Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disorder characterised by a progressive loss of motor function. Despite the strives into growing knowledge on ALS, fundamental... Show moreAmyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disorder characterised by a progressive loss of motor function. Despite the strives into growing knowledge on ALS, fundamental obstacles remain into understanding disease causation and nominating drug targets for a cure. With this work, we widen our understanding of ALS through the analysis of single-nuclei RNA-sequencing dataset of patients’ and control motorcortices. We show intrinsically higher expression of ALS-related genes in Extratelencephalic Neurons accompanied by selective vulnerability of subsets of cortical motor neurons. These changes are found with alterations in oligodendrocytes and microglia that widen our knowledge of cell-to-cell interactions in ALS. We use hiPSC-derived in vitro systems to model the molecular changes identified. Secondly, we offer a wide view on models of human brain cells in a dish to encompass protocols useful for modelling complex cell-to-cell interactions in ALS. Moreover, we describe a human in vitro system for the study of motor neuron that is highly reproducible, scalable and high-throughput. This new method allows the assessment of multiple cell lines in the same dish and could provide insights into heterogeneity in human populations and mechanisms disrupted in disease. We then use these models to further dissect molecular mechanisms disrupted in ALS. We undertake a discussion onto the future of the field and hopefully the opening to a more holistic approach to the understanding of ALS, where multidisciplinary techniques and the use of different models might expand our perspectives on the disease. Show less
Alzheimer’s disease (AD) is the most common cause of dementia and quickly becoming one of the most burdening diseases of the century. Effective treatments are still missing, partially because its... Show moreAlzheimer’s disease (AD) is the most common cause of dementia and quickly becoming one of the most burdening diseases of the century. Effective treatments are still missing, partially because its pathogenesis is still incompletely understood. This thesis explores the role of iron in AD, how it interacts with the immune system to influence disease pathogenesis and whether it could serve as potential biomarker. The first part of this thesis describes the importance of translational MRI, and how it can be used to increase our understanding of neurological diseases and help identify biomarkers. Subsequently, we used translational MRI to characterize the differences in iron accumulation in the brain between patients with AD and healthy elderly. The second part of this thesis investigated how the immune cells of the brain, microglia, interact with the accumulated iron. Using a combination of advanced multispectral immunofluorescence on brain tissue from AD patients and a human stem-cell derived microglia model, we studied the activation pattern of iron-accumulating microglia in human brains and emulated microglial iron accumulation in vitro. This enabled us to study the effect of iron on the gene expression patterns and function of the brain’s immune cells. Show less
Kenkhuis, B.; Somarakis, A.; Kleindouwel, L.R.T.; Roon-Mom, W.M.C. van; Hollt, T.; Weerd, L. van der 2022
Microglia have been identified as key players in Alzheimer's disease pathogenesis, and other neurodegenerative diseases. Iba1, and more specifically TMEM119 and P2RY12 are gaining ground as... Show moreMicroglia have been identified as key players in Alzheimer's 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. Show less
The glioma microenvironment harbors a variety of immune cells including innate immune cells such as monocytes, macrophages and microglia. Microglia are the major innate immune cells present in the... Show moreThe glioma microenvironment harbors a variety of immune cells including innate immune cells such as monocytes, macrophages and microglia. Microglia are the major innate immune cells present in the glioma microenvironment. Communication between glioma and these immune cells is crucial to maintain a tumor-promoting environment. In this thesis the role of a specific type of communication is described. In detail, the consequence of extracellular communication from glioma to the innate immune cells is studied, this includes the transferring of messages (including miRNAs) through extracellular vesicles. In addition, the changes that these cells undergo in the presence of a tumor is documented. Show less
Marco, R. de; Ronen, I.; Branzoli, F.; Amato, M.L.; Asllani, I.; Colasanti, A.; ... ; Cercignani, M. 2022
Background: Low-dose lipopolysaccharide (LPS) is a well-established experimental method for inducing systemic inflammation and shown by microscopy to activate microglia in rodents. Currently,... Show moreBackground: Low-dose lipopolysaccharide (LPS) is a well-established experimental method for inducing systemic inflammation and shown by microscopy to activate microglia in rodents. Currently, techniques for in-vivo imaging of glia in humans are limited to TSPO (Translocator protein) PET, which is expensive, methodologically challenging, and has poor cellular specificity. Diffusion-weighted magnetic resonance spectroscopy (DW-MRS) sensitizes MR spectra to diffusion of intracellular metabolites, potentially providing cell-specific information about cellular morphology. In this preliminary study, we applied DW-MRS to measure changes in the apparent diffusion coefficients (ADC) of glial and neuronal metabolites to healthy participants who underwent an LPS administration protocol. We hypothesized that the ADC of glial metabolites will be selectively modulated by LPSinduced glial activation. Methods: Seven healthy male volunteers, (mean 25.3 +/- 5.9 years) were each tested in two separate sessions once after LPS (1 ng/Kg intravenously) and once after placebo (saline). Physiological responses were monitored during each session and serial blood samples and Profile of Mood States (POMS) completed to quantify white blood cell (WBC), cytokine and mood responses. DW-MRS data were acquired 5-51/2 hours after injection from two brain regions: grey matter in the left thalamus, and frontal white matter. Results: Body temperature, heart rate, WBC and inflammatory cytokines were significantly higher in the LPS compared to the placebo condition (p < 0.001). The ADC of the glial metabolite choline (tCho) was also significantly increased after LPS administration compared to placebo (p = 0.008) in the thalamus which scaled with LPS-induced changes in POMS total and negative mood (Adj R-2 = 0.83; p = 0.004). Conclusions: DW-MRS may be a powerful new tool sensitive to glial cytomorphological changes in grey matter induced by systemic inflammation. Show less
Kenkhuis, B.; Somarakis, A.; Haan, L. de; Dzyubachyk, O.; IJsselsteijn, M.E.; Miranda, N.F.C.C. de; ... ; Weerd, L. van der 2021
Brain iron accumulation has been found to accelerate disease progression in amyloid-beta(A beta) positive Alzheimer patients, though the mechanism is still unknown. Microglia have been identified... Show moreBrain iron accumulation has been found to accelerate disease progression in amyloid-beta(A 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 A 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. Show less
The ventral tegmental area dopamine (VTA-DA) mesolimbic circuit processes emotional, motivational, and social reward associations together with their more demanding cognitive aspects that involve... Show moreThe ventral tegmental area dopamine (VTA-DA) mesolimbic circuit processes emotional, motivational, and social reward associations together with their more demanding cognitive aspects that involve the mesocortical circuitry. Coping with stress increases VTA-DA excitability, but when the stressor becomes chronic the VTA-DA circuit is less active, which may lead to degeneration and local microglial activation. This switch between activation and inhibition of VTA-DA neurons is modulated by e.g. corticotropin-releasing hormone (CRH), opioids, brain-derived neurotrophic factor (BDNF), and the adrenal glucocorticoids. These actions are coordinated with energy-demanding stress-coping styles to promote behavioral adaptation. The VTA circuits show sexual dimorphism that is programmed by sex hormones during perinatal life in a manner that can be affected by glucocorticoid exposure. We conclude that insight in the role of stress in VTA-DA plasticity and connectivity, during reward processing and stress-coping, will be helpful to better understand the mechanism of resilience to breakdown of adaptation. Show less
Bulk, M.; Hegeman-Kleinn, I.; Kenkhuis, B.; Suidgeest, E.; Roon-Mom, W. van; Lewerenz, J.; ... ; Weerd, L. van der 2020
Previous MRI studies consistently reported iron accumulation within the striatum of patients with Huntington's disease (HD). However, the pattern and origin of iron accumulation is poorly... Show morePrevious MRI studies consistently reported iron accumulation within the striatum of patients with Huntington's disease (HD). However, the pattern and origin of iron accumulation is poorly understood. This study aimed to characterize the histopathological correlates of iron-sensitive ex vivo MRI contrast change in HD brains. To this end, T2*-weighted 7T MRI was performed on postmortem tissue of the striatum of three control subjects and 10 HD patients followed by histological examination. In addition, formalin-fixed paraffin-embedded material of three control subjects and 14 HD patients was selected for only histology to identify the cellular localization of iron using stainings for iron, myelin, microglia and astrocytes. As expected HD striata showed prominent atrophy. Compared to controls, the striatum of HD patients was in general more hypointense on T2*-weighted highfield MRI and showed a more intense histopathological staining for iron. In addition, T2*-weighted MRI identified large focal hypointensities within the striatum of HD patients. Upon histological examination, these large focal hypointensities frequently colocalized with enlarged perivascular spaces and iron was found within the vessel wall and reactive astrocytes. In conclusion, we show that the striatum of HD patients has a distinctive phenotype on T2*-weighted MRI compared to control subjects. On ex vivo MRI, these contrast changes are heavily biased by enlarged perivascular spaces from which it is currently unknown whether this is a fixation artefact or a disease specific observation. Clinically, the observation of iron within reactive astrocytes is of importance for the interpretation and understanding of the potential underlying mechanisms of T2*-weighted MRI results in HD patients. Show less
Westhoff, D.; Engelen-Lee, J.Y.; Hoogland, I.C.M.; Aronica, E.M.A.; Westerloo, D.J. van; Beek, D. van de; Gool, W.A. van 2019
Worldwide, raised blood pressure is estimated to affect 35-40% of the adult population and is a main conditioning factor for cardiovascular diseases and stroke. Animal models of hypertension have... Show moreWorldwide, raised blood pressure is estimated to affect 35-40% of the adult population and is a main conditioning factor for cardiovascular diseases and stroke. Animal models of hypertension have provided great advances concerning the pathophysiology of human hypertension, as already shown for the deoxycorticosterone-salt treated rat, the Dahl-salt sensitive rat, the Zucker obese rat and the spontaneously hypertensive rat (SHR). SHR has been widely used to study abnormalities of the brain in chronic hypertension. This review summarises present and past evidence that in the SHR, hypertension causes hippocampal tissue damage which triggers a pro-inflammatory feedforward cascade affecting this vulnerable brain region. The cascade is driven by mineralocorticoid receptor (MR) activation responding to endogenous corticosterone rather than aldosterone. Increased MR expression is a generalised feature of the SHR which seems to support first the rise in blood pressure. Then oxidative stress caused by vasculopathy and hypoxia further increases MR activation in hippocampal neurons and glia cells, activates microglia activation and pro-inflammatory mediators, and down-regulates anti-inflammatory factors. In contrast to MR, involvement of the glucocorticoid receptor (GR) in SHR is less certain. GR showed normal expression levels and blockage with an antagonist failed to reduce blood pressure of SHR. The findings support the concept that MR:GR imbalance caused by vasculopathy causes a switch in MR function towards a proverbial "death" receptor. Show less
Inherited retinal diseases encompass a large group of clinically and genetically heterogeneous diseases estimated to affect two million people worldwide. Among these people, approximately 80,000... Show moreInherited retinal diseases encompass a large group of clinically and genetically heterogeneous diseases estimated to affect two million people worldwide. Among these people, approximately 80,000 are or will become blind in their first decades of life due to mutations in both alleles of the Crumbs homologue-1 (CRB1) gene. Microglia are the resident immune surveyor cells in the retina, and their roles have been heavily studied in several retinal diseases, including retinitis pigmentosa (RP), age-related macular degeneration, and diabetic retinopathy. However, very little is known about the role of microglia in CRB1-associated retinopathies. Thus, we here summarize the main findings described in the literature concerning inflammation and the role of microglia in CRB1-patients and CRB1-rodent models. Show less
Activation of microglia, the macrophages of the central nervous system, is a key element in multiple sclerosis (MS) lesion development and is characterized by enhanced expression of both classes of... Show moreActivation of microglia, the macrophages of the central nervous system, is a key element in multiple sclerosis (MS) lesion development and is characterized by enhanced expression of both classes of major histocompatibility complex (MHC) molecules. This enhanced expression results from increased levels of several transcription factors involved in MHC gene expression. In addition, microglial activation in MS is characterized by enhanced motility. We show that the expression of the chemokine receptor CCR5, a mediator of cell movement, is increased on microglia, macrophages and astrocytes in MS lesions. Additionally, we have determined that CCR5 transcription is regulated by the transcription factor CREB-1, which is also involved in MHC gene expression, and is highly expressed in MS lesions. Because of their immunomodulatory properties, statins (cholesterol lowering drugs) are recently being considered as a possible treatment for MS. We have determined that statins decrease expression of amongst others MHC and CCR5 molecules by inhibiting the transport of these molecules to the cell surface. In addition, we show that statins reduce the motility of microglia and inhibit the differentiation of blood-derived monocytes into dendritic cells, indicating that statins indeed affect critical immune functions and might prove to be beneficial for treatment of MS patients. Show less
