Displaying publications 1 - 20 of 55 in total

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  1. Cheah PS, Thomas PQ
    Springerplus, 2015;4:400.
    PMID: 26261758 DOI: 10.1186/s40064-015-1194-1
    The cerebellum plays a vital role in equilibrium, motor control, and motor learning. The discrete neural and glial fates of cerebellar cells are determined by the molecular specifications (e.g. transcription factors) of neuroprogenitor cells that are influenced by local microenvironment signals. In this study, we evaluated the expression and function of Sox3, a single-exon gene located on the X chromosome, in the developing cerebellum.
  2. Lim CL, Ling KH, Cheah PS
    J Biol Methods, 2018;5(1):e87.
    PMID: 31453240 DOI: 10.14440/jbm.2018.219
    Satellite cells are myogenic cells responsible for muscle growth shortly after birth and muscle repair/regeneration during adulthood. Therapies based on satellite cells hold promise for treating muscular dysfunctions. Studying satellite cells is technically challenging owing to their low abundance, small size and anatomical dispersed location between the basal lamina and the sarcolemma of myofibers. In this article, we present three improved protocol strategies for studying the properties of satellite cells of the mouse during the different stages of muscle regeneration: (1) immunostaining of freshly isolated single myofibers to facilitate the study of quiescent satellite cells, (2) cultivation of single myofibers on Matrigel®-coated dish to study the myogenesis programs initiated by satellite cell activation, and (3) cultivation of single myofibers in floating conditions to analyze activated satellite cells or the doubling time of satellite cells in myofibers. In brief, when compared to previously published protocols, this article presented an improved protocol that requires shorter experimental time and less laborious approach for higher yield of intact single myofibers for downstream analyses.
  3. Bala U, Tan KL, Ling KH, Cheah PS
    BMC Res Notes, 2014;7:714.
    PMID: 25304607 DOI: 10.1186/1756-0500-7-714
    Over the past several decades, many studies concerning peripheral nerve damage or regeneration have been performed. Mice have been widely used for many of these studies, with the sciatic nerve being the most targeted and preferred nerve. Therefore, techniques for harvesting mouse sciatic nerves of a maximum length that is sufficient for different analyses will be highly valuable. Here we describe a simple step-by-step guide for harvesting the maximum length of mouse sciatic nerve and compare the length of the harvested nerves gathered with the proposed method with nerves obtained using a conventional mid-thigh incision approach.
  4. Muhammad AA, Arulselvan P, Cheah PS, Abas F, Fakurazi S
    Drug Des Devel Ther, 2016;10:1715-30.
    PMID: 27307703 DOI: 10.2147/DDDT.S96968
    Diabetic foot ulcer is a serious complication of diabetes, which affects a significant percentage (15%) of diabetics and up to 15%-24% of those affected may require amputation. Therefore, the economic burden of diabetic foot ulcers is enormous and is associated with high cost of treatment and prolongs hospitalization. The present study was conducted to evaluate antibacterial and in vivo wound healing activities of an aqueous fraction of Moringa oleifera on a diabetic condition. Antibacterial activity testing was carried out using agar well and tube dilution techniques. The in vivo study was conducted using six groups of animals that comprise of one normal and diabetic control group each, three treatment groups of 0.5%, 1%, and 2% w/w aqueous fraction, and a positive control group (1% w/w silver sulfadiazine). Rats were induced with diabetes using a combination of streptozotocin 65 and 150 mg/kg nicotinamide daily for 2 days, and excision wounds were created and treated with various doses (0.5%, 1%, and 2% w/w aqueous fraction) daily for 21 days. Biophysical, histological, and biochemical parameters were investigated. The results of the study revealed that aqueous fraction possessed antibacterial activity through inhibition of growth of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli organisms. The topical application of aqueous fraction revealed enhancement of wound healing under sustained hyperglycemic condition for the duration of the experiment. This enhancement was achieved through decreased wound size, improved wound contraction, and tissue regeneration, as well as downregulation of inflammatory mediators, such as tumor necrosis factor-α, interleukin-1β, interleukin-6, inducible nitric oxide synthase, and cyclooxygenase-2, and upregulation of an angiogenic marker vascular endothelial growth factor in wound tissue treated with various doses of aqueous fraction of M. oleifera. The findings suggest that aqueous fraction of M. oleifera containing Vicenin-2 active compound may accelerate wound healing in hyperglycemic condition.
  5. Damodaran T, Cheah PS, Murugaiyah V, Hassan Z
    Neurochem Int, 2020 10;139:104785.
    PMID: 32650028 DOI: 10.1016/j.neuint.2020.104785
    BACKGROUND: Clitoria ternatea (CT) is an herbal plant that has been used as a memory booster in folk medicine. CT root extract has been proven to restore chronic cerebral hypoperfusion (CCH)-induced memory deficits in a rat model, but the underlying mechanisms and the toxicity profile following repeated exposure have yet to be explored.

    THE AIM OF THE STUDY: To investigate the effects of the chronic (28 days) oral administration of CT root extract on CCH-induced cognitive impairment, neuronal damage and cholinergic deficit, and its toxicity profile in the CCH rat model.

    MATERIALS AND METHODS: The permanent bilateral occlusion of common carotid arteries (PBOCCA) surgery method was employed to develop a CCH model in male Sprague Dawley (SD) rats. Then, these rats were given oral administration of CT root extract at doses of 100, 200, and 300 mg/kg, respectively for 28 days and subjected to behavioural tests. At the end of the experiment, the brain was harvested for histological analysis and cholinesterase activities. Then, blood samples were collected and organs such as liver, kidney, lung, heart, and spleen were procured for toxicity assessment.

    RESULTS: Chronic treatment of CT root extract at doses of 200 and 300 mg/kg, restored memory impairments induced by CCH. CT root extract was also found to diminish CCH-induced neuronal damage in the CA1 region of the hippocampus. High dose (300 mg/kg) of the CT root extract was significantly inhibited the increased acetylcholinesterase (AChE) activity in the frontal cortex and hippocampus of the PBOCCA rats. In toxicity study, repeated doses of CT root extract were found to be safe in PBOCCA rats after 28 days of treatment.

    CONCLUSIONS: Our findings provided scientific evidence supporting the therapeutic potential of CT root extract in the treatment of vascular dementia (VaD)-related cholinergic abnormalities and subsequent cognitive decline.

  6. Tan KL, Lee HC, Cheah PS, Ling KH
    Neuroscience, 2023 Feb 10;511:1-12.
    PMID: 36496187 DOI: 10.1016/j.neuroscience.2022.12.003
    Mitochondrial dysfunctions have been described in Down syndrome (DS) caused by either partial or full trisomy of chromosome 21 (HSA21). Mitochondria play a crucial role in various vital functions in eukaryotic cells, especially in energy production, calcium homeostasis and programmed cell death. The function of mitochondria is primarily regulated by genes encoded in the mitochondrion and nucleus. Many genes on HSA21 are involved in oxidative phosphorylation (OXPHOS) and regulation of mitochondrial functions. This review highlights the HSA21 dosage-sensitive nuclear-encoded mitochondrial genes associated with overexpression-related phenotypes seen in DS. This includes impaired mitochondrial dynamics, structural defects and dysregulated bioenergetic profiles such as OXPHOS deficiency and reduced ATP production. Various therapeutic approaches for modulating energy deficits in DS, effects and molecular mechanism of gene therapy and drugs that exert protective effects through modulation of mitochondrial function and attenuation of oxidative stress in DS cells were discussed. It is prudent that improving DS pathophysiological conditions or quality of life may be feasible by targeting something as simple as cellular mitochondrial biogenesis and function.
  7. Huang T, Fakurazi S, Cheah PS, Ling KH
    Int J Mol Sci, 2023 Jun 10;24(12).
    PMID: 37373133 DOI: 10.3390/ijms24129980
    Down syndrome (DS) is the most frequently diagnosed chromosomal disorder of chromosome 21 (HSA21) aneuploidy, characterized by intellectual disability and reduced lifespan. The transcription repressor, Repressor Element-1 Silencing Transcription factor (REST), which acts as an epigenetic regulator, is a crucial regulator of neuronal and glial gene expression. In this study, we identified and investigated the role of REST-target genes in human brain tissues, cerebral organoids, and neural cells in Down syndrome. Gene expression datasets generated from healthy controls and DS samples of human brain tissues, cerebral organoids, NPC, neurons, and astrocytes were retrieved from the Gene Ontology (GEO) and Sequence Read Archive (SRA) databases. Differential expression analysis was performed on all datasets to produce differential expression genes (DEGs) between DS and control groups. REST-targeted DEGs were subjected to functional ontologies, pathways, and network analyses. We found that REST-targeted DEGs in DS were enriched for the JAK-STAT and HIF-1 signaling pathways across multiple distinct brain regions, ages, and neural cell types. We also identified REST-targeted DEGs involved in nervous system development, cell differentiation, fatty acid metabolism and inflammation in the DS brain. Based on the findings, we propose REST as the critical regulator and a promising therapeutic target to modulate homeostatic gene expression in the DS brain.
  8. Lee HC, Tan KL, Cheah PS, Ling KH
    Neural Plast, 2016;2016:7434191.
    PMID: 26881131 DOI: 10.1155/2016/7434191
    Trisomy of human chromosome 21 in Down syndrome (DS) leads to several phenotypes, such as mild-to-severe intellectual disability, hypotonia, and craniofacial dysmorphisms. These are fundamental hallmarks of the disorder that affect the quality of life of most individuals with DS. Proper brain development involves meticulous regulation of various signaling pathways, and dysregulation may result in abnormal neurodevelopment. DS brain is characterized by an increased number of astrocytes with reduced number of neurons. In mouse models for DS, the pool of neural progenitor cells commits to glia rather than neuronal cell fate in the DS brain. However, the mechanism(s) and consequences of this slight neurogenic-to-gliogenic shift in DS brain are still poorly understood. To date, Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling has been proposed to be crucial in various developmental pathways, especially in promoting astrogliogenesis. Since both human and mouse models of DS brain exhibit less neurons and a higher percentage of cells with astrocytic phenotypes, understanding the role of JAK-STAT signaling in DS brain development will provide novel insight into its role in the pathogenesis of DS brain and may serve as a potential target for the development of effective therapy to improve DS cognition.
  9. Leong JW, Abdullah S, Ling KH, Cheah PS
    Neural Plast, 2016;2016:1951250.
    PMID: 27034842 DOI: 10.1155/2016/1951250
    MicroRNAs (miRNAs) are small noncoding RNA known to regulate brain development. The expression of two novel miRNAs, namely, miR-344b and miR-344c, was characterized during mouse brain developmental stages in this study. In situ hybridization analysis showed that miR-344b and miR-344c were expressed in the germinal layer during embryonic brain developmental stages. In contrast, miR-344b was not detectable in the adult brain while miR-344c was expressed exclusively in the adult olfactory bulb and cerebellar granular layer. Stem-loop RT-qPCR analysis of whole brain RNAs showed that expression of the miR-344b and miR-344c was increased as brain developed throughout the embryonic stage and maintained at adulthood. Further investigation showed that these miRNAs were expressed in adult organs, where miR-344b and miR-344c were highly expressed in pancreas and brain, respectively. Bioinformatics analysis suggested miR-344b and miR-344c targeted Olig2 and Otx2 mRNAs, respectively. However, luciferase experiments demonstrated that these miRNAs did not target Olig2 and Otx2 mRNAs. Further investigation on the locality of miR-344b and miR-344c showed that both miRNAs were localized in nuclei of immature neurons. In conclusion, miR-344b and miR-344c were expressed spatiotemporally during mouse brain developmental stages.
  10. Lam XJ, Maniam S, Cheah PS, Ling KH
    Cell Mol Neurobiol, 2023 Oct;43(7):3417-3433.
    PMID: 37517069 DOI: 10.1007/s10571-023-01394-w
    Repressor element-1 silencing transcription factor (REST) or also known as neuron-restrictive silencing factor (NRSF), is the key initiator of epigenetic neuronal gene-expression modification. Identification of a massive number of REST-targeted genes in the brain signifies its broad involvement in maintaining the functionality of the nervous system. Additionally, REST plays a crucial role in conferring neuroprotection to the neurons against various stressors or insults during injuries. At the cellular level, nuclear localisation of REST is a key determinant for the functional transcriptional regulation of REST towards its target genes. Emerging studies reveal the implication of REST nuclear mislocalisation or dysregulation in several neurological diseases. The expression of REST varies depending on different types of neurological disorders, which has created challenges in the discovery of REST-targeted interventions. Hence, this review presents a comprehensive summary on the physiological roles of REST throughout brain development and its implications in neurodegenerative and neurodevelopmental disorders, brain tumours and cerebrovascular diseases. This review offers valuable insights to the development of potential therapeutic approaches targeting REST to improve pathologies in the brain. The important roles of REST as a key player in the nervous system development, and its implications in several neurological diseases.
  11. Huang T, Fakurazi S, Cheah PS, Ling KH
    Biochem Biophys Res Commun, 2024 Sep 04;735:150664.
    PMID: 39260337 DOI: 10.1016/j.bbrc.2024.150664
    In individuals with Down syndrome (DS), an additional HSA21 chromosome copy leads to the overexpression of a myriad of HSA21 genes, disrupting the transcription of the entire genome. This dysregulation in transcription and post-transcriptional modifications contributes to abnormal phenotypes across nearly all tissues and organs in DS individuals. The array of severe clinical symptoms associated with trisomy 21 poses a considerable challenge in the quest for a cure for DS. Fortunately, a wealth of research suggests that chromosome therapy, hinging on cutting-edge genome editing technologies, can potentially eliminate the extra copy of the human chromosome 21. Genome editing tools have demonstrated their efficacy in restoring trisomy to a normal diploid state in vitro DS cell models. Furthermore, we delve into the noteworthy findings in cellular therapy for DS, with recent studies showcasing the increasing feasibility of strategies involving stem cells and CAR T-cells to address corresponding clinical phenotypes.
  12. Siew WH, Tan KL, Babaei MA, Cheah PS, Ling KH
    PMID: 23596395 DOI: 10.3389/fncel.2013.00041
    Intellectual disability (ID) is one of the many features manifested in various genetic syndromes leading to deficits in cognitive function among affected individuals. ID is a feature affected by polygenes and multiple environmental factors. It leads to a broad spectrum of affected clinical and behavioral characteristics among patients. Until now, the causative mechanism of ID is unknown and the progression of the condition is poorly understood. Advancement in technology and research had identified various genetic abnormalities and defects as the potential cause of ID. However, the link between these abnormalities with ID is remained inconclusive and the roles of many newly discovered genetic components such as non-coding RNAs have not been thoroughly investigated. In this review, we aim to consolidate and assimilate the latest development and findings on a class of small non-coding RNAs known as microRNAs (miRNAs) involvement in ID development and progression with special focus on Down syndrome (DS) and X-linked ID (XLID) [including Fragile X syndrome (FXS)].
  13. Cheah PS, Norhani M, Bariah MA, Myint M, Lye MS, Azian AL
    Cornea, 2008 May;27(4):461-70.
    PMID: 18434851 DOI: 10.1097/ICO.0b013e318165642c
    To investigate the histological changes in primate cornea induced by short-term overnight orthokeratology (OK).
  14. Abidin SZ, Leong JW, Mahmoudi M, Nordin N, Abdullah S, Cheah PS, et al.
    Neurosci Bull, 2017 Aug;33(4):373-382.
    PMID: 28597341 DOI: 10.1007/s12264-017-0143-0
    MicroRNAs are small non-coding RNAs that play crucial roles in the regulation of gene expression and protein synthesis during brain development. MiR-3099 is highly expressed throughout embryogenesis, especially in the developing central nervous system. Moreover, miR-3099 is also expressed at a higher level in differentiating neurons in vitro, suggesting that it is a potential regulator during neuronal cell development. This study aimed to predict the target genes of miR-3099 via in-silico analysis using four independent prediction algorithms (miRDB, miRanda, TargetScan, and DIANA-micro-T-CDS) with emphasis on target genes related to brain development and function. Based on the analysis, a total of 3,174 miR-3099 target genes were predicted. Those predicted by at least three algorithms (324 genes) were subjected to DAVID bioinformatics analysis to understand their overall functional themes and representation. The analysis revealed that nearly 70% of the target genes were expressed in the nervous system and a significant proportion were associated with transcriptional regulation and protein ubiquitination mechanisms. Comparison of in situ hybridization (ISH) expression patterns of miR-3099 in both published and in-house-generated ISH sections with the ISH sections of target genes from the Allen Brain Atlas identified 7 target genes (Dnmt3a, Gabpa, Gfap, Itga4, Lxn, Smad7, and Tbx18) having expression patterns complementary to miR-3099 in the developing and adult mouse brain samples. Of these, we validated Gfap as a direct downstream target of miR-3099 using the luciferase reporter gene system. In conclusion, we report the successful prediction and validation of Gfap as an miR-3099 target gene using a combination of bioinformatics resources with enrichment of annotations based on functional ontologies and a spatio-temporal expression dataset.
  15. Zainal Abidin S, Fam SZ, Chong CE, Abdullah S, Cheah PS, Nordin N, et al.
    Gene, 2019 May 20;697:201-212.
    PMID: 30769142 DOI: 10.1016/j.gene.2019.02.014
    MicroRNA-3099 is highly expressed during neuronal differentiation and development of the central nervous system. Here we characterised the role of miR-3099 during neural differentiation and embryonic brain development using a stable and regulatable mouse embryonic stem cell culture system for miR-3099 expression and in utero electroporation of miR-3099 expression construct into E15.5 embryonic mouse brains. In the in vitro system, miR-3099 overexpression upregulated gene related to neuronal markers such as Tuj1, NeuN, Gat1, vGluT1 and vGluT2. In contrast, gene related to astrocyte markers (Gfap, S100β and Slc1a3) were suppressed upon overexpression of miR-3099. Furthermore, miR-3099 overexpression between E15.5 and E18.5 mouse embryonic brains led to disorganised neuronal migration potentially due to significantly decreased Gfap+ cells. Collectively, our results indicated that miR-3099 plays a role in modulating and regulating expression of key markers involved in neuronal differentiation. In silico analysis was also performed to identify miR-3099 homologues in the human genome, and candidates were validated by stem-loop RT-qPCR. Analysis of the miR-3099 seed sequence AGGCUA against human transcriptomes revealed that a potential miRNA, mds21 (Chr21:39186698-39186677) (GenBank accession ID: MK521584), was 100% identical to the miR-3099 seed sequence. Mds21 expression was observed and validated in various human cell lines (293FT, human Wharton's jelly and dental pulp mesenchymal stem cells, and MCF-7, MDA-MB-231, C-Sert, SW780, RT112, 5637, EJ28 and SH-SY5Y cells), with the highest levels detected in human mesenchymal stem cell lines. The analysis validated mds21 as a novel miRNA and a novel homologue of miR-3099 in the human genome.
  16. Prabhakar S, Lule S, da Hora CC, Breakefield XO, Cheah PS
    Exp Anim, 2021 Nov 10;70(4):450-458.
    PMID: 34039790 DOI: 10.1538/expanim.20-0186
    Adeno-associated virus (AAV)-based gene therapy is gaining popularity owing to its excellent safety profile and effective therapeutic outcomes in a number of diseases. Intravenous (IV) injection of AAV into the tail vein, facial vein and retro-orbital (RO) venous sinus have all been useful strategies to infuse the viral vector systemically. However, tail vein injection is technically challenging in juvenile mice, and injection at young ages (≤ postnatal day-(P)21) is essentially impossible. The temporal or facial vein is localized anterior to the ear bud and is markedly visible in the first couple of days postnatally. However, this method is age-dependent and requires a dissecting microscope. Retro-orbital injection (ROI), on the other hand, is suitable for all murine ages, including newborn and older mice, and is relatively less stressful to animals compared to tail vein injection. Although many reports have shown ROI as an effective route of AAV delivery, herein we aim to highlight and summarize the methods and benefits of ROI. To capture the full spectrum of transduction efficiency mediated by ROI, we transduced the editing-dependent reporter mice (Ai9 Cre reporter mice) with the AAV9 vector, which targets a wide range of peripheral tissues with exceptional brain tropism. We also provide a comprehensive description of the ROI technique to facilitate viral vector administration without complications.
  17. Lee KH, Ng YP, Cheah PS, Lim CK, Toh MS
    Br J Dermatol, 2017 Jan;176(1):159-167.
    PMID: 27363533 DOI: 10.1111/bjd.14832
    BACKGROUND: Glycation is a nonenzymatic reaction that cross-links a sugar molecule and protein macromolecule to form advanced glycation products (AGEs) that are associated with various age-related disorders; thus glycation plays an important role in skin chronological ageing.

    OBJECTIVES: To develop a novel in vitro skin glycation model as a screening tool for topical formulations with antiglycation properties and to further characterize, at the molecular level, the glycation stress-driven skin ageing mechanism.

    METHODS: The glycation model was developed using human reconstituted full-thickness skin; the presence of N(ε) -(carboxymethyl) lysine (CML) was used as evidence of the degree of glycation. Topical application of emulsion containing a well-known antiglycation compound (aminoguanidine) was used to verify the sensitivity and robustness of the model. Cytokine immunoassay, quantitative real-time polymerase chain reaction and histological analysis were further implemented to characterize the molecular mechanisms of skin ageing in the skin glycation model.

    RESULTS: Transcriptomic and cytokine profiling analyses in the skin glycation model demonstrated multiple biological changes, including extracellular matrix catabolism, skin barrier function impairment, oxidative stress and subsequently the inflammatory response. Darkness and yellowness of skin tone observed in the in vitro skin glycation model correlated well with the degree of glycation stress.

    CONCLUSIONS: The newly developed skin glycation model in this study has provided a new technological dimension in screening antiglycation properties of topical pharmaceutical or cosmeceutical formulations. This study concomitantly provides insights into skin ageing mechanisms driven by glycation stress, which could be useful in formulating skin antiageing therapy in future studies.

  18. Lam XJ, Xu B, Yeo PL, Cheah PS, Ling KH
    IBRO Neurosci Rep, 2023 Jun;14:407-418.
    PMID: 37388495 DOI: 10.1016/j.ibneur.2023.04.002
    Bipolar disorder (BD) is one of the major psychiatric diseases in which the impairment of mitochondrial functions has been closely connected or associated with the disease pathologies. Different lines of evidence of the close connection between mitochondria dysfunction and BD were discussed with a particular focus on (1) dysregulation of energy metabolism, (2) effect of genetic variants, (3) oxidative stress, cell death and apoptosis, (4) dysregulated calcium homeostasis and electrophysiology, and (5) current as well as potential treatments targeting at restoring mitochondrial functions. Currently, pharmacological interventions generally provide limited efficacy in preventing relapses or recovery from mania or depression episodes. Thus, understanding mitochondrial pathology in BD will lead to novel agents targeting mitochondrial dysfunction and formulating new effective therapy for BD.
  19. Azimzadeh M, Mohd Azmi MAN, Reisi P, Cheah PS, Ling KH
    MethodsX, 2024 Jun;12:102544.
    PMID: 38283759 DOI: 10.1016/j.mex.2023.102544
    In vivo extracellular field potential recording is a commonly used technique in modern neuroscience research. The success of long-term electrophysiological recordings often depends on the quality of the implantation surgery. However, there is limited use of visually guided stereotaxic neurosurgery and the application of the eLab/ePulse electrophysiology system in rodent models. This study presents a practical and functional manual guide for surgical electrode implantation in rodent models using the eLab/ePulse electrophysiology system for recording and stimulation purposes to assess neuronal functionality and synaptic plasticity. The evaluation parameters included the input/output function (IO), paired-pulse facilitation or depression (PPF/PPD), long-term potentiation (LTP), and long-term depression (LTD).•Provides a detailed picture-guided procedure for conducting in vivo stereotaxic neurosurgery.•Specifically covers the insertion of hippocampal electrodes and the recording of evoked extracellular field potentials.
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