Structure, physiology, and biochemistry of collagens

Hybrid lipid nanoparticles derived from human mesenchymal stem cell extracellular vesicles by microfluidic sonication for collagen I mRNA delivery to human tendon progenitor stem cells

Tendon degeneration remains an intricate pathological process characterized by the coexistence of multiple dysregulated homeostasis processes, including the increase in collagen III production in comparison with collagen I. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) remain a promising therapeutic tool thanks to their pro-regenerative properties and applicability as drug delivery systems, despite their drug loading limitations. Herein, we developed MSC-EV-derived hybrid lipid nanoparticles (MSC-Hyb NPs) using a microfluidic-sonication technique as an alternative platform for the delivery of collagen type I (COL 1A1) mRNA into pathological TSPCs. The MSC-Hyb NPs produced had LNP-like physicochemical characteristics and were 178.6 nm in size with a PDI value of 0.245. Moreover, MSC-Hyb NPs encapsulated mRNA and included EV-derived surface proteins such as CD63, CD81 and CD144. MSC-Hyb NPs remained highly biocompatible with TSPCs and proved to be functional mRNA delivery agents with certain limitations in comparison with lipid nanoparticles (LNPs). In vitro efficacy studies on TSPCs showed a 2-fold increase in procollagen type I carboxy-terminal peptide production comparable with the effect caused by LNPs. Therefore, our work provides an alternative production method for MSC-EV-derived hybrid NPs and supports their potential use as drug delivery systems for tendon regeneration.

Injectable Endoplasmin-Loaded Lipid Nanoparticles-Hydrogel Composite for Cartilage Regeneration

BACKGROUND

Endoplasmin (ENPL), a heat shock protein 90 family member, promotes chondrogenic differentiation of stem cells by inhibiting ERK1/2 phosphorylation and inducing endoplasmic reticulum stress. However, its large size limits cellular uptake and therapeutic potential. To overcome this challenge, a cationic lipid nanoparticle (C_LNP) system was designed to deliver ENPL intracellularly, enhancing its effects on human tonsil-derived mesenchymal stem cells (hTMSCs).

METHODS

ENPL-loaded cationic lipid nanoparticles (ENPL_C_LNP) were synthesized to facilitate intracellular ENPL delivery. The delivery efficiency and cytotoxicity were assessed in vitro using hTMSCs. Additionally, ENPL_C_LNPs were incorporated into a hyaluronic acid and chondroitin sulfate-based injectable hydrogel and tested for chondrogenic differentiation potential in a mouse subcutaneous model.

RESULTS

ENPL_C_LNP achieved over 80% intracellular protein delivery efficiency with no cytotoxic effects. Co-cultured hTMSCs exhibited increased glycosaminoglycans (GAGs) and collagen expression over 21 days. In vivo, the hydrogel-embedded ENPL_C_LNP system enabled stable cartilage differentiation, evidenced by abundant cartilage-specific lacuna structures in regenerated tissue.

CONCLUSION

Combining ENPL_C_LNP with an injectable hydrogel scaffold supports chondrogenic differentiation and cartilage regeneration, offering a promising strategy for cartilage tissue engineering.

Research Progress on Biomaterials for Spinal Cord Repair

Spinal cord injury (SCI) is a very destructive disease of the central nervous system that often causes irreversible nerve damage. Unfortunately, the adult mammalian spinal cord displays little regenerative capacity after injury. In addition, the glial scars and inflammatory responses around the lesion site are another major obstacle for successful axon regeneration after SCI. However, biomaterials are highly biocompatible, and they could provide physical guidance to allow regenerating axon growth over the lesion site and restore functional neural circuits. In addition, combined or synergistic effects of spinal cord repair can be achieved by integrating different strategies, including the use of various biomaterials and microstructures, as well as combining bioactive molecules and living cells. Therefore, it is possible to use tissue engineering scaffolds to regulate the local microenvironment of the injured spinal cord, which may achieve better functional recovery in spinal cord injury repair. In this review, we summarize the latest progress in the treatment of SCI by biomaterials, and discussed its potential mechanism.

Regulation of Joint Tissues and Joint Function: Is There Potential for Lessons to Be Learned Regarding Regulatory Control from Joint Hypermobility Syndromes?

Normal development of joints starts in utero with the establishment of a cellular and extracellular matrix template. Following birth, individual joint tissues grow and mature in response to biochemical and mechanical signals, leading to a coordinated pattern of further maturation resulting in a joint that functions as an organ system. Each joint develops and matures as an organ system defined by the biomechanical environment in which it will function. For those with joint hypermobility syndromes, either defined by specific genetic mutations or not (i.e., Ehlers-Danlos syndrome, Marfan syndrome, Loey-Dietz syndrome, hypermobility-type Ehlers-Danlos syndrome), this process is partially compromised, but many aspects of joint tissue maturation and resulting joint function is retained such that the organs form and retain partial function, but it is compromised. Comparing the characteristics of what is known regarding development, growth, maturation, and response to stressors such as puberty, pregnancy, and aging in joints of those without and with joint hypermobility leads to the conclusion that in those that have hypermobility syndromes, the joint systems may be compromised via a failure to undergo mechanical maturation, possibly via defective mechanotransduction. Given the breadth of the mutations involved in such hypermobility syndromes, further characterization of this concept may reveal commonalities in their impact on tissue maturation, which will further inform regulatory aspects of normal tissue and functional integrity. This review/perspective piece will attempt to detail such comparisons and summarize how further study will aid in further understanding.

Regulatory Role of Collagen XI in the Establishment of Mechanical Properties of Tendons and Ligaments in Mice Is Tissue Dependent

Collagen XI is ubiquitous in tissues such as joint cartilage, cancellous bone, muscles, and tendons and is an important contributor during a crucial part in fibrillogenesis. The COL11A1 gene encodes one of three alpha chains of collagen XI. The present study elucidates the role of collagen XI in the establishment of mechanical properties of tendons and ligaments. We investigated the mechanical response of three tendons and one ligament tissues from wild type and a targeted mouse model null for collagen XI: Achilles tendon (ACH), the flexor digitorum longus tendon (FDL), the supraspinatus tendon (SST), and the anterior cruciate ligament (ACL). Area was substantially lower in Col11a1ΔTen/ΔTen ACH, FDL, and SST. Maximum load and maximum stress were significantly lower in Col11a1ΔTen/ΔTen ACH and FDL. Stiffness was lower in Col11a1ΔTen/ΔTen ACH, FDL, and SST. Modulus was reduced in Col11a1ΔTen/ΔTen FDL and SST (both insertion site and midsubstance). Collagen fiber distributions were more aligned under load in both wild type group and Col11a1ΔTen/ΔTen groups. Results also revealed that the effect of collagen XI knockout on collagen fiber realignment is tendon-dependent and location-dependent (insertion versus midsubstance). In summary, this study clearly shows that the regulatory role of collagen XI on tendon and ligament is tissue specific and that joint hypermobility in type II Stickler's Syndrome may in part be due to suboptimal mechanical response of the soft tissues surrounding joints.

The current status of various preclinical therapeutic approaches for tendon repair

Tendons are fibroblastic structures that link muscle and bone. There are two kinds of tendon injuries, including acute and chronic. Each form of injury or deterioration can result in significant pain and loss of tendon function. The recovery of tendon damage is a complex and time-consuming recovery process. Depending on the anatomical location of the tendon tissue, the clinical outcomes are not the same. The healing of the wound process is divided into three stages that overlap: inflammation, proliferation, and tissue remodeling. Furthermore, the curing tendon has a high re-tear rate. Faced with the challenges, tendon injury management is still a clinical issue that must be resolved as soon as possible. Several newer directions and breakthroughs in tendon recovery have emerged in recent years. This article describes tendon injury and summarizes recent advances in tendon recovery, along with stem cell therapy, gene therapy, Platelet-rich plasma remedy, growth factors, drug treatment, and tissue engineering. Despite the recent fast-growing research in tendon recovery treatment, still, none of them translated to the clinical setting. This review provides a detailed overview of tendon injuries and potential preclinical approaches for treating tendon injuries.

Tendon-targeted knockout of collagen XI disrupts patellar and Achilles tendon structure and mechanical properties during murine postnatal development

BACKGROUND

Collagen XI is a fibril-forming collagen typically associated with type II collagen tissues but is also expressed in type I collagen-rich tendons, especially during development. We previously showed that tendon-targeted (Scx-Cre) Col11a1 knockout mice have smaller tendons in adulthood with aberrant fibril structure and impaired mechanical properties. However, the manifestation of this phenotype is not clearly understood. Therefore, our objective is to define the spatiotemporal roles of collagen XI in tendon structure-function during postnatal development. Given the high expression of collagen XI during embryonic development, we hypothesized that collagen XI knockout leads to the deposition of weakened extracellular matrix during early postnatal timepoints, disrupting the establishment of tendon structure and function.

METHODS

Patellar and Achilles tendons from postnatal (P) days 0, 10, 20, and 30 tendon-targeted scleraxis-Cre heterozygous and homozygous Col11a1 knockout mice were evaluated for morphology, nuclear organization, fibril morphology, mechanical properties, and gene expression.

RESULTS

At P0, there were no differences in tendon length or fibril diameter of either tendon. By P10, striking structural and functional differences emerged, with collagen XI deficiency resulting in increased tendon length, a heterogeneous and larger diameter population of fibrils, and inferior mechanical properties in both patellar and Achilles tendons. Differences increased in magnitude through P30, supporting our hypothesis that impaired structure-function during postnatal development may drive tendon lengthening and reduced mechanical properties.

CONCLUSIONS

Though collagen XI is a quantitatively minor component of the tendon extracellular matrix, these results highlight the critical role of collagen XI in the acquisition of tendon structure-function.

The Role of Mast Cells in the Remodeling Effects of Molecular Hydrogen on the Lung Local Tissue Microenvironment under Simulated Pulmonary Hypertension

Molecular hydrogen (H2) has antioxidant, anti-inflammatory, and anti-fibrotic effects. In a rat model simulating pulmonary fibrotic changes induced by monocrotaline-induced pulmonary hypertension (MPH), we had previously explored the impact of inhaled H2 on lung inflammation and blood pressure. In this study, we further focused the biological effects of H2 on mast cells (MCs) and the parameters of the fibrotic phenotype of the local tissue microenvironment. MPH resulted in a significantly increased number of MCs in both the pneumatic and respiratory parts of the lungs, an increased number of tryptase-positive MCs with increased expression of TGF-β, activated interaction with immunocompetent cells (macrophages and plasma cells) and fibroblasts, and increased MC colocalization with a fibrous component of the extracellular matrix of connective tissue. The alteration in the properties of the MC population occurred together with intensified collagen fibrillogenesis and an increase in the integral volume of collagen and elastic fibers of the extracellular matrix of the pulmonary connective tissue. The exposure of H2 together with monocrotaline (MCT), despite individual differences between animals, tended to decrease the intrapulmonary MC population and the severity of the fibrotic phenotype of the local tissue microenvironment compared to changes in animals exposed to the MCT effect alone. In addition, the activity of collagen fibrillogenesis associated with MCs and the expression of TGF-β and tryptase in MCs decreased, accompanied by a reduction in the absolute and relative content of reticular and elastic fibers in the lung stroma. Thus, with MCT exposure, inhaled H2 has antifibrotic effects involving MCs in the lungs of rats. This reveals the unknown development mechanisms of the biological effects of H2 on the remodeling features of the extracellular matrix under inflammatory background conditions of the tissue microenvironment.

State-of-the-Art in Skin Fluorescent Photography for Cosmetic and Skincare Research: From Molecular Spectra to AI Image Analysis

Autofluorescence is a remarkable property of human skin. It can be excited by UV and observed in the dark using special detection systems. The method of fluorescence photography (FP) is an effective non-invasive tool for skin assessment. It involves image capturing by a camera the emission of light quanta from fluorophore molecules in the skin. It serves as a useful tool for cosmetic and skincare research, especially for the detection of pathological skin states, like acne, psoriasis, etc. To the best of our knowledge, there is currently no comprehensive review that fully describes the application and physical principles of FP over the past five years. The current review covers various aspects of the skin FP method from its biophysical basis and the main fluorescent molecules of the skin to its potential applications and the principles of FP recording and analysis. We pay particular attention to recently reported works on the automatic analysis of FP based on artificial intelligence (AI). Thus, we argue that FP is a rapidly evolving technology with a wide range of potential applications. We propose potential directions of the development of this method, including new AI algorithms for the analysis and expanding the range of applications.

Collagen as the extracellular matrix biomaterials in the arena of medical sciences

Collagen is a multipurpose material that has several applications in the health care, dental care, and pharmaceutical industries. Crosslinked compacted solids or lattice-like gels can be made from collagen. Biocompatibility, biodegradability, and wound-healing properties make collagen a popular scaffold material for cardiovascular, dentistry, and bone tissue engineering. Due to its essential role in the control of several of these processes, collagen has been employed as a wound-healing adjunct. It forms a major component of the extracellular matrix and regulates wound healing in its fibrillar or soluble forms. Collagen supports cardiovascular and other soft tissues. Oral wounds have been dressed with resorbable forms of collagen for closure of graft and extraction sites, and to aid healing. This present review is concentrated on the use of collagen in bone regeneration, wound healing, cardiovascular tissue engineering, and dentistry.

A transcriptomic analysis of incisional hernia based on high-throughput sequencing technology

PURPOSE

Incisional hernia is a common postoperative complication; however, few transcriptomic studies have been conducted on it. In this study, we used second-generation high-throughput sequencing to explore the pathogenesis and potential therapeutic targets of incisional hernias.

METHODS

Superficial fasciae were collected from 15 patients without hernia and 21 patients with an incisional hernia. High-throughput sequencing of the fascia was performed to generate an expression matrix. We analyzed the matrix to identify differentially expressed genes (DEGs) and performed gene ontology and enrichment analyses of these DEGs. Additionally, an external dataset was utilized to identify key DEGs.

RESULTS

We identified 1,823 DEGs closely associated with extracellular matrix (ECM) imbalance, bacterial inflammatory response, and fibrillar collagen trimerization. TNNT3, CMAY5, ATP1B4, ASB5, CILP, SIX4, FBN1 and FNDC5 were identified as key DEGs at the intersection of the two expression matrices. Moreover, non-alcoholic fatty liver disease-related, TNF, and IL-17 signaling pathways were identified as key enrichment pathways.

CONCLUSIONS

We identified eight key DEGs and three pathways associated with incisional hernias. Our findings offer new insights into the pathogenesis of incisional hernias and highlight potential targets for their prevention and treatment.

Tertiary lymphoid structures: new immunotherapy biomarker

Immunotherapy shows substantial advancement in cancer and is becoming widely used in clinical practice. A variety of biomarkers have been proposed to predict the efficacy of immunotherapy, but most of them have low predictive ability. Tertiary lymphoid structures (TLSs), the aggregation of multiple lymphocytes, have been found to exist in various tumor tissues. TLSs have been shown to correlate with patient prognosis and immunotherapy response. This review summarizes the characteristics of TLSs and the inducing factors of TLS formation, presents available evidence on the role of TLSs in predicting immunotherapy response in different cancers, and lastly emphasizes their predictive potential for neoadjuvant immunotherapy efficacy.

Accurately deciphering spatial domains for spatially resolved transcriptomics with stCluster

Spatial transcriptomics provides valuable insights into gene expression within the native tissue context, effectively merging molecular data with spatial information to uncover intricate cellular relationships and tissue organizations. In this context, deciphering cellular spatial domains becomes essential for revealing complex cellular dynamics and tissue structures. However, current methods encounter challenges in seamlessly integrating gene expression data with spatial information, resulting in less informative representations of spots and suboptimal accuracy in spatial domain identification. We introduce stCluster, a novel method that integrates graph contrastive learning with multi-task learning to refine informative representations for spatial transcriptomic data, consequently improving spatial domain identification. stCluster first leverages graph contrastive learning technology to obtain discriminative representations capable of recognizing spatially coherent patterns. Through jointly optimizing multiple tasks, stCluster further fine-tunes the representations to be able to capture complex relationships between gene expression and spatial organization. Benchmarked against six state-of-the-art methods, the experimental results reveal its proficiency in accurately identifying complex spatial domains across various datasets and platforms, spanning tissue, organ, and embryo levels. Moreover, stCluster can effectively denoise the spatial gene expression patterns and enhance the spatial trajectory inference. The source code of stCluster is freely available at https://github.com/hannshu/stCluster.

Microstructural, Micromechanical Atlas of the Temporomandibular Joint Disc

The temporomandibular joint (TMJ) disc is mainly composed of collagen, with its arrangement responding to efficient stress distribution. However, microstructural and micromechanical transformations of the TMJ disc under resting, functional, and pathological conditions remain unclear. To address this, our study presents a high-resolution microstructural and mechanical atlas of the porcine TMJ disc. First, the naive microstructure and mechanical properties were investigated in porcine TMJ discs (resting and functional conditions). Subsequently, the perforation and tear models (pathological conditions) were compared. Following this, a rabbit model of anterior disc displacement (abnormal stress) was studied. Results show diverse microstructures and mechanical properties at the nanometer to micrometer scale. In the functional state, gradual unfolding of the crimping cycle in secondary and tertiary structures leads to D-cycle prolongation in the primary structure, causing tissue failure. Pathological conditions lead to stress concentration near the injury site due to collagen interfibrillar traffic patterns, resulting in earlier damage manifestation. Additionally, the abnormal stress model shows collagen damage initiating at the primary structure and extending to the superstructure over time. These findings highlight collagen's various roles in different pathophysiological states. Our study offers valuable insights into TMJ disc function and dysfunction, aiding the development of diagnostic and therapeutic strategies for TMJ disorders, as well as providing guidance for the design of structural biomimetic materials.

Glycosylation Modulates the Structure and Functions of Collagen: A Review

Collagens are fundamental constituents of the extracellular matrix and are the most abundant proteins in mammals. Collagens belong to the family of fibrous or fiber-forming proteins that self-assemble into fibrils that define their mechanical properties and biological functions. Up to now, 28 members of the collagen superfamily have been recognized. Collagen biosynthesis occurs in the endoplasmic reticulum, where specific post-translational modification-glycosylation-is also carried out. The glycosylation of collagens is very specific and adds β-d-galactopyranose and β-d-Glcp-(1→2)-d-Galp disaccharide through β-O-linkage to hydroxylysine. Several glycosyltransferases, namely COLGALT1, COLGALT2, LH3, and PGGHG glucosidase, were associated the with glycosylation of collagens, and recently, the crystal structure of LH3 has been solved. Although not fully understood, it is clear that the glycosylation of collagens influences collagen secretion and the alignment of collagen fibrils. A growing body of evidence also associates the glycosylation of collagen with its functions and various human diseases. Recent progress in understanding collagen glycosylation allows for the exploitation of its therapeutic potential and the discovery of new agents. This review will discuss the relevant contributions to understanding the glycosylation of collagens. Then, glycosyltransferases involved in collagen glycosylation, their structure, and catalytic mechanism will be surveyed. Furthermore, the involvement of glycosylation in collagen functions and collagen glycosylation-related diseases will be discussed.

HTRA1-driven detachment of type I collagen from endoplasmic reticulum contributes to myocardial fibrosis in dilated cardiomyopathy

BACKGROUND

The aberrant secretion and excessive deposition of type I collagen (Col1) are important factors in the pathogenesis of myocardial fibrosis in dilated cardiomyopathy (DCM). However, the precise molecular mechanisms underlying the synthesis and secretion of Col1 remain unclear.

METHODS AND RESULTS

RNA-sequencing analysis revealed an increased HtrA serine peptidase 1 (HTRA1) expression in patients with DCM, which is strongly correlated with myocardial fibrosis. Consistent findings were observed in both human and mouse tissues by immunoblotting, quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunohistochemistry, and immunofluorescence analyses. Pearson's analysis showed a markedly positive correlation between HTRA1 level and myocardial fibrosis indicators, including extracellular volume fraction (ECV), native T1, and late gadolinium enhancement (LGE), in patients with DCM. In vitro experiments showed that the suppression of HTRA1 inhibited the conversion of cardiac fibroblasts into myofibroblasts and decreased Col1 secretion. Further investigations identified the role of HTRA1 in promoting the formation of endoplasmic reticulum (ER) exit sites, which facilitated the transportation of Col1 from the ER to the Golgi apparatus, thereby increasing its secretion. Conversely, HTRA1 knockdown impeded the retention of Col1 in the ER, triggering ER stress and subsequent induction of ER autophagy to degrade misfolded Col1 and maintain ER homeostasis. In vivo experiments using adeno-associated virus-serotype 9-shHTRA1-green fluorescent protein (AAV9-shHTRA1-GFP) showed that HTRA1 knockdown effectively suppressed myocardial fibrosis and improved left ventricular function in mice with DCM.

CONCLUSIONS

The findings of this study provide valuable insights regarding the treatment of DCM-associated myocardial fibrosis and highlight the therapeutic potential of targeting HTRA1-mediated collagen secretion.

Pathogenesis and Diagnosis of Proximal Hamstring Tendinopathies

The proximal hamstring complex is a highly vulnerable area that is especially prone to injury. Proximal hamstring tendinopathies (PHTs) remain challenging in diagnosis, treatment, rehabilitation, and prevention due to a large variety of different injuries, slow healing response, persistent symptoms, and functional impairments. PHTs are often misdiagnosed or underdiagnosed, leading to delayed treatment and therapy failure. In addition, many athletes are at a high risk of PHT recurrence, a leading cause of prolonged rehabilitation and impaired individual performance. Until now, there have been no clear criteria for the diagnosis and classification of PHT. Tendinopathies can be graded based on their symptoms and onset. Additionally, radiological characteristics exist that describe the severity of tendinopathies. The diagnosis usually includes a battery of pain provocation tests, functional tests, and imaging to ensure a proper classification. Understanding the specific tasks in the pathogenesis and diagnostic process of PHT requires knowledge of functional anatomy, injury pattern and pathophysiological mechanisms as well as examination and imaging techniques. This work provides a structured overview of the pathogenesis and diagnostic work-up of PHT, emphasizing structured examination and imaging to enable a reliable diagnosis and rapid treatment decisions.

Collagen and gelatin: Structure, properties, and applications in food industry

Food-producing animals have the highest concentration of collagen in their extracellular matrix. Collagen and gelatin are widely used in food industry due to their specific structural, physicochemical, and biochemical properties, which enable them to improve health and nutritional value as well as to increase the stability, consistency, and elasticity of food products. This paper reviews the structural and functional properties including inherent self-assembly, gel forming, water-retaining, emulsifying, foaming, and thickening properties of collagen and gelatin. Then the colloid structures formed by collagen such as emulsions, films or coatings, and fibers are summarized. Finally, the potential applications of collagen and gelatin in muscle foods, dairy products, confectionary and dessert, and beverage products are also reviewed. The objective of this review is to provide the current market value, progress as well as applications of collagen and its derivatives in food industry.

COL28 promotes proliferation, migration, and EMT of renal tubular epithelial cells

Type XXVIII collagen (COL28) is involved in cancer and lung fibrosis. COL28 polymorphisms and mutations might be involved in kidney fibrosis, but the exact role of COL28 in renal fibrosis is unknown. This study explored the function of COL28 in renal tubular cells by examining the expression of COL28 mRNA and the effects of COL28 overexpression in human tubular cells. COL28 mRNA expression and localization were observed in normal and fibrotic kidney tissues from humans and mice using real-time PCR, western blot, immunofluorescence, and immunohistochemistry. The consequences of COL28 overexpression on cell proliferation, migration, cell polarity, and epithelial-to-mesenchymal transition (EMT) induced by TGF-β1 were examined in human tubular HK-2 cells. COL28 expression was low in human normal renal tissues, mainly observed in the renal tubular epithelial cells and especially in proximal renal tubules. COL28 protein expression in human and mouse obstructive kidney disease was higher than in normal tissues (p < 0.05) and more significant in the UUO2-Week than the UUO1-Week group. The overexpression of COL28 promoted HK-2 cell proliferation and enhanced their migration ability (all p < 0.05). TGF-β1 (10 ng/ml) induced COL28 mRNA expression in HK-2 cells, decreased E-cadherin and increased α-SMA in the COL28-overexpression group compared with controls (p < 0.05). ZO-1 expression decreased while COL6 increased in the COL28-overexpression group compared with controls (p < 0.05). In conclusion, COL28 overexpression promotes the migration and proliferation of renal tubular epithelial cells. The EMT could also be involved. COL28 could be a therapeutic target against renal- fibrotic diseases.

The growth status and functions of olfactory ensheathing cells cultured on randomly oriented and aligned type-I-collagen-based nanofibrous scaffolds

Aim. The potential of olfactory ensheathing cells (OECs) as a cell therapy for spinal cord reconstruction and regeneration after injury has drawn significant attention in recent years. This study attempted to investigate the influences of nano-fibrous scaffolds on the growth status and functional properties of OECs.Methods.The ultra-morphology of the scaffolds was visualized using scanning electron microscopy (SEM). To culture OECs, donated cells were subcultured and identified with p75. Cell proliferation, apoptosis, and survival rates were measured through MTT assay, Annexin-V/PI staining, and p75 cell counting, respectively. The adhesion of cells cultured on scaffolds was observed using SEM. Additionally, the functions of OECs cultured on scaffolds were assessed by testing gene expression levels through real time polymerase chain reaction.Results.The electrospun type I collagen-based nano-fibers exhibited a smooth surface and uniform distribution. It was indicated that the proliferation and survival rates of OECs cultured on both randomly oriented and aligned type I collagen-based nano-fibrous scaffolds were higher than those observed in the collagen-coated control. Conversely, apoptosis rates were lower in cells cultured on scaffolds. Furthermore, OEC adhesion was better on the scaffolds than on the control. The expression levels of target genes were significantly elevated in cells cultured on scaffolds versus the controls.Conclusion.As a whole, the utilization of aligned collagen nanofibers has demonstrated significant advantages in promoting cell growth and improving cell function. These findings have important implications for the field of regenerative medicine and suggest that the approach may hold promise for the future therapeutic applications.

Hyperprolactinemia modifies extracellular matrix components associated with collagen fibrillogenesis in harderian glands of non- and pregnant female mice

The harderian gland (HG) is a gland located at the base of the nictating membrane and fills the inferomedial aspect of the orbit in rodents. It is under the influence of the hypothalamic-pituitary-gonadal axis and, because of its hormone receptors, it is a target tissue for prolactin (PRL) and sex steroid hormones (estrogen and progesterone). In humans and murine, the anterior surface of the eyes is protected by a tear film synthesized by glands associated with the eye. In order to understand the endocrine changes caused by hyperprolactinemia in the glands responsible for the formation of the tear film, we used an animal model with metoclopramide-induced hyperprolactinemia (HPRL). Given the evidences that HPRL can lead to a process of cell death and tissue fibrosis, the protein expression of small leucine-rich proteoglycans (SLRPs) was analyzed through immunohistochemistry in the HG of the non- and the pregnant female mice with hyperprolactinemia. The SRLPs are related to collagen fibrillogenesis and they participate in pro-apoptotic signals. Our data revealed that high prolactin levels and changes in steroid hormones (estrogen and progesterone) can lead to an alteration in the amount of collagen, and in the structure of type I and III collagen fibers through changes in the amounts of lumican and decorin, which are responsible for collagen fibrillogenesis. This fact can lead to the impaired functioning of the HG by excessive apoptosis in the HG of the non- and the pregnant female mice with HPRL and especially in the HG of pregnancy-associated hyperprolactinemia.

Angiotensin-I-Converting Enzyme (ACE)-Inhibitory Peptides from the Collagens of Monkfish (Lophius litulon) Swim Bladders: Isolation, Characterization, Molecular Docking Analysis and Activity Evaluation

The objective of this study was to isolate and characterize collagen and angiotensin-I-converting enzyme (ACE)-inhibitory (ACEi) peptides from the swim bladders of monkfish (Lophius litulon). Therefore, acid-soluble collagen (ASC-M) and pepsin-soluble collagen (PSC-M) with yields of 4.27 ± 0.22% and 9.54 ± 0.51%, respectively, were extracted from monkfish swim bladders using acid and enzyme methods. The ASC-M and PSC-M contained Gly (325.2 and 314.9 residues/1000 residues, respectively) as the major amino acid, but they had low imino acid content (192.5 and 188.6 residues/1000 residues, respectively) in comparison with collagen from calf skins (CSC) (216.6 residues/1000 residues). The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns and ultraviolet (UV) absorption spectrums of ASC-M and PSC-M illustrated that they were mainly composed of type I collagen. Subsequently, three ACEi peptides were isolated from a PSC-M hydrolysate prepared via a double-enzyme system (alcalase + neutrase) and identified as SEGPK (MHP6), FDGPY (MHP7) and SPGPW (MHP9), with molecular weights of 516.5, 597.6 and 542.6 Da, respectively. SEGPK, FDGPY and SPGPW displayed remarkable anti-ACE activity, with IC50 values of 0.63, 0.94 and 0.71 mg/mL, respectively. Additionally, a molecular docking assay demonstrated that the affinities of SEGPK, FDGPY and SPGPW with ACE were -7.3, -10.9 and -9.4 kcal/mol, respectively. The remarkable ACEi activity of SEGPK, FDGPY and SPGPW was due to their connection with the active pockets and/or sites of ACE via hydrogen bonding, hydrophobic interaction and electrostatic force. Moreover, SEGPK, FDGPY and SPGPW could protect HUVECs by controlling levels of nitric oxide (NO) and endothelin-1 (ET-1). Therefore, this work provides an effective means for the preparation of collagens and novel ACEi peptides from monkfish swim bladders, and the prepared ACEi peptides, including SEGPK, FDGPY and SPGPW, could serve as natural functional components in the development of health care products to control hypertension.

Targeting collagen homeostasis for the treatment of liver fibrosis: Opportunities and challenges

Liver fibrosis is an excessive production, aberrant deposition, and deficit degradation of extracellular matrix (ECM). Patients with unresolved fibrosis ultimately undergo end-stage liver diseases. To date, the effective and safe strategy to cease fibrosis progression remains an unmet clinical need. Since collagens are the most abundant ECM protein which play an essential role in fibrogenesis, the suitable regulation of collagen homeostasis could be an effective strategy for the treatment of liver fibrosis. Therefore, this review provides a brief overview on the dysregulation of ECM homeostasis, focusing on collagens, in the pathogenesis of liver fibrosis. Most importantly, promising therapeutic mechanisms related to biosynthesis, deposition and extracellular interactions, and degradation of collagens, together with preclinical and clinical antifibrotic evidence of drugs affecting each target are orderly criticized. In addition, challenges for targeting collagen homeostasis in the treatment of liver fibrosis are discussed.

Evaluation of IR and Raman spectroscopic markers of human collagens: Insides for indicating colorectal carcinogenesis

Vibrational spectroscopic methods are widely used in the molecular diagnostics of carcinogenesis. Collagen, a component of connective tissue, plays a special role as a biochemical marker of pathological changes in tissues. The vibrational bands of collagens are very promising to distinguish between normal colon tissue, benign and malignant colon polyps. Differences in these bands indicate changes in the amount, structure, conformation and the ratio between the individual structural forms (subtypes) of this protein. The screening of specific collagen markers of colorectal carcinogenesis was carried out based on the FTIR and Raman (λ_ex 785 nm) spectra of colon tissue samples and purified human collagens. It was found that individual types of human collagens showed significant differences in their vibrational spectra, and specific spectral markers were found for them. These collagen bands were assigned to specific vibrations in the polypeptide backbone, amino acid side chains and carbohydrate moieties. The corresponding spectral regions for colon tissues and colon polyps were investigated for the contribution of collagen vibrations. Mentioned spectral differences in collagen spectroscopic markers could be of interest for early ex vivo diagnosis of colorectal carcinoma if combine vibrational spectroscopy and colonoscopy.

Cartilage-Related Collagens in Osteoarthritis and Rheumatoid Arthritis: From Pathogenesis to Therapeutics

Collagens serve essential mechanical functions throughout the body, particularly in the connective tissues. In articular cartilage, collagens provide most of the biomechanical properties of the extracellular matrix essential for its function. Collagen plays a very important role in maintaining the mechanical properties of articular cartilage and the stability of the ECM. Noteworthily, many pathogenic factors in the course of osteoarthritis and rheumatoid arthritis, such as mechanical injury, inflammation, and senescence, are involved in the irreversible degradation of collagen, leading to the progressive destruction of cartilage. The degradation of collagen can generate new biochemical markers with the ability to monitor disease progression and facilitate drug development. In addition, collagen can also be used as a biomaterial with excellent properties such as low immunogenicity, biodegradability, biocompatibility, and hydrophilicity. This review not only provides a systematic description of collagen and analyzes the structural characteristics of articular cartilage and the mechanisms of cartilage damage in disease states but also provides a detailed characterization of the biomarkers of collagen production and the role of collagen in cartilage repair, providing ideas and techniques for clinical diagnosis and treatment.

Collagen for neural tissue engineering: Materials, strategies, and challenges

Neural tissue engineering (NTE) has made remarkable strides in recent years and holds great promise for treating several devastating neurological disorders. Selecting optimal scaffolding material is crucial for NET design strategies that enable neural and non-neural cell differentiation and axonal growth. Collagen is extensively employed in NTE applications due to the inherent resistance of the nervous system against regeneration, functionalized with neurotrophic factors, antagonists of neural growth inhibitors, and other neural growth-promoting agents. Recent advancements in integrating collagen with manufacturing strategies, such as scaffolding, electrospinning, and 3D bioprinting, provide localized trophic support, guide cell alignment, and protect neural cells from immune activity. This review categorises and analyses collagen-based processing techniques investigated for neural-specific applications, highlighting their strengths and weaknesses in repair, regeneration, and recovery. We also evaluate the potential prospects and challenges of using collagen-based biomaterials in NTE. Overall, this review offers a comprehensive and systematic framework for the rational evaluation and applications of collagen in NTE.

Modeling Human Muscular Dystrophies in Zebrafish: Mutant Lines, Transgenic Fluorescent Biosensors, and Phenotyping Assays

Muscular dystrophies (MDs) are a heterogeneous group of myopathies characterized by progressive muscle weakness leading to death from heart or respiratory failure. MDs are caused by mutations in genes involved in both the development and organization of muscle fibers. Several animal models harboring mutations in MD-associated genes have been developed so far. Together with rodents, the zebrafish is one of the most popular animal models used to reproduce MDs because of the high level of sequence homology with the human genome and its genetic manipulability. This review describes the most important zebrafish mutant models of MD and the most advanced tools used to generate and characterize all these valuable transgenic lines. Zebrafish models of MDs have been generated by introducing mutations to muscle-specific genes with different genetic techniques, such as (i) N-ethyl-N-nitrosourea (ENU) treatment, (ii) the injection of specific morpholino, (iii) tol2-based transgenesis, (iv) TALEN, (v) and CRISPR/Cas9 technology. All these models are extensively used either to study muscle development and function or understand the pathogenetic mechanisms of MDs. Several tools have also been developed to characterize these zebrafish models by checking (i) motor behavior, (ii) muscle fiber structure, (iii) oxidative stress, and (iv) mitochondrial function and dynamics. Further, living biosensor models, based on the expression of fluorescent reporter proteins under the control of muscle-specific promoters or responsive elements, have been revealed to be powerful tools to follow molecular dynamics at the level of a single muscle fiber. Thus, zebrafish models of MDs can also be a powerful tool to search for new drugs or gene therapies able to block or slow down disease progression.

Probing the effects of matrix-derived microcarrier composition on human adipose-derived stromal cells cultured dynamically within spinner flask bioreactors

Recognizing the cell-instructive capacity of the extracellular matrix (ECM), this study investigated the effects of expanding human adipose-derived stromal cells (hASCs) on ECM-derived microcarriers fabricated from decellularized adipose tissue (DAT) or decellularized cartilage tissue (DCT) within spinner flask bioreactors. Protocols were established for decellularizing porcine auricular cartilage and electrospraying methods were used to generate microcarriers comprised exclusively of DAT or DCT, which were compositionally distinct, but had matching Young's moduli. Both microcarrier types supported hASC attachment and growth over 14 days within a low-shear spinner culture system, with a significantly higher cell density observed on the DCT microcarriers at 7 and 14 days. Irrespective of the ECM source, dynamic culture on the microcarriers altered the expression of genes and proteins associated with cell adhesion and ECM remodeling. Label-free mass spectrometry analysis showed upregulation of proteins associated with cartilage development and ECM in the hASCs expanded on the DCT microcarriers. Based on Luminex analysis, the hASCs expanded on the DCT microcarriers secreted significantly higher levels of IL-8 and PDGFAA, supporting that the ECM source can modulate hASC paracrine factor secretion. Finally, the hASCs expanded on the microcarriers were extracted for analysis of adipogenic and chondrogenic differentiation relative to baseline controls. The microcarrier-cultured hASCs showed enhanced intracellular lipid accumulation at 7 days post-induction of adipogenic differentiation. In the chondrogenic studies, a low level of differentiation was observed in all groups. Future studies are warranted using alternative cell sources with greater chondrogenic potential to further assess the chondro-inductive properties of the DCT microcarriers.

A micronutrient mixture with collagen peptides, probiotics, cannabidiol, and diet may reduce aging, and development and progression of age-related alzheimer's disease, and improve its treatment

Human aging involves gradual decline in organ functions leading to organ specific age-related chronic diseases such as Alzheimer's disease (AD). Although advances in the development of new drugs, novel surgical procedures, improved diet and lifestyle, have resulted in doubling of lifespan of humans, the quality of life in many cases remains poor because of increased incidence of age-related chronic diseases. Using experimental models of accelerated aging, several cellular defects associated with aging and AD have been identified. Some cellular defects due to increased oxidative stress, chronic inflammation, autophagy defects, mitochondrial dysfunction, and imbalances in the composition probiotics in favor of harmful bacteria over beneficial bacteria are common to both aging and AD, while others such as telomere attrition, loss of collagen, elastin, and hyaluronic acid, failure of DNA repair system, and impaired immune function are unique to aging; and some such as increased production of beta-amyloids, hyperphosphorylation of tau protein, and abnormal behaviors are unique to AD. It is suggested that supplementation with a micronutrient mixture, probiotics, collagen peptides, CBD, and modifications in the diet and lifestyle may reduce the aging processes, and the development, progression of AD, and improve the treatments of this disease.

Molecular and Biologic Effects of Platelet-Rich Plasma (PRP) in Ligament and Tendon Healing and Regeneration: A Systematic Review

Platelet-rich plasma (PRP) has been introduced and applied to a wide spectrum of acute and chronic ligament and tendon pathologic conditions. Although the biological effect of PRP has been studied thoroughly in both animal and human studies, there is no consensus so far on the exact mechanism of its action as well as the optimal timing and dosage of its application. Therefore, we conducted a systematic review aiming to evaluate the molecular effect of the administration of PRP in tendoligamentous injuries and degenerative diseases. The literature search revealed 36 in vitro and in vivo studies examining the healing and remodeling response of animal and human ligament or tendon tissues to PRP. Platelet-rich plasma added in the culture media was highly associated with increased cell proliferation, migration, viability and total collagen production of both ligament- and tendon-derived cells in in vitro studies, which was further confirmed by the upregulation of collagen gene expression. In vivo studies correlated the PRP with higher fibroblastic anabolic activity, including increased cellularity, collagen production and vascularity of ligament tissue. Similarly, greater metabolic response of tenocytes along with the acceleration of the healing process in the setting of a tendon tear were noticed after PRP application, particularly between the third and fourth week after treatment. However, some studies demonstrated that PRP had no or even negative effect on tendon and ligament regeneration. This controversy is mainly related to the variable processes and methodologies of preparation of PRP, necessitating standardized protocols for both investigation and ap-plication.

Pomegranate natural extract Pomanox® positively modulates skin health-related parameters in normal and UV-induced photoaging conditions in Hs68 human fibroblast cells

Skin photoaging is primarily caused by ultraviolet radiation and can lead to the degradation of skin extracellular matrix components, resulting in hyperpigmentation and skin elasticity loss. In this area, polyphenols have become of great interest because of their antioxidant, anti-inflammatory and antiaging properties. Here, we evaluated the effects of the pomegranate natural extract Pomanox^® on skin health-related parameters in normal and UV-induced photoaging conditions in human fibroblast Hs68 cells. Moreover, the inhibitory effects of Pomanox^® on tyrosinase activity were assessed. In normal conditions, Pomanox^® significantly modulated collagen and hyaluronic acid metabolisms. In UV-exposed cells, both preventive and regenerative treatments with Pomanox^® positively modulated hyaluronic acid metabolism and decreased ROS levels. However, only the preventive treatment modulated collagen metabolism. Finally, Pomanox^® showed a marked inhibitory capacity of tyrosinase activity (IC50 = 394.7 μg/mL). The modulation of skin health-related parameters exhibited by Pomanox^® open a wide range of potential applications of this product.

Levels of extracellular matrix metabolites are associated with changes in Ankylosing Spondylitis Disease Activity Score and MRI inflammation scores in patients with axial spondyloarthritis during TNF inhibitor therapy

BACKGROUND/PURPOSE

In axial spondyloarthritis (axSpA) inflammation of the sacroiliac joints and spine is associated with local extracellular matrix (ECM) remodeling of affected tissues. We aimed to investigate the association of ECM metabolites with treatment response in axSpA patients treated with TNF-α inhibitory therapy for 46 weeks.

METHODS

In a prospective clinical study of axSpA patients (n=55) initiating a TNF inhibitor (infliximab, etanercept, or adalimumab), serum concentrations of formation of type I (PRO-C1), type III (PRO-C3), and type VI (PRO-C6) collagen; turnover of type IV collagen (PRO-C4), and matrix-metalloproteinase (MMP)-degraded type III (C3M) collagen, MMP-degraded type IV (C4M), type VI (C6M), and type VII (C7M) collagen, and cathepsin-degraded type X collagen (C10C), MMP-mediated metabolite of C-reactive protein (CRPM), citrullinated vimentin (VICM), and neutrophil elastase-degraded elastin (EL-NE) were measured at baseline, week 2, week 22, and week 46.

RESULTS

Patients were mostly males (82%), HLA-B27 positive (84%), with a median age of 40 years (IQR: 32-48), disease duration of 5.5 years (IQR: 2-10), and a baseline Ankylosing Spondylitis Disease Activity Score (ASDAS) of 3.9 (IQR: 3.0-4.5). Compared to baseline, PRO-C1 levels were significantly increased after two weeks of treatment, C6M levels were significantly decreased after two and 22 weeks (repeated measures ANOVA, p=0.0014 and p=0.0015, respectively), EL-NE levels were significantly decreased after 2 weeks (p=0.0008), VICM levels were significantly decreased after two and 22 weeks (p=0.0163 and p=0.0374, respectively), and CRP were significantly decreased after two and 22 weeks (both p=0.0001). Baseline levels of PRO-C1, PRO-C3, C6M, VICM, and CRP were all associated with ASDAS clinically important and major improvement after 22 weeks (ΔASDAS ≥1.1) (Mann-Whitney test, p=0.006, p=0.008, p<0.001, <0.001, <0.001, respectively), while C6M, VICM and CRP levels were associated with ASDAS clinically important and major improvement after 46 weeks (ΔASDAS ≥2.0) (p=0.002, p=0.044, and p<0.001, respectively). PRO-C1 and C6M levels were associated with a Bath AS Disease Activity Score (BASDAI) response to TNF-inhibitory therapy after 22 weeks (Mann-Whitney test, p=0.020 and p=0.049, respectively). Baseline levels of PRO-C4 and C6M were correlated with the total SPARCC MRI Spine and Sacroiliac Joint Inflammation score (Spearman's Rho ρ=0.279, p=0.043 and ρ=0.496, p=0.0002, respectively).

CONCLUSIONS

Extracellular matrix metabolites were associated with ASDAS response, MRI inflammation, and clinical treatment response during TNF-inhibitory treatment in patients with axSpA.

Mechanics of isolated individual collagen fibrils

Collagen fibrils are the fundamental structural elements in vertebrate animals and compose a framework that provides mechanical support to load-bearing tissues. Understanding how these fibrils initially form and mechanically function has been the focus of a myriad of detailed investigations over the last few decades. From these studies a great amount of knowledge has been acquired as well as a number of new questions to consider. In this review, we examine the current state of our knowledge of the mechanical properties of extant fibrils. We emphasize on the mechanical response and related deformation of collagen fibrils upon tension, which is the predominant load imposed in most collagen-rich tissues. We also illuminate the gaps in knowledge originating from the intriguing results that the field is still trying to interpret. STATEMENT OF SIGNIFICANCE: : Collagen is the result of millions of years of biological evolution and is a unique family of proteins, the majority of which provide mechanical support to biological tissues. Cells produce collagen molecules that self-assemble into larger structures, known as collagen fibrils. As simple as they appear under an optical microscope, collagen fibrils display a complex ultrastructural architecture tuned to the external forces that are imposed upon them. Even more complex is the way collagen fibrils deform under loading, and the nature of the mechanisms that drive their formation in the first place. Here, we present a cogent synthesis of the state-of-knowledge of collagen fibril mechanics. We focus on the information we have from in vitro experiments on individual, isolated from tissues, collagen fibrils and the knowledge available from in silico tests.

Low-level green laser promotes wound healing after carbon dioxide fractional laser therapy

BACKGROUND

The carbon dioxide (CO₂ ) fractional laser resurfacing has become one of the hottest therapies for dermatoses. However, complications such as skin swelling, prolonged erythema, post-inflammatory hyperpigmentation, and scar formation remain. Low-level laser (LLL) therapy is accepted to promote skin wound healing and regeneration, decrease inflammation and pain, and modulate immunoreaction with low-dose laser of different wavelength. 532 nm laser therapy is commonly used to remove pigmented spots and to tender skin, but not utilized in wound care.

OBJECTIVE

We aimed to determine the efficacy of the low-level 532 nm green laser in wound healing after CO₂ fractional laser.

METHODS

Six adult male mice (C57BL/6, 8 weeks old) were prepared for animal experiments. The dorsum of each mouse was divided into four parts that, respectively, received designed treatments, as controlled (group Ctrl), 532 nm LLL-treated (group GL), CO₂ fractional laser-treated (group FL), and CO₂ fractional laser followed by three times 532 nm LLL-treated (group FG). Hematoxylin-eosin staining (H&E), Masson-trichrome staining, CD31 immunohistochemical staining were performed to evaluate the efficacy of wound healing after treated by different irradiations. Western blotting was used to detect the expression of related proteins. Mouse skin fibroblasts (MSFs) were treated with LLL using a wavelength of 532 nm once. Cellular responses were observed and analyzed after 48 hours. Cell viability and migration of different groups were assessed by scratch and the Cell Counting Kit-8 (CCK8) assays, respectively.

RESULTS

Collagen remodeling and epidermis thickness were significantly enhanced in group FG than that in group FL in morphology. Besides, CD31 immunohistochemical staining indicated prominently increased angiogenesis in both groups FL and FG than non-irradiation group. The expression of extracellular matrix (ECM)-related protein (Col1, Col3 and MMP1) showed a remarkable improvement in wound healing in group FG than that in group FL. Irradiated MSFs showed a better migration ability compared with non-irradiated controls. LLL enhanced the secretion function of MSFs on Collagen I and III.

CONCLUSIONS

Low-level green laser promotes wound healing after CO₂ fractional laser by improving the integrity of skin barrier and allowing for scarless healing. Therefore, low-level green laser therapy might serve as a sequential therapy of invasive laser surgery to ensure a better wound care.

Clinical evaluation of muscle functions in neurofibromatosis type 1

AIM

Muscle weakness, fatigue and speech problems can occur in neurofibromatosis type 1 (NF1). The pathogenesis of these symptoms is unclear, likely multifactorial. We examined motor function in limb and speech muscles in NF1 patients.

METHODS

We evaluated NF1 and control groups aged 4-18 years for muscle strength, tone and mobility using standard manual testing, joint motion and Beighton score measurements. Speech and language functions were assessed by speech articulation and resonance. As a marker of muscle tissue turnover, we determined collagen degradation products in urine before and after submaximal exercise.

RESULTS

NF1 patients had reduced strength in proximal limb muscles compared to control subjects. Speech articulation problems and hypernasality were more common in NF1 (47% and 38%, respectively). Collagen products excreted in urine correlated with gluteal and biceps muscle strength.

CONCLUSION

Muscle dysfunction can be detected in some children with NF1 and may explain certain clinical features including fatigue, speech and articulation problems. If confirmed by further research, these findings may be relevant to the management of this condition.

Non-Viral Delivery of Gene Therapy to the Tendon

The tendon, as a compact connective tissue, is difficult to treat after an acute laceration or chronic degeneration. Gene-based therapy is a highly efficient strategy for diverse diseases which has been increasingly applied in tendons in recent years. As technology improves by leaps and bounds, a wide variety of non-viral vectors have been manufactured that attempt to have high biosecurity and transfection efficiency, considered to be a promising treatment modality. In this review, we examine the unwanted biological barriers, the categories of applicable genes, and the introduction and comparison of non-viral vectors. We focus on lipid-based nanoparticles and polymer-based nanoparticles, differentiating between them based on their combination with diverse chemical modifications and scaffolds.

Effect of Vitamin C on Tendinopathy Recovery: A Scoping Review

Tendinopathies represent 30-50% of all sports injuries. The tendon response is influenced by the load (volume, intensity, and frequency) that the tendon support, resulting in irritability and pain, among others. The main molecular component of tendons is collagen I (60-85%). The rest consist of glycosaminoglycans-proteoglycans, glycoproteins, and other collagen subtypes. This study's aim was to critically evaluate the efficacy of vitamin C supplementation in the treatment of tendinopathies. At the same time, the study aims to determine the optimal conditions (dose and time) for vitamin C supplementation. A structured search was carried out in the SCOPUS, Medline (PubMed), and Web of Science (WOS) databases. The inclusion criteria took into account studies describing optimal tendon recovery when using vitamin C alone or in combination with other compounds. The study design was considered, including randomized, double-blind controlled, and parallel designs in animal models or humans. The main outcome is that vitamin C supplementation is potentially useful as a therapeutic approach for tendinopathy recovery. Vitamin C supplementation, alone or in combination with other products, increases collagen synthesis with a consequent improvement in the patient's condition. On the other hand, vitamin C deficiency is mainly associated with a decrease in procollagen synthesis and reduced hydroxylation of proline and lysine residues, hindering the tendon repair process.

The Functions and Mechanisms of Basic Fibroblast Growth Factor in Tendon Repair

Tendon injury is a disorder of the musculoskeletal system caused by overuse or trauma, which is characterized by pain and limitations in joint function. Since tendon healing is slowly and various treatments are generally ineffective, it remains a clinically challenging problem. Recent evidences suggest that basic fibroblast growth factor (bFGF) not only plays an important role in tendon healing, but also shows a positive effect in laboratory experimentations. The purpose of this review is to summarize the effects of bFGF in the tendon healing. Firstly, during the inflammatory phase, bFGF stimulates the proliferation and differentiation of vascular endothelial cells to foster neovascularization. Furthermore, bFGF enhances the production of pro-inflammatory factors during the early phase of tendon healing, thereby accelerating the inflammatory response. Secondly, the cell proliferation phase is accompanied by the synthesis of a large number of extracellular matrix components. bFGF speeds up tendon healing by stimulating fibroblasts to secrete type III collagen. Lastly, the remodeling phase is characterized by the transition from type III collagen to type I collagen, which can be promoted by bFGF. However, excessive injection of bFGF can cause tendon adhesions as well as scar tissue formation. In future studies, we need to explore further applications of bFGF in the tendon healing process.

Genetic Disorders of the Extracellular Matrix: From Cell and Gene Therapy to Future Applications in Regenerative Medicine

Metazoans have evolved to produce various types of extracellular matrix (ECM) that provide structural support, cell adhesion, cell-cell communication, and regulated exposure to external cues. Epithelial cells produce and adhere to a specialized sheet-like ECM, the basement membrane, that is critical for cellular homeostasis and tissue integrity. Mesenchymal cells, such as chondrocytes in cartilaginous tissues and keratocytes in the corneal stroma, produce a pericellular matrix that presents optimal levels of growth factors, cytokines, chemokines, and nutrients to the cell and regulates mechanosensory signals through specific cytoskeletal and cell surface receptor interactions. Here, we discuss laminins, collagen types IV and VII, and perlecan, which are major components of these two types of ECM. We examine genetic defects in these components that cause basement membrane pathologies such as epidermolysis bullosa, Alport syndrome, rare pericellular matrix-related chondrodysplasias, and corneal keratoconus and discuss recent advances in cell and gene therapies being developed for some of these disorders. Expected final online publication date for the Annual Review of Genomics and Human Genetics, Volume 23 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Subarachnoid space of the optic nerve sheath and intracranial hypertension: a macroscopic, light and electron microscopic study

PURPOSE

The optic nerve (ON) is an extension of the central nervous system via the optic canal to the orbital cavity. It is accompanied by meninges whose arachnoid layer is in continuity with that of the chiasmatic cistern. This arachnoid layer is extended along the ON, delimiting a subarachnoid space (SAS) around the ON. Not all forms of chronic intracranial hypertension (ICH) present papilledema. The latter is sometimes asymmetric, unilateral, or absent. The radiological signs of optic nerve sheath (ONS) dilation, in magnetic resonance imaging, are inconsistent or difficult to interpret. The objective of this study was to analyze the anatomy, the constitution, and the variability of the SAS around the ON in its intraorbital segment to improve the understanding of the pathophysiologic mechanism of asymmetric or unilateral or absent papilledema in certain ICH.

METHODS

The study was carried out on nine cadaveric specimens. In four embalmed specimens, macroscopic analysis of the SAS of the ONS were performed, with description about density of the arachnoid trabecular meshwork in three distinct areas (bulbar segment, mid-orbital segment and the precanal segment). In three other embalmed specimens, after staining of SAS by methylene blue (MB), we performed macroscopic analysis of MB progression in the SAS of the ONS. Then, in two non-embalmed specimens, light and electron microscopy (EM) analysis were also done.

RESULTS

On the macroscopic level, after staining of SAS, we found in all cases that MB progressed on 16 mm average throughout the SAS of the ONS without reaching the papilla. In four embalmed specimens, in the SAS of the ONS, the density of the arachnoid trabecular meshwork showed inter-individual variability (100%) and intra-individual variability with bilateral variability (50%) and/or variability within the same ONS (88%). On the microscopic level, the arachnoid trabeculae of the ONS are composed of dense connective tissue. The EM perfectly depicted its composition which is mainly of collagen fibers of parallel orientation.

CONCLUSION

The variability of the SAS around the ONS probably impacts the symmetrical or asymmetrical nature of papilledema in ICH.

Small Leucine-Rich Proteoglycans in Tendon Wound Healing

Significance: Tendon injury possesses a high morbidity rate and is difficult to achieve a satisfying prognosis with currently available treatment strategies. Current approaches used for tendon healing always lead to the formation of fibrovascular scar tissue, which significantly compromises the biomechanics of the healed tendon. Moreover, the related functional deficiency deteriorates over time with an increased injury recurrence risk. Small leucine-rich proteoglycans (SLRPs) link and interact with collagen fibrils to regulate tendon structure and biomechanics, which can provide a new and promising method in the field of tendon injury management. Recent Advances: The effect of SLRPs on tendon development has been extensively investigated. SLRP deficiency impairs tendon collagen fibril structure and biomechanic properties, while administration of SLRPs generally benefits tendon wound healing and regains better mechanical properties. Critical Issues: Current knowledge on the role of SLRPs in tendon development and regeneration mostly comes from uninjured knockout mice, and mainly focuses on the morphology description of collagen fibril profile and mechanical properties. Little is known about the regulatory mechanism on the molecular level. Future Directions: This article reviews the current knowledge in this highly translational topic and provides an evidence-based conclusion, thereby encouraging in-depth investigations of SLRPs in tendons and the development of SLRP-based treatments for desired tendon healing.

Correlation between diffusion kurtosis and intravoxel incoherent motion derived (IVIM) parameters and tumor tissue composition in rectal cancer: a pilot study

PURPOSE

To correlate non-invasive quantitative diffusion kurtosis imaging (DKI) and intravoxel incoherent motion-derived (IVIM) parameters with rectal cancer composition assessed by the expression of caudal-type homeobox 2 (CDX-2), Vimentin (VIM), CD34 and Ki-67 on resected tissues, as well as the tumor stroma ratio (TSR) and the results of H&E and Masson staining.

MATERIALS AND METHODS

A prospective study of 26 patients with rectal cancer who underwent magnetic resonance (MR) imaging, including DKI with 4 b values and IVIM at 3.0 T prior to surgery. Primary tumor was harvested and fixed for H&E, immunohistochemistry and Masson staining. One-way ANOVA was used to test the differences. Pearson correlation coefficients and multiple linear regression analyses were applied to evaluation the correlations.

RESULTS

The apparent diffusion coefficient (ADC_DKI) and MK_DKI all exhibited significant differences in subgroups with different T stages (P < 0.05) and among high- and low- grade rectal cancer (P < 0.05). MD_DKI showed a moderate negative correlation with CDX-2 (r = - 0.42, P = 0.040) and a moderate positive correlation with CD34 (r = 0.42, P = 0.041). ADC_IVIM exhibited a moderate positive correlation with Masson staining (r = 0.426, P = 0.048) D_IVIM showed a moderate negative correlation with CDX-2 (r = - 0.58, P = 0.005). [Formula: see text] showed a moderate positive correlation with VIM (r = 0.445, P = 0.033).

CONCLUSION

ADC_DKI and MK_DKI demonstrated a higher correlation with T stages and histologic grades. MD_DKI showed significant correlations with CDX-2 and CD34. ADC_IVIM showed significant correlation with Masson. D_IVIM showed significant correlations with CDX-2 and [Formula: see text] showed significant correlation with VIM. These findings should be validated in a larger study.

Into the Tissues: Extracellular Matrix and Its Artificial Substitutes: Cell Signalling Mechanisms

The existence of orderly structures, such as tissues and organs is made possible by cell adhesion, i.e., the process by which cells attach to neighbouring cells and a supporting substance in the form of the extracellular matrix. The extracellular matrix is a three-dimensional structure composed of collagens, elastin, and various proteoglycans and glycoproteins. It is a storehouse for multiple signalling factors. Cells are informed of their correct connection to the matrix via receptors. Tissue disruption often prevents the natural reconstitution of the matrix. The use of appropriate implants is then required. This review is a compilation of crucial information on the structural and functional features of the extracellular matrix and the complex mechanisms of cell-cell connectivity. The possibilities of regenerating damaged tissues using an artificial matrix substitute are described, detailing the host response to the implant. An important issue is the surface properties of such an implant and the possibilities of their modification.

Coordinate roles for collagen VI and biglycan in regulating tendon collagen fibril structure and function

Tendon is a vital musculoskeletal tissue that is prone to degeneration. Proper tendon maintenance requires complex interactions between extracellular matrix components that remain poorly understood. Collagen VI and biglycan are two matrix molecules that localize pericellularly within tendon and are critical regulators of tissue properties. While evidence suggests that collagen VI and biglycan interact within the tendon matrix, the relationship between the two molecules and its impact on tendon function remains unknown. We sought to elucidate potential coordinate roles of collagen VI and biglycan within tendon by defining tendon properties in knockout models of collagen VI, biglycan, or both molecules. We first demonstrated co-expression and co-localization of collagen VI and biglycan within the healing tendon, providing further evidence of cooperation between the two molecules during nascent tendon matrix formation. Deficiency in collagen VI and/or biglycan led to significant reductions in collagen fibril size and tendon mechanical properties. However, collagen VI-null tendons displayed larger reductions in fibril size and mechanics than seen in biglycan-null tendons. Interestingly, knockout of both molecules resulted in similar properties to collagen VI knockout alone. These results indicate distinct and non-additive roles for collagen VI and biglycan within tendon. This work provides better understanding of regulatory interactions between two critical tendon matrix molecules.

Antimicrobial effectiveness of wound matrices containing native extracellular matrix with polyhexamethylene biguanide

A variety of wound matrix materials that are designed to help heal both acute and chronic wounds are currently available. Because wounds often encounter opportunistic microbes that can delay healing, the effectiveness of these materials is often suboptimal, resulting in delayed or compromised wound healing. The importance of reducing and controlling wound microbes is well recognised and there are several antimicrobial options available to address this unmet clinical need. This study compares the antimicrobial and wound healing capabilities, both in vivo and in vitro against methicillin-resistant Staphylococcus aureus (MRSA) USA 300, for the following compounds: Collagen Wound Matrix-Anti Microbial (CWM-AM); Collagen Wound Matrix-Anti Microbial XT (CWM-AM XT); Antimicrobial Hydrofiber Wound Dressing (AHWD); Dermal Scaffold with Silver (DRSAg); Collagen Extracellular Matrix (CEM); Collagen Wound Matrix (CWM); Matrix Wound Dressing with Silver (MWDAg); Cadexomer Iodine Gel (CIG); Triple Antibiotic Ointment (TAO); and Antimicrobial Wound Gel (AWG). For the in vitro zone of inhibition assay, AWG and CIG had the largest diffused areas, followed by CWM-AM and CWM-AM XT. Furthermore, CWM-AM, CWM-AM XT, AWG, and CIG exhibited a persistent antimicrobial activity for up to 10 days after incubation. However, in the cytotoxicity studies performed using human fibroblasts, CWM-AM and CWM-AM XT had no detrimental effects in cell proliferation and viability, while AWG and CIG were cytotoxic and prohibitive for cell proliferation. Treatments were then assessed for microbiology and wound healing efficacy using an in vivo porcine deep reticular dermal wound model. CWM-AM XT displayed the greatest in vivo antimicrobial activity against MRSA USA300 and expedited the reepithelialisation at a faster rate than other treatment groups. This study shows that a novel collagen matrix containing an antimicrobial agent can reduce the bacterial load and support healing.

Nutritional Considerations for Injury Prevention and Recovery in Combat Sports

Sports participation is not without risk, and most athletes incur at least one injury throughout their careers. Combat sports are popular all around the world, and about one-third of their injuries result in more than 7 days of absence from competition or training. The most frequently injured body regions are the head and neck, followed by the upper and lower limbs, while the most common tissue types injured are superficial tissues and skin, followed by ligaments and joint capsules. Nutrition has significant implications for injury prevention and enhancement of the recovery process due to its effect on the overall physical and psychological well-being of the athlete and improving tissue healing. In particular, amino acid and protein intake, antioxidants, creatine, and omega-3 are given special attention due to their therapeutic roles in preventing muscle loss and anabolic resistance as well as promoting injury healing. The purpose of this review is to present the roles of various nutritional strategies in reducing the risk of injury and improving the treatment and rehabilitation process in combat sports. In this respect, nutritional considerations for muscle, joint, and bone injuries as well as sports-related concussions are presented. The injury risk associated with rapid weight loss is also discussed. Finally, preoperative nutrition and nutritional considerations for returning to a sport after rehabilitation are addressed.

Collagen/Chitosan Gels Cross-Linked with Genipin for Wound Healing in Mice with Induced Diabetes

Diabetes mellitus continues to be one of the most common diseases often associated with diabetic ulcers. Chitosan is an attractive biopolymer for wound healing due to its biodegradability, biocompatibility, mucoadhesiveness, low toxicity, and hemostatic effect. A panel of hydrogels based on chitosan, collagen, and silver nanoparticels were produced to treat diabetic wounds. The antibacterial activity, cytotoxicity, swelling, rheological properties, and longitudinal sections of hydrogels were studied. The ability of the gels for wound healing was studied in CD1 mice with alloxan-induced diabetes. Application of the gels resulted in an increase in VEGF, TGF-b1, IL-1b, and TIMP1 gene expression and earlier wound closure in a comparison with control untreated wounds. All gels increased collagen deposition, hair follicle repair, and sebaceous glands formation. The results of these tests show that the obtained hydrogels have good mechanical properties and biological activity and have potential applications in the field of wound healing. However, clinical studies are required to compare the efficacy of the gels as animal models do not reproduce full diabetes pathology.

Heterologous expression, fermentation strategies and molecular modification of collagen for versatile applications

Collagen is a kind of high macromolecular protein with unique tissue distribution and distinctive functions in the body. At present, most collagen products are extracted from the tissues and organs of mammals or marine fish. However, this method exhibits several disadvantages, including low efficiency and serious waste generation, which makes it difficult to meet the current market demand. With the rapid development of synthetic biology and the deepening of high-density fermentation technology, the collagen preparation by biosynthesis strategy emerges as the times require. Co-expression with the proline hydroxylase gene can solve the problem of non-hydroxylated collagen, but the yield may be affected. Therefore, improving the expression through molecular modification and dynamic regulation of synthesis is an entry point for future research. Due to the defects in certain properties of the natural collagen, modification of properties would be benefit for meeting the requirements of practical application. In this paper, in-depth investigations on recombinant expression, fermentation, and modification studies of collagen are conducted. Also, it summarizes the research progress of collagen in food, medicine, and beauty industry in recent years. Furthermore, the future development trend and application prospect of collagen are discussed, which would provide guidance for its preparation and application.

Four decades in the making: Collagen III and mechanisms of vascular Ehlers Danlos Syndrome

Vascular Ehlers Danlos (vEDS) syndrome is a severe multi-systemic connective tissue disorder characterized by risk of dissection and rupture of the arteries, gastro-intestinal tract and gravid uterus. vEDS is caused by mutations in COL3A1, that encodes the alpha 1 chain of type III collagen, which is a major extracellular matrix component of the vasculature and hollow organs. The first causal mutations were identified in the 1980s but progress in our understanding of the pathomolecular mechanisms has been limited. Recently, the application of more refined animal models combined with global omics approaches has yielded important new insights both in terms of disease mechanisms and potential for therapeutic intervention. However, it is also becoming apparent that vEDS is a complex disorder in terms of its molecular disease mechanisms with a poorly understood allelic and mechanistic heterogeneity. In this brief review we will focus our attention on the disease mechanisms of COL3A1 mutations and vEDS, and recent progress in therapeutic approaches using animal models.