Building collagen molecules, fibrils, and suprafibrillar structures

Mineral and cross-linking in collagen fibrils: The mechanical behavior of bone tissue at the nano-scale

The mineralized collagen fibril is the main building block of hard tissues and it directly affects the macroscopic mechanics of biological tissues such as bone. The mechanical behavior of the fibril itself is determined by its structure: the content of collagen molecules, minerals, and cross-links, and the mechanical interactions and properties of these components. Advanced glycation end products (AGEs) form cross-links between tropocollagen molecules within the collagen fibril and are one important factor that is believed to have a major influence on the tissue. For instance, it has been shown that brittleness in bone correlates with increased AGEs densities. However, the underlying nano-scale mechanisms within the mineralized collagen fibril remain unknown. Here, we study the effect of mineral and AGEs cross-linking on fibril deformation and fracture behavior by performing destructive tensile tests using coarse-grained molecular dynamics simulations. Our results demonstrate that after exceeding a critical content of mineral, it induces stiffening of the collagen fibril at high strain levels. We show that mineral morphology and location affect collagen fibril mechanics: The mineral content at which this stiffening occurs depends on the mineral's location and morphology. Further, both, increasing AGEs density and mineral content lead to stiffening and increased peak stresses. At low mineral contents, the mechanical response of the fibril is dominated by the AGEs, while at high mineral contents, the mineral itself determines fibril mechanics.

The influence and mechanism of fish collagen peptide and egg yolk lecithin on proliferation and lipid composition in feline adipocytes

The influences of fish collagen peptide (FCP) and egg yolk lecithin (EYL) on the proliferation, fat accumulation and triglyceride content in feline adipocytes were investigated in this work, aiming at unveiling the mechanism of fat accumulation for cheek of feline animals. The lipogenic changes of adipocytes in the presence of FCP and EYL were determined by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The results demonstrated that FCP of 10 mg/mL had the strongest cell activity, with a relative increment rate of 156 ± 0.23%, and the triglyceride content reached 215.9 ± 3.86 mmol/L. By comparison, it was observed that an EYL concentration of 5 mg/mL elicited the highest cell activity, exhibiting a relative increment rate of 152 ± 0.60%, and the level of triglyceride content was noted to reached 256.56 ± 25.68 mmol/L. After the feline adipocytes were treated with different concentrations of two active substances, fat formation and lipid droplets were found by oil red O staining. Liposome analyses confirmed that the formation of lipid compounds was regulated by FCP and EYL through pathways involved in lipid metabolism, notably including inositol phosphate insulin resistance, and phosphatidylinositol signaling pathways. This regulation was found to enhance cell vitality and facilitate fat accumulation. These findings provide a new strategy for the development of nutritional and healthy products or foods that promote feline cheek.

Coating based on chitosan/vancomycin nanoparticles: Patterns of formation in a water-carbon dioxide biphase system and in vivo stability

The patterns of formation of chitosan nanoparticles doped with vancomycin and coatings based on them in carbonate solutions have been investigated for the first time in this study. Using a technique of radioactive indicators, it was found that at a CO2 pressure of 30 MPa, the yield of the nanoparticles was ∼85 %, and a maximum antibiotic encapsulation efficiency of ∼30 % was achieved. By spectrophotometric and high-resolution microscopy, it was found that the coating of stabilized xenopericardial tissue of bioprosthetic heart valve, based on chitosan nanoparticles doped with vancomycin with a zeta potential |ζ| ∼20 mV completely covers collagen fibers by depositing about 60 nm nanoparticles onto them under direct deposition from carbonic acid at a pressure of 30 MPa CO2. The coating preserves the mechanical strength characteristics of collagen tissue and completely suppresses the growth of S. aureus pathogenic biofilm. This is consistent with the observed increase in antibiotic release of 15 % when the medium was acidified. Histological study demonstrated that the structure of pericardial tissues was not significantly altered by the deposition nanoparticles from carbonic acid. It was found that the rate of biodegradation of polymers and vancomycin in the coating differs by half (16 weeks for the rat model). A significantly lower degradation rate of antibiotics (∼50 % of vancomycin total remaining mass and ∼25 % of chitosan) was associated with its reliable encapsulation into nanoparticles.

Angle-Resolved Linear Dichroism to Probe the Organization of Highly Ordered Collagen Biomaterials

Controlling the assembly of high-order structures is central to soft-matter and biomaterial engineering. Angle-resolved linear dichroism can probe the ordering of chiral collagen molecules in the dense state. Collagen triple helices were aligned by solvent evaporation. Their ordering gives a strong linear dichroism (LD) that changes sign and intensity with varying sample orientations with respect to the beam linear polarization. Being complementary to circular dichroism, which probes the structure of chiral (bio)molecules, LD can shift from the molecular to the supramolecular scale and from the investigation of the conformation to interactions. Supported by multiphoton microscopy and X-ray scattering, we show that LD provides a straightforward route to probe collagen alignment, determine the packing density, and monitor denaturation. This approach could be adapted to any assembly of chiral (bio)macromolecules, with key advantages in detecting large-scale assemblies with high specificity to aligned and chiral molecules and improved sensitivity compared to conventional techniques.

PCPE-2 (procollagen C-proteinase enhancer-2): the NON-IDENTICAL twin of PCPE-1

PCPE-2 was discovered at the beginning of this century, and was soon identified as a close homolog of PCPE-1 (procollagen C-proteinase enhancer 1). After the demonstration that it could also stimulate the proteolytic maturation of fibrillar procollagens by BMP-1/tolloid-like proteinases (BTPs), PCPE-2 did not attract much attention as it was thought to fulfill the same functions as PCPE-1 which was already well-described. However, the tissue distribution of PCPE-2 shows both common points and significant differences with PCPE-1, suggesting that their activities are not fully overlapping. Also, the recently established connections between PCPE-2 (gene name PCOLCE2) and several important diseases such as atherosclerosis, inflammatory diseases and cancer have highlighted the need for a thorough reappraisal of the in vivo roles of this regulatory protein. In this context, the recent finding that, while retaining the ability to bind fibrillar procollagens and to activate their C-terminal maturation, PCPE-2 can also bind BTPs and inhibit their activity has substantially extended its potential functions. In this review, we describe the current knowledge about PCPE-2 with a focus on collagen fibrillogenesis, lipid metabolism and inflammation, and discuss how we could further advance our understanding of PCPE-2-dependent biological processes.

Current status and prospects of gelatin and its derivatives in oncological applications: Review

Treating cancer remains challenging due to the substantial side effects and unfavourable pharmacokinetic characteristics of antineoplastic medications, despite the progress made in comprehending the properties and actions of tumour cells in recent years. The advancement of biomaterials, such as stents, implants, personalised drug delivery systems, tailored grafts, cell sheets, and other transplantable materials, has brought about a significant transformation in healthcare and medicine in recent years. Gelatin is a very adaptable natural polymer that finds extensive application in healthcare-related industries owing to its favourable characteristics, including biocompatibility, biodegradability, affordability, and the presence of accessible chemical groups. Gelatin is used as a biomaterial in the biomedical sector for the creation of drug delivery systems (DDSs) since it may be applied to various synthetic procedures. Gelatin nanoparticles (NPs) have been extensively employed as carriers for drugs and genes, specifically targeting diseased tissues such as cancer, tuberculosis, and HIV infection, as well as treating vasospasm and restenosis. This is mostly due to their biocompatibility and ability to degrade naturally. Gelatins possess a diverse array of potential applications that require more elucidation. This review focuses on the use of gelatin and its derivatives in the diagnosis and treatment of cancer. The advancement of biomaterials and bioreactors, coupled with the increasing understanding of emerging applications for biomaterials, has enabled progress in enhancing the efficacy of tumour treatment.

Mini review on collagens in normal skin and pathological scars: current understanding and future perspective

Pathological scar tissues are characterized by the presence of overabundant collagens whose structure and organization are also different from those in unwounded skin. This causes scar tissues to lose some functions performed by normal skin, and currently, there are no effective measures to prevent scar formation. Inflammation has been shown to modulate fibroblast proliferation, differentiation, and function, hence collagen production and organization. In this minireview, we provide an overview of the current understanding of collagen, specifically collagen type I and III which are main collagens in skin, structure and fibre formation and highlight their differences between normal skin and pathological scars. We discuss the role that cytokines play in modulating fibroblast function. We also identify some potential research directions which could help to further our understanding of the complex and dynamic wound healing and scar formation process.

In Operando Imaging Electrostatic-Driven Disassembly and Reassembly of Collagen Nanostructures

Collagen is the most abundant protein in tissue scaffolds in live organisms. Collagen can self-assemble in vitro, which has led to a number of biotechnological and biomedical applications. To understand the dominant factors that participate in the formation of collagen nanostructures, here we study in real time and with nanoscale resolution the disassembly and reassembly of collagens. We implement a high-speed force microscope, which provides in situ high spatiotemporal resolution images of collagen nanostructures under changing pH conditions. The disassembly and reassembly are dominated by the electrostatic interactions among amino-acid residues of different molecules. Acidic conditions favor disassembly by neutralizing negatively charged residues. The process sets a net repulsive force between collagen molecules. A neutral pH favors the presence of negative and positively charged residues along the collagen molecules, which promotes their electrostatic attraction. Molecular dynamics simulations reproduce the experimental behavior and validate the electrostatic-based model of the disassembly and reassembly processes.

Collagen in hepatocellular carcinoma: A novel biomarker and therapeutic target

HCC is globally recognized as a major health threat. Despite significant progress in the development of treatment strategies for liver cancer, recurrence, metastasis, and drug resistance remain key factors leading to a poor prognosis for the majority of liver cancer patients. Thus, there is an urgent need to develop effective biomarkers and therapeutic targets for HCC. Collagen, the most abundant and diverse protein in the tumor microenvironment, is highly expressed in various solid tumors and plays a crucial role in the initiation and progression of tumors. Recent studies have shown that abnormal expression of collagen in the tumor microenvironment is closely related to the occurrence, development, invasion, metastasis, drug resistance, and treatment of liver cancer, making it a potential therapeutic target and a possible diagnostic and prognostic biomarker for HCC. This article provides a comprehensive review of the structure, classification, and origin of collagen, as well as its role in the progression and treatment of HCC and its potential clinical value, offering new insights into the diagnosis, treatment, and prognosis assessment of liver cancer.

Preparation and Characterization of Novel Multifunctional Wound Dressing by Near-Field Direct-Writing Electrospinning and Its Application

Near-field direct-writing electrospinning technology can be used to produce ordered micro/nanofiber membrane dressings. The application of this technology can simply realize the control of dressing porosity, compound different functional substances, and adjust their distribution, thus improving the defects of common dressings such as insufficient breathability, poor moisture retention performance, and single function. Herein, a novel multifunctional wound dressing was prepared to utilize near-field direct-writing electrospinning technology, in which calf skin collagen type I (CSC-I) and polycaprolactone (PCL) were used as the composite matrix, Hexafluoroisopropanol (HFIP) as the solvent, and erythromycin (ERY) as an anti-infective drug component. The results show that the micro/nanofiber membranes prepared by near-field direct-writing electrospinning technology can all present a complete mesh structure, excellent thermal stability, and good moisturizing properties. Moreover, the composite fiber membrane loaded with ERY not only had obvious antibacterial properties against E. coli and S. thermophilus but also a better slow-release function of drugs (it is rare to have both in traditional wound dressings). Therefore, this experimental design can provide relevant theories and an experimental foundation for preparing a new type of medical dressing with drug loading and has good guiding significance for the application and promotion of near-field direct-writing electrospinning in medical dressings.

Recent research advances on polysaccharide-, peptide-, and protein-based hemostatic materials: A review

Hemorrhage is a potentially life-threatening emergency that can occur at any time or place. Whether traumatic, congenital, surgical, disease-related, or drug-induced, bleeding can lead to severe complications or death. Therefore, the development of efficient hemostatic materials is critical. However, the results and prognosis demonstrated by clinical means of hemostasis do not reach expectations. With the development of technology, novel hemostatic materials have been developed from polysaccharides (chitosan, hyaluronic acid, alginate, cellulose, cyclodextrins, starch, dextran, and carrageenan), peptides (self-assembling peptides), and proteins (silk fibroin, collagen, gelatin, keratin, and thrombin). These new materials exhibit high hemostatic efficacy due to the enhancement or interaction of various hemostatic mechanisms. The main forms include adhesives, sealants, bandages, hemostatic powders, and hemostatic sponges. This article introduces the clotting process and principles of hemostatic methods and reviews the research on polysaccharide-, peptide-, and protein-based hemostatic materials in the last five years. The design ideas and hemostatic principles of polysaccharide-, peptide-, and protein-based hemostatic materials are mainly introduced. Finally, we summarize material designs, advantages, disadvantages, and challenges regarding hemostatic materials.

Extracellular matrix biomechanical roles and adaptation in health and disease

Extracellular matrices (ECMs) are dynamic 3D macromolecular networks that exhibit structural characteristics and composition specific to different tissues, serving various biomechanical and regulatory functions. The interactions between ECM macromolecules such as collagen, elastin, glycosaminoglycans (GAGs), proteoglycans (PGs), fibronectin, and laminin, along with matrix effectors and water, contribute to the unique cellular and tissue functional properties during organ development, tissue homoeostasis, remodeling, disease development, and progression. Cells adapt to environmental changes by adjusting the composition and array of ECM components. ECMs, forming the 3D bioscaffolds of our body, provide mechanical support for tissues and organs and respond to the environmental variables influencing growth and final adult body shape in mammals. Different cell types display distinct adaptations to the respective ECM environments. ECMs regulate biological processes by controlling the diffusion of infections and inflammations, sensing and adapting to external stimuli and gravity from the surrounding habitat, and, in the context of cancer, interplaying with and regulating cancer cell invasion and drug resistance. Alterations in the ECM composition in pathological conditions drive adaptive responses of cells and could therefore result in abnormal cell behavior and tissue dysfunction. Understanding the biomechanical functionality, adaptation, and roles of distinct ECMs is essential for research on various pathologies, including cancer progression and multidrug resistance, which is of crucial importance for developing targeted therapies. In this Viewpoint article, we critically present and discuss specific biomechanical functions of ECMs and regulatory adaptation mechanisms in both health and disease, with a particular focus on cancer progression.

Extracellular matrix remodeling in the tumor immunity

The extracellular matrix (ECM) is a significant constituent of tumors, fulfilling various essential functions such as providing mechanical support, influencing the microenvironment, and serving as a reservoir for signaling molecules. The abundance and degree of cross-linking of ECM components are critical determinants of tissue stiffness. In the process of tumorigenesis, the interaction between ECM and immune cells within the tumor microenvironment (TME) frequently leads to ECM stiffness, thereby disrupting normal mechanotransduction and promoting malignant progression. Therefore, acquiring a thorough comprehension of the dysregulation of ECM within the TME would significantly aid in the identification of potential therapeutic targets for cancer treatment. In this regard, we have compiled a comprehensive summary encompassing the following aspects: (1) the principal components of ECM and their roles in malignant conditions; (2) the intricate interaction between ECM and immune cells within the TME; and (3) the pivotal regulators governing the onco-immune response in ECM.

An overview of extracellular matrix and its remodeling in the development of cancer and metastasis with a glance at therapeutic approaches

The extracellular matrix (ECM) is an inevitable part of tissues able to provide structural support for cells depending on the purpose of tissues and organs. The dynamic characteristics of ECM let this system fluently interact with the extrinsic triggers and get stiffed, remodeled, and/or degraded ending in maintaining tissue homeostasis. ECM could serve as the platform for cancer progression. The dysregulation of biochemical and biomechanical ECM features might take participate in some pathological conditions such as aging, tissue destruction, fibrosis, and particularly cancer. Tumors can reprogram how ECM remodels by producing factors able to induce protein synthesis, matrix proteinase expression, degradation of the basement membrane, growth signals and proliferation, angiogenesis, and metastasis. Therefore, targeting the ECM components, their secretion, and their interactions with other cells or tumors could be a promising strategy in cancer therapies. The present study initially introduces the physiological functions of ECM and then discusses how tumor-dependent dysregulation of ECM could facilitate cancer progression and ends with reviewing the novel therapeutic strategies regarding ECM.

Posterior corneoscleral limbus: Architecture, stem cells, and clinical implications

The limbus is a transition from the cornea to conjunctiva and sclera. In human eyes, this thin strip has a rich variation of tissue structures and composition, typifying a change from scleral irregularity and opacity to corneal regularity and transparency; a variation from richly vascularized conjunctiva and sclera to avascular cornea; the neural passage and drainage of aqueous humor. The limbal stroma is enriched with circular fibres running parallel to the corneal circumference, giving its unique role in absorbing small pressure changes to maintain corneal curvature and refractivity. It contains specific niches housing different types of stem cells for the corneal epithelium, stromal keratocytes, corneal endothelium, and trabecular meshwork. This truly reflects the important roles of the limbus in ocular physiology, and the limbal functionality is crucial for corneal health and the entire visual system. Since the anterior limbus containing epithelial structures and limbal epithelial stem cells has been extensively reviewed, this article is focused on the posterior limbus. We have discussed the structural organization and cellular components of the region beneath the limbal epithelium, the characteristics of stem cell types: namely corneal stromal stem cells, endothelial progenitors and trabecular meshwork stem cells, and recent advances leading to the emergence of potential cell therapy options to replenish their respective mature cell types and to correct defects causing corneal abnormalities. We have reviewed different clinical disorders associated with defects of the posterior limbus and summarized the available preclinical and clinical evidence about the developing topic of cell-based therapy for corneal disorders.

Modeling collagen fibril self-assembly from extracellular medium in embryonic tendon

Collagen is a key structural component of multicellular organisms and is arranged in a highly organized manner. In structural tissues such as tendons, collagen forms bundles of parallel fibers between cells, which appear within a 24-h window between embryonic day 13.5 (E13.5) and E14.5 during mouse embryonic development. Current models assume that the organized structure of collagen requires direct cellular control, whereby cells actively lay down collagen fibrils from cell surfaces. However, such models appear incompatible with the time and length scales of fibril formation. We propose a phase-transition model to account for the rapid development of ordered fibrils in embryonic tendon, reducing reliance on active cellular processes. We develop phase-field crystal simulations of collagen fibrillogenesis in domains derived from electron micrographs of inter-cellular spaces in embryonic tendon and compare results qualitatively and quantitatively to observed patterns of fibril formation. To test the prediction of this phase-transition model that free protomeric collagen should exist in the inter-cellular spaces before the formation of observable fibrils, we use laser-capture microdissection, coupled with mass spectrometry, which demonstrates steadily increasing free collagen in inter-cellular spaces up to E13.5, followed by a rapid reduction of free collagen that coincides with the appearance of less-soluble collagen fibrils. The model and measurements together provide evidence for extracellular self-assembly of collagen fibrils in embryonic mouse tendon, supporting an additional mechanism for rapid collagen fibril formation during embryonic development.

Biomimetic Scaffolds for Tendon Tissue Regeneration

Tendon tissue connects muscle to bone and plays crucial roles in stress transfer. Tendon injury remains a significant clinical challenge due to its complicated biological structure and poor self-healing capacity. The treatments for tendon injury have advanced significantly with the development of technology, including the use of sophisticated biomaterials, bioactive growth factors, and numerous stem cells. Among these, biomaterials that the mimic extracellular matrix (ECM) of tendon tissue would provide a resembling microenvironment to improve efficacy in tendon repair and regeneration. In this review, we will begin with a description of the constituents and structural features of tendon tissue, followed by a focus on the available biomimetic scaffolds of natural or synthetic origin for tendon tissue engineering. Finally, we will discuss novel strategies and present challenges in tendon regeneration and repair.

Nonlinear time-dependent mechanical behavior of mammalian collagen fibrils

The viscoelastic mechanical behavior of collagenous tissues has been studied extensively at the macroscale, yet a thorough quantitative understanding of the time-dependent mechanics of the basic building blocks of tissues, the collagen fibrils, is still missing. In order to address this knowledge gap, stress relaxation and creep tests at various stress (5-35 MPa) and strain (5-20%) levels were performed with individual collagen fibrils (average diameter of fully hydrated fibrils: 253 ± 21 nm) in phosphate buffered saline (PBS). The experimental results showed that the time-dependent mechanical behavior of fully hydrated individual collagen fibrils reconstituted from Type I calf skin collagen, is described by strain-dependent stress relaxation and stress-dependent creep functions in both the heel-toe and the linear regimes of deformation in monotonic stress-strain curves. The adaptive quasilinear viscoelastic (QLV) model, originally developed to capture the nonlinear viscoelastic response of collagenous tissues, provided a very good description of the nonlinear stress relaxation and creep behavior of the collagen fibrils. On the other hand, the nonlinear superposition (NSP) model fitted well the creep but not the stress relaxation data. The time constants and rates extracted from the adaptive QLV and the NSP models, respectively, pointed to a faster rate for stress relaxation than creep. This nonlinear viscoelastic behavior of individual collagen fibrils agrees with prior studies of macroscale collagenous tissues, thus demonstrating consistent time-dependent behavior across length scales and tissue hierarchies. STATEMENT OF SIGNIFICANCE: Pure stress relaxation and creep experiments were conducted for the first time with fully hydrated individual collagen fibrils. It is shown that collagen nanofibrils have a nonlinear time-dependent behavior which agrees with prior studies on macroscale collagenous tissues, thus demonstrating consistent time-dependent behavior across length scales and tissue hierarchies. This new insight into the non-linear viscoelastic behavior of the building blocks of mammalian collagenous tissues may serve as the foundation for improved macroscale tissue models that capture the mechanical behavior across length scales.

LOXL4, but not LOXL2, is the critical determinant of pathological collagen cross-linking and fibrosis in the lung

Idiopathic pulmonary fibrosis is a progressive fibrotic disease characterized by excessive deposition of (myo)fibroblast produced collagen fibrils in alveolar areas of the lung. Lysyl oxidases (LOXs) have been proposed to be the central enzymes that catalyze the cross-linking of collagen fibers. Here, we report that, while its expression is increased in fibrotic lungs, genetic ablation of LOXL2 only leads to a modest reduction of pathological collagen cross-linking but not fibrosis in the lung. On the other hand, loss of another LOX family member, LOXL4, markedly disrupts pathological collagen cross-linking and fibrosis in the lung. Furthermore, knockout of both Loxl2 and Loxl4 does not offer any additive antifibrotic effects when compared to Loxl4 deletion only, as LOXL4 deficiency decreases the expression of other LOX family members including Loxl2. On the basis of these results, we propose that LOXL4 is the main LOX activity underlying pathological collagen cross-linking and lung fibrosis.

Peptide-triggered self-assembly of collagen mimetic peptides into nanospheres by electrostatic interaction and π-π stacking

Collagen is the most abundant protein in various connective tissues, providing mechanical integrity as well as regulating cellular activities. Self-assembled peptides have been extensively explored to develop collagen mimetic materials, due to their attractive features such as easy synthesis, selective sequences and low immunogenicity. Metal ion-triggered self-assembly of collagen mimetic peptides has recently received increasing interests, since the addition of external stimuli offers programmable control of the self-assembly process. We have for the first time reported a peptide-stimulated self-assembly of collagen mimetic peptides into nanospheres by electrostatic interaction and π-π stacking. We have accidentally discovered that FAM-modified positively-charged triple helical peptide FAM-PRG was highly soluble, while the addition of a single-stranded negatively-charged peptide EOG-10 efficiently drove its self-assembly into well-ordered spherical nanomaterials. Peptide EOG-10 has been shown to mediate similar self-assembly of TPE-modified triple-helical peptide TPE-PRG into luminescent exquisite nanospheres, consistently demonstrating the robustness of this peptide-triggered strategy. Fluorescence monitoring of the interaction of EOG-10 and TPE-PRG at different ratios indicated that EOG-10 specifically binds to TPE-PRG to form a 3 : 1 complex. High salt concentration was shown to inhibit the self-assembly of TPE-PRG with EOG-10, suggesting that their self-assembly was controlled by electrostatic interaction. The self-assembly of TPE-PRG with EOG-10 has been further revealed to require the exact lengths of both peptides as well as complementary sequences without mutations, indicating a pairwise "side-by-side" binding mode. Notably, the identity of the N-terminal residues of X-PRG has been found to play a determinant role in the self-assembly, while non-aromatic residues lost the self-assembling capability, suggesting that π-π stacking and electrostatic interactions collectively modulate the self-assembly of X-PRG and EOG-10. To conclude, we have developed a highly biocompatible and programmably controlled peptide-triggered self-assembly approach to create novel collagen mimetic nanomaterials, which may have great potential in advanced functional materials.

Gelatin nanofibers: Recent insights in synthesis, bio-medical applications and limitations

The use of gelatin and gelatin-blend polymers as environmentally safe polymers to synthesis electrospun nanofibers, has caused a revolution in the biomedical field. The development of efficient nanofibers has played a significant role in drug delivery, and for use in advanced scaffolds in regenerative medicine. Gelatin is an exceptional biopolymer, which is highly versatile, despite variations in the processing technology. The electrospinning process is an efficient technique for the manufacture of gelatin electrospun nanofibers (GNFs), as it is simple, efficient, and cost-effective. GNFs have higher porosity with large surface area and biocompatibility, despite that there are some drawbacks. These drawbacks include rapid degradation, poor mechanical strength, and complete dissolution, which limits the use of gelatin electrospun nanofibers in this form for biomedicine. Thus, these fibers need to be cross-linked, in order to control its solubility. This modification caused an improvement in the biological properties of GNFs, which made them suitable candidates for various biomedical applications, such as wound healing, drug delivery, bone regeneration, tubular scaffolding, skin, nerve, kidney, and cardiac tissue engineering. In this review an outline of electrospinning is shown with critical summary of literature evaluated with respect to the various applications of nanofibers-derived gelatin.

2-Hydroxyethyl Methacrylate/Gelatin/Alginate Scaffolds Reinforced with Nano TiO2 as a Promising Curcumin Release Platform

The idea of this study was to create a new scaffolding system based on 2-hydroxyethyl methacrylate, gelatin, and alginate that contains titanium(IV) oxide nanoparticles as a platform for the controlled release of the bioactive agent curcumin. The innovative strategy to develop hybrid scaffolds was the modified porogenation method. The effect of the scaffold composition on the chemical, morphology, porosity, mechanical, hydrophilicity, swelling, degradation, biocompatibility, loading, and release features of hybrid scaffolds was evaluated. A porous structure with interconnected pores in the range of 52.33–65.76%, favorable swelling capacity, fully hydrophilic surfaces, degradability to 45% for 6 months, curcumin loading efficiency above 96%, and favorable controlled release profiles were obtained. By applying four kinetic models of release, valuable parameters were obtained for the curcumin/PHEMA/gelatin/alginate/TiO2 release platform. Cytotoxicity test results depend on the composition of the scaffolds and showed satisfactory cell growth with visible cell accumulation on the hybrid surfaces. The constructed hybrid scaffolds have suitable high-performance properties, suggesting potential for further in vivo and clinical studies.

Preparation and Characterization of Nanocomposite Hydrogels Based on Self-Assembling Collagen and Cellulose Nanocrystals

Collagen (Col) hydrogels are an important biomaterial with many applications in the biomedical sector. However, deficiencies, including insufficient mechanical properties and a rapid rate of biodegradation, hamper their application. In this work, nanocomposite hydrogels were prepared by combining a cellulose nanocrystal (CNC) with Col without any chemical modification. The high-pressure, homogenized CNC matrix acts as nuclei in the collagen's self-aggregation process. The obtained CNC/Col hydrogels were characterized in terms of their morphology, mechanical and thermal properties and structure by SEM, rotational rheometer, DSC and FTIR, respectively. Ultraviolet-visible spectroscopy was used to characterize the self-assembling phase behavior of the CNC/Col hydrogels. The results showed an accelerated assembling rate with the increasing loading of CNC. The triple-helix structure of the collagen was preserved with a dosage of CNC of up to 15 wt%. The CNC/Col hydrogels demonstrated an improvement in both the storage modulus and thermal stability which is attributed to the interaction between the CNC and collagen by the hydrogen bonds.

Tendon Aging

Tendons are mechanosensitive connective tissues responsible for the connection between muscles and bones by transmitting forces that allow the movement of the body, yet, with advancing age, tendons become more prone to degeneration followed by injuries. Tendon diseases are one of the main causes of incapacity worldwide, leading to changes in tendon composition, structure, and biomechanical properties, as well as a decline in regenerative potential. There is still a great lack of knowledge regarding tendon cellular and molecular biology, interplay between biochemistry and biomechanics, and the complex pathomechanisms involved in tendon diseases. Consequently, this reflects a huge need for basic and clinical research to better elucidate the nature of healthy tendon tissue and also tendon aging process and associated diseases. This chapter concisely describes the effects that the aging process has on tendons at the tissue, cellular, and molecular levels and briefly reviews potential biological predictors of tendon aging. Recent research findings that are herein reviewed and discussed might contribute to the development of precision tendon therapies targeting the elderly population.

Identification of the Collagen Types Essential for Mammalian Breast Acinar Structures

Modeling human breast tissue architecture is essential to study the pathophysiological conditions of the breast. We report that normal mammary epithelial cells grown in human breast extracellular matrix (ECM) hydrogel formed acini structurally similar to those of human and pig mammary tissues. Type I, II, III and V collagens were commonly identified in human, pig, and mouse breast ECM. Mammary epithelial cells formed acini on certain types or combinations of the four collagens at normal levels of breast tissue elasticity. Comparison of the collagen species in mouse normal breast and breast tumor ECM revealed common and distinct sets of collagens within the two types of tissues. Elevated expression of collagen type I alpha 1 chain (Col1a1) was found in mouse and human breast cancers. Collagen type XXV alpha 1 chain (Col25a1) was identified in mouse breast tumors but not in normal breast tissues. Our data provide strategies for modeling human breast pathophysiological structures and functions using native tissue-derived hydrogels and offer insight into the potential contributions of different collagen types in breast cancer development.

Textural modification of Chinese traditional stewed pig trotter: Effect of acid or alkaline-induced degradation of collagen fibers

This study aimed to investigate the effects of acid or alkaline treatments on the textural properties of Chinese traditional stewed pig trotter in relation to the degradation of collagen fibers. Pig trotters were subjected to different pHs of 4, 5, 6, 7, and 8 and then stewed at 95°C for 60 min. Textural parameters (springiness, chewiness, hardness, and gumminess) of pig trotters and Raman spectroscopy, cross-links, decorin, and glycosaminoglycans contents of collagen fibers were assessed. The acid or alkaline treatments at pH 4, 5, 6, and 8 improved the textural properties evidenced by lower chewiness, hardness, and gumminess, and promoted the unfolding of the secondary structure evidenced by a loss of α-helix paralleled with an increase of random coil, as well as induced a breakage to the covalent cross-links evidenced by the reduction of cross-links, decorin, and glycosaminoglycans. This study thus concluded positive effects of acid or alkaline treatments on the textural modification of Chinese traditional stewed pig trotter in relation to the induced degradation of the collagen fibers.

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.

Molecular Characteristics and Promoter Analysis of Porcine COL1A1

COL1A1 encodes the type I collagen α1 chain, which shows the highest abundance among members of the collagen family and is widely expressed in different mammalian cells and tissues. However, its molecular characteristics are not completely elucidated. In this study, the molecular profiles of COL1A1 and characteristics of the COL1A1 protein were investigated using a promoter activity assay and multiple bioinformatics tools. The results showed that the 5' flanking region of porcine COL1A1 contained two CpG islands, five core promoter sequences, and twenty-six transcription factor-binding sites. In the luciferase assay, the upstream 294 bp region of the initiation codon of COL1A1 showed the highest activity, confirming that this section is the core region of the porcine COL1A1 promoter. Bioinformatic analysis revealed that COL1A1 is a negatively charged, hydrophilic secreted protein. It does not contain a transmembrane domain and is highly conserved in humans, mice, sheep, and pigs. Protein interaction analysis demonstrated that the interaction coefficient of COL1A1 with COL1A2, COL3A1, ITGB1, and ITGA2 was greater than 0.9, suggesting that this protein plays a crucial role in collagen structure formation and cell adhesion. These results provide a theoretical basis for further investigation of the functions of porcine COL1A1.

Macrophages alter inflammatory and fibrotic gene expression in human vocal fold fibroblasts

Macrophage phenotypes are simplistically classified as pro-inflammatory (M1) or anti-inflammatory/pro-fibrotic (M2). Phenotypically different macrophages are putatively involved in vocal fold (VF) fibrosis. The current study investigated interactions between macrophages and VF fibroblasts. THP-1 monocyte-derived macrophages were treated with interferon-gamma (IFN-γ), lipopolysaccharide (LPS)/IFN-γ, interleukin-10 (IL10), transforming growth factor-β1 (TGF-β), or interleukin-4 (IL4) for 24 h (M(IFN), M(IFN/LPS), M(IL10), M(TGF), and M(IL4), respectively; M(-) denotes untreated macrophages). Differentially activated macrophages and human VF fibroblasts were co-cultured ± direct contact. Expression of CXCL10, CCN2, ACTA2, FN1, TGM2, and LOX was quantified by real-time polymerase chain reaction. Type I collagen and smooth muscle actin (SMA) were observed by immunofluorescence. CXCL10 and PTGS2 were upregulated in fibroblasts indirectly co-cultured with M(IFN) and M(IFN/LPS). M(TGF) stimulated CCN2, ACTA2, and FN1 in fibroblasts. Enzymes involved in extracellular matrix crosslinking (TGM2, LOX) were increased in monocultured M(IL4) compared to M(-). Direct co-culture with all macrophages increased type I collagen and SMA in fibroblasts. Macrophage phenotypic shift was consistent with stimulation and had downstream differential effects on VF fibroblasts. Direct contact with macrophages, regardless of phenotype, stimulated a pro-fibrotic response in VF fibroblasts. Collectively, these data suggest meaningful interactions between macrophages and fibroblasts mediate fibrosis.

Defining the versican interactome in lung health and disease

The extracellular matrix (ECM) imparts critical mechanical and biochemical information to cells in the lungs. Proteoglycans are essential constituents of the ECM and play a crucial role in controlling numerous biological processes, including regulating cellular phenotype and function. Versican, a chondroitin sulfate proteoglycan required for embryonic development, is almost absent from mature, healthy lungs and is reexpressed and accumulates in acute and chronic lung disease. Studies using genetically engineered mice show that the versican-enriched matrix can be pro- or anti-inflammatory depending on the cellular source or disease process studied. The mechanisms whereby versican develops a contextual ECM remain largely unknown. The primary goal of this review is to provide an overview of the interaction of versican with its many binding partners, the "versican interactome," and how through these interactions, versican is an integrator of complex extracellular information. Hopefully, the information provided in this review will be used to develop future studies to determine how versican and its binding partners can develop contextual ECMs that control select biological processes. Although this review focuses on versican and the lungs, what is described can be extended to other proteoglycans, tissues, and organs.

Liquid Crystal Modified Polylactic Acid Improves Cytocompatibility and M2 Polarization of Macrophages to Promote Osteogenesis

Liquid crystalline phases (LC phases) are widely present in an organism. The well-aligned domain and liquidity of the LC phases are necessary for various biological functions. How to stabilize the floating LC phases and maintain their superior biology is still under study. In addition, it is unclear whether the exogenous LC state can regulate the immune process and improve osteogenesis. In this work, a series of composite films (PLLA/LC) were prepared using cholesteryl oleyl carbonate (COC), cholesteryl pelargonate (CP), and polylactic acid (PLLA) via a controlled facile one-pot approach. The results showed that the thermo-responsive PLLA/LC films exhibited stable LC phases at human body temperature and the cytocompatibility of the composites was improved significantly after modification by the LC. In addition, the M2 polarization of macrophages (RAW264.7) was enhanced in PLLA/LC films, and the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) was improved as co-cultured with macrophages. The in vivo bone regeneration of the materials was verified by calvarial repair, in which the amount of new bone in the PLLA-30% LC group was greater than that in the PLLA group. This work revealed that the liquid crystal-modified PLLA could promote osteogenesis through immunomodulation.

Cloning, tissue distribution and mRNA expression of type I collagen alpha 1 gene from Chu's croaker (Nibea coibor)

The demand for collagen has been increasing over years due to its wide application in food, cosmetics and biomedicine industries. The synthesis of collagen protein in fish depends on instructions provided by collagen, type I, alpha 1 (COL1A1) gene. However, cloning, tissue distribution and mRNA expression of COL1A1 gene in a gel-producing Chu's croaker (Nibea coibor) is currently unknown. This study cloned the cDNA of COL1A1 gene (GenBank accession number: MK641512) from six N. coibor fish. The distribution and mRNA expression pattern of COL1A1 was analyzed in eight tissues of N. coibor. The COL1A1 cDNA had a full length of 6130 bp and contained a 4344 bp open reading frame (ORF) encoding a polypeptide of 1448 amino acids. The homology of N. coibor COL1A1 amino acid had 98% similarity with Larimichthys crocea, indicating conservatism with other members in same family (Sciaenidae). The deduced polypeptide contained the same signal peptides, C-propeptide and N-propeptide domains, and triple helix domains, which are the characteristics of type I collagen in vertebrates. The mRNA of COL1A1 gene was expressed significantly higher in the spine of N. coibor than in all other tissues (P < 0.05), followed by swim bladder, skin and scales. The swim bladder had higher collagen and hydroxyproline contents than other tissues, followed by spine >, scales > and > skin (P < 0.05). Our study successfully cloned the COL1A1 gene from N. coibor for the first time. The COL1A1 gene contained all the features of collagen pro-α1(I) chain proteins, and shared high homology with other marine teleost. COL1A1 gene in N. coibor is highly expressed in spine and swim bladder, consistent with collagen distribution. Our study contributes to better understanding on collagen biosynthesis in N. coibor tissues for various industrial uses.

Autologous hematopoietic stem cell transplantation promotes connective tissue remodeling in systemic sclerosis patients

BACKGROUND

Autologous hematopoietic stem cell transplantation (AHSCT) treats patients with severe and progressive systemic sclerosis (SSc). However, basic mechanisms associated with the therapeutic efficacy of the procedure are not entirely understood. We aimed to evaluate how AHSCT affects skin fibrosis in SSc patients.

METHODS

Clinical data, serum, and skin samples from 39 SSc patients who underwent AHSCT were retrospectively evaluated. Skin biopsies were analyzed by immunohistochemistry with anti-MMP-1, -MMP-2, -MMP-3, -MMP-9, -TIMP-1, -α-SMA, -TGF-β, and -NF-κB p65 antibodies, and stained with hematoxylin and eosin and picrosirius red to assess skin thickness and collagen density, respectively. Serum samples were evaluated by Multiplex Assay for COL1A1, COL4A1, FGF-1, MMP-1, MMP-3, MMP-12, MMP-13, PDGF-AA, PDGF-BB, S100A9, and TIMP-1 levels and compared to healthy controls.

RESULTS

After AHSCT, SSc patients showed clinical improvement in skin involvement, assessed by modified Rodnan's skin score (mRSS). Histologically, collagen density and skin thickness decreased after AHSCT. Immunohistochemical analyses showed increased expression of MMP-2, MMP-3, MMP-9, and TIMP-1 after AHSCT, whereas expression of NF-κB p65 decreased. At baseline, serum levels of COL4A1 and S100A9 were higher than in healthy controls. Serum levels of S100A9 normalized after AHCST in SSc patients compared to controls. Serum levels of PDGF-AA, PDGF-BB, TIMP-1, and MMP-1 decreased, while COL1A1 increased after AHSCT in SSc patients. No changes were detected in MMP-3, MMP-12, MMP-13, and FGF-1 serum levels after AHSCT.

CONCLUSIONS

Our results suggest that the therapeutic effects of AHSCT on skin fibrosis are related to changes in molecules associated with connective tissue maintenance and inflammation in SSc.

Integration Analysis of Transcriptome and Proteome Reveal the Mechanisms of Goat Wool Bending

Zhongwei goat is a unique Chinese native goat breed for excellent lamb fur. The pattern of flower spikes of the lamb fur was significantly reduced due to the reduction of the bending of the hair strands with growth. In order to explore the molecular mechanism underlying hair bending with growth, we performed the comprehensive analysis of transcriptome and proteome of skins from 45-days, 108-days and 365-days goat based on TMT-based quantitative proteomics and RNA-seq methods. In the three comparison groups, 356, 592 and 282 differentially expressed proteins (DEPs) were screened, respectively. KEGG pathway analysis indicated that DEPs were significantly enriched in a set of signaling pathways related to wool growth and bending, such as ECM-receptor interaction, PI3K-Akt signaling pathway, PPAR signaling pathway, protein digestion and absorption, and metabolic pathways. In addition, 20 DEPs abundance of goat skin at three development stages were examined by PRM method, which validated the reliability of proteomic data. Among them, KRT and collagen alpha family may play an important role in the development of goat hair follicle and wool bending. COL6A1, COL6A2, CRNN, TNC and LOC102178129 were identified as candidate genes based on combined analysis of transcriptome and proteome data and PRM quantification. Our results identify the differential expressed proteins as well as pathways related to the wool bending of Zhongwei goats and provide a theoretical basis for further revealing the molecular mechanism underlying wool bending of goats.

BMP1 is not required for lung fibrosis in mice

Bone morphogenetic protein 1 (BMP1) belongs to the astacin/BMP1/tolloid-like family of zinc metalloproteinases, which play a fundamental role in the development and formation of extracellular matrix (ECM). BMP1 mediates the cleavage of carboxyl terminal (C-term) propeptides from procollagens, a crucial step in fibrillar collagen fiber formation. Blocking BMP1 by small molecule or antibody inhibitors has been linked to anti-fibrotic activity in the preclinical models of skin, kidney and liver fibrosis. Therefore, we reason that BMP1 may be important for the pathogenesis of lung fibrosis and BMP1 could be a potential therapeutic target for progressive fibrotic disease such as idiopathic pulmonary fibrosis (IPF). Here, we observed the increased expression of BMP1 in both human IPF lungs and mouse fibrotic lungs induced by bleomycin. Furthermore, we developed an inducible Bmp1 conditional knockout (cKO) mouse strain. We found that Bmp1 deletion does not protect mice from lung fibrosis triggered by bleomycin. Moreover, we found no significant impact of BMP1 deficiency upon C-term propeptide of type I procollagen (CICP) production in the fibrotic mouse lungs. Based on these results, we propose that BMP1 is not required for lung fibrosis in mice and BMP1 may not be considered a candidate therapeutic target for IPF.

Microscale Creep and Stress Relaxation Experiments with Individual Collagen Fibrils

Nanoscale macromolecular biological structures exhibit time-dependent behavior, yet a quantitative understanding of their time-dependent mechanical behavior remains elusive, largely due to experimental challenges in attaining sufficient spatial and temporal resolution and control of stress or strain in conditions that guarantee their molecular integrity. To address this gap, an experimental methodology was developed to conduct creep and stress relaxation experiments with individual mammalian collagen fibrils. An image-based edge detection method implemented with high magnification optical microscopy and combined with closed-loop proportional-integral-derivative (PID) control was implemented and calibrated to apply constant force or stretch ratio values to individual collagen fibrils via a Microelectromechanical Systems (MEMS) device. This experimental methodology allowed for real-time control of uniaxial tensile stress or strain with 27 nm displacement resolution. The overall experimental system was tuned to apply step inputs with rise times below 0.5 s, less than 2.5% overshoot, and steady-state error less than 0.5%. Three individual collagen fibrils with diameters 101-121 nm were subjected to creep and stress relaxation tests in the range 4-20% engineering strain, under partially hydrated conditions. The collagen fibrils demonstrated non-linear viscoelastic behavior that was described well by the adaptive quasi-linear viscoelastic model. The results of this study demonstrate for the first time that mammalian collagen fibrils, the building blocks of connective tissues, exhibit nonlinear viscoelastic behavior in their partially hydrated state.

ER-to-Golgi trafficking of procollagen III via conventional vesicular and tubular carriers

Collagen is the major protein component of the extracellular matrix. Synthesis of procollagens starts in the endoplasmic reticulum (ER), and three ⍺ chains form a rigid triple helix 300-400 nm in length. It remains unclear how such a large cargo is transported from the ER to the Golgi apparatus. In this study, to elucidate the intracellular transport of fibril-forming collagens, we fused cysteine-free GFP to the N-telopeptide region of procollagen III (GFP-COL3A1) and analyzed transport by live-cell imaging. We found that the maturation dynamics of procollagen III were largely different from those of network-forming procollagen IV (Matsui et al. 2020). Proline hydroxylation of procollagen III uniquely triggered the formation of intralumenal droplet-like structures similar to events caused by liquid-liquid phase separation, and ER exit sites surrounded large droplets containing chaperones. Procollagen III was transported to the Golgi apparatus via vesicular and tubular carriers containing ERGIC53 and RAB1B; this process required TANGO1 and CUL3, which we previously reported were dispensable for procollagen IV. GFP-COL3A1 and mCherry-⍺1AT were co-transported in the same vesicle. Based on these findings, we propose that shortly after ER exit, enlarged carriers containing procollagen III fuse to ERGIC for transport to the Golgi apparatus by conventional cargo carriers. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].

Segment-Long-Spacing (SLS) and the Polymorphic Structures of Fibrillar Collagen

The diverse and complex functions of collagen during the development of an organism are closely related to the polymorphism of its supramolecular structures in the extracellular matrix. SLS (segment-long-spacing) is one of the best understood alternative structures of collagen. SLS played an instrumental role in the original studies of collagen more than half a century ago that laid the foundation of nearly everything we know about collagen today. Despite being used mostly under in vitro conditions, the natural occurrence of SLS in tissues has also been reported. Here we will provide a brief overview of the major findings of the SLS and other structures of collagen based on a wealth of work published starting from the 1940s. We will discuss the factors that determine the stability and the structural specificity of the different molecular assemblies of collagen in light of the new studies using designed fibril forming collagen peptides. At the end of the chapter, we will summarize some recent discoveries of the alternative structures of collagen in tissues, especially those involved in pathogenic states. A revisit of SLS will likely inspire new understandings concerning the range of critical roles of fibrillar collagen in terms of its organizational diversity in the extracellular matrix.

Collagen I in the Hip Capsule Plays a Role in Postoperative Clinical Function in Patients With Developmental Dysplasia of the Hip

The aims of the present study is to evaluate the roles of collagen I and III in the hip capsule in the postoperative clinical function of patients with developmental dysplasia of the hip (DDH). Hip capsules from 155 hips of 120 patients were collected during surgery. The patients were divided into three groups according to age: I: 2-3.5 years; II: 3.5-5 years; and III: 5-6 years. Patient clinical function and radiographic outcomes were evaluated with the McKay scores and Severin classification. The expression of collagen I and III was detected through immunohistochemistry and quantitative reverse transcription polymerase chain reaction (RT-PCR) and analyzed according to age, sex, degree of dislocation and McKay classification. All patients received open reduction and pelvic osteotomy and/or femoral shortening osteotomy and achieved good results on the basis of postoperative X-ray imaging. The average follow-up time was 3.4 years (range 2-4.3 years). There were no changes in the expression of collagen III in the different groups. The expression of collagen I according to age and sex was not significantly different. Lower expression of collagen I was observed in DDH patients with a higher degree of dislocation according to the Tonnis grade. The highest expression of collagen I was detected in the group with poor clinical function according to the McKay classification. Collagen I is correlated with the degree of dislocation and is a risk factor for poor clinical function in DDH patients. Collagen I is correlated with the degree of hip dislocation and poor clinical function in DDH patients.

Basic Structure, Physiology, and Biochemistry of Connective Tissues and Extracellular Matrix Collagens

The physiology of connective tissues like tendons and ligaments is highly dependent upon the collagens and other such extracellular matrix molecules hierarchically organized within the tissues. By dry weight, connective tissues are mostly composed of fibrillar collagens. However, several other forms of collagens play essential roles in the regulation of fibrillar collagen organization and assembly, in the establishment of basement membrane networks that provide support for vasculature for connective tissues, and in the formation of extensive filamentous networks that allow for cell-extracellular matrix interactions as well as maintain connective tissue integrity. The structures and functions of these collagens are discussed in this chapter. Furthermore, collagen synthesis is a multi-step process that includes gene transcription, translation, post-translational modifications within the cell, triple helix formation, extracellular secretion, extracellular modifications, and then fibril assembly, fibril modifications, and fiber formation. Each step of collagen synthesis and fibril assembly is highly dependent upon the biochemical structure of the collagen molecules created and how they are modified in the cases of development and maturation. Likewise, when the biochemical structures of collagens or are compromised or these molecules are deficient in the tissues - in developmental diseases, degenerative conditions, or injuries - then the ultimate form and function of the connective tissues are impaired. In this chapter, we also review how biochemistry plays a role in each of the processes involved in collagen synthesis and assembly, and we describe differences seen by anatomical location and region within tendons. Moreover, we discuss how the structures of the molecules, fibrils, and fibers contribute to connective tissue physiology in health, and in pathology with injury and repair.

Glycation of Host Proteins Increases Pathogenic Potential of Porphyromonas gingivalis

The non-enzymatic addition of glucose (glycation) to circulatory and tissue proteins is a ubiquitous pathophysiological consequence of hyperglycemia in diabetes. Given the high incidence of periodontitis and diabetes and the emerging link between these conditions, it is of crucial importance to define the basic virulence mechanisms employed by periodontopathogens such as Porphyromonas gingivalis in mediating the disease process. The aim of this study was to determine whether glycated proteins are more easily utilized by P. gingivalis to stimulate growth and promote the pathogenic potential of this bacterium. We analyzed the properties of three commonly encountered proteins in the periodontal environment that are known to become glycated and that may serve as either protein substrates or easily accessible heme sources. In vitro glycated proteins were characterized using colorimetric assays, mass spectrometry, far- and near-UV circular dichroism and UV-visible spectroscopic analyses and SDS-PAGE. The interaction of glycated hemoglobin, serum albumin and type one collagen with P. gingivalis cells or HmuY protein was examined using spectroscopic methods, SDS-PAGE and co-culturing P. gingivalis with human keratinocytes. We found that glycation increases the ability of P. gingivalis to acquire heme from hemoglobin, mostly due to heme sequestration by the HmuY hemophore-like protein. We also found an increase in biofilm formation on glycated collagen-coated abiotic surfaces. We conclude that glycation might promote the virulence of P. gingivalis by making heme more available from hemoglobin and facilitating bacterial biofilm formation, thus increasing P. gingivalis pathogenic potential in vivo.

The dispersion of viscoelastic properties of fascicle bundles within the tendon results from the presence of interfascicular matrix and flow of body fluids

In this work, we investigate differences in the mechanical and structural properties of tendon fascicle bundles dissected from different areas of bovine tendons. The properties of tendon fascicle bundles were investigated by means of uniaxial tests with relaxation periods and hysteresis, dynamic mechanical analysis (DMA), as well as magnetic resonance imaging (MRI). Uniaxial tests with relaxation periods revealed greater elastic modulus, hysteresis, as well as stress drop during the relaxation of samples dissected from the posterior side of the tendon. However, the normalized stress relaxation curves did not show a statistically significant difference in the stress drop between specimens cut from different zones or between different strain levels. Using dynamic mechanical analysis, we found that fascicle bundles dissected from the anterior side of the tendon had lower storage and loss moduli, which could result from altered fluid flow within the interfascicular matrix (IFM). The lower water content, diffusivity, and higher fractional anisotropy of the posterior part of the tendon, as observed using MRI, indicates a different structure of the IFM, which controls the flow of fluids within the tendon. Our results show that the viscoelastic response to dynamic loading is correlated with fluid flow within the IFM, which was confirmed during analysis of the MRI results. In contrast to this, the long-term relaxation of tendon fascicle bundles is controlled by viscoplasticity of the IFM and depends on the spatial distribution of the matrix within the tendon. Comparison of results from tensile tests, DMA, and MRI gives new insight into tendon mechanics and the role of the IFM. These findings may be useful in improving the diagnosis of tendon injury and effectiveness of medical treatments for tendinopathies.

Collagen deposition correlates with loss of E-cadherin and increased p63 expression in dysplastic conditions of oral submucous fibrosis

This paper focuses on the status of epithelial markers, E-cadherin, and p63 in the backdrop of an abnormal amount of collagen in the sub-mucosa of dysplastic and non-dysplastic grades of OSF. Histologically confirmed OSF and normal oral mucosa samples were procured. Samples were stained by Van Gieson's stain (VG) and immunohistochemistry. The captured images were analyzed by ImageJ software to quantify their grayscale intensities. There was a gradual increase in the intensity of VG stain from normal to non-dysplastic and dysplastic OSF and the differences in their mean grayscale values were found to be significant (p < 0.00001). The intensity of E-cadherin was found to be the highest in non-dysplastic conditions and lowest in dysplastic conditions. The intensity difference of E-cadherin between normal and non-dysplastic OSF was found to be significant (p < 0.00001). The grayscale scale intensity values for p63 in whole epithelium depicted significant differences between normal and diseased conditions but for its intensity, in basal cells, significant differences were found between non-dysplastic and other classes of tissues. There was a positive correlation observed between VG and p63 staining intensity. The diseased oral epithelium demonstrated greater deposition of sub-epithelial collagen fibers along with subsequent loss of E-cadherin and an increased p63 expression.

Collagen Fibrillogenesis in the Mitral Valve: It's a Matter of Compliance

Collagen fibers are essential structural components of mitral valve leaflets, their tension apparatus (chordae tendineae), and the associated papillary muscles. Excess or lack of collagen fibers in the extracellular matrix (ECM) in any of these structures can adversely affect mitral valve function. The organization of collagen fibers provides a sophisticated framework that allows for unidirectional blood flow during the precise opening and closing of this vital heart valve. Although numerous ECM molecules are essential for the differentiation, growth, and homeostasis of the mitral valve (e.g., elastic fibers, glycoproteins, and glycans), collagen fibers are key to mitral valve integrity. Besides the inert structural components of the tissues, collagen fibers are dynamic structures that drive outside-to-inside cell signaling, which informs valvular interstitial cells (VICs) present within the tissue environment. Diversity of collagen family members and the closely related collagen-like triple helix-containing proteins found in the mitral valve, will be discussed in addition to how defects in these proteins may lead to valve disease.

Modelling fibroid pathology: development and manipulation of a myometrial smooth muscle cell macromolecular crowding model to alter extracellular matrix deposition

Current treatment options for uterine fibroids are limited to hormonal manipulation or surgical intervention. We aimed to develop an in vitro model to mirror collagen deposition and extracellular matrix (ECM) formation, the principal features of uterine fibroids, to enable testing of novel therapeutics. Macromolecular crowding with Ficoll 400 and Ficoll 70 in cultures of human uterine myometrial smooth muscle cells containing ascorbic acid, provided the basis for this model. These culture conditions mimic the 'crowded' nature of the in vivo extracellular environment by incorporating neutral, space-filling macromolecules into conventional cell cultures. This method of culture facilitates appropriate ECM deposition, thus closely representing the in vivo fibrotic phenotype of uterine fibroids. Macromolecular crowding in Ficoll cultures containing ascorbic acid reduced myometrial smooth muscle cell proliferation and promoted collagen production. Under these conditions, collagen was processed for extracellular deposition as demonstrated by C-propeptide cleavage from secreted procollagen. The fibrosis marker activin was increased relative to its natural inhibitor, follistatin, in crowded culture conditions while addition of exogenous follistatin reduced collagen (Col1A1) gene expression. This in vitro model represents a promising development for the testing of therapeutic interventions for uterine fibroids. However, it does not recapitulate the full in vivo pathology which can include specific genetic and epigenetic alterations that have not been identified in the myometrial smooth muscle (hTERT-HM) cell line. Following screening of potential therapeutics using the model, the most promising compounds will require further assessment in the context of individual subjects including those with genetic changes implicated in fibroid pathogenesis.

Polarimetric data-based model for tissue recognition

We highlight the potential of a predictive optical model method for tissue recognition, based on the statistical analysis of different polarimetric indicators that retrieve complete polarimetric information (selective absorption, retardance and depolarization) of samples. The study is conducted on the experimental Mueller matrices of four biological tissues (bone, tendon, muscle and myotendinous junction) measured from a collection of 157 ex-vivo chicken samples. Moreover, we perform several non-parametric data distribution analyses to build a logistic regression-based algorithm capable to recognize, in a single and dynamic measurement, whether a sample corresponds (or not) to one of the four different tissue categories.

The physiological activity of bioactive peptides obtained from meat and meat by-products

Meat and meat products constitute an important source of nutrients and play vital roles for growth, maintenance and repair of the body. In addition to the high quality of proteins, meat is also regarded as a major resource to produce bioactive peptides. Meat processing industry also produces by-products such as bones, blood and viscera, which could be further used for the production of bioactive compounds. In the physiological analysis, meat bioactive peptides have been reported to exert antioxidant, anti-hypertensive, anti-inflammatory, anti-microbial and antitumoral activities, which endow nutritional and functional value of meat. With the objective to exert the functional effect, the bioavailability should also be considered due to the degradation by digestion enzymes and the absorption process in intestinal mucosa. In this chapter, the general source, the enzymatic hydrolysis, the physiological effects as well as the bioavailability of bioactive peptides in meat are discussed.