Biology subjects

Molley, T. G.

Publications and source records attributed to Molley, T. G..

4 recordsLinked to original sources

bioRxiv2024

Enzyme Bioink for the 3D Printing of Biocatalytic Materials

The field of 3D biofabrication faces major challenges on the road to printing fully functional tissues and organs. One of them is adding functionality to the newly formed tissue for replicating an active biochemical environment. Native extracellular matrices sequester numerous bioactive species, making the microenvironment biochemically active. On the other hand, most 3D-printed constructs have limited activity, serving merely as mechanical scaffolding. Here we demonstrate active scaffolding through the integration of biocatalytic enzymes within the bioink. Enzymes are an attractive class of biocompatible and substrate-specific bioactive agents that can improve tissue regeneration outcomes. However, the difficulty in the application remains in providing enzymes at the targeted site in adequate amounts over an extended time. In this work, a durable biocatalytic active enzyme bioink for 3D extrusion-based bioprinting is developed by covalently attaching the globular enzyme horseradish peroxidase (HRP) to a gelatin methacrylate (Gel-MA) biopolymer scaffold. Upon introducing methacrylate groups on the surface of the enzyme, it undergoes photo-crosslinking in a post-printing step with the methacrylate groups of Gel-MA without compromising its activity. As a result, HRP becomes a fixed part of the hydrogel network and achieves higher stability inside the gel which results in a higher concentration and catalytic activity for a longer time than solely entrapping the protein inside the hydrogel. We also demonstrate the cytocompatibility of this enzyme bioink and show its printing capabilities for precise applications in the field of tissue engineering. Our approach offers a promising solution to enhance the bioactive properties of 3D-printed constructs, representing a critical step towards achieving functional biofabricated tissues.

bioengineering↗

bioRxiv2021

Defined microenvironments trigger in vitro gastrulation in human pluripotent stem cells

Embryogenesis is orchestrated through local morphogen gradients and endometrial constraints that give rise to the three germ layers in a well-defined assembly. In vitro models of embryogenesis have been demonstrated by treating pluripotent stem cells in adherent or suspension culture with soluble morphogens and small molecules, which leads to tri-lineage differentiation. However, treatment with exogenous agents override the subtle spatiotemporal changes observed in vivo that ultimately underly the human body plan. Here we demonstrate how microconfinement of pluripotent stem cells on hydrogel substrates catalyses gastrulation-like events without the need for supplements. Within six hours of initial seeding, cells at the boundary show elevated cytoskeletal tension and yes-associated protein (YAP) activity, which leads to changes in cell and nuclear morphology, epithelial to mesenchymal transition, and emergence of defined patterns of primitive streak containing SRY-Box Transcription Factor 17 (SOX17)+ T/BRACHYURY+ cells. Immunofluorescence staining, transcript analysis, and the use of pharmacological modulators reveal a role for mechanotransduction-coupled non-canonical wingless-type (WNT) signalling in promoting epithelial to mesenchymal transition and multilayered organization within the colonies. These microscale gastruloids were removed from the substrate and encapsulated in 3D hydrogels, where biomaterials properties correspond to maintenance and spatial positioning of the primitive streak. Together, this approach demonstrates how materials alone can nurture embryonic gastrulation, thereby providing an in vitro model of early development.

bioengineering↗

bioRxiv2020

Freeform printing of heterotypic tumor models within cell-laden microgel matrices

The tissue microenvironment is comprised of a complex assortment of multiple cell types, matrices, membranes and vessel structures. Emulating this complex and often hierarchical organization in vitro has proved a considerable challenge, typically involving segregation of different cell types using layer-by-layer printing or lithographically patterned microfluidic devices. Bioprinting in granular materials is a new methodology with tremendous potential for tissue fabrication. Here, we demonstrate the first example of a complex tumor microenvironment that combines direct writing of tumor aggregates, freeform vasculature channels, and a tunable macroporous matrix as a model to studying metastatic signaling. Our photocrosslinkable microgel suspensions yield local stiffness gradients between particles and the intervening space, while enabling the integration of virtually any cell type. Using computational fluid dynamics, we show that removal of a sacrificial Pluronic ink defines vessel-mimetic channel architectures for endothelial cell linings. Pairing this vasculature with 3D printing of melanoma aggregates, we find that tumor cells within proximity migrated into the prototype vasculature. Together, the integration of perfusable channels with multiple spatially defined cell types provides new avenues for modelling development and disease, with scope for fundamental research and drug development.

bioengineering↗

bioRxiv2019

Geometric regulation of histone state directs melanoma reprogramming

Malignant melanoma displays a high degree of cellular plasticity during disease progression, making classification of the heterogeneous population and selection of an appropriate therapy challenging. Signals in the tumor microenvironment are believed to influence melanoma plasticity through changes in the epigenetic state to guide dynamic differentiation and de-differentiation events that underlie tumorigenicity and dissemination. Here we uncover a relationship between geometric features at perimeter regions of multicellular melanoma aggregates, and reprogramming to a stem cell-like melanoma initiating cell (MIC) through histone marks H3K4Me2 and H3K9Ac. Using an in vitro tumor microengineering approach, we find concurrent expression of molecular MIC markers and spatial enrichment of these histone modifications at perimeter features. Chromatin immunoprecipitation and sequencing analysis demonstrates broad regulation of genes associated with SOX-, ETS-, and USF-families. SOX10 and PRDM14, transcriptional regulators with a putative role in several cancers, overlap with H3K9Ac and show elevated expression in cells along regions of perimeter curvature. siRNA knockdown of the epigenetic modifier PRDM14 abolishes the MIC phenotype suggesting a role in regulating melanoma heterogeneity. Our results suggest mechanotransduction at the periphery of melanoma tumors may orchestrate the activity of epigenetic modifiers to regulate histone state, cellular plasticity, and tumorigenicity.

cancer biology↗