title: Ultrastructural and biochemical characterization of mechanically adaptable collagenous structures in the edible sea urchin Paracentrotus lividus.
abstract: The viscoelastic properties of vertebrate connective tissues rarely undergo significant changes within physiological timescales, the only major exception being the reversible destiffening of the mammalian uterine cervix at the end of pregnancy. In contrast to this, the connective tissues of echinoderms (sea urchins, starfish, sea cucumbers, etc.) can switch reversibly between stiff and compliant conditions in timescales of around a second to minutes. Elucidation of the molecular mechanism underlying such mutability has implications for the zoological, ecological and evolutionary field. Important information could also arise for veterinary and biomedical sciences, particularly regarding the pathological plasticization or stiffening of connective tissue structures. In the present investigation we analyzed aspects of the ultrastructure and biochemistry in two representative models, the compass depressor ligament and the peristomial membrane of the edible sea urchin Paracentrotus lividus, compared in three different mechanical states. The results provide further evidence that the mechanical adaptability of echinoderm connective tissues does not necessarily imply changes in the collagen fibrils themselves. The higher glycosaminoglycan (GAG) content registered in the peristomial membrane with respect to the compass depressor ligament suggests a diverse role of these molecules in the two mutable collagenous tissues. The possible involvement of GAG in the mutability phenomenon will need further clarification. During the shift from a compliant to a standard condition, significant changes in GAG content were detected only in the compass depressor ligament. Similarities in terms of ultrastructure (collagen fibrillar assembling) and biochemistry (two alpha chains) were found between the two models and mammalian collagen. Nevertheless, differences in collagen immunoreactivity, alpha chain migration on SDS-PAGE and BLAST alignment highlighted the uniqueness of sea urchin collagen with respect to mammalian collagen.
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy. Electronic address: alice.barbaglio@unimi.it.
authors.forename: Alice
authors.initials: A
authors.lastname: Barbaglio
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Tricarico
authors.affiliation: Instituto de Engenharia Biomédica, University of Porto, Rua do Campo Alegre, 823, Porto 4150-180, Portugal.
authors.forename: Ana R
authors.initials: AR
authors.lastname: Ribeiro
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Di Benedetto
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Barbato
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Desirèe
authors.initials: D
authors.lastname: Dessì
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Fugnanesi
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Magni
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Mosca
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Michela
authors.initials: M
authors.lastname: Sugni
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bonasoro
authors.affiliation: Instituto de Engenharia Biomédica, University of Porto, Rua do Campo Alegre, 823, Porto 4150-180, Portugal.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Barbosa
authors.affiliation: Department of Life Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, UK.
authors.forename: Iain C
authors.initials: IC
authors.lastname: Wilkie
authors.affiliation: Department of Biosciences, University of Milan, Via Celoria 26, Milan 20133, Italy.
authors.forename: M Daniela
authors.initials: MD
authors.lastname: Candia Carnevali
mesh_terms: D000818:Animals; D003094:Collagen / Q000737:chemistry / Q000648:ultrastructure; D003238:Connective Tissue / Q000033:anatomy & histology / Q000737:chemistry / Q000648:ultrastructure; D007150:Immunohistochemistry; D047328:Paracentrotus / Q000033:anatomy & histology* / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D003094:Collagen
keywords: Collagen; Echinoderm; Glycosaminoglycans; Mutable collagenous tissue; Sea urchin