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This study presents a novel surgical model developed to provide hematological support for implanted cellularized devices augmenting or replacing liver tissue function. Advances in bioengineering provide tools and materials to create living tissue replacements designed to restore that lost to disease, trauma, or congenital deformity. Such substitutes are often assembled and matured in vitro and need an immediate blood supply upon implantation, necessitating the development of supporting protocols. Animal translational models are required for continued development of engineered structures prior to clinical implementation, with rodent models often playing an essential early role. Our long-term goal has been generation of living tissue to provide liver function, utilizing advances in additive manufacturing technology to create 3D structures with intrinsic micron to millimeter scale channels modeled on natural vasculature. The surgical protocol developed enables testing various design iterations in vivo by anastomosis to the host rat vasculature. Lobation of rodent liver facilitates partial hepatectomy and re-purposing the remaining vasculature to support implanted engineered tissue. Removal of the left lateral lobe exposes the underlying hepatic vasculature and can create space for a device. A shunt is created from the left portal vein to the left hepatic vein by cannulating each with separate silicone tubing. The device is then integrated into the shunt by connecting its inflow and outflow ports to the tubing and re-establishing blood flow. Sustained anti-coagulation is maintained with an implanted osmotic pump. In our studies, animals were freely mobile after implantation; devices remained patent while maintaining blood flow through their millifluidic channels. This vascular anastomosis model has been greatly refined during the process of performing over 200 implantation procedures. We anticipate that the model described herein will find utility in developing preclinical translational protocols for evaluation of engineered liver tissue.

A graphene field-effect transistor (gFET) was non-covalently functionalised with 1-pyrenebutyric acid N-hydroxysuccinimide ester and conjugated with anti-CD63 antibodies for the label-free detection of exosomes. Using a microfluidic channel, part of a graphene film was exposed to solution. The change in electrical properties of the exposed graphene created an additional minimum alongside the original Dirac point in the drain-source current (Ids) - back-gate voltage (Vg) curve. When phosphate buffered saline (PBS) was present in the channel, the additional minimum was present at a Vg lower than the original Dirac point and shifted with time when exosomes were introduced into the channel. This shift of the minimum from the PBS reference point reached saturation after 30 minutes and was observed for multiple exosome concentrations. Upon conjugation with an isotype control, sensor response to the highest concentration of exosomes was negligible in comparison to that with anti-CD63 antibody, indicating that the functionalised gFET can specifically detect exosomes at least down to 0.1 μg/mL and is sensitive to concentration. Such a gFET biosensor has not been used before for exosome sensing and could be an effective tool for the liquid-biopsy detection of exosomes as biomarkers for early-stage identification of diseases such as cancer.

Recent research has highlighted the importance of key tumor microenvironment features, notably the collagen-rich extracellular matrix (ECM) in characterizing tumor invasion and progression. This led to great interest from both basic researchers and clinicians, including pathologists, to include collagen fiber evaluation as part of the investigation of cancer development and progression. Fibrillar collagen is the most abundant in the normal extracellular matrix, and was revealed to be upregulated in many cancers. Recent studies suggested an emerging theme across multiple cancer types in which specific collagen fiber organization patterns differ between benign and malignant tissue and also appear to be associated with disease stage, prognosis, treatment response, and other clinical features. There is great potential for developing image-based collagen fiber biomarkers for clinical applications, but its adoption in standard clinical practice is dependent on further translational and clinical evaluations. Here, we offer a comprehensive review of the current literature of fibrillar collagen structure and organization as a candidate cancer biomarker, and new perspectives on the challenges and next steps for researchers and clinicians seeking to exploit this information in biomedical research and clinical workflows.

Focal adhesion kinase (FAK) is an important mediator of extracellular matrix–integrin mechano-signal transduction that regulates cell motility, survival, and proliferation. As such, FAK is being investigated as a potential therapeutic target for malignant and fibrotic diseases, and numerous clinical trials of FAK inhibitors are underway. The function of FAK in nonmalignant, nonmotile epithelial cells is not well understood. We previously showed that hepatocytes demonstrated activated FAK near stiff collagen tracts in fibrotic livers. In this study, we examined the role of liver epithelial FAK by inducing fibrotic liver disease in mice with liver epithelial FAK deficiency. We found that mice that lacked FAK in liver epithelial cells developed more severe liver injury and worse fibrosis as compared with controls. Increased fibrosis in liver epithelial FAK-deficient mice was linked to the activation of several profibrotic pathways, including the hedgehog/smoothened pathway. FAK-deficient hepatocytes produced increased Indian hedgehog in a manner dependent on matrix stiffness. Furthermore, expression of the hedgehog receptor, smoothened, was increased in macrophages and biliary cells of hepatocyte-specific FAK-deficient fibrotic livers. These results indicate that liver epithelial FAK has important regulatory roles in the response to liver injury and progression of fibrosis., Liver epithelial-specific FAK-deficient mice develop worse liver injury and fibrosis compared to controls, indicating that FAK has a regulatory role.

The tumor microenvironment is fundamental to cancer progression, and the influence of its mechanical properties is increasingly being appreciated. Tamoxifen has been used for many years to treat estrogen‐positive breast cancer. Here we report that tamoxifen regulates the level and activity of collagen cross‐linking and degradative enzymes, and hence the organization of the extracellular matrix, via a mechanism involving both the G protein‐coupled estrogen receptor (GPER) and hypoxia‐inducible factor‐1 alpha (HIF‐1A). We show that tamoxifen reduces HIF‐1A levels by suppressing myosin‐dependent contractility and matrix stiffness mechanosensing. Tamoxifen also downregulates hypoxia‐regulated genes and increases vascularization in PDAC tissues. Our findings implicate the GPER/HIF‐1A axis as a master regulator of peri‐tumoral stromal remodeling and the fibrovascular tumor microenvironment and offer a paradigm shift for tamoxifen from a well‐established drug in breast cancer hormonal therapy to an alternative candidate for stromal targeting strategies in PDAC and possibly other cancers.See also: E Cortes et al (January 2019) andM Pein & T Oskarsson (January 2019)EMBO Reports (2019) 20: e46557

Polymorphonuclear leukocytes (PMNs) release granule proteins as the first line of defense against bacteria and set up chemotactic gradients that result in monocyte infiltration to the site of injury. Although well established, the role of biomaterials in regulating adherent PMN degranulation and subsequent PMN-monocyte paracrine interactions is less clear. The aim of this study was to determine how biomaterials affect the degranulation of selected biomarkers and downstream monocyte adhesion and transendothelial migration. Poly(ethylene glycol) (PEG)-containing hydrogels (PEG and an interpenetrating network of PEG and gelatin) promote the release of the α-defensins human neutrophil peptides 1-3, but not azurocidin or monocyte chemotactic protein-1. Although human neutrophil peptides 1-3 are monocyte chemoattractants, no subsequent effects on monocyte transmigration are observed in static conditions. Under flow conditions, monocyte adhesion on human umbilical vein endothelial cells stimulated with tumor necrosis factor-α is elevated in the presence of granule proteins from PMNs adherent on polydimethylsiloxane, but not from PMNs cultured on PEG hydrogels. These results suggest that PEG promotes PMN antimicrobial capacity without enhanced monocyte recruitment.

The hallmark of pancreatic ductal adenocarcinoma (PDAC) is abundant desmoplasia, which is orchestrated by pancreatic stellate cells (PSCs) and accounts for the majority of the stroma surrounding the tumour. Healthy PSCs are quiescent, but upon activation during disease progression, they adopt a myofibroblast-contractile phenotype and secrete and concomitantly reorganise the stiff extracellular matrix (ECM). Transforming growth factor β (TGF-β) is a potent activator of PSCs, and its activation requires spatiotemporal organisation of cellular and extracellular cues to liberate it from an inactive complex with latent TGF-β binding protein (LTBP). Here we study the mechanical activation of TGF-β by PSCs in vitro by investigating LTBP-1 organisation with fibrillar fibronectin and show that all trans-retinoic acid (ATRA), which induces PSC quiescence, down-regulates the ability of PSCs to mechanically organise LTBP-1 and activate TGF-β through a mechanism involving myosin II dependent contractility. Therefore, ATRA inhibits the ability of PSCs to mechanically release active TGF-β, which might otherwise act in an autocrine manner to sustain PSCs in an active state and a tumour-favouring stiff microenvironment.

Talin is a ubiquitous, large focal adhesion protein that links intracellular networks with the extracellular matrix (ECM) via its connection with the actin cytoskeleton and membrane integrins. It is one of a handful molecules that can expose new recognition sites when undergoing force-induced mechanical unfolding, and it can bind and recruit cytoskeletal proteins that are involved in mechanotransduction. Talin has attracted great interest in the field of mechanobiology because of its plasticity in undergoing conformational changes under force stimulation as well as its cellular localization that bridges the cytoskeleton with the ECM. In addition to these roles in healthy cells, the dysregulation of talin activators can lead to disease states in which aberrant integrin activation and mechanotransduction precipitate changes in cell spreading, migration, and survival. New data have implicated a role for talin in diseases that are highly regulated by mechanical cues. In this review, we present the current understanding of talin structure, its relationship to binding partners, and its role in disease states.-Haining, A. W. M., Lieberthal, T. J., del Rio Hernandez, A. Talin: a mechanosensitive molecule in health and disease.

In the foreign body response, infiltrating PMNs exocytose granule subsets to influence subsequent downstream inflammatory and wound healing events. In previous studies, we found that PMNs cultured on poly(ethylene glycol) (PEG)-containing hydrogels (i.e., PEG and gelatin + PEG hydrogels) had enhanced primary granule release, yet similar tertiary granule release compared with PMNs cultured on polydimethylsiloxane or tissue culture polystyrene. PMN primary granules contain microbicidal proteins and proteases, which can potentially injure bystander cells, degrade the extracellular matrix, and promote inflammation. Here, we sought to understand the mechanism of the enhanced primary granule release from PMNs on PEG hydrogels. We found that primary granule release from PMNs on PEG hydrogels was adhesion mediated and involved Src family kinases and PI3K-γ. The addition of gelatin to PEG hydrogels did not further enhance PMN primary granule release. Using stable-isotope dimethyl labeling-based shotgun proteomics, we identified many serum proteins – including Ig gamma constant chain region proteins and alpha-1-acid glycoprotein 1 – that were absorbed/adsorbed in higher quantities on PEG hydrogels than on TCPS, and may be involved in mediating PMN primary granule release. Ultimately, this mechanistic knowledge can be used to direct inflammation and wound healing following biomaterial implantation to promote a more favorable healing response.

The dismal prognosis of pancreatic cancer has motivated research into identifying non-invasive 'liquid biopsy' biomarkers for early detection when treatment is most effective. Recently, exosomes—nanoscale membranous vesicles shed from tumour cells and which can be found circulating in the blood (and most bodily fluids)—have been discovered to contain a wealth of proteomic and genetic information, showing promise for pre-symptomatic screening and monitoring of disease. Here we examine recent findings highlighting the diagnostic value of exosomes in pancreatic cancer as well as the emerging use of lab-on-a-chip (LOC) technologies aiming to streamline exosome isolation and analysis.

Despite many years of effort from cancer biologists and clinical oncologists, pancreatic ductal adenocarcinoma (PDAC) remains a thoroughly recalcitrant disease, resisting both conventional forms of cancer treatment and radical innovative therapies. Perhaps driving the lack of success in PDAC is the underappreciation of the primary hallmark of the tumour: a fibrotic extracellular matrix (ECM) that composes a majority of the highly rigid solid carcinoma. In recent years we have come to understand that the homeostasis of ECM mechanics is pivotal for the homeostasis of cells and the progression or initiation of a malignant phenotype. This can be understood by way of mechanobiology, a field that attempts to understand how physical forces like ECM stiffness alter cell behaviour. In this review, we provide an overview of our understanding of PDAC from this perspective and the recent advances in biophysics and engineering that allow for new tools with which to investigate the mechanobiology of PDAC.

Polymorphonuclear leukocytes (PMNs) are recruited to sites of injury and biomaterial implants. Once activated, PMNs can exocytose their granule subsets to recruit monocytes (MCs) and mediate MC/macrophage activation. We investigated the release of myeloperoxidase (MPO), a primary granule marker, and matrix metalloproteinase-9 (MMP-9), a tertiary granule marker, from human blood-derived PMNs cultured on poly(ethylene glycol) (PEG) hydrogels, polydimethylsiloxane (PDMS), tissue culture polystyrene (TCPS) and gelatin–PEG (GP) hydrogels, with and without the presence of the bacterial peptide formyl-Met-Leu-Phe. Supernatants from PMN cultures on PEG-containing hydrogels (i.e., PEG and GP hydrogels) had higher concentrations of MPO than those from PMN cultures on PDMS or TCPS at 2 h. PMNs on all biomaterials released comparable levels of MMP-9 at 2 h, indicating that PMNs cultured on PEG-containing hydrogels have different mechanisms of release for primary and tertiary granules. Src family kinases were involved in the release of MPO from PMNs cultured on PEG hydrogels, TCPS and GP hydrogels and in the release of MMP-9 from PMNs cultured on all four biomaterials. The increased release of primary granules from PMNs on PEG-containing hydrogels did not significantly increase MC chemotaxis, indicating that additional co-effectors in the dynamic inflammatory milieu in vivo modulate PMN-mediated MC recruitment. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 4252–4261, 2014.