Publications by authors named "Meysam Abbasi"

8 Publications

  • Page 1 of 1

Incidence of symptomatic venous thromboembolism following hospitalization for coronavirus disease 2019: Prospective results from a multi-center study.

Thromb Res 2021 02 11;198:135-138. Epub 2020 Dec 11.

Tuberculosis and Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.

Background: Thrombosis and pulmonary embolism appear to be major causes of mortality in hospitalized coronavirus disease 2019 (COVID-19) patients. However, few studies have focused on the incidence of venous thromboembolism (VTE) after hospitalization for COVID-19.

Methods: In this multi-center study, we followed 1529 COVID-19 patients for at least 45 days after hospital discharge, who underwent routine telephone follow-up. In case of signs or symptoms of pulmonary embolism (PE) or deep vein thrombosis (DVT), they were invited for an in-hospital visit with a pulmonologist. The primary outcome was symptomatic VTE within 45 days of hospital discharge.

Results: Of 1529 COVID-19 patients discharged from hospital, a total of 228 (14.9%) reported potential signs or symptoms of PE or DVT and were seen for an in-hospital visit. Of these, 13 and 12 received Doppler ultrasounds or pulmonary CT angiography, respectively, of whom only one patient was diagnosed with symptomatic PE. Of 51 (3.3%) patients who died after discharge, two deaths were attributed to VTE corresponding to a 45-day cumulative rate of symptomatic VTE of 0.2% (95%CI 0.1%-0.6%; n = 3). There was no evidence of acute respiratory distress syndrome (ARDS) in these patients. Other deaths after hospital discharge included myocardial infarction (n = 13), heart failure (n = 9), and stroke (n = 9).

Conclusions: We did not observe a high rate of symptomatic VTE in COVID-19 patients after hospital discharge. Routine extended thromboprophylaxis after hospitalization for COVID-19 may not have a net clinical benefit. Randomized trials may be warranted.
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February 2021

The Ultimate qPCR Experiment: Producing Publication Quality, Reproducible Data the First Time.

Trends Biotechnol 2019 07 14;37(7):761-774. Epub 2019 Jan 14.

Bio-Rad Laboratories, 255 Linus Pauling Drive, Hercules, CA 94547, USA.

Quantitative PCR (qPCR) is one of the most common techniques for quantification of nucleic acid molecules in biological and environmental samples. Although the methodology is perceived to be relatively simple, there are a number of steps and reagents that require optimization and validation to ensure reproducible data that accurately reflect the biological question(s) being posed. This review article describes and illustrates the critical pitfalls and sources of error in qPCR experiments, along with a rigorous, stepwise process to minimize variability, time, and cost in generating reproducible, publication quality data every time. Finally, an approach to make an informed choice between qPCR and digital PCR technologies is described.
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July 2019

A comparison between droplet digital and quantitative PCR in the analysis of bacterial 16S load in lung tissue samples from control and COPD GOLD 2.

PLoS One 2014 16;9(10):e110351. Epub 2014 Oct 16.

Centre for Heart Lung Innovation, St. Paul's Hospital, Departments of Medicine and Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, Canada.

Background: Low biomass in the bacterial lung tissue microbiome utilizes quantitative PCR (qPCR) 16S bacterial assays at their limit of detection. New technology like droplet digital PCR (ddPCR) could allow for higher sensitivity and accuracy of quantification. These attributes are needed if specific bacteria within the bacterial lung tissue microbiome are to be evaluated as potential contributors to diseases such as chronic obstructive pulmonary disease (COPD). We hypothesize that ddPCR is better at quantifying the total bacterial load in lung tissue versus qPCR.

Methods: Control (n = 16) and COPD GOLD 2 (n = 16) tissue samples were obtained from patients who underwent lung resection surgery, were cut on a cryotome, and sections were assigned for use in quantitative histology or for DNA extraction. qPCR and ddPCR were performed on these samples using primers spanning the V2 region on the 16S rRNA gene along with negative controls. Total 16S counts were compared between the two methods. Both methods were assessed for correlations with quantitative histology measurements of the tissue.

Results: There was no difference in the average total 16S counts (P>0.05) between the two methods. However, the negative controls contained significantly lower counts in the ddPCR (0.55 ± 0.28 16S/uL) than in the qPCR assay (1.00 ± 0.70 16S copies) (P <0.05). The coefficient of variation was significantly lower for the ddPCR assay (0.18 ± 0.14) versus the qPCR assay (0.62 ± 0.29) (P<0.05).

Conclusion: Overall the ddPCR 16S assay performed better by reducing the background noise in 16S of the negative controls compared with 16S qPCR assay.
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December 2015

siRNA-mediated down-regulation of P-glycoprotein in a Xenograft tumor model in NOD-SCID mice.

Pharm Res 2011 Oct 3;28(10):2516-29. Epub 2011 Jun 3.

Department of Biomedical Engineering, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada.

Purpose: The efficacy of chemotherapy is decreased due to over-expression of the drug transporter P-glycoprotein (P-gp). This study was conducted to determine the feasibility of down-regulating tumor P-gp levels with non-viral siRNA delivery in order to sensitize the tumors to drug therapy.

Methods: P-gp over-expressing MDA435/LCC6 MDR1 cells were used to establish xenografts in NOD-SCID mouse. Cationic polymers polyethylenimine (PEI) and stearic acid-substituted poly-L-lysine (PLL-StA) were formulated with P-gp- specific siRNAs and delivered intratumorally to explore the feasibility of P-gp down-regulation in tumors. Intravenous Doxil™ was administered to investigate tumor growth.

Results: PEI and PLL-StA effectively delivered siRNA to MDA435/LCC6 MDR1 cells in vitro to reduce P-gp expression for 3 days. Intratumoral injection of siRNA with the carriers resulted in 60-80% and 20-32% of siRNA retention in tumors after 24 and 96 hr, respectively. This led to ~29.0% and ~61.5% P-gp down-regulation with PEI- and PLL-StA-mediated siRNA delivery, respectively. The P-gp down-regulation by intratumoral siRNA injection led to better response to systemic Doxil™ treatment, resulting in slowed tumor growth in originally doxorubicin-resistant tumors.

Conclusion: Effective P-gp down-regulation was feasible with polymeric siRNA delivery in a xenograft model, resulting in an enhanced response to the drug therapy.
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October 2011

Recent attempts at RNAi-mediated P-glycoprotein downregulation for reversal of multidrug resistance in cancer.

Med Res Rev 2013 Jan 26;33(1):33-53. Epub 2011 Apr 26.

Department of Biomedical Engineering, Faculty of Medicine, University of Alberta, Edmonton, Canada.

Multidrug resistance (MDR) is among the major mechanisms leading to failure in chemotherapy of cancer patients. The ATP-binding cassette proteins are major contributors to MDR, involved in the active efflux of xenobiotics out of cancer cells. Among them, P-glycoprotein (P-gp) is the most dominant protein involved in the efflux of drugs. For more than 30 years, scientists have searched for the ideal P-gp inhibitor to modulate drug resistance activity of P-gp. This inhibitor should be tissue and cell specific with side effects on other tissues, must not provoke immune responses from the host, should provide sustained inhibition, and must be synthesized readily with low cost. Chemical P-gp inhibitors tested to date, have shown nonspecific toxic effects limiting their clinical applications. Sequence-specific P-gp gene silencing by RNA interference (RNAi) may provide a more effective approach for downregulation of specific protein targets due to high specificity, limited toxicity and immunogenicity, and relative ease in synthesis. RNAi can be implemented by delivery of synthetic small interfering RNAs (siRNAs) or by gene expression of short hairpin RNAs using gene expressing vectors. Specific delivery systems and expression vectors have been designed for this purpose and many researchers have explored their effectiveness for P-gp downregulation. In this report, we review the efficiency of various methods for siRNA delivery and transfection for P-gp downregulation in cancer cells for MDR reversal. Novel ideas and observations by different research groups were discussed for future improvement in this essential field.
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January 2013

Cationic polymer-mediated small interfering RNA delivery for P-glycoprotein down-regulation in tumor cells.

Cancer 2010 Dec 16;116(23):5544-54. Epub 2010 Aug 16.

Department of Biomedical Engineering, Faculty of Medicine, Cross Cancer Institute, Edmonton, Alberta, Canada.

Background: Among the treatment options that have been developed for cancer, chemotherapy remains 1 of the leading clinical approaches. Chemotherapy can usually control tumor growth at the onset of disease, but its effectiveness becomes limited by the overexpression of transporter proteins responsible for drug efflux, leading to multidrug resistance (MDR). To overcome this obstacle, the authors explored the feasibility of down-regulating the main drug transporter, P-glycoprotein (P-gp), by using nonviral small interfering RNA (siRNA) delivery as means to enhance the accumulation of chemotherapeutic agents in drug-resistant cancer cells.

Methods: Several cationic carriers capable of siRNA complexation were investigated for P-gp down-regulation in the MDA435/LCC6 cell line and, consequently, increased cellular uptake of the chemotherapeutic agents doxorubicin and paclitaxel.

Results: Efficient siRNA delivery into tumor cells was demonstrated particularly using a palmitic-acid substituted poly(L-lysine), with no apparent differences in siRNA delivery between the wild type (WT)-expressing and P-gp-expressing phenotype (MDR1) of the cells. Efficient siRNA delivery led to approximately 40% to 50% P-gp suppression (based on the average expression level of the protein), an approximately 3-fold increased DOX uptake, and increased cytotoxicity in MDR1 cells.

Conclusions: The authors concluded that effective siRNA delivery with nonviral carriers can reduce the level of P-gp on cell surfaces and enhance the efficiency of chemotherapeutic agents in vitro.
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December 2010

Further investigation of lipid-substituted poly(L-Lysine) polymers for transfection of human skin fibroblasts.

Biomacromolecules 2008 Jun 23;9(6):1618-30. Epub 2008 May 23.

Department of Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.

Enabling gene expression in skin fibroblasts using safe, nonviral gene delivery has the potential to stimulate wound healing and aid in skin tissue engineering efforts. In this study, several lipid-substituted poly(L-Lysines) (PLL) were investigated for their ability to deliver a plasmid DNA (pEGFP) to human skin fibroblasts. While native and lipid-substituted PLLs showed complete complexation with pEGFP, polymers with higher lipid substitution were more resilient to dissociation after heparin treatment. All polymers showed good protection of pEGFP against DNase I and DNase II digestion in vitro. DNA delivery studies using fluorescently labeled pEGFP showed that native PLL lacked the ability to deliver pEGFP into cells, whereas most of the lipid-substituted PLLs gave efficient pEGFP delivery into the cells. Extent of lipid substitution was an important factor in DNA delivery efficiency. The intracellular pEGFP was intact after delivery with lipid-substituted polymers up to 7 days. An RT-PCR methodology indicated successful transcription of the reporter GFP gene, which was not the case when the cells were transfected with a blank plasmid containing no functional GFP gene. Further studies with flow cytometry showed that successful protein expression was obtained with PLLs substituted with myristic and stearic acid, the latter displaying a relatively lower toxicity. We conclude that substituting lipids on PLL results in effective gene carriers and the extent of substitution, rather than the individual lipid, appeared to be critical for effective plasmid delivery.
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June 2008

Palmitic acid-modified poly-L-lysine for non-viral delivery of plasmid DNA to skin fibroblasts.

Biomacromolecules 2007 Apr 3;8(4):1059-63. Epub 2007 Mar 3.

Department of Biomedical Engineering, University of Alberta, Edmonton, AB, Canada.

Palmitic acid conjugates of poly-L-lysine (PLL-PA) were prepared, and their ability to deliver plasmid DNA into human skin fibroblasts was evaluated in vitro. The conjugates were capable of condensing a 4.7 kb plasmid DNA into 50-200 nm particles (mean +/- SD = 112 +/- 34 nm), which were slightly smaller than the particles formed by PLL (mean +/- SD = 126 +/- 51 nm). Both PLL and PLL-PA were readily taken up by the cells, but PLL-PA delivered the plasmid DNA into a higher proportion of cells. DNA delivery was found to be reduced by endocytosis inhibitor Brefeldin A, suggesting an active mechanism of particle uptake. Using enhanced green fluorescent protein (EGFP) as a reporter gene, PLL-PA was found to give the highest number of EGFP-positive cells among several carriers tested, including polyethyleneimine, Lipofectamine-2000, and an adenovirus. Although some carriers gave a higher percentage of EGFP-positive cells than PLL-PA, they were also associated with higher toxicities. We conclude that PLL-PA is a promising gene carrier for non-viral modification of human fibroblasts.
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April 2007