Main and Minor Types of Collagens in the Articular Cartilage: The Role of Collagens in Repair Tissue Evaluation in Chondral Defects

Transcriptomic meta-analysis and exploration of differentially expressed gene functions in wooden breast myopathy of broilers

Wooden breast (WB) myopathy is a common myopathy found in commercial broiler chickens worldwide. Although extensive research on WB has been conducted using transcriptomics, effectively screening and analyzing key target information remains a challenge. In this present study, 5 transcriptomic datasets obtained from the National Center for Biotechnology Information (NCBI) were used. A meta-analysis was conducted to identify meta-differentially expressed genes (meta-DEGs) involved in the response of broilers to WB myopathy. These meta-DEGs were further analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and Gene Set Enrichment Analysis (GSEA), supplemented by protein-protein interaction (PPI) network construction to pinpoint hub genes. These analyses help to reveal key genes, pathways, and biological processes associated with WB myopathy. The results showed that 645 up-regulated and 99 down-regulated significant meta-DEGs (|log2FC| ≥0.6, P-Meta < 0.05, and present in at least 4 datasets) were identified. GO analysis showed that multiple fibrosis-related pathways/biological processes, such as cell adhesion, connective tissue development, and collagen-rich extracellular matrix, as well as calcium ion binding were significantly upregulated. PPI analysis identified TGFB3, COL1A1, COL1A2, and COL3A1 as central hub genes involved in the fibrotic processes. KEGG analysis revealed significant upregulation of apoptosis and lysosomal pathways, with an enrichment of Ca2+-related signals and lysosomal cathepsins within the apoptosis pathway. Additionally, GSEA indicated a suppression of the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain (ETC) in WB myopathy, with PPI analysis also identifying specific hub genes associated with these pathways. In conclusion, our comprehensive analysis of meta-DEGs elucidated key biological processes and pathways implicated in WB myopathy, including fibrosis, apoptosis, altered calcium signaling, and metabolic disruption. The identification of specific hub genes offers avenues for further investigation into the pathogenesis of this condition, potentially guiding targeted therapeutic strategies.

Changes of bone and articular cartilage in broilers with femoral head necrosis

Femoral head necrosis (FHN) in broilers is a common leg disorder in intensive poultry farming, giving rise to poor animal health and welfare. Abnormal mechanical stress in the hip joint is a risk factor for FHN, and articular cartilage is attracting increasing attention as a cushion and lubrication structure for the joint. In the present study, broilers aged 3 to 4 wk with FHN were divided into femoral head separation (FHS) and femoral head separation with growth plate lacerations (FHSL) groups, with normal broilers as control. The features of the hip joint, bone, and cartilage were assessed in FHN progression using devices including computed tomography (CT), atomic force microscope (AFM), and transmission electron microscopy (TEM). Broilers with FHN demonstrated decreased bone mechanical properties, narrow joint space, and thickened femoral head stellate structures. Notably, abnormal cartilage morphology was observed in FHN-affected broilers, characterized by increased cartilage thickness and rough cartilage surfaces. In addition, as FHN developed, cartilage surface friction and friction coefficient dramatically increased, while cartilage modulus and stiffness decreased. The ultramicro-damage occurred in chondrocytes and the extracellular matrix (ECM) of cartilage. Cell disintegration, abnormal mitochondrial accumulation, and oxidative stress damage were observed in chondrocytes. A notable decline in cartilage collagen content was observed in ECM during the initial stages of FHN, accompanied by a pronounced reduction in collagen fiber diameter and proteoglycan content as FHN progressed. Furthermore, the noticeable loosening of the collagen fiber structure and the appearance of type I collagen were noted in cartilage. In conclusion, there was a progressive decrease in bone quality and multifaceted damage of cartilage in the femoral head, which was closely linked to the severity of FHN in broilers.

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.

Non-apoptotic cell death in osteoarthritis: Recent advances and future

Osteoarthritis (OA) is the most common degenerative joint disease. Multiple tissues are altered during the development of OA, resulting in joint pain and permanent damage to the osteoarticular joints. Current research has demonstrated that non-apoptotic cell death plays a crucial role in OA. With the continuous development of targeted therapies, non-apoptotic cell death has shown great potential in the prevention and treatment of OA. We systematically reviewed research progress on the role of non-apoptotic cell death in the pathogenesis, development, and outcome of OA, including autophagy, pyroptosis, ferroptosis, necroptosis, immunogenic cell death, and parthanatos. This article reviews the mechanism of non-apoptotic cell death in OA and provides a theoretical basis for the identification of new targets for OA treatment.

Collagen and Its Derivatives Serving Biomedical Purposes: A Review

Biomaterials have been the subject of extensive research, and their applications in medicine and pharmacy are expanding rapidly. Collagen and its derivatives stand out as valuable biomaterials due to their high biocompatibility, biodegradability, and lack of toxicity and immunogenicity. This review comprehensively examines collagen from various sources, its extraction and processing methods, and its structural and functional properties. Preserving the native state of collagen is crucial for maintaining its beneficial characteristics. The challenges associated with chemically modifying collagen to tailor its properties for specific clinical needs are also addressed. The review discusses various collagen-based biomaterials, including solutions, hydrogels, powders, sponges, scaffolds, and thin films. These materials have broad applications in regenerative medicine, tissue engineering, drug delivery, and wound healing. Additionally, the review highlights current research trends related to collagen and its derivatives. These trends may significantly influence future developments, such as using collagen-based bioinks for 3D bioprinting or exploring new collagen nanoparticle preparation methods and drug delivery systems.

Harnessing Peptide-Based Hydrogels for Enhanced Cartilage Tissue Engineering

Cartilage tissue engineering remains a formidable challenge due to its complex, avascular structure and limited regenerative capacity. Traditional approaches, such as microfracture, autografts, and stem cell delivery, often fail to restore functional tissue adequately. Recently, there has been a surge in the exploration of new materials that mimic the extracellular microenvironment necessary to guide tissue regeneration. This review investigates the potential of peptide-based hydrogels as an innovative solution for cartilage regeneration. These hydrogels, formed via supramolecular self-assembly, exhibit excellent properties, including biocompatibility, ECM mimicry, and controlled biodegradation, making them highly suitable for cartilage tissue engineering. This review explains the structure of cartilage and the principles of supramolecular and peptide hydrogels. It also delves into their specific properties relevant to cartilage regeneration. Additionally, this review presents recent examples and a comparative analysis of various peptide-based hydrogels used for cartilage regeneration. The review also addresses the translational challenges of these materials, highlighting regulatory hurdles and the complexities of clinical application. This comprehensive investigation provides valuable insights for biomedical researchers, tissue engineers, and clinical professionals aiming to enhance cartilage repair methodologies.

Effects of the oral administration of glycosaminoglycans with or without native type II collagen on the articular cartilage transcriptome in an osteoarthritic-induced rabbit model

BACKGROUND

In a previous study, the 84-day administration of glycosaminoglycans (GAGs), with or without native collagen type II (NC), in an osteoarthritis (OA)-induced rabbit model slowed down OA progression, improved several micro- and macroscopic parameters and magnetic resonance imaging (MRI) biomarkers in cartilage, and increased hyaluronic acid levels in synovial fluid. To elucidate the potential underlying mechanisms, a transcriptomics approach was conducted using medial femoral condyle and trochlea samples.

RESULTS

The administration of chondroitin sulfate (CS), glucosamine hydrochloride (GlHCl), and hyaluronic acid (HA), with (CGH-NC) or without (CGH) NC, strongly modulated several genes involved in chondrocyte extracellular matrix (ECM) remodeling and homeostasis when compared to non-treated rabbits (CTR group). Notably, both treatments shared the main mechanism of action, which was related to ECM modulation through the down-regulation of genes encoding proteolytic enzymes, such as ADAM metallopeptidase with thrombospondin type 1 motif, 9 (Adamts9), and the overexpression of genes with a relevant role in the synthesis of ECM components, such as aggrecan (Acan) in both CGH-NC and CGH groups, and fibronectin 1 (Fn1) and collagen type II, alpha 1 (Col2A1) in the CGH group. Furthermore, there was a significant modulation at the gene expression level of the mTOR signaling pathway, which is associated with the regulation of the synthesis of ECM proteolytic enzymes, only in CGH-NC-supplemented rabbits. This modulation could account for the better outcomes concerning the microscopic and macroscopic evaluations reported in these animals.

CONCLUSIONS

In conclusion, the expression of key genes involved in chondrocyte ECM remodeling and homeostasis was significantly modulated in rabbits in response to both CGH and CGH-NC treatments, which would partly explain the mechanisms by which these therapies exert beneficial effects against OA.

Biosynthesis of a Functional Fragment of Human Collagen II in Pichia pastoris

Collagen II (COL2) is the major component of cartilage tissue and is widely applied in pharmaceuticals, food, and cosmetics. In this study, COL fragments were extracted from human COL2 for secretory expression in Pichia pastoris. Three variants were successfully secreted by shake flask cultivation with a yield of 73.3-100.7 mg/L. The three COL2 variants were shown to self-assemble into triple-helix at 4 °C and capable of forming higher order assembly of nanofiber and hydrogel. The bioactivities of the COL2 variants were validated, showing that sample 205 exhibited the best performance for inducing fibroblast differentiation and cell migration. Meanwhile, sample 205 and 209 exhibited higher capacity for inducing in vitro blood clotting than commercial mouse COL1. To overexpress sample 205, the expression cassettes were constructed with different promoters and signal peptides, and the fermentation condition was optimized, obtaining a yield of 172 mg/L for sample 205. Fed-batch fermentation was carried out using a 5 L bioreactor, and the secretory protease Pep4 was knocked out to avoid sample degradation, finally obtaining a yield of 3.04 g/L. Here, a bioactive COL2 fragment was successfully identified and can be overexpressed in P. pastoris; the variant may become a potential biomaterial for skin care.

Exploring the Role of the Microbiome in Rheumatoid Arthritis-A Critical Review

Rheumatoid arthritis (RA) is a chronic, autoimmune rheumatic disease characterized by synovial joint inflammation with subsequent destruction as well as systemic manifestation, leading to impaired mobility and impaired quality of life. The etiopathogenesis of RA is still unknown, with genetic, epigenetic and environmental factors (incl. tobacco smoking) contributing to disease susceptibility. The link between genetic factors like "shared epitope alleles" and the development of RA is well known. However, why only some carriers have a break in self-tolerance and develop autoimmunity still needs to be clarified. The presence of autoantibodies in patients' serum months to years prior to the onset of clinical manifestations of RA has moved the focus to possible epigenetic factors, including environmental triggers that could contribute to the initiation and perpetuation of the inflammatory reaction in RA. Over the past several years, the role of microorganisms at mucosal sites (i.e., microbiome) has emerged as an essential mediator of inflammation in RA. An increasing number of studies have revealed the microbial role in the immunopathogenesis of autoimmune rheumatic diseases. Interaction between the host immune system and microbiota initiates loss of immunological tolerance and autoimmunity. The alteration in microbiome composition, the so-called dysbiosis, is associated with an increasing number of diseases. Immune dysfunction caused by dysbiosis triggers and sustains chronic inflammation. This review aims to provide a critical summary of the literature findings related to the hypothesis of a reciprocal relation between the microbiome and the immune system. Available data from studies reveal the pivotal role of the microbiome in RA pathogenesis.

Meniscal repair with additive manufacture of bioresorbable polymer: From physicochemical characterization to implantation of 3D printed poly (L-co-D, L lactide-co-trimethylene carbonate) with autologous stem cells in rabbits

Three-dimensional (3D) structures are actually the state-of-the-art technique to create porous scaffolds for tissue engineering. Since regeneration in cartilage tissue is limited due to intrinsic cellular properties this study aims to develop and characterize three-dimensional porous scaffolds of poly (L-co-D, L lactide-co-trimethylene carbonate), PLDLA-TMC, obtained by 3D fiber deposition technique. The PLDLA-TMC terpolymer scaffolds (70:30), were obtained and characterized by scanning electron microscopy, gel permeation chromatography, differential scanning calorimetry, thermal gravimetric analysis, compression mechanical testing and study on in vitro degradation, which showed its amorphous characteristics, cylindrical geometry, and interconnected pores. The in vitro degradation study showed significant loss of mechanical properties compatible with a decrease in molar mass, accompanied by changes in morphology. The histocompatibility association of mesenchymal stem cells from rabbit's bone marrow, and PLDLA-TMC scaffolds, were evaluated in the meniscus regeneration, proving the potential of cell culture at in vivo tissue regeneration. Nine New Zealand rabbits underwent total medial meniscectomy, yielding three treatments: implantation of the seeded PLDLA-TMC scaffold, implantation of the unseeded PLDLA-TMC and negative control (defect without any implant). After 24 weeks, the results revealed the presence of fibrocartilage in the animals treated with polymer. However, the regeneration obtained with the seeded PLDLA-TMC scaffolds with mesenchymal stem cells had become intimal to mature fibrocartilaginous tissue of normal meniscus both macroscopically and histologically. This study demonstrated the effectiveness of the PLDLA-TMC scaffold in meniscus regeneration and the potential of mesenchymal stem cells in tissue engineering, without the use of growth factors. It is concluded that bioresorbable polymers represent a promising alternative for tissue regeneration.

3D Bioprinting Strategies for Articular Cartilage Tissue Engineering

Articular cartilage is the avascular and aneural tissue which is the primary connective tissue covering the surface of articulating bone. Traumatic damage or degenerative diseases can cause articular cartilage injuries that are common in the population. As a result, the demand for new therapeutic options is continually increasing for older people and traumatic young patients. Many attempts have been made to address these clinical needs to treat articular cartilage injuries, including osteoarthritis (OA); however, regenerating highly qualified cartilage tissue remains a significant obstacle. 3D bioprinting technology combined with tissue engineering principles has been developed to create biological tissue constructs that recapitulate the anatomical, structural, and functional properties of native tissues. In addition, this cutting-edge technology can precisely place multiple cell types in a 3D tissue architecture. Thus, 3D bioprinting has rapidly become the most innovative tool for manufacturing clinically applicable bioengineered tissue constructs. This has led to increased interest in 3D bioprinting in articular cartilage tissue engineering applications. Here, we reviewed current advances in bioprinting for articular cartilage tissue engineering.

A thorough analysis of data on the correlation between COL9A1 polymorphisms and the susceptibility to congenital talipes equinovarus: a meta-analysis

BACKGROUND

Congenital talipes equinovarus (CTEV) is a prevalent pediatric deformity with a multifactorial etiology. The objective of this meta-analysis was to explore the association between genetic variations in COL9A1 and the susceptibility to CTEV.

METHODS

A comprehensive analysis of pertinent literature released before November 15, 2023, in electronic bibliographic databases was carried out. The importance of the connection was clarified through odds ratios (ORs) with 95% confidence intervals (CIs), utilizing random or fixed-effects models depending on study heterogeneity. Statistical analysis was executed using Comprehensive Meta-Analysis software (Version 4.0).

RESULTS

A total of eight case-control studies involving 833 CTEV patients and 1280 healthy individuals were included in the analysis. Among these, four studies investigated the rs1135056 variant, encompassing 432 CTEV cases and 603 controls; two studies examined the rs35470562 variant, with 189 CTEV cases and 378 controls; and two studies explored the rs592121 variant, including 212 CTEV cases and 299 controls. The results revealed a significant association between the rs1135056 and rs35470562 polymorphisms in the COL9A1 gene, suggesting an increased risk of CTEV in the overall population. Conversely, no such association was found for the rs592121 variant.

CONCLUSION

Our findings reveal a substantial association between the genetic variants COL9A1 rs1135056 and rs35470562 and susceptibility to CTEV. Conversely, the variant rs592121 did not exhibit any corresponding link. However, the limitations imposed by the small study population have compromised the statistical reliability and generalizability of the results.

Type IX Collagen Turnover Is Altered in Patients with Solid Tumors

The fibrotic tumor microenvironment, characterized by its intricate extracellular matrix (ECM), consists of many collagens with diverse functions and unexplored biomarker potential. Type IX collagen is a member of the low-abundance collagen family known as the fibril-associated collagen with interrupted triple helices (FACITs) and is found mostly in cartilage. Its role in the tumor microenvironment remains unexplored. To investigate the biomarker potential of a type IX collagen in cancer, an immuno-assay was developed (PRO-C9) and technical assay performance was evaluated for the assessment of serum. PRO-C9 levels were measured in serum samples from 259 patients with various solid tumor types compared to serum levels from 73 healthy controls. PRO-C9 levels were significantly elevated in patients with solid tumors including bladder, breast, colorectal, gastric, head and neck, lung, melanoma, ovarian, pancreatic, and renal compared to levels in healthy controls (p < 0.05-p < 0.0001). PRO-C9 could discriminate between patients with cancer and healthy controls, with the area under the receiver operating characteristic values ranging from 0.58 to 0.86 (p < 0.3-p < 0.0001), indicating potential diagnostic utility. This study suggests that type IX collagen turnover is altered in patients with solid tumors and demonstrates the feasibility of using PRO-C9 as a non-invasive serum-based biomarker with relevance in multiple cancer types. Furthermore, these results underscore the potential utility of PRO-C9 to better elucidate the biology of FACITs in cancers.

Electrical Stimulation of Mesenchymal Stem Cells as a Tool for Proliferation and Differentiation in Cartilage Tissue Engineering: A Scaffold-Based Approach

Electrical stimulation (ES) is a widely discussed topic in the field of cartilage tissue engineering due to its ability to induce chondrogenic differentiation (CD) and proliferation. It shows promise as a potential therapy for osteoarthritis (OA). In this study, we stimulated mesenchymal stem cells (MSCs) incorporated into collagen hydrogel (CH) scaffolds, consisting of approximately 500,000 cells each, for 1 h per day using a 2.5 Vpp (119 mV/mm) 8 Hz sinusoidal signal. We compared the cell count, morphology, and CD on days 4, 7, and 10. The results indicate proliferation, with an increase ranging from 1.86 to 9.5-fold, particularly on day 7. Additionally, signs of CD were observed. The stimulated cells had a higher volume, while the stimulated scaffolds showed shrinkage. In the ES groups, up-regulation of collagen type 2 and aggrecan was found. In contrast, SOX9 was up-regulated in the control group, and MMP13 showed a strong up-regulation, indicating cell stress. In addition to lower stress levels, the control groups also showed a more spheroidic shape. Overall, scaffold-based ES has the potential to achieve multiple outcomes. However, finding the appropriate stimulation pattern is crucial for achieving successful chondrogenesis.

Sericin promotes chondrogenic proliferation and differentiation via glycolysis and Smad2/3 TGF-β signaling inductions and alleviates inflammation in three-dimensional models

Knee osteoarthritis is a chronic joint disease mainly characterized by cartilage degeneration. The treatment is challenging due to the lack of blood vessels and nerve supplies in cartilaginous tissue, causing a prominent limitation of regenerative capacity. Hence, we investigated the cellular promotional and anti-inflammatory effects of sericin, Bombyx mori-derived protein, on three-dimensional chondrogenic ATDC5 cell models. The results revealed that a high concentration of sericin promoted chondrogenic proliferation and differentiation and enhanced matrix production through the increment of glycosaminoglycans, COL2A1, COL X, and ALP expressions. SOX-9 and COL2A1 gene expressions were notably elevated in sericin treatment. The proteomic analysis demonstrated the upregulation of phosphoglycerate mutase 1 and triosephosphate isomerase, a glycolytic enzyme member, reflecting the proliferative enhancement of sericin. The differentiation capacity of sericin was indicated by the increased expressions of procollagen12a1, collagen10a1, rab1A, periostin, galectin-1, and collagen6a3 proteins. Sericin influenced the differentiation capacity via the TGF-β signaling pathway by upregulating Smad2 and Smad3 while downregulating Smad1, BMP2, and BMP4. Importantly, sericin exhibited an anti-inflammatory effect by reducing IL-1β, TNF-α, and MMP-1 expressions and accelerating COL2A1 production in the early inflammatory stage. In conclusion, sericin demonstrates potential in promoting chondrogenic proliferation and differentiation, enhancing cartilaginous matrix synthesis through glycolysis and TGF-β signaling pathways, and exhibiting anti-inflammatory properties.

Osteoarthritis: Insights into Diagnosis, Pathophysiology, Therapeutic Avenues, and the Potential of Natural Extracts

Osteoarthritis (OA) stands as a prevalent and progressively debilitating clinical condition globally, impacting joint structures and leading to their gradual deterioration through inflammatory mechanisms. While both non-modifiable and modifiable factors contribute to its onset, numerous aspects of OA pathophysiology remain elusive despite considerable research strides. Presently, diagnosis heavily relies on clinician expertise and meticulous differential diagnosis to exclude other joint-affecting conditions. Therapeutic approaches for OA predominantly focus on patient education for self-management alongside tailored exercise regimens, often complemented by various pharmacological interventions primarily targeting pain alleviation. However, pharmacological treatments typically exhibit short-term efficacy and local and/or systemic side effects, with prosthetic surgery being the ultimate resolution in severe cases. Thus, exploring the potential integration or substitution of conventional drug therapies with natural compounds and extracts emerges as a promising frontier in enhancing OA management. These alternatives offer improved safety profiles and possess the potential to target specific dysregulated pathways implicated in OA pathogenesis, thereby presenting a holistic approach to address the condition's complexities.

Intermediate-Term Clinical Outcomes of High-Density Autologous Chondrocyte Implantation in Patients with Concomitant Anterior Cruciate Ligament Reconstruction and Focal Chondral Lesions

OBJECTIVE

To investigate intermediate-term clinical results in patients with concomitant anterior cruciate ligament (ACL) reconstruction and chondral defect treated with high-density autologous chondrocyte implantation (HD-ACI) compared to patients without ACL tear but with a chondral lesion and HD-ACI treatment.

DESIGN

Forty-eight patients with focal chondral lesions underwent HD-ACI (24 with ACL reconstruction after an ACL injury and 24 with an intact ACL). Follow-up assessments occurred at 6, 12, and 24 months. Patient-reported knee function and symptoms were assessed using the International Knee Documentation Committee (IKDC) questionnaire, pain was measured using the Visual Analog Scale (VAS), and adverse events were monitored. Physical activity was assessed using the Tegner Activity Level Scale, and cartilage healing was evaluated with the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) score.

RESULTS

No significant adverse events occurred during follow-up. Both groups showed significant improvements at 2 years compared to baseline (VAS: 8.0 ± 1.3 to 1.4 ± 2.0 [normal ACL]; 7.4 ± 2.3 to 2.1 ± 2.3 [ACL reconstruction]; IKDC: 39.2 ± 10.6 to 76.1 ± 22.0 [intact ACL]; 35.6 ± 12.1 to 74.6 ± 20.9 [ACL reconstruction]). Patients in both groups exceeded the minimal clinically important difference (MCID) for IKDC scores. The Tegner Activity Level Scale decreased immediately after surgery and increased after 2 years, with 70.6% (normal ACL) and 89.5% (ACL reconstruction) returning to their preinjury activity levels. No significant differences in the MOCART score were observed between the groups.

CONCLUSIONS

ACL reconstruction does not appear to reduce the outcomes (at 2 years) of HD-ACI.

Use of Collagen in Cosmetic Products

Collagen (CLG) belongs to the family of fibrillar proteins and is composed of left-handed α polypeptide chains, which, twisting around themselves and their axis, form a right-handed superhelix. In the chemical structure, it contains mainly proline, hydroxyproline, glycine, and hydroxylysine. It occurs naturally in the dermis in the form of fibers that provide the skin with proper density and elasticity. The review aimed to present the types of collagen protein, factors affecting its structure and its unusual role in the functioning of the human body. Also, an overview of cosmetic products containing collagen or its derivatives, the characteristics of the formulas of these products, and the effects of their use were presented. Throughout the market, there are many cosmetic and cosmeceutical products containing CLG. They are in the form of fillers administered as injections, belonging to the group of the oldest tissue fillers; products administered orally and for topical use, such as creams, gels, serums, or cosmetic masks. Analyzed studies have shown that the use of products with collagen or its peptides improves the general condition of the skin and delays the aging process by reducing the depth of wrinkles, improving hydration (in the case of oral preparations), reducing transepithelial water loss (TEWL), as well as improving skin density and elasticity. In addition, oral application of bioactive CLG peptides has shown a positive effect on the nails, reducing the frequency of their breakage.

Passaged Articular Chondrocytes From the Superficial Zone and Deep Zone Can Regain Zone-Specific Properties After Redifferentiation

BACKGROUND

Bioengineered cartilage is a developing therapeutic to repair cartilage defects. The matrix must be rich in collagen type II and aggrecan and mechanically competent, withstanding compressive and shearing loads. Biomechanical properties in native articular cartilage depend on the zonal architecture consisting of 3 zones: superficial, middle, and deep. The superficial zone chondrocytes produce lubricating proteoglycan-4, whereas the deep zone chondrocytes produce collagen type X, which allows for integration into the subchondral bone. Zonal and chondrogenic expression is lost after cell number expansion. Current cell-based therapies have limited capacity to regenerate the zonal structure of native cartilage.

HYPOTHESIS

Both passaged superficial and deep zone chondrocytes at high density can form bioengineered cartilage that is rich in collagen type II and aggrecan; however, only passaged superficial zone-derived chondrocytes will express superficial zone-specific proteoglycan-4, and only passaged deep zone-derived chondrocytes will express deep zone-specific collagen type X.

STUDY DESIGN

Controlled laboratory study.

METHODS

Superficial and deep zone chondrocytes were isolated from bovine joints, and zonal subpopulations were separately expanded in 2-dimensional culture. At passage 2, superficial and deep zone chondrocytes were seeded, separately, in scaffold-free 3-dimensional culture within agarose wells and cultured in redifferentiation media.

RESULTS

Monolayer expansion resulted in loss of expression for proteoglycan-4 and collagen type X in passaged superficial and deep zone chondrocytes, respectively. By passage 2, superficial and deep zone chondrocytes had similar expression for dedifferentiated molecules collagen type I and tenascin C. Redifferentiation of both superficial and deep zone chondrocytes led to the expression of collagen type II and aggrecan in both passaged chondrocyte populations. However, only redifferentiated deep zone chondrocytes expressed collagen type X, and only redifferentiated superficial zone chondrocytes expressed and secreted proteoglycan-4. Additionally, redifferentiated deep zone chondrocytes produced a thicker and more robust tissue compared with superficial zone chondrocytes.

CONCLUSION

The recapitulation of the primary phenotype from passaged zonal chondrocytes introduces a novel method of functional bioengineering of cartilage that resembles the zone-specific biological properties of native cartilage.

CLINICAL RELEVANCE

The recapitulation of the primary phenotype in zonal chondrocytes could be a possible method to tailor bioengineered cartilage to have zone-specific expression.

Deciphering the fibrotic process: mechanism of chronic radiation skin injury fibrosis

This review explores the mechanisms of chronic radiation-induced skin injury fibrosis, focusing on the transition from acute radiation damage to a chronic fibrotic state. It reviewed the cellular and molecular responses of the skin to radiation, highlighting the role of myofibroblasts and the significant impact of Transforming Growth Factor-beta (TGF-β) in promoting fibroblast-to-myofibroblast transformation. The review delves into the epigenetic regulation of fibrotic gene expression, the contribution of extracellular matrix proteins to the fibrotic microenvironment, and the regulation of the immune system in the context of fibrosis. Additionally, it discusses the potential of biomaterials and artificial intelligence in medical research to advance the understanding and treatment of radiation-induced skin fibrosis, suggesting future directions involving bioinformatics and personalized therapeutic strategies to enhance patient quality of life.

Single Injection AAV2-FGF18 Gene Therapy Reduces Cartilage Loss and Subchondral Bone Damage in a Mechanically Induced Model of Osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a highly debilitating, degenerative pathology of cartilaginous joints affecting over 500 million people worldwide. The global economic burden of OA is estimated at $260-519 billion and growing, driven by aging global population and increasing rates of obesity. To date, only the multi-injection chondroanabolic treatment regimen of Fibroblast Growth Factor 18 (FGF18) has demonstrated clinically meaningful disease-modifying efficacy in placebo-controlled human trials. Our work focuses on the development of a novel single injection disease-modifying gene therapy, based on FGF18's chondroanabolic activity.

METHODS

OA was induced in Sprague-Dawley rats using destabilization of the medial meniscus (DMM) (3 weeks), followed by intra-articular treatment with 3 dose levels of AAV2-FGF18, rh- FGF18 protein, and PBS. Durability, redosability, and biodistribution were measured by quantifying nLuc reporter bioluminescence. Transcriptomic analysis was performed by RNA-seq on cultured human chondrocytes and rat knee joints. Morphological analysis was performed on knee joints stained with Safranin O/Fast Green and anti-PRG antibody.

RESULTS

Dose-dependent reductions in cartilage defect size were observed in the AAV2-FGF18- treated joints relative to the vehicle control. Total defect width was reduced by up to 76% and cartilage thickness in the thinnest zone was increased by up to 106%. Morphologically, the vehicle- treated joints exhibited pronounced degeneration, ranging from severe cartilage erosion and bone void formation, to subchondral bone remodeling and near-complete subchondral bone collapse. In contrast, AAV2-FGF18-treated joints appeared more anatomically normal, with only regional glycosaminoglycan loss and marginal cartilage erosion. While effective at reducing cartilage lesions, treatment with rhFGF18 injections resulted in significant joint swelling (19% increase in diameter), as well as a decrease in PRG4 staining uniformity and intensity. In contrast to early-timepoint in vitro RNA-seq analysis, which showed a high degree of concordance between protein- and gene therapy-treated chondrocytes, in vivo transcriptomic analysis, revealed few gene expression changes following protein treatment. On the other hand, the gene therapy treatment exhibited a high degree of durability and localization over the study period, upregulating several chondroanabolic genes while downregulating OA- and fibrocartilage-associated markers.

CONCLUSION

FGF18 gene therapy treatment of OA joints can provide benefits to both cartilage and subchondral bone, with a high degree of localization and durability.

Cell Therapy Approaches for Articular Cartilage Regeneration

Articular cartilage is a common cartilage type found in a multitude of joints throughout the human body. However, cartilage is limited in its regenerative capacity. A range of methods have been employed to aid adults under the age of 45 with cartilage defects, but other cartilage pathologies such as osteoarthritis are limited to non-steroidal anti-inflammatory drugs and total joint arthroplasty. Cell therapies and synthetic biology can be utilized to assist not only cartilage defects but have the potential as a therapeutic approach for osteoarthritis as well. In this review, we will cover current cell therapy approaches for cartilage defect regeneration with a focus on autologous chondrocyte implantation and matrix autologous chondrocyte implantation. We will then discuss the potential of stem cells for cartilage repair in osteoarthritis and the use of synthetic biology to genetically engineer cells to promote cartilage regeneration and potentially reverse osteoarthritis.

The autologous chondral platelet-rich plasma matrix implantation. A new therapy in cartilage repair and regeneration: macroscopic and biomechanical study in an experimental sheep model

Introduction

Articular cartilage injuries are a severe problem, and the treatments for these injuries are complex. The present study investigates a treatment for full-thickness cartilage defects called Autologous Chondral Platelet Rich Plasma Matrix Implantation (PACI) in a sheep model.

Methods

Chondral defects 8 mm in diameter were surgically induced in the medial femoral condyles of both stifles in eight healthy sheep. Right stifles were treated with PACI and an intraarticular injection with a plasma rich in growth factors (PRGF) solution [treatment group (TRT)], while an intraarticular injection of Ringer's lactate solution was administered in left stifles [Control group (CT)]. The limbs' function was objectively assessed with a force platform to obtain the symmetry index, comparing both groups. After 9 and 18 months, the lesions were macroscopically evaluated using the International Cartilage Repair Society and Goebel scales.

Results

Regarding the symmetry index, the TRT group obtained results similar to those of healthy limbs at 9 and 18 months after treatment. Regarding the macroscopic assessment, the values obtained by the TRT group were very close to those of normal cartilage and superior to those obtained by the CT group at 9 months.

Conclusion

This new bioregenerative treatment modality can regenerate hyaline articular cartilage. High functional outcomes have been reported, together with a good quality repair tissue in sheep. Therefore, PACI treatment might be a good therapeutic option for full-thickness chondral lesions.

Gut microbiota in pre-clinical rheumatoid arthritis: From pathogenesis to preventing progression

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by progressive polyarthritis that leads to cartilage and bone damage. Pre-clinical RA is a prolonged state before clinical arthritis and RA develop, in which autoantibodies (antibodies against citrullinated proteins, rheumatoid factors) can be present due to the breakdown of immunologic self-tolerance. As early treatment initiation before the onset of polyarthritis may achieve sustained remission, optimize clinical outcomes, and even prevent RA progression, the pre-clinical RA stage is showing the prospect to be the window of opportunity for RA treatment. Growing evidence has shown the role of the gut microbiota in inducing systemic inflammation and polyarthritis via multiple mechanisms, which may involve molecular mimicry, impaired intestinal barrier function, gut microbiota-derived metabolites mediated immune regulation, modulation of the gut microbiota's effect on immune cells, intestinal epithelial cells autophagy, and the interaction between the microbiome and human leukocyte antigen alleles as well as microRNAs. Since gut microbiota alterations in pre-clinical RA have been reported, potential therapies for modifying the gut microbiota in pre-clinical RA, including natural products, antibiotic therapy, fecal microbiota transplantation, probiotics, microRNAs therapy, vitamin D supplementation, autophagy inducer-based treatment, prebiotics, and diet, holds great promise for the successful treatment and even prevention of RA via altering ongoing inflammation. In this review, we summarized current studies that include pathogenesis of gut microbiota in RA progression and promising therapeutic strategies to provide novel ideas for the management of pre-clinical RA and possibly preventing arthritis progression.

Bilayer osteochondral graft in rabbit xenogeneic transplantation model comprising sintered 3D-printed bioceramic and human adipose-derived stem cells laden biohydrogel

Reconstruction of severe osteochondral defects in articular cartilage and subchondral trabecular bone remains a challenging problem. The well-integrated bilayer osteochondral graft design expects to be guided the chondrogenic and osteogenic differentiation for stem cells and provides a promising solution for osteochondral tissue repair in this study. The subchondral bone scaffold approach is based on the developed finer and denser 3D β-tricalcium phosphate (β-TCP) bioceramic scaffold process, which is made using a digital light processing (DLP) technology and the novel photocurable negative thermo-responsive (NTR) bioceramic slurry. Then, the concave-top disc sintered 3D-printed bioceramic incorporates the human adipose-derived stem cells (hADSCs) laden photo-cured hybrid biohydrogel (HG + 0.5AFnSi) comprised of hyaluronic acid methacryloyl (HAMA), gelatin methacryloyl (GelMA), and 0.5% (w/v) acrylate-functionalized nano-silica (AFnSi) crosslinker. The 3D β-TCP bioceramic compartment is used to provide essential mechanical support for cartilage regeneration in the long term and slow biodegradation. However, the apparent density and compressive strength of the 3D β-TCP bioceramics can be obtained for ~ 94.8% theoretical density and 11.38 ± 1.72 MPa, respectively. In addition, the in vivo results demonstrated that the hADSC + HG + 0.5AFnSi/3D β-TCP of the bilayer osteochondral graft showed a much better osteochondral defect repair outcome in a rabbit model. The other word, the subchondral bone scaffold of 3D β-TCP bioceramic could accelerate the bone formation and integration with the adjacent host cancellous tissue at 12 weeks after surgery. And then, a thicker cartilage layer with a smooth surface and uniformly aligned chondrocytes were observed by providing enough steady mechanical support of the 3D β-TCP bioceramic scaffold.

Immunohistochemical Analysis of Knee Chondral Defect Repair after Autologous Particulated Cartilage and Platelet-Rich Plasma Treatment in Sheep

This study performs an analysis that will enable the evaluation of the quality, durability, and structure of repaired cartilaginous extracellular matrix tissue using an autologous-based particulated autograft cartilage and platelet-rich plasma treatment (PACI + PRP). A single-blind controlled experiment was conducted on 28 sheep to evaluate the efficacy of the PACI + PRP treatment for cartilage defects. Full-thickness 8 mm diameter defects were created in the weight-bearing area of both knees. The right knees received PACI + PRP. The left knees were treated with Ringer's lactate solution (RLS) or hyaluronic acid (HA) injections. Sheep were euthanized at 9- or 18-months post-surgery. An extensive immunohistochemical analysis was performed to assess collagen types (I, II, III, V, VI, IX, X, XI) and aggrecan positivity. A semiquantitative scoring system provided a detailed evaluation of immunostaining. Collagens and aggrecan scores in the PACI + PRP groups were similar to healthy cartilage. Significant differences were found in collagens associated with matrix maturity (II and V), degradation (IX), structure and mechanics (VI), and hypertrophy (X) between healthy cartilage and RLS- or HA-repaired cartilage. The PACI + PRP treatment advanced the repair cartilage process in chondral defects with mature hyaline cartilage and enhanced the structural and mechanical qualities with better consistent cartilage, less susceptible to degradation and without hypertrophic formation over time.

Characterization of Distinct Chondrogenic Cell Populations of Patients Suffering from Microtia Using Single-Cell Micro-Raman Spectroscopy

Microtia is a congenital condition of abnormal development of the outer ear. Tissue engineering of the ear is an alternative treatment option for microtia patients. However, for this approach, the identification of high regenerative cartilage progenitor cells is of vital importance. Raman analysis provides a novel, non-invasive, label-free diagnostic tool to detect distinctive biochemical features of single cells or tissues. Using micro-Raman spectroscopy, we were able to distinguish and characterize the particular molecular fingerprints of differentiated chondrocytes and perichondrocytes and their respective progenitors isolated from healthy individuals and microtia patients. We found that microtia chondrocytes exhibited lower lipid concentrations in comparison to healthy cells, thus indicating the importance of fat storage. Moreover, we suggest that collagen is a useful biomarker for distinguishing between populations obtained from the cartilage and perichondrium because of the higher spectral contributions of collagen in the chondrocytes compared to perichondrocytes from healthy individuals and microtia patients. Our results represent a contribution to the identification of cell markers that may allow the selection of specific cell populations for cartilage tissue engineering. Moreover, the observed differences between microtia and healthy cells are essential for gaining better knowledge of the cause of microtia. It can be useful for designing novel treatment options based on further investigations of the discovered biochemical substrate alterations.

Highly Biocompatible Smart Injectable Hydrogel for the Management of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease that severely affects joints and restricts locomotion. Various treatment regimens are available for RA, providing short-term relief from pain, but long-term relief from the disease is still not available. Evidently, cytokines play a crucial role in the pathophysiology of the disease. However, aberrant immune responses, genetic dispositions, viral infections, or toxicants are some possible causative mediators of RA. The synovial fluid of rheumatoid arthritis patients encompass cytokines, especially osteoclastogenic cytokines, and invasion factors such as macrophage colony-stimulating factor (M-CSF) and the receptor activator of NF-κB ligand (RANKL). Moreover, tumor necrosis factor-α (TNF-α) and interleukins (IL-1, 6, and 17) intensify osteoclast differentiation and activation. Therefore, in order to restrict the cytokine expression, we used budesonide as a therapeutic lead and encapsulated it into a highly biocompatible hydrogel system. The hydrogel system developed by us is enzyme-responsive and provides sustained drug release flow over an extended period of time. This hydrogel is characterized by ζ-potential analysis, field-emission scanning electron microscopy (FE-SEM), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and it is further encapsulated with budesonide (glucocorticoids) for therapeutic purposes. Evidently, Bud-loaded ER-hydrogel showed improvement in joint physiology compared to the disease group and downregulated the inflammatory markers.

Green biomanufacturing in recombinant collagen biosynthesis: trends and selection in various expression systems

Collagen, classically derived from animal tissue, is an all-important protein material widely used in biomedical materials, cosmetics, fodder, food, etc. The production of recombinant collagen through different biological expression systems using bioengineering techniques has attracted significant interest in consideration of increasing market demand and the process complexity of extraction. Green biomanufacturing of recombinant collagen has become one of the focus topics. While the bioproduction of recombinant collagens (type I, II, III, etc.) has been commercialized in recent years, the biosynthesis of recombinant collagen is extremely challenging due to protein immunogenicity, yield, degradation, and other issues. The rapid development of synthetic biology allows us to perform a heterologous expression of proteins in diverse expression systems, thus optimizing the production and bioactivities of recombinant collagen. This review describes the research progress in the bioproduction of recombinant collagen over the past two decades, focusing on different expression systems (prokaryotic organisms, yeasts, plants, insects, mammalian and human cells, etc.). We also discuss the challenges and future trends in developing market-competitive recombinant collagens.

Biomechanics of Chondrocytes and Chondrons in Healthy Conditions and Osteoarthritis: A Review of the Mechanical Characterisations at the Microscale

Biomechanical studies are expanding across a variety of fields, from biomedicine to biomedical engineering. From the molecular to the system level, mechanical stimuli are crucial regulators of the development of organs and tissues, their growth and related processes such as remodelling, regeneration or disease. When dealing with cell mechanics, various experimental techniques have been developed to analyse the passive response of cells; however, cell variability and the extraction process, complex experimental procedures and different models and assumptions may affect the resulting mechanical properties. For these purposes, this review was aimed at collecting the available literature focused on experimental chondrocyte and chondron biomechanics with direct connection to their biochemical functions and activities, in order to point out important information regarding the planning of an experimental test or a comparison with the available results. In particular, this review highlighted (i) the most common experimental techniques used, (ii) the results and models adopted by different authors, (iii) a critical perspective on features that could affect the results and finally (iv) the quantification of structural and mechanical changes due to a degenerative pathology such as osteoarthritis.

NIH/3T3 Fibroblasts Selectively Activate T Cells Specific for Posttranslationally Modified Collagen Type II

It has been shown that synovial fibroblasts (SF) play a key role in the initiation of inflammation and joint destruction, leading to arthritis progression. Fibroblasts may express major histocompatibility complex class II region (MHCII) molecules, and thus, they could be able to process and present antigens to immunocompetent cells. Here we examine whether different types of fibroblasts (synovial, dermal, and thymic murine fibroblasts, destructive LS48 fibroblasts, and noninvasive NIH/3T3 fibroblasts) may be involved in the initiation of rheumatoid arthritis (RA) pathogenesis and can process and present type II collagen (COL2)-an autoantigen associated with RA. Using a panel of MHCII/Aq-restricted T-cell hybridoma lines that specifically recognize an immunodominant COL2 epitope (COL2_259-273), we found that NIH/3T3 fibroblasts activate several T-cell clones that recognize the posttranslationally glycosylated or hydroxylated COL2_259-273 epitope. The HCQ.3 hybridoma, which is specific for the glycosylated immunodominant COL2 epitope 259-273 (Gal264), showed the strongest response. Interestingly, NIH/3T3 cells, but not destructive LS48 fibroblasts, synovial, dermal, or thymic fibroblasts, were able to stimulate the HCQ.3 hybridoma and other COL2-specific T-cell hybridomas. Our experiments revealed that NIH/3T3 fibroblasts are able to activate COL2-specific T-cell hybridomas even in the absence of COL2 or a posttranslationally modified COL2 peptide. The mechanism of this unusual activation is contact-dependent and involves the T-cell receptor (TCR) complex.

Proteoglycans in Articular Cartilage and Their Contribution to Chondral Injury and Repair Mechanisms

Proteoglycans are vital components of the extracellular matrix in articular cartilage, providing biomechanical properties crucial for its proper functioning. They are key players in chondral diseases, specifically in the degradation of the extracellular matrix. Evaluating proteoglycan molecules can serve as a biomarker for joint degradation in osteoarthritis patients, as well as assessing the quality of repaired tissue following different treatment strategies for chondral injuries. Despite ongoing research, understanding osteoarthritis and cartilage repair remains unclear, making the identification of key molecules essential for early diagnosis and effective treatment. This review offers an overview of proteoglycans as primary molecules in articular cartilage. It describes the various types of proteoglycans present in both healthy and damaged cartilage, highlighting their roles. Additionally, the review emphasizes the importance of assessing proteoglycans to evaluate the quality of repaired articular tissue. It concludes by providing a visual and narrative description of aggrecan distribution and presence in healthy cartilage. Proteoglycans, such as aggrecan, biglycan, decorin, perlecan, and versican, significantly contribute to maintaining the health of articular cartilage and the cartilage repair process. Therefore, studying these proteoglycans is vital for early diagnosis, evaluating the quality of repaired cartilage, and assessing treatment effectiveness.

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.

Ultrasound-assisted extraction of collagen from broiler chicken trachea and its biochemical characterization

Broiler chicken tracheas are a co-product from chicken slaughterhouses which are normally turned into low value animal feed despite their high levels of collagen. Typical collagen extraction by acid and/or pepsin usually results in relatively low yield. Ultrasound-assisted extraction (UAE) could be a means to improve collagen yield. The objectives of this study were to investigate the effects of ultrasonic parameters on the yield and biochemical properties of trachea collagen (TC). Conventional extraction using acetic acid and pepsin for 48 h resulted in acid-soluble (AS) and pepsin-soluble (PS) collagen with a yield of 0.65% and 3.10%, respectively. When an ultrasound with an intensity of 17.46 W·cm-2 was applied for 20 min, followed by acid extraction for 42 h (U-AS), the collagen yield increased to 1.58%. A yield of 6.28% was obtained when the ultrasound treatment was followed by pepsin for 36 h (U-PS). PS and U-PS contained collagen of 82.84% and 85.70%, respectively. Scanning electron microscopy images revealed that the ultrasound did not affect the collagen microstructure. All collagen samples showed an obvious triple helix structure as measured by circular dichroism spectroscopy. Fourier transform infrared spectroscopy indicated that the ultrasound did not disturb the secondary structure of the protein in which approximately 30% of the α-helix content was a major structure for all collagen samples. Micro-differential scanning calorimetry demonstrated that the denaturation temperature of collagen in the presence of deionized water was higher than collagen solubilized in 0.5 M acetic acid, regardless of the extraction method. All collagen comprised of α1 and α2-units with molecular weights of approximately 135 and 116 kDa, respectively, corresponding to the type I characteristic. PS and U-PS collagen possessed higher imino acids than their AS and U-AS counterparts. Based on LC-MS/MS peptide mapping, PS and U-PS collagen showed a high similarity to type I collagen. These results suggest that chicken tracheas are an alternative source of type I collagen. UAE is a promising technique that could increase collagen yield without damaging its structure.

The Matrix Reloaded-The Role of the Extracellular Matrix in Cancer

As the core component of all organs, the extracellular matrix (ECM) is an interlocking macromolecular meshwork of proteins, glycoproteins, and proteoglycans that provides mechanical support to cells and tissues. In cancer, the ECM can be remodelled in response to environmental cues, and it controls a plethora of cellular functions, including metabolism, cell polarity, migration, and proliferation, to sustain and support oncogenesis. The biophysical and biochemical properties of the ECM, such as its structural arrangement and being a reservoir for bioactive molecules, control several intra- and intercellular signalling pathways and induce cytoskeletal changes that alter cell shapes, behaviour, and viability. Desmoplasia is a major component of solid tumours. The abnormal deposition and composition of the tumour matrix lead to biochemical and biomechanical alterations that determine disease development and resistance to treatment. This review summarises the complex roles of ECM in cancer and highlights the possible therapeutic targets and how to potentially remodel the dysregulated ECM in the future. Furthering our understanding of the ECM in cancer is important as the modification of the ECM will probably become an important tool in the characterisation of individual tumours and personalised treatment options.

Bone and Cartilage Biology

Recent technical and conceptual advances in molecular and cellular biology have dramatically advanced bone and cartilage biology [...]

Fish scale containing alginate dialdehyde-gelatin bioink for bone tissue engineering

The development of biomaterial inks suitable for biofabrication and mimicking the physicochemical properties of the extracellular matrix is essential for the application of bioprinting technology in tissue engineering (TE). The use of animal-derived proteinous materials, such as jellyfish collagen, or fish scale (FS) gelatin (GEL), has become an important pillar in biomaterial ink design to increase the bioactivity of hydrogels. However, besides the extraction of proteinous structures, the use of structurally intact FS as an additive could increase biocompatibility and bioactivity of hydrogels due to its organic (collagen) and inorganic (hydroxyapatite) contents, while simultaneously enhancing mechanical strength in three-dimensional (3D) printing applications. To test this hypothesis, we present here a composite biomaterial ink composed of FS and alginate dialdehyde (ADA)-GEL for 3D bioprinting applications. We fabricate 3D cell-laden hydrogels using mouse pre-osteoblast MC3T3-E1 cells. We evaluate the physicochemical and mechanical properties of FS incorporated ADA-GEL biomaterial inks as well as the bioactivity and cytocompatibility of cell-laden hydrogels. Due to the distinctive collagen orientation of the FS, the compressive strength of the hydrogels significantly increased with increasing FS particle content. Addition of FS also provided a tool to tune hydrogel stiffness. FS particles were homogeneously incorporated into the hydrogels. Particle-matrix integration was confirmed via scanning electron microscopy. FS incorporation in the ADA-GEL matrix increased the osteogenic differentiation of MC3T3-E1 cells in comparison to pristine ADA-GEL, as FS incorporation led to increased ALP activity and osteocalcin secretion of MC3T3-E1 cells. Due to the significantly increased stiffness and supported osteoinductivity of the hydrogels, FS structure as a natural collagen and hydroxyapatite source contributed to the biomaterial ink properties for bone engineering applications. Our findings indicate that ADA-GEL/FS represents a new biomaterial ink formulation with great potential for 3D bioprinting, and FS is confirmed as a promising additive for bone TE applications.

Design of short peptides and peptide amphiphiles as collagen mimics and an investigation of their interactions with collagen using molecular dynamics simulations and docking studies

Short peptide sequences and bolaamphiphiles derived from natural proteins are gaining importance due to their ability to form unique nanoscale architectures for a variety of biological applications. In this work, we have designed six short peptides (triplet or monomeric forms) and two peptide bolaamphiphiles that either incorporate the bioactive collagen motif (Gly-X-Y) or sequences where Gly, Pro, or hydroxyproline (Hyp) are replaced by Ala or His. For the bolaamphiphiles, a malate moiety was used as the aliphatic linker for connecting His with Hyp to create collagen mimics. Stability of the assemblies was assessed through molecular dynamics simulations and results indicated that (Pro-Ala-His)₃ and (Ala-His-Hyp)₃ formed the most stable structures, while the amphiphiles and the monomers showed some disintegration over the course of the 200 ns simulation, though most regained structural integrity and formed fibrillar structures, and micelles by the end of the simulation, likely due to the formation of more thermodynamically stable conformations. Multiple replica simulations (REMD) were also conducted where the sequences were simulated at different temperatures. Our results showed excellent convergence in most cases compared to constant temperature molecular dynamics simulation. Furthermore, molecular docking and MD simulations of the sequences bound to collagen triple helix structure revealed that several of the sequences had a high binding affinity and formed stable complexes, particularly (Pro-Ala-His)₃ and (Ala-His-Hyp)₃. Thus, we have designed new hybrid-peptide-based sequences which may be developed for potential applications as biomaterials for tissue engineering or drug delivery.

Evaluating the Effect of Hypoxia on Human Adult Mesenchymal Stromal Cell Chondrogenesis In Vitro: A Systematic Review

Human adult mesenchymal stromal cells (MSCs) from a variety of sources may be used to repair defects in articular cartilage by inducing them into chondrogenic differentiation. The conditions in which optimal chondrogenic differentiation takes place are an area of interest in the field of tissue engineering. Chondrocytes exist in vivo in a normally hypoxic environment and thus it has been suggested that exposing MSCs to hypoxia may also contribute to a beneficial effect on their differentiation. There are two main stages in which MSCs can be exposed to hypoxia, the expansion phase when cells are cultured, and the differentiation phase when cells are induced with a chondrogenic medium. This systematic review sought to explore the effect of hypoxia at these two stages on human adult MSC chondrogenesis in vitro. A literature search was performed on PubMed, EMBASE, Medline via Ovid, and Cochrane, and 24 studies were ultimately included. The majority of these studies showed that hypoxia during the expansion phase or the differentiation phase enhances at least some markers of chondrogenic differentiation in adult MSCs. These results were not always demonstrated at the protein level and there were also conflicting reports. Studies evaluating continuous exposure to hypoxia during the expansion and differentiation phases also had mixed results. These inconsistent results can be explained by the heterogeneity of studies, including factors such as different sources of MSCs used, donor variability, level of hypoxia used in each study, time exposed to hypoxia, and differences in culture methodology.

3D in-vitro cultures of human bone marrow and Wharton’s jelly derived mesenchymal stromal cells show high chondrogenic potential

In this study, chondrogenic potentials of 3D high-density cultures of Bone Marrow (BM) and Wharton’s Jelly (WJ)-derived mesenchymal stromal cells (MSCs) was investigated by chondrogenesis- and cytokine-related gene expression over a 16-day culture period supplemented with human transforming growth factor (hTGF)-β1 at 10 ng/ml. In BM-MSC 3D models, a marked upregulation of chondrogenesis-related genes, such as SOX9, COL2A1, and ACAN (all p < 0.05) and formation of spherical pellets with structured type II collagen fibers were observed. Similarly, WJ-based high-density culture appeared higher in size and more regular in shape, with a significant overexpression of COL2A1 and ACAN (all p < 0.05) at day 16. Moreover, a similar upregulation trend was documented for IL-6 and IL-10 expression in both BM and WJ 3D systems. In conclusion, MSC-based high-density cultures can be considered a promising in vitro model of cartilage regeneration and tissue engineering. Moreover, our data support the use of WJ-MSCs as a valid alternative for chondrogenic commitment of stem cells in regenerative medicine.

Cellular responses in the FGF10-mediated improvement of hindlimb regenerative capacity in Xenopus laevis revealed by single-cell transcriptomics

Xenopus laevis tadpoles possess regenerative capacity in their hindlimb buds at early developmental stages (stages ~52-54); they can regenerate complete hindlimbs with digits after limb bud amputation. However, they gradually lose their regenerative capacity as metamorphosis proceeds. Tadpoles in late developmental stages regenerate fewer digits (stage ~56), or only form cartilaginous spike without digits or joints (stage ~58 or later) after amputation. Previous studies have shown that administration of fibroblast growth factor 10 (FGF10) in late-stage (stage 56) tadpole hindlimb buds after amputation can improve their regenerative capacity, which means that the cells responding to FGF10 signaling play an important role in limb bud regeneration. In this study, we performed single-cell RNA sequencing (scRNA-seq) of hindlimb buds that were amputated and administered FGF10 by implanting FGF10-soaked beads at a late stage (stage 56), and explored cell clusters exhibiting a differential gene expression pattern compared with that in controls treated with phosphate-buffered saline. The scRNA-seq data showed expansion of fgf8-expressing cells in the cluster of the apical epidermal cap of FGF10-treated hindlimb buds, which was reported previously, indicating that the administration of FGF10 was successful. On analysis, in addition to the epidermal cluster, a subset of myeloid cells and a newly identified cluster of steap4-expressing cells showed remarkable differences in their gene expression profiles between the FGF10- or phosphate-buffered saline-treatment conditions, suggesting a possible role of these clusters in improving the regenerative capacity of hindlimbs via FGF10 administration.