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The Cause of Pressure Sores
Published in J G Webster, Prevention of Pressure Sores, 2019
Section 1.6 describes the importance and the formation of collagen. SCI persons form unstable collagen due to the following mechanism. The water bridges that hydroxyproline forms with other amino acids in the collagen helix are the main factor in establishing both the mechanical and thermal stability of the collagen fibrils (Traub 1974, Nemethy and Scheraga 1986). Insensate skin has a greatly decreased amino acid content per unit weight. If this interfered with the proper formation of water bridges, the skin would become weakened due to resisting mechanical insults. SCI persons have a reduced blood supply below the level of injury that could reduce the supply of nutrients to the tissues and decrease the availability of the enzyme cofactors, ascorbic acid, and molecular oxygen (Hunt 1978). The resulting localized malnutrition would alter the biosynthesis of the collagen molecule thus forming defective collagen fibrils.
Anatomy, physiology and disease
Published in C M Langton, C F Njeh, The Physical Measurement of Bone, 2016
In addition to these growth factors, the bone matrix also contains skeletal specific proteins such as osteocalcin, and other connective tissue molecules like osteonectin and osteopontin, derived from differentiated osteoblasts [43–46]. But, by far, the major structural component of the skeletal matrix is collagen type I, a large protein composed of three separate peptide chains organized in parallel and synthesized by mature osteoblasts (see section 1.5). In fact, 90% of unmineralized osteoid is collagen type I [47, 48]. Individual subunits of the collagen helix are connected terminally to each other by cross-linking amino acids, added as a post-translational modification of the entire collagen molecule. During resorption, cross-links are catalysed initially, and are subsequently liberated from the matrix proper [43]. Some of these enter the circulation as telopeptide fragments, and are eventually filtered by the renal tubules. Both qualitative and quantitative defects in collagen synthesis, modification or mineralization can lead to chronic disorders characterized by enhanced skeletal fragility, such as osteoporosis.
Molecular Structure and Functions of Collagen
Published in Marcel E. Nimni, Collagen, 1988
Marcel E. Nimni, Robert D. Harkness
Mammalian collagenases display a great deal of specificity by hydrolyzing a single polypeptide bond on each chain of the native triple-stranded collagen helix. A significant amount of work has been devoted to understanding the unique characteristics of the cleavage site. The cleavage site of the α 1 chain was identified by electron microscopy and later by sequence analysis.191,193,194
Vascular and extracellular matrix remodeling by physical approaches to improve drug delivery at the tumor site
Published in Expert Opinion on Drug Delivery, 2020
Sara Gouarderes, Anne-Françoise Mingotaud, Patricia Vicendo, Laure Gibot
It is known that ROS induce ECM remodeling by different mechanisms as an increased expression of MMP-2,-7,-9 and degradation of glycosaminoglycans by hyaluronidase and heparinase [177]. Because cold plasma generates a wide variety of ROS and RNS, it is of prime important to study ECM remodeling after exposure to plasma. Using circular dichroism on bovine type I collagen exposed to cold helium-plasma, Keyvani et al. revealed alterations in the helical structure of dissolved collagen over time, such as oxidation of many structural residues and denaturation although the secondary structure was not damaged [178]. Thus, they demonstrated that the structure of collagen treated with cold atmospheric plasma undergoes oxidation and denaturation. Circular dichroism spectra indicated that 68% of bovine type I collagen helix structures were denatured after a 30 s nonthermal argon plasma treatment, which revealed to be very effective in loosening collagen structures [179]. On the contrary, another study analyzing the physical structure of the bovine type I collagen by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy to check the integrity of the triple helical domain revealed that corona ambient air plasma jet stabilized the collagen structure without altering the triple helical structure [180]. As for many therapeutic strategies, cold atmospheric plasma effects revealed to be dose-dependent [181,182]. For example, Shi et al. suggested that low doses of plasma enhance fibroblasts viability and collagen synthesis while high doses can inhibit them [183]. It seems therefore that plasma has dual effects. Thus, it makes it possible to tune cell fate through modulating the plasma dose for both research and therapeutic purposes but it also appears critical to first tune the parameters according to the desired therapeutic outcome before the application in order to prevent deleterious side effects.
Nicotinamide extrudates as novel anti-aging and collagen promoting platform: a comparative cosmeceutical study versus the gel form
Published in Pharmaceutical Development and Technology, 2020
Abdullah Alyoussef, Maha Nasr, Rania F. Ahmed, Omar A. H. Ahmed Farid, Rofanda Bakeer, Hrushikesh Karandikar, Anant Paradkar
Collagen is the largest and most prevalent protein in the body, and it provides strength, rigidity, and flexibility of connective tissue (Salvia-Trujillo et al. 2016). The physiological changes that occur in skin following exposure to various internal and external factors may interrelate and influence one another. Skin damage is correlated to the increased levels of matrix metalloproteinases which can break down collagen, in addition to impaired transforming growth factor (TGF)-β signaling, which may decrease collagen deposition as well (Aldag et al. 2016). Collagen is made of amino acids, in which glycine is a main constituent of all collagen subtypes and it plays an important role in stabilizing the collagen helix, hence facilitating hydrogen bonding and the formation of intermolecular cross-links. Along with glycine, proline and HPro are also abundant constituents of collagen. Both amino acids are implicated in the stabilization of the triple helix, HPro even more so than proline. The uniqueness of the chemical structure of collagen is due to the unusual abundance of glycine, proline, and HPro in the repeated form of tripeptides. On the molar basis, collagen contains 1/3 glycine, 0.7/3 proline plus HPro, and 1.3/3 other amino acids. Therefore, glycine, proline and HPro contribute to 57% of total amino acids in collagen. Therefore, our current study focused on the assessment of their content upon application of NIC gels and extrudates. As could be inferred from the results, the application of NIC extrudates for 7 days was able to significantly increase the levels of glycine and HPro in the skin, hence providing an evidence for their better collagen promoting nature. Worthy to note is that the gel was only able to significantly increase the glycine level in male rats compared to female rats, while extrudates managed to significantly increase its level in both sexes, which could be attributed to the physiological and morphological differences between male and female rats. It was reported that the number of epidermal layers in male rats in terms of thickness was almost double those of female rats (Wells et al. 2010). This created a better depot for NIC in the epidermal layer and prolonged its presence in the skin, and this correlated with the increased glycine levels. On the other hand, extrudates were able to increase glycine significantly in both sexes since they are working by a different mechanism than that of the gel, depending on occlusion and skin hydration rather than mere skin adhesion. This finding further confirms the superiority of NIC extrudates compared to the gel formulation.