Biology subjects

van der Weerd, L.

Publications and source records attributed to van der Weerd, L..

9 recordsLinked to original sources

bioRxiv2026

The D2-mdx mouse as a preclinical model for Duchenne muscular dystrophy: a natural history study across two independent sites

IntroductionThe quality of preclinical studies for rare diseases, such as Duchenne muscular dystrophy (DMD), relies on the availability of comprehensive natural disease history data. In addition to the classic BL10-mdx mouse, in recent years, the D2-mdx model has increasingly been used as an alternative model due to its reportedly more severely impaired phenotype. To improve our understanding of disease progression in these two DMD models, we conducted a comprehensive natural history study. Materials and MethodsThis involved a cross-sectional analysis of key in vivo and ex vivo outcome measures performed in two independent laboratories, using the same study setup in compliance with TREAT-NMD Standard Operating Procedures (SOPs), while also taking advantage of site-specific expertise. Globally, largely comparable results were obtained across the two study sites. ResultsBody composition showed pronounced differences between the strains, with BL10-mdx mice displaying a hypertrophic and D2-mdx mice displaying an atrophic phenotype. Dystrophic mice of each strain exhibited significant alterations of disease-relevant indices related to muscle functionality and integrity, mostly worsening with age, in comparison to their wildtypes. Cardiac function was affected earlier and more severely in D2-mdx mice. DiscussionNotably, for some parameters, genetic-background related differences were observed, emphasizing the need to include control groups with matching genetic backgrounds in experimental designs. ConclusionsCollectively, our natural history study provides benchmark data for these two mdx mouse strains to guide model selection for preclinical DMD studies, allowing accurate data interpretation. HighlightsO_LIDistinct body composition phenotypes: BL10-mdx mice exhibit pseudohypertrophy while D2-mdx mice display pronounced atrophy. C_LIO_LIEarlier cardiac dysfunction in D2-mdx: D2-mdx mice develop reduced ejection fraction and stroke volume from 28 weeks, while BL10-mdx only at 52 weeks. C_LIO_LIGenetic background-dependent variations: Intrinsic deficits in wildtype D2 mice demonstrate that genetic background influences outcome measures independent of dystrophic pathology. C_LIO_LIComparable ex vivo muscle physiology: Despite divergent in vivo phenotypes, isolated muscle contractile parameters show similar impairment in both dystrophic models. C_LIO_LIMulti-site standardized validation: Cross-sectional study at two independent laboratories following harmonized TREAT-NMD Standard Operating Procedures. C_LI

pharmacology and toxicology↗

bioRxiv2025

Advancing Therapeutic Solutions: Poloxamer-based Thermosensitive Injectable Hydrogels containing a Self-assembling Peptide for In situ Gelation in an Osteoarthritis Murine Model

This study presents the development and characterization of a novel thermosensitive injectable hydrogel designed to enhance the biomechanical properties of poloxamer 407 (P407) through the incorporation of a self-assembling peptide. The primary objective was to engineer a formulation that rapidly gels following intra-articular (i.a.) injection, exhibits improved mechanical strength, and enables sustained release of embedded therapeutic cargo. Gelation time assays demonstrated that the P407-peptide formulation solidified more quickly than P407 alone at equivalent concentrations. Rheological analysis revealed a 1.5 kPa increase in storage modulus in the hybrid hydrogel, confirming improved mechanical integrity. In vitro biocompatibility was assessed using human chondrocytes, with MTS assays and LIVE/DEAD staining indicating no cytotoxicity across tested concentrations. To evaluate in vivo applicability, a near-infrared fluorescent (NIRF) dye was incorporated into the hydrogel and injected intra-articularly into an osteoarthritis (OA) mouse model. The labeled formulation allowed for successful tracking and demonstrated localized gelation, supporting its suitability for site-specific, sustained delivery. Overall, the P407-peptide hydrogel offers a promising platform for i.a. therapeutic applications, combining injectability, rapid thermoresponsive gelation, mechanical reinforcement, and controlled release behavior, making it well-suited for regenerative medicine and OA treatment.

biochemistry↗

bioRxiv2024

GeneSurfer Enables Transcriptome-wide Exploration and Functional Annotation of Gene Co-expression Modules in 3D Spatial Transcriptomics Data

Gene co-expression provides crucial insights into biological functions, however, there is a lack of exploratory analysis tools for localized gene co-expression in large-scale datasets. We present GeneSurfer, an interactive interface designed to explore localized transcriptome-wide gene co-expression patterns in the 3D spatial domain. Key features of GeneSurfer include transcriptome-wide gene filtering and gene clustering based on spatial local co-expression within transcriptomically similar cells, multi-slice 3D rendering of average expression of gene clusters, and on-the-fly Gene Ontology term annotation of co-expressed gene sets. Additionally, GeneSurfer offers multiple linked views for investigating individual genes or gene co-expression in the spatial domain at each exploration stage. Demonstrating its utility with both spatial transcriptomics and single-cell RNA sequencing data from the Allen Brain Cell Atlas, GeneSurfer effectively identifies and annotates localized transcriptome-wide co-expression, providing biological insights and facilitating hypothesis generation and validation.

bioinformatics↗

bioRxiv2022

Multi-scale Assessment of Brain Blood Volume and Perfusion in the APP/PS1 Mouse Model of Amyloidosis

Vascular dysfunction is increasingly recognized to play a role in the development of Alzheimers disease (AD). The relation between vascular dysfunction and the neuropathological amyloid {beta} accumulation characteristic for AD is however unclear. The limited resolution of in vivo imaging techniques, the intricate 3D structure of the microvasculature and the different co-occurring types of amyloid {beta} accumulation in patients hamper studying this relation in patients. Here, we therefore employed the APP/PS1 mouse model, which develops parenchymal amyloid {beta} plaques, to study the effect of parenchymal amyloid {beta} plaques on the structure and function of the vasculature. Blood vessels and amyloid {beta} plaques were fluorescently labeled in vivo with lectin-DyLight594 and methoxy XO4, respectively, in APP/PS1 mice at old age. The brain tissue was cleared post-mortem with the CUBIC clearing protocol, which allowed structural imaging at microscopic resolution of the vessels and plaques in a large 3D volume. Segmentation of the vasculature enabled mapping of the microvascular Cerebral Blood Volume (mCBV), which ranged from 2 % to 5 % in the white matter and the thalamus, respectively. No mCBV differences were observed between APP/PS1 mice and wild type (WT) control mice. The effect of the amyloid {beta} plaques on vascular function was studied in vivo by measuring Cerebral Blood Flow (CBF) and Arterial Transit Time (ATT) with Arterial Spin Labeling (ASL) MRI. Similar to the mCBV findings, no differences were observed in CBF or ATT between APP/PS1 and control mice, indicating that brain vascular morphology and function in this mouse model are preserved in the presence of amyloid {beta} plaques.

neuroscience↗

bioRxiv2021

Co-expression patterns of microglia markers Iba1, TMEM119 and P2RY12 in Alzheimer's disease

Microglia have been identified as key players in Alzheimers disease pathogenesis, and other neurodegenerative diseases. Iba1, and more specifically TMEM119 and P2RY12 are gaining ground as presumedly more specific microglia markers, but comprehensive characterization of the expression of these three markers individually as well as combined is currently missing. Here we used a multispectral immunofluorescence dataset, in which over seventy thousand microglia from both aged controls and Alzheimer patients have been analysed for expression of Iba1, TMEM119 and P2RY12 on a single-cell level. For all markers, we studied the overlap and differences in expression patterns and the effect of proximity to {beta}-amyloid plaques. We found no difference in absolute microglia numbers between control and Alzheimer subjects, but the prevalence of specific combinations of markers (phenotypes) differed greatly. In controls, the majority of microglia expressed all three markers. In Alzheimer patients, a significant loss of TMEM119+-phenotypes was observed, independent of the presence of {beta}-amyloid plaques in its proximity. Contrary, phenotypes showing loss of P2RY12, but consistent Iba1 expression were increasingly prevalent around {beta}-amyloid plaques. No morphological features were conclusively associated with loss or gain of any of the markers or any of the identified phenotypes. All in all, none of the three markers were expressed by all microglia, nor can be wholly regarded as a pan- or homeostatic marker, and preferential phenotypes were observed depending on the surrounding pathological or homeostatic environment. This work could help select and interpret microglia markers in previous and future studies.

neuroscience↗

bioRxiv2021

Off-resonance saturation as an MRI method to quantify ferritin-bound iron in the post-mortem brain

PurposeTo employ an Off-Resonance Saturation (ORS) method to measure the ferritin-bound iron pool, which is an endogenous contrast agent which can give information on cellular iron status. MethodsAn ORS acquisition protocol was implemented on a 7T preclinical scanner and the contrast maps were fitted to an established analytical model. The method was validated by correlation and Bland-Altman analysis on a ferritin-containing phantom. Ferritin-iron maps were obtained from post-mortem tissue of patients with neurological diseases characterized by brain iron accumulation, i. e. Alzheimers disease, Huntingtons disease and aceruloplasminemia, and validated with histology. Transverse relaxation rate and magnetic susceptibility values were also obtained for comparison. ResultsIn post-mortem tissue, the ferritin-iron contrast strongly co-localizes with histological iron staining, in all the cases. Quantitative iron values obtained via the ORS method are in agreement with literature. ConclusionsOff-resonance saturation is an effective way to detect iron in grey matter structures, while mitigating for the presence of myelin. If a reference region with little iron is available in the tissue, the method can produce quantitative iron maps. This method is applicable in the study of brain diseases characterized by brain iron accumulation and complement existing iron-sensitive parametric methods.

biophysics↗

bioRxiv2021

Iron-loading is a prominent feature of activated microglia in Alzheimer's disease patients

Brain iron accumulation has been found to accelerate disease progression in Amyloid {beta}-positive Alzheimer patients, though the mechanism is still unknown. Microglia have been identified as key-players in the disease pathogenesis, and are highly reactive cells responding to aberrations such as increased iron levels. Therefore, using histological methods, multispectral immunofluorescence and an automated in-house developed microglia segmentation and analysis pipeline, we studied the occurrence of iron-accumulating microglia and the effect on its activation state in human Alzheimer brains. We identified a subset of microglia with increased expression of the iron storage protein ferritin light chain (FTL), together with increased Iba1 expression, decreased TMEM119 and P2RY12 expression. This activated microglia subset represented iron-accumulating microglia and appeared morphologically dystrophic. Multispectral immunofluorescence allowed for spatial analysis of FTL+Iba1+-microglia, which were found to be the predominant A{beta}-plaque infiltrating microglia. Finally, an increase of FTL+Iba1+-microglia was seen in patients with high Amyloid-{beta} load and Tau load. These findings suggest iron to be taken up by microglia and to influence the functional phenotype of these cells, especially in conjunction with A{beta}.

neuroscience↗

bioRxiv2020

Effects of Alzheimer's disease and formalin fixation on the different mineralised-iron forms in the human brain

Iron accumulation in the brain is a phenomenon common to many neurodegenerative diseases, perhaps most notably Alzheimers disease (AD). We present here magnetic analyses of post-mortem brain tissue of patients who had severe Alzheimers disease, and compare the results with those from healthy controls. Isothermal remanent magnetization experiments were performed to assess the extent to which different magnetic carriers are affected by AD pathology and formalin fixation. While Alzheimers brain material did not show higher levels of magnetite/maghemite nanoparticles than corresponding controls, the ferrihydrite mineral, known to be found within the core of ferritin proteins and hemosiderin aggregates, almost doubled in concentration in patients with Alzheimers pathology, strengthening the conclusions of our previous studies. As part of this study, we also investigated the effects of sample preparation, by performing experiments on frozen tissue as well as tissue which had been fixed in formalin for a period of five months. Our results showed that the two different preparations did not critically affect the concentration of magnetic carriers in brain tissue, as observable by SQUID magnetometry.

biophysics↗

bioRxiv2018

Post-mortem T2*- weighted MRI imaging of cortical iron reflects severity of Alzheimer’s Disease

The value of iron-based MRI changes for the diagnosis and staging of Alzheimers disease (AD) depends on an association between cortical iron accumulation and AD pathology. Therefore, this study determined the cortical distribution pattern of MRI contrast changes in cortical regions selected based on the known distribution pattern of tau pathology and investigated whether MRI contrast changes reflect the underlying AD pathology in the different lobes.[Formula]-weighted MRI was performed on post-mortem cortical tissue of controls, late-onset AD, and early-onset AD followed by histology and correlation analyses. Combining ex-vivo high-resolution MRI and histopathology revealed that: LOAD and EOAD have a different distribution pattern of AD pathological hallmarks and MRI contrast changes over the cortex, with EOAD showing more severe MRI changes; (2) per lobe, severity of AD pathological hallmarks correlates with iron accumulation, and hence with MRI. Therefore, iron-sensitive MRI sequences allow detection of the cortical distribution pattern of AD pathology ex-vivo.\n\nAbbreviations

neuroscience↗