Biology subjects

Stoddart, M. J.

Publications and source records attributed to Stoddart, M. J..

6 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↗

bioRxiv2026

Modulation of ossification and inflammatory pathways during dexamethasone-induced in vitro osteogenesis

BackgroundDexamethasone (DEX) is used in vitro to promote osteogenic differentiation of human bone marrow mesenchymal stromal cells (hBMSCs). In clinical use, however, glucocorticoids induce osteoblast and osteocyte apoptosis while increasing osteoclast survival, leading overall to osteoporosis and high fracture risk. The overall impact of DEX on the differentiation of human progenitor cells remains contradictory and not fully understood, highlighting the need for further investigation using sequencing approaches as in vitro results will naturally influence further translational research. MethodshBMSCs were induced to osteogenic differentiation for 7 days using different concentrations of either DEX or the nonsteroidal glucocorticoid receptor agonist (+)-ZK216348. cDNA library preparation and RNA sequencing (RNAseq) were performed using Oxford Nanopore Technologies. Differentially expressed genes and pathways associated to the transactivation or transrepression activity of DEX were identified. Sequencing results were validated by qPCR, protein analysis, and with a functional assay on peripheral blood mononuclear cells to determine the overall effect of the BMSC supernatant. ResultsHierarchical clustering of RNAseq data identified eight subclusters with shared regulatory patterns. Enrichment analysis revealed that both upregulated and downregulated genes are involved in ossification and extracellular matrix organization pathways. Several pro- and anti-inflammatory genes were differentially regulated. qPCR analysis validated the upregulation of CXCL1, CXCL8, IL18, and COL8A1, while MMP1 and CXCL12 expression decreased in response to DEX. Comparing DEX results with those obtained using (+)-ZK216348 helped distinguish the potential mechanisms regulating the expression of specific genes. Notably, CXCL8 upregulation occurred through transactivation, whereas COL8A1 upregulation is downstream of a transrepressed gene. Further in vitro experiments confirmed that DEX significantly increased CXCL8 expression and IL-8 secretion. However, hPBMC responses indicated no significant pro- or anti-inflammatory effects from hBMSC conditioned medium. ConclusionsIn conclusion, the effects of DEX on the transcriptome of hBMSCs in a pro-osteogenic environment do not fully replicate the acquisition of an osteogenic phenotype. Several genes associated with ossification, extracellular matrix organization, and inflammation were dysregulated. The unique expression patterns of pro-inflammatory cytokines and collagen types warrant further investigation to elucidate their roles in osteogenic differentiation and bone homeostasis.

cell biology↗

bioRxiv2025

Antibodies blocking PlGF or VEGF interactions with the NRP1 receptormediate anti-proliferative effects

Antibodies blocking the function of vascular endothelial growth factor A (VEGFA) remain a promising therapeutic strategy, especially when combined with check-point inhibitors, but their efficacy is limited by tumor resistance. This can occur via multiple mechanisms, including upregulation of placental growth factor 2 (PlGF-2), an alternative ligand for VEGF receptor 1 (VEGFR1) and neuropilin receptor 1 (NRP1). Activity of both growth factors is mediated by interactions with multiple receptors and extra-cellular matrix components, which complicates efforts to understand their contributions to cancer progression. To complement existing antibodies, we discovered those blocking interactions between PlGF-2 or VEGFA and their shared NRP1 receptor in the presence of heparin. Limiting angiogenesis to promote vascular normalization is one mechanism of anti-VEGF protection; here, anti-VEGFA antibodies blocking interactions with VEGFR1 and NRP1 reduced HUVEC tube formation in a physiological angiogenesis model. By contrast, antibodies binding PlGF-2 or VEGFA to block NRP1 significantly reduced proliferation of Caki-I kidney carcinoma cells in vitro, indicating this receptor mediates additional effects. Interestingly, one antibody exhibited dual-reactive binding to VEGFA and PlGF-2, suggesting a novel therapeutic strategy to prevent PlGF-driven VEGF-resistance. Overall, these antibodies define new mechanisms to disrupt PlGF activity and support a role for NRP1 in cell proliferation. Key ResultsO_LINew antibodies binding VEGFA or PlGF selectively block NRP1-receptor interactions. C_LIO_LIAntibody blockade of VEGFA binding to NRP1 reduced HUVEC angiogenesis. C_LIO_LIBlocking growth factor interactions with NRP1 reduced Caki-I renal carcinoma proliferation. C_LIO_LIIdentified an antibody with dual-reactive binding to VEGFA and PlGF. C_LI

biochemistry↗

bioRxiv2025

Bioconvergence of sound-guided and supramolecular assembly strategies to create peptide-protein composite hydrogels with predictable shape-to-function features

Purely protein-based hydrogels are widely used in tissue engineering for their biomimicry and biocompatibility, yet remain challenging to tailor with precision and predictability at biological and mechanical levels. To overcome this, synthetic self-assembling peptide amphiphiles (PAs) offer opportunities for supramolecular customization, both as single-phase materials and co-assembled with proteins to create hybrid nanocomposites with emerging functionalities. Similarly, contactless, sound-guided bioassembly techniques using liquid-phase hydrogel precursors are emerging as strategic tools for obtaining structured and functional hydrogels. Leveraging these advances, here a fast, contactless, one-pot bioassembly strategy merging supramolecular PA self-assembly with sound-guided patterning to fabricate hybrid peptide-protein hydrogels with programmable shape-to-function features is presented. Using fibrin as proof-of-concept, material performance is biologically enhanced by incorporating growth factor-binding PAs, while inorganic microparticles are embedded and spatially organized via acoustic fields to tune mechanical properties. This strategy allows predictable tuning of composite stiffness and architecture by adjusting sound wave frequency, with acoustic fields guiding material organization from micro-to-macroscale. Composite hydrogels result highly permissive to cell infiltration in vitro and versatile platform to tune immune cell-material interactions. This modular biofabrication platform integrating supramolecular and sound-guided processes can be generalized to other building blocks opening unique opportunities for scalable, tunable, and hierarchically-organized biomaterials.

bioengineering↗

bioRxiv2024

Anisotropic Articular Cartilage Biofabrication based on Decellularized Extracellular Matrix

Tissue-engineered grafts that mimic articular cartilage show promise for treating cartilage injuries. However, engineering cartilage cell-based therapies to match zonal architecture and biochemical composition remains challenging. Decellularized articular cartilage extracellular matrix (dECM) has gained attention for its chondro-inductive properties, yet dECM-based bioinks have limitations in mechanical stability and printability. This study proposes a rapid light-based bioprinting method using a tyrosine-based crosslinking mechanism, which does not require chemical modifications of dECM and thereby preserves its structure and bioactivity. Combining this resin with Filamented Light (FLight) biofabrication enables the creation of cellular, porous, and anisotropic dECM scaffolds composed of aligned microfilaments. Specifically, we investigate the effects of various biopolymer compositions (i.e., hyaluronic acid, collagen I, and dECM) and inner architecture (i.e., bulk light vs FLight) on immune response and cell morphology, and we investigate their influence on nascent ECM production and long-term tissue maturation. Our findings highlight the importance of FLight scaffolds in directing collagen deposition resembling articular cartilage structure and promoting construct maturation, and they emphasize the superiority of biological-rich dECM over single-component materials for engineering articular cartilage, thereby offering new avenues for the development of effective cartilage tissue engineering strategies.

bioengineering↗