Biology subjects

Van Vliet, K. J.

Publications and source records attributed to Van Vliet, K. J..

3 recordsLinked to original sources

bioRxiv2023

Myelin ensheathment and drug response of oligodendrocytes are modulated by stiffness of artificial axons

Myelination is a key biological process wherein glial cells such as oligodendrocytes wrap myelin around neuronal axons, forming an insulative sheath that accelerates signal propagation down the axon. A major obstacle to understanding myelination is the challenge of visualizing and reproducibly quantifying this inherently three-dimensional process in vitro. To this end, we previously developed Artificial Axons (AAs), a biocompatible platform consisting of 3D-printed hydrogel-based axon mimics designed to more closely recapitulate the micrometer-scale diameter and sub-kilopascal mechanical stiffness of biological axons. First, we present our platform for fabricating AAs with tunable axon diameter, stiffness, and inter-axonal spacing. Second, we demonstrate that increasing the Youngs modulus E or stiffness of polymer comprising the AAs increases the extent of myelin ensheathment by rat oligodendrocytes. Third, we demonstrate that the responses of oligodendrocytes to pro-myelinating compounds are also dependent on axon stiffness, which can affect compounds efficacy and the relative ranking. These results reinforce the importance of studying myelination in mechanically representative environments, and highlight the importance of considering biophysical cues when conducting drug screening studies.

neuroscience↗

bioRxiv2022

Topological defects govern mesenchymal condensations, offering a morphology-based tool to predict cartilage differentiation

A critical initial stage of skeletal morphogenesis involves formation of highly compact aggregates of mesenchymal cells, known as mesenchymal condensations, appearing as regularly-spaced pattern of spots. Conventional computational models to understand their patterning have been based on chemotaxis, haptotaxis, and reaction-diffusion equations. In this work, we investigate the mesenchymal condensations from a different perspective, namely topological defects within liquid crystal-like pattern. Using bone marrow-derived mesenchymal stromal cells (bm-MSCs), we observed emergence of cellular swirls in confluent in-vitro cultures, followed by appearance of mesenchymal condensations at the centers of the selfassembled swirls. Specifically, the condensations appeared at the comet-like (+1/2) and spiral-shaped (+1) topological defect sites within the swirl pattern. Next, with the rationale that cellular swirls precede skeletal morphogenesis, and supported with the qualitative observation that swirl pattern-features are donor-specific, we probed the correlation between swirl pattern and the chondrogenic differentiation outcome of bm-MSCs. Towards this, we first generated and imaged cellular swirls systematically across 5 donors by controlling seeding density, culture vessel geometry, and culture duration. We observed that the swirl pattern features quantified as variance of coherency correlated strongly with the cartilage matrix proteins, sulfated glycosaminoglycan and collagen-II, quantified from the standard in-vitro chondrogenic differentiation assay. Our work shows that swirl-pattern quantification provides a novel and powerful tool to predict efficacy of bm-MSCs for in-vitro cartilage regeneration. Significance StatementMesenchymal condensation is a critical stage in the formation of bone and cartilage, where the mesenchymal cells form high density cell clusters that are regularly spaced. In this work, we inspect the patterning of these condensations in-vitro from a novel perspective. We first show that at high density, bone-marrow-derived mesenchymal stromal cells (bm-MSCs) self-assemble to form cellular swirls resembling the vortices in a turbulent flow. This is followed by cell aggregations at the centers of the vortices, which show correspondence to mesenchymal condensations. Interestingly, we observed that the swirl pattern made by bm-MSCs isolated from human donors, varies from individual to individual and correlates with their propensity to differentiate into cartilage. This suggests that swirl pattern quantification via image analysis can be used to predict differentiation outcome, in context of regenerative cell therapy.

biophysics↗

bioRxiv2018

Acute but not inherited demyelination in mouse models leads to brain tissue stiffness changes

The alteration or decrease of axonal myelination is an important hallmark of aging and disease. Demyelinated axons are impaired in their function and degenerate over time. Oligodendrocytes, the cells responsible for myelination of axons, are sensitive to mechanical properties of their environment. Growing evidence indicates that mechanical properties of demyelinating lesions are different from the healthy state and thus have the potential to affect myelinating potential of oligodendrocytes. We performed a high-resolution spatial mapping of the mechanical heterogeneity of demyelinating lesions using Atomic Force Microscope enabled indentation. Our results indicate that the stiffness of specific regions of mouse brain tissue is influenced by age and degree of myelination. Here we specifically demonstrate that acute but not inherited demyelination leads to decreased tissue stiffness, which could lower remyelination potential of oligodendrocytes. We also demonstrate that specific brain regions have unique ranges of stiffness in white and grey matter. Our ex vivo findings may help the design of future in vitro models to mimic mechanical environment of the brain in healthy and disease state. Reported here, mechanical properties of demyelinating lesions may facilitate novel approaches in treating demyelinating diseases such as multiple sclerosis.

biophysics↗