Biology subjects

Bellare, J.

Publications and source records attributed to Bellare, J..

6 recordsLinked to original sources

bioRxiv2026

Voltage-Gated Sodium Channel Modulation Differentially Alters ON and OFF Bipolar Cell Contributions to the Rat ERG

AimThe ERG b-wave is primarily attributed to ON bipolar cell activity, while the contribution of the OFF pathway and the differential role of voltage-gated sodium (NaV) channels in these pathways remain unclear. This study investigated whether pharmacological modulation of NaV channels differentially alters ON and OFF cone bipolar cell responses and ERG b-wave amplitudes. MethodsDark- and light-adapted ERGs were recorded from rats across stimulus intensities spanning rod, mixed rod-cone, and cone pathways (1-1000 lux). ON and OFF cone bipolar cell pathways were pharmacologically isolated using intravitreal cis-PDA. NaV channel activity was modulated via intravitreal administration of lidocaine and lamotrigine (blockers) and veratridine (agonist). Changes in b-wave amplitudes were analysed to assess pathway-specific effects. ResultsBoth lidocaine and lamotrigine significantly globally reduced ERG b-wave across all stimulus intensities, confirming a role for NaV channels in bipolar cell signalling. Pathway isolation revealed differential effects: lidocaine predominantly suppressed ON pathway, whereas lamotrigine preferentially reduced OFF pathway responses. In contrast, veratridine enhanced both ON and OFF pathway activity. These findings indicate that NaV channel activity in ON and OFF cone bipolar cells can be independently and differentially modulated. ConclusionThe ERG b-wave reflects integrated contributions from both ON and OFF cone bipolar cells. Differential NaV channel modulation alters these pathways distinctly, highlighting sodium channel-mediated mechanisms as potential targets for physiologically relevant retinal stimulation strategies in degenerative retinal conditions.

pharmacology and toxicology↗

bioRxiv2025

Collective Response of ON and OFF Bipolar Cells to Light Contributes to Improved Visual Acuity

In the visual signal relay, retinal bipolar cells transduce neurotransmitter signals from photoreceptor cells into electrical signals for onward transmission to the brain. The electrical activity of bipolar cells is reflected in the b-wave of the electroretinogram which is majorly contributed by ON bipolar cells leading to the currently accepted belief that light-induced signals travel through these cells only. Here, we probe the role of ON and OFF pathways to generate visual percept under the hypothesis that the ON Bipolar Cell fine image (central illumination) is superimposed onto a coarser image formed due to OFF Bipolar Cell (surround illumination). This improves image sharpness through edge detection by unsharp masking, thereby contributing to improved visual acuity. This new finding could be useful in stimulating the retina through sub-retinal implants to restore vision.

neuroscience↗

bioRxiv2022

Engineering Proprioceptive Implants via Surgical and Regenerative Approaches: Preliminary Interpretations

The periodontal ligaments are a group of specialized connective tissue fibres with vascular and neural elements that essentially attach a tooth to the alveolar bone. Endosseous dental implant replacing a lost tooth, gets ankylosed to the alveolar bone without intervening periodontal fibres (osseointegration). Hence, proprioception, one of the most important function of periodontal ligament is not elicited by commercial dental implants currently in use. To salvage the flaw, in our proof-of-principle trial in rabbits, biodegradable nanofibres were coiled around the additive manufactured (AM) customized titanium implants. Further, human dental pulp stem cells (DPSCs), adult mesenchymal stem cells of neuro-ectodermal origin, were seeded on the nanofibrous coated, orthotopically placed 3D-printed titanium implants and were induced to differentiate into neural cell lineages. The invivo anchoring mechanism of these biodegradable neuro-supportive scaffold coated implants could probably be "proprioceptive osseointegration" instead of defaults events leading to normal "osseointegration" and could exhibit features similar to periodontium, having possible anastomosis between the severed nerve terminals present in the wall of the extraction socket relaying to/from brain and newly differentiated neural cells present in the regenerated neo-tissue complex, gradually replacing the biodegradable scaffold and may eventually results in the development of proprioceptive osseointegrated root-form endosseous dental implants in near future.

bioengineering↗

bioRxiv2021

Ethanol pre-exposure enhances alcohol-seeking behavior at cellular level by chemoattraction and exhibits bleb-driven cellular stress response in uniform ethanol concentration

This study investigates the effect of ethanol and its pre-exposure on cell migration. Here, fibroblast cells were first pre-treated with ethanol, and their migratory behavior was tested in both chemotaxis and chemokinesis setup. 1% ethanol was taken as a potential chemotactic agent. The study reveals that in presence of ethanol gradient cells display migration towards ethanol, and pre-exposure further augments this migratory behavior by altering their chemotactic responsiveness. In uniform ethanol concentration, cells first undergo three staged adaptations to the new environment: shrinking, blebbing, and recovery, where cells use bleb-driven cell protection machinery to adapt. Thus, migration is initially stalled. But once the cells resume locomotion, no significant difference in migratory parameters is observed. Overall, this study establishes ethanol as a chemoattractant for fibroblasts, with cells showing enhanced alcohol-seeking behavior upon pre-exposure. Such behavior is reminiscent of seeking and tolerance exhibited by alcohol-dependent addictive behavior in higher organisms including humans.

cell biology↗

bioRxiv2019

\"Viscotaxis\" - Directed Migration of Mesenchymal Stem Cells in Response to Loss Modulus Gradient

Directed cell migration in response to chemical and mechanical gradients plays a crucial role in physiological and pathological conditions. One such mechanical cues that is known to influences cell migration is the gradient of substrate elastic modulus (E). However, the elastic modulus alone cannot fully define the material properties of the cellular microenvironment, which often has both elastic and viscous characteristics. In this study, we investigated the influence of the gradient of viscous nature, as defined by loss modulus, G\", on cell migration. We cultured human mesenchymal stem cells (hMSCs) on a collagen-coated polyacrylamide gel with constant elastic property, as defined by the storage modulus G, but with the gradient of loss modulus G\". We found hMSCs to migrate from high to low loss modulus. We have termed this, thus far unreported, directional cellular migration as \"Viscotaxis\". We have confirmed uniform collagen density and constant storage modulus of the gel by fluorescence microscopy and atomic force microscopy to eliminate the possibilities of haptotaxis and durotaxis. We hypothesize that material creep in the high loss modulus region hinders the building up of the cellular traction, leading to a force asymmetry that drives the observed viscotaxis. To verify our hypothesis, we estimated the cellular traction on gels with high and low loss moduli. We indeed found that cells apply higher traction force on more elastic materials i.e. materials with low loss modulus. On the disruption of actomyosin contractility with myosin inhibitor blebbistatin and ROCK inhibitor Y27632, directional migration was lost. Further, we showed that cells can maintain a stable morphology on a low loss modulus substrate but due to its inability to build up stable cellular traction on a substrate with high loss modulus, the cell spreading remains in a dynamic state. Our findings in this paper highlight the importance of considering the viscous modulus while preparing stiffness-based substrates for the field of tissue engineering.

biophysics↗

bioRxiv2018

Soft Substrate Maintains Proliferative and Multi-lineage Potential of Human Mesenchymal Stem Cells on Long Term Expansion

Human mesenchymal stem cells (hMSCs), when cultured on tissue culture plate (TCP) for in vitro expansion, they spontaneously lose their proliferative capacity and multi-lineage differentiation potential. They also lose their distinct spindle morphology and become large and flat. After a certain number of population doubling, they enter into permanent cell cycle arrest, called senescence. This is a major roadblock for clinical use of hMSCs which demands large number of cells. A cell culture system is needed which can maintain the stemness of hMSCs over long term passages yet simple to use. In this study, we explore the role of substrate rigidity in maintaining stemness. hMSCs were serially passaged on TCP and 5 kPa poly-acrylamide gel for 20 population doubling. It was found that while on TCP, cell growth reached a plateau at cumulative population doubling (CPD) = 12.5, on 5 kPa gel, they continue to proliferate linearly till we monitored (CPD = 20). We also found that while on TCP, late passage MSCs lost their adipogenic potential, the same was maintained on soft gel. Cell surface markers related to MSCs were also unaltered. We demonstrated that this maintenance of stemness was correlated with delay in onset of senescence, which was confirmed by {beta}-gal assay and by differential expression of vimentin, Lamin A and Lamin B. As preparation of poly-acrylamide gel is a simple, well established, and well standardized protocol, we believe that this system of cell expansion will be useful in therapeutic and research applications of hMSCs.\n\nOne Sentence SummaryhMSCs retain their stemness when expanded in vitro on soft polyacrylamide gel coated with collagen by delaying senescence.\n\nSignificance StatementFor clinical applications, mesenchymal stem cells (MSCs) are required in large numbers. As MSCs are available only in scarcity in vivo, to fulfill the need, extensive in vitro expansion is unavoidable. However, on expansion, they lose their replicative and multi-lineage differentiation potential and become senescent. A culture system that can maintain MSC stemness on long-term expansion, without compromising the stemness, is need of the hour. In this paper, we identified polyacrylamide (PAA) hydrogel of optimum stiffness that can be used to maintain stemness of MSCs during in vitro long term culture. Large quantity of MSCs thus grown can be used in regenerative medicine, cell therapy, and in treatment of inflammatory diseases.

bioengineering↗