Effect of matrix metalloproteinase on autolysis of sea cucumber Stichopus japonicus

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.

Extracellular Matrix of Echinoderms

This review considers available data on the composition of the extracellular matrix (ECM) in echinoderms. The connective tissue in these animals has a rather complex organization. It includes a wide range of structural ECM proteins, as well as various proteases and their inhibitors. Members of almost all major groups of collagens, various glycoproteins, and proteoglycans have been found in echinoderms. There are enzymes for the synthesis of structural proteins and their modification by polysaccharides. However, the ECM of echinoderms substantially differs from that of vertebrates by the lack of elastin, fibronectins, tenascins, and some other glycoproteins and proteoglycans. Echinoderms have a wide variety of proteinases, with serine, cysteine, aspartic, and metal peptidases identified among them. Their active centers have a typical structure and can break down various ECM molecules. Echinoderms are also distinguished by a wide range of proteinase inhibitors. The complex ECM structure and the variety of intermolecular interactions evidently explain the complexity of the mechanisms responsible for variations in the mechanical properties of connective tissue in echinoderms. These mechanisms probably depend not only on the number of cross-links between the molecules, but also on the composition of ECM and the properties of its proteins.

Characteristics of the Intestine Extracts and Their Effect on the Crude Collagen Fibers of the Body Wall from Sea Cucumber Apostichopus japonicus

Sea cucumbers Apostichopus japonicus will vomit their intestines during certain stimulations, and the collagen of the body wall will then be degraded. To define the effect of the sea cucumber intestine extracts on the body wall, the intestinal extracts and crude collagen fibers (CCF) of sea cucumber A. japonicus were prepared. According to the gelatin zymography, the type of endogenous enzymes in intestinal extracts were mainly serine endopeptidases with optimal activities at pH 9.0 and 40 °C. According to the rheology results, the viscosity of 3% CCF decreased from 32.7 Pa·s to 5.3 Pa·s by adding intestine extracts. The serine protease inhibitor phenylmethanesulfonyl fluoride inhibited the activity of intestinal extracts and increased the viscosity of collagen fibers to 25.7 Pa·s. The results proved that serine protease in the intestinal extracts participated in the process of body wall softening in sea cucumbers.

Relationships of Matrix Metalloproteinase 1 and a Tissue Inhibitor of Metalloproteinase to Collagen Metabolism in Haliotis discus hannai

In response to physical, chemical, and/or biological stimuli, considerable tissue self-degradation occurs in abalone, causing severe post-harvest quality loss. During this process, the extracellular matrix (ECM) is greatly degraded by endogenous proteases. The main component of the ECM is collagen, primarily type I collagen. Although the activity of matrix metalloproteinases (MMPs), which can specifically degrade collagen, is precisely regulated by tissue inhibitors of MPs (TIMPs), indicating that MMPs and TIMPs play crucial roles in the regulation of tissue self-degradation, few studies have reported the interaction between MMPs and TIMPs. In this study, we reveal collagenases to participate in postmortem tissue self-degradation of Haliotis discus hannai by degrading type I collagen. The recombinant MMP-1 catalytic domain (rMMP1c) of abalone with high purity and enzyme activity is expressed using a prokaryotic expression system. The optimum temperature and pH for rMMP1c are 37 °C and 7.0, respectively. The thermal denaturation temperature of rMMP1c is 67.0 ± 0.9 °C. Ethylenediamine tetraacetic acid (EDTA) and 1,10-phenanthroline can completely inhibit rMMP1c activity, while Ba²⁺, Ca²⁺, and Mg²⁺ can significantly elevate it. TIMP is also expressed using HEK 293F cells. Recombinant TIMP (rTIMP) shows good inhibitory activity toward rMMP1c. Inhibition kinetics analyses reveal rTIMP to be a competitive inhibitor of rMMP1c. Biolayer interferometry reveals that rTIMP can effectively bind with rMMP1c, with an equilibrium dissociation constant value of 263 nM. rMMP1c effectively degrades type I collagen γ-β-α chains in turn, and rTIMP can significantly inhibit rMMP1c degradation activity. These results provide a theoretical basis for the study of MMP and TIMP interaction and elucidate the possible mechanism for abalone tissue self-degradation.

Effects of collagenase type I on the structural features of collagen fibres from sea cucumber (Stichopus japonicus) body wall

The autolysis of sea cucumber is caused by depolymerisation of collagen fibres and unfolding of fibrils. In order to highlight the role of collagenase in sea cucumber autolysis, collagen fibres from sea cucumber were hydrolysed with collagenase type I. Electron microscopy (EM) results indicated the collagenase caused partial depolymerisation of collagen fibres into fibrils due to the fracture of proteoglycan interfibrillar bridges, as well as uncoiling of collagen fibrils. Chemical analysis and SDS-PAGE both indicated collagenase induced a time-dependent release of glycosaminoglycans (GAGs) and soluble proteins, which further demonstrated the degradation of proteoglycan interfibrillar bridges. Collagenase also degraded collagens by releasing soluble hydroxyproline (Hpy), with the dissolution rate of Hyp reaching 11.11% after 72 h. Fourier transform infrared analysis showed that collagenase caused the reduction of intermolecular interactions and structural order of collagen. Hence, collagenase participated in the autolysis of sea cucumber by deteriorating both macromolecular and monomeric collagens.

RNA Sequencing Analysis to Capture the Transcriptome Landscape during Tenderization in Sea Cucumber Apostichopus japonicus

Sea cucumber (Apostichopus japonicus) is an economically significant species in China having great commercial value. It is challenging to maintain the textural properties during thermal processing due to the distinctive physiochemical structure of the A. japonicus body wall (AJBW). In this study, the gene expression profiles associated with tenderization in AJBW were determined at 0 h (CON), 1 h (T_1h), and 3 h (T_3h) after treatment at 37 °C using Illumina HiSeq™ 4000 platform. Seven-hundred-and-twenty-one and 806 differentially expressed genes (DEGs) were identified in comparisons of T_1h vs. CON and T_3h vs. CON, respectively. Among these DEGs, we found that two endogenous proteases-72 kDa type IV collagenase and matrix metalloproteinase 16 precursor-were significantly upregulated that could directly affect the tenderness of AJBW. In addition, 92 genes controlled four types of physiological and biochemical processes such as oxidative stress response (3), immune system process (55), apoptosis (4), and reorganization of the cytoskeleton and extracellular matrix (30). Further, the RT-qPCR results confirmed the accuracy of RNA-sequencing analysis. Our results showed the dynamic changes in global gene expression during tenderization and provided a series of candidate genes that contributed to tenderization in AJBW. This can help further studies on the genetics/molecular mechanisms associated with tenderization.