Pathogen-free Conditions Research Articles

418P - Oxidized low-density lipoprotein receptor 1 promotes lung metastases in osteosarcoma through regulating the epithelial-to-mesenchymal transition

Background: Oxidized low-density lipoprotein receptor 1 (OLR1), a type II membrane protein, has been identified as receptor for oxidized low-density lipoprotein. Previously, we described that high expression of OLR1 was associated with poor prognosis in squamous non-small cell lung cancer (NCSLC) and could be used in a prognosis-predictive model. The current study firstly provided evidence that OLR1 regulated EMT and thus promoted lung metastases in osteosarcoma (OS). Methods: All relevant experiments were conducted according to the manufacturer’s protocols. In vivo tumor xenograft experiments were carried out in 6- to 16-week-old mice, then maintained in our animal facility under pathogen-free conditions in accordance with the Institutional Guidelines and approval by local authorities. For the use of the clinical materials for research purposes, prior patient’s consent and approval from the Institute Research Ethics Committee were obtained. All statistical analyses were performed using IBM SPSS Statistics 22.0 for Windows. Results: Microarrays were adopted to explore the underlying epigenetic mechanisms related to metastasis. 44 genes were identified among a total of 26890 differentially expressed genes. After validation in paired primary and metastatic tissues, OLR1 was selected in the current study. The expression levels of OLR1 were tested in four widely used cell lines. Cell proliferation, migration and invasion could be enhanced when OLR1 is overexpressed. OLR1 overexpression also triggered G1 to S+G2 phases of cell cycle. Accordingly, cell proliferation, migration and invasion would be reduced when OLR1 is silenced. OLR1-silencing blocked G1 to S+G2 phases of cell cycle. Also, OLR1 silencing effectively suppressed local tumor carcinogenesis and lung metastases in vivo. Moreover, silencing OLR1 repressed the expression of mesenchymal markers (Snail, Twist, and N-cadherin), but induced an epithelial marker (E-cadherin). Conclusions: This study indicated a novel molecular mechanism involving the role of OLR1 in lung metastases of osteosarcoma, strengthening the correlation between OLR1 and lung metastases. Legal entity responsible for the study: Shanghai Chest Hospital. Funding: National Natural Science Foundation. Disclosure: All authors have declared no conflicts of interest.

Loss of murine Gfi1 causes neutropenia and induces osteoporosis depending on the pathogen load and systemic inflammation.

Gfi1 is a key molecule in hematopoietic lineage development and mutations in GFI1 cause severe congenital neutropenia (SCN). Neutropenia is associated with low bone mass, but the underlying mechanisms are poorly characterized. Using Gfi1 knock-out mice (Gfi1-ko/ko) as SCN model, we studied the relationship between neutropenia and bone mass upon different pathogen load conditions. Our analysis reveals that Gfi1-ko/ko mice kept under strict specific pathogen free (SPF) conditions demonstrate normal bone mass and survival. However, Gfi1-ko/ko mice with early (nonSPF) or late (SPF+nonSPF) pathogen exposure develop low bone mass. Gfi1-ko/ko mice demonstrate a striking rise of systemic inflammatory markers according to elevated pathogen exposure and reduced bone mass. Elevated inflammatory cytokines include for instance Il-1b, Il-6, and Tnf-alpha that regulate osteoclast development. We conclude that low bone mass, due to low neutrophil counts, is caused by the degree of systemic inflammation promoting osteoclastogenesis.

Distinct Housing Conditions Reveal a Major Impact of Adaptive Immunity on the Course of Obesity-Induced Type 2 Diabetes.

Obesity is associated with adipose tissue inflammation, insulin resistance, and the development of type 2 diabetes (T2D). However, our knowledge is mostly based on conventional murine models and promising preclinical studies rarely translated into successful therapies. There is a growing awareness of the limitations of studies in laboratory mice, housed in abnormally hygienic specific pathogen-free (SPF) conditions, as relevant aspects of the human immune system remain unappreciated. Here, we assessed the impact of housing conditions on adaptive immunity and metabolic disease processes during high-fat diet (HFD). We therefore compared diet-induced obesity in SPF mice with those housed in non-SPF, so-called “antigen exposed” (AE) conditions. Surprisingly, AE mice fed a HFD maintained increased insulin levels to compensate for insulin resistance, which was reflected in islet hyperplasia and improved glucose tolerance compared to SPF mice. By contrast, we observed higher proportions of effector/memory T cell subsets in blood and liver of HFD AE mice accompanied by the development of non-alcoholic steatohepatitis-like liver pathology. Thus, our data demonstrate the impact of housing conditions on metabolic alterations. Studies in AE mice, in which physiological microbial exposure was restored, could provide a tool for revealing therapeutic targets for immune-based interventions for T2D patients.

Q969R polymorphism in NLRP3 is associated with immune responses to vaccination against bacterial infections in pigs.

Nucleotide-binding domain, leucine-rich-containing family, pyrin-domain containing-3 (NLRP3) is an important pattern recognition receptor involved in various inflammatory responses and adjuvant effects upon vaccination. We previously identified the Q969R (A2906G) gain-of-function polymorphism in porcine NLRP3, which increased production of interleukin-1β in invitro gene transfection experiments. Here, we explored the associations between the A2906G polymorphism and antibody responses after vaccination against bacteria in Large White pigs maintained under specific pathogen-free conditions. The NLRP3-2906A/G pigs had a greater antibody response to vaccine antigens than NLRP3-2906A/A pigs. We observed a significant association of the antibody response against Haemophilus parasuis serotype 2 and 5 with NLRP3 genotypes. As the A2906G polymorphism in NLRP3 is widely distributed in commercial pig breeds, Landrace, Large White and Berkshire pigs, there is potential for improvement in vaccine efficiency and disease resistance using this polymorphism in various pig populations.

The Role of Proteasome Inhibitor MG132 in 2,4-Dinitrofluorobenzene-Induced Atopic Dermatitis in NC/Nga Mice

Background: Although immunosuppressants for therapy of atopic dermatitis (AD) are still being sought, proteasome inhibitors are also potential candidates for the treatment of AD. Proteasome inhibitors exert various effects by blocking proteasomal degradation and help regulate processes such as apoptosis induction via caspase-9, cell cycle progression via cyclins, NF-κB inactivation via IκB, and downregulation of antigen cross-presentation. The cells targeted by proteasome inhibitors are therefore activated cells undergoing proliferation or differentiation, and antigen-presenting cells carrying out protein degradation. Objectives: This study investigated the therapeutic effects and side effects of a proteasome inhibitor, MG132, on the treatment of AD. Methods: AD-like disease in NC/Nga mice housed under specific pathogen-free conditions was induced by repeated application of 2,4-dinitrofluorobenzene (DNFB). Disease progression was evaluated by inflammation score, histopathology, and serum IgE level, and the effects of systemic MG132 administration were investigated. The percentages and absolute numbers for each population of Th1, Th2, and Th17 cells in the axillary lymph nodes were analyzed by flow cytometry. Results: DNFB application increased the expression of a unique major histocompatibility complex class I mutant molecule D/L^dm7 in dendritic cells (DCs), and increased Th1 and Th17 cells in NC/Nga mice. In vivo MG132 administration to NC/Nga mice with DNFB-induced dermatitis reduced Th17 cells but maintained the level of Th1 cells, resulting in the alleviation of dermatitis lesions by decreasing both serum IgE hyperproduction and mast cell migration. To understand the mechanisms maintaining Th1 cell levels following in vivo MG132-administration, we focused on the role of proteasomes regulating D/L^dm7 expression. Interestingly, 20S proteasome activity was higher in NC/Nga DCs than in BALB/c DCs. In vitro MG132 administration partially increased D/L^dm7 expression in a dose-dependent manner during DC maturation, and induced IFN-γ production from autoreactive CD8+ T cells but not from CD4+ T cells following coculturing with D/L^dm7-upregulated DCs. Conclusion: Although MG132 administration temporarily alleviated AD pathogenesis in NC/Nga mice, prolonged MG132 treatment may result in immunopathogenesis leading to chronic AD due to its side effect of maintaining Th1 levels via autoreactive CD8+ T cells.

Effects of an immunosuppressive active component of Periplocae Cortex (Periploca sepium Bge.) on positive selection of thymocytes in vitro

Abstract Objective To determine the effect of an immunosuppressive active component (periploside A) isolated from the stem bark of Periplocae Cortex (Periploca sepium Bge.), a Chinese medicinal herb used in the treatment of rheumatoid arthritis for centuries in China, on positive selection of thymocytes in vitro. Methods Female C57BL/6 mice at 6 weeks of age were housed in specific pathogen-free conditions. Double-positive thymocytes from C57BL/6 mice were induced into positive selection in vitro with or without periploside A treatment. Cell viability and expression of CD69, CD4, and CD8 were analyzed by flow cytometry. Results Flow cytometric examination of thymocyte populations revealed that the percentage of CD8+ single-positive thymocytes was decreased by periploside A upon differentiation induced by an anti-CD3 antibody. However, the percentage of CD4+ single-positive thymocytes was decreased by periploside A upon differentiation induced by phorbol 12-myristate 13-acetate/ionomycin. Expression of CD69 plays a major role in prohibiting differentiation of thymocytes. Treatment with periploside A decreased CD69 expression in thymocytes. Conclusion These results demonstrate that periploside A influences positive selection of thymocytes in vitro.

Tristetraprolin Is Required for Alveolar Bone Homeostasis

Tristetraprolin (TTP) is an RNA-binding protein that targets numerous immunomodulatory mRNA transcripts for degradation. Many TTP targets are key players in the pathogenesis of periodontal bone loss, including tumor necrosis factor–α. To better understand the extent that host immune factors play during periodontal bone loss, we assessed alveolar bone levels, inflammation and osteoclast activity in periodontal tissues, and immune response in draining cervical lymph nodes in TTP-deficient and wild-type (WT) mice in an aging study. WT and TTP-deficient (knockout [KO]) mice were used for all studies under specific pathogen-free conditions. Data were collected on mice aged 3, 6, and 9 mo. Microcomputed tomography (µCT) was performed on maxillae where 3-dimensional images were generated and bone loss was assessed. Decalcified sections of specimens were scored for inflammation and stained with tartrate-resistant acid phosphate (TRAP) to visualize osteoclasts. Immunophenotyping was performed on single-cell suspensions isolated from primary and peripheral lymphoid tissues using flow cytometry. Results presented indicate that TTP KO mice had significantly more alveolar bone loss over time compared with WT controls. Bone loss was associated with significant increases in inflammatory cell infiltration and an increased percentage of alveolar bone surfaces apposed with TRAP+ cells. Furthermore, it was found that the draining cervical lymph nodes were significantly enlarged in TTP-deficient animals and contained a distinct pathological immune profile compared with WT controls. Finally, the oral microbiome in the TTP KO mice was significantly different with age from WT cohoused mice. The severe bone loss, inflammation, and increased osteoclast activity observed in these mice support the concept that TTP plays a critical role in the maintenance of alveolar bone homeostasis in the presence of oral commensal flora. This study suggests that TTP is required to inhibit excessive inflammatory host responses that contribute to periodontal bone loss, even in the absence of specific periodontal pathogens.

Environmental factors regulate Paneth cell phenotype and host susceptibility to intestinal inflammation in Irgm1-deficient mice.

ABSTRACTCrohn's disease (CD) represents a chronic inflammatory disorder of the intestinal tract. Several susceptibility genes have been linked to CD, though their precise role in the pathogenesis of this disorder remains unclear. Immunity-related GTPase M (IRGM) is an established risk allele in CD. We have shown previously that conventionally raised (CV) mice lacking the IRGM ortholog, Irgm1 exhibit abnormal Paneth cells (PCs) and increased susceptibility to intestinal injury. In the present study, we sought to utilize this model system to determine if environmental conditions impact these phenotypes, as is thought to be the case in human CD. To accomplish this, wild-type and Irgm1−/− mice were rederived into specific pathogen-free (SPF) and germ-free (GF) conditions. We next assessed how these differential housing environments influenced intestinal injury patterns, and epithelial cell morphology and function in wild-type and Irgm1−/− mice. Remarkably, in contrast to CV mice, SPF Irgm1−/− mice showed only a slight increase in susceptibility to dextran sodium sulfate-induced inflammation. SPF Irgm1−/− mice also displayed minimal abnormalities in PC number and morphology, and in antimicrobial peptide expression. Goblet cell numbers and epithelial proliferation were also unaffected by Irgm1 in SPF conditions. No microbial differences were observed between wild-type and Irgm1−/− mice, but gut bacterial communities differed profoundly between CV and SPF mice. Specifically, Helicobacter sequences were significantly increased in CV mice; however, inoculating SPF Irgm1−/− mice with Helicobacter hepaticus was not sufficient to transmit a pro-inflammatory phenotype. In summary, our findings suggest the impact of Irgm1-deficiency on susceptibility to intestinal inflammation and epithelial function is critically dependent on environmental influences. This work establishes the importance of Irgm1−/− mice as a model to elucidate host-environment interactions that regulate mucosal homeostasis and intestinal inflammatory responses. Defining such interactions will be essential for developing novel preventative and therapeutic strategies for human CD.

Shaping of Intestinal Microbiota in Nlrp6- and Rag2-Deficient Mice Depends on Community Structure

Contradicting observations have been made regarding the relative contributions of immune sensors to shaping the microbiome, yet the reasons for these discrepancies are not fully understood. Here, we investigated the contribution of environmental factors in shaping the microbiome in mice deficient in adaptive immunity (Rag2-/-) and Nlrp6, an immune sensor proposed to be involved in regulation of microbiota composition. In conventionally housed Nlrp6-/- mice, familial transmission has a significant effect on microbiota composition, complicating theanalysis of genotype-dependent effects. Notably, after rederivation into standardized specific pathogen-free (SPF) conditions devoid of pathobionts, microbiota composition was indistinguishable between WT, Rag2-/-, and Nlrp6-/- mice. However, upon reintroduction of a pathobiont-containing community host, genotype-dependent differences reappear, specifically affecting the relative abundance of pathobionts such as Helicobacter spp. Our results show that the impact of Nlrp6 and also of adaptive immunity on microbiota composition depends on community structure and primarily influences pathobionts but not commensals.

Staged development of long-lived T-cell receptor αβ TH17 resident memory T-cell population to Candida albicans after skin infection

Candida albicans is a dimorphic fungus to which human subjects are exposed early in life, and by adulthood, it is part of the mycobiome of skin and other tissues. Neonatal skin lacks resident memory T (TRM) cells, but in adults the Calbicans skin test is a surrogate for immunocompetence. Young adult mice raised under specific pathogen-free conditions are naive to C albicans and have been shown recently to have an immune system resembling that of neonatal human subjects. We studied the evolution of the adaptive cutaneous immune response to Candida species. We examined both human skin T cells and the de novo and memory immune responses in a mouse model of C albicans skin infection. In mice the initial IL-17-producing cells after C albicans infection were dermal γδ T cells, but by day 7, αβ TH17 effector T cells were predominant. By day 30, the majority of C albicans-reactive IL-17-producing T cells were CD4 TRM cells. Intravital microscopy showed that CD4 effector T cells were recruited to the site of primary infection and were highly motile 10days after infection. Between 30 and 90days after infection, these CD4 T cells became increasingly sessile, acquired expression of CD69 and CD103, and localized to the papillary dermis. These established TRM cells produced IL-17 on challenge, whereas motile migratory memory T cells did not. TRM cells rapidly clear an infectious challenge with C albicans more effectively than recirculating T cells, although both populations participate. We found that in normal human skin IL-17-producing CD4+ TRM cells that responded to C albicans in an MHC class II-restricted fashion could be identified readily. These studies demonstrate that C albicans infection of skin preferentially generates CD4+ IL-17-producing TRM cells, which mediate durable protective immunity.

Altered Gut Microbiota in a Mouse Model of Alzheimer's Disease.

The topic of gut microbiota is currently attracting considerable interest as a potential factor in Alzheimer's disease (AD). However, the extent and time course of alterations in the gut microbiota, and their effects on AD pathology remain uncertain. Herein, we compared the fecal microbiomes and fecal short chain fatty acid composition (SCFAs) between wild-type and AD model mice at different ages under strictly controlled specific pathogen free conditions, and also conducted microscopic investigations of intestinal structures. Our results showed that the microbiota composition and diversity were perturbed and the level of SCFAs was reduced in AD mice, predicting alterations in more than 30 metabolic pathways, which may be associated with amyloid deposition and ultrastructural abnormalities in AD mouse intestine. These findings indicate that AD pathology might not only affect brain function directly, but also exacerbate cognitive deficits through reducing the level of SCFAs via alterations of gut microbiota induced by intestinal amyloid deposition. Our data may support a role of gut microbiota, and suggest a novel route for therapeutic intervention in AD.

PUB016 Oxidized Low Density Lipoprotein Receptor 1 Promotes Lung Metastases through Regulating the Epithelial-To-Mesenchymal Transition

Oxidized low density lipoprotein receptor 1 (OLR1), a type II membrane protein, has been identified as receptor for oxidized low-density lipoprotein. Previously, we described that high expression of OLR1 was associated with poor prognosis in squamous non-small cell lung cancer (NCSLC), and could construct a prognosis predictive model. The current study firstly provided evidence that OLR1 regulated EMT and thus promoted lung metastases in osteosarcoma (OS). All relevant experiments were conducted according to the manufacturer’s protocols. In vivo tumor xenograft experiments were carried out in 6- to 16-week-old mice, then maintained in our animal facility under pathogen-free conditions in accordance with the Institutional Guidelines and approval by local authorities. For the use of the clinical materials for research purposes, prior patient’s consent and approval from the Institute Research Ethics Committee were obtained. All statistical analyses were performed using IBM SPSS Statistics 22.0 for Windows (SPSS Inc, Chicago, IL). Microarrays were adopted to explore the underlying epigenetic mechanisms related to metastasis. 44 genes were identified among total 26890 differentially expressed genes. After validated in paired primary and metastatic tissues, OLR1 was selected in the current study. The expression levels of OLR1 were tested in 4 widely used cell lines. Cell proliferation, migration and invasion could be enhanced when OLR1 was overexpressed. OLR1 overexpression also triggered G1 to S+G2 phases of cell cycle. Accordingly, cell proliferations, migration and invasion would be reduced when OLR1 was silenced. OLR1-silencing blocked G1 to S+G2 phases of cell cycle. Also, OLR1 silencing effectively suppressed local tumor carcinogenesis and lung metastases in vivo. Moreover, silencing OLR1 repressed the expression of mesenchymal markers (Snail, Twist, and N-cadherin), but induced an epithelial marker (E-cadherin). This study indicated a novel molecular mechanism involving the role of OLR1 in lung metastases of osteosarcoma, strengthened the correlation between OLR1 and lung metastases.

Open housing drives the expression of immune response genes in the nasal mucosa, but not the olfactory bulb.

Nasal mucosa and olfactory bulb are separated by the cribriform plate which is perforated by olfactory nerves. We have previously demonstrated that the cribriform plate is permissive for T cells and monocytes and that viruses can enter the bulb upon intranasal injection by axonal transportation. Therefore, we hypothesized that nasal mucosa and olfactory bulb are equipped to deal with constant infectious threats. To detect genes involved in this process, we compared gene expression in nasal mucosa and bulb of mice kept under specific pathogen free (SPF) conditions to gene expression of mice kept on non-SPF conditions using RNA deep sequencing. We found massive alterations in the expression of immune-related genes of the nasal mucosa, while the bulb did not respond immunologically. The absence of induction of immune-related genes in the olfactory bulb suggests effective defence mechanisms hindering entrance of environmental pathogens beyond the outer arachnoid layer. The genes detected in this study may include candidates conferring susceptibility to meningitis.

Age Modifies the Effect of 2-MeV Fast Neutrons on Rat Mammary Carcinogenesis.

The relative biological effectiveness (RBE) of neutrons depends on their physical nature (e.g., energy) and the biological context (e.g., end points, materials). From the perspective of radiological protection, age is an important biological context that influences radiation-related cancer risk, but very few studies have addressed its potential impact on neutron effects. We therefore investigated the influence of age on the effect of accelerator-generated fast neutrons (mean energy, ∼2 MeV) in an animal model of breast carcinogenesis. Female Sprague-Dawley rats at 1, 3 and 7 weeks of age were irradiated with fast neutrons at absorbed doses of 0.0485-0.97 Gy. All animals were kept under specific pathogen-free conditions and screened weekly for mammary tumors by palpation until they were 90 weeks old. Tumors were diagnosed based on histology. Mathematical modeling was used to analyze mammary cancer incidence, collectively using data from this study and a previously reported experiment on 137Cs gamma rays. The results indicate that neutron irradiation elevated the risk of palpable mammary carcinoma with a linear dose response, the slope of which depended on age at time of irradiation. The RBE of neutron radiation was 7.5 ± 3.4, 9.3 ± 3.5 and 26.1 ± 8.9 (mean ± SE) for animals exposed at 1, 3 and 7 weeks of age, respectively. Our results indicate that age of the animal is an important factor influencing the effect of fast neutrons on breast cancer risk.

Comprehensive validation of T- and B-cell deficiency in rag1-null zebrafish: Implication for the robust innate defense mechanisms of teleosts

rag1−/− zebrafish have been employed in immunological research as a useful immunodeficient vertebrate model, but with only fragmentary evidence for the lack of functional adaptive immunity. rag1-null zebrafish exhibit differences from their human and murine counterparts in that they can be maintained without any specific pathogen-free conditions. To define the immunodeficient status of rag1−/− zebrafish, we obtained further functional evidence on T- and B-cell deficiency in the fish at the protein, cellular, and organism levels. Our developed microscale assays provided evidence that rag1−/− fish do not possess serum IgM protein, that they do not achieve specific protection even after vaccination, and that they cannot induce antigen-specific CTL activity. The mortality rate in non-vaccinated fish suggests that rag1−/− fish possess innate protection equivalent to that of rag1+/− fish. Furthermore, poly(I:C)-induced immune responses revealed that the organ that controls anti-viral immunity is shifted from the spleen to the hepatopancreas due to the absence of T- and B-cell function, implying that immune homeostasis may change to an underside mode in rag-null fish. These findings suggest that the teleost relies heavily on innate immunity. Thus, this model could better highlight innate immunity in animals that lack adaptive immunity than mouse models.

CRISPR/Cas9-Mediated Knockin Application in Cell Therapy: A Non-viral Procedure for Bystander Treatment of Glioma in Mice.

The use of non-viral procedures, together with CRISPR/Cas9 genome-editing technology, allows the insertion of single-copy therapeutic genes at pre-determined genomic sites, overcoming safety limitations resulting from random gene insertions of viral vectors with potential for genome damage. In this study, we demonstrate that combination of non-viral gene delivery and CRISPR/Cas9-mediated knockin via homology-directed repair can replace the use of viral vectors for the generation of genetically modified therapeutic cells. We custom-modified human adipose mesenchymal stem cells (hAMSCs), using electroporation as a transfection method and CRISPR/Cas9-mediated knockin for the introduction and stable expression of a 3 kb DNA fragment including the eGFP (selectable marker) and a variant of the herpes simplex virus 1 thymidine kinase genes (therapeutic gene), under the control of the human elongation factor 1 alpha promoter in exon 5 of the endogenous thymidine kinase 2 gene. Using a U87 glioma model in SCID mice, we show that the therapeutic capacity of the new CRISPR/Cas9-engineered hAMSCs is equivalent to that of therapeutic hAMSCs generated by introduction of the same therapeutic gene by transduction with a lentiviral vector previously published by our group. This strategy should be of general use to other applications requiring genetic modification of therapeutic cells.

On the core bacterial flora of Ixodes persulcatus (Taiga tick)

Ixodes persulcatus is a predominant hard tick species that transmits a wide range of human and animal pathogens. Since bacterial flora of the tick dwelling in the wild always vary according to their hosts and the environment, it is highly desirable that species-associated microbiomes are fully determined by using next-generation sequencing and based on comparative metagenomics. Here, we examine such metagenomic changes of I. persulcatus starting with samples collected from the wild ticks and followed by the reared animals under pathogen-free laboratory conditions over multiple generations. Based on high-coverage genomic sequences from three experimental groups–wild, reared for a single generation or R1, and reared for eight generations or R8 –we identify the core bacterial flora of I. persulcatus, which contains 70 species that belong to 69 genera of 8 phyla; such a core is from the R8 group, which is reduced from 4625 species belonging to 1153 genera of 29 phyla in the wild group. Our study provides a novel example of tick core bacterial flora acquired based on wild-to-reared comparison, which paves a way for future research on tick metagenomics and tick-borne disease pandemics.

Evaluation of the impact of gut microbiota on uremic solute accumulation by a CE-TOFMS–based metabolomics approach

Gut microbiota is involved in the metabolism of uremic solutes. However, the precise influence of microbiota to the retention of uremic solutes in CKD is obscure. To clarify this, we compared adenine-induced renal failure and control mice under germ-free or specific pathogen-free (SPF) conditions, examining the metabolite profiles of plasma, feces, and urine using a capillary electrophoresis time-of-flight mass spectrometry-based approach. Mice with renal failure under germ-free conditions demonstrated significant changes in plasma metabolites. Among 183 detected solutes, plasma levels of 11 solutes, including major uremic toxins, were significantly lower in germ-free mice than in SPF mice with renal failure. These 11 solutes were considered microbiota-derived uremic solutes and included indoxyl sulfate, p-cresyl sulfate, phenyl sulfate, cholate, hippurate, dimethylglycine, γ-guanidinobutyrate, glutarate, 2-hydroxypentanoate, trimethylamine N-oxide, and phenaceturate. Metabolome profiling showed that these solutes were classified into three groups depending on their origins: completely derived from microbiota (indoxyl sulfate, p-cresyl sulfate), derived from both host and microbiota (dimethylglycine), and derived from both microbiota and dietary components (trimethylamine N-oxide). Additionally, germ-free renal failure conditions resulted in the disappearance of colonic short-chain fatty acids, decreased utilization of intestinal amino acids, and more severe renal damage compared with SPF mice with renal failure. Microbiota-derived short-chain fatty acids and efficient amino acid utilization may have a renoprotective effect, and loss of these factors may exacerbate renal damage in germ-free mice with renal failure. Thus, microbiota contributes substantially to the production of harmful uremic solutes, but conversely, growth without microbiota has harmful effects on CKD progression.

Osteoarthritis induced by destabilization of the medial meniscus (DMM) is reduced in germ-free mice

Purpose: Recent studies have suggested a role for the (gut) microbiota in a number of inflammatory conditions, including rheumatoid arthritis, but little is known in osteoarthritis. For this project, we used the DMM model of OA and investigated the difference in OA development between mice maintained in a germ-free environment (GF) and mice housed in standard specific pathogen free (SPF) conditions. We hypothesized that if the gut microbiota produces factors that promote systemic inflammation, then GF mice would develop less severe OA than SPF mice. Methods: DMM surgery was performed on the right leg in C57BL/6 male mice using 23 SPF mice and 20 GF mice housed in a gnotobiotic facility. A sham group was not included since GF mice are in limited supply and we wanted to maximize the numbers of mice in the DMM groups. We have previously shown that OA does not develop after sham surgery in wild-type mice and so the contralateral knee (left) was used as an unoperated control. We analyzed 2 age groups -13.5 weeks AVG age at DMM (17 SPF and 15 GF) and 43 weeks AVG age at DMM (6 SPF and 5 GF). Mice were sacrificed 8 weeks following surgery and both knee joints were processed for histology. Serial sections were cut throughout the joint and the mid- coronal region was identified by the shape of the menisci. Two slides (mid- coronal and another slide ∼ 50 um posteriorly) were stained with Safranin O (Saf O) and scored for cartilage lesions using a modified articular cartilage structure (ACS) score in all four quadrants of the knee. The MAX score was the highest OA severity score of the four quadrant scores and the SUM score was the SUM of the four quadrant scores for the 2 slides. The mid-coronal region slide was also scored for proteoglycan loss (Saf O staining score- using a modified scoring system that follows the ACS score), osteophyte size (medial femur, medial tibia and MAX medial side) and synovial hyperplasia (MAX joint). The data were analyzed using one- way ANOVA and Tukey's post- hoc test; a multiplicity adjusted p value <0.05 was considered significant. Results: Several of the OA severity measurements showed a level of protection in the DMM knees of the GF mice compared to SPF mice. The MAX_ ACS score was decreased in the GF mice by 28% (AVG SPF = 8.652; AVG GF = 6.250; p = 0.036), the MAX_ Saf O score showed no difference while the SUM_Saf O score was decreased by 31% in GF mice (20.87 SPF; 14.35 GF; p = 0.0089). When analyzed in all the animals, the MAX osteophyte size score showed no significant change. When the scores were separated by age, the level of significance increased in the younger mice: the GF showed a reduction in the MAX_ACS score by 45% (9.294 SPF; 5.133 GF; p = 0.0003 - Fig.1), the SUM_ Saf O score by 44% (22.59 SPF; 12.67 GF; p = 0.0004), the MAX_Saf O score by 30% (10.18 SPF; 7.133 GF; p = 0.0380 ) and the MAX osteophyte size score by 36% (2.412 SPF; 1.533 GF; p = 0.0119 ), while the older GF mice showed no difference when compared to the age- matched SPF mice. While the synovial hyperplasia score was higher in the DMM knee compare to the control knee, no difference was seen between the SPF and GF mice, even if analyzed separately based on age. There were no differences in any of the measures in the unoperated control joints. Conclusions: These results suggest a role for the microbiome in OA development in an injury-induced OA model in mice. The finding that the older group of GF mice, compared to age-matched SPF mice, showed less protection from OA than the younger group might be explained by additional pathologies in the GF mice that appear with age (such as bone loss) that could override the effect of the microbiome on the rest of the joint. These results support further investigation into the role of the microbiome in OA, including studies in humans and other mouse models that are ongoing.

Enhancing Survival of Human Hepatocytes by Neonatal Thymectomy and Partial Hepatectomy in Micro-miniature Pigs

BackgroundWith the goal of in vivo cultivation of human hepatocytes that have not been sufficient in full differentiation in vitro, the advantage of neonatal thymectomy was verified on expansion of xenogeneic human hepatocyte in the micro-miniature pig (MMP). MethodsThe thymus was excised immediately after the birth of the MMPs via cesarean section. Newborns were fed by artificial feeding under specific pathogen-free conditions. The thymectomized and nonthymectomized littermates were transplanted with human hepatocytes via a portal vein with or without partial hepatectomy at the MMP adult stage. ResultsThe growth of thymectomized MMPs and the sham operated littermates was not significantly different; the former weighed 1.98 ± 0.30 kg (average ± standard deviation, n = 4) and the latter weighed 2.28 ± 0.39 kg (n = 4) at 1 month of age, and 17.48 ± 1.92 kg and 16.75 ± 2.68 kg at 12 months of age. Blood thymosin α1 concentrations in the thymectomy group were significantly lower than in the control group (0.22 ± 0.05 ng/mL vs 0.46 ± 0.16 ng/mL; n = 4, 12 months old, P = .029). After human hepatocyte transplantation, human albumin levels were detectable on day 28 in the peripheral blood of the thymectomy plus hepatectomy group (14.3 ± 4.9 ng/mL [± range, n = 2]) but were not detectable even on day 21 in the control group. ConclusionsNeonatal thymectomy was successfully achieved in infantile MMPs born via cesarean section. These pigs were considered to be an ideal in vivo bioreactor for human hepatocytes.