Stereological and morphometric analyses revealed that the absence of gut microbiota impairs the development of somatic median nerves, resulting in smaller diameter and hypermyelinated axons, as well as in smaller unmyelinated fibers. Accordingly, DRG and sciatic nerve transcriptomic analyses highlighted a panel of differentially expressed developmental and myelination genes. Interestingly, the type III isoform of Neuregulin1 (NRG1), known to be a neuronal signal essential for Schwann cell myelination, was overexpressed in young adult GF mice, with consequent overexpression of the transcription factor Early Growth Response 2 (Egr2), a fundamental gene expressed by Schwann cells at the onset of myelination. Finally, GF status resulted in histologically atrophic skeletal muscles, impaired formation of neuromuscular junctions, and deregulated expression of related genes. In conclusion, we demonstrate for the first time a gut microbiota regulatory impact on proper development of the somatic peripheral nervous system and its functional connection to skeletal muscles, thus suggesting the existence of a novel 'Gut Microbiota-Peripheral Nervous System-axis.'

Microbial exposure during early life regulates development of bile duct inflammation

OBJECTIVES

The early life microbiome has been linked to inflammatory diseases in adulthood and a role for the microbiome in bile duct inflammation is supported by both human and murine studies. We utilized the NOD.c3c4 mouse model that develops a spontaneous immune-driven biliary disease with a known contribution of the microbiome to evaluate the temporal effects of the early life microbiome.

MATERIALS AND METHODS

Germ-free (GF) NOD.c3c4 mice were conventionalized into a specific pathogen free environment at birth (conventionally raised, CONV-R) or at weaning (germ-free raised, GF-R) and compared with age and gender-matched GF and conventional (CONV) NOD.c3c4 mice. At 9 weeks of age, liver pathology was assessed by conventional histology and flow cytometry immunophenotyping.

RESULTS

Neonatal exposure to microbes (CONV-R) increased biliary inflammation to similar levels as regular conventional NOD.c3c4 mice, while delayed exposure to microbes (GF-R) restrained the biliary inflammation. Neutrophil infiltration was increased in all conventionalized mice compared to GF. An immunophenotype in the liver similar to CONV was restored in both CONV-R and GF-R compared to GF mice displaying a proportional increase of B cells and reduction of T cells in the liver.

CONCLUSIONS

Microbial exposure during early life has a temporal impact on biliary tract inflammation in the NOD.c3c4 mouse model suggesting that age-sensitive interaction with commensal microbes have long-lasting effects on biliary immunity that can be of importance for human cholangiopathies.

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

Induction of CD8+ immune memory and enhanced inflammation in a skin inflammation model through pre-immunization with inactivated pathogens

Laboratory mice live in specific pathogen-free (SPF) conditions, resulting in an immature immune system comparable to that of newborns rather than adult humans or mice from pet shops. This condition may compromise their translational value. Reintroducing pathogens would lead to the uncontrolled spread of infections and associated diseases, so research facilities should seek safer alternatives. We immunized laboratory mice with a cocktail of pathogens, which were inactivated by ultraviolet irradiation and mixed with the adjuvant AddaVax. This immunization resulted in a higher percentage of CD8+ effector memory T cells compared to untreated mice, although the response was not as robust as in pet shop mice. In a model of skin inflammation, pre-immunization led to an increased skin inflammatory response compared to non-immunized mice. All immunized mice seroconverted to the pathogens in the mixture, while none of the non-immunized mice housed together seroconverted to the pathogens applied to the pre-immunized mice. In conclusion, pre-immunization of mice impacts the immune system, which includes increasing the levels of CD8+ effector memory T cells.

The MHC-E peptide ligands for checkpoint CD94/NKG2A are governed by inflammatory signals, whereas LILRB1/2 receptors are peptide indifferent

The immune checkpoint NKG2A/CD94 is a promising target for cancer immunotherapy, and its ligand major histocompatibility complex E (MHC-E) is frequently upregulated in cancer. NKG2A/CD94-mediated inhibition of lymphocytes depends on the presence of specific leader peptides in MHC-E, but when and where they are presented in situ is unknown. We apply a nanobody specific for the Qdm/Qa-1b complex, the NKG2A/CD94 ligand in mouse, and find that presentation of Qdm peptide depends on every member of the endoplasmic reticulum-resident peptide loading complex. With a turnover rate of 30 min, the Qdm peptide reflects antigen processing capacity in real time. Remarkably, Qdm/Qa-1b complexes require inflammatory signals for surface expression in situ, despite the broad presence of Qa-1b molecules in homeostasis. Furthermore, we identify LILRB1 as a functional inhibition receptor for MHC-E in steady state. These data provide a molecular understanding of NKG2A blockade in immunotherapy and assign MHC-E as a convergent ligand for multiple immune checkpoints.

The implementation of tunnel handling in a mouse breeding facility revealed strain-specific behavioural responses

As a step towards implementing non-aversive handling techniques at a big mouse breeding facility in Germany, tunnel handling was introduced in a breeding unit comprising three inbred mouse strains. To assess whether tunnel handling would be feasible for the animal technicians in their everyday work and beneficial for the mice when being handled during weekly cage change only, the behaviour of tunnel- and tail-handled animals of both sexes was examined before, during and after the handling events over a period of nine weeks. Moreover, the time expenditure was compared between both handling techniques. It was possible to use the tunnel in all three mouse strains. However, the impact of the handling techniques on the behavioural parameters investigated in the present study were strain-specific. All behavioural parameters suggested that NZW mice benefited the most from tunnel handling. The results obtained from Hello Kitty and WNK mice were ambiguous, which may suggest that a brief handling session during the cage clean may have not been sufficient to habituate them to the process of handling. It took the animal technicians approximately 3 seconds longer per mouse when using a tunnel. The strain-specific results should encourage researchers to share their experiences with non-aversive handling techniques in different mouse strains, for example, along with their research articles.

SorCS2 binds progranulin to regulate motor neuron development

Motor neuron (MN) development and nerve regeneration requires orchestrated action of a vast number of molecules. Here, we identify SorCS2 as a progranulin (PGRN) receptor that is required for MN diversification and axon outgrowth in zebrafish and mice. In zebrafish, SorCS2 knockdown also affects neuromuscular junction morphology and fish motility. In mice, SorCS2 and PGRN are co-expressed by newborn MNs from embryonic day 9.5 until adulthood. Using cell-fate tracing and nerve segmentation, we find that SorCS2 deficiency perturbs cell-fate decisions of brachial MNs accompanied by innervation deficits of posterior nerves. Additionally, adult SorCS2 knockout mice display slower motor nerve regeneration. Interestingly, primitive macrophages express high levels of PGRN, and their interaction with SorCS2-positive motor axon is required during axon pathfinding. We further show that SorCS2 binds PGRN to control its secretion, signaling, and conversion into granulins. We propose that PGRN-SorCS2 signaling controls MN development and regeneration in vertebrates.

B Cells from Aged Mice Do Not Have Intrinsic Defects in Affinity Maturation in Response to Immunization

Affinity maturation, the progressive increase in serum Ab affinity after vaccination, is an essential process that contributes to an effective humoral response against vaccines and infections. Germinal centers are key for affinity maturation, because they are where B cells undergo somatic hypermutation of their Ig genes in the dark zone before going through positive selection in the light zone via interactions with T follicular helper cells and follicular dendritic cells. In aged mice, affinity maturation has been shown to be impaired after immunization, but whether B cell-intrinsic factors contribute to this defect remains unclear. In this study, we show that B cells from aged BCR transgenic mice are able to become germinal center B cells, which are capable of receiving positive selection signals to a similar extent as B cells from young adult mice. Consistent with this, aging also does not impact the ability of B cells to undergo somatic hypermutation and acquire affinity-enhancing mutations. By contrast, transfer of B cells from young adult BCR mice into aged recipients resulted in the impaired acquisition of affinity-enhancing mutations, demonstrating that the aged microenvironment causes altered affinity maturation.

In vivo MRS study of long-term effects of traumatic intracranial injection of a culture medium in mice

Orthotopic transplantation of glioblastoma cells in the brain of laboratory mice is a common animal model for studying brain tumors. It was shown that 1H magnetic resonance spectroscopy (MRS) enables monitoring of the tumor's occurrence and its development during therapy based on the ratio of several metabolites. However, in studying new approaches to the therapy of glioblastoma in the model of orthotopic xenotransplantation of glioma cells into the brain of mice, it is necessary to understand which metabolites are produced by a growing tumor and which are the result of tumor cells injection along the modeling of the pathology. Currently, there are no data on the dynamic metabolic processes in the brain that occur after the introduction of glioblastoma cells into the brain of mice. In addition, there is a lack of data on the delayed effects of invasive brain damage. Therefore, this study investigates the long-term dynamics of the neurometabolic profile, assessed using 1H MRS, after intracranial injection of a culture medium used in orthotopic modeling of glioma in mice. Levels of N-acetylaspartate, N-acetylaspartylglutamic acid, myoinositol, taurine, glutathione, the sum of glycerophosphocholine and phosphocholine, glutamic acid (Glu), glutamine (Gln), and gamma aminobutyric acid (GABA) indicate patterns of neurometabolites in the early stage after intracranial injection similar to brain trauma ones. Most of the metabolites, with the exception of Gln, Glu and GABA, returned to their original values on day 28 after injection. A progressive increase in the Glu/Gln and Glu/GABA ratio up to 28 days after surgery potentially indicates an impaired turnover of these metabolites or increased neurotransmission. Thus, the data indicate that the recovery processes are largely completed on day 28 after the traumatic event in the brain tissue, leaving open the question of the neurotransmitter system impairment. Consequently, when using animal models of human glioma, researchers should clearly distinguish between which changes in neurometabolites are a response to the injection of cancer cells into the brain, and which processes may indicate the early development of a brain tumor. It is important to keep this in mind when modeling human glioblastoma in mice and monitoring new treatments. In addition, these results may be important in the development of approaches for non-invasive diagnostics of traumatic brain injury as well as recovery and rehabilitation processes of patients after certain brain surgeries.

Inducible overexpression of a FAM3C/ILEI transgene has pleiotropic effects with shortened life span, liver fibrosis and anemia in mice

FAM3C/ILEI is an important factor in epithelial-to-mesenchymal transition (EMT) induction, tumor progression and metastasis. Overexpressed in many cancers, elevated ILEI levels and secretion correlate with poor patient survival. Although ILEI's causative role in invasive tumor growth and metastasis has been demonstrated in several cellular tumor models, there are no available transgenic mice to study these effects in the context of a complex organism. Here, we describe the generation and initial characterization of a Tet-ON inducible Fam3c/ILEI transgenic mouse strain. We find that ubiquitous induction of ILEI overexpression (R26-ILEIind) at weaning age leads to a shortened lifespan, reduced body weight and microcytic hypochromic anemia. The anemia was reversible at a young age within a week upon withdrawal of ILEI induction. Vav1-driven overexpression of the ILEIind transgene in all hematopoietic cells (Vav-ILEIind) did not render mice anemic or lower overall fitness, demonstrating that no intrinsic mechanisms of erythroid development were dysregulated by ILEI and that hematopoietic ILEI hyperfunction did not contribute to death. Reduced serum iron levels of R26-ILEIind mice were indicative for a malfunction in iron uptake or homeostasis. Accordingly, the liver, the main organ of iron metabolism, was severely affected in moribund ILEI overexpressing mice: increased alanine transaminase and aspartate aminotransferase levels indicated liver dysfunction, the liver was reduced in size, showed increased apoptosis, reduced cellular iron content, and had a fibrotic phenotype. These data indicate that high ILEI expression in the liver might reduce hepatoprotection and induce liver fibrosis, which leads to liver dysfunction, disturbed iron metabolism and eventually to death. Overall, we show here that the novel Tet-ON inducible Fam3c/ILEI transgenic mouse strain allows tissue specific timely controlled overexpression of ILEI and thus, will serve as a versatile tool to model the effect of elevated ILEI expression in diverse tissue entities and disease conditions, including cancer.

Reduction in Cold Stress in an Innovative Metabolic Cage Housing System Increases Animal Welfare in Laboratory Mice

Housing in metabolic cages can induce a pronounced stress response. Metabolic cage systems imply housing mice on metal wire mesh for the collection of urine and feces in addition to monitoring food and water intake. Moreover, mice are single-housed, and no nesting, bedding, or enrichment material is provided, which is often argued to have a not negligible impact on animal welfare due to cold stress. We therefore attempted to reduce stress during metabolic cage housing for mice by comparing an innovative metabolic cage (IMC) with a commercially available metabolic cage from Tecniplast GmbH (TMC) and a control cage. Substantial refinement measures were incorporated into the IMC cage design. In the frame of a multifactorial approach for severity assessment, parameters such as body weight, body composition, food intake, cage and body surface temperature (thermal imaging), mRNA expression of uncoupling protein 1 (Ucp1) in brown adipose tissue (BAT), fur score, and fecal corticosterone metabolites (CMs) were included. Female and male C57BL/6J mice were single-housed for 24 h in either conventional Macrolon cages (control), IMC, or TMC for two sessions. Body weight decreased less in the IMC (females-1st restraint: -6.94%; 2nd restraint: -6.89%; males-1st restraint: -8.08%; 2nd restraint: -5.82%) compared to the TMC (females-1st restraint: -13.2%; 2nd restraint: -15.0%; males-1st restraint: -13.1%; 2nd restraint: -14.9%) and the IMC possessed a higher cage temperature (females-1st restraint: 23.7 °C; 2nd restraint: 23.5 °C; males-1st restraint: 23.3 °C; 2nd restraint: 23.5 °C) compared with the TMC (females-1st restraint: 22.4 °C; 2nd restraint: 22.5 °C; males-1st restraint: 22.6 °C; 2nd restraint: 22.4 °C). The concentration of fecal corticosterone metabolites in the TMC (females-1st restraint: 1376 ng/g dry weight (DW); 2nd restraint: 2098 ng/g DW; males-1st restraint: 1030 ng/g DW; 2nd restraint: 1163 ng/g DW) was higher compared to control cage housing (females-1st restraint: 640 ng/g DW; 2nd restraint: 941 ng/g DW; males-1st restraint: 504 ng/g DW; 2nd restraint: 537 ng/g DW). Our results show the stress potential induced by metabolic cage restraint that is markedly influenced by the lower housing temperature. The IMC represents a first attempt to target cold stress reduction during metabolic cage application thereby producing more animal welfare friendlydata.

Successful use of HTF as a basal fertilization medium during SEcuRe mouse in vitro fertilization

OBJECTIVE

The ever-increasing number of genetically engineered mouse models highlights the need for efficient archiving and distribution of these lines. Sperm cryopreservation has become the preferred technique for the majority of these models due to its low requirement of costs, time, and experimental animals. Yet, current in vitro fertilization (IVF) protocols either exhibit decreased fertilization efficiency for the most popular C57BL/6 strain, as recently demonstrated by us, or require costly and difficult-to-prepare media, respectively. As a result, we previously developed SEcuRe, a modified IVF protocol with low costs and high fertilization efficiency. The popular basal fertilization medium, Cook's® proprietary "Research vitro fert" (RVF), used in this protocol has recently been discontinued. As a result, the application of the SEcuRe approach and other IVF protocols employing this medium has been severely limited.

RESULTS

Here we show that human tubal fluid (HTF), a popular and widely available medium with a known composition, can be used as a basal fertilization medium instead of RVF. Comparison of RVF and HTF during 58 independent SEcuRe IVFs with cryopreserved C57BL/6 sperm revealed equal fertilization and live birth rates. In addition, we demonstrate that HTF has a substantially extended shelf-life by utilizing commercial HTF that was six months past its expiration date, yet did not affect fertilization during IVF or subsequent embryo development. This finding not only increases the economic value of our modified method, but also validates it once more. Our results demonstrate that common, shelf-life extended HTF can be used in SEcuRe IVF in place of now-discontinued RVF medium and ensure the applicability of the method, which we since termed SEcuRe 2.0. Our modified SEcuRe 2.0 strategy will assist researchers to efficiently archive and distribute genetically engineered mouse models in a cost-effective, easily adaptable, and 3R-compliant manner with minimal animal use.

The dopaminergic D1 receptor modulates the hyperactivity of Bapa mutant mice

The mutant bate-palmas ("claps"; symbol - bapa) mice induced by the mutagenic chemical ENU present motor incoordination and postural alterations. A previous study showed that bapa mice present increased motor/exploratory behaviors during the prepubertal period due to increased striatal tyrosine hydroxylase expression, suggesting striatal dopaminergic system hyperactivity. This study aimed to evaluate the involvement of striatal dopaminergic receptors in the hyperactivity of bapa mice. Male bapa mice and their wild strain (WT) were used. Spontaneous motor behavior was observed in the open-field test, and stereotypy was evaluated after apomorphine administration. The effects of DR1 and DR2 dopaminergic antagonists (SCH-23,390; sulpiride) and the striatal DR1 and D2 receptor gene expression were evaluated. Relative to WT, bapa mice showed: 1) increased general activity for four days; 2) increased rearing and sniffing behavior and decreased immobility after apomorphine; 3) blockage of rearing behavior after the DR2 antagonist but no effect after DR1 antagonist; 4) blockage of sniffing behavior after the DR1 antagonist in bapa and WT mice but no effect after the DR2 antagonist; 5) increased immobility after the DR1 antagonist but no effect after the DR2 antagonist; 6) increased expression of striatal DR1 receptor gene and reduced the DR2 expression gene after apomorphine administration. Bapa mice showed increased activity in open field behavior. The increased rearing behavior induced by apomorphine of bapa mice resulted from the increased gene expression of the DR1 receptor.

Refining Stereotaxic Neurosurgery Techniques and Welfare Assessment for Long-Term Intracerebroventricular Device Implantation in Rodents

Stereotaxic surgeries enable precise access to specific brain regions, being of particular interest for chronic intracerebroventricular drug delivery. However, the challenge of long-term studies at this level is to allow the implantation of drug storage devices and their correct intrathecal connection while guaranteeing animal welfare during the entire study period. In this study, we propose an optimized method for safe intrathecal device implantation, focusing on preoperative, intraoperative, and postoperative procedures, following the 3Rs principle and animal welfare regulations. Our optimized protocol introduces three main refinements. Firstly, we modify the dimensions of the implantable devices, notably diminishing the device-to-mouse weight ratio. Secondly, we use a combination of cyanoacrylate tissue adhesive and UV light-curing resin, which decreases surgery time, improves healing, and notably minimizes cannula detachment or adverse effects. Thirdly, we develop a customized welfare assessment scoresheet to accurately monitor animal well-being during long-term implantations. Taken together, these refinements positively impacted animal welfare by minimizing the negative effects on body weight, surgery-related complications, and anxiety-like behaviors. Overall, the proposed refinements have the potential to reduce animal use, enhance experimental data quality, and improve reproducibility. Additionally, these improvements can be extended to other neurosurgical techniques, thereby advancing neuroscience research, and benefiting the scientific community.

Comparison of unilateral and bilateral embryo transfer in mice

Surgical embryo transfer in mice is a key technique in assisted reproduction and applied for different purposes in biomedical research. Due to its frequent application in rodent facilities across the world, further improvement of the procedure can substantially contribute to fulfil the principles of the 3Rs. Here, we investigated the effect of bilateral and unilateral left- or right-sided oviduct transfers on the success of embryo transfers. In total, we performed 223 embryo transfers (56 unilateral left, 56 unilateral right, 111 bilateral), in which we transferred 10-14 two-cell embryos each. We found that the type of transfer significantly influenced both the pregnancy rate of recipients and the survival rate of transferred embryos. Bilateral transfers yielded higher pregnancy and survival rates than left-sided unilateral transfers. Right-sided unilateral transfers yielded higher pregnancy rates than left-sided unilateral transfers and did not differ in embryo survival rates from bilateral transfers. We found no evidence that the number of transferred embryos affected the pregnancy rate. However, the number of born pups increased with the number of transferred embryos. In conclusion, unilateral embryo transfers into the right reproductive tract yield equally high pregnancy and embryo survival rates as bilateral transfers. Given that a second abdominal incision can be prevented and the time of surgery can be reduced, we recommend applying unilateral right-sided transfers, as this would reduce postoperative pain and lower the impact on recipients.

Establishment and Characterization of Mild Atopic Dermatitis in the DNCB-Induced Mouse Model

In dermatological research, 2,4-dinitrochlorbenzene (DNCB)-induced atopic dermatitis (AD) is a standard model as it displays many disease-associated characteristics of human AD. However, the reproducibility of the model is challenging due to the lack of information regarding the methodology and the description of the phenotype and endotype of the mimicked disease. In this study, a DNCB-induced mouse model was established with a detailed procedure description and classification of the AD human-like skin type. The disease was induced with 1% DNCB in the sensitization phase and repeated applications of 0.3% and 0.5% DNCB in the challenging phase which led to a mild phenotype of AD eczema. Pathophysiological changes of the dorsal skin were measured: thickening of the epidermis and dermis, altered skin barrier proteins, increased TH1 and TH2 cytokine expression, a shift in polyunsaturated fatty acids, increased pro-resolving and inflammatory mediator formation, and dysregulated inflammation-associated gene expression. A link to type I allergy reactions was evaluated by increased mast cell infiltration into the skin accompanied by elevated IgE and histamine levels in plasma. As expected for mild AD, no systemic inflammation was observed. In conclusion, this experimental setup demonstrates many features of a mild human-like extrinsic AD in murine skin.

Impaired Abcb1a function and red meat in a translational colitis mouse model induces inflammation and alters microbiota composition

Inflammatory Bowel Disease (IBD) affects approximately 0.3% of the global population, with incidence rates rising dramatically worldwide. Emerging evidence points to an interplay between exposome factors such as diet and gut microbiota, host genetics, and the immune system as crucial elements in IBD development. ATP-binding cassette (ABC) transporters, including human p-glycoprotein encoded by the Abcb1 gene, influence intestinal inflammation, and their expression may interact with environmental factors such as diet and gut microbes. Our study aimed to examine the impact of protein sources on a genetic colitis mouse model.

Methods

Abcb1a-deficient colitis mice were fed either casein or red meat-supplemented diets to investigate potential colitis-aggravating components in red meat and their effects on host-microbiota interactions. We conducted deep label free quantitative proteomic inflammation profiling of gastrointestinal tissue (colon, ileum) and urine, and determined the overall microbiome in feces using 16S rRNA gene sequencing. Microbiota shifts by diet and protein transporter impairment were addressed by multivariate statistical analysis. Colon and systemic gut inflammation were validated through histology and immune assays, respectively.

Results

A quantitative discovery based proteomic analysis of intestinal tissue and urine revealed associations between ileum and urine proteomes in relation to Abcb1a deficiency. The absence of Abcb1a efflux pump function and diet-induced intestinal inflammation impacted multiple systemic immune processes, including extensive neutrophil extracellular trap (NET) components observed in relation to neutrophil degranulation throughout the gastrointestinal tract. The colitis model's microbiome differed significantly from that of wild-type mice, indicating the substantial influence of efflux transporter deficiency on microbiota.

Conclusion

The proteomic and microbiota analyzes of a well-established murine model enabled the correlation of gastrointestinal interactions not readily identifiable in human cohorts. Insights into dysregulated biological pathways in this disease model might offer translational biomarkers based on NETs and improved understanding of IBD pathogenesis in human patients. Our findings demonstrate that drug transporter deficiency induces substantial changes in the microbiota, leading to increased levels of IBD-associated strains and resulting in intestinal inflammation. GRAPHICAL ABSTRACT.

Protection of pancreatic islets from oxidative cell death by a peripherally-active morphinan with increased drug safety

OBJECTIVE

Dextromethorphan (DXM) is a commonly used antitussive medication with positive effects in people with type 2 diabetes mellitus, since it increases glucose tolerance and protects pancreatic islets from cell death. However, its use as an antidiabetic medication is limited due to its central nervous side effects and potential use as a recreational drug. Therefore, we recently modified DXM chemically to reduce its blood-brain barrier (BBB) penetration and central side effects. However, our best compound interacted with the cardiac potassium channel hERG (human ether-à-go-go-related gene product) and the μ-opioid receptor (MOR). Thus, the goal of this study was to reduce the interaction of our compound with these targets, while maintaining its beneficial properties.

METHODS

Receptor and channel binding assays were conducted to evaluate the drug safety of our DXM derivative. Pancreatic islets were used to investigate the effect of the compound on insulin secretion and islet cell survival. Via liquor collection from the brain and a behavioral assay, we analyzed the BBB permeability. By performing intraperitoneal and oral glucose tolerance tests as well as pharmacokinetic analyses, the antidiabetic potential and elimination half-life were investigated, respectively. To analyze the islet cell-protective effect, we used fluorescence microscopy as well as flow cytometric analyses.

RESULTS

Here, we report the design and synthesis of an optimized, orally available BBB-impermeable DXM derivative with lesser binding to hERG and MOR than previous ones. We also show that the new compound substantially enhances glucose-stimulated insulin secretion (GSIS) from mouse and human islets and glucose tolerance in mice as well as protects pancreatic islets from cell death induced by reactive oxygen species and that it amplifies the effects of tirzepatide on GSIS and islet cell viability.

CONCLUSIONS

We succeeded to design and synthesize a novel morphinan derivative that is BBB-impermeable, glucose-lowering and islet cell-protective and has good drug safety despite its morphinan and imidazole structures.

Mate genetic similarity affects mating behaviour but not maternal investment in mice

Maternal investment can affect the survival and development of offspring. Here we experimentally investigated in mice, whether females alter implantation rates and pup survival after embryo transfer depending on the genetic similarity with their vasectomised mating partner. We selected the MHC genotype and genetic background of males and paired females either with males that shared the same MHC haplotype and genetic background (CBA/J inbred males, isogenic group), that shared half of the MHC haplotype and genetic background (B6CBAF1 hybrid males, semi-isogenic group), or that had a different MHC haplotype and genetic background (C57BL/6N inbred males, allogenic group). We performed 304 pairings, resulting in 81 vaginal plugs, which confirmed mating. Plug rates were significantly higher in the semi-isogenic group (36.9%) compared to the isogenic group (19.5%), but not the allogenic group (26%). We found no difference in the number of implantation sites, the number of born or surviving pups until weaning, or litter weight or sex ratio between groups. Even though we found a mating bias, we found no difference in maternal investment under laboratory conditions. At least under pathogen-free conditions our study does not provide any evidence for differential maternal investment when females could increase offspring genetic diversity or heterozygosity.

Bouts of rest and physical activity in C57BL/6J mice

The objective was to exploit the raw data output from a scalable home cage (type IIL IVC) monitoring (HCM) system (DVC®), to characterize pattern of undisrupted rest and physical activity (PA) of C57BL/6J mice. The system's tracking algorithm show that mice in isolation spend 67% of the time in bouts of long rest (≥40s). Sixteen percent is physical activity (PA), split between local movements (6%) and locomotion (10%). Decomposition revealed that a day contains ˜7100 discrete bouts of short and long rest, local and locomotor movements. Mice travel ˜330m per day, mainly during the dark hours, while travelling speed is similar through the light-dark cycle. Locomotor bouts are usually <0.2m and <1% are >1m. Tracking revealed also fits of abnormal behaviour. The starting positions of the bouts showed no preference for the rear over the front of the cage floor, while there was a strong bias for the peripheral (75%) over the central floor area. The composition of bouts has a characteristic circadian pattern, however, intrusive husbandry routines increased bout fragmentation by ˜40%. Extracting electrode activations density (EAD) from the raw data yielded results close to those obtained with the tracking algorithm, with 81% of time in rest (<1 EAD s-1) and 19% in PA. Periods ≥40 s of file when no movement occurs and there is no EAD may correspond to periods of sleep (˜59% of file time). We confirm that EAD correlates closely with movement distance (rs>0.95) and the data agreed in ˜97% of the file time. Thus, albeit EAD being less informative it may serve as a proxy for PA and rest, enabling monitoring group housed mice. The data show that increasing density from one female to two males, and further to three male or female mice had the same effect size on EAD (˜2). In contrast, the EAD deviated significantly from this stepwise increase with 4 mice per cage, suggesting a crowdedness stress inducing sex specific adaptations. We conclude that informative metrics on rest and PA can be automatically extracted from the raw data flow in near-real time (< 1 hrs). As discussed, these metrics relay useful longitudinal information to those that use or care for the animals.

Sex-specific effects of Cre expression in Syn1Cre mice

The Cre-loxP system has been used to generate cell-type specific mutations in mice, allowing researchers to investigate the underlying biological mechanisms of disease. However, the Cre-recombinase alone can induce phenotypes that confound comparisons among genotypes if the appropriate Cre control is not included. In this study, we characterised behavioural, morphological and metabolic phenotypes of the pan-neuronal Syn1Cre line. We found that these mice possess intact neuromuscular parameters but have reduced exploratory activity and a male-specific increase in anxiety-like behaviour. Moreover, we observed a male-specific deficit in learning and long-term memory of Syn1Cre mice that could be a result of decreased visual acuity. Furthermore, we found that over-expression of human growth hormone (hGH) from Syn1Cre results in a male-specific reduction in body weight and femur length, potentially through decreased hepatic Igf1 expression. However, metabolic characteristics of Syn1Cre mice such as glucose metabolism, energy expenditure and feeding were unaffected by the presence of Syn1Cre. In conclusion, our data demonstrate that Syn1Cre expression has effects on behavioural and morphological traits. This finding highlights the importance of including the Cre control in all comparisons, while the male-specific effects on some phenotypes highlight the importance of including both sexes.

Dock2 generates characteristic spatiotemporal patterns of Rac activity to regulate neutrophil polarisation, migration and phagocytosis

Introduction

Rac-GTPases and their Rac-GEF activators play important roles in neutrophil-mediated host defence. These proteins control the adhesion molecules and cytoskeletal dynamics required for neutrophil recruitment to inflamed and infected organs, and the neutrophil effector responses that kill pathogens.

Methods

Here, we used live cell TIRF-FRET imaging in neutrophils from Rac-FRET reporter mice with deficiencies in the Rac-GEFs Dock2, Tiam1 or Prex1/Vav1 to evaluate if these proteins activate spatiotemporally distinct pools of Rac, and to correlate patterns of Rac activity with the neutrophil responses they control.

Results

All the GEFs were required for neutrophil adhesion, and Prex1/Vav1 were important during spreading and for the velocity of migration during chemotaxis. However, Dock2 emerged as the prominent regulator of neutrophil responses, as this GEF was required for neutrophil polarisation and random migration, for migration velocity during chemokinesis, for the likelihood to migrate and for the speed of migration and of turning during chemotaxis, as well as for rapid particle engulfment during phagocytosis. We identified characteristic spatiotemporal patterns of Rac activity generated by Dock2 which correlate with the importance of the Rac-GEF in these neutrophil responses. We also demonstrate a requirement for Dock2 in neutrophil recruitment during aseptic peritonitis.

Discussion

Collectively, our data provide a first direct comparison of the pools of Rac activity generated by different types of Rac-GEFs, and identify Dock2 as a key regulator of polarisation, migration and phagocytosis in primary neutrophils.

Grimace scale assessment during Citrobacter rodentium inflammation and colitis development in laboratory mice

Introduction

Bacterial infections and chronic intestinal inflammations triggered by genetic susceptibility, environment or an imbalance in the intestinal microbiome are usually long-lasting and painful diseases in which the development and maintenance of these various intestinal inflammations is not yet fully understood, research is still needed. This still requires the use of animal models and is subject to the refinement principle of the 3Rs, to minimize suffering or pain perceived by the animals. With regard to this, the present study aimed at the recognition of pain using the mouse grimace scale (MGS) during chronic intestinal colitis due to dextran sodium sulfate (DSS) treatment or after infection with Citrobacter rodentium.

Methods

In this study 56 animals were included which were divided into 2 experimental groups: 1. chronic intestinal inflammation (n = 9) and 2. acute intestinal inflammation (with (n = 23) and without (n = 24) C. rodentium infection). Before the induction of intestinal inflammation in one of the animal models, mice underwent an abdominal surgery and the live MGS from the cage side and a clinical score were assessed before (bsl) and after 2, 4, 6, 8, 24, and 48 hours.

Results

The highest clinical score as well as the highest live MGS was detected 2 hours after surgery and almost no sign of pain or severity were detected after 24 and 48 hours. Eight weeks after abdominal surgery B6-Il4/Il10-/- mice were treated with DSS to trigger chronic intestinal colitis. During the acute phase as well as the chronic phase of the experiment, the live MGS and a clinical score were evaluated. The clinical score increased after DSS administration due to weight loss of the animals but no change of the live MGS was observed. In the second C57BL/6J mouse model, after infection with C. rodentium the clinical score increased but again, no increased score values in the live MGS was detectable.

Discussion

In conclusion, the live MGS detected post-operative pain, but indicated no pain during DSS-induced colitis or C. rodentium infection. In contrast, clinical scoring and here especially the weight loss revealed a decreased wellbeing due to surgery and intestinal inflammation.

Rapid ammonia build-up in small individually ventilated mouse cages cannot be overcome by adjusting the amount of bedding

We sought to investigate if varying levels of bedding had an effect on intra-cage ammonia levels in individually ventilated mouse cages (Euro Standard Types II and III). Employing a routine 2 week cage-changing interval, our goal is to keep ammonia levels under 50 ppm. In smaller cages used for breeding or for housing more than four mice, we measured problematic levels of intra-cage ammonia, and a considerable proportion of these cages had ammonia levels at more than 50 ppm toward the end of the cage-change cycle. These levels were not reduced significantly when the levels of absorbent wood chip bedding was either increased or decreased by 50%. The mice in both cage types II and III were housed at comparable stocking densities, yet ammonia levels in larger cages remained lower. This finding highlights the role of cage volume, as opposed to simply the floor space, in controlling air quality. With the current introduction of newer cage designs that employ an even smaller headspace, our study urges caution. With individually ventilated cages, problems with intra-cage ammonia may go undetected, and we may opt to utilize insufficient cage-changing intervals. Few modern cages have been designed to account for the amounts and types of enrichment that are used (and, in parts of the world, mandated) today, adding to the problems associated with decreasing cage volumes.

[Antiviral activity of basidial fungus Inonotus obliquus aqueous extract against SARS-CоV-2 virus (Coronaviridae: Betacoronavirus: Sarbecovirus) in vivo in BALB/c mice model]

INTRODUCTION

The COVID-19 pandemic combined with seasonal epidemics of respiratory viral diseases requires targeted antiviral prophylaxis with restorative and immunostimulant drugs. The compounds of natural origin are low-toxic, but active against several viruses at the same time. One of the most famous compounds is Inonotus obliquus aqueous extract. The fruit body of basidial fungus I. obliquus is called Chaga mushroom. The aim of the work ‒ was to study the antiviral activity of I. obliquus aqueous extract against the SARS-CoV-2 virus in vivo.

MATERIALS AND METHODS

Antiviral activity of I. obliquus aqueous extract sample (#20-17) was analyzed against strain of SARS-CoV-2 Omicron ВА.5.2 virus. The experiments were carried out in BALB/c inbred mice. The SARS-CoV-2 viral load was measured using quantitative real-time PCR combined with reverse transcription. The severity of lung tissue damage was assessed by histological methods.

RESULTS

The peak values of the viral load in murine lung tissues were determined 72 hours after intranasal inoculation at dose of 2,85 lg TCID50. The quantitative real-time PCR testing has shown a significant decrease in the viral load compared to the control group by 4,65 lg copies/ml and 5,72 lg copies/ml in the lung tissue and nasal cavity samples, respectively. Histological methods revealed that the decrease in the number and frequency of observed pathomorphological changes in murine lung tissues depended on the introduction of the compound under study.

CONCLUSION

The results obtained indicate the possibility of using basidial fungus Inonotus obliquus aqueous extract as a preventive agent against circulating variants of SARS-CoV-2 virus.

Transgenic HPV11-E2 protein modulates URR activity in vivo

In vitro experiments have shown that the E2 protein of human papillomaviruses (HPV) binds to the upstream regulatory region (URR) of the viral genome and modulates transcription. Additionally, it seems to be a necessary component for viral DNA replication together with E1. We have developed a transgenic mouse model containing the URR region of the low-risk virus HPV11 that regulates the expression of the lacZ reporter gene. Most interestingly, in these mice, the transgene was exclusively expressed in the bulge region of the hair follicle but not in any other tissues. Further experimental data indicate that in double transgenic mice that also express the HPV11-E2 protein under the control of the Ubiquitin C-promoter, the transcription of the reporter gene is modulated. When E2 is present, the expression of the reporter gene also occurs exclusively in the bulge region of the hair follicles as it does in the single transgenic mice, but the expression of the lacZ driven by the URR is increased and the statistical spread is greater. Even if the expression of the reporter gene occurs in the hair follicles of the dorsal skin of an animal uniform, E2 obviously has the capacity for both to induce and to repress the URR activity in vivo.

Chronic Voluntary Alcohol Consumption Alters Promoter Methylation and Expression of Fgf-2 and Fgfr1

Alcohol abuse accounts for 3.3 million deaths annually, rendering it a global health issue. Recently, fibroblast growth factor 2 (FGF-2) and its target, fibroblast growth factor receptor 1 (FGFR1), were discovered to positively regulate alcohol-drinking behaviors in mice. We tested whether alcohol intake and withdrawal alter DNA methylation of Fgf-2 and Fgfr1 and if there is a correlation regarding mRNA expression of these genes. Blood and brain tissues of mice receiving alcohol intermittently over a six-week period were analyzed using direct bisulfite sequencing and qRT-PCR analysis. Assessment of Fgf-2 and Fgfr1 promoter methylation revealed changes in the methylation of cytosines in the alcohol group compared with the control group. Moreover, we showed that the altered cytosines coincided with binding motives of several transcription factors. We also found that Fgf-2 and Fgfr1 gene expression was significantly decreased in alcohol-receiving mice compared with control littermates, and that this effect was specifically detected in the dorsomedial striatum, a brain region involved in the circuitry of the reward system. Overall, our data showed alcohol-induced alterations in both mRNA expression and methylation pattern of Fgf-2 and Fgfr1. Furthermore, these alterations showed a reward system regional specificity, therefore, resembling potential targets for future pharmacological interventions.

Delivery of B. subtilis into Animal Intestine Using Chitosan-Derived Bioresorbable Gel Carrier: Preliminary Results

The oral delivery of bacteria in the human intestine is of great interest because of its potential to correct the gut microbiota and treat inflammatory bowel diseases. The aim of this study was to evaluate sodium N-(2-sulfonatoethyl)chitosan gel cross-linked with glutaraldehyde as a delivery carrier for probiotic bacteria to the gut using in vitro and in vivo experiments. The bacterial test strain was B. subtilis 20. The cytotoxicity of the gel was evaluated via cell culture using flow cytometry and light microscopy. The gel as a delivery system was assessed by the dye release in medium with different pH levels in vitro, and by bacterial titer monitoring in mouse feces using the microbiology method in vivo. Results of an in vitro experiment showed that tested gel has no cytotoxicity. The use of gel as a carrier for bacterial delivery into the intestine was more effective than oral gavage of bacterial suspension. Therefore, gel delivery of bacteria decreased the titer level by up to two times. However, a gavage of bacterial suspension decreased the titer level by over 200 times. Tested gel has the potential to be a carrier for the safe delivery of bacteria to the intestine through the stomach, reducing the rate of the elimination of probiotic bacteria from the intestine.

Feasibility of pair-housing of rats after cranial implant surgery

Rat models employing cranial implants are increasingly employed to facilitate neural stimulation and recording in freely moving animals. Due to possible damage to wound, implant or attached devices, rats with cranial implants are traditionally housed singly, and little information is available on group- or pair-housing. Here we describe a protocol for pair-housing rats following cranial implant surgery and describe our experience with pair-housing during post-surgical recovery and up to 16 weeks following surgery.Thirty-six adult Wistar rats of both sexes were implanted with deep brain stimulation electrodes. Ten rats were equipped with an additional wireless headstage. Rats were housed in stable pairs before surgery and re-introduced 0-18 h post-surgery. Rat grimace scores did not indicate pain after conclusion of the analgesia protocol, physiological parameters were in the normal range three days post-surgery and weight loss did not exceed 10%. Rats with a cement cap only were pair-housed continuously without damage to the headcap. Rats carrying an additional fragile headstage had to be separated during lights-off periods to prevent headstage damage but could be pair-housed during lights-on periods.Pair-housing is a feasible and effective method to facilitate the rats' need for social companionship following cranial implant surgery.

Evaluation of exhaust air dust polymerase chain reaction as a supplement method for soiled bedding sentinel monitoring in specific pathogen free mouse facility using two different individually ventilated cage racks

Health monitoring is essential for ensuring animal health and reliable research results. Each animal facility should establish adequate health monitoring methods, and microbiological quality control should be implemented through regular health surveillance. Recently, specific pathogen free (SPF) mice have been housed in individually ventilated cage (IVC) racks in the majority of mouse facilities globally, and health monitoring is implemented using a soiled bedding sentinel (SBS). Even though SBS monitoring is a standard method, it has a limitation in that some pathogens are not sufficiently transmitted to the sentinel housed in the IVC. The exhaust air dust polymerase chain reaction (EAD PCR) method has been reported to be a reliable complementary method to SBS monitoring based on research findings. In Korea, health monitoring programs using EAD PCR have not yet been applied to laboratory animal facilities. The microbiological status of mouse colonies housed in the two IVC racks was compared using SBS and EAD PCR monitoring in our SPF mouse facility. Except for Helicobacter spp. and Staphylococcus aureus, the detection of 16 pathogens did not differ between the two methods. In the detection of Helicobacter spp., EAD PCR was found to be more sensitive than SBS. Helicobacter spp. were not found by SBS, whereas four S. aureus positive samples were detected by either SBS or EAD PCR test. According to our findings, EAD PCR can be used as a supplement to SBS monitoring. Moreover, EAD PCR can reduce the number of animals used, making it a 3R (Replacement, Reduction, Refinement)-consistent method.

The Genetic Background Is Shaping Cecal Enlargement in the Absence of Intestinal Microbiota

Germ-free (GF) rodents have become a valuable tool for studying the role of intestinal microbes on the host physiology. The major characteristic of GF rodents is an enlarged cecum. The accumulation of mucopolysaccharides, digestion enzymes and water in the intestinal lumen drives this phenotype. Microbial colonization normalizes the cecum size in ex-GF animals. However, whether strain genetics influences the cecal enlargement is unknown. Here we investigated the impact of mouse genetic background on the cecal size in five GF strains frequently used in biomedical research. The cecal weight of GF mice on B6 background (B6J and B6N) represented up to 20% of total body weight. GF NMRI and BALBc mice showed an intermediate phenotype of 5-10%, and those on the C3H background of up to 5%. Reduced cecal size in GF C3H mice correlated with decreased water content, increased expression of water transporters, and reduced production of acidic mucins, but was independent of the level of digestive enzymes in the lumen. In contrast, GF B6J mice with greatly enlarged cecum showed increased water content and a distinct metabolic profile characterized by altered amino acid and bile acid metabolism, and increased acidic mucin production. Together, our results show that genetic background influences the cecal enlargement by regulating the water transport, production of acidic mucins, and metabolic profiles.

The Effect of Dietary Phospholipids on the Ultrastructure and Function of Intestinal Epithelial Cells

Dietary composition substantially determines human health and affects complex diseases, including obesity, inflammation and cancer. Thus, food supplements have been widely used to accommodate dietary composition to the needs of individuals. Among the promising supplements are dietary phospholipids (PLs) that are commonly found as natural food ingredients and as emulsifier additives. The aim of the present study was to evaluate the effect of major PLs found as food supplements on the morphology of intestinal epithelial cells upon short-term and long-term high-dose feeding in mice. In the present report, the effect of short-term and long-term high dietary PL content was studied in terms of intestinal health and leaky gut syndrome in male mice. We used transmission electron microscopy to evaluate endothelial morphology at the ultrastructural level. We found mitochondrial damage and lipid droplet accumulation in the intracristal space, which rendered mitochondria more sensitive to respiratory uncoupling as shown by a mitochondrial respiration assessment in the intestinal crypts. However, this mitochondrial damage was insufficient to induce intestinal permeability. We propose that high-dose PL treatment impairs mitochondrial morphology and acts through extensive membrane utilization via the mitochondria. The data suggest that PL supplementation should be used with precaution in individuals with mitochondrial disorders.