Biology subjects

Quek, H.

Publications and source records attributed to Quek, H..

8 recordsLinked to original sources

bioRxiv2026

Alzheimer's Disease-Associated Proteomic Changes in Olfactory Stem Cells Show Pathway-Level Transcriptomic Overlap

Alzheimer's disease (AD) is a progressive, neurodegenerative disorder and the leading cause of dementia worldwide. Although recent therapeutic advances have provided some disease-modifying potential, there is currently no curative treatment for AD, highlighting the need for improved disease models and early biomarkers. Olfactory mucosal stem cells, which can be expanded in vitro as olfactory neurosphere-derived (ONS) cells, represent a promising source for biomarker discovery because olfactory tissue is more accessible than central nervous system tissue and has been reported to exhibit AD-related pathological changes. In this study, we used subcellular fractionation-based proteomics, reconstructed bulk proteomics and integrated transcriptomic-proteomic analyses to characterise alterations in ONS cells derived from healthy control, mild cognitive impairment (MCI) and AD individuals. Fraction-specific proteomics identified cytoplasmic and nuclear-enriched protein abundance changes, including alterations in proteins and pathways associated with cytoskeletal organisation, RNA processing, intracellular trafficking, autophagy and mitochondrial/metabolic processes. Reduced LC3B abundance in cytoplasmic AD ONS cells was supported by western blot analysis, although LC3B abundance alone does not indicate altered autophagic flux. Reconstructed bulk proteomics identified 40 FDR-significant proteins in AD compared with HC, defining an AD-associated protein signature enriched for extracellular matrix, cytoskeletal, organelle-associated and RNA-processing pathways. Despite proteomic enrichment of mitochondrial and metabolic pathways, Seahorse Mito Stress Test analysis did not identify significant group-level differences in mitochondrial respiration. Integrated transcriptomic-proteomic analysis revealed partial RNA-protein concordance and pathway-level overlap across disease-associated processes. Together, these findings support the use of patient-derived ONS cells as a model for investigating AD- and MCI-associated molecular changes and highlight protein signatures for further validation.

neuroscience↗

bioRxiv2026

Regional and sub-regional microglial heterogeneity in the steady-state mouse brain and retina

CNS-resident immune cells are uniquely adapted to their microenvironment; however, the extent of their regional specialisation remains unclear. We combined morphometric and transcriptomic profiling of microglia across the healthy adult mouse CNS, including the olfactory bulbs, cortex, hippocampus, cerebellum and retina, to define their regional and sub-regional heterogeneity. Bulk RNA-sequencing revealed region-specific signatures, with retinal microglia showing the most divergent transcriptomes, and genes related to antigen presentation, phagocytosis and chemokine signalling among the top differentially expressed genes. Single-cell RNA sequencing identified predominantly homeostatic microglia across all examined regions, alongside smaller clusters of interferon-responsive, chemokine-enriched, apolipoprotein-enriched and proliferative microglia. Apolipoprotein-enriched microglia were restricted to the olfactory bulbs, whereas interferon-responsive microglia were most abundant in the retina. Single-cell profiling of human retinal microglia confirmed clusters enriched for interferon-stimulated genes. Together, this study reveals previously unrecognised microglial heterogeneity within the healthy brain and eye and provides a comparison of microglia transcriptomes across different neuroanatomical regions of the CNS.

immunology↗

bioRxiv2024

Impact of wildfire smoke and diesel exhaust on inflammatory response in aging human microglia

BackgroundAir pollution, particularly from Diesel Exhaust Particles (DEP) and Wildfire Smoke (WFS), is increasingly recognised as a significant driver of neuroinflammation linked to brain diseases. However, the role of microglia in mediating these neuroinflammatory responses remains poorly understood. This study aimed to investigate the effects of air pollution on monocyte-derived microglia-like cells (MDMi) from both young (< 40 years of age), and (older > 60 years of age) healthy individuals, focusing on immune response, cytokine secretion, nitrosative stress, and phagocytic activity. ResultsOur study demonstrated that DEP and WFS extract (WFSE) significantly upregulated expression of the oxidative stress marker, heme-oxygenase-1 (HO-1) in MDMi after 24 hr, with levels normalising by 96 hr, indicating a transient oxidative stress response. Both DEP and WFSE elicited distinct inflammatory cytokine profiles. DEP induced a rapid response, increasing TNF-, IL-6, IL-23, and IL-33 within 2 hr in young MDMi and 24 hr in aged MDMi. In contrast, WFSE triggered a delayed but sustained inflammatory response, with TNF-, IFN-{gamma}, IL-23, and IL-33 levels persisting at 96 hr in aged MDMi, highlighting an age-related vulnerability to air pollutant-induced inflammation. Both pollutants activated p38, ERK, and NF-{kappa}B pathways, with p38 activity resolving by 96 hours and ERK activation persisting, reflecting their distinct roles in cellular stress and inflammation. NF-{kappa}B p65 nuclear translocation, observed at 24 hours, highlighted its critical role in cytokine release and inflammation following exposure to DEP and WFSE. This is the first report of NF-{kappa}B activation in human microglia exposed to air pollutants. ConclusionsThese results highlight the distinct and potentially harmful effects of DEP and WFSE on immune and inflammatory responses in MDMi, particularly in ageing populations, with significant implications for brain health. DEP triggers acute oxidative stress and inflammatory responses, while WFSE induces more prolonged effects, especially in aged microglia. Both pollutants activate the MAPK and NF-{kappa}B pathways and exhibit unique cytokine profiles, underscoring their overlapping yet distinct mechanisms of action. These findings advance our understanding of air pollutant-induced neuroinflammation and its contribution to neurodegeneration, providing a foundation for developing targeted interventions to mitigate the neurotoxic effects of air pollution.

cell biology↗

bioRxiv2023

A patient-derived blood-brain barrier model for screening copper bis(thiosemicarbazone) complexes as potential therapeutics in Alzheimer's disease

Alzheimers disease (AD) is the most prevalent cause of dementia characterised by progressive cognitive decline. Addressing neuroinflammation represents a promising therapeutic avenue to treat AD, however, the development of effective anti-neuroinflammatory compounds is often hindered by their limited blood-brain barrier (BBB) permeability. Consequently, there is an urgent need for accurate, preclinical AD patient-specific BBB models to facilitate the early identification of immunomodulatory drugs capable of efficiently crossing human AD BBB. This study presents a unique approach to BBB drug permeability screening as it utilises the familial AD patient-derived induced brain endothelial-like cells (iBEC)-based model, which exhibits increased disease relevance and serves as an improved BBB drug permeability assessment tool when compared to traditionally employed in vitro models. To demonstrate its utility as a small molecule drug candidate screening platform, we investigated the effects of CuII(atsm) and a library of novel metal bis(thiosemicarbazone) complexes - a class of compounds exhibiting anti-neuroinflammatory therapeutic potential in neurodegenerative disorders. By evaluating the toxicity, cellular accumulation and permeability of those compounds in the AD patient-derived iBEC, we have identified CuII(dtsm) as an emerging drug candidate with enhanced transport across the AD BBB. Furthermore, we have developed a multiplex approach where AD patient-derived iBEC were combined with immune modulators TNF and IFN{gamma} to establish an in vitro model representing the characteristic neuroinflammatory phenotype at the patients BBB. Here we observed that treatment with CuII(dtsm) not only reduced the expression of proinflammatory cytokine genes but also reversed the detrimental effects of TNF and IFN{psi} on the integrity and function of the AD iBEC monolayer. This suggests a novel pathway through which copper bis(thiosemicarbazone) complexes may exert neurotherapeutic effects in AD by mitigating BBB neuroinflammation and related BBB integrity impairment. Together, the presented model provides an effective and easily scalable in vitro BBB platform for screening AD drug candidates. Its improved translational potential makes it a valuable tool for advancing the development of metal-based compounds aimed at modulating neuroinflammation in AD. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=199 HEIGHT=200 SRC="FIGDIR/small/554047v1_ufig1.gif" ALT="Figure 1"> View larger version (71K): org.highwire.dtl.DTLVardef@1d949b5org.highwire.dtl.DTLVardef@7629ccorg.highwire.dtl.DTLVardef@1b2125dorg.highwire.dtl.DTLVardef@1d3cde1_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2023

A novel patient-derived cellular platform for validating microglia-targeted therapeutics for Alzheimer's disease

The scarcity of effective biomarkers and therapeutic strategies for predicting disease onset and progression in Alzheimers disease (AD) is a major challenge to improve much-needed therapeutic outcomes. Conventional drug discovery approaches have been unsuccessful in providing efficient interventions due to their one-size-fits-all nature. As an alternative, personalised drug development holds promise to pre-select responders and identify suitable drug efficacy indicators. In this study, we established a preclinical drug testing strategy by assessing the efficacy of anti-inflammatory drugs in 2D and 3D in vitro models of monocyte-derived microglia-like cells (MDMi) derived from AD and mild cognitive impairment (MCI) patients, and matched healthy individuals. We observed that the cytokine inflammatory profiles of MDMi in response to drugs clustered separately between cohorts, with the 3D model showing a more defined separation between healthy and patient donors than 2D. By ranking donor and cytokine responses to drugs, we identified that drug efficacy was limited in AD patients and involved cohort-specific responsive cytokines. Our findings suggest that MDMi models have the potential to predict disease progression, stratify responders and identify biomarkers for estimating the efficacy of microglia-targeted drugs. Together, our pipeline could serve as a valuable tool to enhance the clinical translational value of preclinical drug screens and ultimately improve drug outcomes for AD.

cell biology↗

bioRxiv2022

An Alzheimer's disease patient-derived olfactory cell model identifies gene expression changes associated with cognition

An early symptom of Alzheimers disease (AD) is an impaired sense of smell, for which the molecular basis remains elusive. Here, we generated human olfactory neurosphere-derived (ONS) cells from people with AD and mild cognitive impairment (MCI), and performed global RNA sequencing to determine gene expression changes. ONS cells expressed markers of neuroglial differentiation, providing a unique cellular model to explore early AD-associated disease pathways. Our transcriptomics data from ONS cells revealed differentially expressed genes (DEGs) associated with cognitive processes in AD cells compared to MCI, or matched healthy controls (HC). A-Kinase Anchoring Protein 6 (AKAP6) was the most significantly altered gene in AD compared to both MCI and HC, and has been linked to cognitive function. The greatest change in gene expression of all DEGs occurred between AD and MCI. Gene pathway analysis revealed defects in multiple cellular processes with aging, intellectual deficiency and alternative splicing being the most significantly dysregulated in AD ONS cells. Our results demonstrate that ONS cells can provide a cellular model for AD that recapitulates disease-associated differences. We have revealed potential novel genes, including AKAP6 that may have a role in AD, particularly MCI to AD transition, and should be further examined.

neuroscience↗

bioRxiv2021

3D models of Alzheimer's disease patient microglia recapitulate disease phenotype and show differential drug responses compared to 2D

Alzheimers disease (AD) is an incurable neurodegenerative disorder with a rapidly increasing prevalence worldwide. Current approaches targeting hallmark pathological features of AD have had no consistent clinical benefit. Neuroinflammation is a major contributor to neurodegeneration and hence, microglia, the brains resident immune cells, are an attractive target for potentially more effective therapeutic strategies. However, there is no current in vitro model system that faithfully recapitulates patient-specific microglial characteristics. To address this shortcoming, we developed novel 3D models of monocyte-derived microglia-like cells (MDMi) from AD patients. MDMi in 3D exhibited mature microglial features, including a highly branched morphology and enhanced bonafide microglial marker expression compared to 2D. Moreover, AD MDMi in 3D co-cultures with neuro-glial cells showed altered cell-to-cell interactions, growth factor and cytokine secretion profiles and responses to amyloid-{beta}. Drug screening assays in 3D AD MDMi revealed different cytokine responses compared to 2D. Our study demonstrates disease- and drug-specific responses in 3D MDMi models that are not apparent in 2D and presents a new 3D platform for more effective and personalised drug testing.

neuroscience↗

bioRxiv2020

ALS monocyte-derived microglia reveal cytoplasmic TDP-43 accumulation, DNA damage, and cell-specific impairment of phagocytosis associated with disease progression.

AimsAmyotrophic lateral sclerosis (ALS) is a multifactorial neurodegenerative disease characterised by the loss of upper and lower motor neurons. Neuroinflammation mediated by microglial activation is evident in post-mortem brain tissues, and in brain imaging of patients with ALS. However, the exact role of microglia in ALS remains to be elucidated partly due to the lack of an accurate microglial model system that is able to recapitulate the clinical pathology of ALS. Moreover, direct sampling of microglia from patients with ALS is not feasible, further limiting the study of microglial function in ALS. To address this shortcoming, we describe an approach that generates monocyte-derived microglia (MDMi) that are capable of expressing molecular markers, and functional characteristics similar to resident human brain microglia. Importantly, MDMi can be routinely and reproducibly generated from ALS patient blood, and reveal patient heterogeneity associated with age, sex and disease subgroup. MethodsMDMi were successfully established from all 30 ALS patients, including 15 patients with slow disease progression, 6 with intermediate progression, and 9 with rapid progression, together with 20 non-affected heathy controls (HC). ResultsOur ALS MDMi model recapitulated canonical pathological features of ALS including non-phosphorylated and phosphorylated-TDP-43-positive pathological inclusions. We further observed significantly impaired phagocytosis, altered cytokine expression and microglial morphology, as well as elevated DNA damage in ALS compared to HC MDMi. Abnormal phagocytosis was observed in all ALS cases, and was correlated to the progression of disease. Moreover, in-depth analysis of individual microglia revealed cell-specific variation in phagocytic function that was significantly altered, and exacerbated in rapid disease progression. ConclusionsOur approach enabled us to generate ALS patient microglia from peripheral blood samples using a rapid, robust, cost-effective, and reproducible protocol. We have shown that ALS monocyte-derived microglia have significantly altered functional behaviour compared to age-matched HCs, with a major deficit in phagocytic activity. This is also the first demonstration of abnormal TDP-43 localisation in microglia grown from ALS patients. Overall, this approach is highly applicable to monitor disease progression and can be applied as a functional readout in clinical trials for anti-neuroinflammatory agents. Additionally, this model system can be used as a basis for personalised therapeutic treatment for ALS, as well as other neurodegenerative diseases.

neuroscience↗