Specific Pathogen-free Conditions Research Articles

Housing RCS rats under specific pathogen-free conditions mildly ameliorates retinal degeneration and alters intestine microbiota

Retinitis pigmentosa (RP) is a genetic blinding disease with over 80 causative genes. Disease progression varies between patients with similar genetic backgrounds. We assessed the association between environment, gut microbiota, and retinal degeneration in the RP rat model Royal College of Surgeons (RCS). The rats were born and raised for two generations under specific pathogen-free (SPF, n = 69) or non-SPF conditions (n = 48). At the age of four weeks, SPF rats had significantly shorter dark-adapted a-wave and dark and light-adapted b-wave implicit times by electroretinogram (p = 0.014, p = 9.5*10−6, p = 0.009, respectively). The SPF rats had significantly less photoreceptor apoptosis at ages four, eight, and twelve weeks (all p < 0.022), significantly thicker debris zone at age 14 weeks, and smaller hypofluorescent lesions in SPF rats at ages 10–16 weeks, especially in the inferior retina. The non-SPF rats had significantly higher microbiota alpha diversity (p = 0.037) and failed to present the age-related maturation of Proteobacteria, Spirochaetes, Actinobacteria, and Bacteroidetes seen in SPF conditions. Specific microbial amplicon sequence variants were reduced in rats with more severe retinal degeneration. Our data suggest an environmental effect on retinal deterioration in RCS rats. These findings may lead to the development of novel microbiome-related interventions for retinal degeneration.

The Influence of Specific Pathogen-Free and Conventional Environments on the Hematological Parameters of Pigs Bred for Xenotransplantation.

Blood analysis plays a pivotal role in assessing the health of laboratory animals, including pigs. This study investigated the hematological profiles of transgenic pigs of the MGH breed for xenotransplantation, focusing on the effect of housing conditions on blood parameters. A cohort of pigs was longitudinally monitored from 6 to 18 months of age in both conventional and specific pathogen-free (SPF) environments. Red blood cells (RBCs), hemoglobin (HGB), and white blood cells (WBCs) were analyzed using standardized hematology analyzers. The results revealed that RBC and HGB levels were consistently higher in SPF-housed pigs. Notably, WBC counts were significantly lower in SPF-housed pigs, suggesting that reduced pathogen exposure under SPF conditions effectively diminished immune system activation. These findings raise a novel question as to whether distinct hematological parameters of specific and/or designated PF pigs would be advantages for the success of clinical xenotransplantation trials.

Influence of Age on Leukemia Mortality Associated with Exposure to γ rays and 2-MeV Fast Neutrons in Male C3H Mice.

The relative biological effectiveness (RBE) of densely ionizing radiation can depend on the biological context. From a radiological perspective, age is an important factor affecting health risks of radiation exposure, but little is known about the modifying impact of age on the effects of densely ionizing radiation. Herein, we addressed the influence of age on leukemogenesis induced by accelerator-generated fast neutrons (mean energy, ∼2 MeV). Male C3H/HeNrs mice were exposed to 137Cs γ rays (0.2-3.0 Gy) or neutrons (0.0485-0.97 Gy, γ ray contamination 0.0105-0.21 Gy) at 1, 3, 8, or 35 weeks of age and observed over their lifetimes under specific pathogen-free conditions. Leukemia and lymphoma were diagnosed pathologically. Hazard ratio (HR) and RBE for myeloid leukemia mortality as well as the age dependence of these two parameters were modeled and analyzed using Cox regression. Neutron exposure increased HR concordant with a linear dose response. The increase of HR per dose depended on age at exposure, with no significant dose dependence at age 1 or 3 weeks but a significant increase in HR of 5.5 per Gy (γ rays) and 16 per Gy (neutrons) at 8 weeks and 5.8 per Gy (γ rays) and 9 per Gy (neutrons) at 35 weeks. The RBE of neutrons was 2.1 (95% confidence interval, 1.1-3.7), with no dependence on age. The development of lymphoid neoplasms was not related to radiation exposure. The observed increasing trend of radiation-associated mortality of myeloid leukemia with age at exposure supports previous epidemiological and experimental findings. The results also suggest that exposure at the susceptible age of 8 or 35 weeks does not significantly influence the RBE value for neutrons for induction of leukemia, unlike what has been documented for breast and brain tumors.

Structural and Functional Differences in Small Intestinal and Fecal Microbiota: 16S rRNA Gene Investigation in Rats.

To compare the differences in floral composition and functions between the two types of microbiota, ileal contents and feces were collected from Sprague Dawley (SD) rats fed in a conventional or specific-pathogen free (SPF) environment and rats fed a high-fat diet (HFD), and the V3-V4 region of the 16S ribosomal ribonucleic acid (rRNA) gene in these rats was then amplified and sequenced. Compared with feces, about 60% of the bacterial genera in the ileum were exclusive, with low abundance (operational taxonomic units (OTUs) < 1000). Of bacteria shared between the ileum and feces, a few genera were highly abundant (dominant), whereas most had low abundance (less dominant). The dominant bacteria differed between the ileum and feces. Ileal bacteria showed greater β-diversity, and the distance between in-group samples was nearer than that between paired ileum-feces samples. Moreover, the ileum shared various biomarkers and functions with feces (p < 0.05). The HFD and SPF conditions had a profound influence on α-diversity and abundance but not on the exclusive/shared features or β-diversity of samples. The present findings suggested that, under conventional circumstances, fecal bacteria can represent approximately 40% of the low abundant ileal bacterial genera and that dominant fecal bacteria failed to represent the ileal dominant flora. Moreover, fecal flora diversity does not reflect β-diversity in the ileum.

B cell senescence promotes age-related changes in oral microbiota.

In recent years, there has been increasing attention towards understanding the relationship between age-related alterations in the oral microbiota and age-associated diseases, with reports emphasizing the significance of maintaining a balanced oral microbiota for host health. However, the precise mechanisms underlying age-related changes in the oral microbiota remain elusive. We recently reported that cellular senescence of ileal germinal center (GC) B cells, triggered by the persistent presence of commensal bacteria, results in diminished IgA production with aging and subsequent alterations in the gut microbiota. Consequently, we hypothesize that a similar phenomenon may occur in the oral cavity, potentially contributing to age-related changes in the oral microbiota. Examination of p16-luc mice, wherein the expression of the senescent cell marker p16INK4a can be visualized, raised under specific pathogen-free (SPF) or germ-free (GF) conditions, indicated that, unlike ileal GC B cells, the accumulation of senescent cells in GC B cells of cervical lymph nodes increases with age regardless of the presence of commensal bacteria. Furthermore, longitudinal studies utilizing the same individual mice throughout their lifespan revealed concurrent age-related alterations in the composition of the oral microbiota and a decline in salivary IgA secretion. Further investigation involving Rag1-/- mice transplanted with B cells from wild-type or p16INK4a and p21Waf1/Cip1 -double knockout mice unveiled that B cell senescence leads to reduced IgA secretion and alteration of the oral microbiota. These findings advance our understanding of the mechanism of age-associated changes in the oral microbiota and open up possibilities of their control.

P-015 Impaired spermatogenesis in colitis: the role of interferon-γ mediated ferroptosis in sertoli cells by colitic CD4+ T cells

Abstract Study question Does colitis have an impact on spermatogenesis and what could be the potential mechanism? Summary answer Colitis causes sertoli cell ferroptosis and disrupts spermatogenesis in mice due to the migration of colitic CD4+ T cells that produce interferon-γ. What is known already In recent years, there has been a significant increase in rheumatic and inflammatory diseases. Epidemiological data reveals that dysregulated immune conditions can directly or indirectly impact male fertility and sexual function in patients of reproductive age. Inflammatory bowel disease (IBD), which encompasses Crohn’s disease and ulcerative colitis, is a chronic, recurring gastrointestinal inflammatory disorder characterized by bloody stools and weight loss. A study from a Swedish national cohort showed that IBD patients had diminished sperm fertility and increased sperm DNA fragmentation compared to healthy individuals. However, the precise mechanisms underlying male fertility problems in IBD remain unclear. Study design, size, duration In this study, C57BL/6 mice were kept under specific pathogen-free conditions. A murine colitis model that simulates human colitis histological features and symptoms was created using Dextran Sulfate Sodium (DSS). To establish the model, 2-2.5% DSS was added to the mice’s drinking water from days 0 to 7, followed by a three-day recovery period. Participants/materials, setting, methods Testis, epididymis and colon sections were stained with hematoxylin and eosin for histological analysis. The localization and phenotype of infiltrated lymphocytes in epididymis and testis were studied by immunostaining and flow cytometry. Sperm functions including motility, viability, and DNA integrity were assessed by standard assays. Iron, malondialdehyde, and reactive oxygen species (ROS) levels were analysed by commercial kit. Main results and the role of chance Colitis was found to impair male fertility in DSS-induced colitic mice, causing testis and epididymis tissue damage along with inflammatory cell infiltration. Colitis altered the immune cell phenotypes in the testis and epididymis. The proportion and absolute cell count of CD4+ T cells and CD19+ B cells increased after colon inflammation. Testicular sertoli cells in colitic mice exhibited ferroptosis, characterized by increased levels of iron deposition, malondialdehyde, and ROS. We assessed sperm parameters from the cauda epididymis of mice. Compared to the control group, there were significant reduction in sperm concentration, motility, viability and DNA integrity in the group with murine colitis induction. Consistently, we observed lower numbers of active pups from the fathers of the colitis group compared to control mice. CD4+ T cells with interferon-γ producing capabilities accumulated in the testes of colitis mice. Leukocyte flow cytometric analysis and parabiotic mouse model further demonstrated that colitis promoted pathogenic CD4+ T cells migration to the testis through circulation. The treatment of anti-CD4 antibody, anti-interferon-γ antibody or ferroptosis inhibitor can attenuate the colitis-associated testis pathologies. Limitations, reasons for caution Our study was conducted exclusively in mice. The pathogenic effect and the corresponding mechanism of colitis on male fertility in humans still needs to be confirmed. Wider implications of the findings Our team identified the mechanism linking dysregulated gut immune cell activity to testicular dysfunction. By identifying specific molecules on colitic immune cells, which allow their infiltration into the testis, may pave the way for a new therapeutic approach potentially improving the prognosis of colitis and related fertility impairments. Trial registration number not applicable

Administration of a bacterial lysate to the airway compartment is sufficient to inhibit allergen-induced lung eosinophilia in germ-free mice.

The nexus between eosinophils and microbes is attracting increasing attention. We previously showed that airway administration of sterile microbial products contained in dust collected from traditional dairy farms virtually abrogated bronchoalveolar lavage (BAL) eosinophilia and other cardinal asthma phenotypes in allergen-sensitized specific pathogen-free (SPF) mice. Interestingly, comparable inhibition of allergen-induced BAL eosinophilia and promotion of airway barrier integrity were found upon administration of a sterile, pharmacological-grade bacterial lysate, OM-85, to the airway compartment of allergen-sensitized SPF mice. Here, we asked whether intrinsic properties of airway-delivered microbial products were sufficient to inhibit allergic lung inflammation or whether these effects were mediated by reprogramming of the host microbiota. We compared germ-free (GF) mice and offspring of GF mice associated with healthy mouse gut microbiota and maintained under SPF conditions for multiple generations (Ex-GF mice). These mice were treated intranasally with OM-85 and evaluated in the ovalbumin and Alternaria models of allergic asthma focusing primarily on BAL eosinophilia. Levels of allergen-induced BAL eosinophilia were comparable in GF and conventionalized Ex-GF mice. Airway administration of the OM-85 bacterial lysate was sufficient to inhibit allergen-induced lung eosinophilia in both Ex-GF and GF mice, suggesting that host microbiota are not required for the protective effects of bacterial products in these models and local airway exposure to microbial products is an effective source of protection. OM-85-dependent inhibition of BAL eosinophilia in GF mice was accompanied by suppression of lung type 2 cytokines and eosinophil-attracting chemokines, suggesting that OM-85 may work at least by decreasing eosinophil lung recruitment.

A194 EARLY LIFE WESTERN-TYPE DIET ACCELERATES THE ONSET OF MURINE IL-10 KO COLITIS

Abstract Background Early life is a critical time for gut microbiome and immune development, including the establishment of proper host-microbe interactions. While exposures to western world environmental factors are associated with inflammatory bowel disease (IBD) susceptibility, the link between environment in early life and later disease onset is unclear. One of the most important western world environmental factors is diet, which can distinctly alter the gut microbiome. We believe an early life western-type diet (WD) can affect disease progression in a murine IL-10 KO colitis model through dysregulated T-cell responses against the microbiome. Aims We aimed to characterize how an early life WD given to IL-10 KO mice would affect colitis development and the gut microbiome. Methods IL-10 KO mice were housed in specific pathogen free conditions and fed normal chow (NC) or WD ad libitum, either between days 10 to 35 (early WD, eWD) or days 35 to 60 (adolescent WD, aWD). Stool was collected from mice at days 35, 56, and 84 for lipocalin-2 (LCN-2) and 16S rDNA sequencing. Mice were sacrificed at day 84, assessing mesenteric lymph node weight, gene expression, colon damage by histopathology, and colon lamina propria leukocyte (LPL) phenotype and cytokine expression by flow cytometry. Results Compared to NC and aWD, the eWD fed IL-10 KO mice displayed increased fecal LCN-2 at days 56 and 84, indicating greater inflammation. At sacrifice, eWD fed mice had larger mesenteric lymph nodes and more significant colon damage by histopathological scoring. Colon LPL preparations showed that eWD fed IL-10 KO mice had higher proportions and absolute numbers of effector and regulatory T-cells. Additionally, higher proportions and absolute numbers of those T-cells were IFNγ+, IL-17A+, and IL-22+. qPCR of distal colon tissue revealed increased gene expression of innate and type 3 proinflammatory cytokines such as Il1b, Tnfα, and Il23, while showing no change in Il6 and Il4. Taxa positively associated with WD were able to establish a persistent niche in eWD fed mice but not in aWD fed mice. An increase in only one specific taxon was associated with eWD at all timepoints while also most strongly correlating with inflammatory markers. Conclusions This data suggests that eWD feeding during gut microbiome and immune development is uniquely capable of increasing long-term susceptibility to intestinal inflammation in IL-10 KO mice. This appears to be associated with persistent colonization of potentially more inflammatory taxa. This work provides insight into the potential role of early life environmental risk factors, i.e. WD, in the later development of IBD. Funding Agencies CAG, CIHRUniversity of Toronto, Taconic Biosciences

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.

MiR-410 Regulates Helper T Cell Differentiation in Ovalbumin-Induced Asthma through the PI3K-AKT-VEGF Signaling Pathway

Introduction: Asthma has been attributed to Th1/Th2 imbalance and inappropriate Th2 responses to environmental allergens. MicroRNAs (miRNAs), 21 to 23 RNA molecules, are first found in mammals and have been implicated in various biological activities. Our previous study found that miR-410 effectively ameliorates airway inflammation in the ovalbumin (OVA)-induced asthma murine model. However, the role of miR-410 in regulating helper T (Th) cell differentiation is not clear. In the present study, we aimed to explore the regulatory effects of miR-410 on the differentiation of Th cells through both in vivo and in vitro studies. Methods: Dual-luciferase reporter assay was used to find if miR-410 has any direct binding position with VEGF mRNAs. PBMC and CD4+ T cells were isolated and stimulated with OVA. The miR-410 mimics and inhibitors were transfected into CD4+ T cells. The differentiation of Th cells was evaluated by enzyme-linked immunosorbent assay (ELISA) for the concentration of IL-4, IFN-γ, and TGF-β levels in supernatants. Western Blot was used to detect protein expression and phosphorylation of PI3K and AKT. BALB/c mice were kept in a specific pathogen-free condition and received sterile OVA-free food and water. OVA-induced asthmatic mice model was established. ELISA was used to measure the bronchoalveolar lavage fluid (BALF) concentrations of IL-4, IFN-γ, TGF-β, and VEGF. Hematoxylin and eosin staining and immunohistochemical staining were conducted to analyze inflammatory cell infiltration, pathological changes, and the expression of VEGF. Results: Dual-luciferase reporter assay showed that miR-410 has no direct binding position with VEGF mRNAs. In the OVA-primed mononuclear cells compared to normal cells, IFN-γ and TGF-β were decreased while IL-4 and VEGF were increased. This change was reversed while miRNA-410 mimics were transfected into CD4+ T cells. Besides, the OVA-primed CD4+ T cells treated with miR-410 decrease the proliferation of cytokine of Th2 cells as well as phosphorylation of PI3K, and AKT. In OVA-induced asthma mice, IFN-γ and TGF-β were decreased in BALF while the IL-4 and VEGF were increased. OVA-induced mice with asthma treated with miR-410 mimics showed marked reductions in the infiltration of inflammatory cells as well as IL-4 and VEGF in BALF. The immunohistochemical staining of the expression of VEGF also decreased in OVA-induced asthma mice with the instillation of miR-410. Conclusions: In this study, we revealed that miR-410 could regulate the differentiation of Th cells via the PI3K-AKT-VEGF signaling pathway in asthma.

Effects of herbal tea (Platostoma palustre) on the Hyperlipidemia in vivo

Effects of herbal tea (Platostoma palustre) on the Hyperlipidemia in vivo

The promoting effect of modified Dioscorea pills on vascular remodeling in chronic cerebral hypoperfusion via the Ang/Tie signaling pathway.

The objective of this study was to investigate the effect of modified Dioscorea pills (MDP) on microcirculatory remodeling in the hippocampus of rats with chronic cerebral hypoperfusion (CCH) through the angiopoietin (Ang)/tyrosine kinase receptor tyrosine kinase with immunoglobulin-like and EGF-like domains (Ang receptor) 2 (Tie-2) signaling pathways, which may underlie the cognitive improvement observed in CCH rats. Forty male Sprague-Dawley rats raised under specific pathogen-free conditions were randomly divided into three groups: control group (10 rats), model group (15 rats), and MDP group (15 rats). The rats in the model group and MDP group underwent bilateral common carotid artery occlusion using the 2-vessel occlusion (2-VO) method to induce CCH. Rats in the control group underwent the same surgical procedures as those in the model group, except for ligation and occlusion of the carotid arteries. After 1 week of 2-VO, rats in the MDP group were administered MDP condensed decoction intragastrically at a dose of 1 ml/100 g body weight (prepared by the Preparation Room of Hubei Provincial Hospital of Traditional Chinese Medicine) for 45 days, while rats in the other two groups received normal saline intragastrically with the same dose and duration as the MDP group. After the intervention, all rats were euthanized, and brain perfusion was performed to obtain the hippocampal tissue for analysis. Immunohistochemical staining for CD43 was performed to assess microvessel density (MVD); western blot and the reverse transcription-polymerase chain reaction (RT-PCR) were used to analyze the expression of proteins and genes in angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), Tie-2, and vascular endothelial growth factor (VEGF) proteins and genes in the hippocampal tissue and compute the Ang-1/Ang-2 ratio. MDP treatment reduced neuronal loss and promoted restoration of the damaged hippocampal structure in CCH rats. The model group showed significantly higher MVD (14.93 ± 1.92) compared to the control group (5.78 ± 1.65) (P < 0.01), whereas MDP treatment further increased MVD (21.19 ± 2.62). Western blot and RT-PCR analysis revealed that CCH significantly increased the expression of Ang-1, Ang-2, Tie-2, and VEGF proteins and genes, while MDP treatment further significantly upregulated the expression of these proteins and genes. In addition, MDP significantly elevated the gene and protein expression of the Ang-1/Ang-2 ratio compared to the control group (P = 0.041, P = 0.029). CCH induces microvascular neogenesis in the hippocampus, and MDP promotes angiogenesis and microcirculation remodeling in CCH rats via the Ang/Tie signaling pathway, which may be an important mechanism for its restorative effects on hippocampal perfusion and improvement of cognitive function in CCH rats.

IL-1β transgenic mouse model of inflammation driven esophageal and oral squamous cell carcinoma

Chronic inflammation is integral to the development of esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC), although the latter has not been associated with reflux esophagitis. The L2-IL-1β transgenic mice, expressing human interleukin (IL)-1β in the oral, esophageal and forestomach squamous epithelia feature chronic inflammation and a stepwise development of Barrett’s esophagus-like metaplasia, dysplasia and adenocarcinoma at the squamo-columnar junction. However, the functional consequences of IL-1β-mediated chronic inflammation in the oral and esophageal squamous epithelia remain elusive. We report for the first time that in addition to the previously described Barrett’s esophagus-like metaplasia, the L2-IL-1β mice also develop squamous epithelial dysplasia with progression to squamous cell carcinoma (SCC) in the esophagus and the tongue. L2-IL-1β showed age-dependent progression of squamous dysplasia to SCC with approximately 40% (n = 49) and 23.5% (n = 17) incidence rates for esophageal and tongue invasive SCC respectively, by 12–15 months of age. Interestingly, SCC development and progression in L2-IL-1β was similar in both Germ Free (GF) and Specific Pathogen Free (SPF) conditions. Immunohistochemistry revealed a T cell predominant inflammatory profile with enhanced expression of Ki67, Sox2 and the DNA double-strand break marker, γ-H2AX, in the dysplastic squamous epithelia of L2-IL-1β mice. Pro-inflammatory cytokines, immunomodulatory players, chemoattractants for inflammatory cells (T cells, neutrophils, eosinophils, and macrophages) and oxidative damage marker, iNOS, were significantly increased in the esophageal and tongue tissues of L2-IL-1β mice. Our recent findings have expanded the translational utility of the IL-1β mouse model to aid in further characterization of the key pathways of inflammation driven BE and EAC as well as ESCC and Oral SCC.

Sequential Early-Life Infections Alter Peripheral Blood Transcriptomics in Aging Female Mice but Not the Response to De Novo Infection with Influenza Virus or M. tuberculosis.

To determine the impact of accumulating Ag exposure on immunity in the aging mouse, and to develop a model more relevant to humans who are exposed to multiple pathogens during life, we sequentially infected young female mice with four distinct pathogens at 8-wk intervals: murine γ-herpesvirus 68, Sendai virus, murine CMV, and Heligmosomoides polygyrus. Mock-infected mice received PBS. After aging the sequentially infected and mock-infected mice to 18-25 mo under specific pathogen-free conditions, we analyzed multiple immune parameters. We assessed transcriptional activity in peripheral blood, T cell phenotype, the diversity of influenza epitopes recognized by CD8 T cells, and the response of the animals to infection with influenza virus and Mycobacterium tuberculosis. Our data show enhanced transcriptional activation in sequentially infected aged mice, with changes in some CD8 T cell subsets. However, there was no measurable difference in the response of mock-infected and sequentially infected aged mice to de novo infection with either influenza virus or M. tuberculosis at 18-21 mo. Unexpectedly, a single experiment in which 25-mo-old female mice were challenged with influenza virus revealed a significantly higher survival rate for sequentially infected (80%) versus mock-infected (20%) mice. These data suggest that although exposure to a variety of pathogen challenges in the mouse model does not overtly impact cellular markers of immunity in aged female mice following de novo respiratory infection, subtle changes may emerge in other compartments or with increasing age.

Spontaneous episodic inflammation in the intestines of mice lacking HNF4A is driven by microbiota and associated with early life microbiota alterations.

The inflammatory bowel diseases (IBD) occur in genetically susceptible individuals who mount inappropriate immune responses to their microbiota leading to chronic intestinal inflammation. Whereas IBD clinical presentation is well described, how interactions between microbiota and host genotype impact early subclinical stages of the disease remains unclear. The transcription factor hepatocyte nuclear factor 4 alpha (HNF4A) has been associated with human IBD, and deletion of Hnf4a in intestinal epithelial cells (IECs) in mice (Hnf4aΔIEC) leads to spontaneous colonic inflammation by 6-12 mo of age. Here, we tested if pathology in Hnf4aΔIEC mice begins earlier in life and if microbiota contribute to that process. Longitudinal analysis revealed that Hnf4aΔIEC mice reared in specific pathogen-free (SPF) conditions develop episodic elevated fecal lipocalin 2 (Lcn2) and loose stools beginning by 4-5 wk of age. Lifetime cumulative Lcn2 levels correlated with histopathological features of colitis at 12 mo. Antibiotic and gnotobiotic tests showed that these phenotypes in Hnf4aΔIEC mice were dependent on microbiota. Fecal 16S rRNA gene sequencing in SPF Hnf4aΔIEC and control mice disclosed that genotype significantly contributed to differences in microbiota composition by 12 mo, and longitudinal analysis of the Hnf4aΔIEC mice with the highest lifetime cumulative Lcn2 revealed that microbial community differences emerged early in life when elevated fecal Lcn2 was first detected. These microbiota differences included enrichment of a novel phylogroup of Akkermansia muciniphila in Hnf4aΔIEC mice. We conclude that HNF4A functions in IEC to shape composition of the gut microbiota and protect against episodic inflammation induced by microbiota throughout the lifespan. IMPORTANCE The inflammatory bowel diseases (IBD), characterized by chronic inflammation of the intestine, affect millions of people around the world. Although significant advances have been made in the clinical management of IBD, the early subclinical stages of IBD are not well defined and are difficult to study in humans. This work explores the subclinical stages of disease in mice lacking the IBD-associated transcription factor HNF4A in the intestinal epithelium. Whereas these mice do not develop overt disease until late in adulthood, we find that they display episodic intestinal inflammation, loose stools, and microbiota changes beginning in very early life stages. Using germ-free and antibiotic-treatment experiments, we reveal that intestinal inflammation in these mice was dependent on the presence of microbiota. These results suggest that interactions between host genotype and microbiota can drive early subclinical pathologies that precede the overt onset of IBD and describe a mouse model to explore those important processes.

The gut microbiome regulates astrocyte reaction to Aβ amyloidosis through microglial dependent and independent mechanisms

BackgroundPrevious studies show that antibiotic-mediated (abx) alteration of the gut microbiome (GMB) results in a reduction of amyloid beta (Aβ) plaques and proinflammatory microglial phenotype in male APPPS1-21 mice. However, the effect of GMB perturbation on astrocyte phenotypes and microglial-astrocyte communication in the context of amyloidosis has not been examined.MethodsTo study whether the GMB modulates astrocyte phenotype in the context of amyloidosis, APPPS1-21 male and female mice were treated with broad-spectrum abx leading to GMB perturbation. GFAP + astrocytes, plaque-associated astrocytes (PAA), PAA morphological parameters, and astrocyte complement component C3 levels were quantified using a combination of immunohistochemistry, immunoblotting, widefield microscopy, and confocal microscopy. Furthermore, these same astrocyte phenotypes were assessed in abx-treated APPPS1-21 male mice that received either fecal matter transplant (FMT) from untreated APPPS1-21 male donors to restore their microbiome or vehicle control. To assess complete absence of the GMB on astrocyte phenotypes, the same astrocyte phenotypes were quantified in APPPS1-21 male mice raised in germ-free (GF) or specific-pathogen free conditions (SPF). Lastly, we assessed whether microglia are necessary for abx-induced astrocyte phenotypes by depleting microglia in APPPS1-21 male mice via treatment with a colony-stimulating factor 1 receptor (CSF1R) inhibitor (PLX5622) and vehicle control or PLX5622 and abx.ResultsHerein, we demonstrate that postnatal treatment of male APPPS1-21 mice with broad-spectrum abx leading to GMB perturbation reduces GFAP + reactive astrocytes and PAAs, suggesting that the GMB plays a role in regulating reactive astrocyte induction and recruitment to Aβ plaques. Additionally, we show that compared to controls, PAAs in abx-treated male APPPS1-21 mice exhibit an altered morphology with increased number and length of processes and reduced astrocytic complement C3, consistent with a homeostatic phenotype. GFAP + astrocyte reduction, PAA reduction, astrocyte morphological changes, and C3 levels are restored when abx-treated mice are subject to FMT from untreated APPPS1-21 male donor mice. Next, we found that APPPS1-21 male mice raised in GF conditions have similar astrocyte phenotypes as abx-treated male APPPS1-21 male mice. Correlational analysis revealed that pathogenic bacteria depleted by abx correlate with GFAP + astrocytosis, PAAs, and astrocyte morphological changes. Finally, we determined that abx-mediated reduction in GFAP + astrocytosis, PAAs, and astrocytic C3 expression is independent of microglia. However, abx-induced astrocyte morphological alterations are dependent on the presence of microglia, suggesting that there is both microglial independent and dependent GMB control of reactive astrocyte phenotypes.ConclusionsWe show for the first time, in the context of amyloidosis, that the GMB plays an important role in controlling reactive astrocyte induction, morphology, and astrocyte recruitment to Aβ plaques. GMB regulation of these astrocytic phenotypes is both independent and dependent on microglia.

P-266 Study on the mechanisms of ovol1/2 during the morula-to-blastocyst transition

Abstract Study question Screen the key gene groups that determine the development of blastocyst. Explore the effect of ovol1/2 gene on early embryonic development. Summary answer We founded that there were insufficient activation of the Major ZGA genes in the AE group,and focused on candidate gene ovol1/2. What is known already At present, the clinical success rate of assisted reproductive technology (ART) is less than 50%. A large number of embryos cultured in vitro can not develop to blastocyst, and there are cleavage or morula stage arrest. The developmental arrest of preimplantation embryos is an important reason for treatment failure of infertile patients. However, the cause of early embryonic development arrest is not clear, and there is also a lack of effective methods to improve embryo quality. Study design, size, duration In this study, fertilized embryos were obtained through ICSI and a single cell from eight-cell embryo was biopsied through micromanipulation for single-cell RNA sequencing (scRNA-seq). Subsequently, we tracked the developmental potential of remaining cells and divided them into high-quality blastocyst(Bla) group and high-quality eight-cell failed blastocyst formation(arrest embryo, AE) group. In addition,we employed a RNAi approach to study the function of candidate gene ovol1/2, by injecting ovol1/2-targeting small interfering RNAs (siovol1/2) into wild-type (WT) zygotes. Participants/materials, setting, methods The study collected 21 human blastocysts and 5 arrest embryos. Human immature oocytes from ICSI treatments were clinically discarded and donated by women after signing informed consent by donors. C57B6 background mouse strains were used in this study. Mice were maintained under specific pathogen free conditions in a controlled environment of 20–22 °C,with a 12/12 h light/dark cycle, 50–70% humidity, and food and water provided. Main results and the role of chance The results showed that the gene expression of embryos in AE group was significantly different from that of Bla group: 79.5% of differential expression genes were down-regulated, including 48.3% of the Major ZGA gene. Then we focused on the candidate gene ovol1/2. When ovol1/2 were knocked down alone, there was no significant difference in the development rate of embryos from 2-cell to blastocyst between knockdown group and normal control group. When ovol1/2 were knocked down at the same time, there was no significant difference in the development rate of embryos among three groups before the morula stage. But in the morula developed to the blastocyst stage, there were significant differences among three groups of embryos: about 73% of embryos in the normal control group formed blastocyst; about 39% of the embryos in the low-dose knockdown group; the high-dose knockdown group embryos were all arrested in the morula stage. Further investigation revealed that the number of inner cell mass(ICM) cells in low-dose knockdown group did not change significantly, while the number of trophoblastic ectoderm(TE) cells significantly decreased. In addition, the TE functions of low-dose knockdown group such as blastocyst cavity size, paved area, hatching and adhesion rate were damaged. Limitations, reasons for caution Further research of the mechanisms is needed. Wider implications of the findings This is significant to understand molecular mechanisms of early embryonic development, and will provide important theoretical basis for clinical diagnosis and intervention of embryonic development arrest. Our study provides clues for the causes of abnormal blastocyst formation and new ideas for possible clinical improvements in the success rate of ART. Trial registration number not applicable

Intestinal epithelial transcription factor HNF4A protects against microbiota dependent colitis and expansion of Akkermansia muciniphila

Development of the inflammatory bowel diseases (IBD) has been linked to altered homeostatic relationships between the intestine and the microbiota it harbors. However early preclinical stages of IBD remain poorly understood, especially with respect to host-microbiota interactions. The nuclear receptor transcription factor Hepatocyte nuclear factor 4 alpha (HNF4A) has important roles in intestinal epithelial cell (IEC) physiology, and our recent studies in zebrafish and mice revealed that HNF4A activity in IEC is suppressed by intestinal microbiota. Variants at HNF4A have been associated with human IBD, and IEC-specific knockout of Hnf4a in mice ( Hnf4a ΔIEC ) leads to spontaneous colonic inflammation by 6-12 months. We hypothesized that intestinal pathology in Hnf4a ΔIEC mice may begin earlier in life and that microbiota may contribute to that process. Longitudinal analysis revealed that Hnf4a ΔIEC mice reared in specific pathogen-free (SPF) conditions develop fecal lipocalin 2 (LCN2) flares and episodic loose stools beginning as early as 4-5 weeks of age. Lifetime cumulative LCN2 levels correlated with histopathological features of colitis at 12 months of age. Antibiotic and gnotobiotic tests showed that these phenotypes in Hnf4a ΔIEC mice were dependent on the presence of microbiota. Fecal 16S rRNA gene sequencing in an SPF cohort of Hnf4a ΔIEC mice and controls at 12 months of age disclosed that genotype was a significant contributor to alterations in microbiota composition. Longitudinal analysis in a subset of inflamed Hnf4a ΔIEC and wild-type mice revealed that microbial community differences emerged at early life stages when fecal LCN2 flares first arose. These microbiota differences included a salient increase in the relative abundance of Akkermansia muciniphila in a subset of Hnf4a ΔIEC mice. We isolated an A. muciniphila strain from an aged, inflamed Hnf4a ΔIEC mouse, and its genome sequence revealed it to be a member of a new Akkermansia phylogroup with genetic features distinct from the known phylogroups. We conclude that HNF4A functions in IEC throughout the lifespan to protect against episodic flares of inflammation induced by microbiota while also shaping microbiota assembly. These results establish Hnf4a ΔIEC mice as a useful model for investigating preclinical pathology and host-microbiota interactions that precede overt IBD onset. NIH P01-DK094779 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of herbal tea (Platostoma palustre) on blood glucose regulation in vivo

Platostoma palustre jelly is a traditional food. Platostoma palustre has been used as folk medicine and is effective against heat-shock, hypertension and diabetes. Therefore, the aim of in vivo study was to determine the effects of herbal tea (Platostoma palustre) on blood glucose regulation. The commercial herbal tea (Platostoma palustre) was kindly provided by Yueta Agricultural Biotechnology Inc. Adult male 18 Institute of Cancer Research (ICR) mice [8 weeks old; body weight (BW) between 31-33 g] with specific pathogen-free conditions were used for this study. All ICR mice were divided respectively the normal control group (n = 6), the negative control group (n = 6), and the herbal tea group (n = 6). The ICR mice (the negative control group and the herbal tea group) were intraperitoneally injected with streptozotocin (65 mg/kg BW) and nicotinamide (230 mg/kg BW) for inducing the symptoms of hyperglycemia. In the herbal tea group, the herbal tea (10 mL/kg BW) was administrated to ICR mice by gavage. To monitor the blood glucose levels in ICR mice, blood was obtained from the tail of ICR mice, and blood glucose levels were determined using the external glucometer. Blood glucose measurements were conducted once in ICR mice before the experiment and were detected once per month after the experiment. Additionally, the change of ICR mice’ BW, the blood glucose of ICR mice, and the observation of ICR mice’ behavior were monitored and detected during the experiment. The results of this experiment showed · Weight change: the weight gain of the negative control group and the herbal tea group were significantly lower than those of the normal control group and there was no significant difference between the negative control group and the herbal tea group. · Fasting blood glucose and postprandial blood glucose: the fasting blood glucose of the negative control group was significantly higher than that of the normal control group, while the herbal tea group had a tendency to lower the fasting blood glucose, but there was no significant difference compared with the negative control group. The postprandial blood glucose level results showed that the negative control group was significantly higher than the normal control group. The postprandial blood glucose level of the herbal tea group was between the normal control group and the negative control group at the 4th week administration with the herbal tea. At the 8th week administration with the herbal tea, there was a significant difference compared with the negative control group. · Oral glucose tolerance test (OGTT): 4 to 12 weeks after hyperglycemia was induced, the blood glucose levels of the negative control group at each OGTT test point were significantly higher than those of the normal control group. The blood glucose level at the test point tended to decrease, but there was no significant difference from the negative control group. By calculating the area under the OGTT curve, it was found that the area under the curve of the negative control group was significantly higher than that of the normal control group, while the results of the herbal tea group at the 8th and 12th weeks were significantly lower than those of the negative control group. Taken all results together, the hyperglycemia was successfully induced in the experimental ICR mice. After administrating with the herbal tea, the fasting blood glucose level of the ICR mice tended to improve. In addition, a significant improvement was seen in the results of postprandial blood sugar and oral glucose tolerance test effectiveness. Therefore, based on the results of this experiment, it is speculated that drinking the herbal tea for 3 months has considerable potential for blood glucose regulation, which can be used as the basis for the development of related products of the herbal tea in the future.

Natural Microbial Exposure from the Earliest Natural Time Point Enhances Immune Development by Expanding Immune Cell Progenitors and Mature Immune Cells.

Microbial experience fundamentally shapes immunity, particularly during the perinatal period when the immune system is underdeveloped, and novel microbial encounters are common. Most animal models are raised in specific pathogen-free (SPF) conditions with relatively uniform microbial communities. How SPF housing conditions alter early-life immune development relative to natural microbial exposure (NME) has not been thoroughly investigated. In this article, we compare immune development in SPF-raised mice with mice born from immunologically experienced mothers in microbially diverse environments. NME induced broad immune cell expansion, including naive cells, suggesting mechanisms besides activation-induced proliferation contribute to the increase in immune cell numbers. We found NME conditions also expanded immune cell progenitor cell populations in the bone marrow, suggesting microbial experience enhances immune development at the earliest stages of immune cell differentiation. Multiple immune functions characteristically impaired in infants were also enhanced by NME, including T cell memory and Th1 polarization, B cell class switching and Ab production, proinflammatory cytokine expression, and bacterial clearance after Listeria monocytogenes challenge. Collectively, our studies reveal numerous impairments in immune development in SPF conditions relative to natural immune development.