Biology subjects

Grad, S.

Publications and source records attributed to Grad, S..

4 recordsLinked to original sources

bioRxiv2026

Restoring the Chondron: Pericellular Matrix Reconstitution Enhances Mechano-Inflammatory Resilience and Modulates Chondrocyte-Neuron Crosstalk

Abstract Chondrocytes in native articular cartilage are enclosed within a collagen VI (COL VI)-rich pericellular matrix (PCM), forming functional units known as chondrons. However, enzymatic isolation disrupts the PCM, and the functional consequences of its loss and restoration remain poorly understood. In this study, primary human chondrocytes were cultured in alginate beads to promote PCM reconstitution and subsequently recovered as reconstituted chondrons. Chondrocytes and reconstituted chondrons were encapsulated in gelatin methacryloyl hydrogels and compared under inflammatory and mechanical stimulation. Alginate preconditioning generated chondron-like units with a distinct COL VI-positive PCM that was retained after transfer to three-dimensional culture. Under inflammatory conditions, reconstituted chondrons exhibited reduced inflammatory, catabolic, neuroinflammatory, and angiogenic responses compared with isolated chondrocytes at both gene and protein levels. Under interleukin-1{beta} stimulation, mechanical loading further increased inflammatory gene expression in chondrocytes in a donor-dependent manner, whereas responses remained comparatively limited in reconstituted chondrons. Conditioned medium from reconstituted chondrons was also associated with lower capsaicin- and potassium chloride-evoked calcium responses in human induced pluripotent stem cell-derived sensory neurons than corresponding chondrocyte-conditioned medium. These findings demonstrate that reconstitution of a COL VI-rich PCM restores a chondron-like pericellular microenvironment that attenuates inflammatory activation and buffers load-associated inflammatory amplification, while exploratory sensory neuron experiments suggest downstream modulation of neuronal responsiveness. PCM restoration may therefore provide a promising strategy for cartilage tissue engineering and regenerative applications.

molecular biology↗

bioRxiv2026

Toward Standardized Ex Vivo Joint Models: Impact of Glucose and Oxygen Levels for Enhanced Tissue Maintenance

Ex vivo models bridge in vitro and in vivo systems by preserving native extracellular matrix architecture and multicellular interactions. In articular joint research, osteochondral-synovial co-cultures are particularly valuable for studying bone-cartilage crosstalk and synovial inflammatory regulation. However, a lack of standardized culture conditions regarding glucose and oxygen, two key regulators of cellular metabolism, limits reproducibility and translational relevance. This study aims to define how glucose and oxygen conditions influence joint tissues maintenance in an ex vivo model. Bovine osteochondral explants and synovium are harvested from the stifle joint and co-cultured using either high glucose DMEM (HG, 4.5 g/L) or low glucose DMEM (LG, 1 g/L) under hyperoxic (21% O2) or physioxic (5% O2) conditions. Cell viability, gene expression, and metabolomic profiles are evaluated across tissues. LG conditions increase cell death in the deep zone of cartilage and in subchondral bone. Gene expression and metabolomic analyses reveal tissue-specific effects of glucose and oxygen. In cartilage and bone, glucose-dependent gene regulation and metabolic changes occur under hyperoxia but are largely absent under physioxia, indicating buffering of glucose responses. Gene-specific sensitivity to glucose and oxygen is observed in bone and synovium; however, glucose-induced metabolic responses persist under physioxia only in synovium. Overall, these findings identify oxygen and glucose as critical modulators of joint tissue physiology and support the use of HG, physioxic culture conditions to improve cell viability and stabilize molecular outcomes in ex vivo joint models. This optimized ex vivo model provides platforms for investigating mechanisms relevant to joint-related diseases. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/704322v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1393324org.highwire.dtl.DTLVardef@4c9393org.highwire.dtl.DTLVardef@16cc00eorg.highwire.dtl.DTLVardef@b4d9ea_HPS_FORMAT_FIGEXP M_FIG C_FIG This study evaluates the effects of glucose concentration and oxygen tension in an ex vivo joint co-culture system to define optimal culture conditions. High glucose medium and physioxic conditions support tissue viability, preserve homeostasis, and enhance the physiological relevance of the ex vivo model.

cell biology↗

bioRxiv2023

Engineering sensory ganglion multicellular system to model tissue nerve ingrowth

Discogenic pain is associated with deep nerve ingrowth in annulus fibrosus tissue (AF) of intervertebral disc (IVD). To model AF nerve ingrowth, primary bovine dorsal root ganglion (DRG) micro-scale tissue units are spatially organized around an AF explant by mild hydrodynamic forces within a collagen matrix. This results in a densely packed multicellular system mimicking the native DRG tissue morphology and a controlled AF-neuron distance. Such a multicellular organization is essential to evolve populational-level cellular functions and in vivo-like morphologies. Pro-inflammatory cytokine-primed AF demonstrates its neurotrophic and neurotropic effects on nociceptor axons. Both effects depend on the AF-neuron distance underpinning the role of recapitulating inter-tissue/organ anatomical proximity when investigating their crosstalk. This is the first in vitro model studying AF nerve ingrowth by engineering mature and large animal tissues in a morphologically and physiologically relevant environment. Our new approach can be used to biofabricate multi-tissue/organ models for untangling pathophysiological conditions and develop novel therapies.

bioengineering↗

bioRxiv2021

Biofabrication of development-inspired scaffolds for regeneration of the annulus fibrosus macro- and microarchitecture

Annulus fibrosus (AF) tissue engineering is a promising strategy for repairing the degenerated intervertebral disc (IVD) and a research area that could benefit from improved tissue models to drive translation. AF tissue is composed of concentric layers of aligned collagen bundles arranged in an angle-ply pattern, an architecture which is challenging to recapitulate with current scaffold design strategies. In response to this need, we developed a strategy to print 3D scaffolds that induce cell and tissue organization into oriented patterns mimicking the AF. Polycaprolactone (PCL) was printed in an angle-ply macroarchitecture possessing microscale aligned topographical cues. The topography was achieved by extrusion through custom-designed printer nozzles which were either round or possessing circumferential sinusoidal peaks. Whereas the round nozzle produced extruded filaments with a slight uniaxial texture, patterned nozzles with peak heights of 60 or 120 m produced grooves, 10.87 {+/-} 3.09 m or 17.77 {+/-} 4.91 m wide, respectively. Bone marrow derived mesenchymal stem cells (BM-MSCs) cultured on the scaffolds for four weeks exhibited similar degrees of alignment within {+/-} 10 {degrees} of the printing direction and upregulation of outer AF markers (COL1, COL12, SFRP, MKX, MCAM, SCX and TAGLN), with no statistically significant differences as a function of topography. Interestingly, the grooves generated by the patterned nozzles induced longitudinal end-to-end alignment of cells, capturing the arrangement of cells during fibrillogenesis. In contrast, topography produced from the round nozzle induced a continuous web of elongated cells without end-to-end alignment. Extracellular collagen I, decorin and fibromodulin were detected in patterns closely following cellular organization. Taken together, we present a single-step biofabrication strategy to induce anisotropic cellular alignments in x-, y-, and z-space, with potential application as an in vitro model for studying AF tissue morphogenesis and growth.

bioengineering↗