Cell–Matrix interactions, the role of fibronectin and integrins. A survey

Integrins as a bridge between bacteria and cells: key targets for therapeutic wound healing

Integrins are heterodimers composed of α and β subunits that are bonded through non-covalent interactions. Integrins mediate the dynamic connection between extracellular adhesion molecules and the intracellular actin cytoskeleton. Integrins are present in various tissues and organs where these heterodimers participate in diverse physiological and pathological responses at the molecular level in living organisms. Wound healing is a crucial process in the recovery from traumatic diseases and comprises three overlapping phases: inflammation, proliferation and remodeling. Integrins are regulated during the entire wound healing process to enhance processes such as inflammation, angiogenesis and re-epithelialization. Prolonged inflammation may result in failure of wound healing, leading to conditions such as chronic wounds. Bacterial colonization of a wound is one of the primary causes of chronic wounds. Integrins facilitate the infectious effects of bacteria on the host organism, leading to chronic inflammation, bacterial colonization, and ultimately, the failure of wound healing. The present study investigated the role of integrins as bridges for bacteria-cell interactions during wound healing, evaluated the role of integrins as nodes for bacterial inhibition during chronic wound formation, and discussed the challenges and prospects of using integrins as therapeutic targets in wound healing.

Effect of dental composite dust on human gingival keratinocytes

OBJECTIVE

The aim was to investigate the effect of particles released during grinding of dental composites on human gingival keratinocytes (HGK).

METHODS

Specimens from Filtek™ Supreme XTE and ceram.x® universal were prepared and ground to dust. The dust was filtered (≤ 5 µm) and the particle size distribution was examined using NANO-flex®-180° dynamic light scattering (DLS). Suspensions at five concentrations (3, 10, 30, 100 and 300 µg/mL) were prepared using keratinocyte growth medium (KGM). These suspensions, as well as a positive (CuO) and a negative control (KGM) were added to HGK. The cells treated with Filtek™ Supreme XTE suspensions were analyzed by real-time monitoring using RTCA iCELLigence™. In addition, light and scanning electron microscopic images of the exposed cells were taken. Indirect immunofluorescence staining was performed to detect the extracellular matrix protein fibronectin.

RESULTS

In distilled water, DLS showed similar particles' range (171.9 nm- 2.7 µm) for both composites. In saliva, larger particles were detected (Filtek™ Supreme XTE: 243 nm-6,5 µm; ceram.x® universal: 204 nm- 4,6 µm). iCELLigence™ revealed similar results of cell growth parameters for HGK incubated with composite dust (≤ 5 µm) at different concentrations. The microscopic images indicated unaltered cell structures and formation of large agglomerates with high particle concentration (> 100 µg/mL). Exposure to composite dust resulted in upregulation of fibronectin expression.

SIGNIFICANCE

Grinding of dental composite materials generates dust particles of different sizes. The particle size distribution seems to be more influenced by the suspending medium than the material itself. While cell growth of HGK seem not to be affected by the particles, an upregulation of fibronectin in the intercellular space concomitant by increasing particle concentration may indicate an increase of cell migration/mobility.

Synthesis, Characterization, In Vitro Cytological Responses, and In Vivo Bone Regeneration Effects of Low-Crystalline Nanocarbonated Hydroxyapatite

Hydroxyapatite (HA) has been commonly used as an alternative bone substitute. But it has drawbacks, such as poor degradation and limited osteogenesis. Low-crystalline carbonated hydroxyapatite (L-CHA), which has greater biodegradability than HA, is suggested as one of the main components of bone minerals, but the exact mechanism behind the roles of carbonate substituted in biological behaviors of low-crystalline HA is still a mystery. In this study, L-CHAs with different carbonate contents were prepared, and the effects of the content on the physicochemical properties, in vitro cytological responses, and in vivo bone defects repair effects of L-CHAs were investigated. The results demonstrated that CO₃^2- had successfully entered the lattice structure of L-CHAs with a maximum content of 9.2 wt %. Both low-crystalline undoped HA (L-HA) and L-CHAs were nanocrystalline (20-30 nm) with significantly higher specific surface areas, protein adsorption capacities, and biodegradability compared to high-crystalline HA (H-HA) with submicron crystalline size (200-400 nm). Besides, the amounts of the adsorbed protein and released Ca²⁺ ions increased in a carbonate-content-dependent manner. Compared to L-HA and H-HA, L-CHAs promoted the adhesion and proliferation of bone marrow mesenchymal stem cells and significantly upregulated the levels of alkaline phosphatase (ALP) activity and the expression of osteogenesis-related genes. In addition, L-CHA-9 not only showed a faster biodegradation rate but also effectively promoted bone regeneration when implanted in the critical-sized bone defects of rabbit femora. This study provided evidence for the development of L-CHA as a promising biodegradable and bioactive material with great osteoconductivity and osteogenic capability with respect to conventional HA.

Group A streptococci induce stronger M protein-fibronectin interaction when specific human antibodies are bound

Group A streptococcus (GAS) is a highly adapted, human-specific pathogen that is known to manipulate the immune system through various mechanisms. GAS' M protein constitutes a primary target of the immune system due to its spatial configuration and dominance on the bacterial surface. Antibody responses targeting the M protein have been shown to favor the conserved C region. Such antibodies (Abs) circumvent antigenic escape and efficiently bind to various M types. The ability of GAS to bind to fibronectin (Fn), a high molecular weight glycoprotein of the extracellular matrix, has long been known to be essential for the pathogen's evolutionary success and fitness. However, some strains lack the ability to efficiently bind Fn. Instead, they have been found to additionally bind Fn via the A-B domains of their M proteins. Here, we show that human Abs can induce increased Fn-binding affinity in M proteins, likely by enhancing the weak A-B domain binding. We found that this enhanced Fn binding leads to a reduction in Ab-mediated phagocytosis, indicating that this constitutes a GAS immune escape mechanism. We could show that the Fc domain of Abs is necessary to trigger this phenomenon and that Ab flexibility may also play a key role. We, moreover, saw that our Abs could enhance Fn binding in 3 out of 5 emm type strains tested, belonging to different clades, making it likely that this is a more generalizable phenomenon. Together our results suggest a novel synergistic interplay of GAS and host proteins which ultimately benefits the bacterium.

Silk-Based Bioengineered Diaphyseal Cortical Bone Unit Enclosing an Implantable Bone Marrow toward Atrophic Nonunion Grafting

Postnatal fracture healing of atrophic long bone diaphyseal nonunions remains a challenge for orthopedic surgeons. Paucity of autologous spongiosa has potentiated the use of tissue engineered bone grafts to improve success rates of bone marrow engraftment used in plate reosteosynthesis. Herein, the development and in vitro validation of a "sandwich-type" biofabricated diaphyseal cross-sectional unit, with an outer mechanically robust bioprinted cortical bone shell, encompassing an engineered bone marrow, are reported. Channelized silk fibroin blend sponges derived from Bombyx mori and Antheraea assama help in developing compartmentalized endosteum, exhibiting specialized osteoblasts (endosteal niche) and discontinuous endothelium (vascular niche). The cellular cross-talk between these two niches triggered via integrin-mediated cell adhesion, enables in preserving quiescence state of CD34⁺ /CD38^- hematopoietic stem cells and their recycling in the engineered marrow. The outer cortical bone strut is developed through multimaterial microextrusion bioprinting strategy. Osteogenically primed mesenchymal stem cells-laden silk fibroin-nano-hydroxyapatite bioink is bioprinted alongside paramagnetic Fe-doped bioactive glass-polycaprolactone blend thermoplastic ink, reinforcing it for mechanical stability. Pulsed magnetic field actuation positively influences the osteogenic commitment and maturation of the bioprinted constructs via mechanotransductory route. Therefore, the assembled engineered marrow and bioprinted cortical shell hold promise as potential orthobiologic substitutes toward atrophic nonunion repairs.

Endothelial Glycocalyx-Mediated Intercellular Interactions: Mechanisms and Implications for Atherosclerosis and Cancer Metastasis

Purpose

The endothelial glycocalyx (GCX) plays a critical role in the health of the vascular system. Degradation of the GCX has been implicated in the onset of diseases like atherosclerosis and cancer because it disrupts endothelial cell (EC) function that is meant to protect from atherosclerosis and cancer. Examples of such EC function include interendothelial cell communication via gap junctions and receptor-mediated interactions between endothelial and tumor cells. This review focuses on GCX-dependent regulation of these intercellular interactions in healthy and diseased states. The ultimate goal is to build new knowledge that can be applied to developing GCX regeneration strategies that can control intercellular interaction in order to combat the progression of diseases such as atherosclerosis and cancer.

Methods

In vitro and in vivo studies were conducted to determine the baseline expression of GCX in physiologically relevant conditions. Chemical and mechanical GCX degradation approaches were employed to degrade the GCX. The impact of intact versus degraded GCX on intercellular interactions was assessed using cytochemistry, histochemistry, a Lucifer yellow dye transfer assay, and confocal, intravital, and scanning electron microscopy techniques.

Results

Relevant to atherosclerosis, we found that GCX stability determines the expression and functionality of Cx43 in gap junction-mediated EC-to-EC communication. Relevant to cancer metastasis, we found that destabilizing the GCX through either disturbed flow-induced or enzyme induced GCX degradation results in increased E-selectin receptor-mediated EC-tumor cell interactions.

Conclusion

Our findings lay a foundation for future endothelial GCX-targeted therapy, to control intercellular interactions and limit the progression of atherosclerosis and cancer.

Composition, structure and function of the corneal stroma

No other tissue in the body depends more on the composition and organization of the extracellular matrix (ECM) for normal structure and function than the corneal stroma. The precise arrangement and orientation of collagen fibrils, lamellae and keratocytes that occurs during development and is needed in adults to maintain stromal function is dependent on the regulated interaction of multiple ECM components that contribute to attain the unique properties of the cornea: transparency, shape, mechanical strength, and avascularity. This review summarizes the contribution of different ECM components, their structure, regulation and function in modulating the properties of the corneal stroma. Fibril forming collagens (I, III, V), fibril associated collagens with interrupted triple helices (XII and XIV), network forming collagens (IV, VI and VIII) as well as small leucine-rich proteoglycans (SLRP) expressed in the stroma: decorin, biglycan, lumican, keratocan, and fibromodulin are some of the ECM components reviewed in this manuscript. There are spatial and temporal differences in the expression of these ECM components, as well as interactions among them that contribute to stromal function. Unique regions within the stroma like Bowman's layer and Descemet's layer are discussed. To define the complexity of corneal stroma composition and structure as well as the relationship to function is a daunting task. Our knowledge is expanding, and we expect that this review provides a comprehensive overview of current knowledge, definition of gaps and suggests future research directions.

Galectin-8 mediates fibrogenesis induced by cyclosporine in human gingival fibroblasts

BACKGROUND AND OBJECTIVE

During cyclosporine-induced gingival overgrowth, the homeostatic balance of gingival connective tissue is disrupted leading to fibrosis. Galectins are glycan-binding proteins that can modulate a variety of cellular processes including fibrosis in several organs. Here, we study the role of galectin-8 (Gal-8) in the response of gingival connective tissue cells to cyclosporine.

METHODS

We used human gingival fibroblasts and mouse NIH3T3 cells treated with recombinant Gal-8 and/or cyclosporine for analyzing specific mRNA and protein levels through immunoblot, real-time polymerase chain reaction, ELISA and immunofluorescence, pull-down with Gal-8-Sepharose for Gal-8-to-cell surface glycoprotein interactions, short hairpin RNA for Gal-8 silencing and Student's t test and ANOVA for statistical analysis.

RESULTS

Galectin-8 stimulated type I collagen and fibronectin protein levels and potentiated CTGF protein levels in TGF-β1-stimulated human gingival fibroblasts. Gal-8 interacted with α5β1-integrin and type II TGF-β receptor. Gal-8 stimulated fibronectin protein and mRNA levels, and this response was dependent on FAK activity but not Smad2/3 signaling. Cyclosporine and tumor necrosis factor alpha (TNF-α) increased Gal-8 protein levels. Finally, silencing of galectin-8 in NIH3T3 cells abolished cyclosporine-induced fibronectin protein levels.

CONCLUSION

Taken together, these results reveal for the first time Gal-8 as a fibrogenic stimulus exerted through β1-integrin/FAK pathways in human gingival fibroblasts, which can be triggered by cyclosporine. Further studies should explore the involvement of Gal-8 in human gingival tissues and its role in drug-induced gingival overgrowth.

Experimental implantoplasty outcomes correlate with fibroblast growth in vitro

BACKGROUND

Implantoplasty is an option in peri-implantitis treatment, but little is known about the effect on the soft tissue. The aim of the study was to characterize surface roughness following experimental implantoplasty and to examine its effect on human fibroblast growth and secretion of selected proteins.

METHODS

Titanium grade IV coins were mechanically treated with six different rotating bur sequences; diamond burs or carbide burs alone, or followed by either Arkansas stone bur or silicone burs. Machined and rough-surface sandblasted, acid-etched (SLA) coins were used as control. The surface topography was characterized by scanning electron microscope and profilometer. Human gingival fibroblasts from two donors were cultured on the coins to quantify the effect on cell morphology, growth, and protein secretion by confocal microscopy and multiplex immunoassay.

RESULTS

All surface roughness parameters were lower for the surfaces treated with experimental implantoplasty than for the SLA surface, and the sequence of carbide burs followed by silicone burs rendered the least rough surface of the test groups. The implantoplasty procedures changed the elemental composition of the titanium surface. High surface roughness showed a weak to moderate negative correlation to fibroblast growth, but induced a higher secretion of VEGF, IL-6 and MCP-3 to the cell medium compared to the least rough surfaces of the test groups. At day 30 fibronectin levels were higher in the SLA group.

CONCLUSIONS

The surface roughness following implantoplasty demonstrated a weak to moderate negative correlation with the growth of fibroblasts. The addition of Arkansas stone and silicon burs to the experimental implantoplasty bur protocol rendered an initial increase in fibroblast growth. Implantoplasty altered the elemental composition of the titanium surface, and had an effect on the fibroblast cytokine secretion and fibronectin levels.

Placental fibronectin staining is unaffected in pregnancies complicated by late-onset intrauterine growth restriction and small for gestational age fetuses

OBJECTIVE

To investigate the placental staining pattern of fibronectin, an extracellular matrix protein essential for trophoblastic invasion, in pre-eclampsia and fetal growth restriction.

METHODS

This was a retrospective study conducted at the University of Udine, including the placentas of women with pre-eclampsia and fetal growth restriction collected between January 1, 2001, and December 31, 2010. Fibronectin was evaluated in placental tissue micro-array by immunohistochemistry, describing localization and intensity of staining.

RESULTS

The study included the placentas of 36 women with early-onset (delivery <34 weeks of gestation) pre-eclampsia; 6 with early-onset HELLP syndrome; 17 with early-onset intrauterine growth restriction (IUGR); 14 with late-onset (delivery ≥34 weeks of gestation) pre-eclampsia; 35 with late-onset IUGR; 18 with small for gestational age (SGA) fetuses (birth weight <10th percentile); and 64 controls. Fibronectin was present both at the cell surface and in the cytoplasm. Cytoplasm staining intensity resulted higher in early forms of pregnancy-related complications compared to controls, although this was statistically significant (P<0.05) only for early-onset pre-eclampsia (P=0.085 for HELLP syndrome; P=0.091 for IUGR). Also, late-onset forms of pre-eclampsia had stronger cytoplasmic and pericellular staining compared to controls (P<0.05). Interestingly, staining of both late-onset IUGR and SGA was comparable to controls.

CONCLUSION

Fibronectin appeared to be unaffected in women with late-onset IUGR and SGA fetuses, suggesting a peculiar common pathogenetic pattern in these conditions.

An accessible and high-throughput strategy of continuously monitoring apoptosis by fluorescent detection of caspase activation

We present a real-time, high-throughput, and cost-effective method of detecting apoptosis in vitro using a previously developed reagent that detects caspase activation by fluorescence. Current methods of assessing apoptosis fail to account for the dimension of time, and thus are limited in data yielded per sample. This reagent allows real-time detection of apoptosis, but until now has been restricted to a costly automated detection system. Here, we describe apoptosis detection with the Essen Bioscience IncuCyte^® Caspase-3/7 Reagent using a multimode microplate reader, a common instrument in biological laboratories, which may be used prior to or in lieu of the automated system. This modified microplate reader apoptosis assay was validated against the established automated system, and was shown to detect a strong dose-response relationship (automated system r² = 0.9968, microplate reader r² = 0.9924). We also propose a quick and reliable method of quantifying cell density by Hoechst 33342 nuclear staining in microplates (r² = 0.8812 between Hoechst signal and cell density). We assert that the dimension of time should not be overlooked, and that the method presented here is an accessible strategy for many researchers due to low startup cost and precise detection of apoptosis in real time.

Fibronectin Regulates the Dynamic Formation of Ovarian Cancer Multicellular Aggregates and the Expression of Integrin Receptors

Objective:

To investigate the regulatory role of fibronectin (FN) in the formation of multicellular aggregate (MCA) in ovarian cancer SKOV3 and OVCAR-3 cells and integrin expression.

Methods:

The dynamic formation of MCA in SKOV3 and OVCAR-3 was determined using the liquid overlay technique in the presence or absence of FN, anti-FN, RGD peptide, control RGE. The expression of α3β1, α4β1 and α5β1 integrin in monolayer cells, MCA and FN-treated MCA were determined by flow cytometry and quantitative RT-PCR.

Results:

OVCAR-3 and SKOV3 MCA were formed on the 4th and 8th day and peaked on the 6th and 9th day, respectively. Treatment with different concentrations of FN, LN, type IV collagen and control RGE peptide promoted MCA growth, which was mitigated by anti-FN and RGD peptide. In comparison with monolayer cells, up-regulated α3β1, α4β1 and α5β1 expression were detected in MCA while treatment with FN in both cells.

Conclusions:

OVCAR-3 and SKOV3 cells had varying dynamic formation of MCA in our experimental system. FN enhanced MCA formation in both cells, which was associated with increased expression of 3β1, α4β1 and α5β1 in the MCA. Therefore, FN and these integrins may be new therapeutic targets for intervention of ovarian cancer metastasis.

Multicellular spheroid based on a triple co-culture: A novel 3D model to mimic pancreatic tumor complexity

The preclinical drug screening of pancreatic cancer treatments suffers from the absence of appropriate models capable to reproduce in vitro the heterogeneous tumor microenvironment and its stiff desmoplasia. Driven by this pressing need, we describe in this paper the conception and the characterization of a novel 3D tumor model consisting of a triple co-culture of pancreatic cancer cells (PANC-1), fibroblasts (MRC-5) and endothelial cells (HUVEC), which assembled to form a hetero-type multicellular tumor spheroid (MCTS). By histological analyses and Selective Plain Illumination Microscopy (SPIM) we have monitored the spatial distribution of each cell type and the evolution of the spheroid composition. Results revealed the presence of a core rich in fibroblasts and fibronectin in which endothelial cells were homogeneously distributed. The integration of the three cell types enabled to reproduce in vitro with fidelity the influence of the surrounding environment on the sensitivity of cancer cells to chemotherapy. To our knowledge, this is the first time that a scaffold-free pancreatic cancer spheroid model combining both tumor and multiple stromal components has been designed. It holds the possibility to become an advantageous tool for a pertinent assessment of the efficacy of various therapeutic strategies.

STATEMENT OF SIGNIFICANCE

Pancreatic tumor microenvironment is characterized by abundant fibrosis and aberrant vasculature. Aiming to reproduce in vitro these features, cancer cells have been already co-cultured with fibroblasts or endothelial cells separately but the integration of both these essential components of the pancreatic tumor microenvironment in a unique system, although urgently needed, was still missing. In this study, we successfully integrated cellular and acellular microenvironment components (i.e., fibroblasts, endothelial cells, fibronectin) in a hetero-type scaffold-free multicellular tumor spheroid. This new 3D triple co-culture model closely mimicked the resistance to treatments observed in vivo, resulting in a reduction of cancer cell sensitivity to the anticancer treatment.

Extracellular matrix scaffold and hydrogel derived from decellularized and delipidized human pancreas

Extracellular matrix (ECM) plays an important developmental role by regulating cell behaviour through structural and biochemical stimulation. Tissue-specific ECM, attained through decellularization, has been proposed in several strategies for tissue and organ replacement. Decellularization of animal pancreata has been reported, but the same methods applied to human pancreas are less effective due to higher lipid content. Moreover, ECM-derived hydrogels can be obtained from many decellularized tissues, but methods have not been reported to obtain human pancreas-derived hydrogel. Using novel decellularization methods with human pancreas we produced an acellular, 3D biological scaffold (hP-ECM) and hydrogel (hP-HG) amenable to tissue culture, transplantation and proteomic applications. The inclusion of a homogenization step in the decellularization protocol significantly improved lipid removal and gelation capability of the resulting ECM, which was capable of gelation at 37 °C in vitro and in vivo, and is cytocompatible with a variety of cell types and islet-like tissues in vitro. Overall, this study demonstrates the characterisation of a novel protocol for the decellularization and delipidization of human pancreatic tissue for the production of acellular ECM and ECM hydrogel suitable for cell culture and transplantation applications. We also report a list of 120 proteins present within the human pancreatic matrisome.

Time-dependent changes in extra-domain A-fibronectin concentration and relative amounts of fibronectin-fibrin complexes in plasma of patients with peripheral arterial disease after endovascular revascularisation

Fibronectin (FN) may be involved in time- and stage-dependent and inter-related controlled processes of inflammation, coagulation, and wound healing accompanying peripheral arterial disease (PAD). In the present study, FN and FN-containing extra-domain A (EDA-FN), macromolecular FN-fibrin complexes, and FN monomer were analysed in the plasma of 142 PAD patients, including 37 patients with restenosis, for 37 months after revascularisation. FN concentration increased significantly in the plasma of PAD patients within 7 to 12 months after revascularisation, whereas the high concentration of EDA-FN was maintained up to 24 months, significantly higher in the group 7 to 12 months after revascularisation with recurrence of stenosis and lower in the PAD groups 1 to 3 months and 4 to 6 months after revascularisation with comorbid diabetes and ulceration, respectively. The relative amounts of FN-fibrin complexes up to 1600 kDa and FN monomer were significantly higher, within intervals of 4 to 24 months and 4 to 6 months after revascularisation, respectively. Moreover, the relative amounts of 750 to 1600 kDa FN-fibrin complexes within 13 to 24 months after revascularisation were higher in comparison with those in the group without restenosis. In conclusion, high levels of EDA-FN and FN-fibrin complexes could have potential diagnostic value in the management of PAD patients after revascularisation, predicting restenosis risk.

Serum exosomal protein profiling for the non-invasive detection of cardiac allograft rejection

BACKGROUND

Exosomes are cell-derived circulating vesicles that play an important role in cell-cell communication. Exosomes are actively assembled and carry messenger RNAs, microRNAs and proteins. The "gold standard" for cardiac allograft surveillance is endomyocardial biopsy (EMB), an invasive technique with a distinct complication profile. The development of novel, non-invasive methods for the early diagnosis of allograft rejection is warranted. We hypothesized that the exosomal proteome is altered in acute rejection, allowing for a distinction between non-rejection and rejection episodes.

METHODS

Serum samples were collected from heart transplant (HTx) recipients with no rejection, acute cellular rejection (ACR) and antibody-mediated rejection (AMR). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of serum exosome was performed using a mass spectrometer (Orbitrap Fusion Tribrid).

RESULTS

Principal component analysis (PCA) revealed a clustering of 3 groups: (1) control and heart failure (HF); (2) HTx without rejection; and (3) ACR and AMR. A total of 45 proteins were identified that could distinguish between groups (q < 0.05). Comparison of serum exosomal proteins from control, HF and non-rejection HTx revealed 17 differentially expressed proteins in at least 1 group (q < 0.05). Finally, comparisons of non-rejection HTx, ACR and AMR serum exosomes revealed 15 differentially expressed proteins in at least 1 group (q < 0.05). Of these 15 proteins, 8 proteins are known to play a role in the immune response. Of note, the majority of proteins identified were associated with complement activation, adaptive immunity such as immunoglobulin components and coagulation.

CONCLUSIONS

Characterizing of circulating exosomal proteome in different cardiac disease states reveals unique protein expression patterns indicative of the respective pathologies. Our data suggest that HTx and allograft rejection alter the circulating exosomal protein content. Exosomal protein analysis could be a novel approach to detect and monitor acute transplant rejection and lead to the development of predictive and prognostic biomarkers.

Synergistic effects of fibronectin and bone morphogenetic protein on the bioactivity of titanium metal

To improve the biological properties of bioactive titanium metal, recombinant human bone morphogenetic protein 2(rhBMP-2) and fibronectin (Fn) were adsorbed on its surface solely or contiguously to modify the anodic oxidized titanium (AO-Ti), acid-alkali-treated titanium (AA-Ti), and polished titanium (P-Ti). It is found that the different bioactive titanium surface structures had great influence on protein adsorption. The adsorption amounts of BMP adsorbed solely and Fn/BMP adsorbed contiguously were AA-Ti > P-Ti > AO-Ti, and that for Fn adsorbed solely was AA-Ti ≈ P-Ti > AO-Ti. The conformation of proteins was changed remarkably after the adsorption. For BMP, the α-helix decreased on AA-Ti and stabilized on P-Ti and AO-Ti. For Fn, the β-sheet on PT-Ti and AA-Ti increased significantly. For Fn/BMP, the percentage of β-sheet on AA-Ti increased, and that of α-helix on all samples was stable. MSCs showed greater adhesion and spreading on Fn/BMP groups. MTT and Elisa tests showed that the synergistic effects of proteins made the cells proliferate and differentiate faster. It indicated both the surface structure and the synergistic effects of proteins could influence the biological properties of titanium metals. It provides research foundation for improving the biological properties of bioactive titanium metals by simultaneous application of several proteins. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2485-2498, 2017.

The miR-181d-regulated metalloproteinase Adamts1 enzymatically impairs adipogenesis via ECM remodeling

The extracellular matrix (ECM) maintenance is crucial to the structural integrity of adipocytes and whole adipose tissue formation. However, the potential impact of the ECM on adipocyte lineage commitment is unclear. Herein, we demonstrate that forced expression of matrix-associated metalloproteinase Adamts1 (a disintegrin and metalloproteinase with thrombospondin motifs 1), which we show is targeted by microRNA-181d (miR-181d) during BMP4-induced adipocytic lineage commitment, markedly impairs adipocyte commitment. Conversely, siRNA-induced inhibition of Adamts1 promotes adipocyte commitment. Adamst1 metalloprotease activity is required for this inhibition and is determined to function via remodeling ECM components followed by activating FAK-ERK signaling pathway during the commitment process. Furthermore, ablation of Adamts1 in adipose tissue increases adipose tissue mass, reduces insulin sensitivity, and disrupts lipid homeostasis. This finding is consistent with Adamts1 decreased expression in the adipose tissue of obese mice and an inverse correlation of Adamts1 expression with body mass index in humans. Collectively, our results indicate that Adamts1 acts as an ECM 'modifier', with miR-181d-induced downregulation, that regulates adipocyte lineage commitment and obesity.

Spatiotemporal distribution of extracellular matrix changes during mouse duodenojejunal flexure formation

Although gut flexures characterize gut morphology, the mechanisms underlying flexure formation remain obscure. Previously, we analyzed the mouse duodenojejunal flexure (DJF) as a model for its formation and reported asymmetric morphologies between the inner and outer bending sides of the fetal mouse DJF, implying their contribution to DJF formation. We now present the extracellular matrix (ECM) as an important factor for gut morphogenesis. We investigate ECM distribution during mouse DJF formation by histological techniques. In the intercellular space of the gut wall, high Alcian-Blue positivity for proteoglycans shifted from the outer to the inner side of the gut wall during DJF formation. Immunopositivity for fibronectin, collagen I, or pan-tenascin was higher at the inner than at the outer side. Collagen IV and laminins localized to the epithelial basement membrane. Beneath the mesothelium at the pre-formation stage, collagen IV and laminin immunopositivity showed inverse results, corresponding to the different cellular characteristics at this site. At the post-formation stage, however, laminin positivity beneath the mesothelium was the reverse of that observed during the pre-formation stage. High immunopositivity for collagen IV and laminins at the inner gut wall mesenchyme of the post-formation DJF implied a different blood vessel distribution. We conclude that ECM distribution changes spatiotemporally during mouse DJF formation, indicating ECM association with the establishment of asymmetric morphologies during this process.

Temporal lobe in human aging: A quantitative protein profiling study of samples from Chinese Human Brain Bank

The temporal lobe is a portion of the cerebral cortex with critical functionality. The age-related protein profile changes in the human temporal lobe have not been previously studied. This 4-plex tandem mass tag labeled proteomic study was performed on samples of temporal lobe from Chinese donors. Tissue samples were assigned to four age groups: Group A (the young, age: 34±13 years); Group B (the elderly, 62±5 years); Group C (the aged, 84±4 years) and Group D (the old, 95±1 years). Pooled samples from the different groups were subjected to proteomics and bioinformatics analysis to identify age-related changes in protein expression and associated pathways. We isolated 5072 proteins, and found that 67 proteins were downregulated and 109 proteins were upregulated in one or more groups during the aging process. Western blotting assays were performed to verify the proteomic results. Bioinformatic analysis identified proteins involved in neuronal degeneration, including proteins involved in neuronal firing, myelin sheath damage, and cell structure stability. We also observed the accumulation of extracellular matrix and lysosomal proteins which imply the occurrence of fibrosis and autophagy. Our results suggest a series of changes across a wide range of proteins in the human temporal lobe that may relate to aging and age-related neurodegenerative disorders.

Effect of the triterpene 3β, 6β, 16β-trihydroxylup-20(29)-ene isolated from the leaves of Combretum leprosum Mart. on cutaneous wounds in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Combretum leprosum Mart. is a native species of the Caatinga, an important biome in the Brazilian semi-arid region. This species is commonly used in Brazil as a healing agent, as well as for the treatment of skin diseases.

AIM OF THE STUDY

This study investigated the healing potential of the ethanolic extract (EECL) and the bioactive triterpene 3β, 6β, 16β-trihydroxylup-20 (29)-ene (CLF-1) isolated from the leaves of C. leprosum.

MATERIALS AND METHODS

Skin wounds (1cm(2)) were created in the dorsal zone of mice with a scalpel blade number 15. The treatment consisted in a daily topical application of 100 μl of 150 mM NaCl, EECL and CLF-1 (at 10 μg/100 μl) for 12 days. The lesions were then macro and microscopically evaluated.

RESULTS

On postoperative day (POD) 2, the lesions treated with EECL and CLF-1 showed a moderate presence of vessels of the granulation tissue progressing in the dermis. The same effect was not observed in the control group. The treatment with EECL and CLF-1 stimulated angiogenesis, resulting in a rapid deposition of extracellular matrix (ECM). Moreover, the animals treated with EECL and CLF-1 showed smaller lesions on POD 7, primarily due to the contraction in the reticular dermis induced by organization of myofibroblasts, which was not observed in the group treated with NaCl. In addition, the lesions treated with EECL and CLF-1 showed ECM restructuration and presence of epithelium coating, which was not observed in the group treated with NaCl, in which the lesions showed no epithelial lining, suggesting delayed healing.

CONCLUSION

CLF-1 isolated from the leaves of C. leprosum may be considered to be an important molecule for the treatment of skin lesions. However, further investigations are necessary to establish its role in chronic lesions and to elucidate the mechanism of action involved in the cutaneous healing process. To the best of our knowledge, this is the first report describing the pro-healing activity of the ethanolic extract and the triterpene 3β, 6β, 16β-trihydroxylup-20(29)-ene isolated from leaves of C. leprosum.

A potential role for endogenous proteins as sacrificial sunscreens and antioxidants in human tissues

Excessive ultraviolet radiation (UVR) exposure of the skin is associated with adverse clinical outcomes. Although both exogenous sunscreens and endogenous tissue components (including melanins and tryptophan-derived compounds) reduce UVR penetration, the role of endogenous proteins in absorbing environmental UV wavelengths is poorly defined. Having previously demonstrated that proteins which are rich in UVR-absorbing amino acid residues are readily degraded by broadband UVB-radiation (containing UVA, UVB and UVC wavelengths) here we hypothesised that UV chromophore (Cys, Trp and Tyr) content can predict the susceptibility of structural proteins in skin and the eye to damage by physiologically relevant doses (up to 15.4 J/cm²) of solar UVR (95% UVA, 5% UVB). We show that: i) purified suspensions of UV-chromophore-rich fibronectin dimers, fibrillin microfibrils and β- and γ-lens crystallins undergo solar simulated radiation (SSR)-induced aggregation and/or decomposition and ii) exposure to identical doses of SSR has minimal effect on the size or ultrastructure of UV chromophore-poor tropoelastin, collagen I, collagen VI microfibrils and α-crystallin. If UV chromophore content is a factor in determining protein stability in vivo, we would expect that the tissue distribution of Cys, Trp and Tyr-rich proteins would correlate with regional UVR exposure. From bioinformatic analysis of 244 key structural proteins we identified several biochemically distinct, yet UV chromophore-rich, protein families. The majority of these putative UV-absorbing proteins (including the late cornified envelope proteins, keratin associated proteins, elastic fibre-associated components and β- and γ-crystallins) are localised and/or particularly abundant in tissues that are exposed to the highest doses of environmental UVR, specifically the stratum corneum, hair, papillary dermis and lens. We therefore propose that UV chromophore-rich proteins are localised in regions of high UVR exposure as a consequence of an evolutionary pressure to express sacrificial protein sunscreens which reduce UVR penetration and hence mitigate tissue damage.

Major structural proteins such as collagen I and tropoelastin are UVA-resistant.

In contrast, proteins which are rich in Cys, Trp and Tyr residues are UV-susceptible.

These proteins are concentrated in UV exposed tissues.

UV-chromophore (Cys, Trp, Tyr)-rich proteins may act as endogenous sunscreens.

Identification of soluble supramolecular FN-fibrin complexes in human plasma

SDS-agarose FN immunoblotting of 257 normal and pathological human plasma samples revealed the ladder pattern of multiple plasma FN bands which corresponded to FN monomer and dimer, and 5 FN-fibrin bands with increasing molecular masses. The FN-fibrin bands of about 750 kDa, 1000 kDa, 1300 kDa, 1600 kDa, and 1900 kDa appeared more frequently and in significantly higher relative amounts in the pathological samples (P < 0.000) than in relatively healthy individuals. The revealing of high-molecular FN-fibrin complexes by SDS-agarose FN immunobloting might have the potential to become a laboratory biomarker of some diseases in which the coagulation system is triggered.

Biomimetic collagen I and IV double layer Langmuir-Schaefer films as microenvironment for human pluripotent stem cell derived retinal pigment epithelial cells

The environmental cues received by the cells from synthetic substrates in vitro are very different from those they receive in vivo. In this study, we applied the Langmuir-Schaefer (LS) deposition, a variant of Langmuir-Blodgett technique, to fabricate a biomimetic microenvironment mimicking the structure and organization of native Bruch's membrane for the production of the functional human embryonic stem cell derived retinal pigment epithelial (hESC-RPE) cells. Surface pressure-area isotherms were measured simultaneously with Brewster angle microscopy to investigate the self-assembly of human collagens type I and IV on air-subphase interface. Furthermore, the structure of the prepared collagen LS films was characterized with scanning electron microscopy, atomic force microscopy, surface plasmon resonance measurements and immunofluorescent staining. The integrity of hESC-RPE on double layer LS films was investigated by measuring transepithelial resistance and permeability of small molecular weight substance. Maturation and functionality of hESC-RPE cells on double layer collagen LS films was further assessed by RPE-specific gene and protein expression, growth factor secretion, and phagocytic activity. Here, we demonstrated that the prepared collagen LS films have layered structure with oriented fibers corresponding to architecture of the uppermost layers of Bruch's membrane and result in increased barrier properties and functionality of hESC-RPE cells as compared to the commonly used dip-coated controls.

Peptide therapies for ocular surface disturbances based on fibronectin-integrin interactions

The condition of the corneal epithelium is a critical determinant of corneal transparency and clear vision. The corneal epithelium serves as a barrier to protect the eye from external insults, with its smooth surface being essential for its optical properties. Disorders of the corneal epithelium include superficial punctate keratopathy, corneal erosion, and persistent epithelial defects (PEDs). The prompt resolution of these disorders is important for minimization of further damage to the cornea. Currently available treatment modalities for corneal epithelial disorders are based on protection of the ocular surface in order to allow natural healing to proceed. PEDs remain among the most difficult corneal conditions to treat, however. On the basis of characterization of the pathobiology of PEDs at the cell and molecular biological levels, we have strived to develop new modes of treatment for these defects. These treatments rely on two key concepts: provision of a substrate, such as the adhesive glycoprotein fibronectin, for the attachment and migration of corneal epithelial cells, and activation of these cells by biological agents such as the combination of substance P and insulin-like growth factor-1 (IGF-1). Central to both approaches is the role of the fibronectin-integrin system in corneal epithelial wound healing. Determination of the minimum amino acid sequences required for the promotion of corneal epithelial wound closure by fibronectin (PHSRN) and by substance P (FGLM-amide) plus IGF-1 (SSSR) has led to the development of peptide eyedrops for the treatment of PEDs that are free of adverse effects of the parent molecules.

Integrins αvβ6, α6β4 and α3β1 are down-regulated in cholangiolocellular carcinoma but not cholangiocarcinoma

AIM

The aim of this study was to evaluate integrin expression and immunolocalization of the extracellular matrix proteins in cholangiolocellular carcinoma (CoCC).

METHODS

Tissue specimens of 23 CoCC, 28 cholangiocarcinomas (CCC), 42 hepatocellular carcinomas (HCC) and 11 classical type combined hepatocellular cholangiocarcinomas (CHC) were immunostained for β6, β4 and α3 integrins, fibronectin and laminin. ITGB6, B4 and A3 mRNA levels in six HCC cell lines, five CCC cell lines and two CHC cell lines were quantified by quantitative reverse transcription polymerase chain reaction.

RESULTS

Little or no positivity for β6, β4 and α3 integrins was shown in 91%, 91% and 52% of CoCC and 100%, 98% and 81% of HCC, respectively, according to immunostaining, whereas intense positive staining for these integrins was demonstrated in 64%, 96% and 75% of CCC, respectively. There was a close correlation between β4 and α3 integrin expression and intracytoplasmic laminin in CoCC, CCC and HCC, but not between β6 expression and its ligand, fibronectin. Integrin mRNA levels were increased in four of five CCC cell lines, but nearly undetectable in five of six HCC cell lines and one CHC cell line. Tubular differentiation of a CHC cell line cultured in collagen gel matrix induced upregulation of these integrins.

CONCLUSION

Our results first indicated downregulation of αvβ6, α6β4 and α3β1 integrins in CoCC, in contrast to its high expression in CCC, suggesting a diagnostic value of integrins in the differential diagnosis of CoCC and CCC, as well as a useful inducible marker of the intermediate features of CoCC.

Damage to skin extracellular matrix induced by UV exposure

SIGNIFICANCE

Chronic exposure to environmental ultraviolet radiation (UVR) plays a key role in both photocarcinogenesis and induction of accelerated skin aging. Although the spatiotemporal consequences of UVR exposure for the composition and architecture of the dermal extracellular matrix (ECM) are well characterized, the pathogenesis of photoaging remains poorly defined. Given the compelling evidence for the role of reactive oxygen species (ROS) as mediators of photoaging, UVR-exposed human skin may be an accessible model system in which to characterize the role of oxidative damage in both internal and external tissues.

RECENT ADVANCES

Although the cell-mediated degradation of dermal components via UVR-induced expression of ECM proteases has long been identified as an integral part of the photoaging pathway, the relative importance and identity of cellular and extracellular photosensitizers (direct hit and bystanders models, respectively) in initiating this enzymatic activity is unclear. Recently, both age-related protein glycation and relative amino-acid composition have been identified as potential risk factors for photo-ionization and/or photo-sensitization. Here, we propose a selective multi-hit model of photoaging.

CRITICAL ISSUES

Bioinformatic analyses can be employed to identify candidate UVR targets/photosensitizers, but the action of UVR on protein structure and/or ROS production should be verified experimentally. Crucially, in the case of biochemically active ECM components such as fibronectin and fibrillin, the downstream effects of photo-degradation on tissue homeostasis remain to be confirmed.

FUTURE DIRECTIONS

Both topical antioxidants and inhibitors of detrimental cell signaling may be effective in abrogating the effects of specific UVR-mediated protein degradation in the dermis.

Oligophrenin-1 is associated with cell adhesion and migration in prostate cancer

OBJECTIVE

We performed Escherichia coli ampicillin secretion trap (CAST) analysis in prostate cancer (PCa) to identify novel biomarkers. We show here that OPHN1, which encodes oligophrenin-1 protein, is upregulated in PCa. OPHN1 was first determined to be one of the genes associated with X-linked mental retardation; however, neither the gene's function nor the link between its expression and survival of patients has been investigated.

METHODS

We investigate the expression of oligophrenin-1 in 141 PCa tissue samples by immunohistochemistry and perform functional analysis using RNA interference.

RESULTS

Immunohistochemical analysis of oligophrenin-1 demonstrated that 60 (43%) PCa cases were positive for oligophrenin-1. Positive oligophrenin-1 expression was significantly correlated with a high Gleason score (p = 0.0198). Furthermore, patients with oligophrenin-1-positive PCa had a worse biochemical recurrence-free survival rate than patients with oligophrenin-1-negative PCa (p = 0.0079). Cell adhesion to fibronectin was significantly reduced in OPHN1 small interfering (si)RNA-transfected LNCaP and PC3 cells in comparison to negative-control siRNA-transfected cells. Knockdown of OPHN1 reduced the expression of ITGA5 and stress fiber formation in LNCaP and PC3 cells.

CONCLUSION

These results suggest that oligophrenin-1 is involved in tumor progression in PCa.

A quantitative proteomic approach to identify significantly altered protein networks in the serum of patients with lymphangioleiomyomatosis (LAM)

Lymphangioleiomyomatosis (LAM) is a rare and progressive cystic lung condition affecting approximately 3.4–7.5/million women, with an average lag time between symptom onset and diagnosis of upwards of 4 years. The aim of this work was to identify altered proteins in LAM serum which may be potential biomarkers of disease. Serum from LAM patient volunteers and healthy control volunteers were pooled and analysis carried out using quantitative 4-plex iTRAQ technology. Differentially expressed proteins were validated using ELISAs and pathway analysis was carried out using Ingenuity Pathway Analysis. Fourteen proteins were differentially expressed in LAM serum compared to control serum (p<0.05). Further screening validated the observed differences in extracellular matrix remodelling proteins including fibronectin (30% decrease in LAM, p = 0.03), von Willebrand Factor (40% reduction in LAM, p = 0.03) and Kallikrein III (25% increase in LAM, p = 0.03). Pathway networks elucidated the relationships between the ECM and cell trafficking in LAM. This study was the first to highlight an imbalance in networks important for remodelling in LAM, providing a set of novel potential biomarkers. These understandings may lead to a new effective treatment for LAM in the future.

SB-273005, an antagonist of αvβ3 integrin, reduces the production of Th2 cells and cytokine IL-10 in pregnant mice

Pregnancy is associated with complex immunoreactions. In the present study, the effect of SB-273005, an antagonist of αvβ3 integrin, on the alterations of T helper (Th) cells and their derived cytokines that occur during pregnancy was investigated in mice. Five non-pregnant mice were used as a negative control. Mice were impregnated by co-housing females and males at a ratio of 2:1 overnight and pregnancy was confirmed by the appearance of vaginal plugs the following morning. Day 1 (D1) pregnant mice were randomly divided into two groups (n=20) and were administered either dimethylsulfoxide (mock treatment) or SB-273005 (3 mg/kg) by gavage at D3, D4 and D5. At D8, the levels of Th1 and Th2 cells and interleukin (IL)-2 and IL-10 in the spleen and peripheral blood were determined using flow cytometry and enzyme-linked immunosorbent assay. Pregnancy significantly increased the ratio of Th2:Th1 cells in the spleen compared with that in non-pregnant mice (P<0.01). However, this increase was significantly reduced by SB-273005 (P<0.001). Furthermore, whilst pregnancy decreased Th1 cell-produced IL-2 levels and increased Th2 cell-derived IL-10 levels, SB-273005 reversed both processes (P<0.05 for IL-2; P<0.01 for IL-10). The results from the present study demonstrated that pregnancy induces changes in the spleen, including a reduction of IL-2 and an increase in IL-10 production by Th1 and Th2 cells, respectively, as well as an upregulation of the Th2:Th1 ratio in the spleen. These immunological changes are reversed by SB-273005, indicating an important role for αvβ3 integrin in mediating these immunological alterations.

Structure and barrier properties of human embryonic stem cell-derived retinal pigment epithelial cells are affected by extracellular matrix protein coating

Extracellular matrix (ECM) interactions play a vital role in cell morphology, migration, proliferation, and differentiation of cells. We investigated the role of ECM proteins on the structure and function of human embryonic stem cell-derived retinal pigment epithelial (hESC-RPE) cells during their differentiation and maturation from hESCs into RPE cells in adherent differentiation cultures on several human ECM proteins found in native human Bruch's membrane, namely, collagen I, collagen IV, laminin, fibronectin, and vitronectin, as well as on commercial substrates of xeno-free CELLstart™ and Matrigel™. Cell pigmentation, expression of RPE-specific proteins, fine structure, as well as the production of basal lamina by hESC-RPE on different protein coatings were evaluated after 140 days of differentiation. The integrity of hESC-RPE epithelium and barrier properties on different coatings were investigated by measuring transepithelial resistance. All coatings supported the differentiation of hESC-RPE cells as demonstrated by early onset of cell pigmentation and further maturation to RPE monolayers after enrichment. Mature RPE phenotype was verified by RPE-specific gene and protein expression, correct epithelial polarization, and phagocytic activity. Significant differences were found in the degree of RPE cell pigmentation and tightness of epithelial barrier between different coatings. Further, the thickness of self-assembled basal lamina and secretion of the key ECM proteins found in the basement membrane of the native RPE varied between hESC-RPE cultured on compared protein coatings. In conclusion, this study shows that the cell culture substrate has a major effect on the structure and basal lamina production during the differentiation and maturation of hESC-RPE potentially influencing the success of cell integrations and survival after cell transplantation.

Fibronectin is deposited by injury-activated epicardial cells and is necessary for zebrafish heart regeneration

Unlike adult mammals, adult zebrafish vigorously regenerate lost heart muscle in response to injury. The epicardium, a mesothelial cell layer enveloping the myocardium, is activated to proliferate after cardiac injury and can contribute vascular support cells or provide mitogens to regenerating muscle. Here, we applied proteomics to identify secreted proteins that are associated with heart regeneration. We found that Fibronectin, a main component of the extracellular matrix, is induced and deposited after cardiac damage. In situ hybridization and transgenic reporter analyses indicated that expression of two fibronectin paralogues, fn1 and fn1b, are induced by injury in epicardial cells, while the itgb3 receptor is induced in cardiomyocytes near the injury site. fn1, the more dynamic of these paralogs, is induced chamber-wide within one day of injury before localizing epicardial Fn1 synthesis to the injury site. fn1 loss-of-function mutations disrupted zebrafish heart regeneration, as did induced expression of a dominant-negative Fibronectin cassette, defects that were not attributable to direct inhibition of cardiomyocyte proliferation. These findings reveal a new role for the epicardium in establishing an extracellular environment that supports heart regeneration.

Increase of O-glycosylated oncofetal fibronectin in high glucose-induced epithelial-mesenchymal transition of cultured human epithelial cells

Growing evidences indicate that aberrant glycosylation can modulate tumor cell invasion and metastasis. The process termed "epithelial-mesenchymal transition" (EMT) provides a basic experimental model to shed light on this complex process. The EMT involves a striking decline in epithelial markers, accompanied by enhanced expression of mesenchymal markers, culminating in cell morphology change and increased cell motility. Few recent studies have established the participation glycosylation during EMT. Studies now come into knowledge brought to light the involvement of a site-specific O-glycosylation in the IIICS domain of human oncofetal fibronectin (onfFN) during the EMT process. Herein we show that high glucose induces EMT in A549 cells as demonstrated by TGF-β secretion, cell morphology changes, increased cellular motility and the emergence of mesenchymal markers. The hyperglycemic conditions increased onfFN protein levels, promoted an up regulation of mRNA levels for ppGalNAc-T6 and FN IIICS domain, which contain the hexapeptide (VTHPGY) required for onfFN biosynthesis. Glucose effect involves hexosamine (HBP) biosynthetic pathway as overexpression of glutamine: fructose-6-phosphate amidotransferase increases mesenchymal markers, onfFN levels and mRNA levels for FN IIICS domain. In summary, our results demonstrate, for the first time that the metabolism of glucose through HBP promotes O-glycosylation of the oncofetal form of FN during EMT modulating tumorogenesis.

Alterations in molecular status of plasma fibronectin associated with aging of normal human individuals

OBJECTIVES

Senescence, progressive deterioration of many bodily functions might be associated with age-dependent alterations of plasma fibronectin (FN) molecular status (i.e., domain, glycotope, and molecular form expressions).

DESIGN AND METHODS

FN molecular status was analyzed in 127 plasma samples of healthy individuals in groups of newborns, and subjects aged 3-14, 15-39, 41-59, and 60-82 years by FN-ELISA, lectin-FN-ELISA, and immunoblotting using a set of domain-specific monoclonal antibodies, specific lectins, and monoclonal antibody to FN, respectively.

RESULTS

During the first four decades of human life the levels of cell-binding-, carboxyl-terminal-, collagen-, heparin-, and fibrin-domains of plasma FN gradually increased. In subjects aged up to 82 years the cell-binding and carboxyl-terminal FN domain concentrations did not change, while the heparin, fibrin, and collagen domains significantly increased. The relative reactivity of plasma FN with Maackia amurensis lectin, specific to α2,3-linked sialic acid, significantly decreased after birth, reaching a stable level in the subsequent life period, whereas with Sambucus nigra lectin, specific to α2,6-linked sialic acid, it significantly decreased in the 60-82 year old group. Moreover, the appearance of 280-kDa and 320-kDa FN bands, absent in young and mature healthy individuals, was found in the groups of 41-59 and 60-82 year olds.

CONCLUSIONS

The alterations of FN molecular status throughout growth, maturation and senescence might be associated not only with disturbances in the balance of FN production rate and degradation, but concomitantly with conformational rearrangements of FN and its engagement in age-related vascular remodeling processes.

Danger-associated molecular patterns (DAMPs) in acute lung injury

Danger-associated molecular patterns (DAMPs) are host-derived molecules that can function to regulate the activation of pathogen recognition receptors (PRRs). These molecules play a critical role in modulating the lung injury response. DAMPs originate from multiple sources, including injured and dying cells, the extracellular matrix, or exist as immunomodulatory proteins within the airspace and interstitium. DAMPs can function as either toll-like receptor (TLR) agonists or antagonists, and can modulate both TLR and nod-like receptor (NLR) signalling cascades. Collectively, this diverse group of molecules may represent important therapeutic targets in the prevention and/or treatment of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS).

Extracellular Matrix is an Important Component of Limbal Stem Cell Niche

Extracellular matrix plays an important role in stem cell niche which maintains the undifferentiated stem cell phenotype. Human corneal epithelial stem cells are presumed to reside mainly at the limbal basal epithelium. Efforts have been made to characterize different components of the extracellular matrix that are preferentially expressed at the limbus. Mounting evidence from experimental data suggest that these components are part of the stem cell niche and play a role in the homeostasis of limbal stem cells. The extracellular matrix provides a mechanical and structural support as well as regulates cellular functions such as adhesion, migration, proliferation, self-renewal and differentiation. Optimization of the extracellular matrix components might be able to recreate an ex vivo stem cell niche to expand limbal stem cells.