Displaying publications 1 - 20 of 41 in total

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  1. Mok PL, Leong CF, Cheong SK
    Malays J Pathol, 2013 Jun;35(1):17-32.
    PMID: 23817392 MyJurnal
    Mesenchymal stem cells (MSC) are multipotent, self-renewing cells that can be found mainly in the bone marrow, and other post-natal organs and tissues. The ease of isolation and expansion, together with the immunomodulatory properties and their capability to migrate to sites of inflammation and tumours make them a suitable candidate for therapeutic use in the clinical settings. We review here the cellular mechanisms underlying the emerging applications of MSC in various fields.
  2. Mok PL, Cheong SK, Leong CF
    Malays J Pathol, 2008 Jun;30(1):11-9.
    PMID: 19108406 MyJurnal
    Mesenchymal stem cells are pluripotent progenitors that could be found in human bone marrow. Mesenchymal stem cells are capable of renewing themselves without differentiation in long-term culture. These cells also have low immunogenicity and can suppress alloreactive T cell responses. In the current study, mesenchymal stem cells isolated and propagated previously from the bone marrow of a megaloblastic anaemia patient were tested for their capabilities to differentiate into adipocytes, chondrocytes and osteoblasts in vitro. The differentiated cells were determined by Oil Red O, Alcian Blue-PAS and Alizarin Red S staining, and reverse transcriptase-polymerase chain reaction to determine the expression of mRNA specific for adipogenesis, chondrogenesis and osteogenesis. The results showed that the fibroblast-like cells were capable of differentiating into adipocytes, chondrocytes and osteoblasts upon chemical induction. The adipocytes, chondrocytes and osteoblasts were stained positively to Oil Red O, Alcian Blue-PAS and Alizarin Red S respectively. The differentiated cells were also found to express mRNA specific for adipogenesis ('peroxisome proliferation-activated receptor gamma2' and lipoprotein lipase), chondrogenesis (collagen type II) and osteogenesis (osteocalcin, osteopontin and alkaline phosphatase). In conclusion, this research has successfully isolated fibroblast-like cells from human bone marrow and these cells demonstrated morphological, cytochemical and immunochemical characteristics similar to mesenchymal stem cells. These cells maintain their proliferative properties and could be differentiated into the mesoderm lineage. The success of this study is vital because mesenchymal stem cells can be used in cellular therapy to regenerate or replace damaged tissues, or as a vehicle for therapeutic gene delivery in the future.
  3. Ding SLS, Kumar S, Mok PL
    Int J Mol Sci, 2017 Jul 28;18(8).
    PMID: 28788088 DOI: 10.3390/ijms18081406
    The use of multipotent mesenchymal stem cells (MSCs) has been reported as promising for the treatment of numerous degenerative disorders including the eye. In retinal degenerative diseases, MSCs exhibit the potential to regenerate into retinal neurons and retinal pigmented epithelial cells in both in vitro and in vivo studies. Delivery of MSCs was found to improve retinal morphology and function and delay retinal degeneration. In this review, we revisit the therapeutic role of MSCs in the diseased eye. Furthermore, we reveal the possible cellular mechanisms and identify the associated signaling pathways of MSCs in reversing the pathological conditions of various ocular disorders such as age-related macular degeneration (AMD), retinitis pigmentosa, diabetic retinopathy, and glaucoma. Current stem cell treatment can be dispensed as an independent cell treatment format or with the combination of other approaches. Hence, the improvement of the treatment strategy is largely subjected by our understanding of MSCs mechanism of action.
  4. Mok PL, Cheong SK, Leong CF, Chua KH, Ainoon O
    Tissue Cell, 2012 Aug;44(4):249-56.
    PMID: 22560724 DOI: 10.1016/j.tice.2012.04.002
    Mesenchymal stromal cells (MSC) are an attractive cell-targeting vehicle for gene delivery. MIDGE (an acronym for Minimalistic, Immunologically Defined Gene Expression) construct is relatively safer than the viral or plasmid expression system as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. The objective of this study was to test the ability of the human MSC (hMSC) to deliver the erythropoietin (EPO) gene in a nude mice model following nucleofection using a MIDGE construct. hMSC nucleofected with MIDGE encoding the EPO gene was injected subcutaneously in Matrigel at the dorsal flank of nude mice. Subcutaneous implantation of nucleofected hMSC resulted in increased hemoglobin level with presence of human EPO in the peripheral blood of the injected nude mice in the first two weeks post-implantation compared with the control groups. The basal layer of the hair shaft in the dermal layer was found to be significantly positive for immunohistochemical staining of a human EPO antibody. However, only a few basal layers of the hair shaft were found to be positively stained for CD105. In conclusion, hMSC harboring MIDGE-EPO could deliver and transiently express the EPO gene in the nude mice model. These cells could be localized to the hair follicle and secreted EPO protein might have possible role in hair regeneration.
  5. Mok PL, Cheong SK, Leong CF, Chua KH, Ainoon O
    Cytotechnology, 2012 Mar;64(2):203-16.
    PMID: 22160354 DOI: 10.1007/s10616-011-9413-2
    Human mesenchymal stromal cell (hMSC) is a potential target for cell and gene therapy-based approaches against a variety of different diseases. Whilst cationic lipofection has been widely experimented, the Nucleofector technology is a relatively new non-viral transfection method designed for primary cells and hard-to-transfect cell lines. Herein, we compared the efficiency and viability of nucleofection with cationic lipofection, and used the more efficient transfection method, nucleofection, to deliver a construct of minimalistic, immunologically defined gene expression encoding the erythropoietin (MIDGE-EPO) into hMSC. MIDGE construct is relatively safer than the viral and plasmid expression systems as the detrimental eukaryotic and prokaryotic gene and sequences have been eliminated. Using a plasmid encoding the luciferase gene, we demonstrated a high transfection efficiency using the U-23 (21.79 ± 1.09%) and C-17 (5.62 ± 1.09%) pulsing program in nucleofection. The cell viabilities were (44.93 ± 10.10)% and (21.93 ± 5.72)%, respectively 24 h post-nucleofection. On the other hand, lipofection treatment only yielded less than 0.6% efficiencies despite showing higher viabilities. Nucleofection did not affect hMSC renewability, immunophenotype and differentiation potentials. Subsequently, we nucleofected MIDGE-EPO using the U-23 pulsing program into hMSC. The results showed that, despite a low nucleofection efficiency with this construct, the EPO protein was stably expressed in the nucleofected cells up to 55 days when determined by ELISA or immunocytochemical staining. In conclusion, nucleofection is an efficient non-viral transfection approach for hMSC, which when used in conjunction with a MIDGE construct, could result in extended and stable transgene expression in hMSC.
  6. Mok PL, Cheong SK, Leong CF, Othman A
    Cytotherapy, 2008;10(2):116-24.
    PMID: 18368590 DOI: 10.1080/14653240701816996
    Mesenchymal stromal cells (MSC) are pluripotent progenitor cells that can be found in human bone marrow (BM). These cells have low immunogenicity and could suppress alloreactive T-cell responses. In the current study, MSC were tested for their capacity to carry and deliver the erythropoietin (EPO) gene in vitro.
  7. Choong PF, Mok PL, Cheong SK, Then KY
    Cytotherapy, 2007;9(3):252-8.
    PMID: 17464757
    The unique potential of mesenchymal stromal cells (MSC) has generated much research interest recently, particularly in exploring the regenerative nature of these cells. Previously, MSC were thought to be found only in the BM. However, further studies have shown that MSC can also be isolated from umbilical cord blood, adipose tissue and amniotic fluid. In this study, we explored the possibility of MSC residing in the cornea.
  8. Ali F, Taresh S, Al-Nuzaily M, Mok PL, Ismail A, Ahmad S
    Eur Rev Med Pharmacol Sci, 2016 Oct;20(20):4390-4400.
    PMID: 27831631
    Numerous lines of evidence support that bone marrow is a rich source of stem cells that can be used for research purposes and to treat some complex blood diseases and cancers. Stem cells are a potential source for regenerative medicine and tissue replacement after injury or disease, and mother cells that possess the capacity to become any type of cell in the body. They are cells without specific structure and characterized by their ability to self-renew or multiply while maintaining the potential to develop into other types of cells. Stem cells can normally become cells of the blood, heart, bones, skin, muscles or brain. Although, there are different sources of stem cells, all types of stem cells have the same capacity to develop into multiple types of cells. Stem cells are generally described as unspecialized cells with unlimited proliferation capacity that can divide (through mitosis) to produce more stem cells. Several types of adult stem cells have been characterized and can be cultured in vitro, including neural stem cells, hematopoietic stem cells, mesenchymal stem cells, cardiac stem cells and epithelial stem cells. They are valuable as research tools and might, in the future, be used to treat a wide range of diseases such as hematological hereditary diseases, Parkinson's disease, diabetes mellitus, heart disease and many other diseases. Currently, two types of stem cells have been identified based on their origins, namely embryonic stem cells and adult stem cells. Collectively, although many kinds of literature have been studying stem cell application in terms of clinical practice, stem cell-based therapy is still in its infancy stage.
  9. Munisvaradass R, Kumar S, Govindasamy C, Alnumair KS, Mok PL
    Int J Mol Sci, 2017 Sep 08;18(9).
    PMID: 28885562 DOI: 10.3390/ijms18091797
    Breast cancer is a common malignancy among women. The innate and adaptive immune responses failed to be activated owing to immune modulation in the tumour microenvironment. Decades of scientific study links the overexpression of human epidermal growth factor receptor 2 (ERBB2) antigen with aggressive tumours. The Chimeric Antigen Receptor (CAR) coding for specific tumour-associated antigens could initiate intrinsic T-cell signalling, inducing T-cell activation, and cytotoxic activity without the need for major histocompatibility complex recognition. This renders CAR as a potentially universal immunotherapeutic option. Herein, we aimed to establish CAR in CD3+ T-cells, isolated from human peripheral blood mononucleated cells that could subsequently target and induce apoptosis in the ERBB2 overexpressing human breast cancer cell line, SKBR3. Constructed CAR was inserted into a lentiviral plasmid containing a green fluorescent protein tag and produced as lentiviral particles that were used to transduce activated T-cells. Transduced CAR-T cells were then primed with SKBR3 cells to evaluate their functionality. Results showed increased apoptosis in SKBR3 cells co-cultured with CAR-T cells compared to the control (non-transduced T-cells). This study demonstrates that CAR introduction helps overcome the innate limitations of native T-cells leading to cancer cell apoptosis. We recommend future studies should focus on in vivo cytotoxicity of CAR-T cells against ERBB2 expressing tumours.
  10. Wong CY, Cheong SK, Mok PL, Leong CF
    Pathology, 2008 Jan;40(1):52-7.
    PMID: 18038316
    AIMS: Adult human bone marrow contains a population of mesenchymal stem cells (MSC) that contributes to the regeneration of tissues such as bone, cartilage, muscle, tendon, and fat. In recent years, it has been shown that functional stem cells exist in the adult bone marrow, and they can contribute to renal remodelling or reconstitution of injured renal glomeruli, especially mesangial cells. The purpose of this study is to examine the ability of MSC isolated from human bone marrow to differentiate into mesangial cells in glomerular injured athymic mice.

    METHODS: MSC were isolated from human bone marrow mononuclear cells based on plastic adherent properties and expanded in vitro in the culture medium. Human mesenchymal stem cells (hMSC) were characterised using microscopy, immunophenotyping, and their ability to differentiate into adipocytes, chondrocytes, and osteocytes. hMSC were then injected into athymic mice, which had induced glomerulonephropathy (GN).

    RESULTS: Test mice (induced GN and infused hMSC) were shown to have anti-human CD105(+) cells present in the kidneys and were also positive to anti-human desmin, a marker for mesangial cells. Furthermore, immunofluorescence assays also demonstrated that anti-human desmin(+) cells in the glomeruli of these test mice were in the proliferation stage, being positive to anti-human Ki-67.

    CONCLUSIONS: These findings indicate that hMSC found in renal glomeruli differentiated into mesangial cells in vivo after glomerular injury occurred.

  11. Choong PF, Mok PL, Cheong SK, Leong CF, Then KY
    Cytotherapy, 2007;9(2):170-83.
    PMID: 17453969
    The multipotency of stromal cells has been studied extensively. It has been reported that mesenchymal stromal cells (MSC) are capable of differentiating into cells of multilineage. Different methods and reagents have been used to induce the differentiation of MSC. We investigated the efficacy of different growth factors in inducing MSC differentiation into neurons.
  12. Khan MSA, Khundmiri SUK, Khundmiri SR, Al-Sanea MM, Mok PL
    Front Pharmacol, 2018;9:569.
    PMID: 29988459 DOI: 10.3389/fphar.2018.00569
    Ulceration in the stomach develops in peptic ulcer disease when there is a loss of protective mucosal layers, particularly in Helicobacter pylori infection. Antibiotic therapy has failed to eradicate and impede the colonization of H. pylori. Despite given treatment, recurrent bleeding can occur and lead to death in the affected individual. The disease progression is also related to the non-steroidal inflammatory drug and stress. There are extensive research efforts to identify the gastroprotective property from various alkaloids, flavonoids, and tannins compounds from plants and marine. These natural products are believed to be safe for consumption. However, not much attention was given to summarize the carbohydrate and terpenoidal anti-ulcer compounds. Hence, this review will cover the possible mechanisms and information about acidic hydroxylans, arabinogalactan and rhamnogalacturon; and limonene, pinene, lupeol, citral, ursolic acid and nomilin to exemplify on the gastroprotective properties of polysaccharides and terpenoid, respectively, obtained from fruits. These compounds could act as a prebiotic to prevent the inhabitation of H. pylori, modulate the inflammation, suppress gastric cancer growth, and capable of stimulating the reparative mechanisms on the affected regions. Finally, this review provides the future research prospects of these natural compounds in an effort to develop new therapy for gastrointestinal tissue healing.
  13. Mok PL, Koh AE, Farhana A, Alsrhani A, Alam MK, Suresh Kumar S
    Saudi J Biol Sci, 2021 Apr;28(4):2502-2509.
    PMID: 33551661 DOI: 10.1016/j.sjbs.2021.01.051
    COVID-19 is a rapidly emerging infectious disease caused by the SARS-CoV-2 virus currently spreading throughout the world. To date, there are no specific drugs formulated for it, and researchers around the globe are racing against the clock to investigate potential drug candidates. The repurposing of existing drugs in the market represents an effective and economical strategy commonly utilized in such investigations. In this study, we used a multiple-sequence alignment approach for preliminary screening of commercially-available drugs on SARS-CoV sequences from the Kingdom of Saudi Arabia (KSA) isolates. The viral genomic sequences from KSA isolates were obtained from GISAID, an open access repository housing a wide variety of epidemic and pandemic virus data. A phylogenetic analysis of the present 164 sequences from the KSA provinces was carried out using the MEGA X software, which displayed high similarity (around 98%). The sequence was then analyzed using the VIGOR4 genome annotator to construct its genomic structure. Screening of existing drugs was carried out by mining data based on viral gene expressions from the ZINC database. A total of 73 hits were generated. The viral target orthologs were mapped to the SARS-CoV-2 KSA isolate sequence by multiple sequence alignment using CLUSTAL OMEGA, and a list of 29 orthologs with purchasable drug information was generated. The results showed that the SARS CoV replicase polyprotein 1a had the highest sequence similarity at 79.91%. Through ZINC data mining, tanshinones were found to have high binding affinities to this target. These compounds could be ideal candidates for SARS-CoV-2. Other matches ranged between 27 and 52%. The results of this study would serve as a significant endeavor towards drug discovery that would increase our chances of finding an effective treatment or prevention against COVID19.
  14. Ding SSL, Subbiah SK, Khan MSA, Farhana A, Mok PL
    Int J Mol Sci, 2019 Apr 10;20(7).
    PMID: 30974904 DOI: 10.3390/ijms20071784
    Multipotent mesenchymal stem cells (MSCs) have been employed in numerous pre-clinical and clinical settings for various diseases. MSCs have been used in treating degenerative disorders pertaining to the eye, for example, age-related macular degeneration, glaucoma, retinitis pigmentosa, diabetic retinopathy, and optic neuritis. Despite the known therapeutic role and mechanisms of MSCs, low cell precision towards the targeted area and cell survivability at tissue needing repair often resulted in a disparity in therapeutic outcomes. In this review, we will discuss the current and feasible strategy options to enhance treatment outcomes with MSC therapy. We will review the application of various types of biomaterials and advances in nanotechnology, which have been employed on MSCs to augment cellular function and differentiation for improving treatment of visual functions. In addition, several modes of gene delivery into MSCs and the types of associated therapeutic genes that are important for modulation of ocular tissue function and repair will be highlighted.
  15. Ding SLS, Koh AE, Kumar S, Ali Khan MS, Alzahrani B, Mok PL
    PMID: 31060031 DOI: 10.1016/j.jphotobiol.2019.04.008
    Dysfunctional or death of retinal photoreceptors is an irreversible phenomenon that is closely associated with a broad range of retinal degenerative diseases, such as retinitis pigmentosa and age-related macular degeneration (AMD), resulting in successive loss of visual function and blindness. In search for viable treatment for retinal degenerative diseases, mesenchymal stem cells (MSCs) has demonstrated promising therapeutic capabilities to repair and replace damaged photoreceptor cells in both in vitro and in vivo conditions. Nevertheless, the dearth of MSC differentiation capacity into photoreceptors has limited its use in cell replacement therapy. Erythropoietin (EPO) has vital role in early neural retinal cell differentiation and demonstrated rescue potential on dying photoreceptor cells. Hence, we aimed to evaluate the differentiation capacity of MSCs into photoreceptor cells in the presence of human EPO protein. We derived the MSC from human Wharton's jelly of umbilical cord and transduced the cells with lentivirus particles encoding EPO and green fluorescent protein (GFP) as reporter gene. The transduced cells were selectively cultured and induced to differentiate into photoreceptors by exposing to photoreceptor differentiation cocktail. Our preliminary results showed that transduced cells exposed to induction medium had an enhanced differentiation capacity when compared to non-transduced cells. Our results demonstrated a novel strategy to increase the yield of in vitro photoreceptor differentiation and may be potentially useful in improving the efficiency of stem cell transplantation for ocular disorders.
  16. Alam MK, Alfawzan AA, Haque S, Mok PL, Marya A, Venugopal A, et al.
    Front Pediatr, 2021;9:651951.
    PMID: 34026687 DOI: 10.3389/fped.2021.651951
    To investigate whether the craniofacial sagittal jaw relationship in patients with non-syndromic cleft differed from non-cleft (NC) individuals by artificial intelligence (A.I.)-driven lateral cephalometric (Late. Ceph.) analysis. The study group comprised 123 subjects with different types of clefts including 29 = BCLP (bilateral cleft lip and palate), 41 = UCLP (unilateral cleft lip and palate), 9 = UCLA (unilateral cleft lip and alveolus), 13 = UCL (unilateral cleft lip) and NC = 31. The mean age was 14.77 years. SNA, SNB, ANB angle and Wits appraisal was measured in lateral cephalogram using a new innovative A.I driven Webceph software. Two-way ANOVA and multiple-comparison statistics tests were applied to see the differences between gender and among different types of clefts vs. NC individuals. A significant decrease (p < 0.005) in SNA, ANB, Wits appraisal was observed in different types of clefts vs. NC individuals. SNB (p > 0.005) showed insignificant variables in relation to type of clefts. No significant difference was also found in terms of gender in relation to any type of clefts and NC group. The present study advocates a decrease in sagittal development (SNA, ANB and Wits appraisal) in different types of cleft compared to NC individuals.
  17. Koh AE, Subbiah SK, Farhana A, Alam MK, Mok PL
    Front Cell Dev Biol, 2021;9:652065.
    PMID: 33937251 DOI: 10.3389/fcell.2021.652065
    Mesenchymal stem cells (MSC) have shown promise in restoring the vision of patients in clinical trials. However, this therapeutic effect is not observed in every treated patient and is possibly due to the inefficacies of cell delivery and high cell death following transplantation. Utilizing erythropoietin can significantly enhance the regenerative properties of MSCs and hence improve retinal neuron survivability in oxidative stress. Hence, this study aimed to investigate the efficacy of conditioned medium (CM) obtained from transgenic human erythropoietin-expressing MSCs (MSC EPO ) in protecting human retinal pigment epithelial cells from sodium iodate (NaIO3)-induced cell death. Human MSC and MSC EPO were first cultured to obtain conditioned media (CM). The IC50 of NaIO3 in the ARPE-19 culture was then determined by an MTT assay. After that, the efficacy of both MSC-CM and MSC-CM EPO in ARPE-19 cell survival were compared at 24 and 48 h after NaIO3 treatment with MTT. The treatment effects on mitochondrial membrane potential was then measured by a JC-1 flow cytometric assay. The MTT results indicated a corresponding increase in cell survivability (5-58%) in the ARPE-19 cell cultures. In comparison to MSC-CM, the use of conditioned medium collected from the MSC-CM EPO further enhanced the rate of ARPE-19 survivability at 24 h (P < 0.05) and 48 h (P < 0.05) in the presence of NaIO3. Furthermore, more than 90% were found viable with the JC-1 assay after MSC-CM EPO treatment, showing a positive implication on the mitochondrial dynamics of ARPE-19. The MSC-CM EPO provided an enhanced mitigating effect against NaIO3-induced ARPE-19 cell death over that of MSC-CM alone during the early phase of the treatment, and it may act as a future therapy in treating retinal degenerative diseases.
  18. Farhana A, Koh AE, Tong JB, Alsrhani A, Kumar Subbiah S, Mok PL
    Molecules, 2021 Sep 06;26(17).
    PMID: 34500845 DOI: 10.3390/molecules26175414
    Molecular crosstalk between the cellular epigenome and genome converge as a synergistic driver of oncogenic transformations. Besides other pathways, epigenetic regulatory circuits exert their effect towards cancer progression through the induction of DNA repair deficiencies. We explored this mechanism using a camptothecin encapsulated in β-cyclodextrin-EDTA-Fe3O4 nanoparticles (CPT-CEF)-treated HT29 cells model. We previously demonstrated that CPT-CEF treatment of HT29 cells effectively induces apoptosis and cell cycle arrest, stalling cancer progression. A comparative transcriptome analysis of CPT-CEF-treated versus untreated HT29 cells indicated that genes controlling mismatch repair, base excision repair, and homologues recombination were downregulated in these cancer cells. Our study demonstrated that treatment with CPT-CEF alleviated this repression. We observed that CPT-CEF exerts its effect by possibly affecting the DNA repair mechanism through epigenetic modulation involving genes of HMGB1, APEX1, and POLE3. Hence, we propose that CPT-CEF could be a DNA repair modulator that harnesses the cell's epigenomic plasticity to amend DNA repair deficiencies in cancer cells.
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