Transgenic Rat Model Research Articles

Long-term role of neonatal microglia and monocytes in ovarian health.

Early life microglia are essential for brain development, and developmental disruption in microglial activity may have long-term implications for the neuroendocrine control of reproduction. We and others have previously shown that early life immune activation compromises the long-term potential for reproductive function in females. However, the supportive role of microglia in female reproductive development is still unknown. Here, we examined the long-term programming effects of transient neonatal microglial and monocyte ablation on hypothalamic-pituitary-gonadal (HPG) axis function in female rats. We employed a Cx3cr1-Dtr transgenic Wistar rat model to acutely ablate microglia and monocytes, commencing on either postnatal day (P) 7 or 14, since the development of the HPG axis in female rodents primarily occurs during the first two to three postnatal weeks. After an acutely diminished expression of microglia and monocyte genes in the brain and ovaries, respectively, microglia had repopulated the brain by P21, albeit that cellular complexity was still reduced in both groups at this time. Removal of microglia and monocytes on P7, but not P14 reduced circulating luteinising hormone levels in adulthood and ovarian gonadotropin receptors mRNA. These changes were notably associated with fewer primary and antral follicles in these rats. These data suggest that transient ablation of microglia and monocytes at the start of the second but not the third postnatal week has long-term effects on ovarian health. The findings highlight the important developmental role of a healthy immune system for female potential reproductive capacity and the importance of critical developmental periods to adult ovarian health.

5-HT5A Receptor Antagonist ASP5736 Ameliorates Several Abnormal Behaviors in an Fmr1-Targeted Transgenic Male Rat Model of Fragile X Syndrome

BackgroundFragile X syndrome (FXS) is a genetic condition that causes a range of developmental problems, including intellectual disability, aggressive behavior, anxiety, abnormal sensory processing, and cognitive impairment. Despite intensive preclinical research in Fmr1-targeted transgenic mice, an effective treatment for FXS has yet to be developed. We previously demonstrated that ASP5736, a 5-Hydroxytryptamine (serotonin) receptor 5A receptor antagonist, ameliorated scopolamine-induced working memory deficits in mice, reference memory impairment in aged rats, and methamphetamine-induced positive symptoms and phencyclidine-induced cognitive impairment in animal models of schizophrenia. We hypothesized that ASP5736 may be effective for ameliorating similar behavior deficits in male Fmr1-targeted transgenic rats as a preclinical model of FXS.MethodsWe evaluated the effect of acute oral administration of ASP5736 on the abnormal behavior of hyperactivity (0.01, 0.1 mg/kg), prepulse inhibition (0.01, 0.03, 0.1 mg/kg), and the novel object recognition task (0.1 mg/kg) in Frmr1-knockout (KO) rats.Results Fmr1-KO rats showed body weight gain, hyperactivity, abnormal sensory motor gating, and cognitive impairment. ASP5736 (0.1 mg/kg) reversed the hyperactivity and ameliorated the sensory motor gating deficits (0.03–0.1 mg/kg). ASP5736 (0.01 mg/kg) also improved cognitive impairment.ConclusionsASP5736 is a potential drug candidate for FXS. Further studies are needed to confirm its clinical efficacy.

Early loss of locus coeruleus innervation promotes cognitive and neuropathological changes before amyloid plaque deposition in a transgenic rat model of Alzheimer's disease.

The locus coeruleus (LC) is the main source of noradrenaline (NA) in the mammalian brain and has been found to degenerate during the initial stages of Alzheimer's disease (AD). Recent studies indicate that at late stages of the amyloid pathology, LC-pathological alterations accelerate AD-like pathology progression by interfering with the neuromodulatory and anti-inflammatory properties of NA. However, the impact of LC degeneration at the earliest stages of amyloidosis on the AD-like pathology is not well understood. The LC was lesioned in wild-type and McGill-R-Thy1-APP transgenic (APP tg) rats by administering N-(2-chloroethyl)-N-ethyl-bromo-benzylamine before amyloid plaque deposition. Cognitive deficits and AD-like neuropathological changes were measured after the LC lesion. Four months post-treatment, rats displayed a decrease in brain noradrenergic innervation. The LC lesion in APP tg-treated rats enhanced cognitive deficits and decreased hippocampal cholinergic innervation and neurotrophin expression. In addition, the APP tg-treated rats displayed an increased microglial and astroglial cell number in close vicinity to hippocampal amyloid-beta burdened neurons. The recruited microglia showed cellular alterations indicative of an intermediate activation state. Our results indicate that early LC demise aggravates the early neuroinflammatory process, cognitive impairments, cholinergic deficits and neurotrophin deregulation at the earliest stages of the human-like brain amyloidosis.

11C]Martinostat PET analysis reveals reduced HDAC I availability in Alzheimer’s disease

Alzheimer’s disease (AD) is characterized by the brain accumulation of amyloid-β and tau proteins. A growing body of literature suggests that epigenetic dysregulations play a role in the interplay of hallmark proteinopathies with neurodegeneration and cognitive impairment. Here, we aim to characterize an epigenetic dysregulation associated with the brain deposition of amyloid-β and tau proteins. Using positron emission tomography (PET) tracers selective for amyloid-β, tau, and class I histone deacetylase (HDAC I isoforms 1–3), we find that HDAC I levels are reduced in patients with AD. HDAC I PET reduction is associated with elevated amyloid-β PET and tau PET concentrations. Notably, HDAC I reduction mediates the deleterious effects of amyloid-β and tau on brain atrophy and cognitive impairment. HDAC I PET reduction is associated with 2-year longitudinal neurodegeneration and cognitive decline. We also find HDAC I reduction in the postmortem brain tissue of patients with AD and in a transgenic rat model expressing human amyloid-β plus tau pathology in the same brain regions identified in vivo using PET. These observations highlight HDAC I reduction as an element associated with AD pathophysiology.

Differential Cellular Balance of Olfactory and Vomeronasal Epithelia in a Transgenic BACHD Rat Model of Huntington's Disease.

Background. For neurodegenerative diseases such as Huntington’s disease (HD), early diagnosis is essential to treat patients and delay symptoms. Impaired olfaction, as observed as an early symptom in Parkinson´s disease, may also constitute a key symptom in HD. However, there are few reports on olfactory deficits in HD. Therefore, we aimed to investigate, in a transgenic rat model of HD: (1) whether general olfactory impairment exists and (2) whether there are disease-specific dynamics of olfactory dysfunction when the vomeronasal (VNE) and main olfactory epithelium (MOE) are compared. Methods. We used male rats of transgenic line 22 (TG22) of the bacterial artificial chromosome Huntington disease model (BACHD), aged 3 days or 6 months. Cell proliferation, apoptosis and macrophage activity were examined with immunohistochemistry in the VNE and MOE. Results. No differences were observed in cellular parameters in the VNE between the groups. However, the MOE of the 6-month-old HD animals showed a significantly increased number of mature olfactory receptor neurons. Other cellular parameters were not affected. Conclusions. The results obtained in the TG22 line suggest a relative stability in the VNE, whereas the MOE seems at least temporarily affected.

Inhibition of Hippocampal Neurogenesis Starting in Adolescence Increases Anxiodepressive Behaviors Amid Stress.

Stressors during the adolescent period can affect development of the brain and have long-lasting impacts on behavior. Specifically, adolescent stress impairs hippocampal neurogenesis and can increase risk for anxiety, depression, and a dysregulated stress response in adulthood. In order to model the functional effects of reduced hippocampal neurogenesis during adolescence, a transgenic neurogenesis ablation rat model was used to suppress neurogenesis during the adolescent period and test anxiodepressive behaviors and stress physiology during adulthood. Wildtype and transgenic (TK) rats were given valganciclovir during the first two weeks of adolescence (4-6 weeks old) to knock down neurogenesis in TK rats. Starting in young adulthood (13 weeks old), blood was sampled for corticosterone at several time points following acute restraint stress to measure negative feedback of the stress response, and rats were tested on a battery of anxiodepressive tests at baseline and following acute restraint stress. Although TK rats had large reductions in both cell proliferation during adolescence, as measured by bromodeoxyuridine (BrdU), and ongoing neurogenesis in adulthood (by doublecortin), resulting in decreased volume of the dentate gyrus, negative feedback of the stress response following acute restraint was similar across all rats. Despite similar stress responses, TK rats showed higher anxiety-like behavior at baseline. In addition, only TK rats had increased depressive-like behavior when tested after acute stress. Together, these results suggest that long-term neurogenesis ablation starting in adolescence produces hippocampal atrophy and increases behavioral caution and despair amid stressful environments.

Pharmacokinetics and Pharmacodynamic Effect of a Blood-Brain Barrier-Crossing Fusion Protein Therapeutic for Alzheimer’s Disease in Rat and Dog

PurposeWe have recently demonstrated the brain-delivery of an Amyloid-ß oligomer (Aßo)-binding peptide-therapeutic fused to the BBB-crossing single domain antibody FC5. The bi-functional fusion protein, FC5-mFc-ABP (KG207-M) lowered both CSF and brain Aß levels after systemic dosing in transgenic mouse and rat models of Alzheimer’s disease (AD). For development as a human therapeutic, we have humanized and further engineered the fusion protein named KG207-H. The purpose of the present study was to carry out comparative PK/PD studies of KG207-H in wild type rat and beagle dogs (middle-aged and older) to determine comparability of systemic PK and CSF exposure between rodent species and larger animals with more complex brain structure such as dogs.MethodBeagle dogs were used in this study as they accumulate cerebral Aß with age, as seen in human AD patients, and can serve as a model of sporadic AD. KG207-H (5 to 50 mg/kg) was administered intravenously and serum and CSF samples were serially collected for PK studies and to assess target engagement. KG207-H and Aβ levels were quantified using multiplexed selected reaction monitoring mass spectrometry.ResultsAfter systemic dosing, KG207-H demonstrated similar serum pharmacokinetics in rats and dogs. KG207-H appeared in the CSF in a time- and dose-dependent manner with similar kinetics, indicating CNS exposure. Further analyses revealed a dose-dependent inverse relationship between CSF KG207-H and Aß levels in both species indicating target engagement.ConclusionThis study demonstrates translational attributes of BBB-crossing Aβ-targeting biotherapeutic KG207-H in eliciting a pharmacodynamic response, from rodents to larger animal species.

Hidden brain atrophy in ultra-high field MR images in a transgenic rat model of Huntington's disease

The predominant neuropathological sign of Huntington's disease (HD) is a profound and progressive neuronal cell loss in the striatum and the neo-cortex. These histopathological changes have been widely investigated in post-mortem brains obtained from animal models of HD. However, imaging studies in rodents have so far led to conflicting results, where the outcomes have not been in line with histopathological findings. Herein, we aimed to further characterize the progression of neurodegeneration in a transgenic rat model of HD at different ages.Volumetric changes were measured in vivo via ultra-high field MR imaging (7T) and subsequent stereological analysis in the striatum, lateral ventricles, and cerebral cortex of tgHD rats were investigated at 9, 12, and 18-months of age.Histological assessment showed significant atrophy in the striatum, enlarged ventricular volumes, and a thinning of the cerebral cortex in tgHD rats at the late phase of the disease when compared to the wild-type (WT) littermates. Whereas only a reduction in striatal cell volume was observed at the early stage of the disease. MR imaging on the other hand, did not show detectable volumetric change in the investigated structures between tgHD and WT rats at different time-points.Our findings demonstrate neuronal shrinkage precedes striatal atrophy in tgHD rats. As in human HD, the manifestation of striatal atrophy appears prior to cortical thinning in tgHD rats. Surprisingly, contemporary in vivo ultra-high field MR imaging failed to detect these volumetric changes. These findings suggest that contemporary MRI protocols are unsuitable for detecting HD related alterations in rodent brain.

Loss of the heterogeneous expression of flippase ATP11B leads to cerebral small vessel disease in a normotensive rat model

Cerebral small vessel disease (SVD) is the leading cause of vascular dementia, causes a quarter of strokes, and worsens stroke outcomes. The disease is characterised by patchy cerebral small vessel and white matter pathology, but the underlying mechanisms are poorly understood. This microvascular and tissue damage has been classically considered secondary to extrinsic factors, such as hypertension, but this fails to explain the patchy nature of the disease, the link to endothelial cell (EC) dysfunction even when hypertension is absent, and the increasing evidence of high heritability to SVD-related brain damage. We have previously shown the link between deletion of the phospholipase flippase Atp11b and EC dysfunction in an inbred hypertensive rat model with SVD-like pathology and a single nucleotide polymorphism (SNP) in ATP11B associated with human sporadic SVD. Here, we generated a novel normotensive transgenic rat model, where Atp11b is deleted, and show pathological, imaging and behavioural changes typical of those in human SVD, but that occur without hypertension. Atp11bKO rat brain and retinal small vessels show ECs with molecular and morphological changes of dysfunction, with myelin disruption in a patchy pattern around some but not all brain small vessels, similar to the human brain. We show that ATP11B/ATP11B is heterogeneously expressed in ECs in normal rat and human brain even in the same transverse section of the same blood vessel, suggesting variable effects of the loss of ATP11B on each vessel and an explanation for the patchy nature of the disease. This work highlights a link between inherent EC dysfunction and vulnerability to SVD white matter damage with a marked heterogeneity of ECs in vivo which modulates this response, occurring even in the absence of hypertension. These findings refocus our strategies for therapeutics away from antihypertensive (and vascular risk factor) control alone and towards ECs in the effort to provide alternative targets to prevent a major cause of stroke and dementia.

Metabolic alterations in the visual pathway of retinitis pigmentosa rats: A longitudinal multimodal magnetic resonance imaging study with histopathological validation.

Because retinitis pigmentosa (RP) has been shown to cause degenerative changes in the entire visual pathway, there is an urgent need to perform longitudinal assessments of RP-induced degeneration and identify imaging protocols to detect this degeneration as early as possible. In this study, we assessed a transgenic rat model of RP by using complementary noninvasive magnetic resonance imaging techniques, namely, proton magnetic resonance spectroscopy (1 H-MRS), to investigate the metabolic changes in RP. Our study demonstrated decreased concentrations and ratios to creatine (Cr) of N-acetylaspartate (NAA), glutamate (Glu), γ-aminobutyric acid (GABA), and taurine (Tau), whereas myo-inositol (Ins) and choline (Cho) were increased in the visual cortex of Royal College of Surgeons (RCS) rats compared with control rats (p < 0.05). Furthermore, with the progression of RP, the concentrations of NAA, Glu, GABA, and Tau, and the ratios of GABA/Cr and Tau/Cr significantly decreased over time, whereas the concentrations of Ins and Cho and the ratio of Ins/Cr significantly increased over time (p < 0.05). In addition, in RCS rats, NAA/Cr decreased significantly from 3 to 4 months postnatal (p < 0.001), and Cho/Cr increased significantly from 4 to 5 months postnatal (p = 0.005). Meanwhile, the 1 H-MRS indicators in 5-month postnatal RCS rats could be confirmed by immunohistochemical staining. In conclusion, with the progression of RP, the metabolic alterations in the visual cortex indicated progressive reprogramming with the decrease of neurons and axons, accompanied by the proliferation of gliocytes.

Investigating White Matter Inflammatory Cells and their Relationship with Beta‐Amyloid in Alzheimer's Disease

Alzheimer’s disease (AD) is a chronic neurodegenerative condition affecting millions of people worldwide. With an aging population, it is predicted that by 2050 the number of individuals living with AD will triple, resulting in an increased social and economic burden. Previous research has demonstrated that the pathological process leading to AD occurs years before a positive diagnosis. Therefore, identifying biomarkers that co‐occur within the early stage of AD progression and that predict worsening cognitive outcomes are critically needed. AD is characterized by the presence of beta‐amyloid plaques, neurofibrillary tangles and neuroinflammation. Clinically, being unable to recall new information is the most common outcome of AD. White matter inflammation is mediated by microglial activation and astrocytosis and are thought to be important underlying mechanisms involved in the pathogenesis of AD progression, while also being predictive of future cognitive decline. In a transgenic rat model of AD, it has been previously found that microglial activation within the white matter tracts was strongly associated with impairments in executive function. Age‐related differences in inflammatory cells have also been identified. One study found a significant increase in age‐associated white matter inflammatory cells in amyloid‐plaque negative rats at 7‐and‐8‐months of age. Sex‐and‐age related differences in inflammatory cells and amyloid‐beta have been identified, however, they remain poorly understood in the white matter. The purpose of this study was to investigate the sex‐specific‐age trajectory of white matter inflammatory cells in a wildtype rat model of normal aging and in two transgenic rat models of AD: one in an amyloid‐plaque negative, and one in an amyloid‐plaque positive environment. We hypothesized that microglial activation increases with normal aging and is further exacerbated by the presence of beta‐amyloid deposition. Male (n=5) and female (n=5) Fischer 344 wildtype, transgenic APP21 (amyloid‐plaque negative) and APP/PS1 (amyloid‐plaque positive) rats at 3, 9 and 15‐months of age were included in the experimental design. Immunohistochemical analyses were conducted to detect the presence of microglial activation, pro‐inflammatory M1 microglial activation, astrocytosis and beta‐amyloid. Results demonstrate unique age‐dependant trajectories in microglial activation, particularly in the corpus callosum, supraventricular corpus callosum and internal capsule of the wildtype, transgenic APP/21 and APP/PS1 rat genotypes. Given that only the APP/PS1 rats demonstrated age‐dependant plaque deposition, our results indicate that microglial activation within the white matter is associated with changes in amyloid‐plaque deposition. Future work will aim to better understand the mechanisms related to the relationship between white matter microglial activation, amyloid‐plaque deposition and cognitive impairment. A better understanding of this relationship can aid in the development of an earlier method of detecting AD, which in turn can better define a new therapeutic window of opportunity to target microglial activation and prevent neurodegeneration and cognitive decline associated with AD.

Disrupted-in-schizophrenia 1 Protein Misassembly Impairs Cognitive Flexibility and Social Behaviors in a Transgenic Rat Model

Alterations in cognitive functions, social behaviors and stress reactions are commonly diagnosed in chronic mental illnesses (CMI). Animal models expressing mutant genes associated to CMI represent either rare mutations or those contributing only minimally to genetic risk. Non-genetic causes of CMI can be modeled by disturbing downstream signaling pathways, for example by inducing protein misassembly or aggregation. The Disrupted-in-Schizophrenia 1 (DISC1) gene was identified to be disrupted and thereby haploinsufficient in a large pedigree where it was associated with CMI. In a subset of CMI patients, the DISC1 protein misassembles to an insoluble protein. This has been modeled in a rat (tgDISC1 rat) where the full-length, non mutant human transgene was overexpressed and cognitive impairments were observed. Here, we investigated the scope of effects of DISC1 protein misassembly by investigating spatial memory, social behavior and stress resilience. In water maze tasks, the tgDISC1 rats showed intact spatial learning and memory, but were deficient in flexible adaptation to spatial reversal learning compared to littermate controls. They also displayed less social interaction. Additionally, there was a trend towards increased corticosterone levels after restraint stress in the tgDISC1 rats. Our findings suggest that DISC1 protein misassembly leads to disturbances of cognitive flexibility and social behaviors, and might also be involved in stress sensitization. Since the observed behavioral features resemble symptoms of CMI, the tgDISC1 rat may be a valuable model for the investigation of cognitive, social and – possibly – also stress-related symptoms of major mental illnesses.

Repurposing ibudilast to mitigate Alzheimer's disease by targeting inflammation.

Alzheimer's disease is a multifactorial disease that exhibits cognitive deficits, neuronal loss, amyloid plaques, neurofibrillary tangles and neuroinflammation in the brain. Hence, a multi-target drug would improve treatment efficacy. We applied a new multi-scale predictive modelling framework that integrates machine learning with biophysics and systems pharmacology to screen drugs for Alzheimer's disease using patients' tissue samples. Our predictive modelling framework identified ibudilast as a drug with repurposing potential to treat Alzheimer's disease. Ibudilast is a multi-target drug, as it is a phosphodiesterase inhibitor and toll-like receptor 4 (TLR4) antagonist. In addition, we predict that ibudilast inhibits off-target kinases (e.g. IRAK1 and GSG2). In Japan and other Asian countries, ibudilast is approved for treating asthma and stroke due to its anti-inflammatory potential. Based on these previous studies and on our predictions, we tested for the first time the efficacy of ibudilast in Fisher transgenic 344-AD rats. This transgenic rat model is unique as it exhibits hippocampal-dependent spatial learning and memory deficits and Alzheimer's disease pathology, including hippocampal amyloid plaques, tau paired-helical filaments, neuronal loss and microgliosis, in a progressive age-dependent manner that mimics the pathology observed in Alzheimer's disease patients. Following long-term treatment with ibudilast, transgenic rats were evaluated at 11 months of age for spatial memory performance and Alzheimer's disease pathology. We demonstrate that ibudilast-treatment of transgenic rats mitigated hippocampal-dependent spatial memory deficits, as well as hippocampal (hilar subregion) amyloid plaque and tau paired-helical filament load, and microgliosis compared to untreated transgenic rat. Neuronal density analysed across all hippocampal regions was similar in ibudilast-treated transgenic compared to untreated transgenic rats. Interestingly, RNA sequencing analysis of hippocampal tissue showed that ibudilast-treatment affects gene expression levels of the TLR and ubiquitin-proteasome pathways differentially in male and female transgenic rats. Based on the TLR4 signalling pathway, our RNA sequencing data suggest that ibudilast-treatment inhibits IRAK1 activity by increasing expression of its negative regulator IRAK3, and/or by altering TRAF6 and other TLR-related ubiquitin ligase and conjugase levels. Our results support that ibudilast can serve as a repurposed drug that targets multiple pathways including TLR signalling and the ubiquitin/proteasome pathway to reduce cognitive deficits and pathology relevant to Alzheimer's disease.

Impact of Non-pharmacological Chronic Hypertension on a Transgenic Rat Model of Cerebral Amyloid Angiopathy.

Cerebral amyloid angiopathy (CAA), a common comorbidity of Alzheimer’s disease (AD), is a cerebral small vessel disease (CSVD) characterized by deposition of fibrillar amyloid β (Aβ) in blood vessels of the brain and promotes neuroinflammation and vascular cognitive impairment and dementia (VCID). Hypertension, a prominent non-amyloidal CSVD, has been found to increase risk of dementia, but clinical data regarding its effects in CAA patients is controversial. To understand the effects of hypertension on CAA, we bred rTg-DI transgenic rats, a model of CAA, with spontaneously hypertensive, stroke prone (SHR-SP) rats producing bigenic rTg-DI/SHR-SP and non-transgenic SHR-SP littermates. At 7 months (M) of age, cohorts of both rTg-DI/SHR-SP and SHR-SP littermates exhibit elevated systolic blood pressures. However, transgene human amyloid β-protein (Aβ) precursor and Aβ peptide levels, as well as behavioral testing showed no changes between bigenic rTg-DI/SHR-SP and rTg-DI rats. Subsequent cohorts of rats were aged further to 10 M where bigenic rTg-DI/SHR-SP and SHR-SP littermates exhibit elevated systolic and diastolic blood pressures. Vascular amyloid load in hippocampus and thalamus was significantly decreased, whereas pial surface vessel amyloid increased, in bigenic rTg-DI/SHR-SP rats compared to rTg-DI rats suggesting a redistribution of vascular amyloid in bigenic animals. There was activation of both astrocytes and microglia in rTg-DI rats and bigenic rTg-DI/SHR-SP rats not observed in SHR-SP rats indicating that glial activation was likely in response to the presence of vascular amyloid. Thalamic microbleeds were present in both rTg-DI rats and bigenic rTg-DI/SHR-SP rats. Although the number of thalamic small vessel occlusions were not different between rTg-DI and bigenic rTg-DI/SHR-SP rats, a significant difference in occlusion size and distribution in the thalamus was found. Proteomic analysis of cortical tissue indicated that bigenic rTg-DI/SHR-SP rats largely adopt features of the rTg-DI rats with enhancement of certain changes. Our findings indicate that at 10 M of age non-pharmacological hypertension in rTg-DI rats causes a redistribution of vascular amyloid and significantly alters the size and distribution of thalamic occluded vessels. In addition, our findings indicate that bigenic rTg-DI/SHR-SP rats provide a non-pharmacological model to further study hypertension and CAA as co-morbidities for CSVD and VCID.

Long-term exercise pre-training attenuates Alzheimer's disease-related pathology in a transgenic rat model of Alzheimer's disease.

Alzheimer'sdisease (AD) is the most common form of dementia. Despite enormous efforts around the world, there remains no effective cure for AD. This study was performed to investigate the effects of long-term exercise pretreatment on the typical pathology of AD in a novel transgenic AD rat model. Male 2-month-old animals were divided into the following groups: wild-type (WT) rats, AD rats, and AD rats with treadmill exercise pretreatment (AD-Exe). After exercise pretreatment, the Barnes maze task, passive avoidance task, and cued fear conditioning test were performed to test learning and memory function. The elevated plus maze, open field test, sucrose preference test, and forced swim test were conducted to measure anxious-depressive-like behavior. Immunofluorescence staining, Golgi staining, transmission electron microscopy, Western blot analysis, F-Jade C staining, TUNEL staining, and related assay kits were conducted to measure Aβ plaques, tau hyperphosphorylation, neuronal damage, neuronal degeneration, dendritic spine density, synapses, synaptic vesicles, mitochondrial morphology, mitochondrial dynamic, oxidative stress, and neuroinflammation. Behavioral tests revealed that long-term exercise pretreatment significantly alleviated learning and memory dysfunction and anxious-depressive-like behaviors in AD animals. In addition, exercise pretreatment attenuated amyloid-β deposition and tau hyperphosphorylation and preserved spine density, synapses, and presynaptic vesicles. Exercise also inhibited neuronal damage, neuronal apoptosis, and neuronal degeneration. Additional studies revealed the imbalance of mitochondrial dynamics was significantly inhibited by exercise pretreatment accompanied by a remarkable suppression of oxidative stress and neuroinflammation. Our findings suggest that long-term exercise pretreatment alleviated behavioral deficits and typical pathologies of the AD rat model, supporting long-term exercise pretreatment as a potential approach to delay the progression of AD.

Longitudinal assessment of skilled forelimb motor impairments in DJ-1 knockout rats

BackgroundDJ-1 knockout (DJ-1 KO) rats exhibit a moderate parkinsonian phenotype, with gross motor deficits and ca. 50% loss of midbrain dopaminergic neurons appearing around 6–8 months of age. Fine motor impairments are often observed in Parkinson’s disease (PD), but skilled motor function in recently developed transgenic rat models of PD is not well characterized. ObjectivesTo assess the longitudinal performance of DJ-1 KO rats on a skilled forelimb reaching task. MethodsDJ-1 KO and wild-type (WT) rats were trained from 2 to 10 months of age on an isometric pullbar task designed to test forelimb strength and coordination. After 36 consecutive weeks of training (ca. 10 months old), task difficulty was then increased to challenge the motor capabilities of the DJ-1 KO rats. Throughout the study, subjects also received weekly assessments of gross locomotor activity in an open field. ResultsPull-task performance of the DJ-1 KO rats was impaired compared to WT, with deficits reaching significance around 7–9 months of age. When challenged, DJ-1 KO rats were able to exert increased force on the pullbar but continued to exhibit deficits compared to WT rats. Throughout the study, no differences in distance traveled or rearing frequency were observed in the open field, but DJ-1 KO rats were found to spend significantly more time in the center of the open field than WT rats. ConclusionsUsing a sensitive, automated assay of forelimb strength and coordination, we find that skilled forelimb motor performance is impaired in DJ-1 KO rats.

TOFACITINIB TREATMENT PREVENTS POST-OPERATIVE RECURRENCE OF CROHN’S DISEASE MODELED BY ILEOCECAL RESECTION IN HLA-B27 TRANSGENIC RATS

Abstract BACKGROUND Post-operative recurrence (POR) after ileocecal resection (ICR) affects most of Crohn’s disease (CD) patients within 3-5 years after surgery. Current immunomodulatory treatments have not proven efficiency in preventing POR, except for anti-TNFα biologic agents. AIM To evaluate the efficacy of the Janus Kinase inhibitor Tofacitinib to prevent POR after ICR in HLA-B27 transgenic rat model (TgB27) operated on an ICR. METHODS Thirty-three rats (strain F344, 29 TgB27, 4 control non Tg (nTg) rats) were operated on an ICR at the 12th week of life and were sacrificed at the 18th week of life. Tofacitinib (15 mg/kg, n=17) or placebo (n=16) were daily administered by oral gavage two weeks before surgery (10th week of life) until sacrifice. Anastomotic recurrence was blindly analyzed using macroscopic (from 0 to 4) and histologic (from 0 to 6) scores. Luminal microbiome was analyzed by shotgun metagenomic sequencing (Hiseq Illumina) in 9/33 rats before (week 9) and after Tofacitinib treatment or placebo (week 12), as well as 6 weeks following surgery (week 18). STAT3 phosphorylation was quantified in ileal samples by western blotting. Data were expressed by median with IQR. Comparisons were performed using not parametric two tailed Mann-Whitney analysis for unmatched data and Wilcoxon matched-pairs test for matched data. Two tailed χ2 test was used for contingency analysis. Spearman rank correlation was used for microbiota analysis. RESULTS 8/14 TgB27 rats receiving placebo (57%) showed signs of POR (macroscopic score ≥ 2) which were significantly prevented in 2/15 TgB27 rats (13%) treated with Tofacitinib (p= 0.013). nTg animals did not show macroscopic signs of POR. Macroscopic lesions were located 2 cm around the anastomosis in the TgB27 placebo group and consisted in ulcerations with a score of 2 (1-2.25). 11/15 TgB27 rats (73%) treated with Tofacitinib did not show macroscopic lesions and their score were significantly improved (0 (0-1), p= 0,0006). Histologic scores were significantly higher in TgB27 placebo group vs TgB27 Tofacitinib-treated rats (3 (2-4) vs 2 (1-3), p=0.036). Tofacitinib did not impact on alpha diversity and the relative abundance of bacterial taxa either before and after surgery. In contrast, surgery led to a significant 47% decrease of alpha diversity (p=0.0008) and loss of specific taxa in both TgB27 and nTg animals. No correlation was found between individual lesion scores and alpha diversity indexes. Ileal pSTAT3/STAT3 ratios were decreased by 80% in TgB27 rats treated with Tofacitinib (n=4) compared to placebo group (n=4) (0.3 ± 0,16 vs 1.58 ± 0,3, p=0,028). CONCLUSION We develop a reliable model of ICR in TgB27 rats mimicking the POR of CD. Tofacitinib prevents the macroscopic and histologic POR after ICR, without major modifications of the microbioma. ACKNOWLEDGMENTS Charity Foundation DigestScience and Pfizer SAS.

P602 Tofacitinib treatment prevents post-operative recurrence of Crohn’s Disease modeled by ileocecal resection in HLA-B27 transgenic rats

Abstract Background Post-operative recurrence (POR) after ileocecal resection (ICR) affects most of Crohn’s disease (CD) patients. Immunomodulatory treatments have not proven efficiency in preventing POR except for anti-TNFα biologic agents. We evaluate the efficacy of the JAK inhibitor Tofacitinib to prevent POR after ICR in HLA-B27 transgenic rat model (TgB27). Methods Thirty-three rats (strain F344, 29 TgB27, 4 control non Tg (nTg) rats) were operated on an ICR at the 12th week (W12) of life and were sacrificed at W18. Tofacitinib (15 mg/kg, n=17) or placebo (n=16) were daily administered by oral gavage at W10 until W18. Anastomotic recurrence were blindly analyzed using macroscopic (from 0 to 4) and histologic (from 0 to 6) scores. Luminal microbiome was analyzed by shotgun metagenomic sequencing (Hiseq Illumina) in 9/33 rats before (W9) and after Tofacitinib treatment or placebo (W12 and W18). STAT3 phosphorylation was quantified in ileal samples by western blotting. Data were expressed by median with IQR. Comparisons were performed using not parametric two tailed Mann-Whitney analysis for unmatched data and Wilcoxon matched-pairs test for matched data. Two tailed χ2 test was used for contingency analysis. Spearman rank correlation was used for microbiota analysis. Results 8/14 TgB27 rats receiving placebo (57%) showed signs of POR (macroscopic score ≥ 2) which were significantly prevented in 2/15 TgB27 rats (13%) treated with Tofacitinib (p= 0.013). nTg animals did not show macroscopic signs of POR. Macroscopic lesions were located 2 cm around the anastomosis in the TgB27 placebo group and consisted in ulcerations with a score of 2 (1–2.25). 11/15 TgB27 rats (73%) treated with Tofacitinib did not show macroscopic lesions and their score were significantly improved (0 (0–1), p= 0,0006). Histologic scores were significantly higher in TgB27 placebo group vs TgB27 Tofacitinib-treated rats (3 (2–4) vs 2 (1–3), p=0.036). Tofacitinib did not impact on alpha diversity and the relative abundance of bacterial taxa either before and after surgery. In contrast, surgery led to a significant 47% decrease of alpha diversity (p=0.0008) and loss of specific taxa in both TgB27 and nTg animals. No correlation was found between individual lesion scores and alpha diversity indexes. Ileal pSTAT3/STAT3 ratios were decreased by 80% in TgB27 rats treated with Tofacitinib (n=4) compared to placebo group (n=4) (0.3 ± 0,16 vs 1.58 ± 0,3, p=0,028). Conclusion We develop a reliable model of ICR in TgB27 rats mimicking the POR of CD. Tofacitinib prevents the macroscopic and histologic POR after ICR, without major modifications of the microbioma. Acknowledgments: Charity Foundation DigestScience and Pfizer SAS

Dual Blockade of TNF and IL-17A Inhibits Inflammation and Structural Damage in a Rat Model of Spondyloarthritis

The tumor necrosis factor (TNF) and IL-23/IL-17 axes are the main therapeutic targets in spondyloarthritis. Despite the clinical efficacy of blocking either pathway, monotherapy does not induce remission in all patients and its effect on new bone formation remains unclear. We aimed to study the effect of TNF and IL-17A dual inhibition on clinical disease and structural damage using the HLA-B27/human β2-microglobulin transgenic rat model of SpA. Immunized rats were randomized according to arthritis severity, 1 week after arthritis incidence reached 50%, to be treated twice weekly for a period of 5 weeks with either a dual blockade therapy of an anti-TNF antibody and an anti-IL-17A antibody, a single therapy of either antibody, or PBS as vehicle control. Treatment-blinded observers assessed inflammation and structural damage clinically, histologically and by micro-CT imaging. Both single therapies as well as TNF and IL-17A dual blockade therapy reduced clinical spondylitis and peripheral arthritis effectively and similarly. Clinical improvement was confirmed for all treatments by a reduction of histological inflammation and pannus formation (p < 0.05) at the caudal spine. All treatments showed an improvement of structural changes at the axial and peripheral joints on micro-CT imaging, with a significant decrease for roughness (p < 0.05), which reflects both erosion and new bone formation, at the level of the caudal spine. The effect of dual blockade therapy on new bone formation was more prominent at the axial than the peripheral level. Collectively, our study showed that dual blockade therapy significantly reduces inflammation and structural changes, including new bone formation. However, we could not confirm a more pronounced effect of dual inhibition compared to single inhibition.

RTg-D: A novel transgenic rat model of cerebral amyloid angiopathy Type-2.

Cerebral amyloid angiopathy (CAA) is common disorder of the elderly, a prominent comorbidity of Alzheimer's disease, and causes vascular cognitive impairment and dementia. Previously, we generated a transgenic rat model of capillary CAA type-1 that develops many pathological features of human disease. However, a complementary rat model of larger vessel CAA type-2 disease has been lacking. A novel transgenic rat model (rTg-D) was generated that produces human familial CAA Dutch E22Q mutant amyloid β-protein (Aβ) in brain and develops larger vessel CAA type-2. Quantitative biochemical and pathological analyses were performed to characterize the progression of CAA and associated pathologies in aging rTg-D rats. rTg-D rats begin to accumulate Aβ in brain and develop varying levels of larger vessel CAA type-2, in the absence of capillary CAA type-1, starting around 18 months of age. Larger vessel CAA was mainly composed of the Aβ40 peptide and most prominent in surface leptomeningeal/pial vessels and arterioles of the cortex and thalamus. Cerebral microbleeds and small vessel occlusions were present mostly in the thalamic region of affected rTg-D rats. In contrast to capillary CAA type-1 the amyloid deposited within the walls of larger vessels of rTg-D rats did not promote perivascular astrocyte and microglial responses or accumulate the Aβ chaperone apolipoprotein E. Although variable in severity, the rTg-D rats specifically develop larger vessel CAA type-2 that reflects many of the pathological features of human disease and provide a new model to investigate the pathogenesis of this condition.