Biology subjects

Haraszti, T.

Publications and source records attributed to Haraszti, T..

4 recordsLinked to original sources

bioRxiv2025

Structural guidance in 3D microgel-in-hydrogel systems to improve chondrogenesis

Anisotropic biomaterials are broadly studied in regenerative medicine as they aim to mimic the hierarchical structures of native tissue. The Anisogel, an anisotropic microgel-in-hydrogel system, involves two key factors for tissue engineering: guidance cues - magnetically aligned rod-shape structures - and a surrounding matrix - polyethylene glycol-vinylsulfone (PEG-VS) with a degradable peptide crosslinker. This research shows the potential of using a PEG-VS-based Anisogel to allow for guided ingrowth and chondrogenic differentiation of human mesenchymal stromal cells (hMSCs) modulated by the alignment and size of anisometric microgels. The properties of the surrounding matrix are optimized for the availability of anchoring peptides (RGD concentration) and matrix density (hydrogel precursor concentration). The microgels of highest tested dimensions (10x10x100 {micro}m3) lead to a donor-independent significant upregulation of chondrogenic markers (SOX 9, ACAN and COL2AI) and a decrease of hypertrophic chondrogenic markers (RUNX 2), compared to unaligned and smaller microgel sizes. As a proof of concept, the Anisogel is tested in a semi-orthotopic mouse model where the effect of microgel alignment on cell infiltration and osteochondral tissue formation is evaluated.

bioengineering↗

bioRxiv2025

Fabrication of Short Polymeric μFibers as Building Blocks for Anisotropic High-Throughput Compatible 3D Tissue Models

Modeling the 3D microenvironment and cell growth of natively anisotropic human tissues in vitro constitutes a significant challenge in tissue engineering and biofabrication. Short polymeric fibers gain growing attention in this field due to their applicability as pipettable or injectable anisometric building blocks in 3D hydrogel-based cell culture systems or bioinks. However, the production of monodisperse short fibers with high production rates suitable for screening remains challenging. In this study, short, quasi-monodisperse, magneto-responsive, fluorescent poly({varepsilon}-caprolactone) {micro}fibers with variable dimensions in the micrometer range are produced in a scalable, semi-continuous two-step fabrication process combining controlled wet-dry spinning with subsequent cryosectioning. Influences of the spinning process parameters on fiber properties and process features, as well as boundary spinning conditions and upscaling potential, are explored using Design of Experiments approaches. Further, magnetic alignment of the {micro}fibers in a weak magnetic field and incorporation of nile red as fluorescent dye for facile analysis in 3D are demonstrated. Implementation of aligned {micro}fibers into a hydrogel-based 3D vasculogenesis model, produced in a high-throughput automated manner, is shown to stimulate oriented cell growth. This highlights the potential of our {micro}fibers as guiding elements inside tissue and disease models and their suitability for automated high-throughput applications.

bioengineering↗

bioRxiv2023

Laminin alpha 5 - induced mechanical homeostasis modulates retinal epithelium functionality

Epithelial cells are highly interconnected, whereby they acquire mesoscale mechanical properties to accomplish specific tissue functions. In homeostasis, this mechanical status can be summarised as mechanical homeostasis, regulated by the balance of intercellular tension and extracellular matrix adhesion forces. In the outer retina, the significance of this force balance and its consequences for vision remains poorly understood. We found that the density of basement membrane laminins modulates the level of retinal pigmented epithelium contractility, which directly controls its efficiency in phagocytosing photoreceptor outer segments. In vivo, the density gradient of laminins follows retinal functional demand, supporting the physiological role of laminins in controlling epithelial mechanical homeostasis. Our data suggest that laminin density and isoform heterogeneity can differentially engage integrins {beta}1 and {beta}4, the ratio of which determines the contribution of actin vs keratin cytoskeleton in balancing tissue mechanics. With this work, we suggest that the extracellular matrix-defined mechanical status of retinal pigmented epithelium is a novel parameter for visual function. SignificanceIn the retina, the retinal pigmented epithelium (RPE) is responsible for the daily phagocytosis of photoreceptor cell fragments, a process vital for visual function. Along the visual axis, there is a natural decrease in the ratio of photoreceptors to RPE cells, indicating a decrease in RPE functional demand. This study reveals that the density of laminins in RPE basement membrane also diminishes along this axis, critically influencing RPE function by regulating its contractility. For the first time, we demonstrate the presence of a laminin- defined mechanical gradient within the RPE, which determines its capacity to support photoreceptor cells. Our findings highlight the importance of mechanical properties as a key factor in visual function, offering new insights into retinal health and disease.

biophysics↗

bioRxiv2020

Substrate Resistance to Traction Forces Controls Fibroblast Polarization

The mechanics of fibronectin-rich extracellular matrix regulate cell physiology in a number of diseases, prompting efforts to elucidate cell mechanosensing mechanisms at the molecular and cellular scale. Here, the use of fibronectin-functionalized silicone elastomers that exhibit considerable frequency-dependence in viscoelastic properties unveiled the presence of two cellular processes that respond discreetly to substrate mechanical properties. Soft elastomers supported efficient focal adhesion maturation and fibroblast spreading due to an apparent stiff surface layer. However, soft elastomers did not enable cytoskeletal and fibroblast polarization; elastomers with high cross-linking and low deformability were required for polarization. The underlying reason for this behavior was the inability of soft elastomeric substrates to resist traction forces, rather than a lack of sufficient traction force generation; accordingly, mild inhibition of actomyosin contractility rescued fibroblast polarization even on the softer elastomers. Our findings help reconcile previously proposed local and global models of cell mechanosensing by demonstrating the differential dependence of substrate mechanics on distinct cellular processes. Statement of SignificanceThe mechanisms cells employ to sense and respond to the mechanical properties of their surroundings remain incompletely understood. In this study we used a commercial silicone elastomer formulation to prepare compliant, fibronectin-coated substrates and investigate the adhesion and polarization of human fibroblasts. Our results suggest the existence of at least two discrete mechanosensing processes regulated at different time and length (force) scales. Focal adhesion assembly and cell spreading were promoted by a stiff surface layer independent from bulk viscoelasticity, whereas effective cell polarization required elevated elastomer stiffness, sufficient to resist applied cell traction. The results presented here have implications on the use of elastomeric substrates as biomaterials for mechanosensing studies or clinical applications.

biophysics↗