Engineering human mini-bones for the standardized modeling of healthy hematopoiesis, leukemia, and solid tumor metastasis

The bone marrow microenvironment provides indispensable factors to sustain blood production throughout life. It is also a hotspot for the progression of hematologic disorders and the most frequent site of solid tumor metastasis. Preclinical research relies on xenograft mouse models, but these models preclude the human-specific functional interactions of stem cells with their bone marrow microenvironment. Instead, human mesenchymal cells can be exploited for the in vivo engineering of humanized niches, which confer robust engraftment of human healthy and malignant blood samples. However, mesenchymal cells are associated with major reproducibility issues in tissue formation. Here, we report the fast and standardized generation of human mini-bones by a custom-designed human mesenchymal cell line. These resulting humanized ossicles (hOss) consist of fully mature bone and bone marrow structures hosting a human mesenchymal niche with retained stem cell properties. As compared to mouse bones, we demonstrate superior engraftment of human cord blood hematopoietic cells and primary acute myeloid leukemia samples and also validate hOss as a metastatic site for breast cancer cells. We further report the engraftment of neuroblastoma patient-derived xenograft cells in a humanized model, recapitulating clinically described osteolytic lesions. Collectively, our human mini-bones constitute a powerful preclinical platform to model bone-developing tumors using patient-derived materials.

Modeling Metastatic Colonization in a Decellularized Organ Scaffold-Based Perfusion Bioreactor

Metastatic cancer spread is responsible for most cancer-related deaths. To colonize a new organ, invading cells adapt to, and remodel, the local extracellular matrix (ECM), a network of proteins and proteoglycans underpinning all tissues, and a critical regulator of homeostasis and disease. However, there is a major lack in tools to study cancer cell behavior within native 3D ECM. Here, an in-house designed bioreactor, where mouse organ ECM scaffolds are perfused and populated with cells that are challenged to colonize it, is presented. Using a specialized bioreactor chamber, it is possible to monitor cell behavior microscopically (e.g., proliferation, migration) within the organ scaffold. Cancer cells in this system recapitulate cell signaling observed in vivo and remodel complex native ECM. Moreover, the bioreactors are compatible with co-culturing cell types of different genetic origin comprising the normal and tumor microenvironment. This degree of experimental flexibility in an organ-specific and 3D context, opens new possibilities to study cell-cell and cell-ECM interplay and to model diseases in a controllable organ-specific system ex vivo.

Basement membrane stiffness determines metastases formation

The basement membrane (BM) is a special type of extracellular matrix and presents the major barrier cancer cells have to overcome multiple times to form metastases. Here we show that BM stiffness is a major determinant of metastases formation in several tissues and identify netrin-4 (Net4) as a key regulator of BM stiffness. Mechanistically, our biophysical and functional analyses in combination with mathematical simulations show that Net4 softens the mechanical properties of native BMs by opening laminin node complexes, decreasing cancer cell potential to transmigrate this barrier despite creating bigger pores. Our results therefore reveal that BM stiffness is dominant over pore size, and that the mechanical properties of 'normal' BMs determine metastases formation and patient survival independent of cancer-mediated alterations. Thus, identifying individual Net4 protein levels within native BMs in major metastatic organs may have the potential to define patient survival even before tumour formation. The ratio of Net4 to laminin molecules determines BM stiffness, such that the more Net4, the softer the BM, thereby decreasing cancer cell invasion activity.

Decellularization of the Murine Cardiopulmonary Complex

We present here a decellularization protocol for mouse heart and lungs. It produces structural ECM scaffolds that can be used to analyze ECM topology and composition. It is based on a microsurgical procedure designed to catheterize the trachea and aorta of a euthanized mouse to perfuse the heart and lungs with decellularizing agents. The decellularized cardiopulmonary complex can subsequently be immunostained to reveal the location of structural ECM proteins. The whole procedure can be completed in 4 days. The ECM scaffolds resulting from this protocol are free of dimensional distortions. The absence of cells enables structural examination of ECM structures down to submicron resolution in 3D. This protocol can be applied to healthy and diseased tissue from mice as young as 4-weeks old, including mouse models of fibrosis and cancer, opening the way to determine ECM remodeling associated with cardiopulmonary disease.

Pancreatic cancer is suppressed by fibroblast-derived collagen I

Clinical implementation of anti-stromal therapies in pancreatic cancer has been delayed by unanticipated tumor-restraining properties of the desmoplastic stroma. In confronting these challenges, Chen et al. demonstrate in this issue of Cancer Cell that fibroblast-specific deletion of collagen I, in the background of oncogenic Kras-induced spontaneous murine pancreatic ductal adenocarcinoma, enhances immune suppression and accelerates progression of disease.

Author Correction: Decellularization and antibody staining of mouse tissues to map native extracellular matrix structures in 3D

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The STRIPAK Complex Regulates Response to Chemotherapy Through p21 and p27

The STRIPAK complex has been linked to a variety of biological processes taking place during embryogenesis and development, but its role in cancer has only just started to be defined. Here, we expand on previous work indicating a role for the scaffolding protein STRIP1 in cancer cell migration and metastasis. We show that cell cycle arrest and decreased proliferation are seen upon loss of STRIP1 in MDA-MB-231 cells due to the induction of cyclin dependent kinase inhibitors, including p21 and p27. We demonstrate that p21 and p27 induction is observed in a subpopulation of cells having low DNA damage response and that the p21^high/γH2AX^low ratio within single cells can be rescued by depleting MST3&4 kinases. While the loss of STRIP1 decreases cell proliferation and tumor growth, cells treated with low dosage of chemotherapeutics in vitro paradoxically escape therapy-induced senescence and begin to proliferate after recovery. This corroborates with already known research on the dual role of p21 and indicates that STRIP1 also plays a contradictory role in breast cancer, suppressing tumor growth, but once treated with chemotherapeutics, allowing for possible recurrence and decreased patient survival.

The Mini-Organo: A rapid high-throughput 3D coculture organotypic assay for oncology screening and drug development

BACKGROUND

The use of in vitro cell cultures is a powerful tool for obtaining key insights into the behaviour and response of cells to interventions in normal and disease situations. Unlike in vivo settings, in vitro experiments allow a fine-tuned control of a range of microenvironmental elements independently within an isolated setting. The recent expansion in the use of three-dimensional (3D) in vitro assays has created a number of representative tools to study cell behaviour in a more physiologically 3D relevant microenvironment. Complex 3D in vitro models that can recapitulate human tissue biology are essential for understanding the pathophysiology of disease.

AIM

The development of the 3D coculture collagen contraction and invasion assay, the "organotypic assay," has been widely adopted as a powerful approach to bridge the gap between standard two-dimensional tissue culture and in vivo mouse models. In the cancer setting, these assays can then be used to dissect how stromal cells, such as cancer-associated fibroblasts (CAFs), drive extracellular matrix (ECM) remodelling to alter cancer cell behaviour and response to intervention. However, to date, many of the published organotypic protocols are low-throughput, time-consuming (up to several weeks), and work-intensive with often limited scalability. Our aim was to develop a fast, high-throughput, scalable 3D organotypic assay for use in oncology screening and drug development.

METHODS AND RESULTS

Here, we describe a modified 96-well organotypic assay, the "Mini-Organo," which can be easily completed within 5 days. We demonstrate its application in a wide range of mouse and human cancer biology approaches including evaluation of stromal cell 3D ECM remodelling, 3D cancer cell invasion, and the assessment of efficacy of potential anticancer therapeutic targets. Furthermore, the organotypic assay described is highly amenable to customisation using different cell types under diverse experimental conditions.

CONCLUSIONS

The Mini-Organo high-throughput 3D organotypic assay allows the rapid screening of potential cancer therapeutics in human and mouse models in a time-efficient manner.

Cancer cells' ability to mechanically adjust to extracellular matrix stiffness correlates with their invasive potential

Increased tissue stiffness is a classic characteristic of solid tumors. One of the major contributing factors is increased density of collagen fibers in the extracellular matrix (ECM). Here, we investigate how cancer cells biomechanically interact with and respond to the stiffness of the ECM. Probing the adaptability of cancer cells to altered ECM stiffness using optical tweezers-based microrheology and deformability cytometry, we find that only malignant cancer cells have the ability to adjust to collagen matrices of different densities. Employing microrheology on the biologically relevant spheroid invasion assay, we can furthermore demonstrate that, even within a cluster of cells of similar origin, there are differences in the intracellular biomechanical properties dependent on the cells' invasive behavior. We reveal a consistent increase of viscosity in cancer cells leading the invasion into the collagen matrices in comparison with cancer cells following in the stalk or remaining in the center of the spheroid. We hypothesize that this differential viscoelasticity might facilitate spheroid tip invasion through a dense matrix. These findings highlight the importance of the biomechanical interplay between cells and their microenvironment for tumor progression.

Measurement of Mesenchymal Stem Cells Attachment to Endothelial Cells

Mesenchymal stem cells (MSCs) have shown profound therapeutic potential in tissue repair and regeneration. However, recent studies indicate that MSCs are largely entrapped in lungs after intravenous delivery and die shortly. The underlying mechanisms have been poorly understood. We have provided evidence to show that excess expression and activation of integrins in culture-expanded MSCs is a critical cause of MSCs adhesion to endothelial cells of the lung microarteries resulting in the entrapment of the cells ( Wang et al., 2015 ). Therefore, it may be meaningful to test the adhesive ability of MSCs to endothelial cells in vitro before intravenous administration to avoid their lung vascular obstructions. Here we report a simple method to measure MSCs attachment to endothelial cells.

YAP/TAZ-Dependent Reprogramming of Colonic Epithelium Links ECM Remodeling to Tissue Regeneration

Tissue regeneration requires dynamic cellular adaptation to the wound environment. It is currently unclear how this is orchestrated at the cellular level and how cell fate is affected by severe tissue damage. Here we dissect cell fate transitions during colonic regeneration in a mouse dextran sulfate sodium (DSS) colitis model, and we demonstrate that the epithelium is transiently reprogrammed into a primitive state. This is characterized by de novo expression of fetal markers as well as suppression of markers for adult stem and differentiated cells. The fate change is orchestrated by remodeling the extracellular matrix (ECM), increased FAK/Src signaling, and ultimately YAP/TAZ activation. In a defined cell culture system recapitulating the extracellular matrix remodeling observed in vivo, we show that a collagen 3D matrix supplemented with Wnt ligands is sufficient to sustain endogenous YAP/TAZ and induce conversion of cell fate. This provides a simple model for tissue regeneration, implicating cellular reprogramming as an essential element.

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The repairing epithelium can be isolated based on Sca1 expression

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Markers upregulated during tissue repair are expressed in the fetal intestine

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Mechano-transduction via FAK, Src, and YAP/TAZ facilitate efficient tissue repair

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YAP/TAZ activation is required and sufficient to induce cellular reprogramming

ISDoT: in situ decellularization of tissues for high-resolution imaging and proteomic analysis of native extracellular matrix

The extracellular matrix (ECM) is a master regulator of cellular phenotype and behavior. It has a crucial role in both normal tissue homeostasis and disease pathology. Here we present a fast and efficient approach to enhance the study of ECM composition and structure. Termed in situ decellularization of tissues (ISDoT), it allows whole organs to be decellularized, leaving native ECM architecture intact. These three-dimensional decellularized tissues can be studied using high-resolution fluorescence and second harmonic imaging, and can be used for quantitative proteomic interrogation of the ECM. Our method is superior to other methods tested in its ability to preserve the structural integrity of the ECM, facilitate high-resolution imaging and quantitatively detect ECM proteins. In particular, we performed high-resolution sub-micron imaging of matrix topography in normal tissue and over the course of primary tumor development and progression to metastasis in mice, providing the first detailed imaging of the metastatic niche. These data show that cancer-driven ECM remodeling is organ specific, and that it is accompanied by comprehensive changes in ECM composition and topological structure. We also describe differing patterns of basement-membrane organization surrounding different types of blood vessels in healthy and diseased tissues. The ISDoT procedure allows for the study of native ECM structure under normal and pathological conditions in unprecedented detail.

Relative Stiffness Measurements of Tumour Tissues by Shear Rheology

The microenvironment of solid tumours is a critical contributor to the progression of tumours and offers a promising target for therapeutic intervention (Cox and Erler, 2011; Barker et al., 2012 ; Cox et al., 2016; Cox and Erler, 2016). The properties of the tumour microenvironment vary significantly from that of the original tissue in both biochemistry and biomechanics. At present, the complex interplay between the biomechanical properties of the microenvironment and tumour cell phenotype is under intense investigation. The ability to measure the biomechanical properties of tumour samples from cancer models will increase our understanding of their importance in solid tumour biology. Here we report a simple method to measure the viscoelastic properties of tumour specimens using a controlled strain rotational rheometer.

Relative Stiffness Measurements of Cell-embedded Hydrogels by Shear Rheology in vitro

Hydrogel systems composed of purified extracellular matrix (ECM) components (such as collagen, fibrin, Matrigel, and methylcellulose) are a mainstay of cell and molecular biology research. They are used extensively in many applications including tissue regeneration platforms, studying organ development, and pathological disease models such as cancer. Both the biochemical and biomechanical properties influence cellular and tissue compatibility, and these properties are altered in pathological disease progression (Cox and Erler, 2011; Bonnans et al., 2014 ). The use of cell-embedded hydrogels in disease models such as cancer, allow the interrogation of cell-induced changes in the biomechanics of the microenvironment ( Madsen et al., 2015 ). Here we report a simple method to measure these cell-induced changes in vitro using a controlled strain rotational rheometer.

Hypoxia and loss of PHD2 inactivate stromal fibroblasts to decrease tumour stiffness and metastasis

Cancer-associated fibroblasts (CAFs) interact with tumour cells and promote growth and metastasis. Here, we show that CAF activation is reversible: chronic hypoxia deactivates CAFs, resulting in the loss of contractile force, reduced remodelling of the surrounding extracellular matrix and, ultimately, impaired CAF-mediated cancer cell invasion. Hypoxia inhibits prolyl hydroxylase domain protein 2 (PHD2), leading to hypoxia-inducible factor (HIF)-1α stabilisation, reduced expression of αSMA and periostin, and reduced myosin II activity. Loss of PHD2 in CAFs phenocopies the effects of hypoxia, which can be prevented by simultaneous depletion of HIF-1α. Treatment with the PHD inhibitor DMOG in an orthotopic breast cancer model significantly decreases spontaneous metastases to the lungs and liver, associated with decreased tumour stiffness and fibroblast activation. PHD2 depletion in CAFs co-injected with tumour cells similarly prevents CAF-induced metastasis to lungs and liver. Our data argue that reversion of CAFs towards a less active state is possible and could have important clinical implications.

STRIPAK components determine mode of cancer cell migration and metastasis

The contractile actomyosin cytoskeleton and its connection to the plasma membrane are critical for control of cell shape and migration. We identify three STRIPAK complex components, FAM40A, FAM40B and STRN3, as regulators of the actomyosin cortex. We show that FAM40A negatively regulates the MST3 and MST4 kinases, which promote the co-localization of the contractile actomyosin machinery with the Ezrin/Radixin/Moesin family proteins by phosphorylating the inhibitors of PPP1CB, PPP1R14A-D. Using computational modelling, in vitro cell migration assays and in vivo breast cancer metastasis assays we demonstrate that co-localization of contractile activity and actin-plasma membrane linkage reduces cell speed on planar surfaces, but favours migration in confined environments similar to those observed in vivo. We further show that FAM40B mutations found in human tumours uncouple it from PP2A and enable it to drive a contractile phenotype, which may underlie its role in human cancer.

The interaction between uPAR and vitronectin triggers ligand-independent adhesion signalling by integrins

The urokinase-type plasminogen activator receptor (uPAR) is a non-integrin vitronectin (VN) cell adhesion receptor linked to the plasma membrane by a glycolipid anchor. Through structure-function analyses of uPAR, VN and integrins, we document that uPAR-mediated cell adhesion to VN triggers a novel type of integrin signalling that is independent of integrin-matrix engagement. The signalling is fully active on VN mutants deficient in integrin binding site and is also efficiently transduced by integrins deficient in ligand binding. Although integrin ligation is dispensable, signalling is crucially dependent upon an active conformation of the integrin and its association with intracellular adaptors such as talin. This non-canonical integrin signalling is not restricted to uPAR as it poses no structural constraints to the receptor mediating cell attachment. In contrast to canonical integrin signalling, where integrins form direct mechanical links between the ECM and the cytoskeleton, the molecular mechanism enabling the crosstalk between non-integrin adhesion receptors and integrins is dependent upon membrane tension. This suggests that for this type of signalling, the membrane represents a critical component of the molecular clutch.

Regulation of polarized morphogenesis by protein kinase C iota in oncogenic epithelial spheroids

Protein kinase C iota (PKCι), a serine/threonine kinase required for cell polarity, proliferation and migration, is commonly up- or downregulated in cancer. PKCι is a human oncogene but whether this is related to its role in cell polarity and what repertoire of oncogenes acts in concert with PKCι is not known. We developed a panel of candidate oncogene expressing Madin-Darby canine kidney (MDCK) cells and demonstrated that H-Ras, ErbB2 and phosphatidylinositol 3-kinase transformation led to non-polar spheroid morphogenesis (dysplasia), whereas MDCK spheroids expressing c-Raf or v-Src were largely polarized. We show that small interfering RNA (siRNA)-targeting PKCι decreased the size of all spheroids tested and partially reversed the aberrant polarity phenotype in H-Ras and ErbB2 spheroids only. This indicates distinct requirements for PKCι and moreover that different thresholds of PKCι activity are required for these phenotypes. By manipulating PKCι function using mutant constructs, siRNA depletion or chemical inhibition, we have demonstrated that PKCι is required for polarization of parental MDCK epithelial cysts in a 3D matrix and that there is a threshold of PKCι activity above and below which, disorganized epithelial morphogenesis results. Furthermore, treatment with a novel PKCι inhibitor, CRT0066854, was able to restore polarized morphogenesis in the dysplastic H-Ras spheroids. These results show that tightly regulated PKCι is required for normal-polarized morphogenesis in mammalian cells and that H-Ras and ErbB2 cooperate with PKCι for loss of polarization and dysplasia. The identification of a PKCι inhibitor that can restore polarized morphogenesis has implications for the treatment of Ras and ErbB2 driven malignancies.

miR-23b regulates cytoskeletal remodeling, motility and metastasis by directly targeting multiple transcripts

Uncontrolled cell proliferation and cytoskeletal remodeling are responsible for tumor development and ultimately metastasis. A number of studies have implicated microRNAs in the regulation of cancer cell invasion and migration. Here, we show that miR-23b regulates focal adhesion, cell spreading, cell-cell junctions and the formation of lamellipodia in breast cancer (BC), implicating a central role for it in cytoskeletal dynamics. Inhibition of miR-23b, using a specific sponge construct, leads to an increase of cell migration and metastatic spread in vivo, indicating it as a metastatic suppressor microRNA. Clinically, low miR-23b expression correlates with the development of metastases in BC patients. Mechanistically, miR-23b is able to directly inhibit a number of genes implicated in cytoskeletal remodeling in BC cells. Through intracellular signal transduction, growth factors activate the transcription factor AP-1, and we show that this in turn reduces miR-23b levels by direct binding to its promoter, releasing the pro-invasive genes from translational inhibition. In aggregate, miR-23b expression invokes a sophisticated interaction network that co-ordinates a wide range of cellular responses required to alter the cytoskeleton during cancer cell motility.

Arkadia regulates tumor metastasis by modulation of the TGF-β pathway

TGF-β can act as a tumor suppressor at early stages of cancer progression and as a tumor promoter at later stages. The E3 ubiquitin ligase Arkadia (RNF111) is a critical component of the TGF-β signaling pathway, being required for a subset of responses, those mediated by Smad3-Smad4 complexes. It acts by mediating ligand-induced degradation of Ski and SnoN (SKIL), which are 2 potent transcriptional repressors. Here, we investigate the role of Arkadia in cancer using model systems to address both potential tumor-suppressive and tumor-promoting roles. Stable reexpression of Arkadia in lung carcinoma NCI-H460 cells, which we show contain a hemizygous nonsense mutation in the Arkadia/RNF111 gene, efficiently restored TGF-β-induced Smad3-dependent transcription, and substantially decreased the ability of these cells to grow in soft agar in vitro. However, it had no effect on tumor growth in vivo in mouse models. Moreover, loss of Arkadia in cancer cell lines and human tumors is rare, arguing against a prominent tumor-suppressive role. In contrast, we have uncovered a potent tumor-promoting function for Arkadia. Using 3 different cancer cell lines whose tumorigenic properties are driven by TGF-β signaling, we show that loss of Arkadia function, either by overexpression of dominant negative Arkadia or by siRNA-induced knockdown, substantially inhibited lung colonization in tail vein injection experiments in immunodeficient mice. Our findings indicate that Arkadia is not critical for regulating tumor growth per se, but is required for the early stages of cancer cell colonization at the sites of metastasis.

Cancer dissemination--lessons from leukocytes

Cancer cells can move through tissues in a variety of different ways. In some cases, an epithelial-to-mesenchymal transition enables cancer cells to acquire fibroblast-like migratory properties. However, it is also becoming apparent that some cancer cells move in an amoeboid way similar to leukocytes. This theme will be the focus of the review, where we will discuss the similarities and differences between the mechanisms used by cancer cells and leukocytes to cross parenchymal basement membranes, move through interstitial tissue, and enter and exit the vasculature. Further, we propose that the ability to switch between different migratory mechanisms is critical for cells to relocate from one tissue to another.

Limited inter- and intra-patient sequence diversity of the genetic lineage A human metapneumovirus fusion gene

Human metapneumovirus (hMPV) is associated with respiratory tract illness especially in young children. Two hMPV genetic lineages, A and B, and four sublineages A1, A2 and B1, B2 have been defined. Infection with hMPV occurs through membrane fusion mediated by the hMPV fusion (F) protein. In this study, the inter- and intra-patient genetic diversity of the lineage A hMPV F gene was investigated. Ten isolates were collected from 10 hMPV infected children. Viral RNA was isolated and amplified, and approximately 10 clones from each isolate were sequenced. Altogether 108 clones were successfully sequenced. The average interpatient sequence diversity was 1.68% and 1.64% at nucleotide and amino acid levels, respectively. The samples were divisible into two groups on the basis of intrapatient sequence diversity. In group 1 (4 children) the intra-patient sequence diversity was low (nt: 0.26-0.39%, aa: 0.51-0.94%) whereas group 2 (6 children) had a higher intra-patient sequence diversity (nt: 0.85-1.98%, aa: 1.08-2.22%). Phylogenetic analyses showed that the group 1 children harboured sublineage Al only, but interestingly group 2 children harboured both sublineages Al and A2, indicating they had been infected with at least two viruses. Several independent viruses contained premature stop codons in exactly identical positions resulting in truncated fusion proteins. Possibly this is a mechanism for immune system evasion. The F protein is a major antigenic determinant, and the limited sequence diversity observed lay emphasis on the hMPV F gene as a putative target for future vaccine development.

Clathrin and LRP-1-independent constitutive endocytosis and recycling of uPAR

Background

The urokinase receptor (uPAR/CD87) is highly expressed in malignant tumours. uPAR, as a GPI anchored protein, is preferentially located at the cell surface, where it interacts with its ligands urokinase (uPA) and the extracellular matrix protein vitronectin, thus promoting plasmin generation, cell-matrix interactions and intracellular signalling events. Interaction with a complex formed by uPA and its inhibitor PAI-1 induces cell surface down regulation and recycling of the receptor via the clathrin-coated pathway, a process dependent on the association to LRP-1.

Methodology/Principal Findings

In this study, we have found that along with the ligand-induced down-regulation, uPAR also internalizes and recycles constitutively through a second pathway that is independent of LRP-1 and clathrin but shares some properties with macropinocytosis. The ligand-independent route is amiloride-sensitive, does not require uPAR partitioning into lipid rafts, is independent of the activity of small GTPases RhoA, Rac1 and Cdc42, and does not require PI3K activity. Constitutively endocytosed uPAR is found in EEA1 positive early/recycling endosomes but does not reach lysosomes in the absence of ligands. Electron microscopy analysis reveals the presence of uPAR in ruffling domains at the cell surface, in macropinosome-like vesicles and in endosomal compartments.

Conclusions/Significance

These results indicate that, in addition to the ligand-induced endocytosis of uPAR, efficient surface expression and membrane trafficking might also be driven by an uncommon macropinocytic mechanism coupled with rapid recycling to the cell surface.

Monomer dimer dynamics and distribution of GPI-anchored uPAR are determined by cell surface protein assemblies

To search for functional links between glycosylphosphatidylinositol (GPI) protein monomer–oligomer exchange and membrane dynamics and confinement, we studied urokinase plasminogen activator (uPA) receptor (uPAR), a GPI receptor involved in the regulation of cell adhesion, migration, and proliferation. Using a functionally active fluorescent protein–uPAR in live cells, we analyzed the effect that extracellular matrix proteins and uPAR ligands have on uPAR dynamics and dimerization at the cell membrane. Vitronectin directs the recruitment of dimers and slows down the diffusion of the receptors at the basal membrane. The commitment to uPA–plasminogen activator inhibitor type 1–mediated endocytosis and recycling modifies uPAR diffusion and induces an exchange between uPAR monomers and dimers. This exchange is fully reversible. The data demonstrate that cell surface protein assemblies are important in regulating the dynamics and localization of uPAR at the cell membrane and the exchange of monomers and dimers. These results also provide a strong rationale for dynamic studies of GPI-anchored molecules in live cells at steady state and in the absence of cross-linker/clustering agents.

uPAR-induced cell adhesion and migration: vitronectin provides the key

Expression of the membrane receptor uPAR induces profound changes in cell morphology and migration, and its expression correlates with the malignant phenotype of cancers. To identify the molecular interactions essential for uPAR function in these processes, we carried out a complete functional alanine scan of uPAR in HEK293 cells. Of the 255 mutant receptors characterized, 34 failed to induce changes in cell morphology. Remarkably, the molecular defect of all of these mutants was a specific reduction in integrin-independent cell binding to vitronectin. A membrane-tethered plasminogen activator inhibitor-1, which has the same binding site in vitronectin as uPAR, replicated uPAR-induced changes. A direct uPAR–vitronectin interaction is thus both required and sufficient to initiate downstream changes in cell morphology, migration, and signal transduction. Collectively these data demonstrate a novel mechanism by which a cell adhesion molecule lacking inherent signaling capability evokes complex cellular responses by modulating the contact between the cell and the matrix without the requirement for direct lateral protein–protein interactions.

Presence and significance of TT virus in Danish patients on maintenance hemodialysis

OBJECTIVES

To determine the prevalence of TT virus (TTV) in a population of Danish hemodialysis patients and evaluate possible relations between TTV infection and elevated levels of C-reactive protein (CRP) and hypo-response to treatment with erythropoietin (EPO).

MATERIAL AND METHODS

Patients on maintenance hemodialysis at a single center were invited to participate. Demographic and clinical data were registered. Blood samples for virological and routine biochemical tests were drawn simultaneously. TTV DNA was detected using polymerase chain reaction (PCR). TTV viral load was estimated by means of semi-quantitative PCR. All patients were tested for hepatitis B, hepatitis C and GB virus C.

RESULTS

Of 252 patients, 204 (80.9%) gave their written informed consent to participate in the study. The prevalence of TTV was 68% and 50% of TTV-positive patients had a high TTV viral load. TTV-positive patients were significantly older than TTV-negative patients (p = 0.011). No relations were found between TTV infection and elevated levels of alanine aminotransferase (ALT) or CRP or hypo-response to EPO treatment. The mean hemoglobin concentration was 11.24 +/- 1.48 g/dl. Patients with a high TTV viral load had a lower level of hemoglobin (10.86 +/- 1.47 g/dl) than the others (p = 0.01). This trend suggested a positive relation between TTV infection and the number of blood transfusions. A restriction fragment length polymorphism assay suggested that patients were infected with different TTV strains.

CONCLUSIONS

TTV is common in patients on maintenance hemodialysis. The presence of TTV is associated with increasing age. Patients with a high TTV viral load had lower levels of hemoglobin than the others. TTV infection is not related to elevated levels of ALT or CRP or to hypo-response to EPO treatment.

TTV viral load as a marker for immune reconstitution after initiation of HAART in HIV-infected patients

PURPOSE

To investigate whether TT virus (TTV) viral load may be used as a surrogate marker for functional immune reconstitution in HIV-infected patients receiving highly active antiretroviral therapy (HAART).

METHOD

Fifteen protease inhibitor-naïve HIV-infected patients were included in a longitudinal study. From each patient, three serum samples taken before HAART initiation and three samples taken during HAART were analyzed. TTV was detected by polymerase chain reaction (PCR) and was quantitated by competitive PCR. TTV viral heterogeneity was determined by restriction fragment length polymorphisms (RFLPs) and sequencing.

RESULTS

All 15 HIV-infected patients were TTV positive. No significant change in HIV RNA or TTV viral load was observed at the three time points before HAART initiation. Even though HAART lead to an immediate and significant reduction in HIV RNA (p =.0001), a significant reduction in TTV viral load (p =.0002) was not observed until after 3-5 months of HAART. Four patients did not have an increase in CD4+ T cell count after 1 year of HAART; however, a decrease in TTV viral load was still observed, and three of these patients had a reduction in HIV RNA. RFLPs and sequencing revealed that TTV is represented as a heterogeneous population of virus in HIV-infected patients.

CONCLUSION

This pilot study suggests that HAART leads to improved immunological responses, even in patients who do not have an increase in CD4+ T cell counts. We propose that the change in TTV viral load may be useful in the evaluation of cellular immune response at a functional level in HIV-infected patients who receive HAART.

Bone mineral content and body composition in children and young adults with cystic fibrosis

With dual energy X-ray absorptiometry (DEXA), it is possible to quantitate important aspects of growth in children with cystic fibrosis (CF), supplementing the usual measures of height and weight. Of particular concern during growth is the accumulation of bone mineral, since osteoporosis and fractures are well-recognized problems in end-stage disease. Various measures of growth and body composition were examined in 40 children and young adults (ages 5.7-20.3 years, mean 11.9 years) and compared to age-, gender-, and race-matched normal controls. The mean (+/- SE) weight Z-score of the 40 CF patients was -0.70 +/- 0.11, and the mean height Z-score was -0.66 +/- 0.15. Relative to their matched normal controls, the CF patients had a deficit in total body bone mineral averaging 19.1% +/- 3.0%. The deficits in total body bone mineral correlated with pulmonary and nutritional measures of disease severity. Serum vitamin D levels, calcium intake, age, gender, use of steroids, and CF genotype were not found to be significant factors. In this group of children and young adults with CF, height and weight measures of growth were not dramatically reduced (mean Z-scores = -0.7), yet large deficits in total body bone mineral averaging nearly 20% were identified.

Longitudinal evaluation of bone mineral density in children receiving chemotherapy

PURPOSE

Some children who survive a childhood malignancy have diminished bone mineral density (BMD). The purpose of this study is to assess when, and perhaps why, this problem develops.

PATIENTS AND METHODS

BMD was longitudinally monitored in 37 children for a minimum of 1 year (mean, 23.4 months; range, 12 to 41 months) during and, in some cases, after chemotherapy. Evaluations included serum analyses (vitamin D, calcium, and alkaline phosphatase), assessment of calcium intake, and measures of growth and nutrition (height, weight, and skinfolds).

RESULTS

BMD was already diminished at the start of treatment in some patients; 6 of 13 patients (46%) had a BMD z score in the hip or spine of < -1.0. However, only 1 patient (8%) was < -2.0. Most patients did not have a significant drop in BMD z scores during chemotherapy, but one in four did decrease at least 0.5 standard deviations. Age greater than 10 years, a drop in height z score, and treatment with cranial irradiation correlated with a drop in BMD z scores during treatment. In the year immediately after completion of chemotherapy, no consistent "catch-up" was observed in BMD z scores.

CONCLUSIONS

In some patients, BMD z scores are diminished at the time of diagnosis and a drop may occur during treatment in others. Multiple factors related to the disease process and treatment likely contribute to these observations. Cranial irradiation, perhaps by impacting on growth hormone homeostasis, is one such factor. Fortunately, most survivors of a childhood malignancy will not have large deficits in BMD later in life.

Calcium intake in children with positive IgG RAST to cow's milk

OBJECTIVE

This study was made to: (i) identify the prevalence of low calcium intakes in a paediatric population with loosely defined 'milk allergy'; and (ii) assess long-term (mean 21 months later) changes in calcium intake following a single nutrition counselling session with those patients initially found to have a low intake.

METHODOLOGY

Calcium intake was assessed in a cross-sectional study of 58 patients ages 5-16 years (mean 9.9 years) with IgG radioallergosorbent test (RAST) class II or higher for cow's milk protein. Those 31 patients found to have a low calcium intake were prospectively re-evaluated 12-30 months later following a single nutrition counselling session.

RESULTS

Calcium intake was < recommended dietary allowance (RDA) for 31 of 58 (53%) patients. The patient's perception of their intake was unreliable; 44% of those who rated their calcium intake fair or good did not meet their RDA. Taking a calcium supplement did not ensure adequate intake; 21% of those taking supplements still did not meet their RDA. Milk intake predicted calcium intake; 8% of those who did not drink milk vs 68% of those who did drink at least some milk met their RDA without supplementation. The 31 patients with low intakes received counselling and were re-evaluated at an average follow-up of nearly 2 years. Calcium intake was increased a mean of 360 mg/day and use of supplements increased from 10 to 52% of the group. Despite these positive changes, 48% still did not meet their RDA.

CONCLUSION

Limited milk intake is likely to be associated with suboptimal calcium intake. Efforts should be made to educate the family about the importance of calcium and its non-dairy sources. With many families repeated discussions of this issue may be necessary to influence calcium intake.

Quality-of-life and formal functional testing of survivors of out-of-hospital cardiac arrest correlates poorly with traditional neurologic outcome scales

STUDY HYPOTHESIS

The traditional (and unvalidated) five-point Cerebral Performance Category (CPC) score at hospital discharge does not correlate with the results yielded by a validated functional status instrument and subjective quality-of-life assessment.

METHODS

We compared CPC scores with the results of prospective standardized testing after discharge in survivors of out-of-hospital cardiac arrest. Consenting survivors were tested with the validated Functional Status Questionnaire (FSQ), a subjective quality-of-life assessment, and traditional CPC scoring.

RESULTS

Of the 3,130 arrests during the 52 months of the study, 93 patients survived. Thirty-five patients were tested (71% of those eligible at the time of follow-up). Of these patients, 34% said their quality of life was worse, 38% said it was the same, and 28% said it was better than before the cardiac arrest. Fifty-four percent of patients scored normally on all FSQ subscales, but the remainder had an average 2.1 areas (of 6) with significant impairment. CPC score correlated very poorly with quality-of-life rating and with all scores and subscores on the FSQ. A CPC of 1 on discharge (supposedly normal function) had a sensitivity of 78%, a specificity of 43%, a positive predictive value of 64%, and a negative predictive value of 60% for quality of life the same as or better than that before arrest. With regard to ability to predict the presence of any major areas of impairment on the FSQ, the respective figures were 32%, 43%, 43%, and 32%.

CONCLUSION

The CPC score, relied on as a measure of functional outcome in cardiac arrest, correlates poorly with subsequent subjective quality of life and with validated objective functional testing instruments, and conclusions based on it are suspect. Future researchers should employ standardized testing instruments.

Bone density in survivors of childhood malignancies

PURPOSE

The purpose of this study was to assess bone mineralization in survivors of childhood malignancies.

PATIENTS AND METHODS

Bone mineral density (BMD) of the lumbar spine was measured in 60 patients aged 5.5-20.1 years (mean, 12.4 years) who had no known disease 1.0-14.5 years (mean, 4.3 years) after completing treatment for a malignancy. The age-normalized BMD findings (Z scores) were correlated with multiple variables, including measures of growth and nutrition, type of malignancy, and various treatments, including use of steroids, methotrexate, or cranial irradiation.

RESULTS

BMD was normal in most patients with a mean Z score of -0.28 + 0.14 (+/- SE). Only 8% of the patients were more than 2 SDs below age-matched normal BMD. Weight Z score was the major determinant of BMD Z score. Calcium intake and height Z score were also important variables.

CONCLUSIONS

Most survivors of childhood malignancies will not be left with a clinically significant deficit in BMD. Risk factors for diminished BMD include low-weight and low-height Z scores and low calcium intake. Therapeutic interventions are available to address these risk factors in those patients with significantly diminished BMD.

Relationship of timeliness of paramedic advanced life support interventions to outcome in out-of-hospital cardiac arrest treated by first responders with defibrillators

STUDY OBJECTIVE

We sought to determine whether the interval between the arrival of first responder/defibrillators and paramedic advanced life support (ALS) interventions is associated with outcome.

METHODS

We carried out a prospective observational study of adults in out-of-hospital cardiac arrest treated by both first responders and paramedics in an urban emergency medical services system between July 15, 1992, and May 27, 1993 (N = 544).

RESULTS

The gap between first-responder and medic arrival was short (3.2 minutes); medics arrived before first-responder shock in 22% of ventricular fibrillation (VF) cases. Just 10% of patients has a pulse when medics arrived, but the presence of pulse on medic arrival was a powerful predictor of hospital discharge (odds ratio [OR], 20.5; sensitivity, 39%; specificity, 98%; positive predictive value, 55%; negative predictive value, 97%) or a Cerebral Performance Category score on discharge of 1 or 2 (OR, 2.9). No response or individual ALS treatment interval was related to outcome, including the interval from first-responder to medic arrival. ALS interventions by medics were associated with poorer outcomes; even the need for nothing more than additional defibrillation by medics decreased the survival rate of VF patients threefold. By contrast, bystander CPR improved survival more than fourfold and early defibrillation of VF by first responders more than ninefold. Ninety-one percent of all patients discharged from the hospital who received only minimal ALS other than intubation had good neurologic outcome and longer survival after discharge. Half the total survivors of VF arrest (and 59% of all arrest survivors) were resuscitated by medics with aggressive ALS measures, but 80% had very poor neurologic outcomes and 50% died within a year of hospital discharge. Even the need for only additional defibrillation by medics worsened neurologic outcome by a factor of 2.8.

CONCLUSION

Faster response by medics, or any individual ALS intervention other than first-responder defibrillation, demonstrated no benefit in this urban population with short intervals between responder arrivals. Aggressive ALS increased the number of survivors but also decreased their neurologic quality. The benefit of rapid ALS backup to first responder/defibrillators needs further study in other systems. System performance cannot be judged without knowledge of neurologic outcome.

Bone density in children and adolescents with cystic fibrosis

OBJECTIVE

To assess bone mineralization in children and adolescents with cystic fibrosis.

DESIGN

A cross-sectional, observational study of bone mineral density (BMD) in the lumbar vertebrae and the proximal femur of 62 patients aged 4.9 to 17.8 years (mean, 10.7 years). The age-normalized BMD findings (z scores) were correlated with multiple variables, including measures of pulmonary disease, nutritional status and growth, genotype, calcium intake, and serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels.

RESULTS

The mean BMD z score was -1.03 +/- 0.14 (+/- SE) in the lumbar vertebrae and -0.71 +/- 0.17 in the proximal femur. The BMD in this age range declined relative to normal values at a rapid rate of roughly 1 SD every 6 to 8 years. The BMD z scores correlated well with multiple measures of disease severity, particularly weight and forced expiratory volume in 1 second.

CONCLUSIONS

Significant osteoporosis in adults with CF results at least in part from a failure to accumulate bone mineral at a normal rate during skeletal growth and development. The cause of this is likely multifactorial. With increasing longevity, the skeletal consequences of CF become an important consideration.

A comparison of adenosine and verapamil for the treatment of supraventricular tachycardia in the prehospital setting

STUDY OBJECTIVE

To compare the efficacy and base hospital physician use of adenosine with that of verapamil in the prehospital treatment of supraventricular tachycardia (SVT).

DESIGN

A 12-month prospective chart review of adenosine administration and a 12-month retrospective chart review of verapamil administration.

SETTING

A single-tier advanced life support emergency medical service system.

PARTICIPANTS

Prehospital adult patients presenting with narrow-complex SVT.

INTERVENTIONS

Field paramedics identified SVT. They then administered verapamil or adenosine under on-line physician medical control. Paramedics administered up to two i.v. doses of verapamil, 2.5 mg and 5 mg, or up to two i.v. doses of adenosine, 6 mg and 12 mg. They recorded ECG readings; blood pressure; pulse; respirations; and symptoms before, during, and after drug administration.

RESULTS

During the verapamil period, paramedics identified 102 cases of SVT and administered verapamil to 17 patients. Review by a cardiologist revealed 6 of the 17 patients to have been in atrial fibrillation, atrial tachycardia, or sinus tachycardia. Of the remaining 11 patients, 7 (64%) converted from SVT to sinus rhythm. During the adenosine period, paramedics identified 89 cases of SVT, and they administered adenosine to 64 patients. Eight patients had no review because prehospital rhythm strips were lost. Of the remaining 56 patients, 24 were later determined to have been in atrial fibrillation, atrial tachycardia, sinus tachycardia, atrial flutter, or ventricular tachycardia. Of the remaining 32 patients who were in SVT, adenosine converted 25 (78%) to sinus rhythm. An important incidental finding was the misinterpretation of tachydysrhythmias in 30 of 73 patients by paramedics and base hospital physicians.

CONCLUSION

Our study showed no difference in conversion rates between verapamil and adenosine. Base hospital physicians were more likely to order adenosine than verapamil. Paramedics and base hospital physicians often misinterpret tachydysrhythmias.

A randomized clinical trial of active compression-decompression CPR vs standard CPR in out-of-hospital cardiac arrest in two cities

OBJECTIVE

To compare the effectiveness of active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) with a handheld suction device vs standard manual CPR in victims of out-of-hospital cardiopulmonary arrest.

DESIGN

Prospective randomized clinical trial with crossover group design.

SETTING

Emergency medical services (EMS) of a large (San Francisco) and medium-sized (Fresno) city in California.

PATIENTS

All normothermic adult victims of out-of-hospital, nontraumatic cardiac arrest on whom CPR was performed by first responders.

INTERVENTION

Patients were randomized to receive either standard manual CPR according to American Heart Association guidelines or ACD CPR, on first-responder contact.

MAIN OUTCOME MEASURES

Return of spontaneous circulation, admission to the intensive care unit, survival to hospital discharge, and neurological function at hospital discharge.

RESULTS

The ACD group (n = 117 in Fresno; n = 297 in San Francisco) and standard group (n = 136 in Fresno; n = 310 in San Francisco) were similar with regard to demographic and prognostic variables, such as age, witnessed arrest and bystander CPR frequency, and initial cardiac rhythm. Average interval from 911 call activation to EMS responder arrival was 6.4 minutes in Fresno and 4.0 minutes in San Francisco. In Fresno, there was no difference between the ACD group and standard CPR group in return of spontaneous circulation (17% vs 20%; P = .68), hospital admission (16% vs 20%; P = .56), hospital discharge (5% vs 7%; P = .64), or cerebral performance category score at discharge (1.5 vs 1.6; P = .90). Similarly, in San Francisco there was no difference between the ACD group and standard CPR group in return of spontaneous circulation (19% vs 21%; P = .65), hospital admission (13.5% vs 14.5%; P = .79), hospital discharge (4.7% vs 5.5%; P = .80), or cerebral performance category score at discharge (2.2 vs 2.6; P = .31). There was no increase in significant complications associated with the use of ACD CPR.

CONCLUSION

There was no improvement in outcome with ACD CPR in out-of-hospital cardiac arrest in these two cities. Differences in study design, demographics, EMS systems, response intervals, training, and technique performance may contribute to the lack of improvement in initial resuscitation with ACD CPR compared with previous studies. Future research needs to control these variables to determine the reason for these differences in outcome.

A randomized clinical trial of high-dose epinephrine and norepinephrine vs standard-dose epinephrine in prehospital cardiac arrest

OBJECTIVE

To determine the relative efficacy of high- vs standard-dose catecholamines in initial treatment of prehospital cardiac arrest.

DESIGN

Randomized, prospective, double-blind clinical trial.

SETTING

Prehospital emergency medical system of a major US city.

PATIENTS

All adults in nontraumatic cardiac arrest, treated by paramedics, who would receive epinephrine according to American Heart Association advanced cardiac life support guidelines.

INTERVENTIONS

High-dose epinephrine (HDE, 15 mg), high-dose norepinephrine bitartrate (NE, 11 mg), or standard-dose epinephrine (SDE, 1 mg) was blindly substituted for advanced cardiac life support doses of epinephrine.

MAIN OUTCOME MEASURES

Restoration of spontaneous circulation in the field, admission to hospital, hospital discharge, and Cerebral Performance Category score.

RESULTS

Of 2694 patients with cardiac arrests during the study period, resuscitation was attempted on 1062 patients. Of this total, 816 patients met study criteria and were enrolled. In the entire cardiac arrest population, 63% of the survivors were among the 11% of patients who were defibrillated by first responders. The three drug treatment groups were similar for all independent variables. Thirteen percent of patients receiving HDE regained a pulse in the field vs 8% of those receiving SDE (P = .01), and 18% of HDE patients were admitted to the hospital vs 10% of SDE patients who were admitted to the hospital (P = .02). Similar trends for NE were not significant. There were 18 survivors; 1.7% of HDE patients and 2.6% of NE patients were discharged from the hospital compared with 1.2% of SDE patients, but this was not significant (P = .37; beta = .38). There was a nonsignificant trend for Cerebral Performance Category scores to be worse for HDE (3.2) and NE patients (3.7) than for SDE patients (2.3) (P = .10; beta = .31). No significant complications were identified. High-dose epinephrine did not produce longer hospital or critical care unit stays.

CONCLUSIONS

High-dose epinephrine significantly improves the rate of return of spontaneous circulation and hospital admission in patients who are in prehospital cardiac arrest without increasing complications. However, the increase in hospital discharge rate is not statistically significant, and no significant trend could be determined for neurological outcome. No benefit of NE compared with HDE was identified. Further study is needed to determine the optimal role of epinephrine in prehospital cardiac arrest.