Isolation, characterization and biological evaluation of jellyfish collagen for use in biomedical applications.

Fibrillar collagens are the more abundant extracellular proteins. They form a metazoan-specific family, and are highly conserved from sponge to human. Their structural and physiological properties have been successfully used in the food, cosmetic, and pharmaceutical industries. On the other hand, the increase of jellyfish has led us to consider this marine animal as a natural product for food and medicine. Here, we have tested different Mediterranean jellyfish species in order to investigate the economic potential of their collagens. We have studied different methods of collagen purification (tissues and experimental procedures). The best collagen yield was obtained using Rhizostoma pulmo oral arms and the pepsin extraction method (2-10 mg collagen/g of wet tissue). Although a significant yield was obtained with Cotylorhiza tuberculata (0.45 mg/g), R. pulmo was used for further experiments, this jellyfish being considered as harmless to humans and being an abundant source of material. Then, we compared the biological properties of R. pulmo collagen with mammalian fibrillar collagens in cell cytotoxicity assays and cell adhesion. There was no statistical difference in cytotoxicity (p > 0.05) between R. pulmo collagen and rat type I collagen. However, since heparin inhibits cell adhesion to jellyfish-native collagen by 55%, the main difference is that heparan sulfate proteoglycans could be preferentially involved in fibroblast and osteoblast adhesion to jellyfish collagens. Our data confirm the broad harmlessness of jellyfish collagens, and their biological effect on human cells that are similar to that of mammalian type I collagen. Given the bioavailability of jellyfish collagen and its biological properties, this marine material is thus a good candidate for replacing bovine or human collagens in selected biomedical applications.

The fibrillar collagen family.

Collagens, or more precisely collagen-based extracellular matrices, are often considered as a metazoan hallmark. Among the collagens, fibrillar collagens are present from sponges to humans, and are involved in the formation of the well-known striated fibrils. In this review we discuss the different steps in the evolution of this protein family, from the formation of an ancestral fibrillar collagen gene to the formation of different clades. Genomic data from the choanoflagellate (sister group of Metazoa) Monosiga brevicollis, and from diploblast animals, have suggested that the formation of an ancestral alpha chain occurred before the metazoan radiation. Phylogenetic studies have suggested an early emergence of the three clades that were first described in mammals. Hence the duplication events leading to the formation of the A, B and C clades occurred before the eumetazoan radiation. Another important event has been the two rounds of "whole genome duplication" leading to the amplification of fibrillar collagen gene numbers, and the importance of this diversification in developmental processes. We will also discuss some other aspects of fibrillar collagen evolution such as the development of the molecular mechanisms involved in the formation of procollagen molecules and of striated fibrils.

The Multimerization State of the Amyloid-ß42 Amyloid Peptide Governs its Interaction Network with the Extracellular Matrix.

The goals of this work were i) to identify the interactions of amyloid-ß (Aß)42 under monomeric, oligomeric, and fibrillar forms with the extracellular matrix (ECM) and receptors, ii) to determine the influence of Aß42 supramolecular organization on these interactions, and iii) to identify the molecular functions, biological processes, and pathways targeted by Aß42 in the ECM. The ECM and cell surface partners of Aß42 and its supramolecular forms were identified with protein and glycosaminoglycan (GAG) arrays (81 molecules in triplicate) probed by surface plasmon resonance imaging. The number of partners of Aß42 increased upon its multimerization, ranging from 4 for the peptide up to 53 for the fibrillar aggregates. The peptide interacted only with ECM proteins but their percentage among Aß42 partners decreased upon multimerization. Aß42 and its supramolecular forms recognized different molecular features on their partners, and the partners of Aß42 fibrillar forms were enriched in laminin IV-A, N-terminal, and EGF-like domains. Aß42 oligomerization triggered interactions with receptors, whereas Aß42 fibrillogenesis promoted binding to GAGs, proteoglycans, enzymes, and growth factors and the ability to interact with perineuronal nets. Fibril aggregation bind to further membrane proteins including tumor endothelial marker-8, syndecan-4, and discoidin-domain receptor-2. The partners of the Aß42 supramolecular forms are enriched in proteins contributing to cell growth and/or maintenance, involved in integrin cell surface interactions and expressed in kidney cancer, preadipocytes, and dentin. In conclusion, the supramolecular assembly of Aß42 governs its ability to interact in vitro with ECM proteins, remodeling and crosslinking ECM enzymes, proteoglycans, and receptors.

A model of tenascin-X integration within the collagenous network.

Tenascin-X is an extracellular matrix protein whose absence leads to an Ehlers-Danlos syndrome in humans, characterized mainly by disorganisation of collagen and elastic fibril networks. After producing recombinant full-length tenascin-X in mammalian cells, we find that this protein assembled into disulfide-linked oligomers. Trimers were the predominant form observed using rotary shadowing. By solid phase interaction studies, we demonstrate that tenascin-X interacts with types I, III and V fibrillar collagen molecules when they are in native conformation. The use of tenascin-X variants with large regions deleted indicated that both epidermal growth factor repeats and the fibrinogen-like domain are involved in this interaction. Moreover, we demonstrate that tenascin-X binds to the fibril-associated types XII and XIV collagens. We thus suggest that tenascin-X, via trimerization and multiple interactions with components of collagenous fibrils, plays a crucial role in the organisation of extracellular matrices.

Evaluation of polylactic acid nanoparticles safety using Drosophila model.

Cytotoxicity of nanoparticles and their sub-lethal effect on cell behavior and cell fate are a high topic of studies in the nanomaterial field. With an explosion of nanoparticle types (size, shape, polarity, stiffness, composition, etc.), Drosophila has become an attractive animal model for high throughput analysis of these nanocarriers in the drug delivery field with applications in cancer therapy, or simply to generate a fast and complete cytotoxic study of a peculiar nanoparticle. In respect to that, we have conducted an in cellulo study of poly(lactic acid) (PLA) nanoparticle cytotoxicity, and determined that near lethal nanoparticle doses, oxidative stress as well as P53 and ATP pathways may lead to cell cycle arrest at G1, and ultimately to cell death. Neither viability nor the development of Drosophila larvae are affected by the ingestion of PLA nanoparticles at sub-lethal concentrations. Drosophila will be a useful model to study PLA and PLA-modified nanoparticle toxicity, and nanoparticle fate after ingestion.

Poly(Lactic Acid) Nanoparticles Targeting α5ß1 Integrin as Vaccine Delivery Vehicle, a Prospective Study.

Biodegradable polymeric nanoparticles are vehicles of choice for drug delivery and have the ability to encapsulate and present at their surface different molecules of interest. Among these bio-nanocarriers, poly(lactic acid) (PLA) nanoparticles have been used as adjuvant and vehicle for enhanced vaccine efficacy. In order to develop an approach to efficient vaccine delivery, we developed nanoparticles to target α5ß1 positive cells. We first overproduced, in bacteria, human fibronectin FNIII9/10 recombinant proteins possessing an integrin α5ß1 binding site, the RGDS sequence, or a mutated form of this site. After having confirmed the integrin binding properties of these recombinant proteins in cell culture assays, we were able to formulate PLA nanoparticles with these FNIII9/10 proteins at their surface. We then confirmed, by fluorescence and confocal microscopy, an enhanced cellular uptake by α5ß1+ cells of RGDS-FNIII9/10 coated PLA nanoparticles, in comparison to KGES-FNIII9/10 coated or non-coated controls. As a first vaccination approach, we prepared PLA nanoparticles co-coated with p24 (an HIV antigen), and RGDS- or KGES-FNIII9/10 proteins, followed by subcutaneous vaccine administration, in mice. Although we did not detect improvements in the apparent humoral response to p24 antigen in the serum of RGDS/p24 nanoparticle-treated mice, the presence of the FNIII proteins increased significantly the avidity index of anti-p24 antibodies compared to p24-nanoparticle-injected control mice. Future developments of this innovative targeted vaccine are discussed.

Overcoming the toxicity of membrane peptide expression in bacteria by upstream insertion of Asp-Pro sequence.

Transmembrane (TM) peptides often induce toxic effects when expressed in bacteria, probably due to membrane destabilization. We report here that in the case of the TM domains of hepatitis C virus (HCV) E1 and E2 envelope proteins, which are both particularly toxic for the bacteria, the insertion of the Asp-Pro (DP) sequence dramatically reduced their toxicities and promoted their expressions when produced as glutathione S-transferase (GST) GST-DP-TM chimeras. Subcellular fractionation showed that these chimeras co-sediment with the membrane fraction and contain active GST that could be solubilized with a mild detergent. Surprisingly, immuno-gold electron microscopy clearly showed that such chimeras are not localized in the membrane but in the cytosol. We thus postulate that they likely form proteo-lipidic aggregates, which prevent the bacteria from toxicity by sequestering the TM part of the chimeras. The reduction of toxicity in the presence of the Asp-Pro sequence is possibly due to Asp's negative charge that probably disadvantages the binding of the TM peptides to the membrane. In addition, the structural features of Pro residue could promote the formation of chimera aggregates.

Tenascin-X: beyond the architectural function.

Tenascin-X is the largest member of the tenascin (TN) family of evolutionary conserved extracellular matrix glycoproteins, which also comprises TN-C, TN-R and TN-W. Among this family, TN-X is the only member described so far to exert a crucial architectural function as evidenced by a connective tissue disorder (a recessive form of Ehlers-Danlos syndrome) resulting from a loss-of-function of this glycoprotein in humans and mice. However, TN-X is more than an architectural protein, as it displays features of a matricellular protein by modulating cell adhesion. However, the cellular functions associated with the anti-adhesive properties of TN-X have not yet been revealed. Recent findings indicate that TN-X is also an extracellular regulator of signaling pathways. Indeed, TN-X has been shown to regulate the bioavailability of the Transforming Growth Factor (TGF)-ß and to modulate epithelial cell plasticity. The next challenges will be to unravel whether the signaling functions of TN-X are functionally linked to its matricellular properties.

Tenascin-X promotes epithelial-to-mesenchymal transition by activating latent TGF-ß.

Transforming growth factor ß (TGF-ß) isoforms are secreted as inactive complexes formed through noncovalent interactions between the bioactive TGF-ß entity and its N-terminal latency-associated peptide prodomain. Extracellular activation of the latent TGF-ß complex is a crucial step in the regulation of TGF-ß function for tissue homeostasis. We show that the fibrinogen-like (FBG) domain of the matrix glycoprotein tenascin-X (TNX) interacts physically with the small latent TGF-ß complex in vitro and in vivo, thus regulating the bioavailability of mature TGF-ß to cells by activating the latent cytokine into an active molecule. Activation by the FBG domain most likely occurs through a conformational change in the latent complex and involves a novel cell adhesion-dependent mechanism. We identify α11ß1 integrin as a cell surface receptor for TNX and show that this integrin is crucial to elicit FBG-mediated activation of latent TGF-ß and subsequent epithelial-to-mesenchymal transition in mammary epithelial cells.

Apoptosis in capillary endothelial cells in ageing skeletal muscle.

The age-related loss of skeletal muscle mass and function (sarcopenia) is a consistent hallmark of ageing. Apoptosis plays an important role in muscle atrophy, and the intent of this study was to specify whether apoptosis is restricted to myofibre nuclei (myonuclei) or occurs in satellite cells or stromal cells of extracellular matrix (ECM). Sarcopenia in mouse gastrocnemius muscle was characterized by myofibre atrophy, oxidative type grouping, delocalization of myonuclei and ECM fibrosis. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) indicated a sharp rise in apoptosis during ageing. TUNEL coupled with immunostaining for dystrophin, paired box protein-7 (Pax7) or laminin-2α, respectively, was used to identify apoptosis in myonuclei, satellite cells and stromal cells. In adult muscle, apoptosis was not detected in myofibres, but was restricted to stromal cells. Moreover, the age-related rise in apoptotic nuclei was essentially due to stromal cells. Myofibre-associated apoptosis nevertheless occurred in old muscle, but represented < 20% of the total muscle apoptosis. Specifically, apoptosis in old muscle affected a small proportion (0.8%) of the myonuclei, but a large part (46%) of the Pax7(+) satellite cells. TUNEL coupled with CD31 immunostaining further attributed stromal apoptosis to capillary endothelial cells. Age-dependent rise in apoptotic capillary endothelial cells was concomitant with altered levels of key angiogenic regulators, perlecan and a perlecan domain V (endorepellin) proteolytic product. Collectively, our results indicate that sarcopenia is associated with apoptosis of satellite cells and impairment of capillary functions, which is likely to contribute to the decline in muscle mass and functionality during ageing.

Relationships between structural characteristics of bovine intramuscular connective tissue assessed by image analysis and collagen and proteoglycan content.

Three muscles (Longissimus thoracis, Semimembranosus, Biceps femoris) of 40 young bulls from 3 breeds were used to quantify structural characteristics of bovine connective tissue by image analysis, with both macroscopic and microscopic approaches. Collagen and proteoglycan content was also investigated. Perimysium occupied a greater area (8 vs 6%), and was wider (42 vs 2 µm) and shorter per unit area (1.9 vs 30 mm mm(-2)) than endomysium. Perimysium and endomysium from Longissimus were thinner, less ramified than in Biceps. Longissimus showed less total collagen and cross-linking and more proteoglycans (P<0.0001) than Biceps muscle. Blond d'Aquitaine perimysium occupied less area, was more ramified and muscles contained less collagen, cross-linking and more proteoglycans than Angus (P<0.001). Limousin was intermediate. High proteoglycan content in muscle containing less total collagen suggested a complementarity between these molecules. They might influence mechanical properties of intramuscular connective tissue. This was especially true given that proteoglycans and total collagen were negatively and positively linked with structural parameters, respectively.

Structural and biochemical characteristics of bovine intramuscular connective tissue and beef quality.

The aim of the study was to evaluate the impact of structural and biochemical characteristics of muscle intramuscular connective tissue on beef quality. The experimental design was based on three muscles of three breeds sampled as fresh material and cooked at 55°C (Longissimus thoracis and Semimembranosus) or at 70°C (Semimembranosus and Biceps femoris) for quality assessment. The results showed that muscle characteristics influence beef quality differently from one muscle to another. In grilled LT, proteoglycan content contributed negatively to juiciness, and intramuscular lipids were linked positively to tenderness, flavour, residues and overall liking scores. In grilled SM, cross-link and lipid contents were involved in beef quality. In BF cooked to 70°C, perimysial branch points were negatively linked to tenderness. In SM cooked to 70°C, perimysial area was involved in beef quality. These results should allow a better understanding of the factors involved in background toughness, in juiciness and flavour of meat.

Tenascin-X increases the stiffness of collagen gels without affecting fibrillogenesis.

Tenascin-X is an extracellular matrix protein whose absence leads to an Ehlers-Danlos Syndrome in humans, mainly characterised by connective tissue defects including the disorganisation of fibrillar networks, a reduced collagen deposition, and modifications in the mechanical properties of dense tissues. Here we tested the effect of tenascin-X on in vitro collagen fibril formation. We observed that the main parameters of fibrillogenesis were unchanged, and that the diameter of fibrils was not significantly different when they were formed in the presence of tenascin-X. Interestingly, mechanical analysis of collagen gels showed an increased compressive resistance of the gels containing tenascin-X, indicating that this protein might be directly involved in determining the mechanical properties of collagen-rich tissues in vivo.

Nanomechanical properties of tenascin-X revealed by single-molecule force spectroscopy.

Tenascin-X is an extracellular matrix protein and binds a variety of molecules in extracellular matrix and on cell membrane. Tenascin-X plays important roles in regulating the structure and mechanical properties of connective tissues. Using single-molecule atomic force microscopy, we have investigated the mechanical properties of bovine tenascin-X in detail. Our results indicated that tenascin-X is an elastic protein and the fibronectin type III (FnIII) domains can unfold under a stretching force and refold to regain their mechanical stability upon the removal of the stretching force. All the 30 FnIII domains of tenascin-X show similar mechanical stability, mechanical unfolding kinetics, and contour length increment upon domain unfolding, despite their large sequence diversity. In contrast to the homogeneity in their mechanical unfolding behaviors, FnIII domains fold at different rates. Using the 10th FnIII domain of tenascin-X (TNXfn10) as a model system, we constructed a polyprotein chimera composed of alternating TNXfn10 and GB1 domains and used atomic force microscopy to confirm that the mechanical properties of TNXfn10 are consistent with those of the FnIII domains of tenascin-X. These results lay the foundation to further study the mechanical properties of individual FnIII domains and establish the relationship between point mutations and mechanical phenotypic effect on tenascin-X. Moreover, our results provided the opportunity to compare the mechanical properties and design of different forms of tenascins. The comparison between tenascin-X and tenascin-C revealed interesting common as well as distinguishing features for mechanical unfolding and folding of tenascin-C and tenascin-X and will open up new avenues to investigate the mechanical functions and architectural design of different forms of tenascins.

Demosponge and sea anemone fibrillar collagen diversity reveals the early emergence of A/C clades and the maintenance of the modular structure of type V/XI collagens from sponge to human.

Collagens are often considered a metazoan hallmark, with the fibril-forming fibrillar collagens present from sponges to human. From evolutionary studies, three fibrillar collagen clades (named A, B, and C) have been defined and shown to be present in mammals, whereas the emergence of the A and B clades predates the protostome/deuterostome split. Moreover, several C clade fibrillar collagen chains are present in some invertebrate deuterostome genomes but not in protostomes whose genomes have been sequenced. The newly sequenced genomes of the choanoflagellate Monosiga brevicollis, the demosponge Amphimedon queenslandica, and the cnidarians Hydra magnipapillata (Hydra) and Nematostella vectensis (sea anemone) allow us to have a better understanding of the origin and evolution of fibrillar collagens. Analysis of these genomes suggests that an ancestral fibrillar collagen gene arose at the dawn of the Metazoa, before the divergence of sponge and eumetazoan lineages. The duplication events leading to the formation of the three fibrillar collagen clades (A, B, and C) occurred before the eumetazoan radiation. Interestingly, only the B clade fibrillar collagens preserved their characteristic modular structure from sponge to human. This observation is compatible with the suggested primordial function of type V/XI fibrillar collagens in the initiation of the formation of the collagen fibrils.

Insights into early extracellular matrix evolution: spongin short chain collagen-related proteins are homologous to basement membrane type IV collagens and form a novel family widely distributed in invertebrates.

Collagens are thought to represent one of the most important molecular innovations in the metazoan line. Basement membrane type IV collagen is present in all Eumetazoa and was found in Homoscleromorpha, a sponge group with a well-organized epithelium, which may represent the first stage of tissue differentiation during animal evolution. In contrast, spongin seems to be a demosponge-specific collagenous protein, which can totally substitute an inorganic skeleton, such as in the well-known bath sponge. In the freshwater sponge Ephydatia mülleri, we previously characterized a family of short-chain collagens that are likely to be main components of spongins. Using a combination of sequence- and structure-based methods, we present evidence of remote homology between the carboxyl-terminal noncollagenous NC1 domain of spongin short-chain collagens and type IV collagen. Unexpectedly, spongin short-chain collagen-related proteins were retrieved in nonsponge animals, suggesting that a family related to spongin constitutes an evolutionary sister to the type IV collagen family. Formation of the ancestral NC1 domain and divergence of the spongin short-chain collagen-related and type IV collagen families may have occurred before the parazoan-eumetazoan split, the earliest divergence among extant animal phyla. Molecular phylogenetics based on NC1 domain sequences suggest distinct evolutionary histories for spongin short-chain collagen-related and type IV collagen families that include spongin short-chain collagen-related gene loss in the ancestors of Ecdyzosoa and of vertebrates. The fact that a majority of invertebrates encodes spongin short-chain collagen-related proteins raises the important question to the possible function of its members. Considering the importance of collagens for animal structure and substratum attachment, both families may have played crucial roles in animal diversification.

Transplantation of reconstructed human skin on nude mice: a model system to study expression of human tenascin-X and elastic fiber components.

Tenascin-X is a large extracellular matrix protein that is widely expressed in connective tissues during development and in the adult. Genetically determined deficiency of tenascin-X causes the connective tissue disease Ehlers-Danlos syndrome. These patients show reduced collagen density and fragmentation of elastic fibers in their skin. In vitro studies on the role of tenascin-X in elastic fiber biology are hampered because monolayers of fibroblasts do not deposit tenascin-X and elastic fibers into the extracellular matrix. Here, we applied an organotypic culture model of fibroblasts and keratinocytes to address this issue. We investigated the deposition of tenascin-X and elastin into skin-equivalent in vitro and also in vivo after transplantation onto immunodeficient mice. Whereas tenascin-C and fibrillin-1 were readily expressed in the skin-equivalents before transplantation, tenascin-X and elastin were not present. Three weeks post-grafting, a network of elastin was observed that coincided with the appearance of tenascin-X. At the ultrastructural level, microfibrils were observed, some of which were associated with elastin. Transplanted skin-equivalents containing tenascin-X-deficient fibroblasts showed deposition of immunoreactive elastin in similar quantities and distribution as those containing control fibroblasts. This suggests that tenascin-X is important for the stability and maintenance of established elastin fibers, rather than for the initial phase of elastogenesis. Thus, the transplantation of reconstructed skin on nude mice allows the study of tenascin-X and elastin expression and could be used as a model system to study the potential role of tenascin-X in matrix assembly and stability.

Distinct maturations of N-propeptide domains in fibrillar procollagen molecules involved in the formation of heterotypic fibrils in adult sea urchin collagenous tissues.

We have characterized the primary structure of a new sea urchin fibrillar collagen, the 5alpha chain, including nine repeats of the sea urchin fibrillar module in its N-propeptide. By Western blot and immunofluorescence analyses, we have shown that 5alpha is co-localized in adult collagenous ligaments with the 2alpha fibrillar collagen chain and fibrosurfin, two other extracellular matrix proteins possessing sea urchin fibrillar modules. At the ultrastructural level, the 5alpha N-propeptide is detected at the surface of fibrils, suggesting the retention of this domain in mature collagen molecules. Biochemical characterization of pepsinized collagen molecules extracted from the test tissue (the endoskeleton) together with a matrix-assisted laser desorption ionization time-of-flight analysis allowed us to determine that 5alpha is a quantitatively minor fibrillar collagen chain in comparison with the 1alpha and 2alpha chains. Moreover, 5alpha forms heterotrimeric molecules with two 1alpha chains. Hence, as in vertebrates, sea urchin collagen fibrils are made up of quantitatively major and minor fibrillar molecules undergoing distinct maturation of their N-propeptide regions and participating in the formation of heterotypic fibrils.

Evolution of collagens.

The extracellular matrix is often defined as the substance that gives multicellular organisms (from plants to vertebrates) their structural integrity, and is intimately involved in their development. Although the general functions of extracellular matrices are comparable, their compositions are quite distinct. One of the specific components of metazoan extracellular matrices is collagen, which is present in organisms ranging from sponges to humans. By comparing data obtained in diploblastic, protostomic, and deuterostomic animals, we have attempted to trace the evolution of collagens and collagen-like proteins. Moreover, the collagen story is closely involved with the emergence and evolution of metazoa. The collagen triple helix is one of numerous modules that arose during the metazoan radiation which permit the formation of large multimodular proteins. One of the advantages of this module is its involvement in oligomerization, in which it acts as a structural organizer that is not only relatively resistant to proteases but also permits the creation of multivalent supramolecular networks.

Invertebrate data predict an early emergence of vertebrate fibrillar collagen clades and an anti-incest model.

Fibrillar collagens are involved in the formation of striated fibrils and are present from the first multicellular animals, sponges, to humans. Recently, a new evolutionary model for fibrillar collagens has been suggested (Boot-Handford, R. P., Tuckwell, D. S., Plumb, D. A., Farrington Rock, C., and Poulsom, R. (2003) J. Biol. Chem. 278, 31067-31077). In this model, a rare genomic event leads to the formation of the founder vertebrate fibrillar collagen gene prior to the early vertebrate genome duplications and the radiation of the vertebrate fibrillar collagen clades (A, B, and C). Here, we present the modular structure of the fibrillar collagen chains present in different invertebrates from the protostome Anopheles gambiae to the chordate Ciona intestinalis. From their modular structure and the use of a triple helix instead of C-propeptide sequences in phylogenetic analyses, we were able to show that the divergence of A and B clades arose early during evolution because alpha chains related to these clades are present in protostomes. Moreover, the event leading to the divergence of B and C clades from a founder gene arose before the appearance of vertebrates; altogether these data contradict the Boot-Handford model. Moreover, they indicate that all the key steps required for the formation of fibrils of variable structure and functionality arose step by step during invertebrate evolution.