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Osteoarthritis (OA) is a multifactorial joint disease characterized by articular cartilage degradation. Risk factors for OA include joint trauma, obesity, and inflammation, each of which can affect joint health independently, but their interaction and the associated consequences of such interaction were largely unexplored. Here, we studied compositional and structural alterations in knee joint cartilages of Sprague-Dawley rats exposed to two OA risk factors: joint injury and diet-induced obesity. Joint injury was imposed by surgical transection of anterior cruciate ligaments (ACLx), and obesity was induced by a high fat/high sucrose diet. Depth-dependent proteoglycan (PG) content and collagen structural network of cartilage were measured from histological sections collected previously in Collins et al.. (2015). We found that ACLx primarily affected the superficial cartilages. Compositionally, ACLx led to reduced PG content in lean animals, but increased PG content in obese rats. Structurally, ACLx caused disorganization of collagenous network in both lean and obese animals through increased collagen orientation in the superficial tissues and a change in the degree of fibrous alignment. However, the cartilage degradation attributed to joint injury and obesity was not necessarily additive when the two risk factors were present simultaneously, particularly for PG content and collagen orientation in the superficial tissues. Interestingly, sham surgeries caused a through-thickness disorganization of collagen network in lean and obese animals. We conclude that the interactions of multiple OA risk factors are complex and their combined effects cannot be understood by superposition principle. Further research is required to elucidate the interactive mechanism between OA subtypes. [ABSTRACT FROM AUTHOR]

Simple Summary: Pancreatic tumours present significant treatment challenges due to their resistance to chemotherapy and complex tumour microenvironment. Choosing the appropriate preclinical models and understanding how their characteristics affect drug delivery to the tumours is essential for designing clinically relevant experiments. This study investigates pancreatic tumours growing orthotopically or subcutaneously and presents the properties of their tumour microenvironments and their impacts on drug delivery. Pancreatic ductal adenocarcinoma (PDAC) remains a challenging malignancy, mainly due to its resistance to chemotherapy and its complex tumour microenvironment characterised by stromal desmoplasia. There is a need for new strategies to improve the delivery of drugs and therapeutic response. Relevant preclinical tumour models are needed to test potential treatments. This paper compared orthotopic and subcutaneous PDAC tumour models and their suitability for drug delivery studies. A novel aspect was the broad range of tumour properties that were studied, including tumour growth, histopathology, functional vasculature, perfusion, immune cell infiltration, biomechanical characteristics, and especially the extensive analysis of the structure and the orientation of the collagen fibres in the two tumour models. The study unveiled new insights into how these factors impact the uptake of a fluorescent model drug, the macromolecule called 800CW. While the orthotopic model offered a more clinically relevant microenvironment, the subcutaneous model offered advantages for drug delivery studies, primarily due to its reproducibility, and it was characterised by a more efficient drug uptake facilitated by its collagen organisation and well-perfused vasculature. The tumour uptake seemed to be influenced mainly by the structural organisation and the alignment of the collagen fibres and perfusion. Recognising the diverse characteristics of these models and their multifaceted impacts on drug delivery is crucial for designing clinically relevant experiments and improving our understanding of pancreatic cancer biology. [ABSTRACT FROM AUTHOR]

In the present research, the enzyme-facilitated collagen from sea eel (Muraenesox cinereus) swim bladder was isolated, and the collagen characteristics were analyzed. Then, the collagen sponge was prepared and its potential mechanism in promoting skin wound healing in mice was further investigated. Collagen was obtained from the swim bladder of sea eels employing the pepsin extraction technique. Single-factor experiments served as the basis for the response surface method (RSM) to optimize pepsin concentration, solid-liquid ratio, and hydrolysis period. With a pepsin concentration of 2067 U/g, a solid-liquid ratio of 1:83 g/mL, and a hydrolysis period of 10 h, collagen extraction achieved a yield of 93.76%. The physicochemical analysis revealed that the extracted collagen belonged to type I collagen, and the collagen sponge displayed a fibrous structure under electron microscopy. Furthermore, in comparison to the control group, mice treated with collagen sponge dressing exhibited elevated activities of superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-Px), and decreased levels of malondialdehyde (MDA), interleukin (IL)-1β, interleukin (IL)-6, and tumor necrosis factor (TNF)-α. The collagen sponge dressing effectively alleviated inflammation in the wound area, facilitating efficient repair and rapid healing of the skin tissue. During the initial phase of wound healing, the group treated with collagen sponge dressing exhibited an enhancement in the expressions of cluster of differentiation (CD)31, epidermal growth factor (EGF), transforming growth factor (TGF)-β1, and type I collagen, leading to an accelerated rate of wound healing. In addition, this collagen sponge dressing could also downregulate the expressions of CD31, EGF, and type I collagen to prevent scar formation in the later stage. Moreover, this collagen treatment minimized oxidative damage and inflammation during skin wound healing and facilitated blood vessel formation in the wound. Consequently, it exhibits significant potential as an ideal material for the development of a skin wound dressing. [ABSTRACT FROM AUTHOR]

The review summarizes information on possibilities of plant preparations use for collagen structure and metabolism disturbances correction. Biologically active compounds of plant origin can both stimulate and inhibit the biosynthesis of various types collagens, accelerate or slower down their catabolism, regulate the activity of enzymes involved in the collagen's metabolism. Most of the studied compounds realize their effects simultaneously by several mechanisms. Among them, the most common are the direct influence of the substance on the processes of collagen genes expression and indirect influence via TGF-beta1- pathway. In addition, a fairly common are effects on collagen synthesis by changing organism's pools of free amino acids (as the starting compounds for this protein synthesis) and by regulation of hydroxylases (performing collagen post-translational modifications and crosslinking). Besides TGF-beta1 others cytokines can also be involved in the processes of collagen metabolism regulation by compounds of plant origin. In particular, this is characteristic of triterpenes and phytoestrogens. Such a variety of methods for collagens metabolism regulation creates a wide range of possibilities for developing new preparations based on extracts or pure plant compounds able to correct connective tissue collagen structure and metabolic disorders with minimal adverse effects. Fundamentally different possibilities for the influence of plant organisms on collagens are opened with the use of genetically modified plants. Recombinant collagens allow to obtain proteins with new programmed features, making it possible to synthesize proteins with predetermined properties for medical use.

BACKGROUND: Dual modification of collagen was performed using ionic liquid (IL) and ultrasound (US) to modulate the activity of collagen hydrolyzed peptides and reveal the production mechanism of cowhide‐derived dipeptidyl peptidase (DPP‐IV) inhibitory peptides. RESULTS: The results revealed that dual modification (IL + US) significantly improved the hydrolytic degree of collagen (P < 0.05). Meanwhile, IL and US tended to promote the break of hydrogen bonds, but inhibit the crosslinking between collagens. The double modification reduced the thermal stability and accelerated the exposure of tyrosine and phenylalanine of collagen, and improved the proportion of small molecular (< 1 kDa) peptides in collagen hydrolysates. Interestingly, the hydrophobic amino acid residues and DPP‐IV inhibitory activity of collagen peptides with small molecular weight (< 1 kDa) was increased further under the combination of IL and US. CONCLUSION: Enhanced hypoglycemic activity of collagen peptides can be attained through the dual modification of IL and US. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Standardized extracts of undenatured type II collagen (UC-II) are used as alternative approaches to the treatment of osteoarthritis (OA). The effect of UC-II extracts is associated with the modulation of the mechanisms of innate and acquired immunity, a decrease in the activity of proinflammatory cytokines and prostaglandins. Epitopes of native collagen in the structure of UC-II contribute to a decrease in the activity of autoimmune reactions that stimulate cartilage degradation. Interacting with discoidin receptors, UC-II accelerates the reconstruction of cartilage connective tissue and inhibits the pro-inflammatory effects of endogenous collagens. Experimental and clinical studies confirm the effectiveness of the use of standardized substances UC-II for acceleration of cartilage regeneration and reduce pain in OA and subclinical joint dysfunction.

The specific viscoelastic mechanical properties of Achilles tendons are highly dependent on the structural characteristics of collagen at and between all hierarchical levels. Research has been conducted on the deformation mechanisms of positional tendons and single fibrils, but knowledge about the coupling between the whole tendon and nanoscale deformation mechanisms of more commonly injured energy-storing tendons, such as Achilles tendons, remains sparse. By exploiting the highly periodic arrangement of tendons at the nanoscale, in situ loading of rat Achilles tendons during small-angle X-ray scattering acquisition was used to investigate the collagen structural response during load to rupture, cyclic loading and stress relaxation. The fibril strain was substantially lower than the applied tissue strain. The fibrils strained linearly in the elastic region of the tissue, but also exhibited viscoelastic properties, such as an increased stretchability and recovery during cyclic loading and fibril strain relaxation during tissue stress relaxation. We demonstrate that the changes in the width of the collagen reflections could be attributed to strain heterogeneity and not changes in size of the coherently diffracting domains. Fibril strain heterogeneity increased with applied loads and after the toe region, fibrils also became increasingly disordered. Additionally, a thorough evaluation of radiation damage was performed. In conclusion, this study clearly displays the simultaneous structural response and adaption of the collagen fibrils to the applied tissue loads and provide novel information about the transition of loads between length scales in the Achilles tendon. [Display omitted] [ABSTRACT FROM AUTHOR]

In the present research, the enzyme-facilitated collagen from sea eel (Muraenesox cinereus) swim bladder was isolated, and the collagen characteristics were analyzed. Then, the collagen sponge was prepared and its potential mechanism in promoting skin wound healing in mice was further investigated. Collagen was obtained from the swim bladder of sea eels employing the pepsin extraction technique. Single-factor experiments served as the basis for the response surface method (RSM) to optimize pepsin concentration, solid-liquid ratio, and hydrolysis period. With a pepsin concentration of 2067 U/g, a solid-liquid ratio of 1:83 g/mL, and a hydrolysis period of 10 h, collagen extraction achieved a yield of 93.76%. The physicochemical analysis revealed that the extracted collagen belonged to type I collagen, and the collagen sponge displayed a fibrous structure under electron microscopy. Furthermore, in comparison to the control group, mice treated with collagen sponge dressing exhibited elevated activities of superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-Px), and decreased levels of malondialdehyde (MDA), interleukin (IL)-1β, interleukin (IL)-6, and tumor necrosis factor (TNF)-α. The collagen sponge dressing effectively alleviated inflammation in the wound area, facilitating efficient repair and rapid healing of the skin tissue. During the initial phase of wound healing, the group treated with collagen sponge dressing exhibited an enhancement in the expressions of cluster of differentiation (CD)31, epidermal growth factor (EGF), transforming growth factor (TGF)-β1, and type I collagen, leading to an accelerated rate of wound healing. In addition, this collagen sponge dressing could also downregulate the expressions of CD31, EGF, and type I collagen to prevent scar formation in the later stage. Moreover, this collagen treatment minimized oxidative damage and inflammation during skin wound healing and facilitated blood vessel formation in the wound. Consequently, it exhibits significant potential as an ideal material for the development of a skin wound dressing.

Chemically crosslinked acellular bovine pericardium (ABP) has been widely used in clinical practice as bioprostheses. To ensure its consistency and durability, crosslinkers are used in excess, with stability guided by indicators including the hydrothermal denaturation temperature, the enzymatic resistance and the degree of crosslinking. Yet, understanding of the intermolecular structure in collagen fibrils which imparts the intrinsic stability of the ABPs is lacking, and the discrepancies in the stability criteria in varied conditions are poorly explained. In this study, synchrotron small-angle X-ray scattering (SAXS) in combination with thermal and colorimetric methods are employed to investigate the changes in the structure and the stability of ABPs during crosslinking using glutaraldehyde (GA) or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) at different concentrations. Based on the findings, a mechanism is proposed to explicate the crosslinking effects on collagen structure and the relationship between the structure and each stability indicator. At low crosslinker concentrations, the telopeptidyl-helical linkages are preferred, which cause rearrangements in the intermolecular structure of collagen, and efficiently contribute to its stabilities. Excess crosslinking is revealed by a revert trend in structural changes and the plateauing of the stabilities, assigning to the helical-helical linkages and monovalent bindings. The former would improve thermal stability but not collagenase resistance, whereas the latter have negligible effects. Overall, this study provides a mechanistic understanding of the chemical crosslinking of ABPs, which will contribute to the future development of more efficient and economically viable strategies to produce bioprostheses. Chemical crosslinking imparts suitable properties to acellular bovine pericardium (ABP) for clinical applications, yet the understanding is lacking on the structure-stability relationship especially under different crosslinking conditions. Structural evidence in this study differentiates the binding sites during crosslinking in collagen fibrils at different crosslinker concentrations, highlighting the excess usage in the conventional crosslinking treatments. The mechanism based on the structure of collagen also successfully explains the dissimilarity in hydrothermal and enzymatic stabilities with varied crosslinking conditions. Future researches focusing on developing biomaterials via chemical crosslinking of ABPs would benefit from this study, for its contribution to the better understanding of the relationship of collagen structure and functions. [Display omitted] [ABSTRACT FROM AUTHOR]

Summary: The antioxidant peptide was produced from hydrolysis with Bacillus subtilis proteases supplemented with different duration of ultrasound, and the hydrolysis and structural characteristics of yak skin gelatin (YSG) were characterised. Compared with the excessive ultrasonic treatment (10–40 min), the YSG produced by moderate ultrasonic treatment (5 min) had a higher degree of hydrolysis and the DPPH free radical scavenging ability, and ABTS free radical scavenging activity of the hydrolysate was increased. The results showed that ultrasound for 5 min significantly weakened hydrogen bonds and promoted the exposure of hydrophobic groups, resulting in the loosening of collagen structure. Appropriate ultrasonic treatment obviously changed the gelatin structure, as the changes in the decrease of glass transition temperature, the reduction of particle size and the destruction of the surface morphology. These findings showed that moderate ultrasound (5 min) could modify the structure of YSG and, therefore, has great potential in the production of antioxidant peptides. [ABSTRACT FROM AUTHOR]

Scar formation and chronic ulcers can develop following a skin injury. They are the result of the over‐ or underproduction of collagen. It is very important to evaluate the quality and quantity of the collagen that is produced during wound healing, especially with respect to its structure, as these factors are very important to a complicated outcome. However, there is no standard way to quantitatively analyse dermal collagen. As prior work characterised some potentially fractal properties of collagen, it was hypothesised that collagen structure could be evaluated with fractal dimension analysis. Small‐angle X‐ray scattering technology (SAXS) was used to evaluate the dermis of rats exposed to graft harvest, burn, and diabetic pathologic states. It was found that almost all collagen structures could be quantitatively measured with fractal dimension analysis. Further, there were significant differences in the three‐dimensional (3‐D) structure of normal collagen versus that measured in pathologic tissues. There was a significant difference in the 3‐D structure of collagen at different stages of healing. The findings of this work suggest that fractal analysis is a good tool for wound healing analysis, and that quantitative collagen analysis is very useful for assessing the structure of dermal collagen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developed a novel ionic liquid-aqueous biphasic system (IL-ABS) formed by TBAH and potassium tartrate for efficient separation and purification. • Introduced the first application of IL-ABS in solid waste separation, achieving resource recovery and purification. • Demonstrated the capability of IL-THI process to efficiently separate collagen and Cr(III), achieving a 990.9% dechroming degree at room temperature. • Recycled TBAH showed excellent reproducibility and purity across five cycles, maintaining Cr content of c.a. 2.65 mg/kg in collagen well below the standard limit, supporting sustainable chemical processes. • Ensured the structural integrity of collagen, maintaining its triple helical conformation via IL-THI process. Chrome-tanned leather shavings (CTLS) with abundant collagen of 70–90 wt% but high Cr content of 2–4 wt% are considered as hazardous wastes. Due to the stable covalent bond between Cr and collagen, current processes for collagen recovery from CTLS face challenges including low dechroming efficiency, collagen disruption, high energy and chemical consumption and secondary pollution. In this paper, an innovative IL-targeted homogeneous isolation (IL-THI) process based on the reusable ionic liquid-aqueous biphasic system (IL-ABS) was established for the simultaneous resource recovery and complete dechroming of CTLS at room temperature, with the recovery rate of collagen reached 72.4 % while Cr content in collagen is reduced from 35.65 × 103 mg/kg to 1.78 mg/kg. This IL-ABS enriched TBAH in the upper phase and potassium tartrate in the lower phase. Moreover, TBAH demonstrated excellent reproducibility across five cycles, achieving consistently low Cr content of 2.65 mg/kg in collagen, far below the 50 mg/kg limit in national standards. The triple helix conformation and the molecular weight of the collagen product were confirmed via Fourier-transform infrared spectroscopy, X-ray diffraction analyses, circular dichroism spectra analysis and SDS-PAGE. Moreover, economic calculations demonstrated the suitability of this novel process for sustainable CTLS recovery. The superior dechroming ability of IL-ABS is attributed to the formation of Cr(III)-Tartrate complexes, which preferentially migrate to the lower phase due to the solvophobic effect, while dissolved collagen is recovered from the upper phase, as disclosed by UV–Vis spectra, ICP-OES, and all-atom molecular dynamics simulations. Additionally, IL-THI process demonstrates considerable potential for the isolation of Cr(III) and collagen in solid waste, with low energy consumption, improved separation efficiency, and increased design flexibility. [ABSTRACT FROM AUTHOR]

It is well known that collagen tissue, especially the collagen structure, plays an important role in wound healing. However, most research on collagen has been qualitative and morphological, based on sections, and cannot be used for real‐time monitoring and clinical prediction. There are no standardized methods of quantitative analysis based on the whole skin sample in three dimensions (3‐D). In order to explore a 3‐D quantitative analysis, we developed a method that was derived from that of material science and physics, combined with our previous technique, X‐ray scattering (SAXS). We hypothesized that the dermis might be analysed by fractal dimensions. To test this hypothesis, we performed the analysis in different pathological conditions, such as scar tissue, different time points after wounding, skin in different degrees of burns and skin in diabetes. The results showed that fractal dimension analysis could detect differences in different locations of the scar tissue, at different time points after wounding, and at a different extent of the severity of skin in diabetes. The research demonstrated that fractal dimension analysis can describe the 3‐D structure of the collagen tissue of the skin, which will be beneficial for studying wound healing and finding new clinical treatments. [ABSTRACT FROM AUTHOR]

The purpose of the study was to evaluate the integrity of dentine type I collagen after self-etching (SE) treatments with strong and mild universal adhesives. Coronal dentine specimens (n = 10/product) were imaged by optical microscopy and analyzed by ATR-FTIR spectroscopy before and after treatment with 32% phosphoric acid gel (PA-negative control), 17% neutral EDTA (ED-positive control) conditioners and Adhese Universal (AD), Clearfil Universal Bond Quick (CQ), G-Premio Bond (GP), Prelude One (PR) and Scotchbond Universal (SB) adhesives. From the spectroscopic analysis the following parameters were determined: a) Extent of dentine demineralization (DM%) and b) percentage area of the Amide I curve-fitted components of β-turns, 3 10 -helix/β-turns, α-helix, random coils, β-sheets and collagen maturation (R) index. Statistical analysis was performed by one-way ANOVA (DM%), paired t -test/Wilcoxon test (Amide I components) and Spearman correlation coefficient (DM% vs Amide I components) at an a = 0.05 level. PA, ED and GP removed the smear-layer and opened tubule orifices, whereas all other treatments removed only the intratubular smear-layer fraction. The ranking of the statistically significant differences in DM% was PA > GP > ED > AD, SB, CQ, PR, with AD being significantly different from PR. Regarding the Amide I components, PA demonstrated a significant reduction in β-turns, α-helices and an increase in β-sheets, GP a reduction in β-turns, AD an increase in β-turns and random coils, and CQ an increase in β-turns. PR, SB and ED showed insignificant differences in all the Amide I components. Significant correlations were found between DM%-random coils and DM%-R. The universal adhesives used in the SE mode induced none to minimal changes in dentine collagen structure, without evidence of the destabilization pattern observed after conventional phosphoric acid treatments. [ABSTRACT FROM AUTHOR]

Abstract Collagen structure in biological tissues imparts its intrinsic physical properties by the formation of several covalent crosslinks. For the first time, two major crosslinks in the skin dihydroxylysinonorleucine (HLNL) and histidinohydroxymerodesmosine (HHMD), were isotopically labelled and then analysed by liquid-chromatography high-resolution accurate-mass mass spectrometry (LC-HRMS) and small-angle neutron scattering (SANS). The isotopic labelling followed by LC-HRMS confirmed the presence of one imino group in both HLNL and HHMD, making them more susceptible to degrade at low pH. The structural changes in collagen due to extreme changes in the pH and chrome tanning were highlighted by the SANS contrast variation between isotopic labelled and unlabelled crosslinks. This provided a better understanding of the interaction of natural crosslinks with the chromium sulphate in collagen suggesting that the development of a benign crosslinking method can help retain the intrinsic physical properties of the leather. This analytical method can also be applied to study artificial crosslinking in other collagenous tissues for biomedical applications. Graphical abstract

Abstract Green solvents, such as propylene carbonate (PC), can be used in leather processing to improve the efficiency of chrome tanning and reduce wastewater. Here we report a combined small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) study on PC and its efficacy as a carrier medium during chrome tanning. SAXS analysis on the collagen structure of chrome tanned leather using PC, compared to conventionally tanned leather using water, showed an increase in Cr uptake in addition to the more uniform penetration of Cr through the leather cross-section. The increased binding of Cr to the collagen matrix drives the decreased hydration environment of the collagen triple helix. Furthermore, DSC studies show a uniform hydrothermal stability for the PC samples due to the more even distribution of Cr through the collagen matrix. Understanding the mechanisms by which chrome tanning occurs in non-aqueous solvents can guide us towards a more sustainable future for the leather industry. Graphical abstract

Glutaraldehyde cross-linked heterograft tissues, bovine pericardium (BP) or porcine aortic valves, are the leaflet materials in bioprosthetic heart valves (BHV) used in cardiac surgery for heart valve disease. BHV fail due to structural valve degeneration (SVD), often with calcification. Advanced glycation end products (AGE) are post-translational, non-enzymatic reaction products from sugars reducing proteins. AGE are present in SVD-BHV clinical explants and are not detectable in un-implanted BHV. Prior studies modeled BP-AGE formation in vitro with glyoxal, a glucose breakdown product, and serum albumin. However, glucose is the most abundant AGE precursor. Thus, the present studies investigated the hypothesis that BHV susceptibility to glucose related AGE, together with serum proteins, results in deterioration of collagen structure and mechanical properties. In vitro experiments studied AGE formation in BP and porcine collagen sponges (CS) comparing 14C-glucose and 14C-glyoxal with and without bovine serum albumin (BSA). Glucose incorporation occurred at a significantly lower level than glyoxal (p <0.02). BSA co-incubations demonstrated reduced glyoxal and glucose uptake by both BP and CS. BSA incubation caused a significant increase in BP mass, enhanced by glyoxal co-incubation. Two-photon microscopy of BP showed BSA induced disruption of collagen structure that was more severe with glucose or glyoxal co-incubation. Uniaxial testing of CS demonstrated that glucose or glyoxal together with BSA compared to controls, caused accelerated deterioration of viscoelastic relaxation, and increased stiffness over a 28-day time course. In conclusion, glucose, glyoxal and BSA uniquely contribute to AGE-mediated disruption of heterograft collagen structure and deterioration of mechanical properties. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Multiaxial testing of the small intestinal wall is critical for understanding its biomechanical properties and defining material models, but limited data and material models are available. The aim of the present study was to develop a microstructure-based material model for the small intestine and test whether there was a significant variation in the passive biomechanical properties along the length of the organ. Rat tissue was cut into eight segments that underwent inflation/extension testing, and their nonlinearly hyper-elastic and anisotropic response was characterized by a fiberreinforced model. Extensive parametric analysis showed a non-significant contribution to the model of the isotropic matrix and circumferential-fiber family, leading also to severe over-parameterization. Such issues were not apparent with the reduced neo-Hookean and (axial and diagonal)-fiber family model, that provided equally accurate fitting results. Absence from the model of either the axial or diagonal-fiber families led to ill representations of the force- and pressure-diameter data, respectively. The primary direction of anisotropy, designated by the estimated orientation angle of diagonalfiber families, was about 35°C to the axial direction, corroborating prior microscopic observations of submucosal collagen-fiber orientation. The estimated model parameters varied across and within the duodenum, jejunum, and ileum, corroborating histologically assessed segmental differences in layer thicknesses. [ABSTRACT FROM AUTHOR]

Arterial mechanics plays an important role in vascular pathophysiology and repair, and advanced imaging can inform constitutive models of vascular behavior. We have measured the mechanical properties of 14 human superficial femoral arteries (SFAs) (age 12–70, mean 48±19 years) using planar biaxial extension, and determined the preferred collagen fiber direction and dispersion using multiphoton microscopy. The collagen fiber direction and dispersion were evaluated using second-harmonic generation imaging and modeled using bivariate von Mises distributions. The microstructures of elastin and collagen were assessed using two-photon fluorescence imaging and conventional bidirectional histology. The mechanical and structural data were used to describe the SFA mechanical behavior using two- and four-fiber family invariant-based constitutive models. Older SFAs were stiffer and mechanically more nonlinear than younger specimens. In the adventitia, collagen fibers were undulated and diagonally-oriented, while in the media, they were straight and circumferentially-oriented. The media was rich in collagen that surrounded the circumferentially-oriented smooth muscle cells, and the elastin was present primarily in the internal and external elastic laminae. Older SFAs had a more circumferential collagen fiber alignment, a decreased circumferential-radial fiber dispersion, but the same circumferential-longitudinal fiber dispersion as younger specimens. Both the two- and the four-fiber family constitutive models were able to capture the experimental data, and the fits were better for the four-fiber family formulation. Our data provide additional details on the SFA intramural structure and inform structurally-based constitutive models. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Chronic ulcerative and hard-healing wounds are a growing global concern. Skin substitutes, including acellular dermal matrices (ADMs), have shown beneficial effects in healing processes. Presently, the vast majority of currently available ADMs are processed from xenobiotic or cadaveric skin. Here we propose a novel strategy for ADM preparation from human abdominoplasty-derived skin. Skin was processed using three different methods of decellularization involving the use of ionic detergent (sodium dodecyl sulfate; SDS, in hADM 1), non-ionic detergent (Triton X-100 in hADM 2), and a combination of recombinant trypsin and Triton X-100 (in hADM 3). We next evaluated the immunogenicity and immunomodulatory properties of this novel hADM by using an in vitro model of peripheral blood mononuclear cell culture, flow cytometry, and cytokine assays. We found that similarly sourced but differentially processed hADMs possess distinct immunogenicity. hADM 1 showed no immunogenic effects as evidenced by low T cell proliferation and no significant change in cytokine profile. In contrast, hADMs 2 and 3 showed relatively higher immunogenicity. Moreover, our novel hADMs exerted no effect on T cell composition after three-day of coincubation. However, we observed significant changes in the composition of monocytes, indicating their maturation toward a phenotype possessing anti-inflammatory and pro-angiogenic properties. Taken together, we showed here that abdominoplasty skin is suitable for hADM manufacturing. More importantly, the use of SDS-based protocols for the purposes of dermal matrix decellularization allows for the preparation of non-immunogenic scaffolds with high therapeutic potential. Despite these encouraging results, further studies are needed to evaluate the beneficial effects of our hADM 1 on deep and hard-healing wounds.

We present a mechanism for the selectivity of covalent/electrostatic binding of the Cr(III) ion to collagen, mediated by the kosmotropicity of the anions. Although a change in the long‐range ordered structure of collagen is observed after covalent binding (Cr(III)‐OOC) in the presence of SO42− at pH 4.5, the νsym(COO−) band remains intense, suggesting a relatively lower propensity for the Cr(III) to bind covalently instead of electrostatically through Cr(H2O)63+. Replacing SO42− with Cl− reduces the kosmotropic effect which further favors the electrostatic binding of Cr(III) to collagen. Our findings allow a greater understanding of mechanism‐specific metal binding in the collagen molecule. We also report for the first time, surface‐enhanced Raman spectroscopy to analyze binding mechanisms in collagen, suggesting a novel way to study chemical modifications in collagen‐based biomaterials. [ABSTRACT FROM AUTHOR]

Collagen is an important biomacromolecule, making up the majority of the extracellular matrix in animal tissues. Naturally occurring crosslinks in collagen stabilize its intermolecular structure in vivo, whereas chemical treatments for introducing synthetic crosslinks are often carried out ex vivo to improve the physical properties or heat stability of the collagen fibres for applications in biomaterials or leather production. Effective protection of intrinsic natural crosslinks as well as allowing them to contribute to collagen stability together with synthetic crosslinks can reduce the need for chemical treatments. However, the contribution of these natural crosslinks to the heat stability of collagen fibres, especially in the presence of synthetic crosslinks, is as yet unknown. Using synchrotron small‐angle X‐ray scattering, the in situ role of natural and synthetic crosslinks on the stabilization of the intermolecular structure of collagen in skins was studied. The results showed that, although natural crosslinks affected the denaturation temperature of collagen, they were largely weakened when crosslinked using chromium sulfate. The development of synergistic crosslinking chemistries could help retain the intrinsic chemical and physical properties of collagen‐based biological materials. [ABSTRACT FROM AUTHOR]

This review focuses on the SAXS and WAXS analysis of the collagen structure of leather, from pioneering works through to recent developments. X‐ray scattering can be used to investigate the structural features of fibrillar collagen in the leather matrix, including axial periodicity, fibril diameter, chemical fixation, hydration and fibrillar orientation. Key properties of leather, such as appearance, handle, strength, hydrothermal stability and resistance to putrefaction, are closely linked to these parameters, thereby underlining the importance of X‐ray scattering to the study of leather. Recent research on the molecular level changes in collagen structure at different stages of leather processing with a range of treatments is also summarized. We will highlight how studies using X‐ray scattering techniques have provided significant insights into tanning processes which could be used to improve leather properties and optimize/reduce the use of tanning agents such as chromium (III) in the industry. The review will also describe the details of collagen structure and tanning mechanisms that are yet to be determined by X‐ray scattering, as well as future advancements of this technique and what it can accomplish for the leather industry. [ABSTRACT FROM AUTHOR]

Decellularized tissues are considered superior scaffolds for cell cultures, preserving the microstructure of native tissues and delivering many kinds of cytokines. High hydrostatic pressure (HHP) treatment could remove cells physically from biological tissues rather than chemical methods. However, there are some risks of inducing destruction or denaturation of extracellular matrices (ECMs) at an ultrahigh level of HHP. Therefore, efficient decellularization using moderate HHP is required to remove almost all cells simultaneously to suppress tissue damage. In this study, we proposed a novel decellularization method using a moderate HHP with supercooling pretreatment. To validate the decellularization method, a supercooling device was developed to incubate human dermal fibroblasts or collagen gels in a supercooled state. The cell suspension and collagen gels were subjected to 100, 150, and 200 MPa of HHP after supercooling pretreatment, respectively. After applying HHP, the viability and morphology of the cells and the collagen network structure of the gels were evaluated. The viability of cells decreased dramatically after HHP application with supercooling pretreatment, whereas the microstructures of collagen gels were preserved and cell adhesivity was retained after HHP application. In conclusion, it was revealed that supercooling pretreatment promoted the denaturation of the cell membrane to improve the efficacy of decellularization using static application of moderate HHP. Furthermore, it was demonstrated that the HHP with supercooling pretreatment did not degenerate and damage the microstructure in collagen gels.

Knowledge of soft tissue fiber structure is necessary for accurate characterization and modeling of their mechanical response. Fiber configuration and structure informs both our understanding of healthy tissue physiology and of pathological processes resulting from diseased states. This study develops an automatic algorithm to simultaneously estimate fiber global orientation, abundance, and waviness in an investigated image. To our best knowledge, this is the first validated algorithm which can reliably separate fiber waviness from its global orientation for considerably wavy fibers. This is much needed feature for biological tissue characterization. The algorithm is based on incremental movement of local regions of interest (ROI) and analyzes two-dimensional images. Pixels belonging to the fiber are identified in the ROI, and ROI movement is determined according to local orientation of fiber within the ROI. The algorithm is validated with artificial images and ten images of porcine trachea containing wavy fibers. In each image, 80-120 fibers were tracked manually to serve as verification. The coefficient of determination R2 between curve lengths and histograms documenting the fiber waviness and global orientation were used as metrics for analysis. Verification-confirmed results were independent of image rotation and degree of fiber waviness, with curve length accuracy demonstrated to be below 1% of fiber curved length. Validation-confirmed median and interquartile range of R2, respectively, were 0.90 and 0.05 for curved length, 0.92 and 0.07 for waviness, and 0.96 and 0.04 for global orientation histograms. Software constructed from the proposed algorithm was able to track one fiber in about 1.1 s using a typical office computer. The proposed algorithm can reliably and accurately estimate fiber waviness, curve length, and global orientation simultaneously, moving beyond the limitations of prior methods., Competing Interests: Conflict of Interest The authors declare that they have no competing interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Microscopy Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Abstract Although the biomechanical properties of skin and its molecular components have been extensively studied, little research has been devoted to understanding the links between them. Here, a comprehensive analysis of the molecular components of deer and cow skins was undertaken in order to understand the basis of their physical properties. These skins were chosen because they are known to be strong yet supple, exhibiting properties that have been exploited by man for centuries. Firstly, the tensile strength, tear strength and denaturation temperature of deer and cow skins were measured. Secondly, the organisation of the collagen fibrils and presence of glycosaminoglycans in each skin was investigated using polarising microscopy (PM), laser scanning confocal microscopy (LSCM), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) and small angle X-ray scattering (SAXS). Finally, amino acid, crosslink and glycosaminoglycan analyses were carried out on both skins in the study. The results of the study showed that individual physical properties such as tensile strength of the skin are derived from different combinations of biomolecular components which are reflected in collagen architecture. The "wavy" organisation of collagen fibres in deer skin was associated with a small fibril diameter, uniform glycosaminoglycan distribution and higher proportion of trivalent crosslinks. In contrast, the collagen fibrils in cow skin were large, contained a diverse glycosaminoglycan distribution and a higher proportion of tetravalent crosslinks, resulting in straight fibres. This study showed for the first time that the relationship between the structure of collagen in skin and its biomechanical functions is complex, arising from different architectural and molecular features including organisation of collagen fibres, diameters of collagen fibrils, distribution and amount of glycosaminoglycans and types and concentrations of crosslinks. [ABSTRACT FROM AUTHOR]

Abstract The inefficiency of the chromium (III)-collagen cross-linking reaction during conventional leather processing results in severe environmental pollution from the waste chromium in the effluent. A mechanistic study using synchrotron-based small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) on ThruBlu tanned leather, revealed the effect of chromium sulphate and its pre-treatments on collagen structure and stability. By pre-treating with complexing agents such as sodium formate and disodium phthalate, as well as nanoclay (sodium montmorillonite), the uniformity through bovine hide collagen matrix were improved significantly. These pre-treatments effectively reduce the reactivity of chromium during its cross-linking reaction with collagen while retaining its bound water. However, collagen pre-treated with a covalent cross-linker (glutaraldehyde) results in a decrease in both chromium-collagen cross-linking and bound water while improving uniformity. These molecular-level insights can be developed into metrics to guide us towards a more sustainable future for the leather industry. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Multiaxial testing of the small intestinal wall is critical for understanding its biomechanical properties and defining material models, but limited data and material models are available. The aim of the present study was to develop a microstructure-based material model for the small intestine and test whether there was a significant variation in the passive biomechanical properties along the length of the organ. Rat tissue was cut into eight segments that underwent inflation/extension testing, and their nonlinearly hyper-elastic and anisotropic response was characterized by a fiber-reinforced model. Extensive parametric analysis showed a non-significant contribution to the model of the isotropic matrix and circumferential-fiber family, leading also to severe over-parameterization. Such issues were not apparent with the reduced neo-Hookean and (axial and diagonal)-fiber family model, that provided equally accurate fitting results. Absence from the model of either the axial or diagonal-fiber families led to ill representations of the force- and pressure-diameter data, respectively. The primary direction of anisotropy, designated by the estimated orientation angle of diagonal-fiber families, was about 35° to the axial direction, corroborating prior microscopic observations of submucosal collagen-fiber orientation. The estimated model parameters varied across and within the duodenum, jejunum, and ileum, corroborating histologically assessed segmental differences in layer thicknesses.

Ehlers-Danlos syndrome (EDS) is the name for a heterogenous group of rare genetic connective tissue disorders with an overall incidence of 1 in 5000. The histological characteristics of EDS have been previously described in detail in the late 1970s and early 1980s. Since that time, the classification of EDS has undergone significant changes, yet the description of the histological features of collagen morphology in different EDS subtypes has endured the test of time. Nonlinear microscopy techniques can be utilized for non-invasive in vivo label-free imaging of the skin. Among these techniques, two-photon absorption fluorescence (TPF) microscopy can visualize endogenous fluorophores, such as elastin, while the morphology of collagen fibers can be assessed by second-harmonic generation (SHG) microscopy. In our present work, we performed TPF and SHG microscopy imaging on ex vivo skin samples of one patient with classical EDS and two patients with vascular EDS and two healthy controls. We detected irregular, loosely dispersed collagen fibers in a non-parallel arrangement in the dermis of the EDS patients, while as expected, there was no noticeable impairment in the elastin content. Based on further studies on a larger number of patients, in vivo nonlinear microscopic imaging could be utilized for the assessment of the skin status of EDS patients in the future. [ABSTRACT FROM AUTHOR]

Obesity has been linked with numerous health issues as well as an increased risk of breast cancer. Although effects of direct obesity in patient outcomes is widely studied, effects of exposure to obesity-related systemic influences in utero have been overlooked. In this study, we investigated the effect of multigenerational obesity on epithelial cell migration and invasion using decellularized breast tissues explanted from normal female mouse pups from a diet induced multigenerational obesity mouse model. We first studied the effect of multigenerational diet on the mechanical properties, adipocyte size, and collagen structure of these mouse breast tissues, and then, examined the migration and invasion behavior of normal (KTB-21) and cancerous (MDA-MB-231) human mammary epithelial cells on the decellularized matrices from each diet group. Breast tissues of mice whose dams had been fed with high-fat diet exhibited larger adipocytes and thicker and curvier collagen fibers, but only slightly elevated elastic modulus and inflammatory cytokine levels. MDA-MB-231 cancer cell motility and invasion were significantly greater on the decellularized matrices from mice whose dams were fed with high-fat diet. A similar trend was observed with normal KTB-21 cells. Our results showed that the collagen curvature was the dominating factor on this enhanced motility and stretching the matrices to equalize the collagen fiber linearity of the matrices ameliorated the observed increase in cell migration and invasion in the mice that were exposed to a high-fat diet in utero. Previous studies indicated an increase in serum leptin concentration for those children born to an obese mother. We generated extracellular matrices using primary fibroblasts exposed to various concentrations of leptin. This produced curvier ECM and increased breast cancer cell motility for cells seeded on the decellularized ECM generated with increasing leptin concentration. Our study shows that exposure to obesity in utero is influential in determining the extracellular matrix structure, and that the resultant change in collagen curvature is a critical factor in regulating the migration and invasion of breast cancer cells. [ABSTRACT FROM AUTHOR]

Collagen, which is often used in healthcare materials and biomedical research, is largely extracted from animal sources. Recombinant human collagen has the potential to be a promising alternative to animal collagen which has many shortcomings, including immunogenicity and lack of biocompatibility. Currently, recombinant human collagen has been expressed in both eukaryotic and prokaryotic hosts with varying degrees of success. One issue with recombinant collagen across all hosts is the inability to achieve full length collagen with native amounts of post-translational modifications, prompting much exciting research in this direction. There has also been much effort in improving yield and biomimicry of recombinant collagen. This review discusses collagen structure and current methods for extracting animal collagen, before introducing current research in synthesising recombinant human collagen in various hosts, and finally highlighting challenges in the field.

Magnetic resonance imaging (MRI) offers the opportunity to study biological tissues and processes in a non-disruptive manner. The technique shows promise for the study of the load-bearing performance (consolidation) of articular cartilage and changes in articular cartilage accompanying osteoarthritis. Consolidation of articular cartilage involves the recording of two transient characteristics: the change over time of strain and the hydrostatic excess pore pressure (HEPP). MRI study of cartilage consolidation under mechanical load is limited by difficulties in measuring the HEPP in the presence of the strong magnetic fields associated with the MRI technique. Here we describe the use of MRI to image and characterize bovine articular cartilage deforming under load in an MRI compatible consolidometer while monitoring pressure with a Fabry-Perot interferometer-based fiber-optic pressure transducer.

Demineralized bone matrix (DBM) is a natural, collagen-based, osteoinductive biomaterial. Nevertheless, there are conflicting reports on the efficacy of this product. The purpose of this study was to evaluate whether DBM collagen structure is affected by particle size and can influence DBM cytocompatibility and osteoinductivity. Sheep cortical bone was ground and particles were divided in three fractions with different sizes, defined as large (L, 1-2 mm), medium (M, 0.5-1 mm), and small (S, <0.5 mm). After demineralization, the chemical-physical analysis clearly showed a particle size-dependent alteration in collagen structure, with DBM-M being altered but not as much as DBM-S. DBM-M displayed a preferable trend in almost all biological characteristics tested, although all DBM particles revealed an optimal cytocompatibility. Subcutaneous implantation of DBM particles into immunocompromised mice resulted in bone induction only for DBM-M. When sheep MSC were seeded onto particles before implantation, all DBM particles were able to induce new bone formation with the best incidence for DBM-M and DBM-S. In conclusion, the collagen alteration in DBM-M is likely the best condition to promote bone induction in vivo. Furthermore, the choice of 0.5-1 mm particles may enable to obtain more efficient and consistent results among different research groups in bone tissue-engineering applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1019-1033, 2017. [ABSTRACT FROM AUTHOR]

The main features of the triple helical structure of collagen were deduced in the mid-1950s from fibre X-ray diffraction of tendons. Yet, the resulting models only could offer an average description of the molecular conformation. A critical advance came about 20 years later with the chemical synthesis of sufficiently long and homogeneous peptides with collagen-like sequences. The availability of these collagen model peptides resulted in a large number of biochemical, crystallographic and NMR studies that have revolutionized our understanding of collagen structure. High-resolution crystal structures from collagen model peptides have provided a wealth of data on collagen conformational variability, interaction with water, collagen stability or the effects of interruptions. Furthermore, a large increase in the number of structures of collagen model peptides in complex with domains from receptors or collagen-binding proteins has shed light on the mechanisms of collagen recognition. In recent years, collagen biochemistry has escaped the boundaries of natural collagen sequences. Detailed knowledge of collagen structure has opened the field for protein engineers who have used chemical biology approaches to produce hyperstable collagens with unnatural residues, rationally designed collagen heterotrimers, self-assembling collagen peptides, etc. This review summarizes our current understanding of the structure of the collagen triple helical domain (COLx3) and gives an overview of some of the new developments in collagen molecular engineering aiming to produce novel collagen-based materials with superior properties. [ABSTRACT FROM AUTHOR]