Mutable collagenous tissue: A concept generator for biomimetic materials and devices

Echinoderms (starfish, sea-urchins and their close relations) possess a unique type of collagenous tissue that is innervated by the motor nervous system and whose mechanical properties, such as tensile strength and elastic stiffness, can be altered in a time frame of seconds. Intensive research on echinoderm ‘mutable collagenous tissue’ (MCT) began over 50 years ago, and over 20 years ago, MCT first inspired a biomimetic design. MCT, and sea-cucumber dermis in particular, is now a major source of ideas for the development of new mechanically adaptable materials and devices with applications in diverse areas including biomedical science, chemical engineering and robotics. In this review, after an up-to-date account of present knowledge of the structural, physiological and molecular adaptations of MCT and the mechanisms responsible for its variable tensile properties, we focus on MCT as a concept generator surveying biomimetic systems inspired by MCT biology, showing that these include both bio-derived developments (same function, analogous operating principles) and technology-derived developments (same function, different operating principles), and suggest a strategy for the further exploitation of this promising biological resource

Mechanical properties of the compass depressors of the sea-urchin Paracentrotus lividus (Echinodermata, Echinoidea) and the effects of enzymes, neurotransmitters and synthetic tensilin-like protein

The compass depressors (CDs) of the sea-urchin lantern are ligaments consisting mainly of discontinuous collagen fibrils associated with a small population of myocytes. They are mutable collagenous structures, which can change their mechanical properties rapidly and reversibly under nervous control. The aims of this investigation were to characterise the baseline (i.e. unmanipulated) static mechanical properties of the CDs of Paracentrotus lividus by means of creep tests and incremental force-extension tests, and to determine the effects on their mechanical behaviour of a range of agents. Under constant load the CDs exhibited a three-phase creep curve, the mean coefficient of viscosity being 561±365 MPa.s. The stress-strain curve showed toe, linear and yield regions; the mean strain at the toe-linear inflection was 0.86±0.61; the mean Young's modulus was 18.62±10.30 MPa; and the mean tensile strength was 8.14±5.73 MPa. Hyaluronidase from Streptomyces hyalurolyticus had no effect on creep behaviour, whilst chondroitinase ABC prolonged primary creep but had no effect on secondary creep or on any force-extension parameters; it thus appears that neither hyaluronic acid nor sulphated glycosaminoglycans have an interfibrillar load transfer function in the CD. Acetylcholine, the muscarinic agonists arecoline and methacholine, and the nicotinic agonists nicotine and 1-[1-(3,4-dimethyl-phenyl)-ethyl]-piperazine produced an abrupt increase in CD viscosity; the CDs were not differentially sensitive to muscarinic or nicotinic agonists. CDs showed either no, or no consistent, response to adrenaline, L-glutamic acid, 5-hydroxytryptamine and γ-aminobutyric acid. Synthetic echinoid tensilin-like protein had a weak and inconsistent stiffening effect, indicating that, in contrast to holothurian tensilins, the echinoid molecule may not be involved in the regulation of collagenous tissue tensility. We compare in detail the mechanical behaviour of the CD with that of mammalian tendon and highlight its potential as a model system for investigating poorly understood aspects of the ontogeny and phylogeny of vertebrate collagenous tissues.(undefined)info:eu-repo/semantics/publishedVersio

Pluripotent versus reprogrammed cells: cell plasticity in echinoderm regeneration

Echinoderms display remarkable regenerative capabilities and offer a variety of models to study this phenomenon widely distributed throughout the Phylum. Although their regenerative phenomena have been traditionally attributed to two different mechanisms (i.e. epimorphosis and morphallaxis), the true origin and fate of the involved cells are still unclear. An up-to-date overview of cell recruitment processes in the different echinoderm classes is here provided in order to define the state of the art, including the main unsolved issues, as well as the necessary future steps to cover the knowledge gap. Among stellate echinoderms, crinoids are the only group clearly displaying the recruitment of morphologically undifferentiated cells stocked in the stump tissues (i.e. coelomic canals and brachial nerve): these undifferentiated cells actively migrate to form a true blastema where they undergo proliferation and differentiation up to to regenerate the lost tissues. Reprogramming of differentiated cells occurs only in stress conditions. In contrast, a true regenerative blastema is missing in brittle stars and starfish, which apparently mainly rely on recruitment of dedifferentiated cells from mature tissues. In starfish, dedifferentiation is massively employed at the level of muscle tissues, also in location far from the wound site. In both these classes progenitor-like cells are provided and recruited via epithelial-mesenchymal transition (EMT) from coelomic epithelium. In sea cucumbers neural and intestinal regeneration are the main process under investigation. In the former, the absence of \u201cstemness\u201d marker in the transcriptome suggests that radial nerve cord regeneration depends on dedifferentiation of the supporting glial cells that re-differentiate in both the same cytotype and new neurons. Myocyte dedifferentiation markedly occurs during gut regeneration. In sea urchins, damaged test and broken spines are reformed through dedifferentiation of stump cells with only minor local cell proliferation, whereas totally removed spines are regenerated via undifferentiated (pluripotent) cells. Overall, echinoderm regeneration appear mainly to rely on dedifferentiation phenomena rather than recruitment of pluripotent cells already stocked in the stump tissues, the exact origin, identity and fate of the involved cells being still unknown in most cases. Echinoderm tissues, especially coelomic epithelium and muscles, show a high potential of plasticity in terms of cell differentiation/dedifferentiation and activity (proliferation, migration), and EMT plays key roles in this plasticity. Cell tracking coupled to molecular and microscopy approaches will be strongly needed to unravel in detail the strikingly effective cellular mechanisms and pathways (from cell origin to fate) employed by echinoderms in their regeneration processes

Triphenyltin alters androgen metabolism in the sea urchin Paracentrotus lividus

10 pages, 5 figures.-- PMID: 16846652 [PubMed].-- Printed version published Sep 12, 2006.Androgen metabolism (androstenedione and testosterone) has been assessed in the digestive tube and gonads of the echinoderm Paracentrotus lividus exposed to different concentrations of the biocide triphenyltin (TPT) in a semi-static water regime for 4 weeks. Key enzymatic activities involved in both synthesis and metabolism of androgens, namely 17β-hydroxysteroid dehydrogenases (17β-HSDs), 3β-HSDs, 5α-reductases, P450-aromatase, palmitoyl-CoA:testosterone acyltransferases (ATAT) and testosterone sulfotransferases (SULT), were investigated in digestive tube and/or gonads of control and TPT-exposed specimens in an attempt to see whether androgen metabolism was altered by exposure. In agreement with previous data for vertebrates, exposure to TPT led to a concentration dependent decrease of P450-aromatase that was statistically significant at the highest TPT concentration tested (225 ng/L). Additionally, increased metabolism of testosterone to form dihydrotestosterone (DHT) and 5α-androstane-3β,17β-diol was observed, suggesting increased 5α-reductase activity in the gonads of TPT-exposed individuals. Interestingly, exposure to TPT induced testosterone conjugating activities in organisms exposed to medium (SULT) and high (ATAT and SULT) TPT concentrations. Despite the changes of androgen metabolizing enzymes, testosterone levels in gonads remained rather stable. In contrast, an increase in testosterone and a concomitant decrease in estradiol were observed in the coelomic fluid of TPT-exposed organisms. Overall, the data indicate the ability of TPT to modulate androgen metabolism and circulating steroid levels in P. lividus and suggest the existence of regulatory mechanisms to maintain stable endogenous levels of testosterone in gonads. This study also contributes to a better knowledge of echinoderm endocrinology.The study was supported by the EU Project COMPRENDO (EVK1-CT-2002-00129).Peer reviewe

Effects of exposure to ED contaminants (TPT-Cl and Fenarimol)on crinoid echinoderms: comparative analysis of regenerative development and correlated steroid levels

13 pages, 7 figures.Regenerative phenomena reproduce developmental processes in adult organisms and are regulated by neuro-endocrine mechanisms. They can therefore provide sensitive tests for monitoring the effects of exposure to endocrine disrupter contaminants (EDs) which can be bioaccumulated by the organisms causing dysfunctions in steroid hormone metabolism and activities and affecting reproduction and development. Echinoderms are prime candidates for this new ecotoxicological approach, since (1) they offer unique models to study physiological regenerative processes and (2) in echinoderms vertebrate-type steroids can be synthesized and used as terminal hormones along the neuro-endocrine cascades regulating reproductive, growth and developmental processes. We are currently exploring the effects on the regenerative potential of echinoderms of different classes of compounds that are well known to have ED activity. The present paper focuses on the possible effects of well-known compounds with suspected androgenic activity such as TPT-Cl (Triphenyltin-chloride) and Fenarimol [(± )-2,4-dichloro-α-(pyrimidin-5-yl) benzhydryl alcohol]. The selected test-species is the crinoid Antedon mediterranean a tractable and sensitive benthic filter-feeding species which represents a valuable experimental model for investigation on the regenerative process from the macroscopic to the molecular level. The present investigation employs an integrated approach which combines exposure experiments and biological analysis utilizing microscopy, immunocytochemistry and biochemistry. The experiments were carried out on experimentally induced arm regenerations in semistatic controlled conditions with exposure concentrations comparable to those of moderately polluted coastal zones. The bulk of results obtained so far provide indications of significant sublethal effects from exposure to TPT-C1 and Fenarimol and mechanisms of toxicity related to developmental physiology, which are associated with variations in steroid levels in the animal tissues. The results indicate that these two substances (1) affect growth and development by interfering with the same basic cellular mechanisms of regeneration, such as cell proliferation, migration and differentiation/dedifferentiation, which are possibly controlled by steroid hormones; and (2) can induce a number of significant modifications in the timing, modalities and pattern of arm regeneration, which may involve the activation of cell mechanisms related to steroid synthesis/metabolism.The present work has received financial support from the EU (COMPRENDO Project n EVK1-CT-2002-00129). The authors are particularly grateful to Dr Ulrike Shulte-Oehlmann for her valuable coordinating activity and to all the partners of the COMPRENDO project for their direct or indirect support and advice. Special thanks are addressed to Drs Simona Ceriani and Angelita Doria for their valuable help and technical assistance. All the experiments carried out for the research work are in accord with the current laws of our country. The authors are grateful to the anonymous reviewers for their invaluable suggestions and careful revision of the manuscript.Peer reviewe