Nanotopography-induced changes in focal adhesions, cytoskeletal organization, and mechanical properties of human mesenchymal stem cells.

The growth of stem cells can be modulated by physical factors such as extracellular matrix nanotopography. We hypothesize that nanotopography modulates cell behavior by changing the integrin clustering and focal adhesion (FA) assembly, leading to changes in cytoskeletal organization and cell mechanical properties. Human mesenchymal stem cells (hMSCs) cultured on 350 nm gratings of tissue-culture polystyrene (TCPS) and polydimethylsiloxane (PDMS) showed decreased expression of integrin subunits alpha2, alpha , alpha V, beta2, beta 3 and beta 4 compared to the unpatterned controls. On gratings, the elongated hMSCs exhibited an aligned actin cytoskeleton, while on unpatterned controls, spreading cells showed a random but denser actin cytoskeleton network. Expression of cytoskeleton and FA components was also altered by the nanotopography as reflected in the mechanical properties measured by atomic force microscopy (AFM) indentation. On the rigid TCPS, hMSCs on gratings exhibited lower instantaneous and equilibrium Young's moduli and apparent viscosity. On the softer PDMS, the effects of nanotopography were not significant. However, hMSCs cultured on PDMS showed lower cell mechanical properties than those on TCPS, regardless of topography. These suggest that both nanotopography and substrate stiffness could be important in determining mechanical properties, while nanotopography may be more dominant in determining the organization of the cytoskeleton and FAs.

Measurement of intracellular strain on deformable substrates with texture correlation.

Mechanical stimuli are important factors that regulate cell proliferation, survival, metabolism and motility in a variety of cell types. The relationship between mechanical deformation of the extracellular matrix and intracellular deformation of cellular sub-regions and organelles has not been fully elucidated, but may provide new insight into the mechanisms involved in transducing mechanical stimuli to biological responses. In this study, a novel fluorescence microscopy and image analysis method was applied to examine the hypothesis that mechanical strains are fully transferred from a planar, deformable substrate to cytoplasmic and intranuclear regions within attached cells. Intracellular strains were measured in cells derived from the anulus fibrosus of the intervertebral disc when attached to an elastic silicone membrane that was subjected to tensile stretch. Measurements indicated cytoplasmic strains were similar to those of the underlying substrate, with a strain transfer ratio (STR) of 0.79. In contrast, nuclear strains were much smaller than those of the substrate, with an STR of 0.17. These findings are consistent with previous studies indicating nuclear stiffness is significantly greater than cytoplasmic stiffness, as measured using other methods. This study provides a novel method for the study of cellular mechanics, including a new technique for measuring intranuclear deformations, with evidence of differential magnitudes and patterns of strain transferred from the substrate to cell cytoplasm and nucleus.

Mechanobiology of the meniscus.

The meniscus plays a critical biomechanical role in the knee, providing load support, joint stability, and congruity. Importantly, growing evidence indicates that the mechanobiologic response of meniscal cells plays a critical role in the physiologic, pathologic, and repair responses of the meniscus. Here we review experimental and theoretical studies that have begun to directly measure the biomechanical effects of joint loading on the meniscus under physiologic and pathologic conditions, showing that the menisci are exposed to high contact stresses, resulting in a complex and nonuniform stress-strain environment within the tissue. By combining microscale measurements of the mechanical properties of meniscal cells and their pericellular and extracellular matrix regions, theoretical and experimental models indicate that the cells in the meniscus are exposed to a complex and inhomogeneous environment of stress, strain, fluid pressure, fluid flow, and a variety of physicochemical factors. Studies across a range of culture systems from isolated cells to tissues have revealed that the biological response of meniscal cells is directly influenced by physical factors, such as tension, compression, and hydrostatic pressure. In addition, these studies have provided new insights into the mechanotransduction mechanisms by which physical signals are converted into metabolic or pro/anti-inflammatory responses. Taken together, these in vivo and in vitro studies show that mechanical factors play an important role in the health, degeneration, and regeneration of the meniscus. A more thorough understanding of the mechanobiologic responses of the meniscus will hopefully lead to therapeutic approaches to prevent degeneration and enhance repair of the meniscus.

Genome-wide association study of perioperative myocardial infarction after coronary artery bypass surgery.

OBJECTIVES: Identification of patient subpopulations susceptible to develop myocardial infarction (MI) or, conversely, those displaying either intrinsic cardioprotective phenotypes or highly responsive to protective interventions remain high-priority knowledge gaps. We sought to identify novel common genetic variants associated with perioperative MI in patients undergoing coronary artery bypass grafting using genome-wide association methodology. SETTING: 107 secondary and tertiary cardiac surgery centres across the USA. PARTICIPANTS: We conducted a stage I genome-wide association study (GWAS) in 1433 ethnically diverse patients of both genders (112 cases/1321 controls) from the Genetics of Myocardial Adverse Outcomes and Graft Failure (GeneMAGIC) study, and a stage II analysis in an expanded population of 2055 patients (225 cases/1830 controls) combined from the GeneMAGIC and Duke Perioperative Genetics and Safety Outcomes (PEGASUS) studies. Patients undergoing primary non-emergent coronary bypass grafting were included. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome variable was perioperative MI, defined as creatine kinase MB isoenzyme (CK-MB) values ≥10× upper limit of normal during the first postoperative day, and not attributable to preoperative MI. Secondary outcomes included postoperative CK-MB as a quantitative trait, or a dichotomised phenotype based on extreme quartiles of the CK-MB distribution. RESULTS: Following quality control and adjustment for clinical covariates, we identified 521 single nucleotide polymorphisms in the stage I GWAS analysis. Among these, 8 common variants in 3 genes or intergenic regions met p<10(-5) in stage II. A secondary analysis using CK-MB as a quantitative trait (minimum p=1.26×10(-3) for rs609418), or a dichotomised phenotype based on extreme CK-MB values (minimum p=7.72×10(-6) for rs4834703) supported these findings. Pathway analysis revealed that genes harbouring top-scoring variants cluster in pathways of biological relevance to extracellular matrix remodelling, endoplasmic reticulum-to-Golgi transport and inflammation. CONCLUSIONS: Using a two-stage GWAS and pathway analysis, we identified and prioritised several potential susceptibility loci for perioperative MI.

Ectopic expression of the Ets transcription factor ER81 in transgenic mouse mammary gland enhances both urokinase plasminogen activator and stromelysin-1 transcription

The PEA3 group members PEA3, ER81 and ERM, which are highly conserved transcription factors from the Ets family, are over-expressed in metastatic mammary tumors. In the current study, we present the characterization of a transgenic mouse strain which over-expresses ER81 in the mammary gland via the long terminal repeat of the mouse mammary tumor virus (LTR-MMTV). Although six genotypically positive transgenic lines were identified, only one expressed the ectopic transcript with an exclusive expression in the lactating and late-pregnancy (18th day) mammary glands. No mammary tumor or mammary deregulation appeared after 2 years of ectopic ER81 expression following lactation. We then sought to identify ER81 target genes, and the urokinase plasminogen activator (uPA) and the stromelysin-1, two enzymes involved in extracellular matrix degradation, were found to be transcriptionally upregulated in lactating mammary glands over-expressing ER81. Since these enzymes are involved in metastasis, this murine model could be further used to enhance mammary cancer metastatic process by crossing these animals with mice carrying non-metastatic mammary tumors. We thus created a transgenic mouse model permitting the over-expression of a functionally active Ets transcription factor in the mammary gland without perturbing its development.

Three-dimensional cultures of normal human osteoblasts: proliferation and differentiation potential in vitro and upon ectopic implantation in nude mice.

This paper is novel andreports on the in vitro establishment of 3-D cultures of human osteoblasts. These were evaluated for protein markers of bone cells. Sequentially alkaline phosphatase, calcium incorporation for matrix mineralisation and then finally osteocalcin expression were detected in cultures. The extracellular matrix was composed of type 1 collagen and as it mineralised, needle shaped crystals were often associated with matrix vesicles initiating mineralisation. In vivo implantation in nude mice showed progression of mineralisation from the inner region outward with peripheral cells in a non-mineralised matrix. Host vessels invaded the implanted cell area. The research has relevance to musculoskeletal tissue engineering.

The regulation and role of osteopontin in malignant transformation and cancer.

Osteopontin (OPN) is a predominantly secreted extracellular matrix glycophosphoprotein which binds to alpha v-containing integrins and has an important role in malignant cell attachment and invasion. High OPN expression in the primary tumor is associated with early metastasis and poor outcome in human breast and other cancers. Forced OPN overexpression in benign cells may induce neoplastic-like cell behaviour including increased attachment and invasion in vitro as well as the ability to metastasize in vivo. Conversely, OPN inhibition by antisense cDNA impedes cell growth and tumor forming capacity. OPN is not mutationally activated in cancer but its expression is regulated by Wnt/Tcf signaling, steroid receptors, growth factors, ras, Ets and AP-1 transcription factors. Presumably these factors are implicated in induction of OPN overexpression in cancer. Greater understanding of the role of OPN in neoplastic change and its transcriptional regulation may enable development of novel cancer treatment strategies

The 67 kDa laminin receptor: structure, function and role in disease

The 67LR (67 kDa laminin receptor) is a cell-surface receptor with high affinity for its primary ligand. Its role as a laminin receptor makes it an important molecule both in cell adhesion to the basement membrane and in signalling transduction following this binding event. The protein also plays critical roles in the metastasis of tumour cells. Isolation of the protein from either normal or cancerous cells results in a product with an approx. molecular mass of 67 kDa. This protein is believed to be derived from a smaller precursor, the 37LRP (37 kDa laminin receptor precursor). However, the precise mechanism by which cytoplasmic 37LRP becomes cell-membrane-embedded 67LR is unclear. The process may involve post-translational fatty acylation of the protein combined with either homo- or hetero-dimerization, possibly with a galectin-3-epitope-containing partner. Furthermore, it has become clear that acting as a receptor for laminin is not the only function of this protein. 67LR also acts as a receptor for viruses, such as Sindbis virus and dengue virus, and is involved with internalization of the prion protein. Interestingly, unmodified 37LRP is a ribosomal component and homologues of this protein are found in all five kingdoms. In addition, it appears to be strongly associated with histones in the eukaryotic cell nucleus, although the precise role of these interactions is not clear. Here we review the current understanding of the structure and function of this molecule, as well as highlighting areas requiring further research.

Advanced glycation end product (AGE) accumulation on Bruch's membrane: links to age-related RPE dysfunction.

PURPOSE: Advanced glycation end products (AGEs) accumulate during aging and have been observed in postmortem eyes within the retinal pigment epithelium (RPE), Bruch's membrane, and subcellular deposits (drusen). AGEs have been associated with age-related dysfunction of the RPE-in particular with development and progression to age-related macular degeneration (AMD). In the present study the impact of AGEs at the RPE-Bruch's membrane interface was evaluated, to establish how these modifications may contribute to age-related disease. METHODS: AGEs on Bruch's membrane were evaluated using immunohistochemistry. A clinically relevant in vitro model of substrate AGE accumulation was established to mimic Bruch's membrane ageing. Responses of ARPE-19 growing on AGE-modified basement membrane (AGE-BM) for 1 month were investigated by using a microarray approach and validated by quantitative (q)RT-PCR. In addition to identified AGE-related mRNA alterations, lysosomal enzyme activity and lipofuscin accumulation were also studied in ARPE-19 grown on AGE-BM. RESULTS: Autofluorescent and glycolaldehyde-derived AGEs were observed in clinical specimens on Bruch's membrane and choroidal extracellular matrix. In vitro analysis identified a range of dysregulated mRNAs in ARPE-19 exposed to AGE-BM. Altered ARPE-19 degradative enzyme mRNA expression was observed on exposure to AGE-BM. AGE-BM caused a significant reduction in cathepsin-D activity in ARPE-19 (P

The role of advanced glycation end products in retinal ageing and disease

The retina is exposed to a lifetime of potentially damaging environmental and physiological factors that make the component cells exquisitely sensitive to age-related processes. Retinal ageing is complex and a raft of abnormalities can accumulate in all layers of the retina. Some of this pathology serves as a sinister preamble to serious conditions such as age-related macular degeneration (AMD) which remains the leading cause of irreversible blindness in the Western world.

The formation of advanced glycation end products (AGEs) is a natural function of ageing but accumulation of these adducts also represents a key pathophysiological event in a range of important human diseases. AGEs act as mediators of neurodegeneration, induce irreversible changes in the extracellular matrix, vascular dysfunction and pro-inflammatory signalling. Since many cells and tissues of the eye are profoundly influenced by such processes, it is fitting that advanced glycation is now receiving considerable attention as a possible pathogenic factor in visual disorders.

This review presents the current evidence for a pathogenic role for AGEs and activation of the receptor for AGEs (RAGE) in initiation and progression of retinal disease. It draws upon the clinical and experimental literature and highlights the opportunities for further research that would definitively establish these adducts as important instigators of retinal disease. The therapeutic potential for novel agents that can ameliorate AGE formation of attenuate RAGE signalling in the retina is also discussed.

MMP expression and abnormal lung permeability are important determinants of outcome in IPF

Matrix metalloproteinases (MMPs) degrade all of the extracellular matrix components of the intersititium and may play a role in abnormal alveolar permeability, which is a feature of idiopathic pulmonary fibrosis (IPF). The aims of the present study were to evaluate MMP protein levels in patients with IPF and determine any relationship to treatment and markers of permeability.

Antibody Targeting of Cathepsin S Inhibits Angiogenesis and Synergistically Enhances Anti-VEGF

BACKGROUND: Angiogenesis is a key hallmark of tumourigenesis and its inhibition is a proven strategy for the development of novel anti-cancer therapeutics. An important aspect of early angiogenesis is the co-ordinated migration and invasion of endothelial cells through the hypoxic tumour tissue. Cathepsin S has been shown to play an important role in angiogenesis as has vascular endothelial growth factor (VEGF). We sought to assess the anti-angiogenic effect of Fsn0503, a novel cathepsin S inhibitory antibody, when combined with anti-VEGF on vascular development.

METHODOLOGY/PRINCIPAL FINDINGS: Cathepsin S expression and secretion from endothelial cells was characterised using RT-PCR and western blotting. We further show that cathepsin S promotes pericellular hydrolysis of extracellular matrix components in the tumour microenvironment and facilitates endothelial invasion. The cathepsin S inhibitory antibody, Fsn0503, blocks extracellular proteolysis, inhibiting endothelial invasion and tube formation in cell-based assays. The anti-angiogenic effects of Fsn0503 were also shown in vivo where it significantly retarded the development of vasculature in human xenograft models. Furthermore, when Fsn0503 was combined with an anti-VEGF antibody, a synergistic inhibition of microvascular development was observed.

CONCLUSIONS/SIGNIFICANCE: Taken together, this data demonstrates that the antibody-mediated targeting of cathepsin S represents a novel method of inhibiting angiogenesis. Furthermore, when used in combination with anti-VEGF therapies, Fsn0503 has the potential to significantly enhance current treatments of tumour neovascularisation and may also be of use in the treatment of other conditions associated with inappropriate angiogenesis.

Interactions of the 67 kDa laminin receptor and its precursor with laminin

The 67LR (67 kDa laminin receptor) enables cells to interact with components of the extracellular matrix The molecule is derived from the 37LRP (37 kDa laminin receptor precursor); however, the precise molecular mechanism of this conversion is unknown. Recombinant 37LRP expressed in and purified from Escherichia colt, bound to human laminin in a SPR (surface plasmon resonance) experiment. 67LR isolated from human breast-cancer-derived cells in culture was also shown to bind to laminin by SPR. However, the kinetics of association are qualitatively different. 37LRP but not 67LR, binds to heparan sulfate. The binding of 37LRP to heparan sulfate did not affect the interaction of 37LRP with laminin In contrast, heparan sulfate reduces the extent of binding of laminin to 67LR. Taken together, these results show that 37LRP has some of the biological activities of 67LR, even prior to the conversion event. However, the conversion affects the sites of interaction with both laminin and heparan sulfate.

The AGE inhibitor pyridoxamine inhibits development of retinopathy in experimental diabetes

We examined the ability of pyridoxamine (PM), an inhibitor of formation of advanced glycation end products (AGEs) and lipoxidation end products (ALEs), to protect against diabetes-induced retinal vascular lesions. The effects of PM were compared with the antioxidants vitamin E (VE) and R-alpha-lipoic acid (LA) in streptozotocin-induced diabetic rats. Animals were given either PM (1 g/l drinking water), VE (2,000 IU/kg diet), or LA (0.05%/kg diet). After 29 weeks of diabetes, retinas were examined for pathogenic changes, alterations in extracellular matrix (ECM) gene expression, and accumulation of the immunoreactive AGE/ALE N-epsilon-(carboxymethyl)lysine (CML). Acellular capillaries were increased more than threefold, accompanied by significant upregulation of laminin immunoreactivity in the retinal microvasculature. Diabetes also increased mRNA expression for fibronectin (2-fold), collagen IV (1.6-fold), and laminin beta chain (2.6-fold) in untreated diabetic rats compared with nondiabetic rats. PM treatment protected against capillary drop-out and limited laminin protein upregulation and ECM mRNA expression and the increase in CML in the retinal vasculature. VE and LA failed to protect against retinal capillary closure and had inconsistent effects on diabetes-related upregulation of ECM mRNAs. These results indicate that the AGE/ALE inhibitor PM protected against a range of pathological changes in the diabetic retina and may be useful for treating diabetic retinopathy.

Ultraviolet exposure of melanoma cells induces fibroblast activation protein-α in fibroblasts: Implications for melanoma invasion.

Fibroblast activation protein-a (FAP-a) promotes tumor growth and cell invasiveness through extracellular matrix degradation. How ultraviolet radiation (UVR), the major risk factor for malignant melanoma, influences the expression of FAP-a is unknown. We examined the effect of UVR on FAP-a expression in melanocytes, keratinocytes and fibroblasts from the skin and in melanoma cells. UVR induces upregulation of FAP-a in fibroblasts, melanocytes and primary melanoma cells (PM) whereas keratinocytes and metastatic melanoma cells remained FAP-a negative. UVA and UVB stimulated FAP-a-driven migration and invasion in fibroblasts, melanocytes and PM. In co-culture systems UVR of melanocytes, PM and cells from regional metastases upregulated FAP-a in fibroblasts but only supernatants from non-irradiated PM were able to induce FAP-a in fibroblasts. Further, UV-radiated melanocytes and PM significantly increased FAP-a expression in fibroblasts through secretory crosstalk via Wnt5a, PDGF-BB and TGF-ß1. Moreover, UV radiated melanocytes and PM increased collagen I invasion and migration of fibroblasts. The FAP-a/DPPIV inhibitor Gly-ProP(OPh)2 significantly decreased this response implicating FAP-a/DPPIV as an important protein complex in cell migration and invasion. These experiments suggest a functional association between UVR and FAP-a expression in fibroblasts, melanocytes and melanoma cells implicating that UVR of malignant melanoma converts fibroblasts into FAP-a expressing and ECM degrading fibroblasts thus facilitating invasion and migration. The secretory crosstalk between melanoma and tumor surrounding fibroblasts is mediated via PDGF-BB, TGF-ß1 and Wnt5a and these factors should be evaluated as targets to reduce FAP-a activity and prevent early melanoma dissemination.