Biology subjects

Chandiramohan, A.

Publications and source records attributed to Chandiramohan, A..

6 recordsLinked to original sources

bioRxiv2020

An Adhesive Based Fabrication Technique for Culture of Lung Airway Epithelial Cells with Applications in Microfluidics and Lung on a Chip

1This work describes a versatile and cost-effective cell culture method for growing adherent cells on a porous membrane using pressure-sensitive double-sided adhesives. This technique allows cell culture using conventional methods and easy transfer to microfluidic chip devices. To support the viability of our system, we evaluate the toxicity effect of four different adhesives on two distinct airway epithelial cell lines and show functional applications for microfluidic cell culture chip fabrication. We showed that cells could be grown and expanded on a "floating" membrane, which can be transferred upon cell confluency to a microfluidic chip for further analysis. The viability of cells and their inflammatory responses to IL-1{beta} stimulation was investigated. Such a technique would be useful to culture cells in a conventional fashion, which is more convenient and faster, and stimulate cells in an advanced model with perfusion when needed.

bioengineering↗

bioRxiv2020

PHAIR, A biosensor for pH measurement in air-liquid interface of human airway epithelial cells

1In many biological systems, pH can be used as a parameter to understand and study cell dynamics. However, measuring pH in live cell culture is limited by the sensor ion specificity, proximity to the cell surface, and scalability. Commercially available pH sensors are difficult to integrate into a small-scale cell culture system due to their size and are not cost-effective for disposable use. We made PHAIR - a new pH sensor that uses a micro-wire format to measure pH in vitro human airway cell culture. Tungsten micro-wires were used as the working electrodes, and silver micro-wires with a silver/silver chloride coating were used as a pseudo reference electrode. pH sensitivity, in a wide and narrow range, and stability of these sensors were tested in common standard buffer solutions as well as in culture media of human airway epithelial cells grown at the air-liquid interface in a 24 well cell culture plate. When measuring the pH of cells grown under basal and challenging conditions using PHAIR, cell viability and cytokine responses were not affected. Our results confirm that micro-wires-based sensors have the capacity for miniaturization, and detection of diverse ions while maintaining sensitivity. This suggests the broad application of PHAIR in various biological experimental settings.

bioengineering↗

bioRxiv2020

Surface modification of PDMS-based microfluidic devices with collagen using polydopamine as a spacer to enhance primary human bronchial epithelial cell adhesion

Polydimethylsiloxane (PDMS) is a silicone-based synthetic material that is used in various biomedical applications due to its properties, including transparency, flexibility, permeability to gases, and ease of use. Though PDMS facilitates and realizes the fabrication of complicated geometries at the micro and nano scales, it does not optimally interact with cells for adherence and proliferation. Different strategies have been proposed to render PDMS to enhance cell attachment. The majority of these surface modification techniques have been offered for a static cell culture system. However, dynamic cell culture systems such as organ-on-a-chip devices are demanding platforms that recapitulate the complexity of a living tissue microenvironment. For organ-on-a-chip platforms, PDMS surfaces are usually coated by ECM proteins, which occur as a result of physical, weak bonding between PDMS and ECM proteins, and this binding can be degraded when it is exposed to shear stresses. This work reports static and dynamic coating methods to covalently bind collagen within a PDMS-based microfluidic device using polydopamine (PDA). These coating methods were evaluated using water contact angle measurement and atomic force microscopy (AFM) to find the optimum coating conditions. The biocompatibility of collagen-coated PDMS devices was assessed by culturing primary human bronchial epithelial cells (HBECs) in microfluidic devices. It was shown that both PDA coating methods could be used to bind collagen, thereby improving cell adhesion (around three times higher) without showing any discernible difference. These results suggested that such a surface modification can be used to coat an extracellular matrix protein onto PDMS-based microfluidic devices.

bioengineering↗

bioRxiv2020

Development and validation of an open-source, disposable, 3D-printed in vitro environmental exposure system for Transwell culture inserts

Accessible in vitro models recapitulating the human airway that are amenable to study whole cannabis smoke exposure are needed for immunological and toxicological studies that inform public health policy and recreational cannabis use. In the present study, we developed and validated a novel 3D printed In Vitro Exposure System (IVES) that can be directly applied to study the effect of cannabis smoke exposure on primary human bronchial epithelial cells. Using commercially available design software and a 3D printer, we designed a four-chamber Transwell(R) insert holder for exposures to whole smoke. Software was used to model gas distribution, concentration gradients, velocity profile and shear stress within IVES. Following simulations, primary human bronchial epithelial cells cultured at air-liquid interface on Transwell(R) inserts were exposed to whole cannabis smoke. Following 24 hours, outcome measurements included cell morphology, epithelial barrier function, lactate dehydrogenase (LDH) levels, cytokine and gene expression. Whole smoke delivered through IVES possesses velocity profiles consistent with uniform gas distribution across the four chambers and complete mixing. Airflow velocity ranged between 1.0-1.5 m s-1 and generated low shear stresses (<< 1 Pa). Human airway epithelial cells exposed to cannabis smoke using IVES showed changes in cell morphology and disruption of barrier function without significant cytotoxicity. Cannabis smoke elevated IL-1 family cytokines and elevated CYP1A1 and CYP1B1 expression relative to control. IVES represents an accessible, open-source, exposure system that can be used to model varying types of cannabis smoke exposures with human airway epithelial cells grown under air-liquid interface culture conditions.

bioengineering↗

bioRxiv2020

Gene expression and in situ protein profiling of candidate SARS-CoV-2 receptors in human airway epithelial cells and lung tissue

In December 2019, SARS-CoV-2 emerged causing the COVID-19 pandemic. SARS-CoV, the agent responsible for the 2003 SARS outbreak, utilizes ACE2 and TMPRSS2 host molecules for viral entry. ACE2 and TMPRSS2 have recently been implicated in SARS-CoV-2 viral infection. Additional host molecules including ADAM17, cathepsin L, CD147, and GRP78 may also function as receptors for SARS-CoV-2. To determine the expression and in situ localization of candidate SARS-CoV-2 receptors in the respiratory mucosa, we analyzed gene expression datasets from airway epithelial cells of 515 healthy subjects, gene promoter activity analysis using the FANTOM5 dataset containing 120 distinct sample types, single cell RNA sequencing (scRNAseq) of 10 healthy subjects, immunoblots on multiple airway epithelial cell types, and immunohistochemistry on 98 human lung samples. We demonstrate absent to low ACE2 promoter activity in a variety of lung epithelial cell samples and low ACE2 gene expression in both microarray and scRNAseq datasets of epithelial cell populations. Consistent with gene expression, rare ACE2 protein expression was observed in the airway epithelium and alveoli of human lung. We present confirmatory evidence for the presence of TMPRSS2, CD147, and GRP78 protein in vitro in airway epithelial cells and confirm broad in situ protein expression of CD147 in the respiratory mucosa. Collectively, our data suggest the presence of a mechanism dynamically regulating ACE2 expression in human lung, perhaps in periods of SARS-CoV-2 infection, and also suggest that alternate receptors for SARS-CoV-2 exist to facilitate initial host cell infection.

immunology↗

bioRxiv2020

Expression of the endocannabinoid system in the human airway epithelial cells: Impact of sex and chronic respiratory disease status

Recreational and medicinal cannabis consumption in the past 12 months has been reported in 1/5th of Canadians, with greater use in males relative to females. Cannabis smoking is the dominant route of delivery in consumers, with the airway epithelium functioning as the site of first contact for inhaled phytocannabinoids. The endocannabinoid system is responsible for mediating the physiological effects of inhaled phytocannabinoids. Acute cannabis smoke inhalation can result in bronchodilation, which may have applications in chronic respiratory disease management. In contrast, chronic cannabis smoke inhalation is associated with reduced lung function and bronchitis, which challenges potential applications in the lung. The contribution of the endocannabinoid system in the airway epithelium to either beneficial or harmful physiological responses remains to be clearly defined in males and females and those with underlying chronic respiratory disease. To begin to address this knowledge gap, a curated dataset of 1090 unique human bronchial brushing gene expression profiles was created from Gene Expression Omnibus deposited microarray datasets. The dataset included 616 healthy subjects, 136 subjects with asthma, and 338 subjects with COPD. A 27-gene endocannabinoid signature was analyzed across all samples with sex and disease specific-analyses performed. Immunohistochemistry and immunoblots were performed to confirm in situ and in vitro protein expression of select genes in human airway epithelial cells. We confirm three receptors for cannabinoids, CB1, CB2, and TRPV1, are expressed at the protein level in human airway epithelial cells in situ and in vitro, justifying examining the downstream endocannabinoid pathway more extensively at the gene expression level. Sex status was associated with differential expression of 6/27 genes. In contrast, disease status was associated with differential expression of 18/27 genes in asthmatics and 22/27 genes in COPD subjects. We confirm at the protein level that TRPV1, the most differentially expressed candidate in our analyses, was up-regulated in airway epithelial cells from asthmatics relative to healthy subjects. Our data demonstrate that endocannabinoid system is expressed in human airway epithelial cells with expression impacted by disease status and minimally by sex. The data suggest that cannabis consumers may have differential physiological responses in the respiratory mucosa, which could impact both acute and chronic effects of cannabis smoke inhalation.

cell biology↗