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How many RBPMS+ retinal ganglion cells (RGCs) does a standard C57BL/6 laboratory mouse have on average and is this number substrain- or sex-dependent? Do RGCs of (European) C57BL/6J and -N mice show a different intrinsic vulnerability upon glaucomatous injury? Global RGC numbers and densities of common laboratory mice were previously determined via axon counts, retrograde tracing or BRN3A immunohistochemistry. Here, we report the global RGC number and density by exploiting the freely available tool RGCode to automatically count RGC numbers and densities on entire retinal wholemounts immunostained for the pan-RGC marker RBPMS. The intrinsic vulnerability of RGCs from different substrains to glaucomatous injury was evaluated upon introduction of the microbead occlusion model, followed by RBPMS counts, retrograde tracing and electroretinography five weeks post-injury. We demonstrate that the global RGC number and density varies between substrains, yet is not sex-dependent. C57BL/6J mice have on average 46K ± 2K RBPMS+ RGCs per retina, representing a global RGC density of 3268 ± 177 RGCs/mm2. C57BL/6N mice, on the other hand, have on average less RBPMS+ RGCs (41K ± 3K RGCs) and a lower density (3018 ± 189 RGCs/mm2). The vulnerability of the RGC population of the two C57BL/6 substrains to glaucomatous injury did, however, not differ in any of the interrogated parameters. [ABSTRACT FROM AUTHOR]

Background: Matrix metalloproteinases (MMPs), a family of Zn(2+)-dependent endoproteases, have been shown to act as fine regulators of both health and disease. Limited research revealed that they are essential to maintaining ocular physiology and inordinate MMP activities have been linked to several neurodegenerative disorders of the retina, including age-related macular degeneration, proliferative diabetic retinopathy and glaucomatous optic neuropathies (GONs). Nevertheless, a clear definition of their pathology-exacerbating and/or -resolving actions is lacking, especially in the context of GONs, as most studies thus far merely focused on expression profiling in human patients. Therefore, in an initial step towards an improved understanding of MMP functions in the retina, we studied the spatial expression pattern of MMP-2, -3, -9 and MT1-MMP in the healthy mouse retina.Methods: The spatial expression pattern of MMP-2, -3, -9 and MT1-MMP was studied in the healthy mouse retina via immunohistochemical stainings, and immunoreactivity profiles were compared to existing literature. Moreover, we considered sensitivity and specificity issues with commercially available MMP antibodies via Western blot.Results: Basal expression of MMP-2,-3, -9 and MT1-MMP was found in the retina of healthy, adult mice. MMP-2 expression was seen in Müller glia, predominantly in their end feet, which is in line with available literature. MMP-3 expression was described for the first time in the retina, and was observed in vesicle-like structures along the radial fibers of Müller glia. MMP-9 expression, about which still discords exists, was seen in microglia and in a sparse subset of (apoptosing) RGCs. MT1-MMP localization was for the first time studied in adult mice and was found in RGC axons and Müller glia, mimicking the MT1-MMP expression pattern seen in rabbits and neonatal mice. Moreover, one antibody was selected for each MMP, based on its staining pattern in Western blot.Conclusions: The present MMP immunoreactivity profiles in the mouse retina and validation of MMP antibodies, can be instrumental to study MMP expression in mouse models of ocular pathologies and to compare these expression profiles to observations from clinical studies, which would be a first step in the disentanglement of the exact role MMPs in ocular/retinal diseases. [ABSTRACT FROM AUTHOR]

Matrix metalloproteinases (MMPs) have been designated as both friend and foe in the central nervous system (CNS): while being involved in many neurodegenerative and neuroinflammatory diseases, their actions appear to be indispensable to a healthy CNS. Pathological conditions in the CNS are therefore often related to imbalanced MMP activities and disturbances of the complex MMP-dependent protease network. Likewise, in the retina, various studies in animal models and human patients suggested MMPs to be involved in glaucoma. In this study, we sought to determine the spatiotemporal expression profile of MMP-2 in the excitotoxic retina and to unravel its role during glaucoma pathogenesis. We reveal that intravitreal NMDA injection induces MMP-2 expression to be upregulated in the Müller glia. Moreover, MMP-2 null mice display attenuated retinal ganglion cell death upon excitotoxic insult to the retina, which is accompanied by normal glial reactivity, yet reduced TNF levels. Hence, we propose a novel in vivo function for MMP-2, as an activating sheddase of tumor necrosis factor (TNF). Given the pivotal role of TNF as a proinflammatory cytokine and neurodegeneration-exacerbating mediator, these findings generate important novel insights into the pathological processes contributing to glaucomatous neurodegeneration and into the interplay of neuroinflammation and neurodegeneration in the CNS. [ABSTRACT FROM AUTHOR]

Matrix metalloproteinases (MMPs) are Zn-dependent endopeptidases considered to be essential for normal brain development and neuroplasticity by modulating extracellular matrix proteins, receptors, adhesion molecules, growth factors and cytoskeletal proteins. Specifically, MMP-3 has recently been implicated in synaptic plasticity, hippocampus-dependent learning and neuronal development and migration in the cerebellum. However, the function(s) of this enzyme in the neocortex is understudied. Therefore, we explored the phenotypical characteristics of the neuronal architecture and the capacity for experience-dependent cortical plasticity in the visual cortex of adult MMP-3-deficient (MMP-3) mice. Golgi-Cox stainings revealed a significant reduction in apical dendritic length and an increased number of apical obliques for layer V pyramidal neurons in the visual cortex of adult MMP-3 mice compared to wild-type (WT) animals. In addition, a significant upregulation of both phosphorylated and non-phosphorylated neurofilament protein (NF)-high, phosphorylated NF-medium, NF-low and α-internexin was detected in the visual cortex of MMP-3 mice. To assess the effect of MMP-3 deficiency on cortical plasticity, we monocularly enucleated adult MMP-3 mice and analyzed the reactivation of the contralateral visual cortex 7 weeks post-enucleation. In contrast to previous results in C57Bl/6J adult mice, activity remained confined to the binocular zone and did not expand into the monocular regions indicative for an aberrant open-eye potentiation. Permanent hypoactivity in the monocular cortex lateral and medial to V1 also indicated a lack of cross-modal plasticity. These observations demonstrate that genetic inactivation of MMP-3 has profound effects on the structural integrity and plasticity response of the visual cortex of adult mice. [ABSTRACT FROM AUTHOR]

Purpose: Previous reports have yielded conflicting data on the activity of bevacizumab (Avastin), a recombinant humanized monoclonal antibody against VEGF-A, in the mouse. The current study was designed to further explore the use of this VEGF inhibitor in various murine models of ocular diseases and compare it to the widely used murine anti-VEGF-R2 neutralizing antibody (DC101). Methods: Murine models of laser-induced choroidal neovascularization (CNV), oxygen-induced retinopathy (OIR) and glaucoma filtration surgery (GFS) were used to investigate the effect of bevacizumab. Mice either received an intravitreal (CNV-OIR) or subconjunctival (GFS) injection. In all models, they were divided in two groups ( n = 10 per group). In the first group, one eye was injected with bevacizumab (1 µl; 25 µg) and the other eye was used as a negative control and received an injection of NaCl (1 µl; 0.9%). In the second group, one eye was injected with DC101 (1 µl; 6.2 µg), whereas an isotype-matched control antibody (1C8; 4.8 µg) was administered in the contralateral eye. Treatment outcome was studied by clinical investigation (GFS) and immunohistological analysis of angiogenesis (CD31/FITC-dextran/H&E) and fibrosis (Sirius Red). Results: Analysis of blood vessel density (CNV) and blood vessel growth (OIR) showed a comparable decrease after intravitreal administration of bevacizumab or DC101. Furthermore, in the mouse model of GFS, clinical investigation of the bleb and a CD31 staining on sections demonstrated that subconjunctival injection of both antibodies similarly improved the surgical outcome (bleb area and survival) by reducing angiogenesis. Moreover, morphometric analysis after Sirius Red staining showed a comparable reduction in collagen deposition after administration of the inhibitors. Conclusion: Our findings consistently demonstrate that bevacizumab is as effective as the murine anti-VEGF-R2 antibody (DC101) in mouse models of CNV, OIR and GFS, thus confirming its suitability for translational ophthalmological research. [ABSTRACT FROM AUTHOR]

Matrix metalloproteinase-2 (MMP-2) is a highly studied proteolytic enzyme, involved in many detrimental and beneficial functions throughout the body, and also active in the central nervous system (CNS). MMP-2 is profoundly expressed in the developing cerebellum and was recently reported to modulate granule cell proliferation by affecting cell cycle kinetics in cerebella of postnatal day 3 mouse pups. In this report, a two-dimensional difference gel electrophoresis proteomics study was implemented at this postnatal stage and revealed 16 differentially expressed proteins between MMP-2-deficient (MMP-2) and wild-type cerebella. Among those, collapsin response mediator protein 1 (CRMP1) could be identified as the most significant differential protein between the two genotypes. Western blot experiments confirmed this finding and further disclosed a significant increase in phosphorylated CRMP1 expression in MMP-2 cerebella. Strikingly, subsequent immunohistochemical and microscopic analyses revealed an aberrant Purkinje cell (PC) dendritogenesis, possibly related to upregulated (phospho-) CRMP1 levels in these neonatal MMP-2 animals. Further, detailed morphometric analyses showed persistent PC morphological changes in MMP-2 mice, from the neonatal stage until adulthood. These were characterized by a reduced growth of PC somata, reduced dendritic tree sizes, and a decreased dendritic arborization. During development, the observed defects were accompanied by a temporarily disturbed parallel fiber and climbing fiber synaptic input on the PCs, while in adult MMP-2 animals, an increased PC spine density and reduced spine lengths were noted. The observed PC abnormalities might contribute to the mild defects in motor performance, i.e. balance and coordination, detected in adult MMP-2 mice. Overall, these findings indicate the importance of MMP-2 in CNS development and dendritogenesis, and highlight the importance of a correct developmental wiring for adult brain morphology and function. [ABSTRACT FROM AUTHOR]

Restoration of correct neural activity following central nervous system ( CNS) damage requires the replacement of degenerated axons with newly outgrowing, functional axons. Unfortunately, spontaneous regeneration is largely lacking in the adult mammalian CNS. In order to establish successful regenerative therapies, an improved understanding of axonal outgrowth and the various molecules influencing it, is highly needed. Matrix metalloproteinases ( MMPs) constitute a family of zinc-dependent proteases that were sporadically reported to influence axon outgrowth. Using an ex vivo retinal explant model, we were able to show that broad-spectrum MMP inhibition reduces axon outgrowth of mouse retinal ganglion cells ( RGCs), implicating MMPs as beneficial factors in axonal regeneration. Additional studies, using more specific MMP inhibitors and MMP-deficient mice, disclosed that both MMP-2 and MT1- MMP, but not MMP-9, are involved in this process. Furthermore, administration of a novel antibody to MT1- MMP that selectively blocks pro- MMP-2 activation revealed a functional co-involvement of these proteinases in determining RGC axon outgrowth. Subsequent immunostainings showed expression of both MMP-2 and MT1- MMP in RGC axons and glial cells. Finally, results from combined inhibition of MMP-2 and β1-integrin were suggestive for a functional interaction between these molecules. Overall, our data indicate MMP-2 and MT1- MMP as promising axonal outgrowth-promoting molecules. [ABSTRACT FROM AUTHOR]

Purpose: Previous research in the AppNL‐G‐F mouse has shown that hyperspectral retinal imaging (HSRI) can be used to quantify retinal amyloid burden in the preclinical stages of Alzheimer's disease (AD) [1]. This underscores its potential as an imaging biomarker for AD diagnosis and monitoring. One prerequisite for the rational implementation of HSRI as a biomarker, however, is a better understanding of the pathological correlate of the HSRI signature. In this follow‐up study, we explored HSRI signatures in different proteinopathies and identified the pathological features underlying the observed HSRI results. Methods: Retinal tissues were collected from mouse models with amyloid, tau and alpha‐synuclein overexpression/aggregation for ex vivo HSRI (Snapscan, Imec) [1]. HSRI was complemented with optical coherence tomography and electroretinograms (prior to HSRI) and immunohistochemistry and molecular studies of protein aggregation (after HSRI). Results: While all protein aggregates led to HSRI changes in the 450–600 nm range, distinct signatures were observed for amyloid, tau and alpha‐synuclein. Furthermore, the observed HSRI changes correlated with levels of the protein oligomerization and aggregation. Diverging patterns of retinal dysfunction/degeneration were observed in the different mouse models, illustrating the varied impacts of these protein aggregates on retinal structure and function. Conclusions: HSRI may be used to quantify retinal amyloid, tau and alpha‐synuclein, underscoring its potential as a biomarker for diagnosis and disease monitoring. Moreover, our data suggest that amyloid, tau and alpha‐synuclein accumulation lead to distinct HSRI signatures, thus adding further evidence that HSRI may have utility in the diagnosis and stratification of proteinopathies associated with the most common forms of neurodegenerative diseases. Bibliograph: Vandenabeele et al. (2021) Acta Neuropathol Commun 9(1):6. [ABSTRACT FROM AUTHOR]

Abstract: Mice with a targeted truncation in the gene encoding tissue factor of blood coagulation (TF) to eliminate the cytosolic domain and carrying a neo R cassette in intron 5 unexpectedly displayed severe spontaneous thrombosis in various vascular beds. Thrombosis was observed in heterozygous TF+/neo mice, causing death of over 50% of adults within 36 weeks of birth, and fulminantly exacerbating in pregnant females. Homozygous TFneo/neo mice were more severely affected and died within 7 weeks after birth. These TFneo mice primarily synthesized a mutant mRNA aberrantly spliced from exon 5 to neo R , encoding an apparently non-vesicle-binding soluble TF lacking both the transmembrane and cytosolic domain, but still capable of blood coagulation induction. This severe thrombotic phenotype associated with the presence of a non-anchored soluble TF variant underscores the recently recognized significance of circulating TF for thrombus formation and development. [Copyright &y& Elsevier]

Reports that abrupt heart rate acceleration or premature beats cause life threatening arrhythmias in mice with long-QT3 syndrome. Description of arrhythmias; Anti-arrhythmic property of andrenergic agonists.

Neuroinflammation has been put forward as a mechanism triggering axonal regrowth in the mammalian central nervous system (CNS), yet little is known about the underlying cellular and molecular players connecting these two processes. In this study, we provide evidence that MMP2 is an essential factor linking inflammation to axonal regeneration by using an in vivo mouse model of inflammation-induced axonal regeneration in the optic nerve. We show that infiltrating myeloid cells abundantly express MMP2 and that MMP2 deficiency results in reduced long-distance axonal regeneration. However, this phenotype can be rescued by restoring MMP2 expression in myeloid cells via a heterologous bone marrow transplantation. Furthermore, while MMP2 deficiency does not affect the number of infiltrating myeloid cells, it does determine the coordinated expression of pro- and anti-inflammatory molecules. Altogether, in addition to its role in axonal regeneration via resolution of the glial scar, here, we reveal a new mechanism via which MMP2 facilitates axonal regeneration, namely orchestrating the expression of pro- and anti-inflammatory molecules by infiltrating innate immune cells. [ABSTRACT FROM AUTHOR]

Mouse disease models have proven indispensable in glaucoma research, yet the complexity of the vast number of models and mouse strains has also led to confusing findings. In this study, we evaluated baseline intraocular pressure, retinal histology, and retinofugal projections in three mouse strains commonly used in glaucoma research, i.e. C57Bl/6, C57Bl/6-Tyr c , and CD-1 mice. We found that the mouse strains under study do not only display moderate variations in their intraocular pressure, retinal architecture, and retinal ganglion cell density, also the retinofugal projections to the dorsal lateral geniculate nucleus and the superior colliculus revealed striking differences, potentially underlying diverging optokinetic tracking responses and visual acuity. Next, we reviewed the success rate of three models of (glaucomatous) optic neuropathies (intravitreal N-methyl- d -aspartic acid injection, optic nerve crush, and laser photocoagulation-induced ocular hypertension), looking for differences in disease susceptibility between these mouse strains. Different genetic backgrounds and albinism led to differential susceptibility to experimentally induced retinal ganglion cell death among these three mouse strains. Overall, CD-1 mice appeared to have the highest sensitivity to retinal ganglion cell damage, while the C57Bl/6 background was more resistant in the three models used. [ABSTRACT FROM AUTHOR]

The γ-secretase complex plays a role in Alzheimer's disease and cancer progression. The development of clinically useful inhibitors, however, is complicated by the role of the γ-secretase complex in regulated intramembrane proteolysis of Notch and other essential proteins. Different γ-secretase complexes containing different Presenilin or Aph1 protein subunits are present in various tissues. Here we show that these complexes have heterogeneous biochemical and physiological properties. Specific inactivation of the Aph1B γ-secretase in a mouse Alzheimer's disease model led to improvements of Alzheimer's disease-relevant phenotypic features without any Notch-related side effects. The Aph1B complex contributes to total γ-secretase activity in the human brain, and thus specific targeting of Aph1B-containing γ-Secretase complexes may help generate less toxic therapies for Alzheimer's disease. [ABSTRACT FROM AUTHOR]

The mechanisms of BM hematopoietic stem/progenitor cell (HSPC) adhesion, engraftment, and mobilization remain incompletely identified. Here, using WT and transgenic mice, we have shown that membrane-anchored plasminogen activator, urokinase receptor (MuPAR) marks a subset of HSPCs and promotes the preservation of the size of this pool of cells in the BM. Loss or inhibition of MuPAR increased HSPC proliferation and impaired their homing, engraftment, and adhesion to the BM microenvironment. During mobilization, MuPAR was inactivated by plasmin via proteolytic cleavage. Cell-autonomous loss of the gene encoding MuPAR also impaired long-term engraftment and multilineage repopulation in primary and secondary recipient mice. These findings identify MuPAR and plasmin as regulators of the proliferation, marrow pool size, homing, engraftment, and mobilization of HSPCs and possibly also of HSCs. [ABSTRACT FROM AUTHOR]