Evolution of collagen-based adhesion systems

Renal proximal tubule-on-a-chip in PDMS: fabrication, functionalization, and RPTEC:HUVEC co-culture evaluation

'On-a-chip' technology advances the development of physiologically relevant organ-mimicking architecture by integrating human cells into three-dimensional microfluidic devices. This method also establishes discrete functional units, faciliting focused research on specific organ components. In this study, we detail the development and assessment of a convoluted renal proximal tubule-on-a-chip (PT-on-a-chip). This platform involves co-culturing Renal Proximal Tubule Epithelial Cells (RPTEC) and Human Umbilical Vein Endothelial Cells (HUVEC) within a polydimethylsiloxane microfluidic device, crafted through a combination of 3D printing and molding techniques. Our PT-on-a-chip significantly reduced high glucose level, exhibited albumin uptake, and simulated tubulopathy induced by amphotericin B. Remarkably, the RPTEC:HUVEC co-culture exhibited efficient cell adhesion within 30 min on microchannels functionalized with plasma, 3-aminopropyltriethoxysilane, and type-I collagen. This approach significantly reduced the required incubation time for medium perfusion. In comparison, alternative methods such as plasma and plasma plus polyvinyl alcohol were only effective in promoting cell attachment to flat surfaces. The PT-on-a-chip holds great promise as a valuable tool for assessing the nephrotoxic potential of new drug candidates, enhancing our understanding of drug interactions with co-cultured renal cells, and reducing the need for animal experimentation, promoting the safe and ethical development of new pharmaceuticals.

Evo-Devo Mechanobiology: The Missing Link

While the modern framework of evolutionary development (evo-devo) has been decidedly genetic, historic analyses have also considered the importance of mechanics in the evolution of form. With the aid of recent technological advancements in both quantifying and perturbing changes in the molecular and mechanical effectors of organismal shape, how molecular and genetic cues regulate the biophysical aspects of morphogenesis is becoming increasingly well studied. As a result, this is an opportune time to consider how the tissue-scale mechanics that underlie morphogenesis are acted upon through evolution to establish morphological diversity. Such a focus will enable a field of evo-devo mechanobiology that will serve to better elucidate the opaque relations between genes and forms by articulating intermediary physical mechanisms. Here, we review how the evolution of shape is measured and related to genetics, how recent strides have been made in the dissection of developmental tissue mechanics, and how we expect these areas to coalesce in evo-devo studies in the future.

Extracellular matrix stiffness-The central cue for skin fibrosis

Skin fibrosis is a physiopathological process featuring the excessive deposition of extracellular matrix (ECM), which is the main architecture that provides structural support and constitutes the microenvironment for various cellular behaviors. Recently, increasing interest has been drawn to the relationship between the mechanical properties of the ECM and the initiation and modulation of skin fibrosis, with the engagement of a complex network of signaling pathways, the activation of mechanosensitive proteins, and changes in immunoregulation and metabolism. Simultaneous with the progression of skin fibrosis, the stiffness of ECM increases, which in turn perturbs mechanical and humoral homeostasis to drive cell fate toward an outcome that maintains and enhances the fibrosis process, thus forming a pro-fibrotic "positive feedback loop". In this review, we highlighted the central role of the ECM and its dynamic changes at both the molecular and cellular levels in skin fibrosis. We paid special attention to signaling pathways regulated by mechanical cues in ECM remodeling. We also systematically summarized antifibrotic interventions targeting the ECM, hopefully enlightening new strategies for fibrotic diseases.

The Role of Extracellular Matrix Proteins in Breast Cancer

The extracellular matrix is a structure composed of many molecules, including fibrillar (types I, II, III, V, XI, XXIV, XXVII) and non-fibrillar collagens (mainly basement membrane collagens: types IV, VIII, X), non-collagenous glycoproteins (elastin, laminin, fibronectin, thrombospondin, tenascin, osteopontin, osteonectin, entactin, periostin) embedded in a gel of negatively charged water-retaining glycosaminoglycans (GAGs) such as non-sulfated hyaluronic acid (HA) and sulfated GAGs which are linked to a core protein to form proteoglycans (PGs). This highly dynamic molecular network provides critical biochemical and biomechanical cues that mediate the cell–cell and cell–matrix interactions, influence cell growth, migration and differentiation and serve as a reservoir of cytokines and growth factors’ action. The breakdown of normal ECM and its replacement with tumor ECM modulate the tumor microenvironment (TME) composition and is an essential part of tumorigenesis and metastasis, acting as key driver for malignant progression. Abnormal ECM also deregulate behavior of stromal cells as well as facilitating tumor-associated angiogenesis and inflammation. Thus, the tumor matrix modulates each of the classically defined hallmarks of cancer promoting the growth, survival and invasion of the cancer. Moreover, various ECM-derived components modulate the immune response affecting T cells, tumor-associated macrophages (TAM), dendritic cells and cancer-associated fibroblasts (CAF). This review article considers the role that extracellular matrix play in breast cancer. Determining the detailed connections between the ECM and cellular processes has helped to identify novel disease markers and therapeutic targets.

Smart and Biomimetic 3D and 4D Printed Composite Hydrogels: Opportunities for Different Biomedical Applications

In recent years, smart/stimuli-responsive hydrogels have drawn tremendous attention for their varied applications, mainly in the biomedical field. These hydrogels are derived from different natural and synthetic polymers but are also composite with various organic and nano-organic fillers. The basic functions of smart hydrogels rely on their ability to change behavior; functions include mechanical, swelling, shaping, hydrophilicity, and bioactivity in response to external stimuli such as temperature, pH, magnetic field, electromagnetic radiation, and biological molecules. Depending on the final applications, smart hydrogels can be processed in different geometries and modalities to meet the complicated situations in biological media, namely, injectable hydrogels (following the sol-gel transition), colloidal nano and microgels, and three dimensional (3D) printed gel constructs. In recent decades smart hydrogels have opened a new horizon for scientists to fabricate biomimetic customized biomaterials for tissue engineering, cancer therapy, wound dressing, soft robotic actuators, and controlled release of bioactive substances/drugs. Remarkably, 4D bioprinting, a newly emerged technology/concept, aims to rationally design 3D patterned biological matrices from synthesized hydrogel-based inks with the ability to change structure under stimuli. This technology has enlarged the applicability of engineered smart hydrogels and hydrogel composites in biomedical fields. This paper aims to review stimuli-responsive hydrogels according to the kinds of external changes and t recent applications in biomedical and 4D bioprinting.

Collagen- and hyaluronic acid-based hydrogels and their biomedical applications

Hydrogels have been widely investigated in biomedical fields due to their similar physical and biochemical properties to the extracellular matrix (ECM). Collagen and hyaluronic acid (HA) are the main components of the ECM in many tissues. As a result, hydrogels prepared from collagen and HA hold inherent advantages in mimicking the structure and function of the native ECM. Numerous studies have focused on the development of collagen and HA hydrogels and their biomedical applications. In this extensive review, we provide a summary and analysis of the sources, features, and modifications of collagen and HA. Specifically, we highlight the fabrication, properties, and potential biomedical applications as well as promising commercialization of hydrogels based on these two natural polymers.

Alpha-single chains of collagen type VI inhibit the fibrogenic effects of triple helical collagen VI in hepatic stellate cells

The interaction of extracellular matrix (ECM) components with hepatic stellate cells (HSCs) is thought to perpetuate fibrosis by stimulating signaling pathways that drive HSC activation, survival and proliferation. Consequently, disrupting the interaction between ECM and HSCs is considered a therapeutical avenue although respective targets and underlying mechanisms remain to be established. Here we have interrogated the interaction between type VI collagen (CVI) and HSCs based on the observation that CVI is 10-fold upregulated during fibrosis, closely associates with HSCs in vivo and promotes cell proliferation and cell survival in cancer cell lines. We exposed primary rat HSCs and a rat hepatic stellate cell line (CFSC) to soluble CVI and determined the rate of proliferation, apoptosis and fibrogenesis in the absence of any additional growth factors. We find that CVI in nanomolar concentrations prevents serum starvation-induced apoptosis. This potent anti-apoptotic effect is accompanied by induction of proliferation and acquisition of a pronounced pro-fibrogenic phenotype characterized by increased α-smooth muscle actin, TGF-β, collagen type I and TIMP-1 expression and diminished proteolytic MMP-13 expression. The CVI-HSC interaction can be disrupted with the monomeric α2(VI) and α3(VI) chains and abrogates the activating CVI effects. Further, functional relevant α3(VI)—derived 30 amino acid peptides lead to near-complete inhibition of the CVI effect. In conclusion, CVI serves as a potent mitogen and activating factor for HSCs. The antagonistic effects of the CVI monomeric chains and peptides point to linear peptide sequences that prevent activation of CVI receptors which may allow a targeted antifibrotic therapy.

Screening of Potential Key Transcripts Involved in Planarian Regeneration and Analysis of Its Regeneration Patterns by PacBio Long-Read Sequencing

Dugesia japonica is an excellent animal model for studying the regeneration mechanism due to its characteristics of rapid regeneration and easy breeding. PacBio sequencing was performed on the intact planarians (In) and regenerating planarians of 1 day (1d), 3 days (3d), and 5 days (5d) after amputation. The aim of this study is to deeply profile the transcriptome of D. japonica and to evaluate its regenerate changes. Using robust statistical analysis, we identified 5931, 5115, and 4669 transcripts differentially expressed between 1d and In, 3d and In, 5d and In, respectively. A total of 63 key transcripts were screened from these DETs. These key transcripts enhance the expression in different regenerate stages respectively to regulate specific processes including signal transduction, mitosis, protein synthesis, transport and degradation, apoptosis, neural development, and energy cycling. Finally, according to the biological processes involved in these potential key transcripts, we propose a hypothesis of head regeneration model about D. japonica. In addition, the weighted gene co-expression network analysis provides a new way to screen key transcripts from large amounts of data. Together, these analyses identify a number of potential key regulators controlling proliferation, differentiation, apoptosis, and signal transduction. What's more, this study provides a powerful data foundation for further research on planarians regeneration.

Gene expression profiles alteration after infection of virus, bacteria, and parasite in the Olive flounder (Paralichthys olivaceus)

Olive flounder (Paralichthys olivaceus) is one of economically valuable fish species in the East Asia. In comparison with its economic importance, available genomic information of the olive flounder is very limited. The mass mortality caused by variety of pathogens (virus, bacteria and parasites) is main problem in aquaculture industry, including in olive flounder culture. In this study, we carried out transcriptome analysis using the olive flounder gill tissues after infection of three types of pathogens (Virus; Viral hemorrhagic septicemia virus, Bacteria; Streptococcus parauberis, and Parasite; Miamiensis avidus), respectively. As a result, we identified total 12,415 differentially expressed genes (DEG) from viral infection, 1,754 from bacterial infection, and 795 from parasite infection, respectively. To investigate the effects of pathogenic infection on immune response, we analyzed Gene ontology (GO) enrichment analysis with DEGs and sorted immune-related GO terms per three pathogen groups. Especially, we verified various GO terms, and genes in these terms showed down-regulated expression pattern. In addition, we identified 67 common genes (10 up-regulated and 57 down-regulated) present in three pathogen infection groups. Our goals are to provide plenty of genomic knowledge about olive flounder transcripts for further research and report genes, which were changed in their expression after specific pathogen infection.

Metabolic origin of the fused aminoacyl-tRNA synthetase, glutamyl-prolyl-tRNA synthetase

About 1 billion years ago, in a single-celled holozoan ancestor of all animals, a gene fusion of two tRNA synthetases formed the bifunctional enzyme, glutamyl-prolyl-tRNA synthetase (EPRS). We propose here that a confluence of metabolic, biochemical, and environmental factors contributed to the specific fusion of glutamyl- (ERS) and prolyl- (PRS) tRNA synthetases. To test this idea, we developed a mathematical model that centers on the precursor-product relationship of glutamic acid and proline, as well as metabolic constraints on free glutamic acid availability near the time of the fusion event. Our findings indicate that proline content increased in the proteome during the emergence of animals, thereby increasing demand for free proline. Together, these constraints contributed to a marked cellular depletion of glutamic acid and its products, with potentially catastrophic consequences. In response, an ancient organism invented an elegant solution in which genes encoding ERS and PRS fused to form EPRS, forcing coexpression of the two enzymes and preventing lethal dysregulation. The substantial evolutionary advantage of this coregulatory mechanism is evidenced by the persistence of EPRS in nearly all extant animals.

Stiffness modification of photopolymerizable gelatin-methacrylate hydrogels influences endothelial differentiation of human mesenchymal stem cells

For stem cell differentiation, the microenvironment can play an important role, and hydrogels can provide a three-dimensional microenvironment to allow native cell growth in vitro. A challenge is that the stem cell's differentiation can be influenced by the matrix stiffness. We demonstrate a low-toxicity method to create different stiffness matrices, by using a photopolymerizable gelatin methacrylate (GelMA) hydrogel cross-linked by blue light (440 nm). The stiffness and porosity of GelMA hydrogel is easily modified by altering its concentration. We used human bone marrow mesenchymal stem cells (MSCs) as a cell source and cultured the GelMA-encapsulated cells with EGM-2 medium to induce endothelial differentiation. In our GelMA blue light hydrogel system, we found that MSCs can be differentiated into both endothelial-like and osteogenic-like cells. The mRNA expressions of endothelial cell markers CD31, von Willebrand factor, vascular endothelial growth factor receptor-2, and CD34 were significantly increased in softer GelMA hydrogels (7.5% and 10%) compared with stiffer matrices (15% GelMA). On the other hand, the enhancements of osteogenic markers mRNA expressions (Alkaline phosphatase (ALP), Runx2, osteocalcin, and osteopontin) were highest in 10% GelMA. We also found that 10% GelMA hydrogel offered optimal conditions for MSCs to form capillary-like structures. These results suggest that the mechanical properties of the GelMA hydrogel can influence both endothelial and osteogenic differentiation of MSCs and sequent capillary-like formation.

About Chemical Strategies to Fabricate Cell-Instructive Biointerfaces with Static and Dynamic Complexity

Properly functioning cell-instructive biointerfaces are critical for healthy integration of biomedical devices in the body and serve as decisive tools for the advancement of our understanding of fundamental cell biological phenomena. Studies are reviewed that use covalent chemistries to fabricate cell-instructive biointerfaces. These types of biointerfaces typically result in a static presentation of predefined cell-instructive cues. Chemically defined, but dynamic cell-instructive biointerfaces introduce spatiotemporal control over cell-instructive cues and present another type of biointerface, which promises a more biomimetic way to guide cell behavior. Therefore, strategies that offer control over the lateral sorting of ligands, the availability and molecular structure of bioactive ligands, and strategies that offer the ability to induce physical, chemical and mechanical changes in situ are reviewed. Specific attention is paid to state-of-the-art studies on dynamic, cell-instructive 3D materials. Future work is expected to further deepen our understanding of molecular and cellular biological processes investigating cell-type specific responses and the translational steps toward targeted in vivo applications.

Elevated CO2 delays the early development of scleractinian coral Acropora gemmifera

The effects of elevated CO₂ on the early life stages of coral were investigated by culturing the pelagic larvae and new recruits of Acropora gemmifera at three concentrations of CO₂ (corresponding to pH = 8.1, 7.8 and 7.5, respectively). Acidified seawater resulted in fewer A. gemmifera larvae settling, and led to the production of smaller new recruits by slowing the development of the skeleton. The delayed development of new recruits due to elevated CO₂ was consistent with the downregulation of calcification related genes. Several genes related to HCO₃^- and Ca²⁺ transporters were downregulated by elevated CO₂, with solute carriers (SLC) (membrane transport proteins) possibly playing an important role. The downregulation of these membrane transport proteins might suppress the transport of calcium, bicarbonate and organic matter, resulting in the delayed development of A. gemmifera.

Isolation and characterisation of acid- and pepsin-soluble collagen from the skin of Cervus korean TEMMINCK var. mantchuricus Swinhoe

Acid-soluble collagen and pepsin-soluble collagen were extracted from the skin of deer, Cervus korean TEMMINCK var. mantchuricus Swinhoe. The two types of collagen were then characterised using sodium dodecyl sulfate–polyacrylamide gel electrophoresis, amino acid composition analysis, peptide hydrolysis patterns, thermal denaturation temperature, differential scanning calorimetry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance imaging. The yield of pepsin-soluble collagen (9.62%) was greater than that of acid-soluble collagen (2.24%), but both types of collagen showed similar electrophoretic patterns with each other and with calf skin collagen. The peptide hydrolysis pattern results suggested that calf skin collagen and pepsin-soluble collagen from deer skin may be similar in terms of their primary structure. The thermal denaturation temperature of acid-soluble collagen and pepsin-soluble collagen were 36.67°C and 36.44°C, respectively, and their melting temperatures were 110°C and 120°C, respectively, which suggest high thermal stability. Fourier transform infrared showed a triple helical structure and nuclear magnetic resonance confirmed the presence of ‘hydration’ water. These results provide a basis for large-scale production and further application as alternatives to other mammalian collagens.

Corticosteroids effects on LPS-induced rat inflammatory keratocyte cell model

Purpose

Corticosteroids are efficient anti-inflammation treatments. However, there are still arguments on whether it should be used in keratitis. This study was to observe the effect of corticosteroids on keratocytes both in normal condition and inflammation status in vitro.

Methods

Rat keratocytes were cultured and used for examination. 10 μg/ml lipopolysaccharide (LPS) was used to establish the inflammatory keratocyte cell model, and prednisolone acetate (PA), dexamethasone (Dex) and fluorometholone (Flu) were used as corticosteroids treatments. 5 d-growth curve and cell viabilities were assayed by CCK8, and cell morphologies and migration rate were studied. TNF-α, IL-6 and IL-1β levels were examined by ELISA. Western blotting was used to quantified type VI collagen (Col VI) and matrix metalloproteinase 9 (MMP9) expressions, and immunofluorescence staining assays of Col I and Col VI were carried out.

Results

In normal condition, proliferation and migration of keratocytes were slightly influenced in PA, Dex and Flu groups. The secretion of Col I and Col VI was suppressed and MMP9 expression increased in corticosteroids groups. But no significant difference was seen in TNF-α, IL-6 and IL-1β expression levels. In inflammatory status, TNF-α, IL-6 and MMP9 levels increased in LPS group, while they significantly decreased in corticosteroids groups. Although keratocytes viabilities and migration were slightly affected in 24 h, no significant differences were seen between LPS group and corticosteroids groups in 5-d proliferation. Col I and Col VI secretion in LPS-keratocytes was maintained with corticosteroids treatments.

Conclusions

Corticosteroids showed lightly effects on keratocytes proliferation and migration, but it successfully decreased TNF-α, IL-6 level and maintained the secretion of and Col I and Col VI, while suppressed the expression of MMP9 in LPS-induced keratocytes. PA was suggested to use in early stage of keratitis clinical treatment.

Collagen structure: new tricks from a very old dog

The main features of the triple helical structure of collagen were deduced in the mid-1950s from fibre X-ray diffraction of tendons. Yet, the resulting models only could offer an average description of the molecular conformation. A critical advance came about 20 years later with the chemical synthesis of sufficiently long and homogeneous peptides with collagen-like sequences. The availability of these collagen model peptides resulted in a large number of biochemical, crystallographic and NMR studies that have revolutionized our understanding of collagen structure. High-resolution crystal structures from collagen model peptides have provided a wealth of data on collagen conformational variability, interaction with water, collagen stability or the effects of interruptions. Furthermore, a large increase in the number of structures of collagen model peptides in complex with domains from receptors or collagen-binding proteins has shed light on the mechanisms of collagen recognition. In recent years, collagen biochemistry has escaped the boundaries of natural collagen sequences. Detailed knowledge of collagen structure has opened the field for protein engineers who have used chemical biology approaches to produce hyperstable collagens with unnatural residues, rationally designed collagen heterotrimers, self-assembling collagen peptides, etc. This review summarizes our current understanding of the structure of the collagen triple helical domain (COL×3) and gives an overview of some of the new developments in collagen molecular engineering aiming to produce novel collagen-based materials with superior properties.

Comparative genomics explains the evolutionary success of reef-forming corals

Transcriptome and genome data from twenty stony coral species and a selection of reference bilaterians were studied to elucidate coral evolutionary history. We identified genes that encode the proteins responsible for the precipitation and aggregation of the aragonite skeleton on which the organisms live, and revealed a network of environmental sensors that coordinate responses of the host animals to temperature, light, and pH. Furthermore, we describe a variety of stress-related pathways, including apoptotic pathways that allow the host animals to detoxify reactive oxygen and nitrogen species that are generated by their intracellular photosynthetic symbionts, and determine the fate of corals under environmental stress. Some of these genes arose through horizontal gene transfer and comprise at least 0.2% of the animal gene inventory. Our analysis elucidates the evolutionary strategies that have allowed symbiotic corals to adapt and thrive for hundreds of millions of years.

DOI:http://dx.doi.org/10.7554/eLife.13288.001

For millions of years, reef-building stony corals have created extensive habitats for numerous marine plants and animals in shallow tropical seas. Stony corals consist of many small, tentacled animals called polyps. These polyps secrete a mineral called aragonite to create the reef – an external ‘skeleton’ that supports and protects the corals.

Photosynthesizing algae live inside the cells of stony corals, and each species depends on the other to survive. The algae produce the coral’s main source of food, although they also produce some waste products that can harm the coral if they build up inside cells. If the oceans become warmer and more acidic, the coral are more likely to become stressed and expel the algae from their cells in a process known as coral bleaching. This makes the coral more likely to die or become diseased. Corals have survived previous periods of ocean warming, although it is not known how they evolved to do so.

The evolutionary history of an organism can be traced by studying its genome – its complete set of DNA – and the RNA molecules encoded by these genes. Bhattacharya et al. performed this analysis for twenty stony coral species, and compared the resulting genome and RNA sequences with the genomes of other related marine organisms, such as sea anemones and sponges. In particular, Bhattacharya et al. examined “ortholog” groups of genes, which are present in different species and evolved from a common ancestral gene. This analysis identified the genes in the corals that encode the proteins responsible for constructing the aragonite skeleton. The coral genome also encodes a network of environmental sensors that coordinate how the polyps respond to temperature, light and acidity.

Bhattacharya et al. also uncovered a variety of stress-related pathways, including those that detoxify the polyps of the damaging molecules generated by algae, and the pathways that enable the polyps to adapt to environmental stress. Many of these genes were recruited from other species in a process known as horizontal gene transfer.

The oceans are expected to become warmer and more acidic in the coming centuries. Provided that humans do not physically destroy the corals’ habitats, the evidence found by Bhattacharya et al. suggests that the genome of the corals contains the diversity that will allow them to adapt to these new conditions.

DOI:http://dx.doi.org/10.7554/eLife.13288.002

Gelatin-Methacryloyl Hydrogels: Towards Biofabrication-Based Tissue Repair

Research over the past decade on the cell-biomaterial interface has shifted to the third dimension. Besides mimicking the native extracellular environment by 3D cell culture, hydrogels offer the possibility to generate well-defined 3D biofabricated tissue analogs. In this context, gelatin-methacryloyl (gelMA) hydrogels have recently gained increased attention. This interest is sparked by the combination of the inherent bioactivity of gelatin and the physicochemical tailorability of photo-crosslinkable hydrogels. GelMA is a versatile matrix that can be used to engineer tissue analogs ranging from vasculature to cartilage and bone. Convergence of biological and biofabrication approaches is necessary to progress from merely proving cell functionality or construct shape fidelity towards regenerating tissues. GelMA has a critical pioneering role in this process and could be used to accelerate the development of clinically relevant applications.

Notch-Mediated Cell Adhesion

Notch family members are generally recognized as signaling molecules that control various cellular responses in metazoan organisms. Early fly studies and our mammalian studies demonstrated that Notch family members are also cell adhesion molecules; however, information on the physiological roles of this function and its origin is limited. In this review, we discuss the potential present and ancestral roles of Notch-mediated cell adhesion in order to explore its origin and the initial roles of Notch family members dating back to metazoan evolution. We hypothesize that Notch family members may have initially emerged as cell adhesion molecules in order to mediate multicellularity in the last common ancestor of metazoan organisms.

Effects of decellularized matrices derived from periodontal ligament stem cells and SHED on the adhesion, proliferation and osteogenic differentiation of human dental pulp stem cells in vitro

A major bottleneck to the therapeutic applications of dental pulp stem cells (DPSC) are their limited proliferative capacity ex vivo and tendency to undergo senescence. This may be partly due to the sub-optimal in vitro culture milieu, which could be improved by an appropriate extracellular matrix substratum. This study therefore examined decellularized matrix (DECM) from stem cells derived from human exfoliated deciduous teeth (SHED) and periodontal ligament stem cells (PDLSC), as potential substrata for DPSC culture. Both SHED-DECM and PDLSC-DECM promoted rapid adhesion and spreading of newly-seeded DPSC compared to bare polystyrene (TCPS), with vinculin immunocytochemistry showing expression of more focal adhesions by newly-adherent DPSC cultured on DECM versus TCPS. Culture of DPSC on SHED-DECM and PDLSC-DECM yielded higher proliferation of cell numbers compared to TCPS. The qRT-PCR data showed significantly higher expression of nestin by DPSC cultured on DECM versus the TCPS control. Osteogenic differentiation of DPSC was enhanced by culturing on PDLSC-DECM and SHED-DECM versus TCPS, as demonstrated by alizarin red S staining for mineralized calcium deposition, alkaline phosphatase assay and qRT-PCR analysis of key osteogenic marker expression. Hence, both SHED-DECM and PDLSC-DECM could enhance the ex vivo culture of DPSC under both non-inducing and osteogenic-inducing conditions.

Alpha2beta1 integrin in cancer development and chemoresistance

Extracellular matrix, via its receptors the integrins, has emerged as a crucial factor in cancer development. The α2β1 integrin is a major collagen receptor that is widely expressed and known to promote cell migration and control tissue homeostasis. Growing evidence suggests that it can be a key pathway in cancer. Recent studies have shown that α2β1 integrin is a regulator of cancer metastasis either by promoting or inhibiting the dissemination process of cancer cells. The α2β1 integrin signaling can also enhance tumor angiogenesis. Emerging evidence supports a role for α2β1 integrin in cancer chemoresistance especially in hematological malignancies originating from the T cell lineage. In addition, α2β1 integrin has been associated with cancer stem cells. In this review, we will discuss the complex role of α2β1 integrin in these processes. Collagen is a major matrix protein of the tumor microenvironment and thus, understanding how α2β1 integrin regulates cancer pathogenesis is likely to lead to new therapeutic approaches and agents for cancer treatment.

HANAC Syndrome Col4a1 Mutation Causes Neonate Glomerular Hyperpermeability and Adult Glomerulocystic Kidney Disease

Hereditary angiopathy, nephropathy, aneurysms, and muscle cramps (HANAC) syndrome is an autosomal dominant syndrome caused by mutations in COL4A1 that encodes the α1 chain of collagen IV, a major component of basement membranes. Patients present with cerebral small vessel disease, retinal tortuosity, muscle cramps, and kidney disease consisting of multiple renal cysts, chronic kidney failure, and sometimes hematuria. Mutations producing HANAC syndrome localize within the integrin binding site containing CB3[IV] fragment of the COL4A1 protein. To investigate the pathophysiology of HANAC syndrome, we generated mice harboring the Col4a1 p.Gly498Val mutation identified in a family with the syndrome. Col4a1 G498V mutation resulted in delayed glomerulogenesis and podocyte differentiation without reduction of nephron number, causing albuminuria and hematuria in newborns. The glomerular defects resolved within the first month, but glomerular cysts developed in 3-month-old mutant mice. Abnormal structure of Bowman's capsule was associated with metalloproteinase induction and activation of the glomerular parietal epithelial cells that abnormally expressed CD44,α-SMA, ILK, and DDR1. Inflammatory infiltrates were observed around glomeruli and arterioles. Homozygous Col4a1 G498V mutant mice additionally showed dysmorphic papillae and urinary concentration defects. These results reveal a developmental role for the α1α1α2 collagen IV molecule in the embryonic glomerular basement membrane, affecting podocyte differentiation. The observed association between molecular alteration of the collagenous network in Bowman's capsule of the mature kidney and activation of parietal epithelial cells, matrix remodeling, and inflammation may account for glomerular cyst development and CKD in patients with COL4A1-related disorders.

Mallotus philippinensis Muell. Arg fruit glandular hairs extract promotes wound healing on different wound model in rats

Background

Mallotus philippinensis Muell. Arg (MP, Euphorbiaceae) are widely distributed perennial shrub or small tree in tropical and subtropical region in outer Himalayas regions. Since, Mallotus philippinensis have been shown to have a number of medicinal values. Hence our present study was to investigate the healing potential of fruit extract in rat wound models.

Methods

The study includes acute toxicity and wound healing potential of 50% ethanol extract of MP fruit glandular hair (MPE). MPE (200 mg/kg) was administered orally, once daily for 10 days (incision and dead space wound) and 22 days (excision wound). MPE was found safe when given to rats upto 10 times of optimal effective dose. Wound breaking strength (WBS) in Incision wound and rate of contraction, period of epithelization and scar area in Excision wound were evaluated. Granulation tissue free radicals (nitric oxide and lipid peroxidation), antioxidants (catalase, superoxide dismutase, and reduced glutathione), acute inflammatory marker (myeloperoxidase), connective tissue markers (hydroxyproline, hexosamine, and hexuronic acid), and deep connective tissue histology were studied in Dead space wound.

Results

MPE significantly increased WBS and enhanced wound contraction, and decreased both epithelization period and scar area compared with control group. MPE was found to decrease free radicals (50.8 to 55.2%, P<0.001) and myeloperoxidase (44.0%, P<0.001) but enhanced antioxidants (41.1 to 54.5%, P<0.05 to P<0.001) and connective tissue markers (39.5 to 67.3%, P<0.05 to P<0.01). Histopathological evaluation revealed more density of collagen formation with minimal inflammatory cells in deeper tissues.

Conclusion

Thus, the study revealed Mallotus philippinensis fruit hair extract, safe and effective in wound healing and the healing effects seemed to be due to decrease in free radical generated tissue damage, promoting effects on antioxidant status and faster collagen deposition as evidenced biochemically and histology.

Jellyfish collagen matrices conserve the chondrogenic phenotype in two- and three-dimensional collagen matrices

Cartilage is a tissue with a very low capability of self-repair and the search for suitable materials supporting the chondrogenic phenotype and thus avoiding fibrotic dedifferentiation for matrix-associated chondrocyte transplantation (MACI) is ongoing. Jellyfish collagen was thought to be a suitable material mainly because of its good availability and easy handling. Collagen was extracted from jellyfish Rhopilema esculentum and the spreading of porcine chondrocytes on two (2D) and three dimensional (3D) collagen matrices examined in comparison with vertebrate collagens, placenta collagen and a commercially available matrix from porcine collagen type I (Optimaix®). In 2D, most chondrocytes kept their round shape on jellyfish collagen and vertebrate collagen type II compared with vertebrate collagen type I. This was also confirmed in 3D experiments, where chondrocytes preserved their phenotype on jellyfish collagen, as indicated by high collagen II/(II + I) ratios (≥54 % and ~92 % collagen type II in mRNA and protein, respectively) and no proliferation during 28 days of cultivation. These observations were discussed with a view to potential structural differences of jellyfish collagen, which might influence the integrin-mediated adhesion mechanisms of vertebrate cells on jellyfish collagen. This probably results from a lack of integrin-binding sites and the existence of an alternative binding mechanism such that cells kept their round shape on jellyfish collagen, preventing chondrocytes from dedifferentiation. Thus, collagen from R. esculentum is a very suitable and promising material for cartilage tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.

Integrins in Wound Healing

Significance: Regulation of cell adhesions during tissue repair is fundamentally important for cell migration, proliferation, and protein production. All cells interact with extracellular matrix proteins with cell surface integrin receptors that convey signals from the environment into the nucleus, regulating gene expression and cell behavior. Integrins also interact with a variety of other proteins, such as growth factors, their receptors, and proteolytic enzymes. Re-epithelialization and granulation tissue formation are crucially dependent on the temporospatial function of multiple integrins. This review explains how integrins function in wound repair. Recent Advances: Certain integrins can activate latent transforming growth factor beta-1 (TGF-β1) that modulates wound inflammation and granulation tissue formation. Dysregulation of TGF-β1 function is associated with scarring and fibrotic disorders. Therefore, these integrins represent targets for therapeutic intervention in fibrosis. Critical Issues: Integrins have multifaceted functions and extensive crosstalk with other cell surface receptors and molecules. Moreover, in aberrant healing, integrins may assume different functions, further increasing the complexity of their functionality. Discovering and understanding the role that integrins play in wound healing provides an opportunity to identify the mechanisms for medical conditions, such as excessive scarring, chronic wounds, and even cancer. Future Directions: Integrin functions in acute and chronic wounds should be further addressed in models better mimicking human wounds. Application of any products in acute or chronic wounds will potentially alter integrin functions that need to be carefully considered in the design.

Impact of laser-structured biomaterial interfaces on guided cell responses

To achieve a perfect integration of biomaterials into the body, tissue formation in contact with the interface has to be controlled. In this connection, a selective cell control is required: fibrotic encapsulation has to be inhibited, while tissue guidance has to be stimulated. As conventional biomaterials do not fulfil this specification, functionalization of the biointerface is under development to mimic the natural environment of the cells. One approach focuses on the fabrication of defined surface topographies. Thereby, ultrashort pulse laser ablation is very beneficial, owing to a large variety of fabricated structures, reduced heat-affected zones, high precision and reproducibility. We demonstrate that nanostructures in platinum and microstructures in silicon selectively control cell behaviour: inhibiting fibroblasts, while stimulating neuronal attachment and differentiation. However, the control of fibroblasts strongly correlates with the created size dimensions of the surface structures. These findings suggest favourable biomaterial interfaces for electronic devices. The mechanisms which are responsible for selective cell control are poorly understood. To give an insight, cell behaviour in dependence of biomaterial interfaces is discussed-including basic research on the role of the extracellular matrix. This knowledge is essential to understand such specific cell responses and to optimize biomaterial interfaces for future biomedical applications.

Gelatin-based biomaterial engineering with anhydride-containing oligomeric cross-linkers

Chemically cross-linked gelatin hydrogels are versatile cell-adhesive hydrogel materials that have been established for a variety of biomedical applications. The most prominent cross-linker is glutaraldehyde, which, however, has been described to cause compatibility problems and loss of microscopic but relevant structural features. A recently developed oligomeric cross-linker that contains anhydride functionalities was evaluated as cross-linker for the fabrication of gelatin-based hydrogels and microparticles. In a fast curing reaction, hydrogels composed of gelatin and oligomeric cross-linker were fabricated with good conversion over a wide concentration range of constituents and with cross-linkers of different anhydride contents. Hydrogel properties, such as dry weight and mechanics, could be controlled by hydrogel composition and rheological properties correlated to elastic moduli from 1 to 10 kPa. The gels were shown to be cytocompatible and promoted cell adhesion. In soft formulations, cells migrated into the hydrogel bulk. Gelatin microparticles prepared by a standard water-in-oil emulsion technique were also treated with the novel oligomers, and cross-linking degrees matching those obtained with glutaraldehyde were obtained. At the same time, fewer interparticular cross-links were observed. Fluorescein-derivatized cross-linkers yielded labeled microparticles in a concentration-dependent manner. The oligomeric cross-linkers are presented as an efficient and possibly more functional and compatible alternative to glutaraldehyde. The engineered hydrogel materials hold potential for various biomedical applications.

Evolution of integrin I domains

In humans, an ~200-residue "inserted" I domain, a von Willebrand factor A domain (vWFA), buds out from the β-propeller domain in 9 of 18 integrin α subunits. The vWFA domain is not unique to the α subunit as it is an integral part of all integrin β subunits and many other proteins. The βI domain has always been a component of integrins but the αI domain makes its appearance relatively late, in early chordates, since it is found in tunicates and later diverging species. The tunicate αI domains are distinct from the human collagen and leukocyte recognizing integrin α subunits, but fragments of integrins from agnathastomes suggest that the human-type αI domains arose in an ancestor of the very first vertebrate species. The rise of integrins with αI domains parallels the enormous changes in body plan and systemic development of the chordate line that began some 550 million or more years ago.

Collagen-Based Substrates with Tunable Strength for Soft Tissue Engineering

Through the use of mechanical reinforcement of collagen matrices, mechanically strong and compliant 3D tissue mimetic scaffolds can be generated that act as scaffolds for soft tissue engineering. Collagen has been widely used for the development of materials for repair, augmentation or replacement of damaged or diseased tissue. Herein we describe a facile method for the layer-by-layer fabrication of robust planar collagen fiber constructs. Collagen gels cast in a phosphate buffer were dried to form dense collagen mats. Subsequent gels were layered and dried atop mats to create multilayer constructs possessing a range of tunable strengths (0.5 - 11 MPa) and stiffness (1 - 115 MPa). Depending on processing conditions and crosslinking of constructs, strain to failure ranged between 9 to 48%. Collagen mats were constructed into hernia patches that prevented hernia recurrence in Wistar rats.

Thiol-ene Michael-type formation of gelatin/poly(ethylene glycol) biomatrices for three-dimensional mesenchymal stromal/stem cell administration to cutaneous wounds

Mesenchymal stromal/stem cells (MSCs) are considered promising cellular therapeutics in the fields of tissue engineering and regenerative medicine. MSCs secrete high concentrations of immunomodulatory cytokines and growth factors, which exert paracrine effects on infiltrating immune and resident cells in the wound microenvironment that could favorably promote healing after acute injury. However, better spatial delivery and improved retention at the site of injury are two factors that could improve the clinical application of MSCs. In this study, we utilized thiol-ene Michael-type addition for rapid encapsulation of MSCs within a gelatin/poly(ethylene glycol) biomatrix. This biomatrix was also applied as a provisional dressing to full thickness wounds in Sprague-Dawley rats. The three-way interaction of MSCs, gelatin/poly(ethylene glycol) biomatrices, and host immune cells and adjacent resident cells in the wound microenvironment favorably modulated wound progression and host response. In this model we observed attenuated immune cell infiltration, lack of foreign giant cell (FBGC) formation, accelerated wound closure and re-epithelialization, as well as enhanced neovascularization and granulation tissue formation by 7 days. The MSC entrapped in the gelatin/poly(ethylene glycol) biomatrix localized cell presentation adjacent to the wound microenvironment and thus mediated the early resolution of inflammatory events and facilitated the proliferative phases in wound healing.

Circular permutation directs orthogonal assembly in complex collagen peptide mixtures

Multiple types of natural collagens specifically assemble and co-exist in the extracellular matrix. Although noncollagenous trimerization domains facilitate the folding of triple-helical regions, it is intriguing to ask whether collagen sequences are also capable of controlling heterospecific association. In this study, we designed a model system mimicking simultaneous specific assembly of two collagen heterotrimers using a genetically inspired operation, circular permutation. Previously, surface charge-pair interactions were optimized on three collagen peptides to promote the formation of an abc-type heterotrimer. Circular permutation of these sequences retained networks of stabilizing interactions, preserving both triple-helical structure and heterospecificity of assembly. Combining original peptides A, B, and C and permuted peptides D, E, and F resulted primarily in formation of A:B:C and D:E:F, a heterospecificity of 2 of 56 possible stoichiometries. This degree of specificity in collagen molecular recognition is unprecedented in natural or synthetic collagens. Analysis of natural collagen sequences indicates low similarity between the neighboring exons. Combining the synthetic collagen model and bioinformatic analysis provides insight on how fibrillar collagens might have arisen from the duplication of smaller domains.

Tendon's ultrastructure

The structure of a tendon is an important example of complexity of ECM three-dimensional organization. The extracellular matrix (ECM) is a macromolecular network with both structural and regulatory functions. ECM components belong to four major types of macromolecules: the collagens, elastin, proteoglycans, and noncollagenous glycoproteins. Tendons are made by a fibrous, compact connective tissue that connect muscle to bone designed to transmit forces and withstand tension during muscle contraction. Here we show the ultrastructural features of tendon's components.

Scaffold-free microtissues: differences from monolayer cultures and their potential in bone tissue engineering

OBJECTIVES

Cell-based therapies for bone augmentation after tooth loss and for the treatment of periodontal defects improve healing defects. Usually, osteogenic cells or stem cells are cultivated in 2D primary cultures, before they are combined with scaffold materials, even though this means a loss of the endogenous 3D microenvironment for the cells. Moreover, the use of single-cell suspensions for the inoculation of scaffolds or for the direct application into an area of interest has the disadvantages of low initial cell numbers and susceptibility to unwanted cellular distribution, respectively.

MATERIALS AND METHODS

We addressed the question whether an alternative to monolayer cultures, namely 3D microtissues, has the potential to improve osteogenic tissue engineering and its clinical outcome.

RESULTS

By contrast, to monolayer cultures, osteogenic differentiation of 3D microtissues is enhanced by mimicking in vivo conditions. It seems that the osteogenic differentiation in microtissues is enhanced by strong integrin-extracellular matrix interaction and by stronger autocrine BMP2 signaling. Moreover, microtissues are less prone to wash out by body fluids and allow the precise administration of large cell numbers.

CONCLUSION

Microtissue cultures have closer characteristics with cells in vivo and their enhanced osteogenic differentiation makes scaffold-free microtissues a promising concept in osteogenic tissue engineering.

CLINICAL RELEVANCE

Microtissues are particularly suitable for tissue engineering because they improve seeding efficiency of biomaterials by increasing the cell load of a scaffold. This results in accelerated osteogenic tissue formation and could contribute to earlier implant stability in mandibular bone augmentation.

Sequence recombination improves target specificity in a redesigned collagen peptide abc-type heterotrimer

Stability of the collagen triple helix is largely governed by its imino acid content, namely the occurrence of proline and 4R-hydroxyproline at the X and Y positions, respectively, of the periodic (Gly-X-Y)(n) sequence. Although other amino acids at these positions reduce stability of the triple helix, this can be partially compensated by introducing intermolecular side-chain salt bridges. This approach was previously used to design an abc-type heterotrimer composed of one basic, one acidic, and one neutral imino acid rich chain (Gauba and Hartgerink, J Am Chem Soc 2007;129:15034-15041). In this study, an abc-type heterotrimer was designed to be the most stable species using a sequence recombination strategy that preserved both the amino acid composition and the network of interchain salt bridges of the original design. The target heterotrimer had the highest T(m) of 50 °C, 7 °C greater than the next most stable species. Stability of the heterotrimer decreased with increasing ionic strength, consistent with the role of intermolecular salt bridges in promoting stability. Quantitative meta-analysis of these results and published stability measurements on closely related peptides was used to discriminate the contributions of backbone propensity and side-chain electrostatics to collagen stability.

C1q limits dendritic cell differentiation and activation by engaging LAIR-1

C1q, the first component of complement, and leukocyte-associated Ig-like receptor 1 (LAIR-1; CD305), an inhibitory receptor expressed on hematopoietic cells, have both been associated with arrest of monocyte-derived dendritic cell (DC) differentiation and inhibition of Toll-like receptor activity in plasmacytoid DCs. Defects in both molecules have been implicated in susceptibility to, and progression of, systemic lupus erythematosus. Inhibitory signaling partners for C1q on monocytes and DCs remain undefined. Because C1q contains collagen-like motifs and LAIR-1 is a universal collagen receptor, we hypothesized that C1q is a functional ligand for LAIR-1. Binding analyses in cell-free systems and on the cell membrane demonstrate that C1q and its collagen tail associate with LAIR-1 and LAIR-2 (CD306), a soluble inhibitor of LAIR-1. Both C1q and its collagen tail trigger phosphorylation of LAIR-1 immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in monocytes. Functional analyses show that C1q-mediated inhibition of monocyte-DC differentiation and C1q-mediated inhibition of IFN-α production by plasmacytoid DCs were both reversed by LAIR-2. Moreover, C1q-mediated inhibition of DC differentiation was reversed by LAIR-1 siRNA. Thus, C1q is a functional ligand for LAIR-1 restricting immune cell differentiation and activation. The discovery of C1q interactions with LAIR-1 and LAIR-2 lends much needed insight into molecular mechanisms operating to prevent the loss of tolerance, particularly in systemic lupus erythematosus.

The evolution of metazoan extracellular matrix

The modular domain structure of extracellular matrix (ECM) proteins and their genes has allowed extensive exon/domain shuffling during evolution to generate hundreds of ECM proteins. Many of these arose early during metazoan evolution and have been highly conserved ever since. Others have undergone duplication and divergence during evolution, and novel combinations of domains have evolved to generate new ECM proteins, particularly in the vertebrate lineage. The recent sequencing of several genomes has revealed many details of this conservation and evolution of ECM proteins to serve diverse functions in metazoa.

Human pathogens utilize host extracellular matrix proteins laminin and collagen for adhesion and invasion of the host

Laminin (Ln) and collagen are multifunctional glycoproteins that play an important role in cellular morphogenesis, cell signalling, tissue repair and cell migration. These proteins are ubiquitously present in tissues as a part of the basement membrane (BM), constitute a protective layer around blood capillaries and are included in the extracellular matrix (ECM). As a component of BMs, both Lns and collagen(s), thus function as major mechanical containment molecules that protect tissues from pathogens. Invasive pathogens breach the basal lamina and degrade ECM proteins of interstitial spaces and connective tissues using various ECM-degrading proteases or surface-bound plasminogen and matrix metalloproteinases recruited from the host. Most pathogens associated with the respiratory, gastrointestinal, or urogenital tracts, as well as with the central nervous system or the skin, have the capacity to bind and degrade Lns and collagen(s) in order to adhere to and invade host tissues. In this review, we focus on the adaptability of various pathogens to utilize these ECM proteins as enhancers for adhesion to host tissues or as a targets for degradation in order to breach the cellular barriers. The major pathogens discussed are Streptococcus, Staphylococcus, Pseudomonas, Salmonella, Yersinia, Treponema, Mycobacterium, Clostridium, Listeria, Porphyromonas and Haemophilus; Candida, Aspergillus, Pneumocystis, Cryptococcus and Coccidioides; Acanthamoeba, Trypanosoma and Trichomonas; retrovirus and papilloma virus.

Scaffold-free microtissues: differences from monolayer cultures and their potential in bone tissue engineering

Objectives

The paper’s aim is to review dentin hypersensitivity (DHS), discussing pain mechanisms and aetiology.

Materials and methods

Literature was reviewed using search engines with MESH terms, DH pain mechanisms and aetiology (including abrasion, erosion and periodontal disease).

Results

The many hypotheses proposed for DHS attest to our lack of knowledge in understanding neurophysiologic mechanisms, the most widely accepted being the hydrodynamic theory. Dentin tubules must be patent from the oral environment to the pulp. Dentin exposure, usually at the cervical margin, is due to a variety of processes involving gingival recession or loss of enamel, predisposing factors being periodontal disease and treatment, limited alveolar bone, thin biotype, erosion and abrasion.

Conclusions

The current pain mechanism of DHS is thought to be the hydrodynamic theory. The initiation and progression of DHS are influenced by characteristics of the teeth and periodontium as well as the oral environment and external influences. Risk factors are numerous often acting synergistically and always influenced by individual susceptibility.

Clinical relevance

Whilst the pain mechanism of DHS is not well understood, clinicians need to be mindful of the aetiology and risk factors in order to manage patients’ pain and expectations and prevent further dentin exposure with subsequent sensitivity.

Integrin signaling in cancer cell survival and chemoresistance

Resistance to apoptosis and chemotherapy is a hallmark of cancer cells, and it is a critical factor in cancer recurrence and patient relapse. Extracellular matrix (ECM) via its receptors, the integrins, has emerged as a major pathway contributing to cancer cell survival and resistance to chemotherapy. Several studies over the last decade have demonstrated that ECM/integrin signaling provides a survival advantage to various cancer cell types against numerous chemotherapeutic drugs and against antibody therapy. In this paper, we will discuss the major findings on how ECM/integrin signaling protects tumor cells from drug-induced apoptosis. We will also discuss the potential role of ECM in malignant T-cell survival and in cancer stem cell resistance. Understanding how integrins and their signaling partners promote tumor cell survival and chemoresistance will likely lead to the development of new therapeutic strategies and agents for cancer treatment.

Natural and Genetically Engineered Proteins for Tissue Engineering

To overcome the limitations of traditionally used autografts, allografts and, to a lesser extent, synthetic materials, there is the need to develop a new generation of scaffolds with adequate mechanical and structural support, control of cell attachment, migration, proliferation and differentiation and with bio-resorbable features. This suite of properties would allow the body to heal itself at the same rate as implant degradation. Genetic engineering offers a route to this level of control of biomaterial systems. The possibility of expressing biological components in nature and to modify or bioengineer them further, offers a path towards multifunctional biomaterial systems. This includes opportunities to generate new protein sequences, new self-assembling peptides or fusions of different bioactive domains or protein motifs. New protein sequences with tunable properties can be generated that can be used as new biomaterials. In this review we address some of the most frequently used proteins for tissue engineering and biomedical applications and describe the techniques most commonly used to functionalize protein-based biomaterials by combining them with bioactive molecules to enhance biological performance. We also highlight the use of genetic engineering, for protein heterologous expression and the synthesis of new protein-based biopolymers, focusing the advantages of these functionalized biopolymers when compared with their counterparts extracted directly from nature and modified by techniques such as physical adsorption or chemical modification.

Collagen-like polypeptide poly(Pro-Hyp-Gly) conjugated with Gly-Arg-Gly-Asp-Ser and Pro-His-Ser-Arg-Asn peptides enchances cell adhesion, migration, and stratification

Collagens are widely used in medical applications, including as a scaffold for tissue regeneration. However, animal-derived collagens have several drawbacks, such as low thermal stability, nonspecific cell adhesion, antigenicity, and contamination with pathogenic substances. To overcome these problems, we chemically synthesized the collagen-like polypeptide, poly(prolyl-hydroxyprolyl-glycyl) (poly(Pro-Hyp-Gly)), which forms a collagen-like triple-helical structure and shows biodegradability and biocompatibility. Here, we designed a novel scaffold where fibronectin-derived Gly Arg-Gly-Asp-Ser (GRGDS) and Pro-His-Ser-Arg-Asn (PHSRN) peptides were simultaneously conjugated with poly(Pro-Hyp-Gly). We assessed cell adhesion and migration activities using NIH3T3 cells in the scaffold and stratification ofimmortalized rabbit corneal epithelial cells. Cell adhesion was enhanced in scaffolds with GRGDS, increased with increasing amounts of conjugated GRGDS, and was significantly higher than bovine type I atelocollagen but lower than bovine fibronectin. Interestingly, simultaneous conjugation of GRGDS and PHSRN synergistically enhanced cell migration. Scaffolds containing almost equal amounts of GRGDS and PHSRN showed significantly higher cell migration than bovine type I atelocollagen. Addition of free GRGDS completely inhibited cell migration on the scaffold, whereas addition of free PHSRN partially inhibited cell migration. These results suggest that GRGDS plays a definitive role, and PHSRN plays an additional role, in cell migration. Conjugation of GRGDS resulted in the same level of stratification of rabbit corneal epithelial cells compared with bovine type I atelocollagen and bovine fibronectin. Because the simultaneous conjugation of GRGDS and PHSRN on poly(Pro-Hyp-Gly) enhances cell adhesion, migration, and stratification, it may be a useful scaffold for tissue regeneration.

Molecular architecture and function of matrix adhesions

Cell adhesions mediate important bidirectional interactions between cells and the extracellular matrix. They provide an interactive interface between the extracellular chemical and physical environment and the cellular scaffolding and signaling machinery. This dynamic, reciprocal regulation of intracellular processes and the matrix is mediated by membrane receptors such as the integrins, as well as many other components that comprise the adhesome. Adhesome constituents assemble themselves into different types of cell adhesion structures that vary in molecular complexity and change over time. These cell adhesions play crucial roles in cell migration, proliferation, and determination of cell fate.

Surface-sensitive Raman spectroscopy of collagen I fibrils

Collagen fibrils are the main constituent of the extracellular matrix surrounding eukaryotic cells. Although the assembly and structure of collagen fibrils is well characterized, very little appears to be known about one of the key determinants of their biological function-namely, the physico-chemical properties of their surface. One way to obtain surface-sensitive structural and chemical data is to take advantage of the near-field nature of surface- and tip-enhanced Raman spectroscopy. Using Ag and Au nanoparticles bound to Collagen type-I fibrils, as well as tips coated with a thin layer of Ag, we obtained Raman spectra characteristic to the first layer of collagen molecules at the surface of the fibrils. The most frequent Raman peaks were attributed to aromatic residues such as phenylalanine and tyrosine. In several instances, we also observed Amide I bands with a full width at half-maximum of 10-30 cm(-1). The assignment of these Amide I band positions suggests the presence of 3(10)-helices as well as α- and β-sheets at the fibril's surface.

Focal adhesions in osteoneogenesis

As materials technology and the field of tissue engineering advance, the role of cellular adhesive mechanisms, in particular, interactions with implantable devices, becomes more relevant in both research and clinical practice. A key tenet of medical device technology is to use the exquisite ability of biological systems to respond to the material surface or chemical stimuli in order to help to develop next-generation biomaterials. The focus of this review is on recent studies and developments concerning focal adhesion formation in osteoneogenesis, with an emphasis on the influence of synthetic constructs on integrin-mediated cellular adhesion and function.