Remodeling Of Collagen Fibers Research Articles

Cucumber‐Derived Extracellular Vesicle‐Functionalized Metal‐Organic Frameworks for Enhanced Photodynamic Therapy of Hypertrophic Scars

AbstractPhotodynamic therapy (PDT) with noninvasiveness and high safety has emerged as a promising therapeutic approach for the management of hypertrophic scars (HS). However, the low transdermal delivery and overexpressed levels of intracellular glutathione (GSH) severely hinder its therapeutic effectiveness. Herein, a multifunctional biomimetic nanoplatform (NDs@EV‐RGD) composed of arginine‐glycine‐aspartic acid (RGD)‐modified cucumber‐derived extracellular vesicles (EVs) and copper‐based metal‐organic framework nanodots (Cu‐MOF NDs) is designed for PDT‐mediated HS treatment. The EVs with low Young's modulus exhibit excellent deformability which endow NDs@EV‐RGD with the capacity to overcome the compact stratum corneum barrier, thereby significantly improving their transdermal delivery efficiency. Notably, the RGD targeting peptide displays specific binding to α1β1 integrin on the fibroblast membranes within HS, leading to the high accumulation efficiency of NDs@EV‐RGD at the HS site. Under near‐infrared laser irradiation, NDs@EV‐RGD efficiently generates abundant reactive oxygen species, inducing the apoptosis of excessively proliferated fibroblasts. Moreover, Cu‐MOF NDs interact with the local GSH, leading to GSH depletion and a significant enhancement in PDT efficacy. Furthermore, NDs@EV‐RGD demonstrates a remarkable therapeutic effect in improving the appearance of HS in a rabbit ear HS model, promoting the apoptosis and remodeling of collagen fibers. Therefore, this work provides a promising biomimetic platform for HS treatment.

Incorporation of Decidual Stromal Cells Derived Exosomes in Sodium Alginate Hydrogel as an Innovative Therapeutic Strategy for Advancing Endometrial Regeneration and Reinstating Fertility.

Intrauterine adhesion (IUA) stands as a prevalent medical condition characterized by endometrial fibrosis and scar tissue formation within the uterine cavity, resulting in infertility and, in severe cases, recurrent miscarriages. Cell therapy, especially with stem cells, offers an alternative to surgery, but concerns about uncontrolled differentiation and tumorigenicity limit its use. Exosomes, more stable and immunogenicity-reduced than parent cells, have emerged as a promising avenue for IUA treatment. In this study, a novel approach has been proposed wherein exosomes originating from decidual stromal cells (DSCs) are encapsulated within sodium alginate hydrogel (SAH) scaffolds to repair endometrial damage and restore fertility in a mouse IUA model. Current results demonstrate that in situ injection of DSC-derived exosomes (DSC-exos)/SAH into the uterine cavity has the capability to induce uterine angiogenesis, initiate mesenchymal-to-epithelial transformation (MET), facilitate collagen fiber remodeling and dissolution, promote endometrial regeneration, enhance endometrial receptivity, and contribute to the recovery of fertility. RNA sequencing and advanced bioinformatics analysis reveal miRNA enrichment in exosomes, potentially supporting endometrial repair. This finding elucidates how DSC-exos/SAH mechanistically fosters collagen ablation, endometrium regeneration, and fertility recovery, holding the potential to introduce a novel IUA treatment and offering invaluable insights into the realm of regenerative medicine.

Dynamic changes in mitral valve extracellular matrix, tissue mechanics and function in a mouse model of Marfan syndrome

ObjectiveMouse models of Marfan syndrome (MFS) with Fibrillin 1 (Fbn1) variant C1041G exhibit cardiovascular abnormalities, including myxomatous valve disease (MVD) and aortic aneurism, with structural extracellular matrix (ECM) dysregulation. In this study, we examine the structure-function-mechanics relations of the mitral valve related to specific transitions in ECM composition and organization in progressive MVD in MFS mice from Postnatal day (P)7 to 1 year-of-age. Approach and resultsMechanistic links between mechanical forces and biological changes in MVD progression were examined in Fbn1C1041G/+ MFS mice. By echocardiography, mitral valve dysfunction is prevalent at 2 months with a decrease in cardiac function at 6 months, followed by a preserved cardiac function at 12 months. Mitral valve (MV) regurgitation occurs in a subset of mice at 2–6 months, while progressive dilatation of the aorta occurs from 2 to 12 months. Mitral valve tissue mechanical assessments using a uniaxial Permeabilizable Fiber System demonstrate decreased stiffness of MFS MVs at all stages. Histological and microscopic analysis of ECM content, structure, and fiber orientation demonstrate that alterations in ECM mechanics, composition, and organization precede functional abnormalities in Fbn1C1041G/+MFS MVs. At 2 months, ECM abnormalities are detected with an increase in proteoglycans and decreased stiffness of the mitral valve. By 6–12 months, collagen fiber remodeling is increased with abnormal fiber organization in MFS mitral valve leaflets. At the same time, matrifibrocyte gene expression characteristic of collagen-rich connective tissue is increased, as detected by RNA in situ hybridization and qPCR. Together, these studies demonstrate early prevalence of proteoglycans at 2 months followed by upregulation of collagen structure and organization with age in MVs of MFS mice. ConclusionsAltogether, our data indicate dynamic regulation of mitral valve structure, tissue mechanics, and function that reflect changes in ECM composition, organization, and gene expression in progressive MVD. Notably, increased collagen fiber organization and orientation, potentially dependent on increased matrifibrocyte cell activity, is apparent with altered mitral valve mechanics and function in aging MFS mice.

Tissue and Cell Dual‐Penetrating Dendritic Lipopeptide Liposomes for Hypertrophic Scar Treatment

AbstractHypertrophic scar is a complex global disease, which can lead to remarkable functional impairment, pruritus, and pain. Treating local skin diseases needs a transdermal drug delivery system that can simultaneously promote cell and tissue penetration within the hypertrophic scar. Herein, a tissue and cell dual‐penetrating liposomal delivery platform consisting of arginine‐based dendritic lipopeptide mimicking the pivotal amino acid sequence in viral protein transduction domains and virion‐like nanostructure to enhance hypertrophic scar tissue deep penetration and cellular internalization is reported. This dendritic lipopeptide liposomal delivery platform can overcome corneum barriers to the punch on hypertrophic scar fibroblast membranes, as are natural viruses. It also can deeply deliver drugs to promote hypertrophic scar fibroblast apoptosis and collagen fiber remodeling within thickened dermis and epidermis, and finally remove the raised scars.

Fibroblasts alter the physical properties of dermal ECM-derived hydrogels to create a pro-angiogenic microenvironment

This study aimed to investigate the impact of fibroblasts (MRC-5) on the extracellular matrix (ECM) microenvironment of endothelial cells (ECs) during the vascularization of skin-derived ECM hydrogel in vitro. Two types of ECs were studied: human dermal microvascular endothelial cells (HMEC) and human pulmonary microvascular endothelial cells (HPMEC). Results showed that the presence of MRC-5 fibroblasts increased the stiffness of the hydrogel and led to larger fiber diameters and increased porosity. Extensive collagen fiber remodeling occurred in the ECM hydrogel with MRC-5 fibroblasts. Additionally, higher levels of fibulin-1 and fibronectin were deposited in the hydrogel when co-cultured with MRC-5 fibroblasts. These findings suggest that MRC-5 fibroblasts play a role in modifying the ECM microenvironment, promoting vascularization through dynamic ECM remodeling.

Evaluation of the tissue repair process and immunomodulatory action of Platelet-Rich Plasma (PRP) in the treatment of abdominal stretch marks

The aims of this study were to characterize and to compare the structural alterations of collagen and elastic fibers in the abdominal stretch marks of patients submitted to intralesional and per quadrant (region close to stretch marks) Platelet-Rich Plasma (PRP) treatment, as well as, to establish the possible mechanisms of action of this treatment involving toll-like receptors (TLRs) signaling pathways and growth factors. Incisional biopsies were collected from abdominal stretch marks with a 2 mm diameter punch in female patients, at the beginning of treatment, after 6 and 12 weeks of treatment, and submitted to morphological analyzes of elastic and collagen fibers, and immunohistochemistry for TLRs signaling pathways and growth factors. Our results demonstrated PRP per quadrant treatment was most effective in reducing the area of the abdominal stretch marks, with consequent stimulation of the synthesis and remodeling of collagen and elastic fibers. Also, PRP per quadrant treatment promoted an increase in TLR2 and TLR4 immunoreactivities, with consequent increase in TNF-α, VEGF and IGF-1. Based on the current findings, PRP constitutes a promising therapeutic approach in patients with stretch marks, since it promoted modulation of inflammatory cytokines and growth factors, with consequent remodeling of extracellular matrix, culminating with tissue improvement.

Endometrial fibrosis in mares: Picrosirius Red and Collagen-2 and 3

In mares, endometrial fibrosis results from abnormal collagen deposition in the stroma and around the endometrial glands. The pathogenesis of endometrial fibrosis remains unknown, but the different types of collagens are a fundamental part of the process. The Picrosirius Red (PSR) staining is widely studied and necessary for collagen fiber and tissue remodeling. The present study aimed to determine the collagen deposition and the gene expression of collagen-2(COL-2) and collagen-3(COL-3) in the endometrium of mares with different degrees of fibrosis. Cyclic mares (n = 34) with a mean age of 14 ± 6.4 years old were used. A uterine biopsy from each mare was obtained at diestrus (D5–D10). Mares were grouped according to the degree of uterine fibrosis described by Kenney (1978): Grade I (n = 12), Grade II (n = 12), and Grade III (n = 10). Collagen in the equine endometrium was morphometrically quantified under PSR staining. The morphometric quantification of the images was performed from each sample after digital microphotographs were taken at 200x magnification, processed, and evaluated using the ImageJ 1.52a software. COL-2 and COL-3 expression was performed using qPCR. Grades were considered independent factors. Collagen-stained area and transcript expression were considered dependent factors. Data were analyzed with ANOVA andt-test. A Pearson correlation was performed between age and collagen deposition. The percentage of tissue collagen area stained with PSR revealed a significant increase between all groups in collagen deposition according to the degree of fibrosis: Grade I (11.7 ± 1.4%), Grade II (17.8 ± 1.3%), and Grade III (24.1 ± 1.9%). Age and the percentage of collagen deposited in the endometrial tissue correlated (r = 0.5) (P = 0.015). Grade II samples presented higher expression of COL-2 transcripts compared to Grade I (P = 0.026) and Grade III (P = 0.003). However, COL-3 did not show differences between groups. This study agrees with other studies that indicate that the worsening of degenerative changes coincides with advanced mare age. Sample evaluations emphasizing degenerative changes rely on an experienced evaluator, while the PSR, followed by computerized analysis, presents quantitative data. In conclusion, the increase in PSR analysis in Grade II and Grade III mares compared to Grade I demonstrates that this technique could play an important role in routine analyses for the detection, quantification, and dynamics of collagen in specific tissues. The study revealed that COL-2 might be involved in the progression and differentiation of healthy endometrium into an endometrium with severe fibrosis.

Mapping the 3D remodeling of the extracellular matrix in human hypertrophic scar by multi-parametric multiphoton imaging using endogenous contrast

The hypertrophic scar is an aberrant form of wound healing process, whose clinical efficacy is limited by a lack of understanding of its pathophysiology. Remodeling of collagen and elastin fibers in the extracellular matrix (ECM) is closely associated with scar progression. Herein, we perform label-free multiphoton microscopy (MPM) of both fiber components from human skin specimens and propose a multi-fiber metrics (MFM) analysis model for mapping the structural remodeling of the ECM in hypertrophic scars in a highly-sensitive, three-dimensional (3D) manner. We find that both fiber components become wavier and more disorganized in scar tissues, while content accumulation is observed from elastin fibers only. The 3D MFM analysis can effectively distinguish normal and scar tissues with better than 95% in accuracy and 0.999 in the area under the curve value of the receiver operating characteristic curve. Further, unique organizational features with orderly alignment of both fibers are observed in scar-normal adjacent regions, and an optimized combination of features from 3D MFM analysis enables successful identification of all the boundaries. This imaging and analysis system uncovers the 3D architecture of the ECM in hypertrophic scars and exhibits great translational potential for evaluating scars in vivo and identifying individualized treatment targets.

Utilizing micro-CT imaging to define collagen modeling in murine aorta.

We aim to demonstrate local aortic tissue biodynamics via collagen and elastin fiber remodeling in murine aorta at varying distension using microcomputed tomography (microCT). Ten week-old C57BL/6 mice were injected via tail vein with in-vivo collagen hybridizing peptide, which reforms the triple-helix structure of denatured collagen, and is visualized via fluorescein tag. Careful dissection and removal of the thoracoabdominal aorta was performed, which was pressurized with formalin at varying distensions. Samples were then prepared via heavy-metal staining, and fixed in epoxy resin. These were subsequently imaged at the microCT scanner at University of Chicago, as well as at the 2-BM-B beamline using the Advanced Photon Source at Argonne National Laboratory to obtain micron and sub-micron resolution images and thus provide multi-level views of the tissue. Clear visualization of distinct collagen and elastin layers was observed with microCT. The images also clearly illustrate the effect on individual collagen and elastin fiber organization created by overdistension and shear-stress on the aorta. Clear demonstration of the geometric structure of aortic elastin fibers was seen upon initial segmentation. Preliminary experiments demonstrate that microCT provides an excellent visualization of murine aorta at micron and submicron levels. Next steps will be to segment and mesh this data in order to simulate local tissue responses to stress via finite element analysis. This method will produce a multi-scale imaging model of aortic failure.

Three-dimensional remodeling of collagen fibers within cervical tissues in pregnancy

The cervix is a collagen-rich connective tissue that must remain closed during pregnancy while undergoing progressive remodeling in preparation for delivery, which begins before the onset of the preterm labor process. Therefore, it is important to resolve the changes of collagen fibers during cervical remodeling for the prevention of preterm labor. Herein, we assessed the spatial organization of collagen fibers in a three-dimensional (3D) context within cervical tissues of mice on day 3, 9, 12, 15 and 18 of gestation. We found that the 3D directional variance, a novel metric of alignment, was higher on day 9 than that on day 3 and then gradually decreased from day 9 to day 18. Compared with two-dimensional (2D) approach, a higher sensitivity was achieved from 3D analysis, highlighting the importance of truly 3D quantification. Moreover, the depth-dependent variation of 3D directional variance was investigated. By combining multiple 3D directional variance-derived metrics, a high level of classification accuracy was acquired in distinguishing different periods of pregnancy. These results demonstrate that 3D directional variance is sensitive to remodeling of collagen fibers within cervical tissues, shedding new light on highly-sensitive, early detection of preterm birth (PTB).

Inelastic material formulations based on a co-rotated intermediate configuration—Application to bioengineered tissues

In the field of material modeling, there is a general trend to include more and more complex phenomena in the modeling, making the models’ theoretical derivation and numerical implementation extremely difficult. In particular, modeling inelastic material behavior under finite deformations in a continuum mechanical manner, e.g. to simulate soft biological tissues, remains one of the most challenging tasks. Unfortunately, the multiplicative decomposition of the deformation gradient usually utilized in this context suffers from an inherent rotational non-uniqueness, making it not straightforward to combine this approach with algorithmic differentiation (AD)—a very helpful tool in modern computational mechanics. To address this issue in the growth and remodeling model proposed herein, a novel co-rotated intermediate configuration is introduced. This configuration shares essential characteristics with the intermediate one, but is uniquely defined and applicable to a wide range of inelastic materials. In this regard, the concept of structural tensors, hardening effects, and a thermodynamically consistent derivation are discussed as well. Since the stress-driven growth model presented is based on the approach of homeostatic surfaces by Lamm et al. (2022), a large number of derivatives of potentials and energies are required, which can be elegantly implemented using AD due to the co-rotated formulation. Moreover, fiber remodeling of collagen fibers is taken into account in a stress-driven manner using AD. Finally, qualitative comparisons are made with recently published experiments by Eichinger et al. (2020) in uniaxial and multiaxial settings, revealing the efficient combination of the proposed framework and the material model.

Optimization of an Ex-Vivo Human Skin/Vein Model for Long-Term Wound Healing Studies: Ground Preparatory Activities for the 'Suture in Space' Experiment Onboard the International Space Station.

This study is preliminary to an experiment to be performed onboard the International Space Station (ISS) and on Earth to investigate how low gravity influences the healing of sutured human skin and vein wounds. Its objective was to ascertain whether these tissue explants could be maintained to be viable ex vivo for long periods of time, mimicking the experimental conditions onboard the ISS. We developed an automated tissue culture chamber, reproducing and monitoring the physiological tensile forces over time, and a culture medium enriched with serelaxin (60 ng/mL) and (Zn(PipNONO)Cl) (28 ng/mL), known to extend viability of explanted organs for transplantation. The results show that the human skin and vein specimens remained viable for more than 4 weeks, with no substantial signs of damage in their tissues and cells. As a further clue about cell viability, some typical events associated with wound repair were observed in the tissue areas close to the wound, namely remodeling of collagen fibers in the papillary dermis and of elastic fibers in the vein wall, proliferation of keratinocyte stem cells, and expression of the endothelial functional markers eNOS and FGF-2. These findings validate the suitability of this new ex vivo organ culture system for wound healing studies, not only for the scheduled space experiment but also for applications on Earth, such as drug discovery purposes.

Moderate intestinal immunopathology after acute oral infection with Toxoplasma gondii oocysts is associated with expressive levels of serotonin

BackgroundInvasion of the intestinal mucosa by T. gondii elicits a local immune response of variable intensity. These reactions can be lethal in C57BL/6 mice. The tissue damage caused by inflammation and the functional effects depend on the host immunity, strain, and developmental form of the parasite. We investigated the effects of acute oral infection with T. gondii on histoarchitecture, enteric nervous system (ENS), and inflammatory markers in the jejunum and ileum of mice. MethodsFemale C57BL/6 mice were divided into a control group and a group orally infected with 1000 sporulated T. gondii oocysts (ME-49 strain). After 5 days, jejunum and ileum were collected and processed for analyzes (e.g., histological and histopathological examinations, ENS, cytokine dosage, myeloperoxidase, nitric oxide activity). Main resultsIn infected mice, we observed a significant increase in serotonin-immunoreactive cells (5-HT IR) in the intestinal mucosa, as well as cellular infiltrates in the lamina propria, periganglionitis, and ganglionitis in the myenteric plexus. We also noted decreased neuron density in the jejunum, increased population of enteric glial cells in the ileum, histomorphometric changes in the intestinal wall, villi, and epithelial cells, remodeling of collagen fibers, and increased myeloperoxidase activity, cytokines, and nitric oxide in the intestine. Conclusions and inferencesAcute infection of female mice with T. gondii oocysts resulted in changes in ENS and a marked increase in 5-HT. These changes are consistent with its modulatory role in the development of moderate acute inflammation. The use of this experimental model may lend itself to studies aimed at understanding the pathophysiological mechanisms of intestinal inflammation in humans involving ENS.

Collagen and elastic fiber remodeling in the pregnant mouse myometrium†.

The myometrium undergoes progressive tissue remodeling from early to late pregnancy to support fetal growth and transitions to the contractile phase to deliver a baby at term. Much of our effort has been focused on understanding the functional role of myometrial smooth muscle cells, but the role of extracellular matrix is not clear. This study was aimed to demonstrate the expression profile of sub-sets of genes involved in the synthesis, processing, and assembly of collagen and elastic fibers, their structural remodeling during pregnancy, and hormonal regulation. Myometrial tissues were isolated from non-pregnant and pregnant mice to analyze gene expression and protein levels of components of collagen and elastic fibers. Second harmonic generation imaging was used to examine the morphology of collagen and elastic fibers. Gene and protein expressions of collagen and elastin were induced very early in pregnancy. Further, the gene expressions of some of the factors involved in the synthesis, processing, and assembly of collagen and elastic fibers were differentially expressed in the pregnant mouse myometrium. Our imaging analysis demonstrated that the collagen and elastic fibers undergo structural reorganization from early to late pregnancy. Collagen and elastin were differentially induced in response to estrogen and progesterone in the myometrium of ovariectomized mice. Collagen was induced by both estrogen and progesterone. By contrast, estrogen induced elastin, but progesterone suppressed its expression. The current study suggests progressive extracellular matrix remodeling and its potential role in the myometrial tissue mechanical function during pregnancy and parturition.

CO2 laser resurfacing for burn and traumatic scars of the hand and upper extremity.

BackgroundScar formation is a normal part of the proliferative phase in wound healing where collagen is remodelled to better approximate normal skin. When collagen is not effectively redistributed, excessive scarring may occur. Recently, CO2 laser has emerged as an adjunct in improving scar quality via remodelling and redistribution of dermal collagen fibres. Due to the paucity of literature related to its use in the hands and upper extremities, we created a study to examine its effects on hypertrophic scars focused on the hands and upper extremities.MethodsPatients treated with CO2 laser for hypertrophic scars of the hand and upper extremity were included. The Vancouver Scar Scale (VSS) and Patient and Observer Scar Assessment Scale (POSAS) were used to assess the progression of scar quality. Unpaired t-tests were performed to determine statistical difference between pre- and post-treatment scores on each scale. Pearson correlation coefficients were used to understand the relationship between number of treatments and scar quality.ResultsOf the 90 patients enrolled, 54 patients completed serial scar assessment forms. All patient and observer-reported POSAS domains showed improvement (P < 0.05) apart from Itching. All VSS domains showed improvement (P < 0.05). There was moderate correlation between overall patient-reported opinion of scar quality and Discoloration, Stiffness and Thickness, and strong correlation between overall patient opinion and Irregularity (r = 0.715). All observer-reported domains were strongly correlated (r = 7.56–8.74) with overall observer opinion of scar quality.ConclusionThe results of this study may further substantiate CO2 laser as a treatment modality for excessive scarring in a variety of surgical subspecialties.Lay SummaryComplex trauma and burns that impact the skin sometimes result in abnormal healing of the skin called, “hypertrophic scarring”. In our study we assessed how using focused CO2 laser therapy impacts patients and health care provider assessment of wound progression. Our results were based upon patient reported and healthcare provider observations based upon two standardized forms the Vancouver Scar Scale (VSS) and the Patient and Observer Scar Assessment Scale (POSAS). What we found is that after CO2 Laser Therapy, our 64 patients with 77 treated scars received on average almost 3 treatments and these treatments helped them with physical function and improved aesthetic appearance of their scars. The health care providers also found that the treatments improved functional and aesthetic end points. Overall, our study helps substantiate the body of evidence that using CO2 laser therapy improves aesthetics and function of hypertrophic scars in the upper extremity.

Effects of temperature-sensitive hydroxybutyl chitosan hydrogel on wound healing of full-thickness skin defect in rats

Effects of temperature-sensitive hydroxybutyl chitosan hydrogel on wound healing of full-thickness skin defect in rats

Progressive Microstructural Deterioration Dictates Evolving Biomechanical Dysfunction in the Marfan Aorta.

Medial deterioration leading to thoracic aortic aneurysms arises from multiple causes, chief among them mutations to the gene that encodes fibrillin-1 and leads to Marfan syndrome. Fibrillin-1 microfibrils associate with elastin to form elastic fibers, which are essential structural, functional, and instructional components of the normal aortic wall. Compromised elastic fibers adversely impact overall structural integrity and alter smooth muscle cell phenotype. Despite significant progress in characterizing clinical, histopathological, and mechanical aspects of fibrillin-1 related aortopathies, a direct correlation between the progression of microstructural defects and the associated mechanical properties that dictate aortic functionality remains wanting. In this paper, age-matched wild-type, Fbn1C1041G/+, and Fbn1mgR/mgR mouse models were selected to represent three stages of increasing severity of the Marfan aortic phenotype. Ex vivo multiphoton imaging and biaxial mechanical testing of the ascending and descending thoracic aorta under physiological loading conditions demonstrated that elastic fiber defects, collagen fiber remodeling, and cell reorganization increase with increasing dilatation. Three-dimensional microstructural characterization further revealed radial patterns of medial degeneration that become more uniform with increasing dilatation while correlating strongly with increased circumferential material stiffness and decreased elastic energy storage, both of which comprise aortic functionality.

Role of the Alarmin S100A9 protein in inducing Achilles tendinopathy in rats.

BackgroundThis study aimed to investigate the correlation between the Alarmin S100A9 protein and Achilles tendinopathy (AT), and to reveal the role of this protein in inducing AT.MethodsIn this study, 40 male Sprague-Dawley rats were randomly divided into four groups: Control group (received no treatment), Injury group (Achilles tendon tissues were cut intraoperatively), S100A9 group (received a subcutaneous injection of rhS100A9 solution), and S100A9 + Paquinimod group [received a subcutaneous injection of rhS100A9 and Paquinimod (1:1 ratio) into the Achilles tendon]. At 1 week postoperatively, the four groups of rats were euthanized, and the Achilles tendon tissues were isolated for histological staining, immunohistochemistry (IHC), immunofluorescence, Sirius Red (SR) staining, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay.ResultsCompared with both the Control and S100A9 + Paquinimod groups, the Injury and S100A9 groups exhibited higher expression levels of S100A9 protein, matrix metalloproteinase-3 (MMP-3), and inflammatory factors. Regarding histomorphology [hematoxylin-eosin (HE) staining and Safranin O/fast green (SOFG; fast green and Safranin) training], the Achilles tendon tissues in the Injury and S100A9 groups showed AT-like changes, and the fibers were extremely disorderly, non-bundled, and ruptured, and some nuclei were spindles. As for collagen (Col) remodeling, a large number of fresh collagen fibers had formed, the amounts of Col-I and Col-II were lower, and a large quantity of Col-III was present. Additionally, a large number of tendon cells had died in both the Injury and S100A9 groups.ConclusionsThis study showed that Alarmin S100A9 can induce AT-like morphological changes and local inflammatory reactions, trigger collagen fiber remodeling and tendon cell apoptosis, and ultimately induce AT.

Development of a Collagen Fibre Remodelling Rupture Risk Metric for Potentially Vulnerable Carotid Artery Atherosclerotic Plaques.

Atherosclerotic plaque rupture in carotid arteries can lead to stroke which is one of the leading causes of death or disability worldwide. The accumulation of atherosclerotic plaque in an artery changes the mechanical properties of the vessel. Whilst healthy arteries can continuously adapt to mechanical loads by remodelling their internal structure, particularly the load-bearing collagen fibres, diseased vessels may have limited remodelling capabilities. In this study, a local stress modulated remodelling algorithm is proposed to explore the mechanical response of arterial tissue to the remodelling of collagen fibres. This stress driven remodelling algorithm is used to predict the optimum distribution of fibres in healthy and diseased human carotid bifurcations obtained using Magnetic Resonance Imaging (MRI). In the models, healthy geometries were segmented into two layers: media and adventitia and diseased into four components: adventitia, media, plaque atheroma and lipid pool (when present in the MRI images). A novel meshing technique for hexahedral meshing of these geometries is also demonstrated. Using the remodelling algorithm, the optimum fibre patterns in various patient specific plaques are identified and the role that deviations from these fibre configurations in plaque vulnerability is shown. This study provides critical insights into the collagen fibre patterns required in carotid artery and plaque tissue to maintain plaque stability.

Decreased levels of endocytic collagen receptor Endo180 in dermal fibroblasts lead to decreased production of type I collagen and increased expression of matrix metalloproteinase‐1

BackgroundEndo180 is involved in collagen remodeling by incorporating extracellular degraded collagen. Ultraviolet irradiation of dermal fibroblasts reduces Endo180 expression, which affects collagen fiber remodeling. However, it is unclear whether the decrease in Endo180 is directly related to the decrease in type I collagen fibers during photoaging. We aimed to clarify the relationship between Endo180 reduction and the decrease in type I collagen fibers observed in photoaged dermis.MethodsEndo180 was reduced in normal human dermal fibroblasts using RNAi. Endo180 knockdown cells were inoculated into collagen gels. The influence of Endo180 knockdown was evaluated by measuring mRNA expression of collagen fiber remodeling‐related factors and collagen gel contraction. The collagen state and oxidative stress in the collagen gels were also measured.ResultsEndo180 knockdown cells, which were confirmed by gelatin uptake inhibition, showed upregulation of matrix metalloproteinase‐1 and downregulation of type I collagen mRNA expression when cultured in collagen gels. The contractility of the collagen gel was reduced by Endo180 knockdown. The collagen state in the extracellular matrix of the collagen gels containing Endo180 knockdown fibroblasts showed increased amounts of 3/4 fragmented collagen and denatured collagen and decreased type I collagen synthesis. In addition, an increase in intracellular oxidative stress was observed.ConclusionsThis study confirmed that the decrease in Endo180 caused a failure in collagen fiber formation and a decrease in collagen production, reproducing the photoaging dermal structural changes. This suggests that the decrease in Endo180 may be involved in wrinkle formation, which is a characteristic of photoaged skin.