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Laminins are a large family of conserved, multidomain trimeric basement membrane proteins that contribute to the structure of extracellular matrix and influence the behavior of associated cells, such as adhesion, differentiation, migration, phenotype stability, and resistance to anoikis. In lower organisms such as Hydra there is only one isoform of laminin, but higher organisms have at least 16 trimeric isoforms with varying degrees of cell/tissue specificity. In vitro protein and cell culture studies, gene manipulation in animals, and laminin gene mutations in human diseases have provided insight into the specific functions of some laminins, but the biological roles of many isoforms are still largely unexplored, mainly owing to difficulties in isolating them in pure form from tissues or cells. In this review, we elucidate the evolution of laminins, describe their molecular complexity, and explore the current knowledge of their diversity and functional aspects, including laminin-mediated signaling via membrane receptors, in vitro cell biology, and involvement in various tissues gained from animal model and human disease studies. The potential use of laminins in cell biology research and biotechnology is discussed. [ABSTRACT FROM AUTHOR]

The article provides information on the interaction between cells and the extracellular matrix. It is stated that according to researches these interactions are mediated by integrins and elastin receptors. It informs that connective tissue fibres play an important role in the migration of normal and malignant cells inside the body.

Abstract: During decades preceding and following the last war, a favourite subject of biochemists was to study glycoproteins. One class of these substances, found in connective tissues were characterised as polysaccharides, most of them found to be linked to proteins, designated later as glycosaminoglycans and proteoglycans. Another family of glycoconjugates represented epithelial mucins as found in the gastro-intestinal and respiratory tracts and conduits. A third family of glycoconjugates is represented by circulating glycoproteins isolated from the blood plasma, mostly studied by medical biochemists in relation to pathological conditions comprising those increasing during the inflammatory reaction: acute phase glycoproteins. Their study suggested that they might be derived from connective tissues. Although inflammatory glycoproteins derive mostly from the liver, the possibility of connective tissue origin of glycoproteins remained open. Using cornea, an avascular tissue, we could show that connective tissues also synthesize glycoproteins. We proposed to designate them “structural glycoproteins” (SGP-s) to distinguish them from circulating, blood-born glycoproteins coming from the liver. They play locally “structural” roles in connective tissues where they are synthesized. Soon after fibronectin was identified and shown to mediate cell-matrix interactions. A large family of glycoproteins were then isolated from a variety of sources, cells, tissues others than liver, confirming our original hypothesis. The first experiments on these glycoproteins were published from 1961/1962 giving the opportunity to recapitulate this biochemical adventure 50 years later, together with the celebration of the foundation of the first connective tissue society in Europe, as described in the first article in this issue. [Copyright &y& Elsevier]

The Tp63 gene encodes for multiple isoforms of the p63 transcription factor, a member of the p53 family of proteins. Much like its more famous sibling, the biological role of p63 is quite complex, with wide-ranging effects on development, differentiation, and cellular lineage choices. The crucial function of p63 is epitomized by the striking phenotype of p63 knockout mice. These animals have a profound block in the development of stratified epithelia and aplasia of multiple ectodermal appendages, as well as orofacial clefting and limb defects. Remarkably, a similar spectrum of phenotypic alterations is observed in human syndromes resulting from Tp63 gene mutations. p63 is an important hub in the transcriptional and signaling networks of epithelial cells; thus, it is not surprising that dysregulation of this transcription factor is associated with squamous cell carcinoma. Finally, as a testament to the growing repertoire of p63-associated diseases, autoantibodies to p63 are associated with chronic ulcerative stomatitis, an oral immunologically mediated disease. Over the past decade, our understanding of the broad biologic and pathophysiological roles of p63 has grown significantly. In this review, we discuss the molecular attributes of Tp63 and the clinical consequences of Tp63 dysregulation, particularly as it pertains to oral tissues. [ABSTRACT FROM PUBLISHER]

Adhesion of epithelium to the extracellular matrix is crucial for the maintenance of systemic and oral health. In the oral cavity, teeth or artificial dental implants penetrate the soft tissue of the gingiva. In this interface, gingival soft tissue needs to be well attached via the epithelial seal to the tooth or implant surface to maintain health. After injury or wounding, epithelial tissue rapidly migrates to form the initial epithelial cover to restore the barrier against infection. These events are crucially dependent on deposition of extracellular matrix and proper activation and function of integrin receptors in the epithelial cells. Recent experimental evidence suggests that epithelial integrins also participate in the regulation of periodontal inflammation. In this review, we will discuss the structure and function of epithelial integrins and their extracellular ligands and elaborate on their potential role in disease and repair processes in the oral cavity. [ABSTRACT FROM PUBLISHER]

Abstract: The discovery that adherent tissue cells actively sustain internal tension and exert mechanical forces on their surroundings has opened new vistas in the field of cell and tissue mechanics. Cellular forces, generated by acto-myosin contractility, play a central role in numerous aspects of cell behavior and function. Apart from the various specific functions that cells perform by applying forces (e.g., wound healing, remodeling of the extracellular matrix and muscle contraction), cells also apply stresses as a generic means for sensing and responding to the mechanical nature of their environment. In addition, the internal tension plays a role in actively controlling the elastic moduli and shape stability of the cell. In this review, we survey recent theoretical and experimental studies of the physical consequences of cell mechanical activity including its role in cell morphology, adhesion strength, stress-fiber polarization, and the elastic properties of cells. We also discuss the role of cell mechanics in orienting cellular assemblies and in the response of cells to external loads. [Copyright &y& Elsevier]

The anti-cancer drug, emodin, can cause significant mechanobiological changes in human cancer cells, due to the interplay of anti-cell adhesion, actin-disrupting and apoptosis-causing effects of the drug. Here, we used micropillars to monitor the changes in traction forces induced by breast cancer cells in response to this drug stimulus. Our results showed that the variations in the cell traction forces reflected changes in the cytoskeleton integrity and cell behavior. Cell traction forces were found to increase during cell rounding and decrease during the onset of apoptosis and cytoskeleton disruption. These results can provide useful insights into the chemo-mechanical relationships arising from the cell-matrix interactions and can potentially help in the quantitative assessment of drug efficacy. [ABSTRACT FROM AUTHOR]

Salivary glands form during embryonic development by a complex process that creates compact, highly organized secretory organs with functions essential for oral health. The architecture of these glands is generated by branching morphogenesis, revealed by recent research to involve unexpectedly dynamic cell motility and novel regulatory pathways. Numerous growth factors, extracellular matrix molecules, gene regulatory pathways, and mechanical forces contribute to salivary gland morphogenesis, but local gene regulation and morphological changes appear to play particularly notable roles. Here we review these recent advances and their potential application to salivary gland tissue engineering. [ABSTRACT FROM PUBLISHER]

Podocytes adhere to the glomerular basement membrane by cell surface receptors. Since in other cells these adhesions are enhanced by cell surface proteoglycans, we examined the contribution of these molecules and their glycosaminoglycan side chains to podocyte adhesion by developing immortalized podocyte cell lines with (control) or without (mutant) heparan sulfate glycosaminoglycan chains. In adhesion assays control podocytes attached, spread, and migrated more efficiently compared with mutants, indicating a requirement for heparan sulfate chains in these processes. The proteoglycan syndecan-4 is known to have direct effects on cell attachment, spreading, and cytoskeletal organization. We found it localized to focal adhesions in control podocytes coincident with stress fiber formation. In mutant cells, syndecan-4 was associated with smaller focal contacts and cortical actin organization. Analysis by flow cytometry showed that mutant cells had twice the amount of surface syndecan-4 of control cells. Protein kinase Cα, a signaling molecule bound to and activated by syndecan-4, showed a fourfold increase in membrane localization-activation than that seen in control cells. In vivo, the loss of heparan sulfate glycosaminoglycans in PEXTKO mice led to a loss of glomerular syndecan-4. Overall, our study provides further evidence for a dynamic role of cell surface heparan sulfate glycosaminoglycans in podocyte activity. [ABSTRACT FROM AUTHOR]

Connective tissue growth factor (CCN2/CTGF) is not normally expressed in gingival fibroblasts, but is induced by the potent profibrotic cytokine TGFβ and is overexpressed in gingival fibrosis. Since CCN2 is a marker and mediator of fibrosis, targeting CCN2 expression in gingival fibroblasts may provide new insights into the future development of novel therapeutic opportunities to treat oral fibrosis. Herein we used real-time polymerase chain-reaction, Western blot, and indirect immunofluorescence analysis to evaluate whether SB-431542, a specific pharmacological inhibitor of TGFβ type I receptor (ALK5), blocks the ability of TGFβ to induce CCN2 mRNA and protein expression in human gingival fibroblasts. Our results indicate that CCN2 mRNA and protein are induced by TGFβ in gingival fibroblasts in a SB-431542-sensitive fashion. These results suggest that blocking ALK5 may be useful in blocking the profibrotic effects of TGFβ in gingival fibroblasts. [ABSTRACT FROM PUBLISHER]

Abstract: The effect of different collagen and cell concentrations on the mechanical and remodeling behaviors of corneal stroma wound healing models consisting of collagen hydrogels seeded with human corneal fibroblasts during a 25 day culture period were examined. Human corneal fibroblasts were seeded at 1 × 105, 3 × 105 or 5 × 105 cells per hydrogel, and collagen concentrations of 2.5 mg/ml, 3.5 mg/ml or 4.5 mg/ml were examined. Two non-destructive techniques, spherical indentation and optical coherence tomography, were used to measure the elastic modulus and dimensional changes respectively at several time-points over the culture period. The elastic modulus of the hydrogels increased continuously over 25 days. Hydrogels with higher initial cell seeding densities and lower initial collagen concentrations were found to increase in elastic modulus faster and possessed a higher elastic modulus by the end of the culture period when compared to the other hydrogels. A mathematical equation was applied to accurately fit the change in elastic modulus over time. This study demonstrates a robust in vitro technique able to monitor the effect of different parameters on the cell–matrix mechanical relationship in a corneal stroma model during prolonged culture periods and enhances our understanding on corneal wound healing processes. [ABSTRACT FROM AUTHOR]

Adhesion of mammalian cells to in vitro surfaces is an area of active research and it attracts considerable interest from various scientific disciplines, most notably from medical technology and biotechnology. One important issue in the context of cell-surface adhesion is the time course of attachment and spreading upon surfaces that are decorated with proteins to make them cytocompatible. This article reviews two emerging non-microscopic techniques capable of monitoring the adhesion process label-free and in real-time. Both approaches, electric cell-substrate impedance sensing (ECIS) and the quartz crystal microbalance (QCM), are based on substrate-integrated transducers that transduce cellular adhesion into an electrical signal. A short introduction of both techniques is followed by a set of examples that illustrate the performance of these sensors, their individual merits and limitations. In order to analyze the integral and complex signals of both sensors in contact with mammalian cells in more detail, we also studied their individual readouts during the adsorption of liposomes with well-defined structure and chemical composition. [ABSTRACT FROM AUTHOR]

Glomerulosclerosis is characterized by the loss of glomerular cells by apoptosis and deposition of collagen type I into the normal collagen IV-containing mesangial matrix. We sought to determine the alterations that might contribute to these changes by performing proteomic analysis of rat mesangial cell lysates comparing cells cultured on normal collagen type IV to those grown on abnormal collagen type I surfaces. Subculture on collagen type I was associated with changed expression of several proteins, including a significant upregulation of the paxillin-like LIM protein, hydrogen-peroxide-induced clone 5 (Hic-5), and increased the susceptibility of the cells to apoptosis in response to physiological triggers. When we knocked down Hic-5 (using siRNA), we found mesangial cells grown on collagen type I were protected from apoptosis to the same degree as untreated cells grown on collagen type IV. Further we found that the level of Hic-5 in vivo was almost undetectable in control rats but increased dramatically in the glomerular mesangium of remnant kidneys 90 and 120 days after subtotal nephrectomy. This induction of Hic-5 paralleled the upregulation of mesangial collagen type I expression and glomerular cell apoptosis. Our results suggest that Hic-5 is pivotal in mediating the response of mesangial cells to attachment on abnormal extracellular matrix during glomerular scarring. [ABSTRACT FROM AUTHOR]

Abstract: Prenatal inflammation prevents normal lung morphogenesis and leads to bronchopulmonary dysplasia (BPD), a common complication of preterm birth. We previously demonstrated in a bacterial endotoxin mouse model of BPD that disrupting fibronectin localization in the fetal lung mesenchyme causes arrested saccular airway branching. In this study we show that expression of the fibronectin receptor, integrin α8β1 is decreased in the lung mesenchyme in the same inflammation model suggesting it is required for normal lung development. We verified a role for integrin α8β1 in lung development using integrin α8-null mice, which develop fusion of the medial and caudal lobes as well as abnormalities in airway division. We further show in vivo and in vitro that α8-null fetal lung mesenchymal cells fail to form stable adhesions and have increased migration. Thus we propose that integrin α8β1 plays a critical role in lung morphogenesis by regulating mesenchymal cell adhesion and migration. Furthermore, our data suggest that disruption of the interactions between extracellular matrix and integrin α8β1 may contribute to the pathogenesis of BPD. [Copyright &y& Elsevier]

Abstract: The pericellular matrix (PCM) surrounding chondrocytes is thought to play an important role in transmitting biochemical and biomechanical signals to the cells, which regulates many cellular functions including tissue homeostasis. To better understand chondrocytes interactions with their PCM, three-dimensional poly(ethylene glycol) (PEG) hydrogels containing Arg–Gly–Asp (RGD), the cell-adhesion sequence found in fibronectin and which is present in the PCM of cartilage, were employed. RGD was incorporated into PEG hydrogels via tethers at 0.1, 0.4 and 0.8mM concentrations. Bovine chondrocytes were encapsulated in the hydrogels and subjected to dynamic compressive strains (0.3Hz, 18% amplitude strain) for 48h, and their response assessed by cell morphology, ECM gene expression, cell proliferation and matrix synthesis. Incorporation of RGD did not influence cell morphology under free swelling conditions. However, the level of cell deformation upon an applied strain was greater in the presence of RGD. In the absence of dynamic loading, RGD appears to have a negative effect on chondrocyte phenotype, as seen by a 4.7-fold decrease in collagen II/collagen I expressions in 0.8mM RGD constructs. However, RGD had little effect on early responses of chondrocytes (i.e. cell proliferation and matrix synthesis/deposition). When isolating RGD as a biomechanical cue, cellular response was very different. Chondrocyte phenotype (collagen II/collagen I ratio) and proteoglycan synthesis were enhanced with higher concentrations of RGD. Overall, our findings demonstrate that RGD ligands enhance cartilage-specific gene expression and matrix synthesis, but only when mechanically stimulated, suggesting that cell–matrix interactions mediate chondrocyte response to mechanical stimulation. [Copyright &y& Elsevier]

Abstract: The extracellular matrix is an insoluble aggregate of large proteins and glycosoaminoglycans that comprises the microenvironment of cells in tissue. The matrix displays a host of ligands that interact with cell-surface receptors to mediate the attachment and spreading of cells and regulate signaling processes. Studies of cell–matrix interactions and downstream signaling processes commonly employ substrates having an adsorbed layer of protein and are challenged by the difficulty in controlling the structure and activity of the immobilized protein. Significant effort has been directed towards the development of model substrates that present adhesion ligands in defined densities, orientations and environments. Among these approaches, self-assembled monolayers of alkanethiolates on gold offer a high level of control over the molecular structure of the surface and are well-suited to studies of cell adhesion. This review describes the design and use of monolayers for applications in cell biology, including the use of monolayers to evaluate the roles of peptide and protein ligands in cell–matrix interactions, the development of methods to pattern ligands on monolayers and applications to cell biology, the development of dynamic monolayers that can switch the activities of ligands presented to an adherent cell, and the rewiring of interactions between a cell and its substrate. These examples illustrate the flexibility inherent to monolayers for applications in cell biology. [Copyright &y& Elsevier]

Abstract: The individual and synergistic effects of extracellular matrix interactions on isolated islet function in culture were investigated within a three-dimensional poly(ethylene glycol) (PEG) hydrogel encapsulation environment. First, we observed similar glucose-stimulated insulin secretion from unencapsulated murine islets and islets photoencapsulated in PEG gels. Then islets were encapsulated in gels containing the basement membrane proteins collagen type IV and laminin, individually and in combination, at a total protein concentration of 100μg/ml, and islet insulin secretion in response to high glucose was measured over time. Specific laminin interactions were investigated via islet encapsulation with adhesive peptide sequences found in laminin as well as via functional blocking of cell surface receptors known to bind laminin. Over 32days, islet interactions with collagen type IV and laminin localized within the three-dimensional extracellular environment contributed to two-fold and four-fold increases in insulin secretion, respectively, relative to islets encapsulated without matrix proteins. Hydrogel compositions containing both matrix proteins and > 75% laminin further increased islet insulin secretion to approximately six-fold that of islets encapsulated in the absence of matrix proteins. Encapsulation with the peptide sequence IKVAV resulted in increased islet insulin secretion, but not to the extent observed in the presence of whole laminin. Increased insulin secretion in the presence of laminin was eliminated when islets were exposed to functionally blocking anti-α6 integrin antibody prior to islet encapsulation with laminin. Our results demonstrate the potential of specific matrix interactions within an islet encapsulation microenvironment to promote encapsulated islet function. [Copyright &y& Elsevier]

Cell-cell and cell-matrix interactions are of utmost importance in the pathogenesis of inflammatory diseases. For example, cell-cell and cell-matrix interactions are crucial for leukocyte homing and recruitment to inflammatory sites. The discovery of the disintegrin and metalloprotease (ADAM) proteins, which have both adhesive and proteolytic activities, raised the question of their involvement in inflammatory processes. More interestingly, the presence of the RGD integrin-binding sequence in the disintegrin domain of ADAM-15 (MDC-15; metar-Odin) highlighted ADAM-15 as a protein particularly involved in cell-cell interactions. These findings therefore prompted authors to investigate the roles of ADAM-15 in inflammatory diseases. Because of the early description of ADAM-15 expression in endothelial cells, work first focused on the roles of ADAM-15 in vascular diseases, and ADAM-15 was found to be associated with atherosclerosis. Other studies also pointed at ADAM-15 as a mediator of rheumatoid arthritis and intestinal inflammation as well as inherent angiogenesis. The roles of ADAM-15 in these diseases appear to involve mechanisms as different as cell-cell interactions, cell-extracellular matrix (ECM) interactions, and shedding activity. Here we review and discuss these recent discoveries pointing to ADAM-15 as a mediator of mechanisms underlying inflammation and as a possible therapeutic target for prevention of inflammatory diseases. [ABSTRACT FROM AUTHOR]

Background/Aims: α8β1-Integrin is expressed in mesangial cells. In vitro studies suggest a role for α8-integrin in the regulation of cell proliferation and apoptosis. We tested the hypothesis that α8-integrin is essential for the healing process after mesangioproliferative glomerulonephritis. Methods: Mice homozygous for a deletion of the α8-integrin chain were compared with wild-type mice. To study glomerular healing, we used the habu toxin model of reversible mesangioproliferative glomerulonephritis. Animals received 6 mg/kg habu toxin intravenously; controls received saline only. Results: Early mesangiolysis occurred in wild-type and α8-integrin-deficient mice. However, mesangiolysis was no longer detectable after 7 days in wild types but persisted after 14 days in α8-integrin-deficient animals. Mesangial activation marker α-smooth muscle actin was detectable only at day 7 in wild-type mice but persisted until day 14 in α8-integrin-deficient mice. In wild types, glomerular cell proliferation and apoptosis peaked at day 7 and decreased thereafter but remained elevated in α8-integrin-deficient mice until day 28. In cultivated mesangial cells, α8-integrin expression was associated with increased cell survival. Conclusion: Interactions between α8-integrin and the mesangial matrix may contribute to healing of glomerular injury by influencing cell proliferation and apoptosis. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background/Aims: Because various regions of the mitral valve contain distinctive extracellular matrix enabling the tissues to withstand diverse mechanical environments, we investigated phenotype and matrix production of porcine valvular interstitial cells (VICs) from different regions. Methods: VICswere isolated from the chordae (MCh), the center of the anterior leaflet (AlCtr), and the posterior leaflet free edge (PlFree), then assayed for metabolic, growth, and adhesion rates; collagen and glycosaminoglycan (GAG) production, and phenotype using biochemical assays, flow cytometry, and immunocytochemistry. Results: The AlCtr VICs exhibited the fastest metabolism but slowest growth. PlFree cells grew the fastest, but demonstrated the least smooth muscle α-actin, vimentin, and internal complexity. AlCtr VICs secreted less collagen into the culture medium but more 4-sulfated GAGs than other cells. Adhesion-based separation resulted in altered secretion of sulfated GAGs by MCh and AlCtr cells but not by the PlFree cells. Conclusions: VICs isolated from various regions of the mitral valve demonstrate phenotypic differences in culture, corresponding to the ability of the mitral valve to accommodate the physical stresses or altered hemodynamics that occur with injury or disease. Further understanding of VIC and valve mechanobiology could lead to novel medical or tissue engineering approaches to treat valve diseases. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Cell migration is a process that plays an important role throughout the entire life span. It starts early on during embryogenesis and contributes to shaping our body. Migrating cells are involved in maintaining the integrity of our body, for instance, by defending it against invading pathogens. On the other side, migration of tumor cells may have lethal consequences when tumors spread metastatically. Thus, there is a strong interest in unraveling the cellular mechanisms underlying cell migration. The purpose of this review is to illustrate the functional importance of ion and water channels as part of the cellular migration machinery. Ion and water flow is required for optimal migration, and the inhibition or genetic ablation of channels leads to a marked impairment of migration. We briefly touch cytoskeletal mechanisms of migration as well as cell–matrix interactions. We then present some general principles by which channels can affect cell migration before we discuss each channel group separately. [ABSTRACT FROM AUTHOR]

The development and complete differentiation of salivary glands is a complex process that involves a large number of co-ordinated events. Little is known about the molecular basis for salivary gland development. However, we have reported previously that integrins appear to play a role. Integrins are heterodimeric transmembrane receptors consisting of one α and one β subunit that play a pivotal role in the interaction of cells with the extracellular matrix. Such interactions regulate the organisation of cells of tissues and organs during development as well as cell proliferation and differentiation. Using immunohistochemistry and Western and Northern blot analysis, we mapped the localisation and expression of integrins β1, β3 and β4 in human salivary glands obtained from foetuses ranging from weeks 4–24 of gestation and compared it with adult salivary glands. Integrin β1 first appeared during the canalisation stage and during the differentiation stage. A message first appeared at week 6 of development. The expression of β4 integrin protein and message was observed only in the late stage of differentiation. Integrin β3 was not detected in the developing glands; however, integrins β1, β3 and β4 were all expressed in adult salivary gland tissues. The data suggest that integrins, particularly β1, have a role to play in salivary gland development and differentiation. [ABSTRACT FROM AUTHOR]

Although best known for its role in cholinergic signalling, a substantial body of evidence suggests that acetylcholinesterase (AChE) has multiple biological functions. Previously, we and others identified AChE expression in areas of bone that lacked expression of other neuronal proteins. More specifically, we identified AChE expression at sites of new bone formation suggesting a role for AChE as a bone matrix protein. We have now characterised AChE expression, secretion and adhesive function in osteoblasts. Using Western blot analysis, we identified expression of two AChE species in osteoblastic cells, a major species of 68 kDa and less abundant species of approximately 55 kDa. AChE colocalised with the Golgi apparatus in osteoblastic cells and was identified in osteoblast-conditioned medium. Further analyses revealed differentiation-dependent secretion by osteoblasts, with AChE secretion levels corresponding with alkaline phosphatase activity. AChE expression by osteoblastic cells was also found to be regulated by mechanical strain both in vitro and in vivo. Finally, we investigated the possibility of a functional role for AChE in osteoblast adhesion. Using specific inhibitors, blockade of sites thought to be responsible for AChE adhesive properties caused a concentration-dependent decrease in osteoblastic cell adhesion, suggesting that AChE is involved in regulating cell–matrix interactions in bone. [Copyright &y& Elsevier]

In this study the anti-angiogenic action of a novel non-peptide RGDS-analog named RAM was tested in vitro and in vivo. RAM inhibited FGF-2-induced chemotaxis by 80% in an adhesion-independent way. Further, it induced HUVEC-apoptosis in collagen-seeded HUVEC, indicating that such pro-apoptotic effect was adhesion-independent. In vivo studies revealed that RAM inhibited FGF-2 induced angiogenesis by 60% in the mouse Matrigel-assay and in the chicken-egg chorion-allantoic membrane assay. Finally, RAM was markedly more stable in serum as compared to the template RGDS and after 24h incubation in 100% serum was significantly more active than RGDS. Taken together these results show that RAM exerts anti-chemotactic and pro-apoptotic effects, by an unexpected adhesion-independent mechanism, as we have recently shown for the template RGDS molecule [Blood 103 (2004) 4180], and has in vivo relevant anti-angiogenic properties, with marked stability in serum; therefore, RAM represents a novel promising anti-angiogenic molecule. [Copyright &y& Elsevier]

Thrombospondins (TSPs) 1 and 2 are extracellular modular glycoproteins that are best known for their anti-angiogenic properties and their ability to modulate cell–matrix interactions. However, these proteins, and in particular TSP2, are pleiotropic in function and affect processes as disparate as bone growth and hemostasis. In recognition of their ability to influence a wide variety of cell functions, and in the absence of convincing evidence for their participation as integral components of extracellular structures, the term ‘matricellular’ has been applied to these and a small group of functionally related proteins. In this review, we focus on the role of TSP1 and 2 in two forms of injury in mice, excisional skin wounds and subcutaneously implanted biomaterials, and take advantage of mice with targeted disruptions of one or both genes to identify likely biochemical mechanisms that could account for the characteristics of the injury response in these knockout mice. In work that stems largely from our own laboratory, we show that pericellular levels of the matrix metalloproteinase, MMP2, are controlled to a large extent by TSP2 (and potentially also by TSP1), and that elevated levels of MMP2 are likely to account in part for defects as diverse as reduced cellular adhesion, abnormal collagen fibril structure, and increased endothelial cell and vascular proliferation. [Copyright &y& Elsevier]

Cell-matrix interactions are thought to influence epithelial structure, growth, and differentiation. Three-dimensional cell cultures were used to study the effects of the composition of the dermal equivalent on the morphology of epithelium grown from HaCaT skin keratinocytes. Three commercial preparations, a basement membrane preparation from a tumor (matrix 1), two preparations consisting of collagen type I and III (matrix 3 and 4) and a noncommercial preparation containing collagen type I (matrix 2) were investigated. The effects of fibroblasts of different origin (vaginal mucosa, oral buccal mucosa, and skin) were investigated in connection with matrix 4. The histomorphology and expression of the proteins PCNA, Ki-67, p53, p21, pankeratin, involucrin, cytokeratin 10 (Ck10), Ck17, Ck19 and collagen type IV were evaluated. Three-dimensional cultures of HaCaT cells gave rise to an epithelium with an immature and hyperproliferative character, showing active proliferation with intense PCNA staining. Both matrix 1 and matrix 2 resulted in an epithelium with budding into the matrix and some degree of layering. These epithelia showed only scattered Ck17 and Ck19 expression but a low terminal differentiation potential as indicated by scattered Ck10 and involucrin staining. The epithelia of cocultures with matrices 3 and 4 were positive for Ck17 and Ck19. However, the epithelium on matrix 3 showed strong expression of the terminal differentiation marker Ck10 and involucrin. This methodological study provides evidence of the importance of standardization of the composition of the matrix to avoid confounding effects on epithelial morphology and protein expression in studies using a three-dimensional epithelial culture model. [ABSTRACT FROM AUTHOR]

The extracellular matrix (ECM) is produced by the cells and secreted into the surrounding medium, and consists of a complex mixture of structural and functional proteins. It has been recently observed that the ECM can influence the behavior of cell growth in vitro quite remarkably. A simple mathematical model has been constructed based on negative feedback control mechanisms to represent the dynamics of ECM deposition and cellular differentiation. The model analysis shows a strong relationship between the numerical solution and the experimental observations in cell-polymer constructs for the design of engineered cartilage. The current paper may be a useful guide for those who want to explore the studies on cell-matrix interactions. [ABSTRACT FROM PUBLISHER]

The terminal differentiation of odontoblasts is controlled by the inner dental epithelium (IDE) and occurs according to a tooth-specific pattern. It requires temporospatially regulated epigenetic signaling and the expression of specific competence. The patterning of cusp formation was compared with that of odontoblast differentiation in the first lower molar in mice. Histology, immunostaining, and three dimensional reconstructions were completed by experimental approaches in vitro. The mesenchyme controls the pattern of cusp formation. During the cap-bell transition in the molar, a subpopulation of nondividing IDE cells from the enamel knot (EK) undergo a tooth-specific segregation in as many subpopulations as cusps will form. Epithelial cell-basement membrane interactions seem to be involved in the segregation of EK cells. The timing and spatial pattern of the segregation of EK cells correlate with cusps formation. However, the temporal pattern of odontoblast terminal differentiation is different. This discrepancy might result from cusp-specific differences either in the timing of the initiation of odontoblast terminal differentiation and/or in cell proliferation kinetics. [ABSTRACT FROM AUTHOR]

Relationships between cell-cell/cell-matrix interactions and enamel organ histomorphogenesis were examined by immunostaining and electron microscopy. During the cap-bell transition in the mouse molar, laminin-5 (LN5) disappeared from the basement membrane (BM) associated with the inner dental epithelium (IDE), and nondividing IDE cells from the enamel knot (EK) underwent a tooth-specific segregation in as many subpopulations as cusps develop. In the incisor, the basement membrane (BM) in contact with EK cells showed strong staining for LN5 and integrin α6β4. LN5 seems to provide stable adhesion, while its proteolytic processing might facilitate cell segregation. In both teeth, immunostaining for antigens associated with desmosomes or adherens junctions was similar for EK cells and neighboring IDE cells. Outside the EK, IDE cell-BM interactions changed locally during the initial molar cusp delimitation and on the labial part of the incisor cervical loop. Conversely, cell-cell junctions stabilized the anterior part of the incisor during completion of morphogenesis. Time and space regulation of cell-matrix and cell-cell interactions might thus play complementary roles in allowing plasticity during tooth morphogenesis and stabilization at later stages of epithelial histogenesis. [ABSTRACT FROM AUTHOR]

Close regulation of odontoblast differentiation and subsequent secretory activity is critical for dentinogenesis during both embryogenesis and tissue repair. Some dental papilla cells achieve commitment and specific competence, allowing them to respond to epithelially derived inductive signals during the process of odontoblast differentiation. Temporo-spatial regulation of odontoblast differentiation is dependent on matrix-mediated interactions involving the basement membrane (BM). Experimental studies have highlighted the possible roles of growth factors in these processes. Regulation of functional activity of odontoblasts allows for both ordered secretion of the primary dentin matrix and maintenance of vitality and down-regulation of secretory activity throughout secondary dentinogenesis. After injury to the mature tooth, the fate of the odontoblast can vary according to the intensity of the injury. Milder injury can result in up-regulation of functional activity leading to focal secretion of a reactionary dentin matrix, while greater injury can lead to odontoblast cell death. Induction of differentiation of a new generation of odontoblast-like cells can then lead to reparative dentinogenesis. Many similarities exist between development and repair, including matrix-mediation of the cellular processes and the apparent involvement of growth factors as signaling molecules despite the absence of epithelium during repair. While some of the molecular mediators appear to be common to these processes, the close regulation of primary dentinogenesis may be less ordered during tertiary dentinogenic responses. [ABSTRACT FROM AUTHOR]

Objectives and Methods: Tumor dormancy and resistance to cytotoxic agents are key limiting events in the treatment of malignant diseases. To determine whether both are influenced by the extracellular milieu in which tumors reside, HT1080 human fibrosarcoma, MCF-7 breast carcinoma and OSCORT osteosarcoma cell proliferation, viability, apoptosis and cytoreductive-treatment-induced death were investigated in the presence or absence of extracellular matrix (ECM). Results: ECM-adherent, but not plastic-adherent HT1080 cells formed a multicellular network accompanied by reduced proliferation and lowered DNA synthetic capacity. The number of cells in S-phase was dramatically reduced. Viable cells entered a state of dormancy reminiscent of that observed in the step of metastasis after extravasation, i.e. prior to the initiation of progressive growth. Such ECM-induced dormancy could be reversed by plating cells on plastic, but only after a 48-hour lag period. No difference was indicated in clonogenicity of HT1080 cells originated from plastic or ECM gel. However, the cells released from ECM gel showed significantly reduced migration ability. The resistance of anchored cells against cytotoxic damage was increased by ECM gel. Examination of cytoreductive treatment revealed that ECM adherence at the time of injury is partially protective, a property which was also moderately apparent when injured cells were transferred to the basement membrane. Conclusions: Taken together, these results suggest that the ECM plays a key role in tumor dormancy and cytotoxic resistance, both explorable at the molecular level using our in vitro model system.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Laminins may play important roles in gastric gland development due to the differential localization of their α chains in human fetal fundic (oxyntic) mucosa. To extend this hypothesis, the current investigation was undertaken to compare the anatomical and cellular distribution of epithelial integrin subunits with those of laminin α chains in the human stomach at different ages (8–22 weeks of gestation) using indirect immunofluorescence. In the body, fundus and antrum regions, the β1 and α6 subunits were associated with the entire epithelium at all developmental stages in the same way as laminin chains (α1/α5) detected with 4C7 monoclonal antibody. By contrast, the α3 and β4 subunits of α3β1 and α6β4 integrins together with the laminin α3-chain were concentrated in the surface and foveolus compartments composed of differentiating mucous cells. Most importantly, the α2 integrin subunit was expressed in a rather complex pattern: (1) it was located at the base and at cell-cell boundaries of surface/foveolar epithelium, (2) was specifically repressed in differentiating parietal cells, and (3) its expression increased in maturing glands, where it became concentrated at the basal pole of epithelial cells simultaneously exhibiting a strong reactivity for laminin-2 (α2-chain). Taken altogether, our observations provide new evidence for the implication of different laminins and their receptors in the development of all human gastric epithelial lineages, surface mucous cells or glandular cells. The coordinated expression of α2 and α3 integrin subunits as well as the cellular re-distribution of α2β1 integrin likely represent key events for the differentiation of glandular secretory cell types, especially maturing chief cells responsible for the synthesis/secretion of gastric digestive enzymes in fundic-type glands. [ABSTRACT FROM AUTHOR]

Tissue contractures are processes of cell-mediated contraction, irreversible in nature and typically associated with fibrotic phenomena. Contractures can be reproduced in vitro; here, we have used a medium-throughput model based on fibroblast-seeded fibrin (the 'contracture well'). Firstly, we show how profoundly these processes depend on the location of the contractile cells: when on top of the material, fibroblasts produce an interfacial contracture (analog to capsular contraction around an implant), which tries and bends the construct; when seeded inside the material, they initiate a bulk contracture (analogue to a wound bed closure) that shrinks it from within. Secondly, we demonstrate that the interfacial and bulk contractures are also mechanically and biologically different processes. Thirdly, we show the potentially predictive value of this model, since it not only recapitulates the effect of pro-fibrotic factors (TGF-β1 for dermal (myo)fibroblasts), but can also indicate the fibrotic potential of a given cell population (here, dystrophic myoblasts more fibrotic than healthy or genetically corrected ones), which may have important implications in the identification of appropriate therapies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

The extracellular matrix provides mechanical cues to cells within it, not just in terms of stiffness (elasticity) but also time-dependent responses to deformation (viscoelasticity). In this work, we determined the viscoelastic transformation of gelatine methacryloyl (GelMA) hydrogels caused by adipose tissue-derived stromal cells (ASCs) through mathematical modelling. GelMA-ASCs combination is of interest to model stem cell-driven repair and to understand cell-biomaterial interactions in 3D environments. Immortalised human ASCs were embedded in 5%, 10%, and 15% (w/v) GelMA hydrogels and evaluated for 14 d. GelMA had a concentration-dependent increase in stiffness, but cells decreased this stiffness over time, across concentrations. Viscoelastic changes in terms of stress relaxation increased progressively in 5% GelMA, while mathematical Maxwell analysis showed that the relative importance (Ri) of the fastest Maxwell elements increased proportionally. The 10% GelMA only showed differences at 7 d. In contrast, ASCs in 15% GelMA caused slower stress relaxation, increasing the Ri of the slowest Maxwell element. We conclude that GelMA concentration influenced the stiffness and number of Maxwell elements. ASCs changed the percentage stress relaxation and Ri of Maxwell elements transforming hydrogel viscoelasticity into a more fluid environment over time. Overall, 5% GelMA induced the most favourable ASC response. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells, also called medicinal signaling cells (MSC), have been studied regarding their potential to facilitate tissue repair for >30 years. Such cells, derived from multiple tissues and species, are capable of differentiation to a number of lineages (chondrocytes, adipocytes, bone cells). However, MSC are believed to be quite heterogeneous with regard to several characteristics, and the large number of studies performed thus far have met with limited or restricted success. Thus, there is more to understand about these cells, including the molecular recognition systems that are used by these cells to perform their functions, to enhance the realization of their potential to effect tissue repair. This perspective article reviews what is known regarding the recognition systems available to MSC, the possible systems that could be looked for, and alternatives to enhance their localization to specific injury sites and increase their subsequent facilitation of tissue repair. MSC are reported to express recognition molecules of the integrin family. However, there are a number of other recognition molecules that also could be involved such as lectins, inducible lectins, or even a MSC-specific family of molecules unique to these cells. Finally, it may be possible to engineer expression of recognition molecules on the surface of MSC to enhance their function in vivo artificially. Thus, improved understanding of recognition molecules on MSC could further their success in fostering tissue repair. [ABSTRACT FROM AUTHOR]

Regulation of survival and death of mesangial cells by extracellular matrix. Background. Cell-matrix interactions exert major effects on such phenotypic features as cell growth and differentiation. Apoptosis is an active form of cell death that is crucial for maintaining the appropriate number of cells as well as the organization of tissue. Recently, it has been suggested that apoptosis of the mesangial cells (MC) is important in glomerular remodeling after injury. The MC are surrounded by an extracellular matrix (ECM) in vivo . Since in disease conditions the mesangial matrix is altered quantitatively and qualitatively, it is of interest to determine whether cell-matrix interactions may influence apoptosis of the MC. Methods. We first investigated the differences in the susceptibility to apoptotic stimuli of the MC cultured on various ECM components (type I collagen, fibronectin, basement membrane matrix). We then determined whether the inhibition of MC-matrix interactions would affect apoptosis. Finally, interactions between MC and matrix were disrupted by the inhibition of β1 -integrin expression with antisense oligonucleotides (ODN). Results. When MC were cultured on type I collagen or fibronectin and deprived of serum for eight hours, the extracted DNA from the MC demonstrated an internucleosomal ladder pattern on gel electrophoresis that constituted the biochemical characteristic of apoptosis. However, no ladder pattern was apparent when MC were cultured on basement membrane matrix. The attachment of cells was completely inhibited when the MC were cultured on agarose-coated dishes for 24 hours. Gel electrophoresis of DNA extracted from these cells showed a ladder pattern. However, the MC attached to the substratum did not show any apoptosis. MC showed an increase in apoptotic cell death after treatment with antisense ODN against β1 -integrin molecule. Conclusions. These results indicate that normal ECM may prevent the MC... [ABSTRACT FROM AUTHOR]

Systemic scleroderma (SSc) is a complex connective tissue disorder of unknown etiology. In early stages of the disease, fibroblasts are activated to produce large amounts of collagen with subsequent fibrosis. Collagen metabolism of fibroblasts is modulated by their contact with the extracellular matrix (ECM), which involves distinct receptors on the cell surface, mainly belonging to the integrins. We investigated the expression of collagen receptor α[sub2]&beta[sub1] in SSc and normal fibroblasts, since this receptor has been shown to he utilized by fibroblasts for adhesion to and reorganization of collagen 1. 9 strains of scleroderma fibroblasts grown as monolayer cultures were first analyzed with respect to their collagen I expression. 6 of these strains were similar to controls ("low" producers) and 3 strains showed up to 2-3 X higher levels of collagen I mRNA expression ("high" producers). Northern hybridization using a cDNA probe specific for the α[sub2] integrin subunit revealed a decrease of the corresponding mRNA in SSc fibroblasts as compared to controls (75% versus 100%). "High" collagen producing cell strains displayed the lowest values for α[sub2] integrin mRNA. The decrease of α[sub2] integrin subunit expression at the mRNA level in selected fibroblasts was further substantiated by radioimmunoprecipitation using specific mAbs directed against α[sub2] integrin subunit. No significant changes in &beta[sub1] integrin expression could be observed -- neither at mRNA nor at the protein level. Our data indicate a correlation between excessive synthesis of collagen and low levels of α[sub2] integrin subunit expression in SSc fibroblasts. Further experiments should clarify whether this observation is a phenomenon specific for scleroderma or whether it reflects an "activated" state of fibroblasts. [ABSTRACT FROM AUTHOR]

Traction forces developed by most cell types play a significant role in the spatial organisation of biological tissues. However, due to the complexity of cell-extracellular matrix interactions, these forces are quantitatively difficult to estimate without explicitly considering cell properties and extracellular mechanical matrix responses. Recent experimental devices elaborated for measuring cell traction on extracellular matrix use cell deposits on a piece of gel placed between one fixed and one moving holder. We formulate here a mathematical model describing the dynamic behaviour of the cell-gel medium in such devices. This model is based on a mechanical force balance quantification of the gel visco-elastic response to the traction forces exerted by the diffusing cells. Thus, we theoretically analyzed and simulated the displacement of the free moving boundary of the system under various conditions for cells and gel concentrations. This modelis then used as the theoretical basis of an experimental device where endothelial cells are seeded on a rectangular biogel of fibrin cast between two floating holders, one fixed and the other linked to a force sensor. From a comparison of displacement of the gel moving boundary simulated by the model and the experimental data recorded from the moving holder displacement, the magnitude of the traction forces exerted by the endothelial cell on the fibrin gel was estimated for different experimental situations. Different analytical expressions for the cell traction term are proposed and the corresponding force quantifications are compared to the traction force measurements reported for various kind of cells with the use of similar or different experimental devices. [ABSTRACT FROM AUTHOR]

The extracellular matrix (ECM) provides structural support and adhesive substrates for the body tissues. Recent advances in our understanding of the biology of matrix indicate that the ECM also plays a significant role in regulating the behavior of cells. Matrix proteins engender changes in cell shape and movement, bind growth factors, and facilitate cell-cell and cell-matrix interactions. Matrix-induced differentiation results from multiple stimuli that include: tensile forces on the cell, cytokine- or growth factor-mediated stimulation, and interaction with bioactive domains of matrix glycoproteins. Because these signals are important determinants of cell behavior, pharmacological manipulation of cell-matrix interactions may offer a valuable new approach to disease treatment. [ABSTRACT FROM AUTHOR]

The bone marrow microenvironment plays an important role in promoting hematopoietic progenitor cell proliferation and differentiation and the controlled egress of these developing hematopoietic cells. The establishment of long-term bone marrow cultures, which are thought to mimic hematopoiesis in vitro, and various stromal cell lines has greatly facilitated the analysis of the functions of this microenvironment. Extracellular matrix (ECM) molecules of all three categories (collagens, proteoglycans and glycoproteins) have been identified as part of this microenvironment and have been shown to be involved in, different biological functions such as cell adhesion and anti-adhesion, binding and presentation of various cytokines and regulation of cell growth. It is suggested that these matrix molecules in combination with cytokines are crucial for compartmentalization of the bone marrow. Although many cell adhesion molecules have been characterized on the surface of hematopoietic progenitor cells, the nature of cellular receptors for the ECM components is less well defined. During leukemia, many immature blood cells are released from bone marrow, but it is not yet known whether these abnormalities in hematopoiesis are also caused by an altered microenvironment or altered composition of its extracellular matrix. The elucidation of the involvement of specific ECM-isoforms and as yet not characterized ECM components and their receptors in the bone marrow will certainly help towards a better understanding of these phenomena. [ABSTRACT FROM AUTHOR]

The extracellular matrix is formed by complex and intricate networks within which molecules are precisely organized. These molecular networks determine the specific histoarchitecture of tissues and provide cells with information and a scaffold. Most of the structural extracellular matrix molecules – collagens, noncollagenous glycoproteins, and proteoglycans – are chimeric and share common domains. Studies of the interactions between extracellular matrix molecules and mapping of the interaction sites to defined structural modules have led to the concept that the function of the extracellular matrix relies largely in the polymers that they form. Furthermore, determination of the tertiary structure of protein motifs involved either in the assembly of the various molecules into polymers or in cell–extracellular matrix interactions has recently opened the field of structural biology of the extracellular matrix. [ABSTRACT FROM AUTHOR]