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Concept: Structural proteins

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Fish discards and subproducts may represent an important source of raw material, not only for the food industry, but for other different kind of industries, such as the nutraceutical and cosmetic industries. Collagen, which is mainly obtained from animal skins, is an important structural protein in the animal kingdom having many different applications. It is well known that fish skins constitute a significant subproduct in the fishery industry, especially in the case of some species, where fish skins may represent up to 20% of the total body weight of fish. Peptides from collagen hydrolysates have been described to be useful for preventing skin aging and osteoarthritis, however, the mechanism for these biological activities is not well known. Fibroblasts are the main cell types involved in the collagen synthesis, and in the present work, human dermal fibroblasts have been exposed to the treatment of collagen peptides of two different molecular weight ranges. Results show that higher molecular weight collagen peptides produce higher synthesis of collagen type I mRNA and, therefore, it may suggest that prior molecular weight selection may be an important step to maximize the effect of collagen hydrolysates on collagen type I synthesis by dermal fibroblasts.

Concepts: Protein, Collagen, Extracellular matrix, Fibroblast, Skin, Industry, Type-I collagen, Structural proteins

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Type VII collagen (Col7) is the major component of anchoring fibrils and very important for skin integrity. This is emphasized by the Col7 related skin blistering diseases dystrophic epidermolysis bullosa and epidermolysis bullosa acquisita. Structural data that provides insights into the interaction network of Col7 and thus providing a basis for a better understanding of the pathogenesis of the diseases is missing. We proved that the von-Willebrand-factor A like domain 2 (vWFA2) of Col7 is responsible for type I collagen binding. The interaction has a K(D) value of 90 μM as determined by SPR and is enthalpy driven as derived from the van’t Hoff equation. Furthermore, a hitherto unknown interaction of this domain with type IV collagen was identified. The interaction of vWFA2 with type I collagen is sensitive to the presence of magnesium ions, however, vWFA2 does not contain a magnesium binding site thus magnesium must bind to type I collagen. A lysine residue has been identified to be crucial for type I collagen binding. This allowed localization of the binding site. Mutational analysis suggests different interaction mechanisms in different species and that these interactions might be of covalent nature.

Concepts: Protein, Collagen, Atom, Epidermolysis bullosa, Structural proteins, Epidermolysis bullosa acquisita, Epidermolysis bullosa dystrophica, Van 't Hoff equation

2

Cutis laxa (CL) is a rare disorder affecting elastic fiber formation(1) . The disease is disfiguring and involvement of big vessels in lung and heart often leads to severe complications. CL occurs as an inherited and acquired form, cutis laxa acquisita (CLA). While in the inherited form most mutations have been identified in genes for elastic fiber components like elastin (2) , fibulin-4 (3) , fibulin-5 (4) , or LTBP-4 (5) the pathogenesis of CLA remains poorly understood. Clinically, there often is an association between CLA and paraproteinemia (1) . Deposition of immunoglobulins and complement has been proposed to result in an immune-mediated destruction of elastic fibers (6) . This article is protected by copyright. All rights reserved.

Concepts: Immune system, DNA, Protein, All rights reserved, Copyright, Structural proteins, Cutis laxa, Elastic fiber

0

Nonsurgical treatment such as exercise is the preferred method for management of knee osteoarthritis (OA). A combination of aerobic, muscle strengthening, and flexibility exercises is recommended for older adults. However, effects of the exercise intervention on cartilage metabolism remain unclear. This study used biomarkers to investigate the effects of well-rounded exercise program on cartilage metabolism in 42 women (mean age: 59 years). Participants started a weekly supervised exercise program and continued for 12 weeks. Before and after the program, we measured physical performance on the Timed Up-and-Go Test, 3-Minute Walk Test, and 30-Second Chair Stand Test. We collected serum and urine samples at the start of the program until 24 weeks and measured the concentrations of 4 biomarkers related to type II collagen metabolism: serum cartilage type II procollagen carboxy propeptide (sPIICP), urine C-terminal telopeptide of collagen type II (uCTX-II), urine cleavage of type II collagen by collagenases (uC2C), and serum cartilage oligomeric matrix protein (sCOMP). Participants were divided into pre-OA and OA groups based on X-ray findings. The pre-OA group showed significant increases and decreases in sPIICP and uCTX-II concentrations with improved physical performance, respectively. sCOMP concentrations significantly increased in both groups. The exercise also improved physical performance with no detrimental effect on type II collagen metabolism in the OA group. Thus, well-rounded exercise may not only improve physical capacity but also have beneficial effects on type II collagen metabolism, especially in people without radiological OA.

Concepts: Protein, Collagen, Muscle, Exercise, Cartilage, Test method, Structural proteins, Type-II collagen

0

Dedifferentiation of chondrocytes during cell expansion is one of the barriers in tissue construction for cartilage repair. To understand chondrocyte behavior and improve cell expansion in monolayer culture, this study investigated the effects of morphological changes and cellular aggregation on the maintenance of chondrogenic capacity by observing the expression patterns of chondrogenic (collagen type II and aggrecan) and dedifferentiation (collagen type I) markers. Primary human chondrocytes were cultured on either a polystyrene surface (PS) or a polyamidoamine dendrimer surface with a fifth-generation (G5) dendron structure to create a one-step process of cell expansion and the maintenance of chondrogenic activities prior to the construction of cell sheets.

Concepts: Gene expression, Collagen, Cellular differentiation, Cartilage, Autologous chondrocyte implantation, Chondrocyte, Type-I collagen, Structural proteins

0

Cadmium (Cd) is a toxic metal that damages bone tissue by affecting its mineral and organic components. The organic matrix is mainly (90%) composed of collagen, which determines the biomechanical strength of bone. The aim of this study was to evaluate the effect of zinc (Zn) supplementation (30 or 60 mg l-1) under moderate and relatively high exposure to Cd (5 and 50 mg l-1) on collagen in the rat tibia proximal epiphysis and diaphysis (regions abundant in trabecular and cortical bone, respectively). Significant decrease in collagen type I biosynthesis was found in both regions of the tibia in Cd-treated rats, whereas the supplementation with Zn provided significant protection against this effect. Western blot confirmed the presence of the major type I collagen in the tibia epiphysis and diaphysis, but collagen type II was revealed only in the epiphysis. Acetic acid- and pepsin-soluble collagen concentration in the tibia epiphysis and diaphysis was significantly increased due to the exposure to Cd, whereas the supplementation with Zn protected, partially or totally, from these effects, depending on the used concentration. The supplementation with Zn also provided protection from unfavorable Cd impact on the maturation of the bone collagen, as the ratio of cross-links to monomers was higher compared to the Cd-treated group. This report confirms our previous findings on the preventive action of Zn against harmful effects of Cd on bone, but additionally, and to the best of our knowledge for the first time, explains the possible mechanism of the beneficial influence of this bioelement.

Concepts: Bone, Collagen, Ratio, Zinc, Rat, Type-I collagen, Structural proteins, COL1A2

0

Intra-articular corticosteroid injections (IACI) are commonly used interventions for pain relief in patients with knee osteoarthritis (OA). Biomarkers may be helpful in further elucidating how IACI exert their effect. The aim of this study is to look at the response of biomarkers of cartilage and bone metabolism after IACI in knee OA. Eighty subjects with symptomatic knee OA [45% male, mean age (SD) 64 (11) years] underwent routine knee joint injection with 40 mg triamcinolone acetonide and 4 ml 1% lignocaine. Knee pain (as pain subscale of WOMAC VAS) and biomarkers [C-telopeptides of type-II collagen (uCTX-II), and N-telopeptides of type-I collagen in urine; cartilage oligomeric matrix protein (COMP), hyaluronic acid, N-terminal propeptide of type-IIA collagen, and human cartilage glycoprotein-39 (YKL-40) in serum] were measured at baseline and 3 weeks after IACI. Radiographic severity of disease was evaluated using knee radiographs. Median uCTX-II, a cartilage degradation marker, was lower at 3 weeks post IACI compared with baseline: 306.3 and 349.9 ng/mmol, respectively (p < 0.01), which remained significant after Bonferroni correction. Apart from a weak trend of lower sCOMP post IACI (p = 0.089), other biomarkers showed no change after IACI. Both baseline uCTX-II values and the change in uCTX-II from baseline to 3 weeks post injection correlated with radiographic severity of joint space narrowing, but not osteophyte grade. No association between uCTX-II and pain was observed. This observational study suggests that IACI in knee OA may reduce cartilage degradation in the short term.

Concepts: Protein, Bone, Collagen, Cartilage, Osteoarthritis, Knee, Joint, Structural proteins

0

Tropoelastin, as the monomer unit of elastin, assembles into elastic fibers that impart strength and resilience to elastic tissues. Tropoelastin is also widely used to manufacture versatile materials with specific mechanical and biological properties. The assembly of tropoelastin into elastic fibers or biomaterials is crucially influenced by key submolecular regions and specific residues within these domains. In this work, we identify the functional contributions of two rarely occurring negatively charged residues, glutamate 345 in domain 19 and glutamate 414 in domain 21, in jointly maintaining the native conformation of the tropoelastin hinge, bridge and foot regions. Alanine substitution of E345 and/or E414 variably alters the positioning and interactive accessibility of these regions, as illustrated by nanostructural studies and detected by antibody and cell probes. These structural changes are associated with a lower propensity for monomer coacervation, cross-linking into morphologically and functionally atypical hydrogels, and markedly impaired and abnormal elastic fiber formation. Our work indicates the crucial significance of both E345 and E414 residues in modulating specific local structure and higher-order assembly of human tropoelastin.

Concepts: Materials science, Disability, Structural proteins

0

The annulus fibrosus (AF) of the intervertebral disc (IVD) has a zonal distribution of phenotypically distinct cells. The outer AF (OAF) cells produce an extracellular matrix (ECM) rich in type I collagen with little proteoglycans, whereas the ECM of the inner AF (IAF) has abundant type II collagen and proteoglycans. The inhomogeneous distribution of the ECM in the AF may reflect the complex mechanical forces that the IVD experiences. A bioengineered AF tissue should recapitulate both the inner and outer zones in order to have proper functionality. The aim of this study is to generate multi-lamellated OAF and IAF tissues with ECM compositions that resemble their zonal origin using polycarbonate urethane (PU) scaffolds. It was observed that supplementation of the media with insulin-transferrin-selenium (ITS) and proline yielded tissues with good cellularity. However, IAF cells accumulated only type I collagen, similar to OAF cells. Addition of dexamethasone and sodium pyruvate induced the accumulation of IAF tissues rich in type II collagen and aggrecan, without altering the accumulation of type I collagen in OAF tissues. Dexamethasone stimulated mitochondrial membrane potential in both tissues in the presence of sodium pyruvate, suggesting a relationship between the mitochondrial aerobic respiratory state and dexamethasone signalling during the in vitro-tissue formation by OAF and IAF cells. Inhibition of the glucocorticoid receptor blocked the stimulation of mitochondrial membrane potentials and type II collagen accumulation. In summary, biologically distinct multi-lamellated OAF and IAF tissues can be generated, which will facilitate advancement towards the goal of engineering a biological IVD replacement. This article is protected by copyright. All rights reserved.

Concepts: DNA, Collagen, Extracellular matrix, Golgi apparatus, Organelle, Cellular respiration, Potential, Structural proteins

0

The aim of the present study was to assess the efficacy and safety of the oral administration of Ajuga decumbens extract (ADE) supplement to individuals with knee discomfort associated with physical activity. A randomized, double-blind, placebo-controlled study was conducted using 48 subjects. The subjects were randomly allocated to an ADE diet group (oral administration of ADE-containing diet, n=24) or a placebo group (n=24), and the intervention was conducted for 12 weeks. A total of 22 subjects in the placebo group and 22 subjects in the ADE diet group were assessed to be eligible for assessment of the efficacy of supplement. Knee function was assessed by changes in the scores of the Japanese Knee Osteoarthritis Measure (JKOM) questionnaire and the scores of the Japan Orthopedic Association (JOA) criteria, as well as by analyzing the levels of type II collagen synthesis and degradation biomarkers (procollagen II C-terminal propeptide, cross-linked C-telopeptide of type II collagen, collagen type II cleavage and matrix metalloproteinase-13). Outcomes were measured at the baseline and at 4, 8 and 12 weeks from the start of administration. Subscale II (joint flexion/stiffness) of the JOA criteria was markedly improved in the ADE diet group compared with the placebo group at 8 and 12 weeks during the intervention. Furthermore, in the subgroup analyses using subjects with mild knee discomfort, subscale II (pain/stiffness) and IV (general activities) scores of JKOM were significantly improved (P<0.05) and total JKOM score was markedly improved in the ADE diet group compared with the placebo group at week 8 of the intervention. No adverse effects were identified for the administration of ADE. In conclusion, these observations suggest that the administration of an ADE-containing diet is safe and improves joint function (flexion and stiffness) and general activity in subjects with mild knee discomfort. Therefore, ADE could be a promising candidate as a functional food that is beneficial to joint health.

Concepts: Collagen, Randomized controlled trial, Assessment, Knee, Placebo, Type-I collagen, Structural proteins, Type-II collagen