Enhanced neuronal survival and BDNF elevation via long-term co-activation of galanin 2 (GALR2) and neuropeptide Y1 receptors (NPY1R): potential therapeutic targets for major depressive disorder

BACKGROUND

Major Depressive Disorder (MDD) is a prevalent and debilitating condition, necessitating novel therapeutic strategies due to the limited efficacy and adverse effects of current treatments. We explored how galanin receptor 2 (GALR2) and Neuropeptide Y1 Receptor (NPYY1R) agonists, working together, can boost brain cell growth and increase antidepressant-like effects in rats. This suggests new ways to treat Major Depressive Disorder (MDD).

RESEARCH DESIGN AND METHODS

In a controlled laboratory setting, adult naive Sprague-Dawley rats were administered directly into the brain's ventricles, a method known as intracerebroventricular (ICV) administration, with GALR2 agonist (M1145), NPYY1R agonist, both, or in combination with a GALR2 antagonist (M871). Main outcome measures included long-term neuronal survival, differentiation, and behavioral.

RESULTS

Co-administration of M1145 and NPYY1R agonist significantly enhanced neuronal survival and maturation in the ventral dentate gyrus, with a notable increase in Brain-Derived Neurotrophic Factor (BDNF) expression. This neurogenic effect was associated with an antidepressant-like effect, an outcome partially reversed by M871.

CONCLUSIONS

GALR2 and NPYY1R agonists jointly promote hippocampal neurogenesis and exert antidepressant-like effects in rats without adverse outcomes, highlighting their therapeutic potential for MDD. The study's reliance on an animal model and intracerebroventricular delivery warrants further clinical exploration to confirm these promising results.

Establishment of animal models and behavioral studies for autism spectrum disorders

In recent years, the incidence of autism spectrum disorder (ASD) has increased, but the etiology and pathogenesis remain unclear. In this narrative review, we review and systematically summarize the methods used to construct animal models to study ASD and the related behavioral studies based on recent literature. Utilization of various ASD animal models can complement research on the etiology, pathogenesis, and core behaviors of ASD, providing information and a foundation for further basic research and clinical treatment of ASD.

Rodent models of AKI and AKI-CKD transition: an update in 2024

Despite known drawbacks, rodent models are essential tools in the research of renal development, physiology, and pathogenesis. In the past decade, rodent models have been developed and used to mimic different etiologies of acute kidney injury (AKI), AKI to chronic kidney disease (CKD) transition or progression, and AKI with comorbidities. These models have been applied for both mechanistic research and preclinical drug development. However, current rodent models have their limitations, especially since they often do not fully recapitulate the pathophysiology of AKI in human patients, and thus need further refinement. Here, we discuss the present status of these rodent models, including the pathophysiologic compatibility, clinical translational significance, key factors affecting model consistency, and their main limitations. Future efforts should focus on establishing robust models that simulate the major clinical and molecular phenotypes of human AKI and its progression.

An Assessment of Physical and N6-Cyclohexyladenosine-Induced Hypothermia in Rodent Distal Focal Ischemic Stroke

Therapeutic hypothermia (TH) mitigates damage in ischemic stroke models. However, safer and easier TH methods (e.g., pharmacological) are needed to circumvent physical cooling complications. This study evaluated systemic and pharmacologically induced TH using the adenosine A1 receptor agonist, N6-cyclohexyladenosine (CHA), with control groups in male Sprague-Dawley rats. CHA was administered intraperitoneally 10 minutes following a 2-hour intraluminal middle cerebral artery occlusion. We used a 1.5 mg/kg induction dose, followed by three 1.0 mg/kg doses every 6 hours for a total of 4 doses, causing 20-24 hours of hypothermia. Animals assigned to physical hypothermia and CHA-hypothermia had similar induction rates and nadir temperatures, but forced cooling lasted ∼6 hours longer compared with CHA-treated animals. The divergence is likely attributable to individual differences in CHA metabolism, which led to varied durations at nadir, whereas physical hypothermia was better regulated. Physical hypothermia significantly reduced infarction (primary endpoint) on day 7 (mean reduction of 36.8 mm3 or 39% reduction; p = 0.021 vs. normothermic animals; Cohen's d = 0.75), whereas CHA-induced hypothermia did not (p = 0.33). Similarly, physical cooling improved neurological function (physical hypothermia median = 0, physical normothermia median = 2; p = 0.008) and CHA-induced cooling did not (p > 0.99). Our findings demonstrate that forced cooling was neuroprotective compared with controls, but prolonged CHA-induced cooling was not neuroprotective.

Antidepressant-like Effect of the Eburnamine-Type Molecule Vindeburnol in Rat and Mouse Models of Ultrasound-Induced Depression

Vindeburnol (VIND, RU24722, BC19), a synthetic molecule derived from the eburnamine-vincamine alkaloid group, has many neuropsychopharmacological effects, but its antidepressant-like effects are poorly understood and have only been described in a few patents. To reliably estimate this effect, vindeburnol was studied in a model of long-term variable-frequency ultrasound (US) exposure at 20-45 kHz in male Wistar rats and BALB/c mice. Vindeburnol was administered chronically for 21 days against a background of simultaneous ultrasound exposure at a dose of 20 mg/kg intraperitoneally (IP). Using four behavioral tests, the sucrose preference test (SPT), the social interaction test (SIT), the open field test (OFT), and the forced swimming test (FST), we found that the treatment with the compound diminished depression-like symptoms in mice and rats. The compound restored the ultrasound-related reduced sucrose consumption to control levels and increased social interaction time in mice and rats compared with those in ultrasound-exposed animals. Vindeburnol showed contraversive results of horizontal and vertical activity in both species and generally did not increase locomotor activity. At the same time, the compound showed a specific effect in the FST, significantly reducing the immobility time. Moreover, we found an increase in norepinephrine, dopamine, and its metabolite levels in the brainstem, as well as an increase in dopamine, 3-methoxytyramine, and 3,4-dihydroxyphenylacetic acid levels in the striatum. We also observed a statistically significant increase in tyrosine hydroxylase (TH) levels in the region containing the locus coeruleus (LC). We suggest that using its distinct chemical structure and pharmacological activity as a starting point could boost antidepressant drug discovery.

The rodent models of arteriovenous fistula

Arteriovenous fistulas (AVFs) have long been used as dialysis access in patients with end-stage renal disease; however, their maturation and long-term patency still fall short of clinical needs. Rodent models are irreplaceable to facilitate the study of mechanisms and provide reliable insights into clinical problems. The ideal rodent AVF model recapitulates the major features and pathology of human disease as closely as possible, and pre-induction of the uremic milieu is an important addition to AVF failure studies. Herein, we review different surgical methods used so far to create AVF in rodents, including surgical suturing, needle puncture, and the cuff technique. We also summarize commonly used evaluations after AVF placement. The aim was to provide recent advances and ideas for better selection and induction of rodent AVF models. At the same time, further improvements in the models and a deeper understanding of AVF failure mechanisms are expected.

Dense dopaminergic innervation of the peri-infarct cortex despite dopaminergic cell loss after a pure motor-cortical stroke in rats

After ischemic stroke, the cortex directly adjacent to the ischemic core (i.e., the peri-infarct cortex, PIC) undergoes plastic changes that facilitate motor recovery. Dopaminergic signaling is thought to support this process. However, ischemic stroke also leads to the remote degeneration of dopaminergic midbrain neurons, possibly interfering with this beneficial effect. In this study, we assessed the reorganization of dopaminergic innervation of the PIC in a rat model of focal cortical stroke. Adult Sprague-Dawley rats either received a photothrombotic stroke (PTS) in the primary motor cortex (M1) or a sham operation. 30 days after PTS or sham procedure, the retrograde tracer Micro Ruby (MR) was injected into the PIC of stroke animals or into homotopic cortical areas of matched sham rats. Thus, dopaminergic midbrain neurons projecting into the PIC were identified based on MR signal and immunoreactivity against tyrosine hydroxylase (TH), a marker for dopaminergic neurons. The density of dopaminergic innervation within the PIC was assessed by quantification of dopaminergic boutons indicated by TH-immunoreactivity. Regarding postsynaptic processes, expression of dopamine receptors (D1- and D2) and a marker of the functional signal cascade (DARPP-32) were visualized histologically. Despite a 25% ipsilesional loss of dopaminergic midbrain neurons after PTS, the number and spatial distribution of dopaminergic neurons projecting to the PIC was not different compared to sham controls. Moreover, the density of dopaminergic innervation in the PIC was significantly higher than in homotopic cortical areas of the sham group. Within the PIC, D1-receptors were expressed in neurons, whereas D2-receptors were confined to astrocytes. The intensity of D1- and DARPP-32 expression appeared to be higher in the PIC compared to the contralesional homotopic cortex. Our data suggest a sprouting of dopaminergic fibers into the PIC and point to a role for dopaminergic signaling in reparative mechanisms post-stroke, potentially related to recovery.

Tibolone Improves Locomotor Function in a Rat Model of Spinal Cord Injury by Modulating Apoptosis and Autophagy

Spinal cord injury (SCI) harms patients' health and social and economic well-being. Unfortunately, fully effective therapeutic strategies have yet to be developed to treat this disease, affecting millions worldwide. Apoptosis and autophagy are critical cell death signaling pathways after SCI that should be targeted for early therapeutic interventions to mitigate their adverse effects and promote functional recovery. Tibolone (TIB) is a selective tissue estrogen activity regulator (STEAR) with neuroprotective properties demonstrated in some experimental models. This study aimed to investigate the effect of TIB on apoptotic cell death and autophagy after SCI and verify whether TIB promotes motor function recovery. A moderate contusion SCI was produced at thoracic level 9 (T9) in male Sprague Dawley rats. Subsequently, animals received a daily dose of TIB orally and were sacrificed at 1, 3, 14 or 30 days post-injury. Tissue samples were collected for morphometric and immunofluorescence analysis to identify tissue damage and the percentage of neurons at the injury site. Autophagic (Beclin-1, LC3-I/LC3-II, p62) and apoptotic (Caspase 3) markers were also analyzed via Western blot. Finally, motor function was assessed using the BBB scale. TIB administration significantly increased the amount of preserved tissue (p < 0.05), improved the recovery of motor function (p < 0.001) and modulated the expression of autophagy markers in a time-dependent manner while consistently inhibiting apoptosis (p < 0.05). Therefore, TIB could be a therapeutic alternative for the recovery of motor function after SCI.

The Rehabilitation Potential of Neurostimulation for Mild Traumatic Brain Injury in Animal and Human Studies

Neurostimulation carries high therapeutic potential, accompanied by an excellent safety profile. In this review, we argue that an arena in which these tools could provide breakthrough benefits is traumatic brain injury (TBI). TBI is a major health problem worldwide, with the majority of cases identified as mild TBI (mTBI). MTBI is of concern because it is a modifiable risk factor for dementia. A major challenge in studying mTBI is its inherent heterogeneity across a large feature space (e.g., etiology, age of injury, sex, treatment, initial health status, etc.). Parallel lines of research in human and rodent mTBI can be collated to take advantage of the full suite of neuroscience tools, from neuroimaging (electroencephalography: EEG; functional magnetic resonance imaging: fMRI; diffusion tensor imaging: DTI) to biochemical assays. Despite these attractive components and the need for effective treatments, there are at least two major challenges to implementation. First, there is insufficient understanding of how neurostimulation alters neural mechanisms. Second, there is insufficient understanding of how mTBI alters neural function. The goal of this review is to assemble interrelated but disparate areas of research to identify important gaps in knowledge impeding the implementation of neurostimulation.

System Biology Investigation Revealed Lipopolysaccharide and Alcohol-Induced Hepatocellular Carcinoma Resembled Hepatitis B Virus Immunobiology and Pathogenesis

Hepatitis B infection caused by the hepatitis B virus is a life-threatening cause of liver fibrosis, cirrhosis, and hepatocellular carcinoma. Researchers have produced multiple in vivo models for hepatitis B virus (HBV) and, currently, there are no specific laboratory animal models available to study HBV pathogenesis or immune response; nonetheless, their limitations prevent them from being used to study HBV pathogenesis, immune response, or therapeutic methods because HBV can only infect humans and chimpanzees. The current study is the first of its kind to identify a suitable chemically induced liver cirrhosis/HCC model that parallels HBV pathophysiology. Initially, data from the peer-reviewed literature and the GeneCards database were compiled to identify the genes that HBV and seven drugs (acetaminophen, isoniazid, alcohol, D-galactosamine, lipopolysaccharide, thioacetamide, and rifampicin) regulate. Functional enrichment analysis was performed in the STRING server. The network HBV/Chemical, genes, and pathways were constructed by Cytoscape 3.6.1. About 1546 genes were modulated by HBV, of which 25.2% and 17.6% of the genes were common for alcohol and lipopolysaccharide-induced hepatitis. In accordance with the enrichment analysis, HBV activates the signaling pathways for apoptosis, cell cycle, PI3K-Akt, TNF, JAK-STAT, MAPK, chemokines, NF-kappa B, and TGF-beta. In addition, alcohol and lipopolysaccharide significantly activated these pathways more than other chemicals, with higher gene counts and lower FDR scores. In conclusion, alcohol-induced hepatitis could be a suitable model to study chronic HBV infection and lipopolysaccharide-induced hepatitis for an acute inflammatory response to HBV.

DYNAMIC METABOLIC CHANGES OBSERVED IN AN LPS-INDUCED SYSTEMIC INFLAMMATION RAT MODEL USING CONTINUOUS LONG-TERM INDIRECT CALORIMETRY EXPERIMENTS

ABSTRACT

Background : Nutritional management is crucial for severely ill patients. Measuring metabolism is believed to be necessary for the acute sepsis phase to accurately estimate nutrition. Indirect calorimetry (IDC) is assumed to be useful for acute intensive care; however, there are few studies on long-term IDC measurement in patients with systemic inflammation. Methods : Rats were categorized into the LPS received or control groups; LPS rats were categorized into underfeeding (UF), adjusted feeding (AF), and overfeeding (OF) groups. Indirect calorimetry measurement was performed until 72 or 144 h. Body composition was measured at -24 and 72 or 144 h, and tissue weight was measured at 72 or 144 h. Results : Low energy consumption and loss of diurnal variation of resting energy expenditure were observed in the LPS group compared with the control group until 72 h, after which the LPS group recovered. The resting energy expenditure in the OF group was higher than that in the UF and AF groups. In the first phase, low energy consumption was observed in all groups. In the second and third phases, higher energy consumption occurred in the OF group than in the UF and AF groups. In the third phase, diurnal variation recovered in all groups. Muscle atrophy caused body weight loss, but fat tissue loss did not occur. Conclusions : We observed metabolic changes with IDC during the acute systemic inflammation phase owing to differences in calorie intake. This is the first report of long-term IDC measurement using the LPS-induced systemic inflammation rat model.

Neurite Outgrowth and Gene Expression Profile Correlate with Efficacy of Human Induced Pluripotent Stem Cell-Derived Dopamine Neuron Grafts

Transplantation of human induced pluripotent stem cell-derived dopaminergic (iPSC-DA) neurons is a promising therapeutic strategy for Parkinson's disease (PD). To assess optimal cell characteristics and reproducibility, we evaluated the efficacy of iPSC-DA neuron precursors from two individuals with sporadic PD by transplantation into a hemiparkinsonian rat model after differentiation for either 18 (d18) or 25 days (d25). We found similar graft size and dopamine (DA) neuron content in both groups, but only the d18 cells resulted in recovery of motor impairments. In contrast, we report that d25 grafts survived equally as well and produced grafts rich in tyrosine hydroxylase-positive neurons, but were incapable of alleviating any motor deficits. We identified the mechanism of action as the extent of neurite outgrowth into the host brain, with d18 grafts supporting significantly more neurite outgrowth than nonfunctional d25 grafts. RNAseq analysis of the cell preparation suggests that graft efficacy may be enhanced by repression of differentiation-associated genes by REST, defining the optimal predifferentiation state for transplantation. This study demonstrates for the first time that DA neuron grafts can survive well in vivo while completely lacking the capacity to induce recovery from motor dysfunction. In contrast to other recent studies, we demonstrate that neurite outgrowth is the key factor determining graft efficacy and our gene expression profiling revealed characteristics of the cells that may predict their efficacy. These data have implication for the generation of DA neuron grafts for clinical application.

Preclinical models of middle cerebral artery occlusion: new imaging approaches to a classic technique

Stroke remains a major burden on patients, families, and healthcare professionals, despite major advances in prevention, acute treatment, and rehabilitation. Preclinical basic research can help to better define mechanisms contributing to stroke pathology, and identify therapeutic interventions that can decrease ischemic injury and improve outcomes. Animal models play an essential role in this process, and mouse models are particularly well-suited due to their genetic accessibility and relatively low cost. Here, we review the focal cerebral ischemia models with an emphasis on the middle cerebral artery occlusion technique, a "gold standard" in surgical ischemic stroke models. Also, we highlight several histologic, genetic, and in vivo imaging approaches, including mouse stroke MRI techniques, that have the potential to enhance the rigor of preclinical stroke evaluation. Together, these efforts will pave the way for clinical interventions that can mitigate the negative impact of this devastating disease.

Cirrhotic Cardiomyopathy Following Bile Duct Ligation in Rats-A Matter of Time?

Cirrhotic patients often suffer from cirrhotic cardiomyopathy (CCM). Previous animal models of CCM were inconsistent concerning the time and mechanism of injury; thus, the temporal dynamics and cardiac vulnerability were studied in more detail. Rats underwent bile duct ligation (BDL) and a second surgery 28 days later. Cardiac function was assessed by conductance catheter and echocardiography. Histology, gene expression, and serum parameters were analyzed. A chronotropic incompetence (P_d31 < 0.001) and impaired contractility at rest and a reduced contractile reserve (P_d31 = 0.03, P_dob-d31 < 0.001) were seen 31 days after BDL with increased creatine (P_d35, P_d42, and P_d56 < 0.05) and transaminases (P_d31 < 0.001). A total of 56 days after BDL, myocardial fibrosis was seen (P_d56 < 0.001) accompanied by macrophage infiltration (CD68: P_group < 0.001) and systemic inflammation (TNFα: P_group < 0.001, white blood cell count: P_group < 0.001). Myocardial expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) was increased after 31 (P_d31 < 0.001) and decreased after 42 (P_d42 < 0.001) and 56 days (P_d56 < 0.001). Caspase-3 expression was increased 31 and 56 days after BDL (P_d31 = 0.005; P_d56 = 0.005). Structural changes in the myocardium were seen after 8 weeks. After the second surgery (second hit), transient myocardial insufficiency with secondary organ dysfunction was seen, characterized by reduced contractility and contractile reserve.

Short exposure to photo-oxidative damage triggers molecular signals indicative of early retinal degeneration

Introduction

Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world, currently affecting over 350 billion people globally. For the most prevalent late-stage form of this disease, atrophic AMD, there are no available prevention strategies or treatments, in part due to inherent difficulties in early-stage diagnosis. Photo-oxidative damage is a well-established model for studying inflammatory and cell death features that occur in late-stage atrophic AMD, however to date has not been investigated as a potential model for studying early features of disease onset. Therefore, in this study we aimed to determine if short exposure to photo-oxidative damage could be used to induce early retinal molecular changes and advance this as a potential model for studying early-stage AMD.

Methods

C57BL/6J mice were exposed to 1, 3, 6, 12, or 24h photo-oxidative damage (PD) using 100k lux bright white light. Mice were compared to dim-reared (DR) healthy controls as well as mice which had undergone long periods of photo-oxidative damage (3d and 5d-PD) as known timepoints for inducing late-stage retinal degeneration pathologies. Cell death and retinal inflammation were measured using immunohistochemistry and qRT-PCR. To identify retinal molecular changes, retinal lysates were sent for RNA sequencing, following which bioinformatics analyses including differential expression and pathway analyses were performed. Finally, to investigate modulations in gene regulation as a consequence of degeneration, microRNA (miRNA) expression patterns were quantified using qRT-PCR and visualized using in situ hybridization.

Results

Short exposure to photo-oxidative damage (1-24h-PD) induced early molecular changes in the retina, with progressive downregulation of homeostatic pathways including metabolism, transport and phototransduction observed across this time-course. Inflammatory pathway upregulation was observed from 3h-PD, preceding observable levels of microglia/macrophage activation which was noted from 6h-PD, as well as significant photoreceptor row loss from 24h-PD. Further rapid and dynamic movement of inflammatory regulator miRNA, miR-124-3p and miR-155-5p, was visualized in the retina in response to degeneration.

Conclusion

These results support the use of short exposure to photo-oxidative damage as a model of early AMD and suggest that early inflammatory changes in the retina may contribute to pathological features of AMD progression including immune cell activation and photoreceptor cell death. We suggest that early intervention of these inflammatory pathways by targeting miRNA such as miR-124-3p and miR-155-5p or their target genes may prevent progression into late-stage pathology.

Targeting proteostasis of the HEV replicase to combat infection in preclinical models

BACKGROUND & AIMS

Appropriate treatment options are lacking for hepatitis E virus (HEV)-infected pregnant women and immunocompromised individuals. Thus, we aimed to identify efficient anti-HEV drugs through high-throughput screening, validate them in vitro and in vivo (in a preclinical animal study), and elucidate their underlying antiviral mechanism of action.

METHODS

Using appropriate cellular and rodent HEV infection models, we studied a critical pathway for host-HEV interactions and performed a preclinical study of the corresponding antivirals, which target proteostasis of the HEV replicase.

RESULTS

We found 17 inhibitors that target HEV-HSP90 interactions by unbiased compound library screening on human hepatocytes harboring an HEV replicon. Inhibitors of HSP90 (iHSP90) markedly suppressed HEV replication with efficacy exceeding that of conventional antivirals (IFNα and ribavirin) in vitro. Mechanistically, iHSP90 treatment released the viral replicase ORF1 protein from the ORF1-HSP90 complex and triggered rapid ubiquitin/proteasome-mediated degradation of ORF1, resulting in abrogated HEV replication. Furthermore, a preclinical trial in a Mongolian gerbil HEV infection model showed this novel anti-HEV strategy to be safe, efficient, and able to prevent HEV-induced liver damage.

CONCLUSIONS

In this study, we uncover a proteostatic pathway that is critical for host-HEV interactions and we provide a foundation from which to translate this new understanding of the HEV life cycle into clinically promising antivirals.

IMPACT AND IMPLICATIONS

Appropriate treatment options for hepatitis E virus (HEV)-infected pregnant women and immunocompromised patients are lacking; hence, there is an urgent need for safe and effective HEV-specific therapies. This study identified new antivirals (inhibitors of HSP90) that significantly limit HEV infection by targeting the viral replicase for degradation. Moreover, these anti-HEV drugs were validated in an HEV rodent model and were found to be safe and efficient for prevention of HEV-induced liver injury in preclinical experiments. Our findings substantially promote the understanding of HEV pathobiology and pave the way for antiviral development.

Acellular Dermal Matrix Susceptibility to Collagen Digestion: Effect on Mechanics and Host Response

Various tissue origins and manufacturing processes can differentially affect the retention of native properties of acellular dermal matrices (ADMs); however, comparative studies are limited. Head-to-head comparisons between different configurations of porcine-derived Strattice (Allergan Aesthetics, an AbbVie Company, Irvine, CA) and bovine-derived SurgiMend (Integra LifeSciences, Billerica, MA) ADMs were performed to evaluate mechanical integrity and host tissue biologic response. Thermodynamic profile and morphology, which affect retention of mechanical strength, were evaluated through differential scanning calorimetry, scanning electron microscopy, and histology. Mechanical strength was assessed through tensile testing following collagenase exposure in vitro and following subcutaneous implantation in a rodent model. Host biologic response was evaluated through histopathology. Compared with respective native tissues, reductions in onset melting temperature following tissue processing were smaller for Strattice Firm versus SurgiMend 1.0 (Δ0.79°C vs. Δ5.77°C), Strattice Extra Thick versus SurgiMend 3.0 (Δ1.57°C vs. Δ4.79°C), and Strattice Perforated versus SurgiMend Microperforated (Δ1.18°C vs. Δ7.76°C), with similar trends for peak melting temperature. Strattice maintained native dermal architecture versus compacted collagen with process-induced interstices observed for SurgiMend. Strattice Firm, Extra Thick, and Perforated retained 33.44%, 65.65%, and 17.20% of initial strength after 48 h exposure to excess collagenase, while the SurgiMend ADMs were completely digested by 48 h. At 6 weeks postimplantation, both Strattice and SurgiMend showed minimal inflammatory response, but greater fibroblast repopulation was evident for Strattice. Strattice Firm had higher maximum load (145.85 ± 33.05 N/cm vs. 24.29 ± 12.35 N/cm, p ≤ 0.01), maximum stress (8.20 ± 1.91 MPa vs. 2.24 ± 1.27 Mpa, p ≤ 0.01), and stiffness (7491.00 ± 1981.32 N/cm vs. 737.56 ± 292.55 N/cm, p ≤ 0.01) than SurgiMend 1.0. Strattice Extra Thick had lower maximum load (198.54 ± 58.79 N/cm vs. 303.08 ± 76.76 N/cm, p < 0.05) than SurgiMend 3.0, but similar maximum stress (6.96 ± 1.78 Mpa vs. 8.73 ± 2.15 Mpa) and stiffness (13386.11 ± 3123.28 N/cm vs. 9389.02 ± 4860.67 N/cm). Strattice Perforated had higher maximum load (72.65 ± 41.44 N/cm vs. 10.23 ± 4.67 N/cm, p < 0.05) and maximum stress (4.08 ± 2.08 Mpa vs. 0.44 ± 0.19 p < 0.05) than SurgiMend Microperforated. Maximum load retention rates following implantation were higher for Strattice Firm versus SurgiMend 1.0 (37.85% vs. 8.03%), Strattice Extra Thick versus SurgiMend 3.0 (45.03% vs. 37.80%), and Strattice Perforated versus SurgiMend Microperforated (28.04% vs. 6.21%). Similar results were obtained for maximum stress and stiffness. In conclusion, Strattice retained greater mechanical strength in vitro and in vivo, while exhibiting greater fibroblast cell infiltration.

Rodent Models of Dilated Cardiomyopathy and Heart Failure for Translational Investigations and Therapeutic Discovery

Even with modern therapy, patients with heart failure only have a 50% five-year survival rate. To improve the development of new therapeutic strategies, preclinical models of disease are needed to properly emulate the human condition. Determining the most appropriate model represents the first key step for reliable and translatable experimental research. Rodent models of heart failure provide a strategic compromise between human in vivo similarity and the ability to perform a larger number of experiments and explore many therapeutic candidates. We herein review the currently available rodent models of heart failure, summarizing their physiopathological basis, the timeline of the development of ventricular failure, and their specific clinical features. In order to facilitate the future planning of investigations in the field of heart failure, a detailed overview of the advantages and possible drawbacks of each model is provided.

Changes in Plasma Metabolomic Profile Following Bariatric Surgery, Lifestyle Intervention or Diet Restriction-Insights from Human and Rat Studies

Although bariatric surgery is known to change the metabolome, it is unclear if this is specific for the intervention or a consequence of the induced bodyweight loss. As the weight loss after Roux-en-Y Gastric Bypass (RYGB) can hardly be mimicked with an evenly effective diet in humans, translational research efforts might be helpful. A group of 188 plasma metabolites of 46 patients from the randomized controlled Würzburg Adipositas Study (WAS) and from RYGB-treated rats (n = 6) as well as body-weight-matched controls (n = 7) were measured using liquid chromatography tandem mass spectrometry. WAS participants were randomized into intensive lifestyle modification (LS, n = 24) or RYGB (OP, n = 22). In patients in the WAS cohort, only bariatric surgery achieved a sustained weight loss (BMI -34.3% (OP) vs. -1.2% (LS), p ≤ 0.01). An explicit shift in the metabolomic profile was found in 57 metabolites in the human cohort and in 62 metabolites in the rodent model. Significantly higher levels of sphingolipids and lecithins were detected in both surgical groups but not in the conservatively treated human and animal groups. RYGB leads to a characteristic metabolomic profile, which differs distinctly from that following non-surgical intervention. Analysis of the human and rat data revealed that RYGB induces specific changes in the metabolome independent of weight loss.

Sympathetic Denervation and Pharmacological Stimulation of Parasympathetic Nervous System Prevent Pulmonary Vascular Bed Remodeling in Rat Model of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) develops in 1.5-2.0% of patients experiencing pulmonary embolism (PE) and is characterized by stable pulmonary artery obstruction, heart failure, and poor prognosis. Little is known about involvement of autonomic nervous system (ANS) in the mechanisms of CTEPH. This study was aimed at evaluation of the effect of vagal and sympathetic denervation, as well as stimulation of the parasympathetic nervous system, on the outcomes of CTEPH in rats. CTEPH was induced by multiple intravenous injections of alginate microspheres. Sympathetic and vagal denervation was performed using unilateral surgical ablation of the stellate ganglion and vagotomy, respectively. Stimulation of the parasympathetic nervous system was carried out by administering pyridostigmine. The effect of neuromodulatory effects was assessed in terms of hemodynamics, histology, and gene expression. The results demonstrated the key role of ANS in the development of CTEPH. Sympathetic denervation as well as parasympathetic stimulation resulted in attenuated pulmonary vascular remodeling. These salutary changes were associated with altered MMP2 and TIMP1 expression in the lung and decreased FGFb level in the blood. Unilateral vagotomy had no effect on physiological and morphological outcomes of the study. The data obtained contribute to the identification of new therapeutic targets for CTEPH treatment.

Dysregulated UPR and ER Stress Related to a Mutation in the Sdf2l1 Gene Are Involved in the Pathophysiology of Diet-Induced Diabetes in the Cohen Diabetic Rat

The Cohen Diabetic rat is a model of type 2 diabetes mellitus that consists of the susceptible (CDs/y) and resistant (CDr/y) strains. Diabetes develops in CDs/y provided diabetogenic diet (DD) but not when fed regular diet (RD) nor in CDr/y given either diet. We recently identified in CDs/y a deletion in Sdf2l1, a gene that has been attributed a role in the unfolded protein response (UPR) and in the prevention of endoplasmic reticulum (ER) stress. We hypothesized that this deletion prevents expression of SDF2L1 and contributes to the pathophysiology of diabetes in CDs/y by impairing UPR, enhancing ER stress, and preventing CDs/y from secreting sufficient insulin upon demand. We studied SDF2L1 expression in CDs/y and CDr/y. We evaluated UPR by examining expression of key proteins involved in both strains fed either RD or DD. We assessed the ability of all groups of animals to secrete insulin during an oral glucose tolerance test (OGTT) over 4 weeks, and after overnight feeding (postprandial) over 4 months. We found that SDF2L1 was expressed in CDr/y but not in CDs/y. The pattern of expression of proteins involved in UPR, namely the PERK (EIF2α, ATF4 and CHOP) and IRE1 (XBP-1) pathways, was different in CDs/y DD from all other groups, with consistently lower levels of expression at 4 weeks after initiation of DD and coinciding with the development of diabetes. In CDs/y RD, insulin secretion was mildly impaired, whereas in CDs/y DD, the ability to secrete insulin decreased over time, leading to the development of the diabetic phenotype. We conclude that in CDs/y DD, UPR participating proteins were dysregulated and under-expressed at the time point when the diabetic phenotype became overt. In parallel, insulin secretion in CDs/y DD became markedly impaired. Our findings suggest that under conditions of metabolic load with DD and increased demand for insulin secretion, the lack of SDF2L1 expression in CDs/y is associated with UPR dysregulation and ER stress which, combined with oxidative stress previously attributed to the concurrent Ndufa4 mutation, are highly likely to contribute to the pathophysiology of diabetes in this model.

Experimental Animal Models: Tools to Investigate Antidiabetic Activity

About 2.8% of the global population are being suffered from Diabetes mellitus. Diabetes mellitus is a group of metabolic disorders that is characterized by an absolute lack of insulin and resulting in hyperglycemia. To overcome the challenges, many antidiabetic drugs are being used, and research is being carried out in search of more effective anti-diabetic drugs. To study the effectiveness of antidiabetic drugs, many diabetic models, chemicals, and diabetogenic hormones were used at the research level. In this review, we summarised various animal models used, chemicals that induce diabetes, their properties, and the mechanism of action of these models. Further, diabetes mellitus is generally induced in laboratory animals by several methods that include: chemical, surgical and genetic manipulations. To better understand both the pathogenesis and potential therapeutic agents, appropriate animal models of type 1 & type 2 diabetes mellitus are needed. However, for an animal model to have relevance to the study of diabetes, either the characteristics of the animal model should mirror the pathophysiology and natural history of diabetes or the model should develop complications of diabetes with an etiology similar to that of the human condition. There appears to be no single animal model that encompasses all of these characteristics, but there are many that provide very similar characteristics in one or more aspects of diabetes in humans. The use of the appropriate animal model based on these similarities can provide much-needed data on pathophysiological mechanisms operative in human diabetes.

Effects of bariatric surgery on drug pharmacokinetics-Preclinical studies

With the rising worldwide obesity rates, bariatric surgeries are increasing. Although the surgery offers an effective treatment option for weight loss, the procedure causes dramatic physiological and metabolic changes. Animal models in rodents provide a valuable tool for studying the systemic effects of the surgery. Since the surgery may significantly influence the pharmacokinetic properties of medications, animal studies should provide essential insight into mechanisms underlying changes in how the body handles the drug. This review summarizes research work in rodents regarding the impact of standard bariatric procedures on pharmacokinetics. A qualitative literature search was conducted via PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE. Studies that examined bariatric surgery's effects on drug pharmacokinetics in rodent models were included. Clinical studies and studies not involving drug interventions were excluded. A total of 15 studies were identified and assessed in this review. These studies demonstrate the possible impact of bariatric surgery on drug absorption, distribution, metabolism, excretion, and potential mechanisms. Pharmacokinetic changes exhibited in the limited pre-clinical studies highlight a need for further investigation to fully understand the impact and mechanism of bariatric surgery on drug responses.

Application of Multi-Layered Temperature-Responsive Polymer Brushes Coating on Titanium Surface to Inhibit Biofilm Associated Infection in Orthopedic Surgery

Infection associated with biomedical implants remains the main cause of failure, leading to reoperation after orthopedic surgery. Orthopedic infections are characterized by microbial biofilm formation on the implant surface, which makes it challenging to diagnose and treat. One potential method to prevent and treat such complications is to deliver a sufficient dose of antibiotics at the onset of infection. This strategy can be realized by coating the implant with thermoregulatory polymers and triggering the release of antibiotics during the acute phase of infection. We developed a multi-layered temperature-responsive polymer brush (MLTRPB) coating that can release antibiotics once the temperature reaches a lower critical solution temperature (LCST). The coating system was developed using copolymers composed of diethylene glycol methyl ether methacrylate and 2-hydroxyethyl methacrylate by alternatively fabricating monomers layer by layer on the titanium surface. LCST was set to the temperature of 38-40 °C, a local temperature that can be reached during infection. The antibiotic elution characteristics were investigated, and the antimicrobial efficacy was tested against S. aureus species (Xen29 ATCC 29 213) using one to four layers of MLTRPB. Both in vitro and in vivo assessments demonstrated preventive effects when more than four layers of the coating were applied, ensuring promising antibacterial effects of the MLTRPB coating.

Aldosterone as a Possible Contributor to Eye Diseases

Aldosterone, an effector molecule of the renin-angiotensin-aldosterone system (RAAS), has been receiving more attention in the field of ophthalmology because of its possible role in the pathogenesis of various eye diseases or abnormalities; it may even become a target for their treatment. Primary aldosteronism, a typical model of a systemic aldosterone excess, may cause vision loss due to various ocular diseases, such as retinal vein occlusion, central serous chorioretinopathy, and, possibly glaucoma. RAAS components are present in various parts and types of cells present in the eye. Investigations of the local RAAS in various animal models of diabetic macular edema, retinal vein occlusion, retinopathy of prematurity, central serous chorioretinopathy, and glaucoma have found evidence that aldosterone or mineralocorticoid receptors may exacerbate the pathology of these disorders. Further studies are needed to elucidate whether the modulation of aldosterone or mineralocorticoid receptors is an effective treatment for preventing vision loss in patients with eye diseases.

Inhibition of JAK1,2 Prevents Fibrotic Remodeling of Pulmonary Vascular Bed and Improves Outcomes in the Rat Model of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare complication of acute pulmonary embolism with poor clinical outcomes. Therapeutic approaches to prevention of fibrotic remodeling of the pulmonary vascular bed in CTEPH are limited. In this work, we tested the hypothesis that Janus kinase 1/2 (JAK1/2) inhibition with ruxolitinib might prevent and attenuate CTEPH in a rat model. CTEPH was induced by repeated embolization of the pulmonary artery with partially biodegradable 180 ± 30 μm alginate microspheres. Two weeks after the last injection of microspheres, ruxolitinib was administered orally at doses of 0.86, 2.58, and 4.28 mg/kg per day for 4 weeks. Prednisolone (1.475 mg/kg, i.m.) was used as a reference drug. Ruxolitinib in all doses as well as prednisolone reduced pulmonary vascular wall hypertrophy. Ruxolitinib at a dose of 2.58 mg/kg and prednisolone reduced vascular wall fibrosis. Prednisolone treatment resulted in decreased right ventricular systolic pressure. Pulmonary vascular resistance was lower in the prednisolone and ruxolitinib (4.28 mg/kg) groups in comparison with the placebo group. The plasma level of brain natriuretic peptide was lower in groups receiving ruxolitinib at doses of 2.58 and 4.28 mg/kg versus placebo. This study demonstrated that JAK1/2 inhibitor ruxolitinib dose-dependently reduced pulmonary vascular remodeling, thereby preventing CTEPH formation in rats.

Biomechanical, Histologic, and Micro-Computed Tomography Characterization of Partial-Width Full-Thickness Supraspinatus Tendon Injury in Rats

PURPOSE

Partial rotator cuff tears can cause shoulder pain and dysfunction and are more common than complete tears. However, few studies examine partial injuries in small animals and, therefore a robust, clinically relevant model may be lacking. This study aimed to fully characterize the established rat model of partial rotator cuff injury over time and determine if it models human partial rotator cuff tears.

METHODS

We created a full-thickness, partial-width injury at the supraspinatus tendon-bone interface bilaterally in 31 Sprague-Dawley rats. Rats were euthanized immediately, and at 2-, 3-, 4-, and 8-weeks after surgery. Fourteen intact shoulders were used as controls. Samples were assessed biomechanically, histologically, and morphologically.

RESULTS

Biomechanically, load to failure in controls and 8 weeks after injury was significantly greater than immediately and 3 weeks after injury. Load to failure at 8 weeks was comparable to control. However, the locations of failure were different between intact shoulders and partially injured samples. Bone mineral density at 8 weeks was significantly greater than that at 2 and 3 weeks. Although no animals demonstrated propagation to complete tear and the injury site remodeled histologically, the appearance at 8 weeks was not identical to that in the controls.

CONCLUSIONS

The biomechanical properties and bone quality decreased after the injury and was restored gradually over time with full restoration by 8 weeks after injury. However, the findings were not equivalent to the intact shoulder. This study demonstrated the limitations of the current model in its application to long-term outcome studies, and the need for better models that can be used to assess chronic partial rotator cuff injuries.

CLINICAL RELEVANCE

There is no small animal model that mimics human chronic partial rotator cuff tears, which limits our ability to improve care for this common condition.

Effects of Age and Lifelong Moderate-Intensity Exercise Training on Rats' Testicular Function

Aging is associated with testicular morphological and functional alterations, but the underlying molecular mechanisms and the impact of physical exercise are poorly understood. In this study, we examined the effects of age and lifelong moderate-intensity exercise on rat testis. Mature adults (35 weeks) and middle-aged (61 weeks) Wistar Unilever male rats were maintained as sedentary or subjected to a lifelong moderate-intensity treadmill training protocol. Testis weight and histology, mitochondrial biogenesis and function, and proteins involved in protein synthesis and stress response were evaluated. Our results illustrate an age-induced testicular atrophy that was associated with alterations in stress response, and mitochondrial biogenesis and function. Aging was associated with increased testicular levels of heat shock protein beta-1 (HSP27) and antioxidant enzymes. Aging was also associated with decreased mRNA abundance of the nuclear respiratory factor 1 (Nrf1), a key transcription factor for mitochondrial biogenesis, which was accompanied by decreased protein levels of the oxidative phosphorylation system (OXPHOS) complexes subunits in the testes of older animals. On the other hand, exercise did not protect against age-induced testicular atrophy and led to deleterious effects on sperm morphology. Exercise led to an even more pronounced decrease in the Nrf1 mRNA levels in testes of both age groups and was associated with decreased mRNA abundance of other mitochondrial biogenesis markers and decreased protein levels of OXPHOS complexes subunits. Lifelong moderate-intensity exercise training was also associated with an increase in testicular oxidative stress markers and possibly with reduced translation. Together, our results indicate that exercise did not protect against age-induced testicular atrophy and was not associated with beneficial changes in mitochondria and stress response, further activating mechanisms of protein synthesis inhibition.

Hybrid fibroin/polyurethane small-diameter vascular grafts: from fabrication to in vivo preliminary assessment

To address the need of alternatives to autologous vessels for small-calibre vascular applications (e.g. cardiac surgery), a hybrid semi-degradable material composed of silk fibroin and polyurethane (Silkothane®) was herein used to fabricate very small-calibre grafts (innner diameter = 1.5 mm) via electrospinning. Hybrid grafts were in vitro characterized in terms of morphology and mechanical behaviour, and compared to similar grafts of pure silk fibroin. Similarly, two native vessels from a rodent model (abdominal aorta and vena cava) were harvested and characterized. Preliminary implants were performed on Lewis rats to confirm the suitability of Silkothane® grafts for small-calibre applications, specifically as aortic insertion and femoral shunt. The manufacturing process generated pliable grafts consisting of a randomized fibrous mesh and exhibiting similar geometrical features to rat aortas. Both Silkothane® and pure silk fibroin grafts showed radial compliances in the range from 1.37 ± 0.86 to 1.88 ± 1.01 % 10-2 mmHg-1, lower than that of native vessels. The Silkothane® small-calibre devices were also implanted in rats demonstrating to be adequate for vascular applications; all the treated rats survived the surgery for 3 months after implantation, and 16 rats out of 17 (94%) still showed blood flow inside the graft at sacrifice. The obtained results lay the basis for a deeper investigation of the interaction between the Silktohane® graft and the implant site, which may deal with further analysis on the potentialities in terms of degradability and tissue formation, on longer time-points.

Dopaminergic Positron Emission Tomography Imaging in the Alpha-Synuclein Preformed Fibril Model Reveals Similarities to Early Parkinson's Disease

BACKGROUND

Positron emission tomography (PET) imaging in early Parkinson's disease (PD) subjects reveals that increased dopamine (DA) turnover and reduced dopamine transporter (DAT) density precede decreases in DA synthesis and storage. The rat α-synuclein preformed fibril (α-syn PFF) model provides a platform to investigate DA dynamics during multiple stages of α-syn inclusion-triggered nigrostriatal degeneration.

OBJECTIVES

We investigated multiple aspects of in vivo dopaminergic deficits longitudinally and similarities to human PD using translational PET imaging readouts.

METHODS

Longitudinal imaging was performed every 2 months in PFF and control rats for 7 months. [18 F]-Fluoro-3,4-dihydroxyphenyl-L-alanine (FDOPA) imaging was performed to investigate DA synthesis and storage (Kocc ) and DA turnover, estimated by its inverse, the effective distribution volume ratio (EDVR). 11 C-Methylphenidate (MP) was used to estimate DAT density (BPND ).

RESULTS

Early DA turnover increases and DAT binding decreases were observed in the ipsilateral striatum of PFF rats, progressing longitudinally. EDVR decreased 26%, 38%, and 47%, and BPND decreased 36%, 50%, and 65% at the 2-, 4-, and 6-month time points, respectively, compared to ipsilateral control striatum. In contrast, deficits in DA synthesis and storage were not observed in the ipsilateral striatum of PFF rats compared to control injections and were relatively preserved up to 6 months (Kocc decreased 20% at 6 months).

CONCLUSIONS

The relative preservation of DA synthesis and storage compared to robust progressive deficits in DAT density and increases in DA turnover in the rat α-syn PFF model display remarkable face validity to dopaminergic alterations in human PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Impact of Non-caloric Sweeteners on Male Fertility: A Systematic Review and Narrative Synthesis in Rodent Models

Understanding the factors which influence fertility is essential for developing appropriate nutritional recommendations for couples trying to conceive. Non-caloric sweeteners (NCS) are increasing in the food chain and despite being no/low calorie, several adverse metabolic consequences have been attributed to their consumption. Their effects on reproduction have been relatively under-researched, particularly in males. This review aims to systematically review the literature for evidence of the effect of NCS on male fertility in rodents, with sperm parameters (sperm quantity and quality) assessed as primary outcomes. Given the lack of information available in humans this review has been carried out using evidence from rodent models. Risk of bias assessment was carried out using the Syrcle risk of bias tool. Nine studies met the inclusion criteria. Forty-four percent showed a negative effect of NCS on male reproductive parameters compared with controls. The effects of NCS on fertility have been conflicting and selected studies have been heterogeneous in relation to study design. It is unclear if NCS has an impact on male reproductive function. There is a need for randomized controlled trials using a standardized protocol for analysis, to formulate a clear message in terms of male fertility.

Cocaine-Induced Locomotor Activation Differs Across Inbred Mouse Substrains

Cocaine use disorders (CUD) are devastating for affected individuals and impose a significant societal burden, but there are currently no FDA-approved therapies. The development of novel and effective treatments has been hindered by substantial gaps in our knowledge about the etiology of these disorders. The risk for developing a CUD is influenced by genetics, the environment and complex interactions between the two. Identifying specific genes and environmental risk factors that increase CUD risk would provide an avenue for the development of novel treatments. Rodent models of addiction-relevant behaviors have been a valuable tool for studying the genetics of behavioral responses to drugs of abuse. Traditional genetic mapping using genetically and phenotypically divergent inbred mice has been successful in identifying numerous chromosomal regions that influence addiction-relevant behaviors, but these strategies rarely result in identification of the causal gene or genetic variant. To overcome this challenge, reduced complexity crosses (RCC) between closely related inbred mouse strains have been proposed as a method for rapidly identifying and validating functional variants. The RCC approach is dependent on identifying phenotypic differences between substrains. To date, however, the study of addiction-relevant behaviors has been limited to very few sets of substrains, mostly comprising the C57BL/6 lineage. The present study expands upon the current literature to assess cocaine-induced locomotor activation in 20 inbred mouse substrains representing six inbred strain lineages (A/J, BALB/c, FVB/N, C3H/He, DBA/2 and NOD) that were either bred in-house or supplied directly by a commercial vendor. To our knowledge, we are the first to identify significant differences in cocaine-induced locomotor response in several of these inbred substrains. The identification of substrain differences allows for the initiation of RCC populations to more rapidly identify specific genetic variants associated with acute cocaine response. The observation of behavioral profiles that differ between mice generated in-house and those that are vendor-supplied also presents an opportunity to investigate the influence of environmental factors on cocaine-induced locomotor activity.

Control of Orthodontic Tooth Movement by Nitric Oxide Releasing Nanoparticles in Sprague-Dawley Rats

Orthodontic treatment commonly requires the need to prevent movement of some teeth while maximizing movement of other teeth. This study aimed to investigate the influence of locally injected nitric oxide (NO) releasing nanoparticles on orthodontic tooth movement in rats.

MATERIALS AND METHODS

Experimental tooth movement was achieved with nickel-titanium alloy springs ligated between the maxillary first molar and ipsilateral incisor. 2.2 mg/kg of silica nanoparticles containing S-nitrosothiol groups were injected into the mucosa just mesial to 1^st molar teeth immediately prior to orthodontic appliance activation. NO release from nanoparticles was measured in vitro by chemiluminescence. Tooth movement was measured using polyvinyl siloxane impressions. Bones were analyzed by microcomputed tomography. Local tissue was assessed by histomorphometry.

RESULTS

Nanoparticles released a burst of NO within the first hours at approximately 10 ppb/mg particles that diminished by 10 × to approximately 1 ppb/mg particles over the next 1-4 days, and then diminished again by tenfold from day 4 to day 7, at which point it was no longer measurable. Molar but not incisor tooth movement was inhibited over 50% by injection of the NO releasing nanoparticles. Inhibition of molar tooth movement occurred only during active NO release from nanoparticles, which lasted for approximately 1 week. Molar tooth movement returned to control levels of tooth movement after end of NO release. Alveolar and long bones were not impacted by injection of the NO releasing nanoparticles, and serum cyclic guanosine monophosphate (cGMP) levels were not increased in animals that received the NO releasing nanoparticles. Root resorption was decreased and periodontal blood vessel numbers were increased in animals with appliances that were injected with the NO releasing nanoparticles as compared to animals with appliances that did not receive injections with the nanoparticles.

CONCLUSION

Nitric oxide (NO) release from S-nitrosothiol containing nanoparticles inhibits movement of teeth adjacent to the site of nanoparticle injection for 1 week. Additional studies are needed to establish biologic mechanisms, optimize efficacy and increase longevity of this orthodontic anchorage effect.

Development of a Hypoparathyroid Male Rodent Model for Testing Delayed-Clearance PTH Molecules

CONTEXT

Parathyroid hormone (PTH) replacement is a promising approach in the management of hypoparathyroidism but long-acting analogues need to be developed. To date, animal models for testing PTH required parathyroidectomy by surgery. We have developed a nonsurgical rodent hypoparathyroid model and tested a delayed-clearance PTH molecule (DC-PTH).

OBJECTIVE

The aim of this study was to use cinacalcet to suppress calcium levels in normal rats and to reverse these effects with the administration of PTH or PTH analogues.

METHODS

Male Wistar rats were gavaged with either 30 mg/kg cinacalcet-HCl (cinacalcet) or vehicle only. Animals were then dosed with either single or repeated subcutaneous doses of PTH 1-34 or a DC-PTH at 20 nmol/kg. Control animals received vehicle only. Serum samples were analyzed for ionized calcium (iCa), phosphate, PTH, and DC-PTH. A pharmacokinetic-pharmacodynamic (PK-PD) model was built for cinacalcet, PTH 1-34, and DC-PTH using Phoenix64.

RESULTS

Cinacalcet reduced iCa levels between 2 and 24 hours, returning to baseline by 72 hours post dose with nadir at 8 hours (analysis of variance P < .001), associated with a fall in rat PTH. For phosphate there was a variable biphasic response. Single-dose PTH abrogated the cinacalcet-induced fall in iCa for up to 2 hours. DC-PTH prevented the fall in iCa from 4 hours post dose and gave a prolonged response, with iCa levels quicker to return to baseline than controls. DC-PTH has a half-life of 11.5 hours, approximately 44 times longer than human PTH 1-34. The PK-PD models defined the reproducible effect of cinacalcet on iCa and that DC-PTH had prolonged biological activity.

CONCLUSION

The administration of cinacalcet provides a robust and reproducible nonsurgical animal model of hypoparathyroidism. DC-PTH holds promise for the treatment of hypoparathyroidism in the future.

Folinic Acid Potentiates the Liver Regeneration Process after Selective Portal Vein Ligation in Rats

Simple Summary

Fewer than 30% of patients with liver metastases are eligible for major liver resection, because liver remaining after such a surgery would be insufficient to cover the patient’s needs; this is called a low percentage of future liver remnant (FLR). Folinic acid (FA) has been shown to play a crucial role in cellular synthesis, regeneration, and nucleotide and amino acid biosynthesis. The aim of this piece of research was to evaluate the effect of FA as a potential hypertrophic hepatic enhancer agent after selective portal vein ligation (PVL) to ensure adequate FLR. We have confirmed in our rodent model that FA accelerates liver regeneration after PVL and enhances recovery of liver function. These findings may allow more patients to be eligible for liver resection without jeopardizing postoperative liver function.

Abstract

Liver resection remains the gold standard for hepatic metastases. The future liver remnant (FLR) and its functional status are two key points to consider before performing major liver resections, since patients with less than 25% FLR or a Child–Pugh B or C grade are not eligible for this procedure. Folinic acid (FA) is an essential agent in cell replication processes. Herein, we analyze the effect of FA as an enhancer of liver regeneration after selective portal vein ligation (PVL). Sixty-four male WAG/RijHsd rats were randomly distributed into eight groups: a control group and seven subjected to 50% PVL, by ligation of left portal branch. The treated animals received FA (2.5 m/kg), while the rest were given saline. After 36 h, 3 days or 7 days, liver tissue and blood samples were obtained. FA slightly but significantly increased FLR percentage (FLR%) on the 7th day (91.88 ± 0.61%) compared to control or saline-treated groups (86.72 ± 2.5 vs. 87 ± 3.33%; p < 0.01). The hepatocyte nuclear area was also increased both at 36 h and 7days with FA (61.55 ± 16.09 µm², and 49.91 ± 15.38 µm²; p < 0.001). Finally, FA also improved liver function. In conclusion, FA has boosted liver regeneration assessed by FLR%, nuclear area size and restoration of liver function after PVL.

Neuroprotection by Transcranial Direct Current Stimulation in Rodent Models of Focal Ischemic Stroke: A Meta-Analysis

Infarct size is associated with stroke severity in clinical studies, so reducing it has become an important target and research hotspot in the treatment of ischemic stroke. Some preclinical studies have shown transcranial direct current stimulation (tDCS) reduced infarct size and improved neurological deficit, but others have not found beneficial effects. Besides, the optimal pattern of tDCS for ischemic stroke remains largely unknown. To shed light on the current circumstance and future research directions, the systematic review evaluated the effect of different tDCS paradigms in reducing infarct size and improving neurological deficit in rodent models of ischemic stroke and assessed the methodological quality of current literature. We searched the MEDLINE (via PubMed), EMBASE, Web of Science, and Scopus from their inception to August 18, 2021, to identify studies evaluating the effects of tDCS in rodent models of ischemic stroke. Eight studies were included, of which seven studies were included in the meta-analysis. The results showed cathodal tDCS, rather than anodal tDCS, reduced infarct size mainly measured by tetrazolium chloride and magnetic resonance imaging (standardized mean difference: -1.13; 95% CI: -1.72, -0.53; p = 0.0002) and improved neurological deficit assessed by a modified neurological severity score (standardized mean difference: -2.10; 95% CI: -3.78, -0.42; p = 0.01) in an early stage of focal ischemic stroke in rodent models. Subgroup analyses showed effects of cathodal tDCS on infarct size were not varied by ischemia duration (ischemia for 1, 1.5, and 2 h or permanent ischemia) and anesthesia (involving isoflurane and ketamine). The overall quality of studies included was low, thus the results must be interpreted cautiously. Published studies suggest that cathodal tDCS may be a promising avenue to explore for augmenting rehabilitation from focal ischemic stroke. Considering the methodological limitations, it is unreliable to blindly extrapolate the animal data to the clinical practice. Future research is needed to investigate the mechanism of tDCS in a randomized and blinded fashion in clinically relevant stroke models, such as elderly animals, female animals, and animals with comorbidities, to find an optimal treatment protocol.

The Cholecystokinin Type 2 Receptor, a Pharmacological Target for Pain Management

Over the past decades, accumulating evidence has demonstrated a pivotal role of cholecystokinin type 2 receptor (CCK2R) in pain modulation. The established role of CCK2R activation in directly facilitating nociception has led to the development of several CCK2R antagonists, which have been shown to successfully alleviate pain in several rodent models of pain. However, the outcomes of clinical trials are more modest since they have not demonstrated the expected biological effect obtained in animals. Such discordances of results between preclinical and clinical studies suggest reconsidering our knowledge about the molecular basis of the pharmacology and functioning of CCK2R. This review focuses on the cellular localization of CCK2R specifically in the sensory nervous system and discusses in further detail the molecular mechanisms and signal transduction pathways involved in controlling pain perception. We then provide a comprehensive overview of the most successful compounds targeting CCK2R and report recent advances in pharmacological strategies used to achieve CCK2R modulation. We purposely distinguish between CCK2R benefits obtained in preclinical models and outcomes in clinical trials with different pain etiologies. Lastly, we emphasize the biological and clinical relevance of CCK2R as a promising target for the development of new treatments for pain management.

An examination of two different approaches for the study of femoral neck fracture: Towards a more relevant rodent model

Femoral neck fractures are a massive personal and health programme burden. Methods to study femoral neck strength, across its combined trabecular and cortical components are therefore essential. Rodent ovariectomy-induced osteoporosis models are commonly coupled with ex vivo 3-/4-point bending methods to measure changes in femoral cortical diaphysis. The loading direction used to assess these properties are often non-physiologic and, moreover, these ovariectomy models are linked to marked weight gain that can influence the biomechanical properties. Herein, we explore whether more physiological axial ex vivo loading protocols applied to femoral neck samples of ovariectomised (OVX) rodents provide anatomically-relevant models for the assessment of strength. We examine the use of mouse and rat femurs, loaded in constrained and unconstrained configuration, respectively, and explore whether weight-correction increases their utility. Accordingly, the mid-shaft of the proximal half of femurs from OVX and sham-operated (Sham) mice was methacrylate-anchored and the head loaded parallel to the diaphysis (constrained). Alternatively, femurs from OVX and Sham rats were isolated intact and axially-loaded through hip and knee joint articular surfaces (unconstrained). Yield displacement, stiffness, maximum load and resilience were measured and fracture pattern classified; effects of body weight-correction via a linear regression method or simple division were assessed. Our data reveal significant deficiencies in biomechanical properties in OVX mouse femurs loaded in constrained configuration, only after weight-correction by linear regression. In addition, evaluation of rat femur biomechanics in unconstrained loading demonstrated greater variation and that weight-correction by simple division improved scope to reveal significant OVX impact. We conclude that greater femoral neck fracture susceptibility can indeed be measured in OVX rodents as long as multiple biomechanical parameters are reported, care is taken in choosing the method for assessing load-bearing strength and weight-correction applied. These studies advance the establishment of more relevant rodent models for the study of femoral neck fracture.

In utero Exposure to Valproic-Acid Alters Circadian Organisation and Clock-Gene Expression: Implications for Autism Spectrum Disorders

Autism Spectrum Disorder (ASD) is a pervasive neurodevelopmental disorder characterised by restrictive patterns of behaviour and alterations in social interaction and communication. Up to 80% of children with ASD exhibit sleep-wake cycle disturbances, emphasising the pressing need for novel approaches in the treatment of ASD-associated comorbidities. While sleep disturbances have been identified in ASD individuals, little has been done to assess the contribution of the circadian system to these findings. The objective of this study is to characterise circadian behaviour and clock-gene expression in a valproic acid (VPA)-induced animal model of autism to highlight perturbations potentially contributing to these disturbances. Male and female VPA-exposed offspring underwent circadian challenges, including baseline light-dark cycles, constant dark/light and light pulse protocols. Baseline analysis showed that VPA-exposed males, but not females, had a greater distribution of wheel-running behaviour across light-dark phases and a later activity offset (p < 0.0001), while controls showed greater activity confinement to the dark phase (p = 0.0256). Constant light analysis indicated an attenuated masking response and an increase in the number of days to reach arrhythmicity (p < 0.0001). A 1-h light pulse (150 lux) at CT 15 after 6 days of constant dark showed that both sexes exposed to VPA exhibited a lesser phase-shift when compared to controls (p = 0.0043). Immunohistochemical and western-blot assays reveal no alterations in retinal organisation or function. However, immunohistochemical assay of the SCN revealed altered expression of BMAL1 expression in VPA-exposed males (p = 0.0016), and in females (p = 0.0053). These findings suggest alterations within the core clockwork of the SCN and reduced photic-entrainment capacity, independent of retinal dysfunction. The results of this study shed light on the nature of circadian dysregulation in VPA-exposed animals and highlights the urgent need for novel perspectives in the treatment of ASD-associated comorbidities.

Physiological importance of NGLY1, as revealed by rodent model analyses

Cytosolic peptide:N-glycanase (NGLY1) is an enzyme that cleaves N-glycans from glycoproteins that has been retrotranslocated from the endoplasmic reticulum (ER) lumen into the cytosol. It is known that NGLY1 is involved in the degradation of cytosolic glycans (non-lysosomal glycan degradation) as well as ER-associated degradation (ERAD), a quality control system for newly synthesized glycoproteins. The discovery of NGLY1 deficiency, which is caused by mutations in the human NGLY1 gene and results in multisystemic symptoms, has attracted interest in the physiological functions of NGLY1 in mammals. Studies using various animal models led to the identification of possible factors that contribute to the pathogenesis of NGLY1 deficiency. In this review, we summarize phenotypic consequences that have been reported for various Ngly1-deficient rodent models, and discuss future perspectives to provide more insights into the physiological functions of NGLY1.

Protein Targets of Acetaminophen Covalent Binding in Rat and Mouse Liver Studied by LC-MS/MS

Acetaminophen (APAP) is a mild analgesic and antipyretic used commonly worldwide. Although considered a safe and effective over-the-counter medication, it is also the leading cause of drug-induced acute liver failure. Its hepatotoxicity has been linked to the covalent binding of its reactive metabolite, N-acetyl p-benzoquinone imine (NAPQI), to proteins. The aim of this study was to identify APAP-protein targets in both rat and mouse liver, and to compare the results from both species, using bottom-up proteomics with data-dependent high resolution mass spectrometry and targeted multiple reaction monitoring (MRM) experiments. Livers from rats and mice, treated with APAP, were homogenized and digested by trypsin. Digests were then fractionated by mixed-mode solid-phase extraction prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS). Targeted LC-MRM assays were optimized based on high-resolution MS/MS data from information-dependent acquisition (IDA) using control liver homogenates treated with a custom alkylating reagent yielding an isomeric modification to APAP on cysteine residues, to build a modified peptide database. A list of putative in vivo targets of APAP were screened from data-dependent high-resolution MS/MS analyses of liver digests, previous in vitro studies, as well as selected proteins from the target protein database (TPDB), an online resource compiling previous reports of APAP targets. Multiple protein targets in each species were found, while confirming modification sites. Several proteins were modified in both species, including ATP-citrate synthase, betaine-homocysteine S-methyltransferase 1, cytochrome P450 2C6/29, mitochondrial glutamine amidotransferase-like protein/ES1 protein homolog, glutamine synthetase, microsomal glutathione S-transferase 1, mitochondrial-processing peptidase, methanethiol oxidase, protein/nucleic acid deglycase DJ-1, triosephosphate isomerase and thioredoxin. The targeted method afforded better reproducibility for analysing these low-abundant modified peptides in highly complex samples compared to traditional data-dependent experiments.

Macronutrient-induced modulation of periodontitis in rodents-a systematic review

CONTEXT

Consumption of dietary macronutrients is associated with the progression of a wide range of inflammatory diseases, either by direct modulation of host immune response or via microbiome. This includes periodontitis, a disease affecting tooth-supporting tissues.

OBJECTIVE

The aim of this work was to systematically review studies focusing on the effect of macronutrient (ie, carbohydrate, protein, fat) intake on periodontitis in rodents.

DATA SOURCES

Electronic searches were performed in February 2021 using the PubMed and Web of Science databases. Out of 883 articles reviewed, 23 studies were selected for additional analysis.

DATA EXTRACTION

Investigators extracted relevant data, including author names; the year of publication; article title; macronutrient composition; number and species of animals and their age at the start of the experiment; intervention period; method of periodontitis induction; and primary and secondary periodontitis outcomes. Quality assessment was done using the risk-of-bias tool for animal studies. After completing the data extraction, descriptive statistical information was obtained.

DATA ANALYSIS

High intakes of dietary cholesterol, saturated fatty acids, and processed carbohydrates such as sucrose, and protein-deficient diets were positively associated with periodontitis in rodents. This included greater amounts of alveolar bone loss, more lesions on periodontal tissues, and dental plaque accumulation. In contrast, high doses of milk basic protein in diets and diets with a high ratio of ω-3 to ω-6 fatty acids were negatively associated with periodontitis in rodents.

CONCLUSION

This work highlights the fact that, despite the large body of evidence linking macronutrients with inflammation and ageing, overall there is little information on how dietary nutrients affect periodontitis in animal models. In addition, there is inconsistency in data due to differences in methodology, outcome measurement, and dietary formulation. More studies are needed to examine the effects of different dietary macronutrients on periodontitis and investigate the underlying biological mechanisms.

Cellular and Molecular Dynamics during Early Oral Osseointegration: A Comprehensive Characterization in the Lewis Rat

OBJECTIVE

There is a need to improve the predictability of osseointegration in implant dentistry. Current literature uses a variety of in vivo titanium (Ti) implantation models to investigate failure modes and test new materials and surfaces. However, these models produce a variety of results, making comparison across studies difficult. The purpose of this study is to validate an oral osseointegration in the Lewis rat to provide a reproducible baseline to track the inflammatory response and healing of Ti implants.

METHODS

Ti screws (0.76 mm Ø × 2 mm length) were implanted into the maxillary diastema of 52 adult male Lewis rats. Peri-implant tissues were evaluated 2, 7, 14, and 30 days after implantation (n = 13). Seven of the 13 samples underwent microtomographic analysis, histology, histomorphometry, and immunohistochemistry to track healing parameters. The remaining six samples underwent quantitative polymerase chain reaction (qPCR) to evaluate gene expression of inflammation and bone remodeling markers over time.

RESULTS

This model achieved a 78.5% success rate. Successful implants had a bone to implant contact (BIC)% of 68.86 ± 3.15 at 30 days on average. Histologically, healing was similar to other rodent models: hematoma and acute inflammation at 2 days, initial bone formation at 7, advanced bone formation and remodeling at 14, and bone maturation at 30. qPCR indicated the highest expression of bone remodeling and inflammatory markers 2-7 days, before slowly declining to nonsurgery control levels at 14-30 days.

CONCLUSION

This model combines cost-effectiveness and simplicity of a rodent model, while maximizing BIC, making it an excellent candidate for evaluation of new surfaces.

Relationship between Lung Carcinogenesis and Chronic Inflammation in Rodents

Simple Summary

Lung cancer is the most common cause of cancer-related deaths worldwide. There are various risk factors for lung cancer, including tobacco smoking, inhalation of dust particles, chronic inflammation, and genetic factors. Chronic inflammation has been considered a key factor that promotes tumor progression via production of cytokines, chemokines, cytotoxic mediators, and reactive oxygen species by inflammatory cells. Here, we review rodent models of lung tumor induced by tobacco, tobacco-related products, and pro-inflammatory materials as well as genetic modifications, and discuss the relationship between chronic inflammation and lung tumor. Through this review, we hope to clarify the effects of chronic inflammation on lung carcinogenesis and help develop new treatments for lung cancer.

Abstract

Lung cancer remains the leading cause of cancer-related deaths, with an estimated 1.76 million deaths reported in 2018. Numerous studies have focused on the prevention and treatment of lung cancer using rodent models. Various chemicals, including tobacco-derived agents induce lung cancer and pre-cancerous lesions in rodents. In recent years, transgenic engineered rodents, in particular, those generated with a focus on the well-known gene mutations in human lung cancer (KRAS, EGFR, and p53 mutations) have been widely studied. Animal studies have revealed that chronic inflammation significantly enhances lung carcinogenesis, and inhibition of inflammation suppresses cancer progression. Moreover, the reduction in tumor size by suppression of inflammation in animal experiments suggests that chronic inflammation influences the promotion of tumorigenesis. Here, we review rodent lung tumor models induced by various chemical carcinogens, including tobacco-related carcinogens, and transgenics, and discuss the roles of chronic inflammation in lung carcinogenesis.

The IntelliCage System: A Review of Its Utility as a Novel Behavioral Platform for a Rodent Model of Substance Use Disorder

The use of animal models for substance use disorder (SUD) has made an important contribution in the investigation of the behavioral and molecular mechanisms underlying substance abuse and addiction. Here, we review a novel and comprehensive behavioral platform to characterize addiction-like traits in rodents using a fully automated learning system, the IntelliCage. This system simultaneously captures the basic behavioral navigation, reward preference, and aversion, as well as the multi-dimensional complex behaviors and cognitive functions of group-housed rodents. It can reliably capture and track locomotor and cognitive pattern alterations associated with the development of substance addiction. Thus, the IntelliCage learning system offers a potentially efficient, flexible, and sensitive tool for the high-throughput screening of the rodent SUD model.

The silent information regulator 1 pathway attenuates ROS-induced oxidative stress in Alzheimer's disease

We show that down-regulation of circular ribonucleic acid 0001588 with small interfering-circular ribonucleic acid 0001588 mimics promoted caspase-3 and caspase-9 activity levels, increased lactate dehydrogenase activity levels, and reduced cell growth of in vitro model. Circular ribonucleic acid 0001588 plasmids increased circular ribonucleic acid 0001588 expressions and promoted cell growth and reduced activity levels of lactate dehydrogenase, caspase-3, and caspase-9 activity levels in vitro model of Alzheimer's disease. Then, circular ribonucleic acid 0001588 down-regulation also promoted reactive oxygen species production and oxidative stress (malonaldehyde), and reduced superoxide dismutase, glutathione, and glutathione peroxidase levels by suppressing of silent information regulator 1/nuclear factor erythroid 2-related factor 2/heme oxygenase-1 in vitro. However, over-expression of circular ribonucleic acid 0001588 reduced reactive oxygen species production and malonaldehyde levels and increased superoxide dismutase, glutathione, and levels via activation signal pathway of silent information regulator 1/nuclear factor erythroid 2-related factor 2/heme oxygenase-1 signaling pathway by miR-211-5p up-regulation in vitro. Over-expression of miR-211-5p attenuated the role of circular ribonucleic acid 0001588 on Alzheimer's disease-induced oxidative stress. Also, activation of the silent information regulator 1 pathway attenuated the antioxidative effects of circular ribonucleic acid 0001588 down-regulation on oxidative stress by activating silent information regulator 1/nuclear factor erythroid 2-related factor 2/heme oxygenase-1 in vitro. In conclusion, our findings indicated that circular ribonucleic acid 0001588 induced the silent information regulator 1/nuclear factor erythroid 2-related factor 2-dependent heme oxygenase-1 pathway to prevent oxidative stress by miR-211-5p in the rat model or in vitro model of a sporadic type of Alzheimer's disease. Therefore, the expression of the circular ribonucleic acid 0001588 gene was inhibited in rodent Alzheimer's disease model.

Advances in Rodent Models for Breast Cancer Formation, Progression, and Therapeutic Testing

Breast cancer is a highly complicated disease. Advancement in the treatment and prevention of breast cancer lies in elucidation of the mechanism of carcinogenesis and progression. Rodent models of breast cancer have developed into premier tools for investigating the mechanisms and genetic pathways in breast cancer progression and metastasis and for developing and evaluating clinical therapeutics. Every rodent model has advantages and disadvantages, and the selection of appropriate rodent models with which to investigate breast cancer is a key decision in research. Design of a suitable rodent model for a specific research purpose is based on the integration of the advantages and disadvantages of different models. Our purpose in writing this review is to elaborate on various rodent models for breast cancer formation, progression, and therapeutic testing.

Regulation of Intestinal Inflammation by Dietary Fats

With the epidemic of human obesity, dietary fats have increasingly become a focal point of biomedical research. Epidemiological studies indicate that high-fat diets (HFDs), especially those rich in long-chain saturated fatty acids (e.g., Western Diet, National Health Examination survey; NHANES 'What We Eat in America' report) have multi-organ pro-inflammatory effects. Experimental studies have confirmed some of these disease associations, and have begun to elaborate mechanisms of disease induction. However, many of the observed effects from epidemiological studies appear to be an over-simplification of the mechanistic complexity that depends on dynamic interactions between the host, the particular fatty acid, and the rather personalized genetics and variability of the gut microbiota. Of interest, experimental studies have shown that certain saturated fats (e.g., lauric and myristic fatty acid-rich coconut oil) could exert the opposite effect; that is, desirable anti-inflammatory and protective mechanisms promoting gut health by unanticipated pathways. Owing to the experimental advantages of laboratory animals for the study of mechanisms under well-controlled dietary settings, we focus this review on the current understanding of how dietary fatty acids impact intestinal biology. We center this discussion on studies from mice and rats, with validation in cell culture systems or human studies. We provide a scoping overview of the most studied diseases mechanisms associated with the induction or prevention of Inflammatory Bowel Disease in rodent models relevant to Crohn's Disease and Ulcerative Colitis after feeding either high-fat diet (HFD) or feed containing specific fatty acid or other target dietary molecule. Finally, we provide a general outlook on areas that have been largely or scarcely studied, and assess the effects of HFDs on acute and chronic forms of intestinal inflammation.

Numerical Study on Electrode Design for Rodent Deep Brain Stimulation With Implantations Cranial to Targeted Nuclei

The globus pallidus internus and the subthalamic nucleus are common targets for deep brain stimulation to alleviate symptoms of Parkinson's disease and dystonia. In the rodent models, however, their direct targeting is hindered by the relatively large dimensions of applied electrodes. To reduce the neurological damage, the electrodes are usually implanted cranial to the nuclei, thus exposing the non-targeted brain regions to large electric fields and, in turn, possible undesired stimulation effects. In this numerical study, we analyze the spread of the fields for the conventional electrodes and several modifications. As a result, we present a relatively simple electrode design that allows an efficient focalization of the stimulating field in the inferiorly located nuclei.

Rodent Models to Analyze the Glioma Microenvironment

Animal models are still indispensable for understanding the basic principles of glioma development and invasion. Preclinical approaches aim to analyze the treatment efficacy of new drugs before translation into clinical trials is possible. Various animal disease models are available, but not every approach is useful for addressing specific questions. In recent years, it has become increasingly evident that the tumor microenvironment plays a key role in the nature of glioma. In addition to providing an overview, this review evaluates available rodent models in terms of usability for research on the glioma microenvironment.