Mechanotransduction and extracellular matrix homeostasis

Creating a bionic scaffold via light-curing liquid crystal ink to reveal the role of osteoid-like microenvironment in osteogenesis

Osteoid plays a crucial role in directing cell behavior and osteogenesis through its unique characteristics, including viscoelasticity and liquid crystal (LC) state. Thus, integrating osteoid-like features into 3D printing scaffolds proves to be a promising approach for personalized bone repair. Despite extensive research on viscoelasticity, the role of LC state in bone repair has been largely overlooked due to the scarcity of suitable LC materials. Moreover, the intricate interplay between LC state and viscoelasticity in osteogenesis remains poorly understood. Here, we developed innovative hydrogel scaffolds with osteoid-like LC state and viscoelasticity using digital light processing with a custom LC ink. By utilizing these LC scaffolds as 3D research models, we discovered that LC state mediates high protein clustering to expose accessible RGD motifs to trigger cell-protein interactions and osteogenic differentiation, while viscoelasticity operates via mechanotransduction pathways. Additionally, our investigation revealed a synergistic effect between LC state and viscoelasticity, amplifying cell-protein interactions and osteogenic mechanotransduction processes. Furthermore, the interesting mechanochromic response observed in the LC hydrogel scaffolds suggests their potential application in mechanosensing. Our findings shed light on the mechanisms and synergistic effects of LC state and viscoelasticity in osteoid on osteogenesis, offering valuable insights for the biomimetic design of bone repair scaffolds.

Stimuli-responsive microcarriers and their application in tissue repair: A review of magnetic and electroactive microcarrier

Microcarrier applications have made great advances in tissue engineering in recent years, which can load cells, drugs, and bioactive factors. These microcarriers can be minimally injected into the defect to help reconstruct a good microenvironment for tissue repair. In order to achieve more ideal performance and face more complex tissue damage, an increasing amount of effort has been focused on microcarriers that can actively respond to external stimuli. These microcarriers have the functions of directional movement, targeted enrichment, material release control, and providing signals conducive to tissue repair. Given the high controllability and designability of magnetic and electroactive microcarriers, the research progress of these microcarriers is highlighted in this review. Their structure, function and applications, potential tissue repair mechanisms, and challenges are discussed. In summary, through the design with clinical translation ability, meaningful and comprehensive experimental characterization, and in-depth study and application of tissue repair mechanisms, stimuli-responsive microcarriers have great potential in tissue repair.

Dapansutrile OLT1177 suppresses foreign body response inflammation while preserving vascularisation of implanted materials

Mitigating inflammation associated with the foreign body response (FBR) remains a significant challenge in enhancing the performance of implantable medical devices. Current anti-inflammatory approaches aim to suppress implant fibrosis, the major outcome of the FBR, but also inadvertently inhibit beneficial immune signalling necessary for tissue healing and vascularization. In a previous study, we demonstrated the feasibility of 'selective' immunosuppression targeting the NLRP3 inflammasome using the small molecule inhibitor MCC950, leading to reduced implant fibrosis without compromising healing and leading to enhanced vascularization. However, the clinical potential of MCC950 is severely limited due to its failure to pass Phase I clinical safety trials. This has triggered substantial efforts to develop safer analogues of NLRP3 inhibitors. Dapansutrile (OLT1177) is emerging as a leading candidate amongst current NLRP3 inhibitors, demonstrating both safety and effectiveness in a growing number of clinical indications and Phase 2 trials. While the anti-inflammatory effects of OLT1177 have been shown, validation of these effects in the context of implanted materials and the FBR have not yet been demonstrated. In this study, we show OLT1177 possesses beneficial effects on key cell types which drive FBR outcomes, including macrophages, fibroblasts, and smooth muscle cells. Evaluation of OLT1177 in a 28 day subcutaneous implantation model showed OLT1177 reduced fibrotic capsule formation while promoting implant vascularization. Mechanistic studies revealed that this occurred through activation of early pro-angiogenic markers while suppressing late-stage anti-angiogenic markers. These findings establish OLT1177 as a promising therapeutic approach for mitigating implant fibrosis while supporting vascularisation, suggesting a highly promising selective immunosuppressive strategy for the FBR warranting further research to explore its optimal integration into medical materials and devices.

Modeling the mechanosensitive collective migration of cells on the surface and the interior of morphing soft tissues

Cellular contractility, migration, and extracellular matrix (ECM) mechanics are critical for a wide range of biological processes including embryonic development, wound healing, tissue morphogenesis, and regeneration. Even though the distinct response of cells near the tissue periphery has been previously observed in cell-laden microtissues, including faster kinetics and more prominent cell-ECM interactions, there are currently no models that can fully combine coupled surface and bulk mechanics and kinetics to recapitulate the morphogenic response of these constructs. Mailand et al. (Biophys J 117(5):975-986, 2019) had shown the importance of active elastocapillarity in cell-laden microtissues, but modeling the distinct mechanosensitive migration of cells on the periphery and the interior of highly deforming tissues has not been possible thus far, especially in the presence of active elastocapillary effects. This paper presents a framework for understanding the interplay between cellular contractility, migration, and ECM mechanics in dynamically morphing soft tissues accounting for distinct cellular responses in the bulk and the surface of tissues. The major novelty of this approach is that it enables modeling the distinct migratory and contractile response of cells residing on the tissue surface and the bulk, where concurrently the morphing soft tissues undergo large deformations driven by cell contractility. Additionally, the simulation results capture the changes in shape and cell concentration for wounded and intact microtissues, enabling the interpretation of experimental data. The numerical procedure that accounts for mechanosensitive stress generation, large deformations, diffusive migration in the bulk and a distinct mechanism for diffusive migration on deforming surfaces is inspired from recent work on bulk and surface poroelasticity of hydrogels involving elastocapillary effects, but in this work, a two-field weak form is proposed and is able to alleviate numerical instabilities that were observed in the original method that utilized a three-field mixed finite element formulation.

The application of nanomaterials in tumor therapy based on the regulation of mechanical properties

Mechanical properties, as crucial physical properties, have a significant impact on the occurrence, development, and metastasis of tumors. Regulating the mechanical properties of tumors to enhance their sensitivity to radiotherapy and chemotherapy has become an important strategy in the field of cancer treatment. Over the past few decades, nanomaterials have made remarkable progress in cancer therapy, either based on their intrinsic properties or as drug delivery carriers. However, the investigation of nanomaterials of mechanical regulation in tumor therapy is currently in its initial stages. The mechanical properties of nanomaterials themselves, drug carrier targeting, and regulation of the mechanical environment of tumor tissue have far-reaching effects on the efficient uptake of drugs and clinical tumor treatment. Therefore, this review aims to comprehensively summarize the applications and research progress of nanomaterials in tumor therapy based on the regulation of mechanical properties, in order to provide strong support for further research and the development of treatment strategies in this field.

De Novo Elastin Assembly Alleviates Development of Supravalvular Aortic Stenosis-Brief Report

BACKGROUND

A series of incurable cardiovascular disorders arise due to improper formation of elastin during development. Supravalvular aortic stenosis (SVAS), resulting from a haploinsufficiency of ELN, is caused by improper stress sensing by medial vascular smooth muscle cells, leading to progressive luminal occlusion and heart failure. SVAS remains incurable, as current therapies do not address the root issue of defective elastin.

METHODS

We use SVAS here as a model of vascular proliferative disease using both human induced pluripotent stem cell-derived vascular smooth muscle cells and developmental Eln+/- mouse models to establish de novo elastin assembly as a new therapeutic intervention.

RESULTS

We demonstrate mitigation of vascular proliferative abnormalities following de novo extracellular elastin assembly through the addition of the polyphenol epigallocatechin gallate to SVAS human induced pluripotent stem cell-derived vascular smooth muscle cells and in utero to Eln+/- mice.

CONCLUSIONS

We demonstrate de novo elastin deposition normalizes SVAS human induced pluripotent stem cell-derived vascular smooth muscle cell hyperproliferation and rescues hypertension and aortic mechanics in Eln+/- mice, providing critical preclinical findings for the future application of epigallocatechin gallate treatment in humans.

Impact of changes in collagen construction and molecular state on integrin - binding properties

The interaction between the integrin and collagen is important in cell adhesion and signaling. Collagen, as the main component of extracellular matrix, is a base material for tissue engineering constructs. In tissue engineering, the collagen structure and molecule state may be altered to varying degrees in the process of processing and utilizing, thereby affecting its biological properties. In this work, the impact of changes in collagen structure and molecular state on the binding properties of collagen to integrin α2β1 and integrin specific cell adhesion were explored. The results showed that the molecular structure of collagen is destroyed under the influence of heating, freeze-grinding and irradiation, the triple helix integrity is reduced and molecular breaking degree is increased. The binding ability of collagen to integrin α2β1 is increased with the increase of triple helix integrity and decays exponentially with the increase of molecular breaking degree. The collagen molecular state can also influences the binding ability of collagen to cellular receptor. The collagen fibrils binding to integrin α2β1 and HT1080 cells is stronger than to collagen monomolecule. Meanwhile, the hybrid fibril exhibits a different cellular receptor binding performance from corresponding single species collagen fibril. These findings provide ideas for the design and development of new collagen-based biomaterials and tissue engineering research.

Softening the tumor matrix through cholesterol depletion breaks the physical barrier for enhanced antitumor therapy

The tumor develops defense tactics, including conversing the mechanical characteristics of tumor cells and their surrounding environment. A recent study reported that cholesterol depletion stiffens tumor cells, which could enhance adaptive T-cell immunotherapy. However, it remains unclear whether reducing the cholesterol in tumor cells contributes to re-educating the stiff tumor matrix, which serves as a physical barrier against drug penetration. Herein, we found that depleting cholesterol from tumor cells can demolish the intratumor physical barrier by disrupting the mechanical signal transduction between tumor cells and the extracellular matrix through the destruction of lipid rafts. This disruption allows nanoparticles (H/S@hNP) to penetrate deeply, resulting in improved photodynamic treatment. Our research also indicates that cholesterol depletion can inhibit the epithelial-mesenchymal transition and repolarize tumor-associated macrophages from M2 to M1, demonstrating the essential role of cholesterol in tumor progression. Overall, this study reveals that a cholesterol-depleted, softened tumor matrix reduces the difficulty of drug penetration, leading to enhanced antitumor therapeutics.

FAK, vinculin, and talin control mechanosensitive YAP nuclear localization

Focal adhesions (FAs) are nanoscale complexes containing clustered integrin receptors and intracellular structural and signaling proteins that function as principal sites of mechanotransduction in part via promoting the nuclear translocation and activation of the transcriptional coactivator yes-associated protein (YAP). Knockdown of FA proteins such as focal adhesion kinase (FAK), talin, and vinculin can prevent YAP nuclear localization. However, the mechanism(s) of action remain poorly understood. Herein, we investigated the role of different functional domains in vinculin, talin, and FAK in regulating YAP nuclear localization. Using genetic or pharmacological inhibition of fibroblasts and human mesenchymal stem cells (hMSCs) adhering to deformable substrates, we find that disruption of vinculin-talin binding versus talin-FAK binding reduces YAP nuclear localization and transcriptional activity via different mechanisms. Disruption of vinculin-talin binding or knockdown of talin-1 reduces nuclear size, traction forces, and YAP nuclear localization. In contrast, disruption of the talin binding site on FAK or elimination of FAK catalytic activity did not alter nuclear size yet still prevented YAP nuclear localization and activity. These data support both nuclear tension-dependent and independent models for matrix stiffness-regulated YAP nuclear localization. Our results highlight the importance of vinculin-talin-FAK interactions at FAs of adherent cells, controlling YAP nuclear localization and activity.

Structure-Mechanics Principles and Mechanobiology of Fibrocartilage Pericellular Matrix: A Pivotal Role of Type V Collagen

The pericellular matrix (PCM) is the immediate microniche surrounding resident cells in various tissue types, regulating matrix turnover, cell-matrix cross-talk and disease initiation. This study elucidated the structure-mechanical properties and mechanobiological functions of the PCM in fibrocartilage, a family of connective tissues that sustain complex tensile and compressive loads in vivo. Studying the murine meniscus as the model tissue, we showed that fibrocartilage PCM contains thinner, random collagen fibrillar networks that entrap proteoglycans, a structure distinct from the densely packed, highly aligned collagen fibers in the bulk extracellular matrix (ECM). In comparison to the ECM, the PCM has a lower modulus and greater isotropy, but similar relative viscoelastic properties. In Col5a1 +/ D menisci, the reduction of collagen V, a minor collagen localized in the PCM, resulted in aberrant fibril thickening with increased heterogeneity. Consequently, the PCM exhibited a reduced modulus, loss of isotropy and faster viscoelastic relaxation. This disrupted PCM contributes to perturbed mechanotransduction of resident meniscal cells, as illustrated by reduced intracellular calcium signaling, as well as upregulated biosynthesis of lysyl oxidase and tenascin C. When cultured in vitro, Col5a1 +/ D meniscal cells synthesized a weakened nascent PCM, which had inferior properties towards protecting resident cells against applied tensile stretch. These findings underscore the PCM as a distinctive microstructure that governs fibrocartilage mechanobiology, and highlight the pivotal role of collagen V in PCM function. Targeting the PCM or its molecular constituents holds promise for enhancing not only meniscus regeneration and osteoarthritis intervention, but also addressing diseases across various fibrocartilaginous tissues.

Role of liver sinusoidal endothelial cell in metabolic dysfunction-associated fatty liver disease

Liver sinusoidal endothelial cells (LSECs) are highly specialized endothelial cells that represent the interface between blood cells on one side and hepatocytes on the other side. LSECs not only form a barrier within the hepatic sinus, but also play important physiological functions such as regulating hepatic vascular pressure, anti-inflammatory and anti-fibrotic. Pathologically, pathogenic factors can induce LSECs capillarization, that is, loss of fenestra and dysfunction, which are conducive to early steatosis, lay the foundation for the progression of metabolic dysfunction-associated fatty liver disease (MAFLD), and accelerate metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. The unique localization, phenotype, and function of LSECs make them potential candidates for reducing liver injury, inflammation, and preventing or reversing fibrosis in the future.

C. elegans touch receptor neurons direct mechanosensory complex organization via repurposing conserved basal lamina proteins

The sense of touch is conferred by the conjoint function of somatosensory neurons and skin cells. These cells meet across a gap filled by a basal lamina, an ancient structure found in metazoans. Using Caenorhabditis elegans, we investigate the composition and ultrastructure of the extracellular matrix at the epidermis and touch receptor neuron (TRN) interface. We show that membrane-matrix complexes containing laminin, nidogen, and the MEC-4 mechano-electrical transduction channel reside at this interface and are central to proper touch sensation. Interestingly, the dimensions and spacing of these complexes correspond with the discontinuous beam-like extracellular matrix structures observed in serial-section transmission electron micrographs. These complexes fail to coalesce in touch-insensitive extracellular matrix mutants and in dissociated neurons. Loss of nidogen reduces the density of mechanoreceptor complexes and the amplitude of the touch-evoked currents they carry. Thus, neuron-epithelium cell interfaces are instrumental in mechanosensory complex assembly and function. Unlike the basal lamina ensheathing the pharynx and body wall muscle, nidogen recruitment to the puncta along TRNs is not dependent upon laminin binding. MEC-4, but not laminin or nidogen, is destabilized by point mutations in the C-terminal Kunitz domain of the extracellular matrix component, MEC-1. These findings imply that somatosensory neurons secrete proteins that actively repurpose the basal lamina to generate special-purpose mechanosensory complexes responsible for vibrotactile sensing.

Side-view optical microscopy-assisted atomic force microscopy for thickness-dependent nanobiomechanics

The mechanical properties of biomaterials play an important role in regulating life processes, and thus accurately delineating the mechanical properties of biomaterials is critical to understand their functionality. Particularly, atomic force microscopy (AFM) has become a powerful and standard tool for characterizing and analyzing the nanomechanical properties of biomaterials, and providing a capability to visualize the thickness of the specimen during AFM-based force spectroscopy experiments benefits the biomedical applications of AFM. Here, we present a study of side-view optical microscopy-assisted AFM based on the integration of AFM and a detachable side-view optical microscopy module, which is able to image in real time the AFM indentation process from the side-view perspective and consequently facilitates the utilization of AFM-based indentation assay to precisely detect the mechanical properties of a specimen by taking its thickness into account. The effectiveness of side-view optical microscopy-assisted AFM was confirmed on four different types of biomaterial systems, including microfabricated structures, hydrogels, living cells, and cell spheroids, and the experimental results significantly show that the mechanical properties of samples at the micro/nanoscale are closely related to their thickness, vividly illustrating side-view optical microscopy-assisted AFM as a promising approach for accurate nanomechanics of biomaterial systems. The study provides additional possibilities for measuring the thickness-dependent nanomechanical properties of biomaterials by AFM, which will enable AFM-based force spectroscopy technology to address more biological issues with enhanced precision and will benefit the field of mechanobiology.

Impact of mechanical cues on key cell functions and cell-nanoparticle interactions

In recent years, it has been recognized that mechanical forces play an important regulative role in living organisms and possess a direct impact on crucial cell functions, ranging from cell growth to maintenance of tissue homeostasis. Advancements in mechanobiology have revealed the profound impact of mechanical signals on diverse cellular responses that are cell type specific. Notably, numerous studies have elucidated the pivotal role of different mechanical cues as regulatory factors influencing various cellular processes, including cell spreading, locomotion, differentiation, and proliferation. Given these insights, it is unsurprising that the responses of cells regulated by physical forces are intricately linked to the modulation of nanoparticle uptake kinetics and processing. This complex interplay underscores the significance of understanding the mechanical microenvironment in shaping cellular behaviors and, consequently, influencing how cells interact with and process nanoparticles. Nevertheless, our knowledge on how localized physical forces affect the internalization and processing of nanoparticles by cells remains rather limited. A significant gap exists in the literature concerning a systematic analysis of how mechanical cues might bias the interactions between nanoparticles and cells. Hence, our aim in this review is to provide a comprehensive and critical analysis of the existing knowledge regarding the influence of mechanical cues on the complicated dynamics of cell-nanoparticle interactions. By addressing this gap, we would like to contribute to a detailed understanding of the role that mechanical forces play in shaping the complex interplay between cells and nanoparticles.

Dynamic biaxial loading of vascular smooth muscle cell seeded tissue equivalents

An intricate reciprocal relationship exists between adherent synthetic cells and their extracellular matrix (ECM). These cells deposit, organize, and degrade the ECM, which in turn influences cell phenotype via responses that include sensitivity to changes in the mechanical state that arises from changes in external loading. Collagen-based tissue equivalents are commonly used as simple but revealing model systems to study cell-matrix interactions. Nevertheless, few quantitative studies report changes in the forces that the cells establish and maintain in such gels under dynamic loading. Moreover, most prior studies have been limited to uniaxial experiments despite many soft tissues, including arteries, experiencing multiaxial loading in vivo. To begin to close this gap, we use a custom biaxial bioreactor to subject collagen gels seeded with primary aortic smooth muscle cells to different biaxial loading conditions. These conditions include cyclic loading with different amplitudes as well as different mechanical constraints at the boundaries of a cruciform sample. Irrespective of loading amplitude and boundary condition, similar mean steady-state biaxial forces emerged across all tests. Additionally, stiffness-force relationships assessed via intermittent equibiaxial force-extension tests showed remarkable similarity for ranges of forces to which the cells adapted during periods of cyclic loading. Taken together, these findings are consistent with a load-mediated homeostatic response by vascular smooth muscle cells.

IKIP downregulates THBS1/FAK signaling to suppress migration and invasion by glioblastoma cells

Background

Inhibitor of NF-κB kinase-interacting protein (IKIP) is known to promote proliferation of glioblastoma (GBM) cells, but how it affects migration and invasion by those cells is unclear.

Methods

We compared levels of IKIP between glioma tissues and normal brain tissue in clinical samples and public databases. We examined the effects of IKIP overexpression and knockdown on the migration and invasion of GBM using transwell and wound healing assays, and we compared the transcriptomes under these different conditions to identify the molecular mechanisms involved.

Results

Based on data from our clinical samples and from public databases, IKIP was overexpressed in GBM tumors, and its expression level correlated inversely with survival. IKIP overexpression in GBM cells inhibited migration and invasion in transwell and wound healing assays, whereas IKIP knockdown exerted the opposite effects. IKIP overexpression in GBM cells that were injected into mouse brain promoted tumor growth but inhibited tumor invasion of surrounding tissue. The effects of IKIP were associated with downregulation of THBS1 mRNA and concomitant inhibition of THBS1/FAK signaling.

Conclusions

IKIP inhibits THBS1/FAK signaling to suppress migration and invasion of GBM cells.

Limiting extracellular matrix expansion in diet-induced obese mice reduces cardiac insulin resistance and prevents myocardial remodelling

OBJECTIVE

Obesity increases deposition of extracellular matrix (ECM) components of cardiac tissue. Since obesity aggregates with insulin resistance and heart disease, it is imperative to determine whether the increased ECM deposition contributes to this disease cluster. The hypotheses tested in this study were that in cardiac tissue of obese mice i) increased deposition of ECM components (collagens and hyaluronan) contributes to cardiac insulin resistance and that a reduction in these components improves cardiac insulin action and ii) reducing excess collagens and hyaluronan mitigates obesity-associated cardiac dysfunction.

METHODS

Genetic and pharmacological approaches that manipulated collagen and hyaluronan contents were employed in obese C57BL/6 mice fed a high fat (HF) diet. Cardiac insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp and cardiac function was measured by pressure-volume loop analysis in vivo.

RESULTS

We demonstrated a tight association between increased ECM deposition with cardiac insulin resistance. Increased collagen deposition by genetic deletion of matrix metalloproteinase 9 (MMP9) exacerbated cardiac insulin resistance and pirfenidone, a clinically available anti-fibrotic medication which inhibits collagen expression, improved cardiac insulin resistance in obese mice. Furthermore, decreased hyaluronan deposition by treatment with PEGylated human recombinant hyaluronidase PH20 (PEGPH20) improved cardiac insulin resistance in obese mice. These relationships corresponded to functional changes in the heart. Both PEGPH20 and pirfenidone treatment in obese mice ameliorated HF diet-induced abnormal myocardial remodelling.

CONCLUSION

Our results provide important new insights into the role of ECM deposition in the pathogenesis of cardiac insulin resistance and associated dysfunction in obesity of distinct mouse models. These findings support the novel therapeutic potential of targeting early cardiac ECM abnormalities in the prevention and treatment of obesity-related cardiovascular complications.

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.

Graphene Oxide Strengthens Gelatine through Non-Covalent Interactions with Its Amorphous Region

Graphene oxide (GO) has attracted huge attention in biomedical sciences due to its outstanding properties and potential applications. In this study, we synthesized GO using our recently developed 1-pyrenebutyric acid-assisted method and assessed how the GO as a filler influences the mechanical properties of GO-gelatine nanocomposite dry films as well as the cytotoxicity of HEK-293 cells grown on the GO-gelatine substrates. We show that the addition of GO (0-2%) improves the mechanical properties of gelatine in a concentration-dependent manner. The presence of 2 wt% GO increased the tensile strength, elasticity, ductility, and toughness of the gelatine films by about 3.1-, 2.5-, 2-, and 8-fold, respectively. Cell viability, apoptosis, and necrosis analyses showed no cytotoxicity from GO. Furthermore, we performed circular dichroism, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses to decipher the interactions between GO and gelatine. The results show, for the first time, that GO enhances the mechanical properties of gelatine by forming non-covalent intermolecular interactions with gelatine at its amorphous or disordered regions. We believe that our findings will provide new insight and help pave the way for potential and wide applications of GO in tissue engineering and regenerative biomedicine.

Genetic disruption of ATAT1 causes RhoA downregulation through abnormal truncation of C/EBPβ

Microtubule acetylation has been shown to regulate actin filament dynamics by modulating signaling pathways that control actin organization, although the precise mechanisms remain unknown. In this study, we found that the downregulation of microtubule acetylation via the disruption ATAT1 (which encodes α-tubulin N-acetyltransferase 1) inhibited the expression of RhoA, a small GTPase involved in regulating the organization of actin filaments and the formation of stress fibers. Analysis of RHOA promoter and chromatin immunoprecipitation assays revealed that C/EBPβ is a major regulator of RHOA expression. Interestingly, the majority of C/EBPβ in ATAT1 knockout (KO) cells was found in the nucleus as a 27-kDa fragment (referred to as C/EBPβp27) lacking the N-terminus of C/EBPβ. Overexpression of a gene encoding a C/EBPβp27-mimicking protein via an N-terminal deletion in C/EBPβ led to competitive binding with wild-type C/EBPβ at the C/EBPβ binding site in the RHOA promoter, resulting in a significant decrease of RHOA expression. We also found that cathepsin L (CTSL), which is overexpressed in ATAT1 KO cells, is responsible for C/EBPβp27 formation in the nucleus. Treatment with a CTSL inhibitor led to the restoration of RHOA expression by downregulation of C/EBPβp27 and the invasive ability of ATAT1 KO MDA-MB-231 breast cancer cells. Collectively, our findings suggest that the downregulation of microtubule acetylation associated with ATAT1 deficiency suppresses RHOA expression by forming C/EBPβp27 in the nucleus through CTSL. We propose that CTSL and C/EBPβp27 may represent a novel therapeutic target for breast cancer treatment. [BMB Reports 2024; 57(6): 293-298].

Enhancing chondrogenic differentiation of mesenchymal stem cells through synergistic effects of cellulose nanocrystals and plastic compression in collagen-based hydrogel for cartilage formation

Collagen-based (COL) hydrogels could be a promising treatment option for injuries to the articular cartilage (AC) becuase of their similarity to AC native extra extracellular matrix. However, the high hydration of COL hydrogels poses challenges for AC's mechanical properties. To address this, we developed a hydrogel platform that incorporating cellulose nanocrystals (CNCs) within COL and followed by plastic compression (PC) procedure to expel the excessive fluid out. This approach significantly improved the mechanical properties of the hydrogels and enhanced the chondrogenic differentiation of mesenchymal stem cells (MSCs). Radially confined PC resulted in higher collagen fibrillar densities together with reducing fibril-fibril distances. Compressed hydrogels containing CNCs exhibited the highest compressive modulus and toughness. MSCs encapsulated in these hydrogels were initially affected by PC, but their viability improved after 7 days. Furthermore, the morphology of the cells and their secretion of glycosaminoglycans (GAGs) were positively influenced by the compressed COL-CNC hydrogel. Our findings shed light on the combined effects of PC and CNCs in improving the physical and mechanical properties of COL and their role in promoting chondrogenesis.

Hierarchical Design of Tissue-Mimetic Fibrillar Hydrogel Scaffolds

Most tissues of the human body present hierarchical fibrillar extracellular matrices (ECMs) that have a strong influence over their physicochemical properties and biological behavior. Of great interest is the introduction of this fibrillar structure to hydrogels, particularly due to the water-rich composition, cytocompatibility, and tunable properties of this class of biomaterials. Here, the main bottom-up fabrication strategies for the design and production of hierarchical biomimetic fibrillar hydrogels and their most representative applications in the fields of tissue engineering and regenerative medicine are reviewed. For example, the controlled assembly/arrangement of peptides, polymeric micelles, cellulose nanoparticles (NPs), and magnetically responsive nanostructures, among others, into fibrillar hydrogels is discussed, as well as their potential use as fibrillar-like hydrogels (e.g., those from cellulose NPs) with key biofunctionalities such as electrical conductivity or remote stimulation. Finally, the major remaining barriers to the clinical translation of fibrillar hydrogels and potential future directions of research in this field are discussed.

Heat-inducible CAR-T overcomes adverse mechanical tumor microenvironment in a 3D bioprinted glioblastoma model

Glioblastoma (GBM) presents a significant therapeutic challenge due to the limited efficacy of existing treatments. Chimeric antigen receptor (CAR) T-cell therapy offers promise, but its potential in solid tumors like GBM is undermined by the physical barrier posed by the extracellular matrix (ECM). To address the inadequacies of traditional 2D cell culture, animal models, and Matrigel-based 3D culture in mimicking the mechanical characteristics of tumor tissues, we employed biomaterials and digital light processing-based 3D bioprinting to fabricate biomimetic tumor models with finely tunable ECM stiffness independent of ECM composition. Our results demonstrated that increased material stiffness markedly impeded CAR-T cell penetration and tumor cell cytotoxicity in GBM models. The 3D bioprinted models enabled us to examine the influence of ECM stiffness on CAR-T cell therapy effectiveness, providing a clinically pertinent evaluation tool for CAR-T cell development in stiff solid tumors. Furthermore, we developed an innovative heat-inducible CAR-T cell therapy, effectively overcoming the challenges posed by the stiff tumor microenvironment.

Unveiling cellular and molecular aspects of ascending thoracic aortic aneurysms and dissections

Ascending thoracic aortic aneurysm (ATAA) remains a significant medical concern, with its asymptomatic nature posing diagnostic and monitoring challenges, thereby increasing the risk of aortic wall dissection and rupture. Current management of aortic repair relies on an aortic diameter threshold. However, this approach underestimates the complexity of aortic wall disease due to important knowledge gaps in understanding its underlying pathologic mechanisms.Since traditional risk factors cannot explain the initiation and progression of ATAA leading to dissection, local vascular factors such as extracellular matrix (ECM) and vascular smooth muscle cells (VSMCs) might harbor targets for early diagnosis and intervention. Derived from diverse embryonic lineages, VSMCs exhibit varied responses to genetic abnormalities that regulate their contractility. The transition of VSMCs into different phenotypes is an adaptive response to stress stimuli such as hemodynamic changes resulting from cardiovascular disease, aging, lifestyle, and genetic predisposition. Upon longer exposure to stress stimuli, VSMC phenotypic switching can instigate pathologic remodeling that contributes to the pathogenesis of ATAA.This review aims to illuminate the current understanding of cellular and molecular characteristics associated with ATAA and dissection, emphasizing the need for a more nuanced comprehension of the impaired ECM-VSMC network.

The influence of physical and spatial substrate characteristics on endothelial cells

Cardiovascular diseases are a main cause of death worldwide, leading to a growing demand for medical devices to treat this patient group. Central to the engineering of such devices is a good understanding of the biology and physics of cell-surface interactions. In existing blood-contacting devices, such as vascular grafts, the interaction between blood, cells, and material is one of the main limiting factors for their long-term durability. An improved understanding of the material's chemical- and physical properties as well as its structure all play a role in how endothelial cells interact with the material surface. This review provides an overview of how different surface structures influence endothelial cell responses and what is currently known about the underlying mechanisms that guide this behavior. The structures reviewed include decellularized matrices, electrospun fibers, pillars, pits, and grated surfaces.

FAM19A5 in vascular aging and osteoporosis: Mechanisms and the "calcification paradox"

Aging induces a progressive decline in the vasculature's structure and function. Vascular aging is a determinant factor for vascular ailments in the elderly. FAM19A5, a recently identified adipokine, has demonstrated involvement in multiple vascular aging-related pathologies, including atherosclerosis, cardio-cerebral vascular diseases and cognitive deficits. This review summarizes the current understanding of FAM19A5' role and explores its putative regulatory mechanisms in various aging-related disorders, including cardiovascular diseases (CVDs), metabolic diseases, neurodegenerative diseases and malignancies. Importantly, we provide novel insights into the underlying therapeutic value of FAM19A5 in osteoporosis. Finally, we outline future perspectives on the diagnostic and therapeutic potential of FAM19A5 in vascular aging-related diseases.

Deposited footprints let cells switch between confined, oscillatory, and exploratory migration

For eukaryotic cells to heal wounds, respond to immune signals, or metastasize, they must migrate, often by adhering to extracellular matrix (ECM). Cells may also deposit ECM components, leaving behind a footprint that influences their crawling. Recent experiments showed that some epithelial cell lines on micropatterned adhesive stripes move persistently in regions they have previously crawled over, where footprints have been formed, but barely advance into unexplored regions, creating an oscillatory migration of increasing amplitude. Here, we explore through mathematical modeling how footprint deposition and cell responses to footprint combine to allow cells to develop oscillation and other complex migratory motions. We simulate cell crawling with a phase field model coupled to a biochemical model of cell polarity, assuming local contact with the deposited footprint activates Rac1, a protein that establishes the cell's front. Depending on footprint deposition rate and response to the footprint, cells on micropatterned lines can display many types of motility, including confined, oscillatory, and persistent motion. On two-dimensional (2D) substrates, we predict a transition between cells undergoing circular motion and cells developing an exploratory phenotype. Small quantitative changes in a cell's interaction with its footprint can completely alter exploration, allowing cells to tightly regulate their motion, leading to different motility phenotypes (confined vs. exploratory) in different cells when deposition or sensing is variable from cell to cell. Consistent with our computational predictions, we find in earlier experimental data evidence of cells undergoing both circular and exploratory motion.

Stiffness Modulation and Pulsatile Release in Dual Responsive Hydrogels

Inspired by nature, self-regulation can be introduced in synthetic hydrogels by incorporating chemo-mechanical signals or coupled chemical reactions to maintain or adapt the material's physico-chemical properties when exposed to external triggers. In this work, we present redox and light dual stimuli responsive hydrogels capable of rapidly adapting the polymer crosslinking network while maintaining hydrogel stability. Upon irradiation with UV light, polymer hydrogels containing redox responsive disulfide crosslinks and light responsive ortho-nitrobenzyl moieties show a release of payload accompanied by adaptation of the hydrogel network towards higher stiffness due to in situ crosslinking by S-nitrosylation. Whereas the hydrogel design allows the network to either become softer in presence of reducing agent glutathione or stiffer upon UV irradiation, simultaneous application of both stimuli induces network self-regulation resulting in a pulsatile form of payload release from the hydrogel. Finally, adaptive stiffness was used to make tunable hydrogels as substrates for different cell lines.

YAP/TAZ Drive Agrin-Matrix Metalloproteinase 12-Mediated Diabetic Skin Wound Healing

Macroscopic loss of extracellular matrix can lead to chronic defects in skin wound healing, but supplementation of extracellular matrix holds promise for facilitating wound closure, particularly in diabetic wound healing. We recently showed that the extracellular matrix proteoglycan agrin accelerates cutaneous wound healing by improving mechanoperception of migrating keratinocytes and allowing them to respond to mechanical stresses through matrix metalloproteinase 12 (MMP12). RNA-sequencing analysis revealed that in addition to a disorganized extracellular matrix, agrin-depleted skin cells have impaired YAP/TAZ transcriptional outcomes, leading us to hypothesize that YAP/TAZ, as central mechanosensors, drive the functionality of agrin-MMP12 signaling during cutaneous wound repair. In this study, we demonstrate that agrin activates YAP/TAZ during migration of keratinocytes after wounding in vitro and in vivo. Mechanistically, YAP/TAZ sustain agrin and MMP12 protein expression during migration after wounding through positive feedback. YAP/TAZ silencing abolishes agrin-MMP12-mediated force recognition and geometrical constraints. Importantly, soluble agrin therapy accelerates wound closure in diabetic mouse models by engaging MMP12-YAP. Because patients with diabetic foot ulcers and impaired wound healing have reduced expression of agrin-MMP12 that correlates with YAP/TAZ inactivation, we propose that timely activation of YAP/TAZ by soluble agrin therapy can accentuate mechanobiological microenvironments for efficient wound healing, under normal and diabetic conditions.

Deposited footprints let cells switch between confined, oscillatory, and exploratory migration

For eukaryotic cells to heal wounds, respond to immune signals, or metastasize, they must migrate, often by adhering to extracellular matrix. Cells may also deposit extracellular matrix components, leaving behind a footprint that influences their crawling. Recent experiments showed that some epithelial cells on micropatterned adhesive stripes move persistently in regions they have previously crawled over, where footprints have been formed, but barely advance into unexplored regions, creating an oscillatory migration of increasing amplitude. Here, we explore through mathematical modeling how footprint deposition and cell responses to footprint combine to allow cells to develop oscillation and other complex migratory motions. We simulate cell crawling with a phase field model coupled to a biochemical model of cell polarity, assuming local contact with the deposited footprint activates Rac1, a protein that establishes the cell's front. Depending on footprint deposition rate and response to the footprint, cells on micropatterned lines can display many types of motility, including confined, oscillatory, and persistent motion. On two-dimensional substrates, we predict a transition between cells undergoing circular motion and cells developing an exploratory phenotype. Small quantitative changes in a cell's interaction with its footprint can completely alter exploration, allowing cells to tightly regulate their motion, leading to different motility phenotypes (confined vs exploratory) in different cells when deposition or sensing is variable from cell to cell. Consistent with our computational predictions, we find in earlier experimental data evidence of cells undergoing both circular and exploratory motion.

Fibroblasts' secretome from calcified and non-calcified dermis in Pseudoxanthoma elasticum differently contributes to elastin calcification

Pseudoxanthoma elasticum (PXE) is a rare disease characterized by ectopic calcification, however, despite the widely spread effect of pro/anti-calcifying systemic factors associated with this genetic metabolic condition, it is not known why elastic fibers in the same patient are mainly fragmented or highly mineralized in clinically unaffected (CUS) and affected (CAS) skin, respectively. Cellular morphology and secretome are investigated in vitro in CUS and CAS fibroblasts. Here we show that, compared to CUS, CAS fibroblasts exhibit: a) differently distributed and organized focal adhesions and stress fibers; b) modified cell-matrix interactions (i.e., collagen gel retraction); c) imbalance between matrix metalloproteinases and tissue inhibitor of metalloproteinases; d) differentially expressed pro- and anti-calcifying proteoglycans and elastic-fibers associated glycoproteins. These data emphasize that in the development of pathologic mineral deposition fibroblasts play an active role altering the stability of elastic fibers and of the extracellular matrix milieu creating a local microenvironment guiding the level of matrix remodeling at an extent that may lead to degradation (in CUS) or to degradation and calcification (in CAS) of the elastic component. In conclusion, this study contributes to a better understanding of the mechanisms of the mineral deposition that can be also associated with several inherited or age-related diseases (e.g., diabetes, atherosclerosis, chronic kidney diseases).

Effects of mechanical ventilation on the interstitial extracellular matrix in healthy lungs and lungs affected by acute respiratory distress syndrome: a narrative review

BACKGROUND

Mechanical ventilation, a lifesaving intervention in critical care, can lead to damage in the extracellular matrix (ECM), triggering inflammation and ventilator-induced lung injury (VILI), particularly in conditions such as acute respiratory distress syndrome (ARDS). This review discusses the detailed structure of the ECM in healthy and ARDS-affected lungs under mechanical ventilation, aiming to bridge the gap between experimental insights and clinical practice by offering a thorough understanding of lung ECM organization and the dynamics of its alteration during mechanical ventilation.

MAIN TEXT

Focusing on the clinical implications, we explore the potential of precise interventions targeting the ECM and cellular signaling pathways to mitigate lung damage, reduce inflammation, and ultimately improve outcomes for critically ill patients. By analyzing a range of experimental studies and clinical papers, particular attention is paid to the roles of matrix metalloproteinases (MMPs), integrins, and other molecules in ECM damage and VILI. This synthesis not only sheds light on the structural changes induced by mechanical stress but also underscores the importance of cellular responses such as inflammation, fibrosis, and excessive activation of MMPs.

CONCLUSIONS

This review emphasizes the significance of mechanical cues transduced by integrins and their impact on cellular behavior during ventilation, offering insights into the complex interactions between mechanical ventilation, ECM damage, and cellular signaling. By understanding these mechanisms, healthcare professionals in critical care can anticipate the consequences of mechanical ventilation and use targeted strategies to prevent or minimize ECM damage, ultimately leading to better patient management and outcomes in critical care settings.

Dental Pulp Stem Cells Modulate Inflammasome Pathway and Collagen Deposition of Dermal Fibroblasts

Fibrosis is a pathological condition consisting of a delayed deposition and remodeling of the extracellular matrix (ECM) by fibroblasts. This deregulation is mostly triggered by a chronic stimulus mediated by pro-inflammatory cytokines, such as TNF-α and IL-1, which activate fibroblasts. Due to their anti-inflammatory and immunosuppressive potential, dental pulp stem cells (DPSCs) could affect fibrotic processes. This study aims to clarify if DPSCs can affect fibroblast activation and modulate collagen deposition. We set up a transwell co-culture system, where DPSCs were seeded above the monolayer of fibroblasts and stimulated with LPS or a combination of TNF-α and IL-1β and quantified a set of genes involved in inflammasome activation or ECM deposition. Cytokines-stimulated co-cultured fibroblasts, compared to unstimulated ones, showed a significant increase in the expression of IL-1β, IL-6, NAIP, AIM2, CASP1, FN1, and TGF-β genes. At the protein level, IL-1β and IL-6 release as well as FN1 were increased in stimulated, co-cultured fibroblasts. Moreover, we found a significant increase of MMP-9 production, suggesting a role of DPSCs in ECM remodeling. Our data seem to suggest a crosstalk between cultured fibroblasts and DPSCs, which seems to modulate genes involved in inflammasome activation, ECM deposition, wound healing, and fibrosis.

The NDR family of kinases: essential regulators of aging

Aging is defined as a progressive decline of cognitive and physiological functions over lifetime. Since the definition of the nine hallmarks of aging in 2013 by López-Otin, numerous studies have attempted to identify the main regulators and contributors in the aging process. One interesting group of proteins whose participation has been implicated in several aging hallmarks are the nuclear DBF2-related (NDR) family of serine-threonine AGC kinases. They are one of the core components of the Hippo signaling pathway and include NDR1, NDR2, LATS1 and LATS2 in mammals, along with its highly conserved metazoan orthologs; Trc in Drosophila melanogaster, SAX-1 in Caenorhabditis elegans, CBK1, DBF20 in Saccharomyces cerevisiae and orb6 in Saccharomyces pombe. These kinases have been independently linked to the regulation of widely diverse cellular processes disrupted during aging such as the cell cycle progression, transcription, intercellular communication, nutrient homeostasis, autophagy, apoptosis, and stem cell differentiation. However, a comprehensive overview of the state-of-the-art knowledge regarding the post-translational modifications of and by NDR kinases in aging has not been conducted. In this review, we summarize the current understanding of the NDR family of kinases, focusing on their relevance to various aging hallmarks, and emphasize the growing body of evidence that suggests NDR kinases are essential regulators of aging across species.

Integrin αVβ3 antagonist-c(RGDyk) peptide attenuates the progression of ossification of the posterior longitudinal ligament by inhibiting osteogenesis and angiogenesis

BACKGROUND

Ossification of the posterior longitudinal ligament (OPLL), an emerging heterotopic ossification disease, causes spinal cord compression, resulting in motor and sensory dysfunction. The etiology of OPLL remains unclear but may involve integrin αVβ3 regulating the process of osteogenesis and angiogenesis. In this study, we focused on the role of integrin αVβ3 in OPLL and explored the underlying mechanism by which the c(RGDyk) peptide acts as a potent and selective integrin αVβ3 inhibitor to inhibit osteogenesis and angiogenesis in OPLL.

METHODS

OPLL or control ligament samples were collected in surgery. For OPLL samples, RNA-sequencing results revealed activation of the integrin family, particularly integrin αVβ3. Integrin αVβ3 expression was detected by qPCR, Western blotting, and immunohistochemical analysis. Fluorescence microscopy was used to observe the targeted inhibition of integrin αVβ3 by the c(RGDyk) peptide on ligaments fibroblasts (LFs) derived from patients with OPLL and endothelial cells (ECs). The effect of c(RGDyk) peptide on the ossification of pathogenic LFs was detected using qPCR, Western blotting. Alkaline phosphatase staining or alizarin red staining were used to test the osteogenic capability. The effect of the c(RGDyk) peptide on angiogenesis was determined by EC migration and tube formation assays. The effects of the c(RGDyk) peptide on heterotopic bone formation were evaluated by micro-CT, histological, immunohistochemical, and immunofluorescence analysis in vivo.

RESULTS

The results indicated that after being treated with c(RGDyk), the osteogenic differentiation of LFs was significantly decreased. Moreover, the c(RGDyk) peptide inhibited the migration of ECs and thus prevented the nutritional support required for osteogenesis. Furthermore, the c(RGDyk) peptide inhibited ectopic bone formation in mice. Mechanistic analysis revealed that c(RGDyk) peptide could inhibit osteogenesis and angiogenesis in OPLL by targeting integrin αVβ3 and regulating the FAK/ERK pathway.

CONCLUSIONS

Therefore, the integrin αVβ3 appears to be an emerging therapeutic target for OPLL, and the c(RGDyk) peptide has dual inhibitory effects that may be valuable for the new therapeutic strategy of OPLL.

Multiscale computational model of aortic remodeling following postnatal disruption of TGFβ signaling

The healthy adult aorta is a remarkably resilient structure, able to resist relentless cardiac-induced and hemodynamic loads under normal conditions. Fundamental to such mechanical homeostasis is the mechano-sensitive cell signaling that controls gene products and thus the structural integrity of the wall. Mouse models have shown that smooth muscle cell-specific disruption of transforming growth factor-beta (TGFβ) signaling during postnatal development compromises this resiliency, rendering the aortic wall susceptible to aneurysm and dissection under normal mechanical loading. By contrast, disruption of such signaling in the adult aorta appears to introduce a vulnerability that remains hidden under normal loading, but manifests under increased loading as experienced during hypertension. We present a multiscale (transcript to tissue) computational model to examine possible reasons for compromised mechanical homeostasis in the adult aorta following reduced TGFβ signaling in smooth muscle cells.

Advances in high throughput cell culture technologies for therapeutic screening and biological discovery applications

Cellular phenotypes and functional responses are modulated by the signals present in their microenvironment, including extracellular matrix (ECM) proteins, tissue mechanical properties, soluble signals and nutrients, and cell-cell interactions. To better recapitulate and analyze these complex signals within the framework of more physiologically relevant culture models, high throughput culture platforms can be transformative. High throughput methodologies enable scientists to extract increasingly robust and broad datasets from individual experiments, screen large numbers of conditions for potential hits, better qualify and predict responses for preclinical applications, and reduce reliance on animal studies. High throughput cell culture systems require uniformity, assay miniaturization, specific target identification, and process simplification. In this review, we detail the various techniques that researchers have used to face these challenges and explore cellular responses in a high throughput manner. We highlight several common approaches including two-dimensional multiwell microplates, microarrays, and microfluidic cell culture systems as well as unencapsulated and encapsulated three-dimensional high throughput cell culture systems, featuring multiwell microplates, micromolds, microwells, microarrays, granular hydrogels, and cell-encapsulated microgels. We also discuss current applications of these high throughput technologies, namely stem cell sourcing, drug discovery and predictive toxicology, and personalized medicine, along with emerging opportunities and future impact areas.

Advancements in self-assembling peptides: Bridging gaps in 3D cell culture and electronic device fabrication

Self-assembling peptides (SAPs) show promise in creating synthetic microenvironments that regulate cellular function and tissue repair. Also, the precise π-π interactions and hydrogen bonding within self-assembled peptide structures enable the creation of quantum confined structures, leading to reduced band gaps and the emergence of semiconductor properties within the superstructures. This review emphasizes the need for standardized 3D cell culture methods and electronic devices based on SAPs for monitoring cell communication and controlling cell surface morphology. Additionally, the gap in understanding the relationship between SAP peptide sequences and nanostructures is highlighted, underscoring the importance of optimizing peptide deposition parameters, which affect charge transport and bioactivity due to varying morphologies. The potential of peptide nanofibers as extracellular matrix mimics and the introduction of the zone casting method for improved film deposition are discussed within this review, aiming to bridge knowledge gaps and offer insights into fields like tissue engineering and materials science, with the potential for groundbreaking applications at the interface of biology and materials engineering.

Generation of Anterior Segment of the Eye Cells from hiPSCs in Microfluidic Platforms

Ophthalmic diseases affect many people, causing partial or total loss of vision and a reduced quality of life. The anterior segment of the eye accounts for nearly half of all visual impairment that can lead to blindness. Therefore, there is a growing demand for ocular research and regenerative medicine that specifically targets the anterior segment to improve vision quality. This study aims to generate a microfluidic platform for investigating the formation of the anterior segment of the eye derived from human induced pluripotent stem cells (hiPSC) under various spatial-mechanoresponsive conditions. Microfluidic platforms are developed to examine the effects of dynamic conditions on the generation of hiPSCs-derived ocular organoids. The differentiation protocol is validated, and mechanoresponsive genes are identified through transcriptomic analysis. Several culture strategies is implemented for the anterior segment of eye cells in a microfluidic chip. hiPSC-derived cells showed anterior eye cell characteristics in mRNA and protein expression levels under dynamic culture conditions. The expression levels of yes-associated protein and transcriptional coactivator PDZ binding motif (YAP/TAZ) and PIEZO1, varied depending on the differentiation and growth conditions of the cells, as well as the metabolomic profiles under dynamic culture conditions.

Personalized coronary and myocardial blood flow models incorporating CT perfusion imaging and synthetic vascular trees

Computational simulations of coronary artery blood flow, using anatomical models based on clinical imaging, are an emerging non-invasive tool for personalized treatment planning. However, current simulations contend with two related challenges - incomplete anatomies in image-based models due to the exclusion of arteries smaller than the imaging resolution, and the lack of personalized flow distributions informed by patient-specific imaging. We introduce a data-enabled, personalized and multi-scale flow simulation framework spanning large coronary arteries to myocardial microvasculature. It includes image-based coronary anatomies combined with synthetic vasculature for arteries below the imaging resolution, myocardial blood flow simulated using Darcy models, and systemic circulation represented as lumped-parameter networks. We propose an optimization-based method to personalize multiscale coronary flow simulations by assimilating clinical CT myocardial perfusion imaging and cardiac function measurements to yield patient-specific flow distributions and model parameters. Using this proof-of-concept study on a cohort of six patients, we reveal substantial differences in flow distributions and clinical diagnosis metrics between the proposed personalized framework and empirical methods based purely on anatomy; these errors cannot be predicted a priori. This suggests virtual treatment planning tools would benefit from increased personalization informed by emerging imaging methods.

Unsolved morphogenesis problems and the hidden order

In this work, the morphogenesis mechanisms are considered from the complexity perspective. It is shown that both morphogenesis and the functioning of organs should be unstable in the case of short-range interaction potentials. The repeatability of forms during evolution is a strong argument for its directionality. The formation of organs during evolution can occur only in the presence of a priori information about the structure of such an organ. The focus of the discussion is not merely on constraining potential possibilities but on the concept of directed evolution itself. A morphogenesis model was constructed based on nontrivial quantum effects. These interaction effects between biologically important molecules ensure the accurate synthesis of cells, tissues, and organs.

Comparative analysis of traction forces in normal and glaucomatous trabecular meshwork cells within a 3D, active fluid-structure interaction culture environment

This study presents a 3D in vitro cell culture model, meticulously 3D printed to replicate the conventional aqueous outflow pathway anatomical structure, facilitating the study of trabecular meshwork (TM) cellular responses under glaucomatous conditions. Glaucoma affects TM cell functionality, leading to extracellular matrix (ECM) stiffening, enhanced cell-ECM adhesion, and obstructed aqueous humor outflow. Our model, reconstructed from polyacrylamide gel with elastic moduli of 1.5 and 21.7 kPa, is based on serial block-face scanning electron microscopy images of the outflow pathway. It allows for quantifying 3D, depth-dependent, dynamic traction forces exerted by both normal and glaucomatous TM cells within an active fluid-structure interaction (FSI) environment. In our experimental design, we designed two scenarios: a control group with TM cells observed over 20 hours without flow (static setting), focusing on intrinsic cellular contractile forces, and a second scenario incorporating active FSI to evaluate its impact on traction forces (dynamic setting). Our observations revealed that active FSI results in higher traction forces (normal: 1.83-fold and glaucoma: 2.24-fold) and shear strains (normal: 1.81-fold and glaucoma: 2.41-fold), with stiffer substrates amplifying this effect. Glaucomatous cells consistently exhibited larger forces than normal cells. Increasing gel stiffness led to enhanced stress fiber formation in TM cells, particularly in glaucomatous cells. Exposure to active FSI dramatically altered actin organization in both normal and glaucomatous TM cells, particularly affecting cortical actin stress fiber arrangement. This model while preliminary offers a new method in understanding TM cell biomechanics and ECM stiffening in glaucoma, highlighting the importance of FSI in these processes. STATEMENT OF SIGNIFICANCE: This pioneering project presents an advanced 3D in vitro model, meticulously replicating the human trabecular meshwork's anatomy for glaucoma research. It enables precise quantification of cellular forces in a dynamic fluid-structure interaction, a leap forward from existing 2D models. This advancement promises significant insights into trabecular meshwork cell biomechanics and the stiffening of the extracellular matrix in glaucoma, offering potential pathways for innovative treatments. This research is positioned at the forefront of ocular disease study, with implications that extend to broader biomedical applications.

Regenerative Anterior Cruciate Ligament Healing in Youth and Adolescent Athletes: The Emerging Age of Recovery Science

Anterior cruciate ligament (ACL) injuries mainly arise from non-contact mechanisms during sport performance, with most injuries occurring among youth or adolescent-age athletes, particularly females. The growing popularity of elite-level sport training has increased the total volume, intensity and frequency of exercise and competition loading to levels that may exceed natural healing capacity. Growing evidence suggests that the prevailing mechanism that leads to non-contact ACL injury from sudden mechanical fatigue failure may be accumulated microtrauma. Given the consequences of primary ACL injury on the future health and quality of life of youth and adolescent athletes, the objective of this review is to identify key "recovery science" factors that can help prevent these injuries. Recovery science is any aspect of sports training (type, volume, intensity, frequency), nutrition, and sleep/rest or other therapeutic modalities that may prevent the accumulated microtrauma that precedes non-contact ACL injury from sudden mechanical fatigue failure. This review discusses ACL injury epidemiology, current surgical efficacy, the native ACL vascular network, regional ACL histological complexities such as the entheses and crimp patterns, extracellular matrix remodeling, the concept of causal histogenesis, exercise dosage and ligament metabolism, central nervous system reorganization post-ACL rupture, homeostasis regulation, nutrition, sleep and the autonomic nervous system. Based on this information, now may be a good time to re-think primary ACL injury prevention strategies with greater use of modified sport training, improved active recovery that includes well-planned nutrition, and healthy sleep patterns. The scientific rationale behind the efficacy of regenerative orthobiologics and concomitant therapies for primary ACL injury prevention in youth and adolescent athletes are also discussed.

A two-phase thin-film model for cell-induced gel contraction incorporating osmotic effects

We present a mathematical model of an experiment in which cells are cultured within a gel, which in turn floats freely within a liquid nutrient medium. Traction forces exerted by the cells on the gel cause it to contract over time, giving a measure of the strength of these forces. Building upon our previous work (Reoch et al. in J Math Biol 84(5):31, 2022), we exploit the fact that the gels used frequently have a thin geometry to obtain a reduced model for the behaviour of a thin, two-dimensional cell-seeded gel. We find that steady-state solutions of the reduced model require the cell density and volume fraction of polymer in the gel to be spatially uniform, while the gel height may vary spatially. If we further assume that all three of these variables are initially spatially uniform, this continues for all time and the thin film model can be further reduced to solving a single, non-linear ODE for gel height as a function of time. The thin film model is further investigated for both spatially-uniform and varying initial conditions, using a combination of analytical techniques and numerical simulations. We show that a number of qualitatively different behaviours are possible, depending on the composition of the gel (i.e., the chemical potentials) and the strength of the cell traction forces. However, unlike in the earlier one-dimensional model, we do not observe cases where the gel oscillates between swelling and contraction. For the case of initially uniform cell and gel density, our model predicts that the relative change in the gels' height and length are equal, which justifies an assumption previously used in the work of Stevenson et al. (Biophys J 99(1):19-28, 2010). Conversely, however, even for non-uniform initial conditions, we do not observe cases where the length of the gel changes whilst its height remains constant, which have been reported in another model of osmotic swelling by Trinschek et al. (AIMS Mater Sci 3(3):1138-1159, 2016; Phys Rev Lett 119:078003, 2017).

Focal Adhesion's Role in Cardiomyocytes Function: From Cardiomyogenesis to Mechanotransduction

Mechanotransduction refers to the ability of cells to sense mechanical stimuli and convert them into biochemical signals. In this context, the key players are focal adhesions (FAs): multiprotein complexes that link intracellular actin bundles and the extracellular matrix (ECM). FAs are involved in cellular adhesion, growth, differentiation, gene expression, migration, communication, force transmission, and contractility. Focal adhesion signaling molecules, including Focal Adhesion Kinase (FAK), integrins, vinculin, and paxillin, also play pivotal roles in cardiomyogenesis, impacting cell proliferation and heart tube looping. In fact, cardiomyocytes sense ECM stiffness through integrins, modulating signaling pathways like PI3K/AKT and Wnt/β-catenin. Moreover, FAK/Src complex activation mediates cardiac hypertrophic growth and survival signaling in response to mechanical loads. This review provides an overview of the molecular and mechanical mechanisms underlying the crosstalk between FAs and cardiac differentiation, as well as the role of FA-mediated mechanotransduction in guiding cardiac muscle responses to mechanical stimuli.

Artificial Homeostasis Systems Based on Feedback Reaction Networks: Design Principles and Future Promises

Feedback-controlled chemical reaction networks (FCRNs) are indispensable for various biological processes, such as cellular mechanisms, patterns, and signaling pathways. Through the intricate interplay of many feedback loops (FLs), FCRNs maintain a stable internal cellular environment. Currently, creating minimalistic synthetic cells is the long-term objective of systems chemistry, which is motivated by such natural integrity. The design, kinetic optimization, and analysis of FCRNs to exhibit functions akin to those of a cell still pose significant challenges. Indeed, reaching synthetic homeostasis is essential for engineering synthetic cell components. However, maintaining homeostasis in artificial systems against various agitations is a difficult task. Several biological events can provide us with guidelines for a conceptual understanding of homeostasis, which can be further applicable in designing artificial synthetic systems. In this regard, we organize our review with artificial homeostasis systems driven by FCRNs at different length scales, including homogeneous, compartmentalized, and soft material systems. First, we stretch a quick overview of FCRNs in different molecular and supramolecular systems, which are the essential toolbox for engineering different nonlinear functions and homeostatic systems. Moreover, the existing history of synthetic homeostasis in chemical and material systems and their advanced functions with self-correcting, and regulating properties are also emphasized.

Dysregulated cellular metabolism in atherosclerosis: mediators and therapeutic opportunities

Accumulating evidence over the past decades has revealed an intricate relationship between dysregulation of cellular metabolism and the progression of atherosclerotic cardiovascular disease. However, an integrated understanding of dysregulated cellular metabolism in atherosclerotic cardiovascular disease and its potential value as a therapeutic target is missing. In this Review, we (1) summarize recent advances concerning the role of metabolic dysregulation during atherosclerosis progression in lesional cells, including endothelial cells, vascular smooth muscle cells, macrophages and T cells; (2) explore the complexity of metabolic cross-talk between these lesional cells; (3) highlight emerging technologies that promise to illuminate unknown aspects of metabolism in atherosclerosis; and (4) suggest strategies for targeting these underexplored metabolic alterations to mitigate atherosclerosis progression and stabilize rupture-prone atheromas with a potential new generation of cardiovascular therapeutics.

Osteosarcoma Cells Secrete CXCL14 That Activates Integrin α11β1 on Fibroblasts to Form a Lung Metastatic Niche

Cooperation between primary malignant cells and stromal cells can mediate the establishment of lung metastatic niches. Here, we characterized the landscape of cell populations in the tumor microenvironment in treatment-naïve osteosarcoma using single-cell RNA sequencing and identified a stem cell-like cluster with tumor cell-initiating properties and prometastatic traits. CXCL14 was specifically enriched in the stem cell-like cluster and was also significantly upregulated in lung metastases compared with primary tumors. CXCL14 induced stromal reprogramming and evoked a malignant phenotype in fibroblasts to form a supportive lung metastatic niche. Binding of CXCL14 to heterodimeric integrin α11β1 on fibroblasts activated actomyosin contractility and matrix remodeling properties. CXCL14-stimulated fibroblasts produced TGFβ and increased osteosarcoma invasion and migration. mAbs targeting the CXCL14-integrin α11β1 axis inhibited fibroblast TGFβ production, enhanced CD8+ T cell-mediated antitumor immunity, and suppressed osteosarcoma lung metastasis. Taken together, these findings identify cross-talk between osteosarcoma cells and fibroblasts that promotes metastasis and demonstrate that targeting the CXCL14-integrin α11β1 axis is a potential strategy to inhibit osteosarcoma lung metastasis.

SIGNIFICANCE

Cooperation between stem-like osteosarcoma cells and fibroblasts mediated by a CXCL14-integrin α11β1 axis creates a tumor-supportive lung metastatic niche and represents a therapeutic target to suppress osteosarcoma metastasis.

Acoustic Wave-Induced Stroboscopic Optical Mechanotyping of Adherent Cells

In this study, a novel, high content technique using a cylindrical acoustic transducer, stroboscopic fast imaging, and homodyne detection to recover the mechanical properties (dynamic shear modulus) of living adherent cells at low ultrasonic frequencies is presented. By analyzing the micro-oscillations of cells, whole populations are simultaneously mechanotyped with sub-cellular resolution. The technique can be combined with standard fluorescence imaging allowing to further cross-correlate biological and mechanical information. The potential of the technique is demonstrated by mechanotyping co-cultures of different cell types with significantly different mechanical properties.

Acellular Dermal Matrix Cover Improves Skin Growth during Tissue Expansion by Affecting Distribution of Mechanical Forces

BACKGROUND

Biological cover over tissue expander prostheses has been introduced to provide soft-tissue support for tissue expanders during breast reconstruction. However, its impact on mechanically induced skin growth remains unknown. This study investigates the hypothesis that covering the tissue expander with acellular dermal matrix (ADM) affects mechanotransduction without compromising the efficacy of tissue expansion.

METHODS

Tissue expansion, with and without use of ADM, was performed on a porcine model. The tissue expanders were inflated twice with 45 mL of saline, and the full-thickness skin biopsy specimens were harvested from expanded and control unexpanded skin 1 week and 8 weeks after the final inflation. Histologic evaluation, immunohistochemistry staining, and gene expression analysis were performed. Skin growth and total deformation were evaluated using isogeometric analysis.

RESULTS

The authors' results demonstrate that use of ADM as a biological cover during tissue expansion does not impede mechanotransduction that leads to skin growth and blood vessel formation. Isogeometric analysis revealed similar total deformation and growth of expanded skin with and without a biological cover, confirming that its use does not inhibit mechanically induced skin growth. In addition, the authors found that use of an ADM cover results in more uniform distribution of mechanical forces applied by the tissue expander.

CONCLUSIONS

These results suggest that ADM improves mechanically induced skin growth during tissue expansion by facilitating a more uniform distribution of mechanical forces applied by the tissue expander. Therefore, the use of a biological cover has potential to improve outcomes in tissue expansion-based reconstruction.