Matrix Ligands Research Articles

RECAPITULATING THE POST-SURGICAL BRAIN MICROENVIRONMENT OF ATYPICAL TERATOID RHABDOID TUMOURS TO IDENTIFY MEMBRANE PROTEINS FOR TARGETED THERAPY

Abstract AIMS Atypical Teratoid Rhabdoid Tumours (AT/RT) are rare aggressive tumours primarily arising in the hind brain of children under three, conferring median survival of <12 months. Surgery remains the only standard treatment; however tumours recur from post-surgical residual disease. Decellularised human brain cerebellum aim to recapitulate AT/RT post-surgical brain microenvironments which retain extracellular matrix (ECM) ligands, and where AT/RT plasma membrane proteins are hypothesised to represent viable molecular therapy targets. METHOD AT/RT, astrocyte and human brain cerebellum (decellularised and non-decellularised) membrane protein fractions were extracted and analysed using liquid chromatography-mass spectrometry. Proteomic analysis tools were integrated to identify differential expressed proteins and identify shared correlations. RESULTS Decellularised cerebellar ECM exhibited an enriched membrane proteome relative to total proteome, evidence of complete removal of intracellular components. Furthermore, decellularised and non-decellularised cerebellar tissue expressed comparable levels of membrane proteins and protein networks, indicative of ECM ligand retention. AT/RT and astrocyte KEGG Pathway analysis revealed specific oncology-based pathway expression in membrane protein compared to total protein, reinforcing membrane proteins as more visible therapeutic targets. Between the top 20 expressed proteins, ATP1A1 was the only membrane protein shared exclusively between all AT/RT cells and astrocytes, suggesting a critical functional role. Membrane proteins showing shared expression when normalised against each AT/RT cell line included ATP1A1, HSPD1, GNA13 and SLC3A2, indicating biological similarities between AT/RT molecular subtypes, which may offer candidate ubiquitous therapy targets. Membrane proteins expressed similarly in AT/RT-MYC molecular subtypes include ATP1A1, SLC7A5 and EEF1A1. STRING membrane pathway analysis also identified shared proteins between AT/RT and astrocyte cell populations. CONCLUSION AT/RT membrane protein pathways provide ideal therapeutic targets directly amenable for drug repurposing. Future work prioritises proteomic analysis utilising 3D AT/RT spheroids and cerebellum brain tissue to maximise accurately recapitulating the AT/RT post-surgical microenvironment. Cerebellum decellularisation still permits retention of essential proteins and ligands.

Measuring Integrin Force Loading Rates Using a Two-Step DNA Tension Sensor.

Cells apply forces to extracellular matrix (ECM) ligands through transmembrane integrin receptors: an interaction which is intimately involved in cell motility, wound healing, cancer invasion and metastasis. These small (piconewton) integrin-ECM forces have been studied by molecular tension fluorescence microscopy (MTFM), which utilizes a force-induced conformational change of a probe to detect mechanical events. MTFM has revealed the force magnitude for integrin receptors in a variety of cell models including primary cells. However, force dynamics and specifically the force loading rate (LR) have important implications in receptor signaling and adhesion formation and remain poorly characterized. Here, we develop an LR probe composed of an engineered DNA structure that undergoes two mechanical transitions at distinct force thresholds: a low force threshold at 4.7 pN (hairpin unfolding) and a high force threshold at 47 pN (duplex shearing). These transitions yield distinct fluorescence signatures observed through single-molecule fluorescence microscopy in live cells. Automated analysis of tens of thousands of events from eight cells showed that the bond lifetime of integrins that engage their ligands and transmit a force >4.7 pN decays exponentially with a τ of 45.6 s. A subset of these events mature in magnitude to >47 pN with a median loading rate of 1.1 pN s-1 and primarily localize at the periphery of the cell-substrate junction. The LR probe design is modular and can be adapted to measure force ramp rates for a broad range of mechanoreceptors and cell models, thus aiding in the study of molecular mechanotransduction in living systems.

Silica gel-supported Pd nanocatalyst: Efficient Mizoroki-Heck reactions and sustainable Ozagrel synthesis

We developed a cost-effective silica gel-supported palladium nanocatalyst in a three-step reactions process. Initially, silica gel (60–120 mesh) underwent amino group functionalization using 3-aminopropyltriethoxysilane, leading to the formation of a Schiff base through a reaction with the 1,10-phenanthroline-2,9-dicarboxaldehyde ligand. Subsequently, palladium nanocatalyst was introduced to the silica matrix ligand in the presence of palladium salt and hydrazine hydrate, resulting in the formation of the silica gel-supported Schiff-base palladium nanocatalyst (Si@SBPdNPs 3). Successful functionalization of the silica matrix was confirmed using various spectroscopic techniques. FT-IR spectra demonstrated the incorporation of organic moieties onto the silica surface, while SEM images revealed the modified spherical shape of the silica gel. TEM and XRD analyses confirmed the presence of palladium on the silica matrix. ICP and EDX measurements validated the anchoring of 0.55 mmol/g of palladium to the catalyst. Additionally, XPS analysis showed the complexation of Pd(0) with the organic ligand on the silica matrix, confirming the successful integration of palladium into the system. This nanocatalyst demonstrated outstanding performance in Mizoroki-Heck reactions, yielding high product outputs in the cross-coupling of various aryl halides and olefins under mild conditions. Additionally, the nanocatalyst was effectively utilized in synthesizing Ozagrel, a thromboxane A2 synthesis inhibitor used for treating noncardioembolic stroke patients. Remarkably, the catalyst demonstrated excellent reusability, maintaining high productivity across five consecutive cycles, underscoring its economic and sustainable potential for industrial applications.

Dynamic Regulation of Cell Mechanotransduction through Sequentially Controlled Mobile Surfaces.

The physical properties of nanoscale cell-extracellular matrix (ECM) ligands profoundly impact biological processes, such as adhesion, motility, and differentiation. While the mechanoresponse of cells to static ligands is well-studied, the effect of dynamic ligand presentation with "adaptive" properties on cell mechanotransduction remains less understood. Utilizing a controllable diffusible ligand interface, we demonstrated that cells on surfaces with rapid ligand mobility could recruit ligands through activating integrin α5β1, leading to faster focal adhesion growth and spreading at the early adhesion stage. By leveraging UV-light-sensitive anchor molecules to trigger a "dynamic to static" transformation of ligands, we sequentially activated α5β1 and αvβ3 integrins, significantly promoting osteogenic differentiation of mesenchymal stem cells. This study illustrates how manipulating molecular dynamics can directly influence stem cell fate, suggesting the potential of "sequentially" controlled mobile surfaces as adaptable platforms for engineering smart biomaterial coatings.

Integrin mechanosensing relies on a pivot-clip mechanism to reinforce cell adhesion

Cells intricately sense mechanical forces from their surroundings, driving biophysical and biochemical activities. This mechanosensing phenomenon occurs at the cell-matrix interface, where mechanical forces resulting from cellular motion, such as migration or matrix stretching, are exchanged through surface receptors, primarily integrins, and their corresponding matrix ligands. A pivotal player in this interaction is the α5β1 integrin and fibronectin (FN) bond, known for its role in establishing cell adhesion sites for migration. However, upregulation of the α5β1-FN bond is associated with uncontrolled cell metastasis. This bond operates through catch bond dynamics, wherein the bond lifetime paradoxically increases with greater force. The mechanism sustaining the characteristic catch bond dynamics of α5β1-FN remains unclear. Leveraging molecular dynamics simulations, our approach unveils a pivot-clip mechanism. Two key binding sites on FN, namely the synergy site and the RGD (Arg-Gly-Asp) motif, act as active points for structural changes in α5β1 integrin. Conformational adaptations at these sites are induced by a series of hydrogen bond formations and breaks at the synergy site. We disrupt these adaptations through a double mutation on FN, known to reduce cell adhesion. A whole-cell finite-element model is employed to elucidate how the synergy site may promote dynamic α5β1-FN binding, resisting cell contraction. In summary, our study integrates molecular- and cellular-level modeling to propose that FN’s synergy site reinforces cell adhesion through enhanced binding dynamics and a mechanosensitive pivot-clip mechanism. This work sheds light on the interplay between mechanical forces and cell-matrix interactions, contributing to our understanding of cellular behaviors in physiological and pathological contexts.

Validation of a novel western blot assay to monitor patterns and levels of alpha dystroglycan in skeletal muscle of patients with limb girdle muscular dystrophies

The cell membrane protein, dystroglycan, plays a crucial role in connecting the cytoskeleton of a variety of mammalian cells to the extracellular matrix. The α-subunit of dystroglycan (αDG) is characterized by a high level of glycosylation, including a unique O-mannosyl matriglycan. This specific glycosylation is essential for binding of αDG to extracellular matrix ligands effectively. A subset of muscular dystrophies, called dystroglycanopathies, are associated with aberrant, dysfunctional glycosylation of αDG. This defect prevents myocytes from attaching to the basal membrane, leading to contraction-induced injury. Here, we describe a novel Western blot (WB) assay for determining levels of αDG glycosylation in skeletal muscle tissue. The assay described involves extracting proteins from fine needle tibialis anterior (TA) biopsies and separation using SDS-PAGE followed by WB. Glycosylated and core αDG are then detected in a multiplexed format using fluorescent antibodies. A practical application of this assay is demonstrated with samples from normal donors and patients diagnosed with LGMD2I/R9. Quantitative analysis of the WB, which employed the use of a normal TA derived calibration curve, revealed significantly reduced levels of αDG in patient biopsies relative to unaffected TA. Importantly, the assay was able to distinguish between the L276I homozygous patients and a more severe form of clinical disease observed with other FKRP variants. Data demonstrating the accuracy and reliability of the assay are also presented, which further supports the potential utility of this novel assay to monitor changes in ⍺DG of TA muscle biopsies in the evaluation of potential therapeutics.

Fibroblast and myofibroblast activation in normal tissue repair and fibrosis.

The term 'fibroblast' often serves as a catch-all for a diverse array of mesenchymal cells, including perivascular cells, stromal progenitor cells and bona fide fibroblasts. Although phenotypically similar, these subpopulations are functionally distinct, maintaining tissue integrity and serving as local progenitor reservoirs. In response to tissue injury, these cells undergo a dynamic fibroblast-myofibroblast transition, marked by extracellular matrix secretion and contraction of actomyosin-based stress fibres. Importantly, whereas transient activation into myofibroblasts aids in tissue repair, persistent activation triggers pathological fibrosis. In this Review, we discuss the roles of mechanical cues, such as tissue stiffness and strain, alongside cell signalling pathways and extracellular matrix ligands in modulating myofibroblast activation and survival. We also highlight the role of epigenetic modifications and myofibroblast memory in physiological and pathological processes. Finally, we discuss potential strategies for therapeutically interfering with these factors and the associated signal transduction pathways to improve the outcome of dysregulated healing.

Screening of differentially expressed genes in gastric cancer based on GEO database and function and pathway enrichment analysis

To explore the core genes related to the diagnosis and prognosis of gastric cancer (GC) based on Gene Expression Omnibus (GEO) database and screen the molecular targets involved in the occurrence and development of GC. GC microarray data GSE118916, GSE54129 and GSE79973 were downloaded from GEO database, and the differentially expressed genes (DEGs) were screened. Enrichment analysis of the signaling pathways and molecular functions were preformed and protein-protein interaction networks (PPI) were constructed to identify the hub genes, whose expression levels and diagnostic and prognostic values were verifies based on gastric adenocarcinoma data from TCGA. The expression levels of these core genes were also detected in different GC cell lines using qRT- PCR. Seventy-seven DEGs were identified, which encodes proteins located mainly in the extracellular matrix and basement membrane with activities of oxidoreductase and extracellular matrix receptor and ligand, involving the biological processes of digestion and hormone metabolism and the signaling pathways in retinol metabolism and gastric acid secretion. Nine hub genes were obtained, among which SPARC, TIMP1, THBS2, COL6A3 and THY1 were significantly up- regulated and TFF1, GKN1, TFF2 and PGC were significantly down-regulated in GC. The abnormal expressions of SPARC, TIMP1, THBS2, COL6A3, TFF2 and THY1 were significantly correlated with the survival time of GC patients. ROC curve analysis showed that aberrant expression of TIMP1 SPARC, THY1 and THBS2 had high diagnostic value for GC. High expressions of SPARC, TIMP1, THBS2 and COL6A3 were detected in GC tissues. In the GC cell lines, qRT- PCR revealed different expression patterns of these hub genes, but their expressions were largely consistent with those found in bioinformatics analyses. SPARC, TIMP1, THBS2 and other DEGs are probably involved in GC occurrence and progression and may serve as potential candidate molecular markers for early diagnosis and prognostic evaluation of GC.

Culture substrate stiffness impacts human myoblast contractility-dependent proliferation and nuclear envelope wrinkling.

Understanding how biophysical and biochemical microenvironmental cues together influence the regenerative activities of muscle stem cells and their progeny is crucial in strategizing remedies for pathological dysregulation of these cues in aging and disease. In this study, we investigated the cell-level influences of extracellular matrix (ECM) ligands and culture substrate stiffness on primary human myoblast contractility and proliferation within 16 h of plating and found that tethered fibronectin led to stronger stiffness-dependent responses compared to laminin and collagen. A proteome-wide analysis further uncovered cell metabolism, cytoskeletal and nuclear component regulation distinctions between cells cultured on soft and stiff substrates. Interestingly, we found that softer substrates increased the incidence of myoblasts with a wrinkled nucleus, and that the extent of wrinkling could predict Ki67 (also known as MKI67) expression. Nuclear wrinkling and Ki67 expression could be controlled by pharmacological manipulation of cellular contractility, offering a potential cellular mechanism. These results provide new insights into the regulation of human myoblast stiffness-dependent contractility response by ECM ligands and highlight a link between myoblast contractility and proliferation.

Utilizing multiscale engineered biomaterials to examine TGF-β-mediated myofibroblastic differentiation.

Cells integrate many mechanical and chemical cues to drive cell signalling responses. Because of the complex nature and interdependency of alterations in extracellular matrix (ECM) composition, ligand density, mechanics, and cellular responses it is difficult to tease out individual and combinatorial contributions of these various factors in driving cell behavior in homeostasis and disease. Tuning of material viscous and elastic properties, and ligand densities, in combinatorial fashions would enhance our understanding of how cells process complex signals. For example, it is known that increased ECM mechanics and transforming growth factor beta (TGF-β) receptor (TGF-β-R) spacing/clustering independently drive TGF-β signalling and associated myofibroblastic differentiation. However, it remains unknown how these inputs orthogonally contribute to cellular outcomes. Here, we describe the development of a novel material platform that combines microgel thin films with controllable viscoelastic properties and DNA origami to probe how viscoelastic properties and nanoscale spacing of TGF-β-Rs contribute to TGF-β signalling and myofibroblastic differentiation. We found that highly viscous materials with non-fixed TGF-β-R spacing promoted increased TGF-β signalling and myofibroblastic differentiation. This is likely due to the ability of cells to better cluster receptors on these surfaces. These results provide insight into the contribution of substrate properties and receptor localisation on downstream signalling. Future studies allow for exploration into other receptor-mediated processes.

A Library of Elastin-like Proteins with Tunable Matrix Ligands for In Vitro 3D Neural Cell Culture.

Hydrogels with encapsulated cells have widespread biomedical applications, both as tissue-mimetic 3D cultures in vitro and as tissue-engineered therapies in vivo. Within these hydrogels, the presentation of cell-instructive extracellular matrix (ECM)-derived ligands and matrix stiffness are critical factors known to influence numerous cell behaviors. While individual ECM biopolymers can be blended together to alter the presentation of cell-instructive ligands, this typically results in hydrogels with a range of mechanical properties. Synthetic systems that allow for the facile incorporation and modulation of multiple ligands without modification of matrix mechanics are highly desirable. In the present work, we leverage protein engineering to design a family of xeno-free hydrogels (i.e., devoid of animal-derived components) consisting of recombinant hyaluronan and recombinant elastin-like proteins (ELPs), cross-linked together with dynamic covalent bonds. The ELP components incorporate cell-instructive peptide ligands derived from ECM proteins, including fibronectin (RGD), laminin (IKVAV and YIGSR), collagen (DGEA), and tenascin-C (PLAEIDGIELTY and VFDNFVL). By carefully designing the protein primary sequence, we form 3D hydrogels with defined and tunable concentrations of cell-instructive ligands that have similar matrix mechanics. Utilizing this system, we demonstrate that neurite outgrowth from encapsulated embryonic dorsal root ganglion (DRG) cultures is significantly modified by cell-instructive ligand content. Thus, this library of protein-engineered hydrogels is a cell-compatible system to systematically study cell responses to matrix-derived ligands.

Dynamic Micropatterning Reveals Substrate-Dependent Differences in the Geometric Control of Cell Polarization and Migration.

Cells are highly dynamic and adopt variable shapes and sizes. These variations are biologically important but challenging to investigate in a spatiotemporally controlled manner. Micropatterning, confining cells on microfabricated substrates with defined geometries and molecular compositions, is a powerful tool for controlling cell shape and interactions. However, conventional binary micropatterns are static and fail to address dynamic changes in cell polarity, spreading, and migration. Here, a method for dynamic micropatterning is reported, where the non-adhesive surface surrounding adhesive micropatterns is rapidly converted to support specific cell-matrix interactions while allowing simultaneous imaging of the cells. The technique is based on ultraviolet photopatterning of biotinylated polyethylene glycol-grafted poly-L-lysine, and it is simple, inexpensive, and compatible with a wide range of streptavidin-conjugated ligands. Experiments using biotinylation-based dynamic micropatterns reveal that distinct extracellular matrix ligands and bivalent integrin-clustering antibodies support different degrees of front-rear polarity in human glioblastoma cells, which correlates to altered directionality and persistence upon release and migration on fibronectin. Unexpectedly, however, neither an asymmetric cell shape nor centrosome orientation can fully predict the future direction of migration. Taken together, biotinylation-based dynamic micropatterns allow easily accessible and highly customizable control over cell morphology and motility.

Hyperglycemia exerts disruptive effects on the secretion of TGF-β1 and its matrix ligands, decorin and biglycan, by mesenchymal sub-populations and macrophages during bone repair

IntroductionBone has a high capacity for repair, but for patients with uncontrolled type 2 diabetes mellitus (T2DM), the associated hyperglycemia can significantly delay osteogenic processes. These patients respond poorly to fracture repair and bone grafts, leading to lengthy care plans due to arising complications. Mesenchymal stromal cells (MSCs) and M2 macrophages are both major sources of transforming growth factor-β1 (TGF-β1), a recognized mediator for osteogenesis and whose bioavailability and activities are further regulated by matrix small leucine-rich proteoglycans (SLRPs), decorin and biglycan. The aim of this study was to investigate how in vivo and in vitro hyperglycemic (HGly) environments can influence levels of TGF-β1, decorin, and biglycan during bone repair, with additional consideration for how long-term glucose exposure and cell aging can also influence this process.ResultsFollowing bone healing within a T2DM in vivo model, histological and immuno-labeling analyses of bone tissue sections confirmed delayed healing, which was associated with significantly elevated TGF-β1 levels within the bone matrices of young diabetic rats, compared with normoglycemic (Norm) and aged counterparts. Studies continued to assess in vitro effects of normal (5.5 mM) and high (25 mM) glucose exposure on the osteogenic differentiation of compact bone derived mesenchymal stromal cells (CB-MSCs) at population doubling (PD)15, characterized to contain populations of lineage committed osteoblasts, and at PD150, where transit-amplifying cells predominate. Short-term glucose exposure increased TGF-β1 and decorin secretion by committed osteoblasts but had a lesser effect on transit-amplifying cells. In contrast, the long-term exposure of CB-MSCs to high glucose was associated with decreased TGF-β1 and increased decorin secretion. Similar assessments on macrophage populations indicated high glucose inhibited TGF-β1 secretion, preventing M2 formation.DiscussionCollectively, these findings highlight how hyperglycemia associated with T2DM can perturb TGF-β1 and decorin secretion by MSCs and macrophages, thereby potentially influencing TGF-β1 bioavailability and signaling during bone repair.

Collagen VI Is a Gi-Biased Ligand of the Adhesion GPCR GPR126/ADGRG6.

GPR126/ADGRG6, a member of the adhesion G-protein-coupled receptor family, balances cell differentiation and proliferation through fine-tuning of intracellular cAMP levels, which is achieved through coupling to Gs and Gi proteins. While GPR126-mediated cAMP increase has been proven to be essential for differentiation of Schwann cells, adipocytes and osteoblasts, Gi-signaling of the receptor was found to propagate breast cancer cell proliferation. Extracellular ligands or mechanical forces can modulate GPR126 activity but require an intact encrypted agonist sequence, coined the Stachel. Even though coupling to Gi can be seen for constitutively active truncated receptor versions of GPR126 as well as with a peptide agonist derived from the Stachel sequence, all known N-terminal modulators have so far only been shown to modulate Gs coupling. Here, we identified collagen VI as the first extracellular matrix ligand of GPR126 that induces Gi signaling at the receptor, which shows that N-terminal binding partners can mediate selective G protein signaling cascades that are masked by fully active truncated receptor variants.

Mechanical Signal-Tailored Hydrogel Microspheres Recruit and Train Stem Cells for Precise Differentiation.

The aberrant mechanical microenvironment in degenerated tissues induces misdirection of cell fate, making it challenging to achieve efficient endogenous regeneration. Herein, a hydrogel microsphere-based synthetic niche with integrated cell recruitment and targeted cell differentiation properties via mechanotransduction was constructed for enhanced endogenous regeneration. Through the incorporation of microfluidics and photo-polymerization strategies, we prepared fibronectin (Fn) modified methacrylated gelatin (GelMA) microspheres with the independently tunable elastic modulus(1-10Kpa) and ECM ligand density (2 and 10μg/ml), allowing a wide range of cytoskeleton modulation to trigger the corresponding mechanobiological signaling to direct cell fate. The combination of the soft matrix (2Kpa) and low ligand density (2μg/ml) could support the nucleus pulposus (NP)-like differentiation of intervertebral disc (IVD) progenitor/stem cells by translocating Yes-associated protein (YAP), without the addition of inducible biochemical factors. Meanwhile, platelet-derived growth factor-BB was loaded onto Fn-GelMA microspheres (PDGF@Fn-GelMA) via the heparin-binding domain of Fn and exhibited continuous release for over 28 days to initiate endogenous cell recruitment. In in vivo experiments, hydrogel microsphere-niche maintained the IVD structure and stimulated ECM synthesis, thereby enhancing the endogenous regeneration of NP. Overall, this synthetic niche with cell recruiting and mechanical training capabilities offered a promising novel strategy for endogenous tissue regeneration. This article is protected by copyright. All rights reserved.

PATH-30. BIOLOGIC AND CLINICAL SIGNIFICANCE OF NEOPLASTIC AND IMMUNE CELL STATES IN GROUP3 AND GROUP 4 MEDULLOBLASTOMA

Abstract Medulloblastoma (MB) is a heterogeneous malignant childhood brain cancer, classified into four molecular subgroups, WNT, SHH, Group3, and Group4, based on transcriptional, genetic, and clinical features. We aimed to understand the tumor microenvironment of Group 3 and Group 4 tumors utilizing single-cell transcriptome data. We identified four neoplastic cell states, including stemness (TNF-α), proliferative, mesenchymal and quiescence, and 11 broad lymphoid and myeloid cell types from single-cell transcriptomes. We applied CIBERSORTx to enumerate cell type proportion and CODEFACS on 73 bulk MB RNAseq profiles to determine cell type-specific abundance and gene expression profiles. We noted significant associations (both positive and negative) between the abundance of neoplastic cell states and microenvironmental cell types in both group3 and group4 MB. For example, the invasive cell state negatively correlated with dendritic cells in Group3 and Group4 tumors, but the invasive cell state was oppositely correlated with a macrophage subset in group 3 versus group 4 tumors, Survival analysis showed a significant association of higher proliferative cell state with poorer survival in Group3 MB while in group4 elevated invasive cell state, as well as elevated α, NK, and CD4-T cell abundance showed trends for poorer prognosis. Using Ecotyper, we determined cellular ecotypes based on cell type-specific transcriptome states. An ecotype containing B cell, hematopoietic, dendritic, and proliferative cell states was associated with poor prognosis in group3 and group4 tumors. We further analyzed ligand-receptor interaction between cell type states of poor prognosis ecotype; and found several interactions between ligands from immune cells (SEMA4G, LAMB2) and receptors on neoplastic cells (PLXNB2). Conversely, extracellular matrix ligands on neoplastic cells (COL1A1/2 and FN1) were found on this analysis potentially associated with integrin receptors on immune cells. Overall, our study highlights the potential biologic and clinical significance of neoplastic and immune cell states in group3/4 MB.

On the role of elasticity in focal adhesion stability within the passive regime

Within a purely mechanical setting, we investigate the behavior, up to full decohesion, of a system modeling the interactions exchanged between focal adhesions and extra-cellular matrix in the passive regime. In our work, decohesion is described as a homogenized effect of low scales events leading to the rupture of the molecular bonds between integrin receptors and the extra-cellular matrix ligands. We propose a simple three-layers scheme of this mechanical system and, based on a Griffith-like approach, we analytically describe the transition from an elastic regime to the nucleation of a decohesion front, up to full decohesion. We focus our attention on the important role played by elasticity and deduce how the relative stiffness of the layers modulates the decohesion behavior, with the system undergoing a ductile–fragile detachment transition. The comparison with known experimental results on focal adhesions and DNA shear denaturation supports the effectiveness of the proposed model in predicting the mechanical behavior of decohesion phenomena in biological systems. Interestingly, we show the possibility of predicting focal adhesion lengths distribution based on the obtained force saturation as the focal adhesion dimension is increased theoretically deduced.

Cardiac ultrastructure inspired matrix induces advanced metabolic and functional maturation of differentiated human cardiomyocytes.

The vast potential of human induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs) in preclinical models of cardiac pathologies, precision medicine, and drug screening remains to be fully realized because hiPSC-CMs are immature without adult-like characteristics. Here, we present a method to accelerate hiPSC-CM maturation on a substrate, cardiac mimetic matrix (CMM), mimicking adult human heart matrix ligand chemistry, rigidity, and submicron ultrastructure, which synergistically mature hiPSC-CMs rapidly within 30days. hiPSC-CMs matured on CMM exhibit systemic transcriptomic maturation toward an adult heart state, are aligned with high strain energy, metabolically rely on oxidative phosphorylation and fatty acid oxidation, and display enhanced redox handling capability, efficient calcium handling, and electrophysiological features of ventricular myocytes. Endothelin-1-induced pathological hypertrophy is mitigated on CMM, highlighting the role of a native cardiac microenvironment in withstanding hypertrophy progression. CMM is a convenient model for accelerated development of ventricular myocytes manifesting highly specialized cardiac-specific functions.

Adherens junctions stimulate and spatially guide integrin activation and extracellular matrix deposition.

Cadherins and integrins are intrinsically linked through the actin cytoskeleton and are largely responsible for the mechanical integrity and organization of tissues. We show that cadherin clustering stimulates and spatially guides integrin activation. Adherens junction (AJ)-associated integrin activation depends on locally generated tension and does not require extracellular matrix ligands. It leads to the creation of primed integrin clusters, which spatially determine where focal adhesions will form if ligands are present and where ligands will be deposited. AJs that display integrin activation are targeted by microtubules facilitating their disassembly via caveolin-based endocytosis, showing that integrin activation impacts the stability of the core cadherin complex. Thus, the interplay between cadherins and integrins is more intimate than what was once believed and is rooted in the capacity of active integrins to be stabilized via AJ-generated tension. Altogether, our data establish a mechanism of cross-regulation between cadherins and integrins.

Hydrogel Arrays Enable Increased Throughput for Screening Effects of Matrix Components and Therapeutics in 3D Tumor Models.

Cell-matrix interactions mediate complex physiological processes through biochemical, mechanical, and geometrical cues, influencing pathological changes and therapeutic responses. Accounting for matrix effects earlier in the drug development pipeline is expected to increase the likelihood of clinical success of novel therapeutics. Biomaterial-based strategies recapitulating specific tissue microenvironments in 3D cell culture exist but integrating these with the 2D culture methods primarily used for drug screening has been challenging. Thus, the protocol presented here details the development of methods for 3D culture within miniaturized biomaterial matrices in a multi-well plate format to facilitate integration with existing drug screening pipelines and conventional assays for cell viability. Since the matrix features critical for preserving clinically relevant phenotypes in cultured cells are expected to be highly tissue- and disease-specific, combinatorial screening of matrix parameters will be necessary to identify appropriate conditions for specific applications. The methods described here use a miniaturized culture format to assess cancer cell responses to orthogonal variation of matrix mechanics and ligand presentation. Specifically, this study demonstrates the use of this platform to investigate the effects of matrix parameters on the responses of patient-derived glioblastoma (GBM) cells to chemotherapy.