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Structure and Function of Cartilage
Published in Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi, Articular Cartilage, 2017
Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi
Fibril collagens represent the most prevalent types of collagen with types I, II, and XI being the predominant members. Fibril collagens have unique nonhelical N- and C-terminal domains per type, but share a characteristic central core of approximately 300 nm in length, comprised of a repeating amino acid sequence G-X-Y, with glycine, proline, and hydroxyproline being the most common constituents (van der Rest and Garrone 1991). This amino acid sequence helps the procollagen monomer exhibit a characteristic left-handed helix structure that can then assemble into a right-handed triple helix in the final trimer. Trimer assembly occurs in the lumen of the endoplasmic reticulum and is mediated by molecular chaperones and the C-propeptides. Hydroxylation of the proline in the Y position is required for the necessary folding and stabilization of the helix through a stereoelectronic effect (Kotch et al. 2008) and is dependent on the presence of ascorbic acid as a cofactor for prolyl-4-hydroxylase to convert proline to hydroxyproline. As primates (and guinea pigs) lack the ability to synthesize ascorbic acid, the lack of dietary ascorbic acid results in the disease state of scurvy. Without ascorbic acid, the hydroxyproline cannot be formed, resulting in procollagen being unable to exit the endoplasmic reticulum, and, thus, the lack of new collagen fibrils being synthesized.
Biomolecules and Tissue Properties
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
Studies involving molecular modeling and the production of triple helical polypeptides have shown that changes in the glycine–proline–hydroxyproline repeat alter the appearance and stability of the triple helix. The triple helix requires glycine to be present every third amino acid because it is the only amino acid small enough to be in the center of the super helix. Proline and hydroxyproline play important roles in the stability of the collagen triple helix, stabilizing structurally and thermally. The absence of these amino acids has been shown to cause a disruption in the collagen triple helix.
Natural Polymers as Components of Blends for Biomedical Applications
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
Collagen is the main protein in an animal’s body. This structural protein forms molecular lines that strengthen the tendons and vast, resilient sheets that support the skin and internal organs. Hard tissues such as bones and teeth are made of collagen with the addition of mineral crystals, mainly hydroxyapatites. There are 20 genetically distinct collagens in the collagen family. Collagen type I, type II, and type III are fibril-forming ones: type I (skin, tendon, and bone), type II (cartilage), and type III (skin and vasculature) [63–69]. In each collagen chain, there are 1000 amino acids, which form the sturdy structure by a repeated sequence of three amino acids. Every third amino acid is glycine, a small amino acid that fits perfectly inside the helix. In other positions in the chain, the following are located: proline and a modified version of proline, hydroxyproline. It is believed that hydroxyproline is responsible for collagen stability because of additional hydrogen bonds formed by the OH group. Hydrogen bonds play the main role in the stabilization of the collagen triple helix [64]. Each collagen molecule undergoes a strong molecular connection with neighboring collagen molecules by hydrogen bonding and other crosslinks [63–65,67–69]. Highly crosslinked collagen is usually insoluble in water [70]. Additional crosslinking of collagen can be made by exposure of collagen to UV irradiation [71].
Spectroscopic imaging: Nuclear magnetic resonance and Raman spectrometry for the detection of collagen cross-linking from giant squid mantle, fin, and tentacle tissues
Published in Instrumentation Science & Technology, 2018
Héctor M. Sarabia-Sainz, Wilfrido Torres-Arreola, Josafat Marina Ezquerra-Brauer
Collagen fractions were purified using a cation-exchange column chromatography as previously reported.[20] The conditions were as follows: a HiTrap CM FF column was equilibrated with 50 mM sodium acetate/6 M urea (pH 4.8). A linear gradient was used from 0 to 0.5 M NaCl at a flow rate of 1 mL/min. Samples for pyridinoline analysis were dialyzed in 0.05 M acetic acid. The results are expressed as collagen percentage based on hydroxyproline content in the collagen fractions.[23]
Functionalized acellular periosteum guides stem cell homing to promote bone defect repair
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Guoqing Zhu, Yidi Zhou, Yichang Xu, Lingjun Wang, Meng Han, Kun Xi, Jincheng Tang, Ziang Li, Yu Kou, Xindie Zhou, Yu Feng, Yong Gu, Liang Chen
The hydroxyproline content in NP and DP was detected using a hydroxyproline kit, which indirectly indicated the collagen content. Six samples from each group were weighed, recorded, then cut into pieces; these sample pieces were placed in test tubes, added to 1 ml of 6 mol/L hydrochloric acid solution, and hydrolyzed in a 95 °C water bath for 5 h. The hydroxyproline kit was used to detect the hydroxyproline content and calculate the collagen content in the test sample, according to the content of hydroxyproline in collagen (13.4%).
Preparation of hybrid meniscal constructs using hydrogels and acellular matrices
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Gizem Zihna, Bengisu Topuz, Gülçin Günal, Halil Murat Aydin
In the current study, acellular cross-linked hybrid scaffolds that can mimic meniscus tissue were developed to be used in ideal meniscus repair. Firstly, whole meniscus tissue decellularization was carried out by freezing and thawing cycles, physical agitation with osmotic shock, enhancing penetration with the help of trypsin enzyme, and keeping the concentration ratio of the SDS chemical agent low. Crapo et al. said that for effective decellularization, the criteria that are the absence of cell nuclei in histological examinations such as H&E and DAPI, the remaining double-stranded DNA not exceeding 200 base pairs, and the double-stranded DNA less than 50 ng per mg of dry tissue should be met [13]. Our results met these criteria showing that found to be under 50 ng/per mg dry weight of DNA content from biochemical assay and found to be cell nuclei-free ECM from histology studies. From the data in the literature, it is known that meniscus cells are generally clustered between collagen fibrils [32]. The hypothesis that cells are exposed and removed more easily with the decrease of GAGs attached to these structures with the loosening of collagen fibrils at the end of the decellularization process has been confirmed in histology studies where no cell nuclei were observed around collagen fibers. Stabile et al. reported a 55% DNA reduction in meniscal decellularization with Trypsin/EDTA followed by Triton X-100 agents [16]. In the decellularized group, after physical pre-treatment, Trypsin/EDTA and SDS agents were applied at increasing temperatures, resulting in an 82% reduction in genomic DNA. The amount of collagen in the tissue was calculated based on the amount of hydroxyproline. The relative increase in collagen content in the decellularized tissue is associated with increasing a percentage of dry weight after decellularization due to the loss of cells and other cellular proteins [33]. Considering the decellularization studies in the literature, GAG reduction was expected in the groups due to SDS treatment [15, 34]. The decrease in the number of glycosaminoglycans was tried to be kept to a minimum by reducing the SDS ratio to 0.5% (w/v). In brief, the treatment time and concentration of the SDS agent applied, compared with the literature, were reduced and it was shown that this protocol was effective in preserving the organization of the meniscus tissue. Moreover, thanks to the loosen matrix of decellularized tissue gained the ability of cross-linking of the meniscus scaffold. In this study, it was also aimed to improve the damaged 3 D structure of decellularized meniscus tissue by impregnating gel into decellularized matrix.