Process In Mouse Model Research Articles

Nanoplastics exposure-induced mitochondrial dysfunction contributes to disrupted stem cell differentiation in human cerebral organoids

Nanoplastics are ubiquitous in our daily lives, raising concerns about their potential impact on the human brain. Many studies reported that nanoplastics permeate the blood-brain barrier and influence cellular processes in mouse models. However, the neurotoxic effects of ingesting nanoplastics on human brain remain poorly understood. Here, we treated cerebral organoids with polystyrene nanoplastics to model the effects of nanoplastic exposure on human brain. Importantly, we found that mitochondria might be the significant organelles affected by polystyrene nanoplastics using immunostaing and RNA-seq analysis. Subsequently, we observed the increased cell death and decreased cell differentiation in our cerebral organoids. In conclusion, our findings shed insights on the mechanisms underlying the toxicity of nanoplastics on human brain organoids, providing an evaluation system in detection potential environmental toxicity on human brain.

Primer on FGF3

Though initially discovered as a proto-oncogene in virally induced mouse mammary tumors, FGF3 is primarily active in prenatal stages, where it is found at various sites at specific times. FGF3 is crucial during development, as its roles include tail formation, inner ear development and hindbrain induction and patterning. FGF3 expression and function are highly conserved in vertebrates, while it also interacts with other FGFs in various developmental processes. Intriguingly, while it is classified as a classical paracrine signaling factor, murine FGF3 was uniquely found to also act in an intracrine manner, depending on alternative translation initiation sites. Corresponding with its conserved role in inner ear morphogenesis, mutations in FGF3 in humans are associated with LAMM syndrome, a disorder that include hearing loss and inner ear malformations. While recent studies indicate of some FGF3 presence in post-natal stages, emerging evidences of its upregulation in various human tumors and cariogenic processes in mouse models, highlights the importance of its close regulation in adult tissues. Altogether, the broad and dynamic expression pattern and regulation of FGF3 in embryonic and adult tissues together with its link to congenital malformations and cancer, calls for further discoveries of its diverse roles in health and disease.

Slow-wave sleep affects synucleinopathy and regulates proteostatic processes in mouse models of Parkinson's disease.

Slow-wave sleep (SWS) modulation in rodent models of Alzheimer’s disease alters extracellular amyloid burden. In Parkinson’s disease (PD), SWS appears to be closely linked with disease symptoms and progression. PD is characterized by damaging intracellular α-synuclein (αSyn) deposition that propagates extracellularly, contributing to disease spread. Intracellular αSyn is sensitive to degradation, whereas extracellular αSyn may be eliminated by glymphatic clearance, a process increased during SWS. Here, we explored whether long-term slow-wave modulation in murine models of PD presenting αSyn aggregation alters pathological protein burden and, thus, might constitute a valuable therapeutic target. Sleep-modulating treatments showed that enhancing slow waves in both VMAT2-deficient and A53T mouse models of PD reduced pathological αSyn accumulation compared to control animals. Nonpharmacological sleep deprivation had the opposite effect in VMAT2-deficient mice, severely increasing the pathological burden. We also found that SWS enhancement was associated with increased recruitment of aquaporin-4 to perivascular sites, suggesting a possible increase of glymphatic function. Furthermore, mass spectrometry data revealed differential and specific up-regulation of functional protein clusters linked to proteostasis upon slow wave–enhancing interventions. Overall, the beneficial effect of SWS enhancement on neuropathological outcome in murine synucleinopathy models mirrors findings in models of Alzheimer. Modulating SWS might constitute an effective strategy for modulating PD pathology in patients.

Resolvin D1 attenuates the inflammatory process in mouse model of LPS-induced keratitis.

The aim of this study was to investigate the effects of the lipid mediator Resolvin D1 in experimental keratitis. C57BL/6J mice were injected with lipopolysaccharide (2 µg/eye), and after 24 hours, the corneal damage was assessed. Clinical score was quantified, and corneal inflammatory biomarkers were detected by immunohistochemistry. A robust accumulation of sub‐epithelial macrophages and polymorphonuclear leucocytes, chemokine (C‐X‐C motif) ligand 1 (also known as keratinocyte‐derived chemokine), interleukin‐10 and promoters of apoptosis was also observed in lipopolysaccharide‐treated mice. Formyl peptide receptor 2 corneal expression was also assessed. The corneal stroma treated with lipopolysaccharide was characterized by presence of macrophages of M1‐like subtype and immature fibroblastic cells, marked with Ki67, not fully differentiated in fibroblasts. Indeed, the staining of the cornea with anti‐vimentin antibodies, a marker of differentiated myofibroblasts, was very faint. Resolvin D1 attenuated all the inflammatory parameters assessed in the present study, except for IL‐10. In conclusion, the data presented here seem to be consistent with the hypothesis that Resolvin D1 protected the cornea from the lipopolysaccharide‐induced keratitis by acting on several inflammatory components of this damage, pivoted by Formyl peptide receptor 2 (FPR2) activation and macrophages‐leucocytes activity.

Tissue Clearing and Expansion Methods for Imaging Brain Pathology in Neurodegeneration: From Circuits to Synapses and Beyond.

Studying the structural alterations occurring during diseases of the nervous system requires imaging heterogeneous cell populations at the circuit, cellular and subcellular levels. Recent advancements in brain tissue clearing and expansion methods allow unprecedented detailed imaging of the nervous system through its entire scale, from circuits to synapses, including neurovascular and brain lymphatics elements. Here, we review the state-of-the-art of brain tissue clearing and expansion methods, mentioning their main advantages and limitations, and suggest their parallel implementation for circuits-to-synapses brain imaging using conventional (diffraction-limited) light microscopy -such as confocal, two-photon and light-sheet microscopy- to interrogate the cellular and molecular basis of neurodegenerative diseases. We discuss recent studies in which clearing and expansion methods have been successfully applied to study neuropathological processes in mouse models and postmortem human brain tissue. Volumetric imaging of cleared intact mouse brains and large human brain samples has allowed unbiased assessment of neuropathological hallmarks. In contrast, nanoscale imaging of expanded cells and brain tissue has been used to study the effect of protein aggregates on specific subcellular structures. Therefore, these approaches can be readily applied to study a wide range of brain processes and pathological mechanisms with cellular and subcellular resolution in a time- and cost-efficient manner. We consider that a broader implementation of these technologies is necessary to reveal the full landscape of cellular and molecular mechanisms underlying neurodegenerative diseases.

Assessment of operant learning and memory in mice born through ICSI.

Are there differences in operant learning and memory between mice born through ICSI and naturally conceived control (CTL) mice? ICSI females exhibited deficits in the acquisition reward learning relative to CTL females, and ICSI males exhibited deficiencies in discrimination learning and memory relative to CTL males. Some human outcome studies have suggested that ICSI might be associated with an increased risk of certain cognitive disorders, but only one of two behavioral studies with ICSI mouse models have reported differences between ICSI and CTL females. No studies to date have investigated associative learning in ICSI mice. Groups of 36 ICSI mice (18 male, 18 female) and 37 CTL mice (19 male, 18 female) aged 3-6 months were compared in a series of operant learning procedures that assessed acquisition of a new behavior, discrimination learning and memory. In total, 16 ICSI mice (9 male, 7 female) and 17 CTL mice (10 male, 7 female) received follow-up discrimination learning and memory assessments at 12 months of age (6 months after the end of initial training) to evaluate retention and reacquisition of learned performances. Mice received daily operant learning sessions in experimental chambers in which all stimulus events and the recording of responses were automated. Food rewards were delivered for responding under different conditions of reinforcement, which varied by procedure. Subjects received a successive series of sessions of nose poke acquisition training, discrimination training and the delayed-non-matching-to-position memory procedure. Mixed repeated measures ANOVAs in which the between-subjects factor was group (ICSI vs CTL) and the within-subjects factor was repeated exposures to learning procedures (i.e. sessions) were used to analyze data. In comparisons between all mice (i.e. males and females combined), CTL mice exhibited superior performance relative to ICSI in response acquisition (P = 0.03), discrimination (P = 0.001) and memory (P = 0.007). Sex-specific comparisons between the groups yielded evidence of sexual dimorphism. ICSI females exhibited a deficit in acquisition learning relative to CTL females (P < 0.001), but there was not a significant difference between CTL and ICSI males. In the discrimination and memory tasks, ICSI males exhibited deficits relative to CTL males (P = 0.002 and P = 0.02, respectively) but the differences between females in these tasks were not significant. There was no difference in discrimination or memory retention/re-acquisition assessments conducted with mice at 12 months of age. ICSI males and females weighed significantly more than CTL counterparts at all points during the experiment. N/A. The study was not blinded. All learning assessments utilized food reward; other assessments of operant, Pavlovian and nonassociative learning are needed to fully characterize learning in ICSI mice and speculate regarding the implications for cognitive function in humans conceived via ICSI. Studying learning and memory processes in mouse models have the potential to shed light on ICSI outcomes at the level of cognitive function. Future research should use multiple learning paradigms, assess both males and females, and investigate the effects of variables related to the ICSI procedure. Studying cognitive function in ICSI is an interdisciplinary endeavor and requires co-ordination between researchers at the genetic and psychological levels of analysis. This work was supported, in part, by grants from the NIH (P30GM110767, HD071736 and HD085506 to W.Y.), the Templeton Foundation (61174 to W.Y.) and a New Scholarly Endeavor Grant from the University of Nevada, Reno Office of Research and Innovation (to M.L., Y.W., H.Z., L.H. and W.Y.). The authors declare no competing interests.

Mouse models of deep vein thrombosis.

The pathogenesis of venous thromboembolism (VTE) is still not completely understood. Experimental animals in which human deep vein thrombosis can be modeled are useful tools to investigate the pathogenesis of VTE. Besides the availability of transgenic and genetically modified mice, the use of high frequency ultrasound and intravital microscopy plays an important role in identifying thrombotic processes in mouse models. In this article, an overview about the application of various new technologies and existing mouse models is provided, and the impact of venous side branches on deep vein thrombosis in the mouse model is discussed.

Introduction of Zinc-salt Fixation for Effective Detection of Immune Cell-related Markers by Immunohistochemistry.

Tissue localization of immune cells is critical to the study of disease processes in mouse models of human diseases. However, immunohistochemistry (IHC) for immune cell phenotyping in mouse tissue sections presents specific technical challenges. For example, CD4 and CD8 have been difficult to detect using IHC on formalin-fixed and paraffin-embedded mouse tissue, prompting alternative methods. We investigated the use of formalin-free zinc-salt fixation (ZN) and optimized IHC protocols for detecting a panel of immune cell-related markers (CD3, CD4, CD8, Foxp3, B220, F4/80, CD68, and major histocompatibility complex [MHC] class-I, MHC class-II, and Gr-1). The IHC results for these markers were compared on mouse spleen tissue treated with neutral buffered formalin (NBF) or ZN with or ZN without antigen retrieval (AR). Whereas CD4 and CD8 were not detected in NBF-treated tissue, all markers were detected in ZN-treated tissue without AR. Thus, the use of ZN treatment for IHC staining can be a good tool for studying immunoreactive lesions in tissues.

Innate lymphoid cells in the initiation, regulation and resolution of inflammation.

A previously unappreciated cell type of the innate immune system, termed innate lymphoid cells (ILCs), has been characterized in mice and humans and found to influence the induction, regulation and resolution of inflammation. ILCs have an important role in these processes in mouse models of infection, inflammation and tissue repair. Further, disease-association studies in defined patient populations have identified significant alterations in ILC responses, suggesting a potential role for these cell populations in human health and disease. In this review we discuss the emerging family of ILCs, the role of ILCs in inflammation, and how current or novel therapeutic strategies could be used to selectively modulate ILC responses and limit chronic inflammatory diseases.

Prolonged diet induced obesity has minimal effects towards brain pathology in mouse model of cerebral amyloid angiopathy: Implications for studying obesity–brain interactions in mice

Cerebral amyloid angiopathy (CAA) occurs in nearly every individual with Alzheimer's disease (AD) and Down's syndrome, and is the second largest cause of intracerebral hemorrhage. Mouse models of CAA have demonstrated evidence for increased gliosis contributing to CAA pathology. Nearly two thirds of Americans are overweight or obese, with little known about the effects of obesity on the brain, although increasingly the vasculature appears to be a principle target of obesity effects on the brain. In the current study we describe for the first time whether diet induced obesity (DIO) modulates glial reactivity, amyloid levels, and inflammatory signaling in a mouse model of CAA. In these studies we identify surprisingly that DIO does not significantly increase Aβ levels, astrocyte (GFAP) or microglial (IBA-1) gliosis in the CAA mice. However, within the hippocampal gyri a localized increase in reactive microglia were increased in the CA1 and stratum oriens relative to CAA mice on a control diet. DIO was observed to selectively increase IL-6 in CAA mice, with IL-1β and TNF-α not increased in CAA mice in response to DIO. Taken together, these data show that prolonged DIO has only modest effects towards Aβ in a mouse model of CAA, but appears to elevate some localized microglial reactivity within the hippocampal gyri and selective markers of inflammatory signaling. These data are consistent with the majority of the existing literature in other models of Aβ pathology, which surprisingly show a mixed profile of DIO effects towards pathological processes in mouse models of neurodegenerative disease. The importance for considering the potential impact of ceiling effects in pathology within mouse models of Aβ pathogenesis, and the current experimental limitations for DIO in mice to fully replicate metabolic dysfunction present in human obesity, are discussed. This article is part of a Special Issue entitled: Animal Models of Disease.