3-dimensional Matrices Research Articles

A multiblock PLS model of cortico-cortical and corticomuscular interactions in Parkinson's disease

Electroencephalography (EEG) and simultaneously-recorded electromyography (EMG) data are a means to assess integrity of the functional connection between the cortex and the muscle during movement. EEG-EMG coupling is typically assessed with pair-wise squared coherence, resulting in a small, but statistically-significant coherence between a single EEG and a single EMG channel. However, a means to combine results across subjects is not straightforward with this approach because the exact frequency of maximal EEG-EMG coupling may vary between individuals, and it emphasizes the role of an individual locus in the brain in driving the muscle activity, when interactions between head regions may in fact be more influential on ongoing EMG activity. To deal with these issues, we implemented a multiblock Partial Least Squares (mbPLS) procedure, previously proposed in chemical applications, which incorporates a hierarchical structure into the ordinary two-block PLS often used in neuroimaging studies. In the current implementation, each subject's data features are collected in individual data blocks on a sub-level, while simultaneously aggregating the sub-level information to obtain a super-level group "consensus". We further extended the mbPLS model to include 3-dimensional matrices: time-frequency-EEG channel and a time-frequency-connection utilizing Partial Directed Coherence (PDC). We applied the proposed method to concurrent EEG and EMG data collected from ten normal subjects and nine patients with mild-moderate Parkinson's disease (PD) performing a dynamic motor task-that of sinusoidal squeezing. The results demonstrate that connections between EEG electrodes, rather than activity at individual electrodes, correspond more closely to ongoing EMG activity. In PD subjects, there was enhanced connectivity to and from occipital regions, likely related to the previously-described enhanced use of visual information during motor performance in this group. The proposed mbPLS framework is a promising technique for performing multi-subject, multi-modal data analysis and it allows for robust group inferences even in the face of large inter-subject variability.

Development of a novel microfluidic device for long-term in situ monitoring of live cells in 3-dimensional matrices

Using the latest innovations in microfabrication technology, 3-dimensional microfluidic cell culture systems have been developed as an attractive alternative to traditional 2-dimensional culturing systems as a model for long-term microscale cell-based research. Most microfluidic systems are based on the embedding of cells in hydrogels. However, physiologically realistic conditions based on hydrogels are difficult to obtain and the systems are often too complicated. We have developed a microfluidic cell culture device that incorporates a biodegradable rigid 3D polymer scaffold using standard soft lithography methods. The device permits repeated high-resolution fluorescent imaging of live cell populations within the matrix over a 4week period. It was also possible to track cell development at the same spatial location throughout this time. In addition, human primary periodontal ligament cells were induced to produce quantifiable calcium deposits within the system. This simple and versatile device should be readily applicable for cell-based studies that require long-term culture and high-resolution bioimaging.

PH regulators in invadosomal functioning: Proton delivery for matrix tasting

Invadosomes are actin-rich finger-like cellular structures sensing and interacting with the surrounding extracellular matrix (ECM) and involved in its proteolytic remodeling. Invadosomes are structures distinct from other adhesion complexes, and have been identified in normal cells that have to cross tissue barriers to fulfill their function such as leukocytes, osteoclasts and endothelial cells. They also represent features of highly aggressive cancer cells, allowing them to escape from the primary tumor, to invade surrounding tissues and to reach systemic circulation. They are localized to the ventral membrane of cells grown under 2-dimensional conditions and are supposed to be present all around cells grown in 3-dimensional matrices. Indeed invadosomes are key structures in physiological processes such as inflammation and the immune response, bone remodeling, tissue repair, but also in pathological conditions such as osteopetrosis and the development of metastases. Invadosomes are subdivided into podosomes, found in normal cells, and into invadopodia specific for cancer cells. While these two structures exhibit differences in organization, size, number and half-life, they share similarities in molecular composition, participation in cell-matrix adhesion and promoting matrix degradation. A key determinant in invadosomal function is the recruitment and release of proteases, such as matrix metalloproteinases (MMPs), serine proteases and cysteine cathepsins, together with their activation in a tightly controlled and highly acidic microenvironment. Therefore numerous pH regulators such as V-ATPases and Na+/H+ exchangers, are found in invadosomes and are directly involved in their constitution as well as their functioning. This review focuses on the participation of pH regulators in invadosome function in physiological and pathological conditions, with a particular emphasis on ECM remodeling by osteoclasts during bone resorption and by cancer cells.

Abstract 5269: Cell matrix interactions in a 3D alginate cell culture system

Abstract The use of 3-dimensional (3D) matrices for cell culture is gaining popularity as a substitute for traditional 2D cell culture as it can enable formation of multi-cellular structures and a more biologically relevant cell-cell contact such as found in tissues, organs and tumors. NovaMatrix®-3D is an alginate-based cell culture system comprising an alginate foam matrix and an alginate immobilizing solution. Cells are entrapped throughout the alginate foam by first suspending them in a solution of sodium alginate that is applied to the foam. As the foam absorbs the suspension, in situ gelation occurs as calcium ions are donated from the foam cross-linking the added alginate forming a hydrogel in the pores of the foam comprising the cells. Cells do not have receptors that recognize alginate molecules and this may stimulate formation of spheroids. However, some cells require signaling molecules and matrix interaction in order to proliferate. This was evaluated by culturing cells in the presence of alginate to which the peptide sequence RGD (Arg-Gly-Asp) was covalently attached (RGD-alginate) thereby facilitating a signaling cascade via integrin-RGD interaction. Various cell lines were first cultured in 2D then prepared as a suspension in 0.5 - 1% alginate or RGD-alginate in cell culture medium. An aliquot of each cell suspension was added to γ-sterilized NovaMatrix®-3D foams. NHIK 3025 (human cervix carcinoma), OVCAR-3 (human ovarian adenocarcinoma), SKOV-3 (human ovarian carcinoma), NIH:3T3 (murine fibroblasts), C2C12 (murine myoblasts), V79-379A (hamster lung fibroblast) and MDCK (Madin Darby canine kidney) were used and single cells were immobilized in the alginate foams. Cell localization within the foam was visualized using confocal microscopy to identify fluorescently labeled (CellTrace™ CFSE) cells. Cell proliferation was measured by counting cells after de-gelling the foam using sodium citrate. Cell proliferation and spheroid formation occurred during three weeks of culture in foams with or without RGD-alginate for NHIK 3025, SKOV-3, 3T3 and V79-379A indicating that these cell lines do not require the presence of RGD within the alginate matrix for cell growth. However, during the same period, cell proliferation was only seen in the foams containing RGD-alginate for OVCAR-3, MDCK and C2C12. The proliferation rate was affected by the RGD density. Cells that did not proliferate in pure alginate were still metabolically viable as shown by live-dead staining. This cell culture model enables 3D cell culture, formation of spheroids and isolation of intact cellular structures. Cell-matrix interaction can be controlled by type and concentration of signaling molecules covalently attached to the alginate immobilization solution making NovaMatrix®-3D a versatile cell culture system. Portions of this work have been funded with the support from METOXIA project no.222741 under the 7th Research Framework Programme of the European Union. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5269. doi:1538-7445.AM2012-5269

Analytical forms for most likely matrices derived from incomplete information

Consider a rectangular matrix describing some type of communication or transportation between a set of origins and a set of destinations, or a classification of objects by two attributes. The problem is to infer the entries of the matrix from limited information in the form of constraints, generally the sums of the elements over various subsets of the matrix, such as rows, columns, etc., or from bounds on these sums, down to individual elements. Such problems are routinely addressed by applying the maximum entropy method to compute the matrix numerically, but in this article we derive analytical, closed-form solutions. For the most complicated cases we consider the solution depends on the root of a non-linear equation, for which we provide an analytical approximation in the form of a power series. Some of our solutions extend to 3-dimensional matrices. Besides being valid for matrices of arbitrary size, the analytical solutions exhibit many of the appealing properties of maximum entropy, such as precise use of the available data, intuitive behaviour with respect to changes in the constraints, and logical consistency.

Kronecker products and the RSK correspondence

A matrix M with nonnegative integer entries is minimal if the nonincreasing sequence of its entries (called π-sequence) is minimal, in the dominance order of partitions, among all nonincreasing sequences of entries of matrices with nonnegative integers that have the same 1-marginals as A.The starting point for this work is an identity that relates the number of minimal matrices that have fixed 1-marginals and π-sequence to a linear combination of Kronecker coefficients. In this paper we provide a bijection that realizes combinatorially this identity. From this bijection we obtain an algorithm that to each minimal matrix associates a minimal component, with respect to the dominance order, in a Kronecker product, and a combinatorial description of the corresponding Kronecker coefficient in terms of minimal matrices and tableau insertion. Our bijection follows from a generalization of the dual RSK correspondence to 3-dimensional binary matrices, which we state and prove. With the same tools we also obtain a generalization of the RSK correspondence to 3-dimensional integer matrices.

Research on stem cells as candidates to be differentiated into hepatocytes

Liver diseases have become one of the most important causes of morbidity and mortality in the world. Cell therapy and liver transplantation are though to be two treatment options well accepted. However, the shortage of cells sources in cytotherapy and the lack of liver donor in liver transplantation are the major obstacles for the performance of these treatment methods. It urged us to find new origins of extra-hepatic cells. A number of recent studies show that extra-hepatic mesenchymal stem cells (MSC) from different tissues can be differentiated into hepatocytes like cells (HLC). Several hepatic differentiation protocols of MSC have been published in recent years, based on cellular stimulation with exogenous cytokines/growth factors, co-culture with fetal or adult hepatocytes, 2- or 3-dimensional (2D, 3D) matrices to favor differentiation. Independently from the starting stem cells population used, some minimal criteria must be fulfilled to ensure therapeutic success: in vitro expandability, expression of hepatic like surface markers, with hepatic cell functions, and minimal or absent immunogenicity in the recipient host. In this review, we focused on stem cells originated from bone marrow, umbilical cord and adipose tissue which are widely investigated in recent years and have been proved to have liver regenerative potential, the factors used to differentiate stem cells to hepatocyte-like cells and the methods used to investigate these cells.

Hyphal Growth in Human Fungal Pathogens and Its Role in Virulence

Most of the fungal species that infect humans can grow in more than one morphological form but only a subset of pathogens produce filamentous hyphae during the infection process. This subset is phylogenetically unrelated and includes the commonly carried yeasts, Candida albicans, C. dubliniensis, and Malassezia spp., and the acquired pathogens, Aspergillus fumigatus and dermatophytes such as Trichophyton rubrum and T. mentagrophytes. The primary function of hypha formation in these opportunistic pathogens is to invade the substrate they are adhered to, whether biotic or abiotic, but other functions include the directional translocation between host environments, consolidation of the colony, nutrient acquisition and the formation of 3-dimensional matrices. To support these functions, polarised hyphal growth is co-regulated with other factors that are essential for normal hypha function in vivo.

Conducting polymers with immobilised fibrillar collagen for enhanced neural interfacing

Conducting polymers with pendant functionality are advantageous in various bionic and organic bioelectronic applications, as they allow facile incorporation of bio-regulative cues to provide bio-mimicry and conductive environments for cell growth, differentiation and function. In this work, polypyrrole substrates doped with chondroitin sulfate (CS), an extracellular matrix molecule bearing carboxylic acid moieties, were electrochemically synthesized and conjugated with type I collagen. During the coupling process, the conjugated collagen formed a 3-dimensional fibrillar matrix in situ at the conducting polymer interface, as evidenced by atomic force microscopy (AFM) and fluorescence microscopy under aqueous physiological conditions. Cyclic voltammetry (CV) and impedance measurement confirmed no significant reduction in the electroactivity of the fibrillar collagen-modified conducting polymer substrates. Rat pheochromocytoma (nerve) cells showed increased differentiation and neurite outgrowth on the fibrillar collagen, which was further enhanced through electrical stimulation of the underlying conducting polymer substrate. Our study demonstrates that the direct coupling of ECM components such as collagen, followed by their further self-assembly into 3-dimensional matrices, has the potential to improve the neural-electrode interface of implant electrodes by encouraging nerve cell attachment and differentiation.

Abstract 4278: Spheroid growth in 3D alginate matrices

Abstract The use of 3-dimensional (3D) matrices for cell culture is gaining popularity as a substitute for traditional 2D cell culture as it can approximate cell architecture and cell-cell contact found in tissues, organs and tumors. NovaMatrix-3D™ is an alginate-based cell culture system comprising an alginate foam matrix and an alginate immobilizing solution. In principle, cells are first suspended in a sodium alginate solution then the cell suspension is applied to the alginate foam. In situ gelation occurs when calcium ions are donated from the foam cross-linking the added alginate, effectively entrapping the cells within the pores throughout the foam. To show the utility of the NovaMatrix-3D™ culture system, various cell lines were first cultured in 2D then prepared as a suspension in 0.5 – 1% sodium alginate in cell culture medium. An aliquot of each cell suspension was added to γ-sterilized NovaMatrix-3DTM foams (12- or 24-well plate size). NHIK 3025 (cervix carcinoma), MCF7 (breast adenocarcinoma), ZR-75-1 (breast ductal carcinoma) and NIH:OVCAR-3 (ovarian adenocarcinoma) were used and single cells were immobilized in the alginate foams. Cell localization within the foam was visualized using confocal microscopy to identify fluorescently labeled (CellTrace™ CFSE) cells. Cell proliferation was measured by counting cells after de-gelling the foam using sodium citrate. In each case, cells were immobilized with or without RDG-coupled alginate to investigate the importance of the presence of cell attachment peptides within the alginate. For these cell lines, cell growth and multicellular spheroid formation was independent of the presence of RGD. Spheroids could also be removed intact by de-gelling the alginate matrix and further processed for histological staining. One example shows the selective staining of apoptotic cells within the spheroid. Use of alginate foams with concomitant in situ immobilization of cells results in a 3D cell culture model with the potential to approximate cell proliferation and architecture within tissues or tumors. The technology enables biomimetic approaches by varying e.g. matrix elasticity, gelling ions, attachment peptides and foam degradation making NovaMatrix-3D™ a versatile cell culture system. Portions of this work have been funded with the support from METOXIA project no.222741 under the 7th Research Framework Programme of the European Union. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4278. doi:10.1158/1538-7445.AM2011-4278

VEGF and FGF prime vascular tube morphogenesis and sprouting directed by hematopoietic stem cell cytokines

AbstractHere, we demonstrate a novel, direct-acting, and synergistic role for 3 hematopoietic stem cell cytokines: stem cell factor, interleukin-3, and stromal derived factor-1α, in controlling human endothelial cell (EC) tube morphogenesis, sprouting, and pericyte-induced tube maturation under defined serum-free conditions in 3-dimensional matrices. Angiogenic cytokines such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) alone or VEGF/FGF combinations do not support these responses. In contrast, VEGF and FGF prime EC responses to hematopoietic cytokines via up-regulation of c-Kit, IL-3Rα, and C-X-C chemokine receptor type 4 from either human ECs or embryonic quail vessel explants. In support of these findings, EC Runx1 is demonstrated to be critical in coordinating vascular morphogenic responses by controlling hematopoietic cytokine receptor expression. Combined blockade of hematopoietic cytokines or their receptors in vivo leads to blockade of developmental vascularization in quail embryos manifested by vascular hemorrhage and disrupted vascular remodeling events in multiple tissue beds. This work demonstrates a unique role for hematopoietic stem cell cytokines in vascular tube morphogenesis and sprouting and further demonstrates a novel upstream priming role for VEGF and FGF to facilitate the action of promorphogenic hematopoietic cytokines.

The Promise and Therapeutic Potential of Human ES and iPS Cells

The Promise and Therapeutic Potential of Human ES and iPS Cells

Endothelial-derived PDGF-BB and HB-EGF coordinately regulate pericyte recruitment during vasculogenic tube assembly and stabilization

Recently, we reported a novel system whereby human pericytes are recruited to endothelial cell (EC)-lined tubes in 3-dimensional (3D) extracellular matrices to stimulate vascular maturation including basement membrane matrix assembly. Through the use of this serum-free, defined system, we demonstrate that pericyte motility within 3D collagen matrices is dependent on the copresence of ECs. Using either soluble receptor traps consisting of the extracellular ligand-binding domains of platelet-derived growth factor receptor β, epidermal growth factor receptor (EGFR), and ErbB4 receptors or blocking antibodies directed to platelet-derived growth factor (PDGF)-BB, or heparin-binding EGF-like growth factor (HB-EGF), we show that both of these EC-derived ligands are required to control pericyte motility, proliferation, and recruitment along the EC tube ablumenal surface. Blockade of pericyte recruitment causes a lack of basement membrane matrix deposition and, concomitantly, increased vessel widths. Combined inhibition of PDGF-BB and HB-EGF-induced signaling in quail embryos leads to reduced pericyte recruitment to EC tubes, decreased basement membrane matrix deposition, increased vessel widths, and vascular hemorrhage phenotypes in vivo, in support of our findings in vitro. In conclusion, we report a dual role for EC-derived PDGF-BB and HB-EGF in controlling pericyte recruitment to EC-lined tubes during developmental vascularization events.

An Automated High-Content Assay for Tumor Cell Migration through 3-Dimensional Matrices

High-content tumor cell migration assays in 3-dimensional (3D) extracellular matrix are a powerful tool for modeling and understanding the biology of this critical step in the process of metastasis. Currently available methods offer very limited throughput and are not amenable to studies of comparative pharmacology or small-scale screening. The authors present an automated approach to high-content tumor cell migration assays. A standard screening-sized plate with an array of microchannels was designed and constructed from common thermoplastics. After filling the channels with 3D matrix, cells were placed at one end of the channel, and migration into the channel was monitored via an imaging system. All liquid-handling steps were performed by standard liquid-handling robotics. Tumor cell migration in the channel was truly 3D and correlated with metastatic potential. The information-rich data from these assays were used to rank the potency of compounds inhibiting migration through 3D collagen as well as to gain additional insights into the compounds' activities related to cell health. This approach is compatible with a variety of multiparametric, morphological, and/or kinetic readouts.

Hypoxia Enhances the Angiogenic Potential of Human Dental Pulp Cells

Introduction Trauma can result in the severing of the dental pulp vessels, leading to hypoxia and ultimately to pulp necrosis. Improved understanding of mechanisms underlying the response of dental pulp cells to hypoxic conditions might lead to better therapeutic alternatives for patients with dental trauma. The purpose of this study was to evaluate the effect of hypoxia on the angiogenic response mediated by human dental pulp stem cells (DPSCs) and human dental pulp fibroblasts (HDPFs). Methods DPSCs and HDPFs were exposed to experimental hypoxic conditions. Hypoxia-inducible transcription factor-1alpha (HIF-1alpha) was evaluated by Western blot and immunocytochemistry, whereas vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) expression was evaluated by enzyme-linked immunosorbent assay. YC-1, an inhibitor of HIF-1alpha, was used to evaluate the functional effect of this transcriptional factor on hypoxia-induced VEGF expression. Conditioned medium from hypoxic and normoxic pulp cells was used to stimulate human dermal microvascular endothelial cells (HDMECs). HDMEC proliferation was measured by WST-1 assay, and angiogenic potential was evaluated by a capillary sprouting assay in 3-dimensional collagen matrices. Results Hypoxia enhanced HIF-1alpha and VEGF expression in DPSCs and HDPFs. In contrast, hypoxia did not induce bFGF expression in pulp cells. YC-1 partially inhibited hypoxia-induced HIF-1alpha and VEGF in these cells. The growth factor milieu of hypoxic HDPFs (but not hypoxic DPSCs) induced endothelial cell proliferation and sprouting as compared with medium from normoxic cells. Conclusions Collectively, these data demonstrate that hypoxia induces complex and cell type–specific pro-angiogenic responses and suggest that VEGF (but not bFGF) participates in the revascularization of hypoxic dental pulps.

Role of sphingosine kinase‐1 in paracrine/transcellular angiogenesis and lymphangiogenesis in vitro

Sphingosine-1-phosphate (S1P) is an important bioactive sphingolipid involved in angiogenesis and lymphangiogenesis, 2 important processes that influence the growth, survival, and spread of tumors. S1P acts as an extracellular mediator through binding to 5 highly specific S1P receptors, S1P(1-5). Sphingosine kinase-1 (SK1), one of 2 known sphingosine kinase enzymes responsible for S1P production, appears to be overexpressed in many tumors. Although a role for S1P in angiogenesis and lymphangiogenesis has been established, it is unclear whether S1P secreted from cancer cells has a paracrine function in a tumor environment. Here we investigated whether modulation of cellular SK1 could initiate a paracrine angiogenic and lymphangiogenic switch. We found that SK1 overexpression in HEK cells or its down-regulation in glioma or breast cancer cells modulated extracellular S1P levels accordingly, which in turn increased or decreased both migration and tube formation in cocultured vascular or lymphatic endothelial cells. In contrast, down-regulation of sphingosine kinase 2 in both glioma and breast cancer cells had no appreciable effect on cellular or secreted S1P levels. In addition, vascular endothelial growth factors VEGF and VEGF-C down-regulation in cancer cells appeared insufficient to block the angiogenic and lymphangiogenic switch triggered by these cells. Moreover, S1P initiated endothelial cell sprouting in 3-dimensional collagen matrices, which is representative of a multistep angiogenic process. Our data collectively demonstrate for the first time that SK1 plays an essential role in regulating in vitro paracrine angiogenesis and lymphangiogenesis.

T-helper 2 cells are essential for modulation of vascular repair by allogeneic endothelial cells

Endothelial cells (ECs) embedded within 3-dimensional matrices (MEEC) control lumenal inflammation and intimal hyperplasia when placed in the vascular adventitia. Matrix embedding alters endothelial immunogenicity in vitro. T-helper (Th) cell-driven host immunity is an impediment of allogeneic grafts. We aimed to identify if modulation of Th balance would affect immune compatibility and endothelial regulation of vascular repair in vivo. Pigs (n = 4/group) underwent carotid artery balloon injury and were left untreated (Group 1) or received perivascular porcine MEEC implants (Group 2), 12 days of cyclosporine A (CsA; Group 3), or MEEC and CsA (Group 4). Host immune reactivity was analyzed after 28 and 90 days. MEEC treatment induced formation of EC-specific immunoglobulin (Ig) G(1) antibodies (41 +/- 6 mean fluorescence intensity [MFI]) and differentiation of host splenocytes into Th2, but not Th1, cytokine-producing cells (interleukin [IL]-4, 242 +/- 102; IL-10, 273 +/- 114 number of spots). Concomitant CsA therapy reduced IgG(1) antibody frequency (25 +/- 2 MFI; p < 0.02) and Th2-cytokine producing splenocytes upon MEEC treatment (IL-4, 157 +/- 19; IL-10, 124 +/- 26 number of spots; p < 0.05). MEECs inhibited luminal occlusion 28 and 90 days after balloon injury (12 +/- 7%) vs untreated controls (68 +/- 14%; p < 0.001) but to a lesser extent with concomitant CsA treatment (34 +/- 13%; p < 0.02 vs Group 2). MEECs do not induce a significant Th1-driven immune response but do enhance differentiation of splenocytes into cells producing Th2 cytokine. Reduction in this Th2 response reduces the vasoregulatory effects of allogeneic ECs after injury.

Deletion of the Met receptor in the collecting duct decreases renal repair following ureteral obstruction

Hepatocyte growth factor and its receptor, Met, activate biological pathways necessary for repair and regeneration following kidney injury. The Met receptor is expressed in multiple cell types within the kidney, each of which is capable of regulating fibrotic responses. To specifically address the role of the Met receptor in the adult collecting duct during renal injury, a conditional knockout mouse (Met(fl/fl);HoxB7-Cre) was generated and tested using unilateral ureteral obstruction, a model of nephron injury, fibrosis, and repair. Following obstruction in these mice there was increased expression of collagens I and IV along with plasminogen activator inhibitor 1, a known regulator of matrix degradation, compared to ureteral obstructed non-flox littermates. There were trends toward increased interstitial fibrosis, infiltration of the interstitium, and acute tubular necrosis in the knockout mice despite similar degrees of hydronephrosis to the control littermates. The Met(fl/fl);HoxB7-Cre mice; however, had reduced tubular cell proliferation and kidney regenerative capacity after release of the obstruction, thus leading to diminished functional recovery. We suggest that Met receptor signaling in the collecting duct acts as a major regulator of cell survival and propagation of the repair process with a possible secondary role to diminish inflammatory and fibrotic responses.

Endothelial cell lumen and vascular guidance tunnel formation requires MT1-MMP–dependent proteolysis in 3-dimensional collagen matrices

AbstractHere we show that endothelial cells (EC) require matrix type 1-metalloproteinase (MT1-MMP) for the formation of lumens and tube networks in 3-dimensional (3D) collagen matrices. A fundamental consequence of EC lumen formation is the generation of vascular guidance tunnels within collagen matrices through an MT1-MMP-dependent proteolytic process. Vascular guidance tunnels represent a conduit for EC motility within these spaces (a newly remodeled 2D matrix surface) to both assemble and remodel tube structures. Interestingly, it appears that twice as many tunnel spaces are created than are occupied by tube networks after several days of culture. After tunnel formation, these spaces represent a 2D migratory surface within 3D collagen matrices allowing for EC migration in an MMP-independent fashion. Blockade of EC lumenogenesis using inhibitors that interfere with the process (eg, integrin, MMP, PKC, Src) completely abrogates the formation of vascular guidance tunnels. Thus, the MT1-MMP-dependent proteolytic process that creates tunnel spaces is directly and functionally coupled to the signaling mechanisms required for EC lumen and tube network formation. In summary, a fundamental and previously unrecognized purpose of EC tube morphogenesis is to create networks of matrix conduits that are necessary for EC migration and tube remodeling events critical to blood vessel assembly.

Matrices of science and technology interactions and patterns of structured growth: implications for development

Scientific and other non-patent references (NPRs) in patents are important tools to analyze interactions between science and technology. This paper organizes a database with 514,894 USPTO patents granted globally in 1974, 1982, 1990, 1998 and 2006. There are 165,762 patents with at least one reference to science and engineering (S&E) literature, from a total of 1,375,503 references. Through a lexical analysis, 71.1% of this S&E literature is classified by S&E fields. These data serve as the basis for the elaboration of global and national 3-dimensional matrices (technological domains, S&E fields and number of references). Three indicators are proposed to analyze these matrices, allowing us to identify patterns of structured growth that differentiate developed and non-developed countries. This differentiation informs suggestions for public policies for development, emphasizing the need for an articulation between the industrial and technological dimension and scientific side. The intertwinement of these two dimensions is a key component of developmental policies for the twenty-first century.