Biology subjects

Barthold, J.

Publications and source records attributed to Barthold, J..

7 recordsLinked to original sources

bioRxiv2026

Human Osteochondral Granular Extracellular Matrix (gECM) Hydrogels Drive Tissue-Specific Composition and Mechanics

Osteochondral defects remain a major clinical challenge due to the limited regenerative capacity of cartilage and the complexity of the osteochondral interface. Here, we present a human-derived granular extracellular matrix (gECM) hydrogel platform designed for translational osteochondral repair. Using otherwise discarded human donor tissues, we developed cartilage and bone gECM hydrogels under current good manufacturing practice workflows. These materials are shear-thinning, immediately hold their form, and crosslink under physiological conditions to form stable constructs. Proteomic analysis confirmed that cartilage and bone gECM retain distinct tissue-specific biochemical signatures, while mechanical characterization demonstrated tissue-relevant stiffness, with bone gECM hydrogels exhibiting greater stiffness than cartilage gECM hydrogel. Particle packing density primarily governed viscosity, whereas tissue type contributed strongly to bulk stiffness. Together, these findings establish a scalable, human-derived gECM platform that integrates tissue-specific structural and mechanical cues, and advances a clinically translatable strategy for osteochondral repair.

bioengineering↗

bioRxiv2026

Granular Extracellular Matrix (gECM) Hydrogel Wafers as Shelf-Stable 2.5D Substrates for Microphysiological Modeling

Understanding disease pathology and evaluating emerging therapeutics require in vitro models that accurately recapitulate human tissue environments. However, existing microphysiological systems often compromise either biomimicry or ease-of-use, limiting widespread adoption and scalability. Here, we present lyophilized granular extracellular matrix (gECM) hydrogel wafers as shelf-stable, humanized 2.5D substrates that enable physiologically relevant modeling while simplifying integration into experimental workflows. Derived from decellularized human cartilage and bone, gECM hydrogel wafers retain tissue-specific architecture while introducing microporosity and surface topography through lyophilization. These wafers maintain swelling behavior, structural integrity, and mechanical properties over three months of room-temperature storage, allowing pre-fabrication and on-demand use without loss of function. gECM hydrogel wafers support direct cell seeding without encapsulation and sustain viability and proliferation of human adipose-derived mesenchymal stromal cells over 21 days, with gene expression trends comparable to 3D gECM hydrogels. Furthermore, wafers can be readily integrated into microfluidic systems with in situ hydration and transport of large biomolecules. Together, this platform bridges the gap between conventional 2D culture ease-of-use and 3D biomaterial biomimicry, providing a scalable and physiologically relevant in vitro model approach for high-throughput disease studies and therapeutic screening.

bioengineering↗

bioRxiv2026

Granular Extracellular Matrix (gECM) Hydrogels Enable Distinct Composition and Mechanics Across Tissue Types for Translation

Biomaterials-based tissue engineering aims to recapitulate native tissue architecture and function for both clinical repair and advanced in vitro models. While improvements in biomaterials have been made, including granular hydrogels and ECM-derived scaffolds, current biomaterials lack intentional design choices for effective translation, including regulatory considerations, practical extrusion delivery, and biomimetic characteristics. Here, we develop and characterize a library of granular ECM (gECM) biomaterials for five key tissues (cartilage, bone, skin, liver, and kidney), in which ECM particles are densely packed within a hyaluronic acid hydrogel. We optimize tissue processing methods that preserve proteomic content and structure while also aligning with scale-up manufacturing and regulatory guidelines. We show that gECM hydrogels can be molded, extruded, and 3D-printed while retaining their shape, and they stabilize at physiological temperature and pH. Lastly, we demonstrate that bulk gECM mechanics are driven by tissue type, and gECM hydrogels support viability, proliferation, and tissue-specific cellular activity. Together, these findings establish gECM hydrogels as a translational and biomimetic platform for clinical tissue repair and complex in vitro models.

bioengineering↗

bioRxiv2026

Flowable Grafts Made from Granular Extracellular Matrix (gECM) Hydrogels Promote Integrative Repair of Articular Cartilage in a Large-Animal Model

Focal injuries to articular cartilage in load-bearing joints fail to heal and often progress to degeneration, underscoring the need for repair strategies that result in restored cartilage structure and function rather than fibrocartilage formation. Granular extracellular matrix (gECM) hydrogels, flowable grafts composed of densely-packed matrix particles, offer a promising approach but lack long-term functional validation in large-animal models. Here, we developed a flowable gECM hydrogel composed of decellularized cartilage microparticles incorporated within a thiol-functionalized hyaluronan matrix. Proteomic analysis confirmed enrichment of cartilage-specific gECM matrisome components. When implanted into critical-sized femoral condyle defects in a goat model and evaluated 12 months post-implantation, both gECM hydrogel and microdrilling (surgical controls) achieved >80% defect filling. However, in contrast to microdrilling, gECM repair tissue exhibited surface tribological (friction, adhesion) and compressive mechanical properties comparable to native cartilage, with a similar proteoglycan-to-collagen ratio, enrichment of type II collagen, minimal type I collagen (typical of a fibrous scar), improved quantitative MRI metrics, and evidence of lateral cartilage integration and subchondral bone remodeling. Together, these findings demonstrate that a flowable gECM hydrogel supports integrative, cartilage-like repair in a load-bearing joint, supporting advancement of this approach toward clinical translation. One Sentence SummaryA granular ECM hydrogel implanted in a goat condyle provided a robust repair, filling the defect tissue with integrated, hyaline-like cartilage at 12 months.

bioengineering↗

bioRxiv2021

Epigenetic remodeling during monolayer cell expansion reduces therapeutic potential

Understanding how cells remember previous mechanical environments to influence their fate, or mechanical memory, informs the design of biomaterials and therapies in medicine. Current regeneration therapies require two-dimensional (2D) cell expansion processes to achieve large cell populations critical for the repair of damaged (e.g. connective and musculoskeletal) tissues. However, the influence of mechanical memory on cell fate following expansion is unknown, and mechanisms defining how physical environments influence the therapeutic potential of cells remain poorly understood. Here, we show that the organization of histone H3 trimethylated at lysine 9 (H3K9me3) and expression of tissue-identifying genes in primary cartilage cells (chondrocytes) transferred to three-dimensional (3D) hydrogels depends on the number of previous population doublings on tissue culture plastic during 2D cell expansion. Decreased levels of H3K9me3 occupying promoters of dedifferentiation genes after the 2D culture were also retained in 3D culture. Suppression of H3K9me3 during expansion of cells isolated from a murine model similarly resulted in the loss of the chondrocyte phenotype and global remodeling of nuclear architecture. In contrast, increasing levels of H3K9me3 through inhibiting H3K9 demethylases partially rescued the chondrogenic nuclear architecture and gene expression, which has important implications for tissue repair therapies, where expansion of large numbers of phenotypically-suitable cells is required. Overall, our findings indicate mechanical memory in primary cells is encoded in the chromatin architecture, which impacts cell fate and the phenotype of expanded cells. SIGNIFICANCE STATEMENTTissue regeneration procedures, such as cartilage defect repair (e.g. Matrix-induced Autologous Chondrocyte Implantation) often require cell expansion processes to achieve sufficient cells to transplant into an in vivo environment. However, the chondrocyte cell expansion on 2D stiff substrates induces epigenetic changes that persist even when the chondrocytes are transferred to a different (e.g. 3D) or in vivo environment. Treatments to alter epigenetic gene regulation may be a viable strategy to improve existing cartilage defect repair procedures and other tissue engineering procedures that involve cell expansion.

bioengineering↗

bioRxiv2020

Percolation of Microparticle Matrix Promotes Cell Migration and Integration while Supporting Native Tissue Architecture

Cells embedded in the extracellular matrix of tissues play a critical role in maintaining homeostasis while promoting integration and regeneration following damage or disease. Emerging engineered biomaterials utilize decellularized extracellular matrix as a tissue-specific support structure; however, many dense, structured biomaterials unfortunately demonstrate limited formability, fail to promote cell migration, and result in limited tissue repair. Here, we developed a reinforced composite material of densely packed acellular extracellular matrix microparticles in a hydrogel, termed tissue clay, that can be molded and crosslinked to mimic native tissue architecture. We utilized hyaluronic acid-based hydrogels, amorphously packed with acellular articular cartilage tissue particulated to ~125-250 microns in diameter and defined a percolation threshold of 0.57 (v/v) beyond which the compressive modulus exceeded 300kPa. Remarkably, primary chondrocytes recellularized particles within 48 hours, a process driven by chemotaxis, exhibited distributed cellularity in large engineered composites, and expressed genes consistent with native cartilage repair. We additionally demonstrated broad utility of tissue clays through recellularization and persistence of muscle, skin, and cartilage composites in a subcutaneous in vivo mouse model. Our findings suggest optimal strategies and material architectures to balance concurrent demands for large-scale mechanical properties while also supporting integration of dense musculoskeletal and connective tissues.

bioengineering↗

bioRxiv2016

Adaptive and Non-adaptive Responses of Populations to Environmental Change

Understanding how the natural world will be impacted by environmental change over the coming decades is one of the most pressing challenges facing humanity. Addressing this challenge is difficult because environmental change can generate both population level plastic and evolutionary responses, with plastic responses being either adaptive or non-adaptive. We develop an approach that links quantitative genetic theory with data-driven structured models to allow prediction of population responses to environmental change via plasticity and adaptive evolution. After introducing general new theory, we construct a number of example models to demonstrate that evolutionary responses to environmental change over the short-term will be considerably slower than plastic responses, and that the rate of adaptive evolution to a new environment depends upon whether plastic responses are adaptive or non-adaptive. Parameterization of the models we develop requires information on genetic and phenotypic variation and demography that will not always be available, meaning that simpler models will often be required to predict responses to environmental change. We consequently develop a method to examine whether the full machinery of the evolutionarily explicit models we develop will be needed to predict responses to environmental change, or whether simpler non-evolutionary models that are now widely constructed may be sufficient.

evolutionary biology↗