Integrin α3β1 Binding to Fibronectin Is Dependent on the Ninth Type III Repeat

Novel role of homogalacturonan region of pectin in disrupting the interaction between fibronectin and integrin β1

Pectin interacts with fibronectin (FN), a modular protein in the extracellular matrix. This interaction is significant as FN plays a pivotal role by binding to the receptor integrin α5β1. However, the molecular mechanism underlying the pectin-FN interaction and its impact on integrin binding remains unknown. In this study, water-soluble pectins (WSPs) were extracted from three different pectin sources and subsequently characterized. These included Citrus WSP, which primarily comprises the homogalacturonan region, and Kaki and Yuzu WSPs, both of which are rich in rhamnogalacturonan regions. We investigated the molecular interactions between these WSPs and two FN fragments, Anastellin and RetroNectin, using surface plasmon resonance analysis. Citrus WSP exhibited a notable binding affinity to FN, with a dissociation constant (KD) of approximately 10-7 M. In contrast, Kaki and Yuzu WSPs displayed comparatively weaker or negligible binding affinities. The binding reactivity of Citrus WSP with FN was notably diminished following the enzymatic removal of its methyl-ester groups. Additionally, Citrus WSP disrupted the binding of integrin β1 to RetroNectin without altering the affinity, despite its minimal direct binding to integrin itself. This study furthers our understanding of the intricate pectin-FN interaction and sheds light on their potential physiological relevance and impact on cellular responses.

LAMC2 is a potential prognostic biomarker for cholangiocarcinoma

Cholangiocarcinoma is a common malignancy with increasing incidence worldwide. Most patients are diagnosed at the advanced stage with poor survival rate. Laminin subunit γ2 (LAMC2) is a heparin binding-associated gene involved in tumorigenesis and has been implicated in the prognosis of various types of cancers. However, it is unclear whether expression of LAMC2 is associated with the clinical outcome of patients with cholangiocarcinoma. In the present study, the role and prognostic value of LAMC2 expression in patients with cholangiocarcinoma was investigated. Clinical information and pathological characteristics were analyzed and the association between LAMC2 expression and clinical characteristics, pathological findings and patient outcomes, including metastasis-free and disease-specific survival, were investigated. Data from 182 patients with cholangiocarcinoma were evaluated. High LAMC2 expression was associated with higher tumor stage (P<0.001), large duct type (P=0.024) and poor histological grade (P=0.002). Kaplan-Meier analysis showed high LAMC2 expression was associated with lower overall (P=0.003), disease-specific (P=0.0025), local recurrence-free (P<0.0001) and metastasis-free survival (P<0.0001). Moreover, multivariate analysis demonstrated that increased LAMC2 expression was a significant predictive risk factor for overall [hazard ratio (HR) 1.713; P=0.034], disease-specific (HR 2.011; P=0.039), local recurrence-free (HR 2.721; P<0.001) and metastasis-free survival (HR 3.117; P<0.001). Gene enrichment analysis using Gene Ontology showed that terms associated with LAMC2 upregulation were 'regulation of platelet-derived growth factor receptor-βsignaling pathway' and 'platelet-derived growth factor receptor-β signaling pathway'. The present study indicated that LAMC2 was upregulated in cholangiocarcinoma tumor tissue and had an inverse association with overall, disease-specific, local recurrence-free and metastasis-free survival in patients with cholangiocarcinoma. These results suggested that LAMC2 may serve as a potential biomarker for cholangiocarcinoma.

Receptor-binding domain of SARS-CoV-2 is a functional αv-integrin agonist

Among the novel mutations distinguishing SARS-CoV-2 from similar coronaviruses is a K403R substitution in the receptor-binding domain (RBD) of the viral spike (S) protein within its S1 region. This amino acid substitution occurs near the angiotensin-converting enzyme 2-binding interface and gives rise to a canonical RGD adhesion motif that is often found in native extracellular matrix proteins, including fibronectin. Here, the ability of recombinant S1-RBD to bind to cell surface integrins and trigger downstream signaling pathways was assessed and compared with RGD-containing, integrin-binding fragments of fibronectin. We determined that S1-RBD supported adhesion of fibronectin-null mouse embryonic fibroblasts as well as primary human small airway epithelial cells, while RBD-coated microparticles attached to epithelial monolayers in a cation-dependent manner. Cell adhesion to S1-RBD was RGD dependent and inhibited by blocking antibodies against αv and β3 but not α5 or β1 integrins. Similarly, we observed direct binding of S1-RBD to recombinant human αvβ3 and αvβ6 integrins, but not α5β1 integrins, using surface plasmon resonance. S1-RBD adhesion initiated cell spreading, focal adhesion formation, and actin stress fiber organization to a similar extent as fibronectin. Moreover, S1-RBD stimulated tyrosine phosphorylation of the adhesion mediators FAK, Src, and paxillin; triggered Akt activation; and supported cell proliferation. Thus, the RGD sequence of S1-RBD can function as an αv-selective integrin agonist. This study provides evidence that cell surface αv-containing integrins can respond functionally to spike protein and raises the possibility that S1-mediated dysregulation of extracellular matrix dynamics may contribute to the pathogenesis and/or post-acute sequelae of SARS-CoV-2 infection.

Extracellular matrix regulates force transduction at VE-cadherin junctions

Increased tension on VE-cadherin (VE-cad) complexes activates adaptive cell stiffening and local cytoskeletal reinforcement--two key signatures of intercellular mechanotransduction. Here we demonstrate that tugging on VE-cad receptors initiates a cascade that results in downstream integrin activation. The formation of new integrin adhesions potentiates vinculin and actin recruitment to mechanically reinforce stressed cadherin adhesions. This cascade differs from documented antagonistic effects of integrins on intercellular junctions. We identify focal adhesion kinase, Abl kinase, and RhoA GTPase as key components of the positive feedback loop. Results further show that a consequence of integrin involvement is the sensitization of intercellular force transduction to the extracellular matrix (ECM) not by regulating junctional tension but by altering signal cascades that reinforce cell-cell adhesions. On type 1 collagen or fibronectin substrates, integrin subtypes α2β1 and α5β1, respectively, differentially control actin remodeling at VE-cad adhesions. Specifically, ECM-dependent differences in VE-cad force transduction mirror differences in the rigidity sensing mechanisms of α2β1 and α5β1 integrins. The findings verify the role of integrins in VE-cad force transduction and uncover a previously unappreciated mechanism by which the ECM impacts the mechanical reinforcement of interendothelial junctions.

Recurrence of Papillary Thyroid Cancer: A Systematic Appraisal of Risk Factors

CONTEXT

Thyroid cancer recurrence is associated with increased mortality and adverse outcomes. Recurrence risk is currently predicted using clinical tools, often restaging patients after treatment. Detailed understanding of recurrence risk at disease onset could lead to personalized and improved patient care.

OBJECTIVE

We aimed to perform a comprehensive bioinformatic and experimental analysis of 3 levels of genetic change (mRNA, microRNA, and somatic mutation) apparent in recurrent tumors and construct a new combinatorial prognostic risk model.

METHODS

We analyzed The Cancer Genome Atlas data (TCGA) to identify differentially expressed genes (mRNA/microRNA) in 46 recurrent vs 455 nonrecurrent thyroid tumors. Two exonic mutational pipelines were used to identify somatic mutations. Functional gene analysis was performed in cell-based assays in multiple thyroid cell lines. The prognostic value of genes was evaluated with TCGA datasets.

RESULTS

We identified 128 new potential biomarkers associated with recurrence, including 40 mRNAs, 39 miRNAs, and 59 genetic variants. Among differentially expressed genes, modulation of FN1, ITGα3, and MET had a significant impact on thyroid cancer cell migration. Similarly, ablation of miR-486 and miR-1179 significantly increased migration of TPC-1 and SW1736 cells. We further utilized genes with a validated functional role and identified a 5-gene risk score classifier as an independent predictor of thyroid cancer recurrence.

CONCLUSION

Our newly proposed risk model based on combinatorial mRNA and microRNA expression has potential clinical utility as a prognostic indicator of recurrence. These findings should facilitate earlier prediction of recurrence with implications for improving patient outcome by tailoring treatment to disease risk and increasing posttreatment surveillance.

Receptor binding domain of SARS-CoV-2 is a functional αv-integrin agonist

Among the novel mutations distinguishing SARS-CoV-2 from similar respiratory coronaviruses is a K403R substitution in the receptor-binding domain (RBD) of the viral spike (S) protein within its S1 region. This amino acid substitution occurs near the angiotensin-converting enzyme 2 (ACE2)-binding interface and gives rise to a canonical RGD adhesion motif that is often found in native extracellular matrix proteins, including fibronectin. In the present study, the ability of recombinant S1-RBD to bind to cell surface integrins and trigger downstream signaling pathways was assessed and compared to RGD-containing, integrin-binding fragments of fibronectin. S1-RBD supported adhesion of both fibronectin-null mouse embryonic fibroblasts as well as primary human small airway epithelial cells. Cell adhesion to S1-RBD was cation- and RGD-dependent, and was inhibited by blocking antibodies against α v and β 3 , but not α 5 or β 1 , integrins. Similarly, direct binding of S1-RBD to recombinant human α v β 3 and α v β 6 integrins, but not α 5 β 1 integrins, was observed by surface plasmon resonance. Adhesion to S1-RBD initiated cell spreading, focal adhesion formation, and actin stress fiber organization to a similar extent as fibronectin. Moreover, S1-RBD stimulated tyrosine phosphorylation of the adhesion mediators FAK, Src, and paxillin, Akt activation, and supported cell proliferation. Together, these data demonstrate that the RGD sequence within S1-RBD can function as an α v -selective integrin agonist. This study provides evidence that cell surface α v -containing integrins can respond functionally to spike protein and raise the possibility that S1-mediated dysregulation of ECM dynamics may contribute to the pathogenesis and/or post-acute sequelae of SARS-CoV-2 infection.

Key concepts in muscle regeneration: muscle "cellular ecology" integrates a gestalt of cellular cross-talk, motility, and activity to remodel structure and restore function

This review identifies some key concepts of muscle regeneration, viewed from perspectives of classical and modern research. Early insights noted the pattern and sequence of regeneration across species was similar, regardless of the type of injury, and differed from epimorphic limb regeneration. While potential benefits of exercise for tissue repair was debated, regeneration was not presumed to deliver functional restoration, especially after ischemia-reperfusion injury; muscle could develop fibrosis and ectopic bone and fat. Standard protocols and tools were identified as necessary for tracking injury and outcomes. Current concepts vastly extend early insights. Myogenic regeneration occurs within the environment of muscle tissue. Intercellular cross-talk generates an interactive system of cellular networks that with the extracellular matrix and local, regional, and systemic influences, forms the larger gestalt of the satellite cell niche. Regenerative potential and adaptive plasticity are overlain by epigenetically regionalized responsiveness and contributions by myogenic, endothelial, and fibroadipogenic progenitors and inflammatory and metabolic processes. Muscle architecture is a living portrait of functional regulatory hierarchies, while cellular dynamics, physical activity, and muscle-tendon-bone biomechanics arbitrate regeneration. The scope of ongoing research-from molecules and exosomes to morphology and physiology-reveals compelling new concepts in muscle regeneration that will guide future discoveries for use in application to fitness, rehabilitation, and disease prevention and treatment.

Bio-functionalization and in-vitro evaluation of titanium surface with recombinant fibronectin and elastin fragment in human mesenchymal stem cell

Titanium is a biomaterial that meets a number of important requirements, including excellent mechanical and chemical properties, but has low bioactivity. To improve cellular response onto titanium surfaces and hence its osseointegration, the titanium surface was bio-functionalized to mimic an extracellular matrix (ECM)-like microenvironment that positively influences the behavior of stem cells. In this respect, fibronectin and elastin are important components of the ECM that regulate stem cell differentiation by supporting the biological microenvironment. However, each native ECM is unsuitable due to its high production cost and immunogenicity. To overcome these problems, a recombinant chimeric fibronectin type III_9-10 and elastin-like peptide fragments (FN9-10_ELP) was developed herein and applied to the bio-functionalized of the titanium surface. An evaluation of the biological activity and cellular responses with respect to bone regeneration indicated a 4-week sustainability on the FN9-10_ELP functionalized titanium surface without an initial burst effect. In particular, the adhesion and proliferation of human mesenchymal stem cells (hMSCs) was significantly increased on the FN9-10_ELP coated titanium compared to that observed on the non-coated titanium. The FN9-10_ELP coated titanium induced osteogenic differentiation such as the alkaline phosphatase (ALP) activity and mineralization activity. In addition, expressions of osteogenesis-related genes such as a collagen type I (Col I), Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), osteocalcin (OCN), bone sialo protein (BSP), and PDZ-binding motif (TAZ) were further increased. Thus, in vitro the FN9-10_ELP functionalization titanium not only sustained bioactivity but also induced osteogenic differentiation of hMSCs to improve bone regeneration.

Tissue factor potentiates adherence of breast cancer cells to human umbilical vein endothelial cells under static and flow conditions

Tissue factor (TF) has been extensively studied for tumor metastasis, but its role in mediating cancer cell adhesion to vasculature remains unknown. This study aimed to measure the ability of TF to mediate the adhesion of breast cancer cells to human umbilical vein endothelial cells (HUVECs). MDA-MB-231 cells expressed the highest TF level and adhered more to HUVECs under static and flow conditions, a neutralizing TF antibody abolished the enhanced adhesion of MDA-MB-231 cells to HUVECs. Recombinant human soluble TF (rTF) bonded β1integrin on HUVECs surfaces, β1 or α3integrin antibody combined with TF antibody abolished more cell-cell adhesion. These data suggested that TF mediated adhesion of breast cancer cells to endothelial cells may rely on β1integrin on HUVECs surfaces.

Design and Evaluation of a Polypeptide that Mimics the Integrin Binding Site for EDA Fibronectin to Block Profibrotic Cell Activity

Fibrosis is characterized by excessive production of disorganized collagen- and fibronectin-rich extracellular matrices (ECMs) and is driven by the persistence of myofibroblasts within tissues. A key protein contributing to myofibroblast differentiation is extra domain A fibronectin (EDA-FN). We sought to target and interfere with interactions between EDA-FN and its integrin receptors to effectively inhibit profibrotic activity and myofibroblast formation. Molecular docking was used to assist in the design of a blocking polypeptide (antifibrotic 38-amino-acid polypeptide, AF38Pep) for specific inhibition of EDA-FN associations with the fibroblast-expressed integrins α₄β₁ and α₄β₇. Blocking peptides were designed and evaluated in silico before synthesis, confirmation of binding specificity, and evaluation in vitro. We identified the high-affinity EDA-FN C-C′ loop binding cleft within integrins α₄β₁ and α₄β₇. The polypeptide with the highest predicted binding affinity, AF38Pep, was synthesized and could achieve specific binding to myofibroblast fibronectin-rich ECM and EDA-FN C-C′ loop peptides. AF38Pep demonstrated potent myofibroblast inhibitory activity at 10 µg/mL and was not cytotoxic. Treatment with AF38Pep prevented integrin α₄β₁-mediated focal adhesion kinase (FAK) activation and early signaling through extracellular-signal-regulated kinases 1 and 2 (ERK1/2), attenuated the expression of pro-matrix metalloproteinase 9 (MMP9) and pro-MMP2, and inhibited collagen synthesis and deposition. Immunocytochemistry staining revealed an inhibition of α-smooth muscle actin (α-SMA) incorporation into actin stress fibers and attenuated cell contraction. Increases in the expression of mRNA associated with fibrosis and downstream from integrin signaling were inhibited by treatment with AF38Pep. Our study suggested that AF38Pep could successfully interfere with EDA-FN C-C′ loop-specific integrin interactions and could act as an effective inhibitor of fibroblast of myofibroblast differentiation.

Fibronectin 1 activates WNT/β-catenin signaling to induce osteogenic differentiation via integrin β1 interaction

Osteoporosis (OP) is a systemic skeletal disease leading to fragility fractures and is a major health issue globally. WNT/β-catenin signaling regulates bone-remodeling processes and plays vital roles in OP development. However, the underlying regulatory mechanisms behind WNT/β-catenin signaling in OP requires clarification, as further studies are required to identify novel alternate therapeutic agents to improve OP. Here we report that fibronectin 1 (FN-1) promoted differentiation and mineralization of osteoblasts by activating WNT/β-catenin pathway, in cultured pre-osteoblasts. With isobaric tags for relative and absolute quantitation labeling proteomics analysis, we investigated protein changes in bone samples from OP patients and normal controls. FN-1 accumulated in osteoblasts in bone samples from OP patients and age-related OP mice compared to control group. In addition, we observed that integrin β1 (ITGB1) acts as an indispensable signaling molecule for the interplay between FN-1 and β-catenin, and that FN-1 expression increased, but ITGB1 expression decreased in osteoblasts during OP progression. Therefore, our study reveals a novel explanation for WNT/β-catenin pathway inactivation in OP pathology. Supplying of FN-1 and ITGB1 may provide a potential therapeutic strategy in improving bone formation during OP.

Review of Integrin-Targeting Biomaterials in Tissue Engineering

The ability to direct cell behavior has been central to the success of numerous therapeutics to regenerate tissue or facilitate device integration. Biomaterial scientists are challenged to understand and modulate the interactions of biomaterials with biological systems in order to achieve effective tissue repair. One key area of research investigates the use of extracellular matrix-derived ligands to target specific integrin interactions and induce cellular responses, such as increased cell migration, proliferation, and differentiation of mesenchymal stem cells. These integrin-targeting proteins and peptides have been implemented in a variety of different polymeric scaffolds and devices to enhance tissue regeneration and integration. This review first presents an overview of integrin-mediated cellular processes that have been identified in angiogenesis, wound healing, and bone regeneration. Then, research utilizing biomaterials are highlighted with integrin-targeting motifs as a means to direct these cellular processes to enhance tissue regeneration. In addition to providing improved materials for tissue repair and device integration, these innovative biomaterials provide new tools to probe the complex processes of tissue remodeling in order to enhance the rational design of biomaterial scaffolds and guide tissue regeneration strategies.

Interactions at engineered graft-tissue interfaces: A review

The interactions at the graft-tissue interfaces are critical for the results of engraftments post-implantation. To improve the success rate of the implantations, as well as the quality of the patients' life, understanding the possible reactions between artificial materials and the host tissues is helpful in designing new generations of material-based grafts aiming at inducing specific responses from surrounding tissues for their own reparation and regeneration. To help researchers understand the complicated interactions that occur after implantations and to promote the development of better-designed grafts with improved biocompatibility and patient responses, in this review, the topics will be discussed from the basic reactions that occur chronologically at the graft-tissue interfaces after implantations to the existing and potential applications of the mechanisms of such reactions in designing of grafts. It offers a chance to bring up-to-date advances in the field and new strategies of controlling the graft-tissue interfaces.

Engineering PEG-based hydrogels to foster efficient endothelial network formation in free-swelling and confined microenvironments

In vitro tissue engineered models are poised to have significant impact on disease modeling and preclinical drug development. Reliable methods to induce microvascular networks in such microphysiological systems are needed to improve the size and physiological function of these models. By systematically engineering several physical and biomolecular properties of the cellular microenvironment (including crosslinking density, polymer density, adhesion ligand concentration, and degradability), we establish design principles that describe how synthetic matrix properties influence vascular morphogenesis in modular and tunable hydrogels based on commercial 8-arm poly (ethylene glycol) (PEG8a) macromers. We apply these design principles to generate endothelial networks that exhibit consistent morphology throughout depths of hydrogel greater than 1 mm. These PEG8a-based hydrogels have relatively high volumetric swelling ratios (>1.5), which limits their utility in confined environments such as microfluidic devices. To overcome this limitation, we mitigate swelling by incorporating a highly functional PEG-grafted alpha-helical poly (propargyl-l-glutamate) (PPLGgPEG) macromer along with the canonical 8-arm PEG8a macromer in gel formation. This hydrogel platform supports enhanced endothelial morphogenesis in neutral-swelling environments. Finally, we incorporate PEG8a-PPLGgPEG gels into microfluidic devices and demonstrate improved diffusion kinetics and microvascular network formation in situ compared to PEG8a-based gels.

A Matricryptic Conformation of the Integrin-Binding Domain of Fibronectin Regulates Platelet-Derived Growth Factor-Induced Intracellular Calcium Release

Platelet-derived growth factor (PDGF) signaling is dysregulated in a wide variety of diseases, making PDGF an attractive therapeutic target. However, PDGF also affects numerous signaling cascades essential for tissue homeostasis, limiting the development of PDGF-based therapies that lack adverse side-effects. Recent studies showed that fibroblast-mediated assembly of extracellular matrix (ECM) fibronectin fibrils attenuates PDGF-induced intracellular calcium release by selectively inhibiting phosphoinositol 3-kinase (PI3K) activation while leaving other PDGF-mediated signaling cascades intact. In the present study, a series of recombinant fibronectin-derived fusion proteins were used to localize the sequences in fibronectin that are responsible for this inhibition. Results demonstrate that attenuation of PDGF-induced intracellular calcium release by the fibronectin matrix mimetic, FNIII1H,8-10 requires α5β1 integrin ligation, but is not dependent upon the matricryptic, heparin-binding site of FNIII1. Intact cell-binding fibronectin fragments were also unable to attenuate PDGF-induced intracellular calcium release. In contrast, a novel integrin-binding fragment that adopts an extended and aligned conformational state, inhibited both PI3K activation and intracellular calcium release in response to PDGF. Taken together, these studies provide evidence that attenuation of PDGF-induced intracellular calcium release by fibronectin is mediated by a novel conformation of the α5β1 integrin-binding, FNIII9-10 modules, that is expressed by fibrillar fibronectin.

Targeting the Immune Microenvironment in the Treatment of Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is a highly aggressive solid tumor, with a 5-year mortality rate of ~50%. The development of immunotherapies has improved the survival of patients with HNSCC, but, the long-term prognosis of patients with recurrent or metastatic HNSCC remains poor. HNSCC is characterized by intratumoral infiltration of regulatory T cells, dysfunctional natural killer cells, an elevated Treg/CD8+ T cell ratio, and increased programmed cell death ligand 1 protein on tumor cells. This leads to an immunocompromised niche in favor of the proliferation and treatment resistance of cancer cells. To achieve an improved treatment response, several potential combination strategies, such as increasing the neoantigens for antigen presentation and therapeutic agents targeting components of the tumor microenvironment, have been explored and have shown promising results in preclinical studies. In addition, large-scale bioinformatic studies have also identified possible predictive biomarkers of HNSCC. As immunotherapy has shown survival benefits in recent HNSCC clinical trials, a comprehensive investigation of immune cells and immune-related factors/cytokines and the immune profiling of tumor cells during the development of HNSCC may provide more insights into the complex immune microenvironment and thus, facilitate the development of novel immunotherapeutic agents.

Effect of tumor microenvironment on pathogenesis of the head and neck squamous cell carcinoma: a systematic review

The tumor microenvironment (TME) is comprised of many different cell populations, such as cancer-associated fibroblasts and various infiltrating immune cells, and non-cell components of extracellular matrix. These crucial parts of the surrounding stroma can function as both positive and negative regulators of all hallmarks of cancer development, including evasion of apoptosis, induction of angiogenesis, deregulation of the energy metabolism, resistance to the immune detection and destruction, and activation of invasion and metastasis. This review represents a summary of recent studies focusing on describing these effects of microenvironment on initiation and progression of the head and neck squamous cell carcinoma, focusing on oral squamous cell carcinoma, since it is becoming clear that an investigation of differences in stromal composition of the head and neck squamous cell carcinoma microenvironment and their impact on cancer development and progression may help better understand the mechanisms behind different responses to therapy and help define possible targets for clinical intervention.

Cardiac Extracellular Matrix Modification as a Therapeutic Approach

The cardiac extracellular matrix (cECM) is comprised of proteins and polysaccharides secreted by cardiac cell types, which provide structural and biochemical support to cardiovascular tissue. The roles of cECM proteins and the associated family of cell surface receptor, integrins, have been explored in vivo via the generation of knockout experimental animal models. However, the complexity of tissues makes it difficult to isolate the effects of individual cECM proteins on a particular cell process or disease state. The desire to further dissect the role of cECM has led to the development of a variety of in vitro model systems, which are now being used not only for basic studies but also for testing drug efficacy and toxicity and for generating therapeutic scaffolds. These systems began with 2D coatings of cECM derived from tissue and have developed to include recombinant ECM proteins, ECM fragments, and ECM mimics. Most recently 3D model systems have emerged, made possible by several developing technologies including, and most notably, 3D bioprinting. This chapter will attempt to track the evolution of our understanding of the relationship between cECM and cell behavior from in vivo model to in vitro control systems. We end the chapter with a summary of how basic studies such as these have informed the use of cECM as a direct therapy.

Local remodeling of synthetic extracellular matrix microenvironments by co-cultured endometrial epithelial and stromal cells enables long-term dynamic physiological function

Mucosal barrier tissues, comprising a layer of tightly-bonded epithelial cells in intimate molecular communication with an underlying matrix-rich stroma containing fibroblasts and immune cells, are prominent targets for drugs against infection, chronic inflammation, and other disease processes. Although human in vitro models of such barriers are needed for mechanistic studies and drug development, differences in extracellular matrix (ECM) needs of epithelial and stromal cells hinder efforts to create such models. Here, using the endometrium as an example mucosal barrier, we describe a synthetic, modular ECM hydrogel suitable for 3D functional co-culture, featuring components that can be remodeled by cells and that respond dynamically to sequester local cell-secreted ECM characteristic of each cell type. The synthetic hydrogel combines peptides with off-the-shelf reagents and is thus accessible to cell biology labs. Specifically, we first identified a single peptide as suitable for initial attachment of both endometrial epithelial and stromal cells using a 2D semi-empirical screen. Then, using a co-culture system of epithelial cells cultured on top of gel-encapsulated stromal cells, we show that inclusion of ECM-binding peptides in the hydrogel, along with the integrin-binding peptide, leads to enhanced accumulation of basement membrane beneath the epithelial layer and more fibrillar collagen matrix assembly by stromal cells over two weeks in culture. Importantly, endometrial co-cultures composed of either cell lines or primary cells displayed hormone-mediated differentiation as assessed by morphological changes and secretory protein production. A multiplex analysis of apical cytokine and growth factor secretion comparing cell lines and primary cells revealed strikingly different patterns, underscoring the importance of using primary cell models in analysis of cell-cell communication networks. In summary, we define a "one-size-fits-all" synthetic ECM that enables long-term, physiologically responsive co-cultures of epithelial and stromal cells in a mucosal barrier format.

Hydrogels with precisely controlled integrin activation dictate vascular patterning and permeability

Integrin binding to bioengineered hydrogel scaffolds is essential for tissue regrowth and regeneration, yet not all integrin binding can lead to tissue repair. Here, we show that through engineering hydrogel materials to promote α3/α5β1 integrin binding, we can promote the formation of a space-filling and mature vasculature compared with hydrogel materials that promote αvβ3 integrin binding. In vitro, α3/α5β1 scaffolds promoted endothelial cells to sprout and branch, forming organized extensive networks that eventually reached and anastomosed with neighbouring branches. In vivo, α3/α5β1 scaffolds delivering vascular endothelial growth factor (VEGF) promoted non-tortuous blood vessel formation and non-leaky blood vessels by 10 days post-stroke. In contrast, materials that promote αvβ3 integrin binding promoted endothelial sprout clumping in vitro and leaky vessels in vivo. This work shows that precisely controlled integrin activation from a biomaterial can be harnessed to direct therapeutic vessel regeneration and reduce VEGF-induced vascular permeability in vivo.

Detection of an Integrin-Binding Mechanoswitch within Fibronectin during Tissue Formation and Fibrosis

Fibronectin (Fn) is an extracellular matrix protein that orchestrates complex cell adhesion and signaling through cell surface integrin receptors during tissue development, remodeling, and disease, such as fibrosis. Fn is sensitive to mechanical forces in its tandem type III repeats, resulting in extensive molecular enlongation. As such, it has long been hypothesized that cell- and tissue-derived forces may activate an "integrin switch" within the critical integrin-binding ninth and 10th type III repeats-conferring differential integrin-binding specificity, leading to differential cell responses. Yet, no direct evidence exists to prove the hypothesis nor demonstrate the physiological existence of the switch. We report direct experimental evidence for the Fn integrin switch both in vitro and ex vivo using a scFv engineered to detect the transient, force-induced conformational change, representing an opportunity for detection and targeting of early molecular signatures of cell contractile forces in tissue repair and disease.

Molecular Mechanisms of Human Papillomavirus Induced Skin Carcinogenesis

Infection of the cutaneous skin with human papillomaviruses (HPV) of genus betapapillomavirus (βHPV) is associated with the development of premalignant actinic keratoses and squamous cell carcinoma. Due to the higher viral loads of βHPVs in actinic keratoses than in cancerous lesions, it is currently discussed that these viruses play a carcinogenic role in cancer initiation. In vitro assays performed to characterize the cell transforming activities of high-risk HPV types of genus alphapapillomavirus have markedly contributed to the present knowledge on their oncogenic functions. However, these assays failed to detect oncogenic functions of βHPV early proteins. They were not suitable for investigations aiming to study the interactive role of βHPV positive epidermis with mesenchymal cells and the extracellular matrix. This review focuses on βHPV gene functions with special focus on oncogenic mechanisms that may be relevant for skin cancer development.

Material Strategies for Modulating Epithelial to Mesenchymal Transitions

Epithelial to mesenchymal transitions (EMT) involve the phenotypic change of epithelial cells into fibroblast-like cells. This process is accompanied by the loss of cell-cell contacts, increased extracellular matrix (ECM) production, stress fiber alignment, and an increase in cell mobility. While essential for development and wound repair, EMT has also been recognized as a contributing factor to fibrotic diseases and cancer. Both chemical and mechanical cues, such as tumor necrosis factor alpha, NF-κB, Wnt, Notch, interleukin-8, metalloproteinase-3, ECM proteins, and ECM stiffness can determine the degree and duration of EMT events. Additionally, transforming growth factor beta is a primary driver of EMT and, interestingly, can be activated through cell-mediated mechanoactivation. In this review, we highlight recent findings demonstrating the contribution of mechanical stimuli, such as tissue and material stiffness, in driving EMT. We then highlight material strategies for controlling EMT events. Finally, we discuss drivers of the similar process of endothelial to mesenchymal transition (EndoMT) and corresponding material strategies for controlling EndoMT.

On-demand dissolution of modular, synthetic extracellular matrix reveals local epithelial-stromal communication networks

Methods to parse paracrine epithelial-stromal communication networks are a vital need in drug development, as disruption of these networks underlies diseases ranging from cancer to endometriosis. Here, we describe a modular, synthetic, and dissolvable extracellular matrix (MSD-ECM) hydrogel that fosters functional 3D epithelial-stromal co-culture, and that can be dissolved on-demand to recover cells and paracrine signaling proteins intact for subsequent analysis. Specifically, synthetic polymer hydrogels, modified with cell-interacting adhesion motifs and crosslinked with peptides that include a substrate for cell-mediated proteolytic remodeling, can be rapidly dissolved by an engineered version of the microbial transpeptidase Sortase A (SrtA) if the crosslinking peptide includes a SrtA substrate motif and a soluble second substrate. SrtA-mediated dissolution affected only 1 of 31 cytokines and growth factors assayed, whereas standard protease degradation methods destroyed about half of these same molecules. Using co-encapsulated endometrial epithelial and stromal cells as one model system, we show that the dynamic cytokine and growth factor response of co-cultures to an inflammatory cue is richer and more nuanced when measured from SrtA-dissolved gel microenvironments than from the culture supernate. This system employs accessible, reproducible reagents and facile protocols; hence, has potential as a tool in identifying and validating therapeutic targets in complex diseases.

The role of biophysical properties of provisional matrix proteins in wound repair

Wound healing is a complex, dynamic process required for maintaining homeostasis in an organism. Along with being controlled biochemically, wound healing is also controlled through the transduction of biophysical stimuli through cell interactions with the extracellular matrix (ECM). This review provides an overview of the ECM's role in the wound healing process and subsequently expands on the variety of roles biophysical phenomenon play.