Cartilage contains mixed fibrils of collagen types II, IX, and XI

Highly oriented hydrogels for tissue regeneration: design strategies, cellular mechanisms, and biomedical applications

Many human tissues exhibit a highly oriented architecture that confers them with distinct mechanical properties, enabling adaptation to diverse and challenging environments. Hydrogels, with their water-rich "soft and wet" structure, have emerged as promising biomimetic materials in tissue engineering for repairing and replacing damaged tissues and organs. Highly oriented hydrogels can especially emulate the structural orientation found in human tissue, exhibiting unique physiological functions and properties absent in traditional homogeneous isotropic hydrogels. The design and preparation of highly oriented hydrogels involve strategies like including hydrogels with highly oriented nanofillers, polymer-chain networks, void channels, and microfabricated structures. Understanding the specific mechanism of action of how these highly oriented hydrogels affect cell behavior and their biological applications for repairing highly oriented tissues such as the cornea, skin, skeletal muscle, tendon, ligament, cartilage, bone, blood vessels, heart, etc., requires further exploration and generalization. Therefore, this review aims to fill that gap by focusing on the design strategy of highly oriented hydrogels and their application in the field of tissue engineering. Furthermore, we provide a detailed discussion on the application of highly oriented hydrogels in various tissues and organs and the mechanisms through which highly oriented structures influence cell behavior.

Investigating the interfaces of the epiphyseal plate: An integrated approach of histochemistry, microtomography and SEM

We investigated the interfaces of the epiphyseal plate with over- and underlying bone segments using an integrated approach of histochemistry, microtomography and scanning electron microscopy (SEM) to overcome the inherent limitations of sections-based techniques. Microtomography was able to provide an unobstructed, frontal view of large expanses of the two bone surfaces facing the growth plate, while SEM observation after removal of the soft matrix granted an equally unhindered access with a higher resolution. The two interfaces appeared widely dissimilar. On the diaphyseal side the hypertrophic chondrocytes were arranged in tall columns packed in a sort of compact palisade; the interposed extracellular matrix was actively calcifying into a thick mineralized crust growing towards the epiphysis. Behind the mineralization front, histochemical data revealed a number of surviving cartilage islets which were being slowly remodelled into bone. In contrast, the epiphyseal side of the cartilage consisted of a relatively quiescent reserve zone whose mineralization was marginal in amount and discontinuous in extension; the epiphyseal bone consisted of a loose trabecular meshwork, with ample vascular spaces opening directly into the non-mineralized cartilage. On both sides the calcification process took place through the formation of spheroidal bodies 1-2 μm wide which gradually grew by apposition and coalesced into a solid mass, in a way distinctly different from that of bone and other calcified tissues.

The chondro-osseous junction of articular cartilage

In the synovial joints the transition between the soft articular cartilage and the subchondral bone is mediated by a layer of calcified cartilage of structural and mechanical characteristics closer to those of bone. This layer, buried in the depth of articular cartilage, is not directly accessible and is mostly visualized in histological sections of decalcified tissue, where it appears as a darker strip in contact with the subchondral bone. In this study conventional histology and scanning electron microscopy (SEM) with secondary electron imaging (SE) or backscattered electron imaging (BSE) were used to discriminate the calcified and the uncalcified cartilage in high resolution on native, untreated tissue as well as in deproteinated or demineralized tissue. This approach evidenced a high heterogeneity of the calcified layer of articular cartilage. High resolution pictures revealed that the mineralization process originates by progressive accretion and confluence of individual, small mineral clusters, in a very different way from other hard tissues such as bone, dentin and mineralized tendons. Finally, selective removal of the soft matrix by thermal treatment allowed for the first time a face-on, unrestricted 3D view of the mineralization front.

Purification and Isolation of Proteins from Hyaline Cartilage

Proteins from hyaline or articular cartilage can be isolated and purified using a series of chemical extraction steps and various identification techniques including mass spectrometry and immunoblotting. The isolation and purification of proteins from cartilage will facilitate the study of specific proteins and multimeric complexes of cartilage proteins to better understand their functions in normal healthy cartilage as well as pathological conditions of cartilage. Cartilage tissue engineering efforts rely on the comprehensive understanding of the composition of cartilage and the function of each of the protein constituents.

Assessment of the COL9A1 Single Nucleotide Polymorphism with Severity of clubfoot in a paediatric population along with their biological mothers

Background

A frequent birth abnormality known as congenital talipes equinovarus (CTEV) results in severe abnormalities of one or both feet. The risk of CTEV has been shown to be significantly influenced by genetics. It is a typical congenital malformation. Diseases involving the articular cartilage and COL9A1 polymorphisms are linked.

Materials and method

This case parent dyad research was conducted in a premier care medical and educational facility by the Departments of Paediatric Orthopedics and Biochemistry. Children who had been diagnosed with clubfoot as well as their biological mothers took part in the study. 125 kids were able to join in the research when all the screening, inclusion, and exclusion criteria were met. Baseline demographic information was collected, including the child's age and sex, the kind of clubfoot, any family members who have the condition, and whether or not the mothers smoke or drink. Pirani score is used to clinically evaluate every case. Only one peripheral blood sample was taken from each patient, including their Biological Mothers.

Results

out of 125 children enrolled with biological mothers, Col9A1 SNP rs1135056 is substantially related.

Conclusion

Additionally, patients with the GG genotype for rs592121 have a higher chance of developing CTEV than those with other genotypes. In this investigation, we found possible associations between COL9A1 gene polymorphisms in the mother and offspring with the risk of CTEV. Our research may help us comprehend the genetic makeup of CTEV better and lay the groundwork for creative intervention strategies.

The Functional Role of Extracellular Matrix Proteins in Cancer

The extracellular matrix (ECM) is highly dynamic as it is constantly deposited, remodeled and degraded to maintain tissue homeostasis. ECM is a major structural component of the tumor microenvironment, and cancer development and progression require its extensive reorganization. Cancerized ECM is biochemically different in its composition and is stiffer compared to normal ECM. The abnormal ECM affects cancer progression by directly promoting cell proliferation, survival, migration and differentiation. The restructured extracellular matrix and its degradation fragments (matrikines) also modulate the signaling cascades mediated by the interaction with cell-surface receptors, deregulate the stromal cell behavior and lead to emergence of an oncogenic microenvironment. Here, we summarize the current state of understanding how the composition and structure of ECM changes during cancer progression. We also describe the functional role of key proteins, especially tenascin C and fibronectin, and signaling molecules involved in the formation of the tumor microenvironment, as well as the signaling pathways that they activate in cancer cells.

The effects of maturation and aging on the rotator cuff tendon-to-bone interface

Rotator cuff tendon injuries often occur at the tendon-to-bone interface (i.e., enthesis) area, with a high prevalence for the elderly population, but the underlying reason for this phenomenon is still unknown. The objective of this study is to identify the histological, molecular, and biomechanical alterations of the rotator cuff enthesis with maturation and aging in a mouse model. Four different age groups of mice (newborn, young, adult, and old) were studied. Striking variations of the entheses were observed between the newborn and other matured groups, with collagen content, proteoglycan deposition, collagen fiber dispersion was significantly higher in the newborn group. The compositional and histological features of young, adult, and old groups did not show significant differences, except having increased proteoglycan deposition and thinner collagen fibers at the insertion sites in the old group. Nanoindentation testing showed that the old group had a smaller compressive modulus at the insertion site when compared with other groups. However, tensile mechanical testing reported that the old group demonstrated a significantly higher failure stress when compared with the young and adult groups. The proteomics analysis detected dramatic differences in protein content between newborn and young groups but minor changes among young, adult, and old groups. These results demonstrated: (1) the significant alterations of the enthesis composition and structure occur from the newborn to the young time period; (2) the increased risk of rotator cuff tendon injuries in the elderly population is not solely because of old age alone in the rodent model.

Autophagy in Femoral Head Necrosis of Broilers Bone Metabolism Parameters and Autophagy-Related Gene Expression in Femoral Head Necrosis Induced by Glucocorticoid in Broilers

Objectives: In this study, the influence of methylprednisolone (MP) and 3-methyladenine (3-MA) on chondrocyte autophagy and bone quality were determined to investigate the mechanisms of femoral head necrosis in broilers.

Methods: Chickens were divided into four groups: control, MP, 3-MA, and 3-MA+MP groups. Blood and bone samples were collected for biochemistry assay and bone quality determination. Cartilage was separated from the femoral head for histopathological analysis and gene expression detection.

Results: The results indicated that MP treatment significantly affected blood levels of alkaline phosphatase, high-density lipoprotein, calcium, phosphorus, bone alkaline phosphatase, and osteocalcin in broilers. Additionally, MP treatment significantly increased blood levels of cholesterol, low-density lipoprotein, triglyceride, carboxy-terminal telopeptide of type-I collagen, and tartrate-resistant acid phosphatase 5. MP treatment also significantly decreased the levels of bone parameters compared with these values in controls, inhibited the expression of collagen-2, aggrecan, and mammalian target of rapamycin, and increased the expression of beclin1 and microtubule-associated protein 1 light chain 3, hypoxia-inducible factor 1 alpha, phosphoinositide 3-kinase, protein kinase B and autophagy-related gene 5 of the femoral head. Furthermore, following co-treatment with 3-MA and MP, 3-MA mitigated the effects of MP.

Conclusions: Our findings demonstrated that autophagy may be involved in the pathogenesis of femoral head necrosis induced by MP in broilers, and this study provides new treatment and prevention ideas for femoral head necrosis caused by glucocorticoids.

Biomimetic Approaches for the Design and Fabrication of Bone-to-Soft Tissue Interfaces

Bone-to-soft tissue interfaces are responsible for transferring loads between tissues with significantly dissimilar material properties. The examples of connective soft tissues are ligaments, tendons, and cartilages. Such natural tissue interfaces have unique microstructural properties and characteristics which avoid the abrupt transitions between two tissues and prevent formation of stress concentration at their connections. Here, we review some of the important characteristics of these natural interfaces. The native bone-to-soft tissue interfaces consist of several hierarchical levels which are formed in a highly specialized anisotropic fashion and are composed of different types of heterogeneously distributed cells. The characteristics of a natural interface can rely on two main design principles, namely by changing the local microarchitectural features (e.g., complex cell arrangements, and introducing interlocking mechanisms at the interfaces through various geometrical designs) and changing the local chemical compositions (e.g., a smooth and gradual transition in the level of mineralization). Implementing such design principles appears to be a promising approach that can be used in the design, reconstruction, and regeneration of engineered biomimetic tissue interfaces. Furthermore, prominent fabrication techniques such as additive manufacturing (AM) including 3D printing and electrospinning can be used to ease these implementation processes. Biomimetic interfaces have several biological applications, for example, to create synthetic scaffolds for osteochondral tissue repair.

Glucose Availability Affects Extracellular Matrix Synthesis During Chondrogenesis In Vitro

Understanding in vitro chondrogenesis of human mesenchymal stem cells (hMSCs) is important as it holds great promise for cartilage tissue engineering and other applications. The current technology produces the end tissue quality that is highly variable and dependent on culture conditions. We investigated the effect of nutrient availability on hMSC chondrogenesis in a static aggregate culture system by varying the medium-change frequency together with starting glucose levels. Glucose uptake and lactate secretion profiles were obtained to monitor the metabolism change during hMSC chondrogenesis with different culture conditions. Higher medium-change frequency led to increases in cumulative glucose uptake for all starting glucose levels. Furthermore, increase in glucose uptake by aggregates led to increased end tissue glycosaminoglycan (GAG) and hydroxyproline (HYP) content. The results suggest that increased glucose availability either through increased medium-change frequency or higher initial glucose levels lead to improved chondrogenesis. Also, cumulative glucose uptake and lactate secretion were found to correlate well with GAG and HYP content, indicating both molecules are promising biomarkers for noninvasive assessment of hMSC chondrogenesis. Collectively, our results can be used to design optimal culture conditions and develop dynamic assessment strategies for cartilage tissue engineering applications. Impact statement In this study, we investigated how culture conditions, medium-change frequency and glucose levels, affect chondrogenesis of human mesenchymal stem cells in an aggregate culture model. Doubling the medium-change frequency significantly increased the biochemical quality of the resultant tissue aggregates, as measured by their glycosaminoglycan and hydroxyproline content. We attribute this to increased glucose uptake through the glycolysis pathway, as secretion of lactate, a key endpoint product of the glycolysis pathway, increased concurrently. These findings can be used to design optimal culture conditions for tissue engineering and regenerative medicine applications.

Senescent Tissue-Resident Mesenchymal Stromal Cells Are an Internal Source of Inflammation in Human Osteoarthritic Cartilage

Human osteoarthritic cartilage contains not only chondrocytes (OACs), but also mesenchymal stromal cells (OA-MSCs), whose abundance increases during osteoarthritis (OA). However, it is not clear how OA-MSC contributes to OA pathogenesis. Here, we show that aging OA-MSC plays an important role in cell senescence, fibrosis, and inflammation in cartilage. Protein array analysis indicates that OA-MSC expresses pro-inflammatory senescence associated secretory phenotype (SASP) including IL-1β, IL-6, IL-8, and CXCL1, 5, and 6, which play key roles in OA pathogenesis. OAC is a main recipient of the inflammatory signals by expressing receptors of cytokines. RNAseq analysis indicates that the transition from normal cartilage stromal cells (NCSCs) to OA-MSC during aging results in activation of SASP gene expression. This cell transition process can be recapitulated by a serial passage of primary OAC in cell culture comprising (1) OAC dedifferentiation into NCSC-like cells, and (2) its subsequent senescence into pro-inflammatory OA-MSC. While OAC dedifferentiation is mediated by transcriptional repression of chondrogenic gene expression, OA-MSC senescence is mediated by transcriptional activation of SASP gene expression. We postulate that, through replication-driven OAC dedifferentiation and mesenchymal stromal cell (MSC) senescence, OA-MSC becomes an internal source of sterile inflammation in human cartilage joint.

Endoplasmic reticulum stress, chondrocyte apoptosis and oxidative stress in cartilage of broilers affected by spontaneous femoral head necrosis

With the promotion of the intensive breeding model, the incidence of leg diseases has risen in fast-growing commercial broilers with higher body weight, seriously affecting their feed efficiency and causing animal welfare problems. Femoral head necrosis (FHN) is the most common leg disease in broilers. Previous studies reported that hormone-induced FHN is related to endoplasmic reticulum (ER) stress, apoptosis, and oxidative stress, but no detailed study has been conducted in broilers with spontaneous FHN. In the study, the articular cartilage of 5-wk-old Ross 308 broilers with spontaneous FHN was used to investigate the pathogenesis of the disease. According to the degree of femoral head injury, the birds participating in the experiment were divided into 3 groups, namely a control group, femoral head separation group and femoral head separation with growth plate lacerations group. The morphological changes in articular cartilage were observed by hematoxylin and eosin, toluidine blue, alcian blue and safranine O-solid green staining, and the expressions of genes related to cartilage homeostasis, ER stress, autophagy, apoptosis and oxidative stress was detected using Real-Time Quantitative PCR. In the results, the expression of aggrecan and collagen-2 mRNA levels decreased in the articular cartilage of spontaneous FHN broilers, and the same changes were observed in the tissue staining results, indicating the disordered nature of articular cartilage homeostasis. At the same time, FHN in broilers causes ER stress in articular chondrocytes and regulates oxidative stress by activating the nuclear factor erythroid 2-related factor 2/antioxidant response element pathway through protein kinase RNA-like ER kinase. Autophagy can be activated through the protein kinase RNA-like ER kinase-activating transcription factor-4 pathway, and apoptosis can even be activated through CCAAT-enhancer-binding protein homologous protein. Therefore, the secretory activity of articular chondrocytes in spontaneous FHN broilers is negatively affected, which leads to the disorder of cartilage homeostasis and results in FHN due to ER-stress-mediated chondrocyte apoptosis and oxidative stress.

Polysaccharides on gelatin-based hydrogels differently affect chondrogenic differentiation of human mesenchymal stromal cells

Selection of feasible hybrid-hydrogels for best chondrogenic differentiation of human mesenchymal stromal cells (hMSCs) represents an important challenge in cartilage regeneration. In this study, three-dimensional hybrid hydrogels obtained by chemical crosslinking of poly (ethylene glycol) diglycidyl ether (PEGDGE), gelatin (G) without or with chitosan (Ch) or dextran (Dx) polysaccharides were developed. The hydrogels, namely G-PEG, G-PEG-Ch and G-PEG-Dx, were prepared with an innovative, versatile and cell-friendly technique that involves two preparation steps specifically chosen to increase the degree of crosslinking and the physical-mechanical stability of the product: a first homogeneous phase reaction followed by directional freezing, freeze-drying and post-curing. Chondrogenic differentiation of human bone marrow mesenchymal stromal cells (hBM-MSC) was tested on these hydrogels to ascertain whether the presence of different polysaccharides could favor the formation of the native cartilage structure. We demonstrated that the hydrogels exhibited an open pore porous morphology with high interconnectivity and the incorporation of Ch and Dx into the G-PEG common backbone determined a slightly reduced stiffness compared to that of G-PEG hydrogels. We demonstrated that G-PEG-Dx showed a significant increase of its anisotropic characteristic and G-PEG-Ch exhibited higher and faster stress relaxation behavior than the other hydrogels. These characteristics were associated to absence of chondrogenic differentiation on G-PEG-Dx scaffold and good chondrogenic differentiation on G-PEG and G-PEG-Ch. Furthermore, G-PEG-Ch induced the minor collagen proteins and the formation of collagen fibrils with a diameter like native cartilage. This study demonstrated that both anisotropic and stress relaxation characteristics of the hybrid hydrogels were important features directly influencing the chondrogenic differentiation potentiality of hBM-MSC.

Enhancing the chondrogenic potential of chondrogenic progenitor cells by deleting RAB5C

Osteoarthritis (OA) is the most prevalent chronic joint disease that affects a large proportion of the elderly population. Chondrogenic progenitor cells (CPCs) reside in late-stage OA cartilage tissue, producing a fibrocartilaginous extracellular matrix; these cells can be manipulated in vitro to deposit proteins of healthy articular cartilage. CPCs are under the control of SOX9 and RUNX2. In our earlier studies, we showed that a knockdown of RUNX2 enhanced the chondrogenic potential of CPCs. Here we demonstrate that CPCs carrying a knockout of RAB5C, a protein involved in endosomal trafficking, exhibited elevated expression of multiple chondrogenic markers, including the SOX trio, and increased COL2 deposition, whereas no changes in COL1 deposition were observed. We report RAB5C as an attractive target for future therapeutic approaches designed to increase the COL2 content in the diseased joint.

Slippery when wet: The free surface of the articular cartilage

The free surface of the articular cartilage must withstand compressive and shearing forces, maintain a low friction coefficient and allow oxygen and metabolites to reach the underlying matrix. In many ways it is critical to the physiology of the whole tissue and its disruption always involves deep pathological alterations and loss of the joint integrity. Being very difficult to image with section-based conventional techniques, it was often described by previous research in conflicting terms or entirely overlooked. High-magnification face-on observations with high resolution scanning electron microscopy and with scanning probe microscopy revealed a very thin, delicate superficial layer rich in glycoconjugates, which may explain the very low friction coefficient of the tissue but which was very easily altered and/or dissolved in the preparation. Beneath this superficial sheet lies a thicker coat of thin, highly uniform, slightly wavy collagen fibrils lying parallel to the surface and mutually interconnected by a huge number of interfibrillar glycosaminoglycan bridges. These bridges and the collagen fibrils form an extended reticular structure able to redistribute tensile and compressive stress across a larger area of the surface and hence a greater volume of tissue.

Combination Therapy Using Kartogenin-Based Chondrogenesis and Complex Polymer Scaffold for Cartilage Defect Regeneration

Articular cartilage has a highly organized structure, responsible for supporting tremendous mechanical loads. How to repair defected articular cartilage has become a great challenge as the avascular nature of cartilage limits its regenerative ability. Aiming to facilitate chondrogenic differentiation and cartilage regeneration, we recently explored a novel combination therapy using soluble poly-l-lysine/Kartogenin (L-K) nanoparticles and a poly(lactic-co-glycolic acid) PLGA/methacrylated hyaluronic acid (PLHA) complex scaffold. The potential use for joint cartilage reconstruction was investigated through L-K nanoparticles stimulating adipose-derived stem cells (ADSCs) on PLHA scaffolding, which ultimately differentiated into cartilage in vivo. In this study, on one hand, an effective method was established for obtaining uniform L-K nanoparticles by self-assembly. They were further proved to be biocompatible to ADSCs via cytotoxicity assays in vitro and to accelerate ADSCs secreting type 2 collagen in a dose-dependent manner by immunofluorescence. On the other hand, the porous PLHA scaffold was manufactured by the combination of coprecipitation and ultraviolet (UV) cross-linking. Nanoindentation technology-verified PLHA had an appropriate stiffness close to actual cartilage tissue. Additional microscopic observation confirmed that the PLHA platform supported proliferation and chondrogenesis for ADSCs in vitro. In the presence of ADSCs, a 12-week osteochondral defect regeneration by the combination therapy showed that smooth and intact cartilage tissue successfully regenerated. Furthermore, the results of combination therapy were superior to those of phosphate-buffered saline (PBS) only, KGN, or KGN/PLHA treatment. The results of magnetic resonance imaging (MRI) and histological assessment indicated that the renascent tissue gradually regenerated while the PLHA scaffold degraded. In conclusion, we have developed a novel multidimensional combination therapy of cartilage defect repair that facilitated cartilage regeneration. This strategy has a great clinical translational potential for articular cartilage repair in the near future.

Col11a1a Expression Is Required for Zebrafish Development

The autosomal dominant chondrodystrophies, the Stickler type 2 and Marshall syndromes, are characterized by facial abnormalities, vision deficits, hearing loss, and articular joint issues resulting from mutations in COL11A1. Zebrafish carry two copies of the Col11a1 gene, designated Col11a1a and Col11a1b. Col11a1a is located on zebrafish chromosome 24 and Col11a1b is located on zebrafish chromosome 2. Expression patterns are distinct for Col11a1a and Col11a1b and Col11a1a is most similar to COL11A1 that is responsible for human autosomal chondrodystrophies and the gene responsible for changes in the chondrodystrophic mouse model cho/cho. We investigated the function of Col11a1a in craniofacial and axial skeletal development in zebrafish using a knockdown approach. Knockdown revealed abnormalities in Meckel's cartilage, the otoliths, and overall body length. Similar phenotypes were observed using a CRISPR/Cas9 gene-editing approach, although the CRISPR/Cas9 effect was more severe compared to the transient effect of the antisense morpholino oligonucleotide treatment. The results of this study provide evidence that the zebrafish gene for Col11a1a is required for normal development and has similar functions to the mammalian COL11A1 gene. Due to its transparency, external fertilization, the Col11a1a knockdown, and knockout zebrafish model systems can, therefore, contribute to filling the gap in knowledge about early events during vertebrate skeletal development that are not as tenable in mammalian model systems and help us understand Col11a1-related early developmental events.

Tissue Engineering: An Alternative to Repair Cartilage

Herein we review the state-of-the-art in tissue engineering for repair of articular cartilage. First, we describe the molecular, cellular, and histologic structure and function of endogenous cartilage, focusing on chondrocytes, collagens, extracellular matrix, and proteoglycans. We then explore in vitro cell culture on scaffolds, discussing the difficulties involved in maintaining or obtaining a chondrocytic phenotype. Next, we discuss the diverse compounds and designs used for these scaffolds, including natural and synthetic biomaterials and porous, fibrous, and multilayer architectures. We then report on the mechanical properties of different cell-loaded scaffolds, and the success of these scaffolds following in vivo implantation in small animals, in terms of generating tissue that structurally and functionally resembles native tissue. Last, we highlight future trends in this field. We conclude that despite major technical advances made over the past 15 years, and continually improving results in cartilage repair experiments in animals, the development of clinically useful implants for regeneration of articular cartilage remains a challenge

Genetic variant of COL11A2 gene is functionally associated with developmental dysplasia of the hip in Chinese Han population

OBJECTIVES

Developmental dysplasia of the hip (DDH) is a common skeletal disorder. This study was conducted to demonstrate the association between DDH and a polymorphism rs9277935 of COL11A2 gene.

RESULTS

A significant difference in genotype distribution in a recessive model (TT+GT vs. GG) between two groups (P=0.017) was demonstrated. Analysis in female patients showed significantly greater frequency of minor allele G(0.49 vs. 0.43, p=0.024) and significantly higher distribution of GG genotype (p=0.006). DDH patients were found to have significantly lower COL11A2 expression than controls. Moreover, DDH patients with rs9277935 genotype TT have a significantly increased expression of COL11A2 than those with genotype GG. COL11A2 demonstrated chondrogenic properties in vitro.

CONCLUSION

Polymorphism rs9277935 of gene COL11A2 is a functional variant regulating the expression and the chondrogenic properties of COL11A2 in DDH in Chinese Han population.

METHODS

A case-control candidate gene association study was conducted in 945 patients (350 radiologically confirmed DDH patients and 595 healthy controls). Difference of COL11A2 expression in hip joint tissue was compared between the patients and the controls. Allelic difference in Col11a2 expression by rs9277935 was assessed with luciferase activity. Chondrogenic effects of Col11a2 signaling on BMSCs were also determined in vitro.

Molecular Insights Into Lysyl Oxidases in Cartilage Regeneration and Rejuvenation

Articular cartilage remains among the most difficult tissues to regenerate due to its poor self-repair capacity. The lysyl oxidase family (LOX; also termed as protein-lysine 6-oxidase), mainly consists of lysyl oxidase (LO) and lysyl oxidase-like 1-4 (LOXL1-LOXL4), has been traditionally defined as cuproenzymes that are essential for stabilization of extracellular matrix, particularly cross-linking of collagen and elastin. LOX is essential in the musculoskeletal system, particularly cartilage. LOXs-mediated collagen cross-links are essential for the functional integrity of articular cartilage. Appropriate modulation of the expression or activity of certain LOX members selectively may become potential promising strategy for cartilage repair. In the current review, we summarized the advances of LOX in cartilage homeostasis and functioning, as well as copper-mediated activation of LOX through hypoxia-responsive signaling axis during recent decades. Also, the molecular signaling network governing LOX expression has been summarized, indicating that appropriate modulation of hypoxia-responsive-signaling-directed LOX expression through manipulation of bioavailability of copper and oxygen is promising for further clinical implications of cartilage regeneration, which has emerged as a potential therapeutic approach for cartilage rejuvenation in tissue engineering and regenerative medicine. Therefore, targeted regulation of copper-mediated hypoxia-responsive signalling axis for selective modulation of LOX expression may become potential effective therapeutics for enhanced cartilage regeneration and rejuvenation in future clinical implications.

Analysis of Collagen-Binding Integrin Interactions with Supramolecular Aggregates of the Extracellular Matrix

Integrin-mediated interactions of cells with the extracellular matrix (ECM) are important for their activities. The ECM itself is a complex network of macromolecules forming aggregates or suprastructures. Moreover, the molecular composition is important for the macromolecular organization and, thereby, the functional properties of the ECM. In addition, collagen molecules lose their integrin-binding capabilities after incorporation into fibrils. Therefore, we have established detailed protocols for the analysis of integrin-matrix interactions at the supramolecular level.

Clinical, histopathological and genetic characterisation of oculoskeletal dysplasia in the Northern Inuit Dog

Seven Northern Inuit Dogs (NID) were diagnosed by pedigree analysis with an autosomal recessive inherited oculoskeletal dysplasia (OSD). Short-limbed dwarfism, angular limb deformities and a variable combination of macroglobus, cataracts, lens coloboma, microphakia and vitreopathy were present in all seven dogs, while retinal detachment was diagnosed in five dogs. Autosomal recessive OSD caused by COL9A3 and COL9A2 mutations have previously been identified in the Labrador Retriever (dwarfism with retinal dysplasia 1-drd1) and Samoyed dog (dwarfism with retinal dysplasia 2-drd2) respectively; both of those mutations were excluded in all affected NID. Nine candidate genes were screened in whole genome sequence data; only one variant was identified that was homozygous in two affected NID but absent in controls. This variant was a nonsense single nucleotide polymorphism in COL9A3 predicted to result in a premature termination codon and a truncated protein product. This variant was genotyped in a total of 1,232 dogs. All seven affected NID were homozygous for the variant allele (T/T), while 31/116 OSD-unaffected NID were heterozygous for the variant (C/T) and 85/116 were homozygous for the wildtype allele (C/C); indicating a significant association with OSD (p = 1.41x10-11). A subset of 56 NID unrelated at the parent level were analysed to determine an allele frequency of 0.08, estimating carrier and affected rates to be 15% and 0.6% respectively in NID. All 1,109 non-NID were C/C, suggesting the variant is rare or absent in other breeds. Expression of retinal mRNA was similar between an OSD-affected NID and OSD-unaffected non-NID. In conclusion, a nonsense variant in COL9A3 is strongly associated with OSD in NID, and appears to be widespread in this breed.

Expression of minor cartilage collagens and small leucine rich proteoglycans may be relatively reduced in osteoarthritic cartilage

Background

In osteoarthritis (OA), cartilage matrix is lost despite vigorous chondrocyte anabolism. In this study, we attempted to determine whether altered matrix synthesis is involved in this paradox in disease progression through gene expression analysis and ultrastructural analysis of collagen fibrils within the cartilage matrix.

Methods

Cartilage tissues were obtained from 29 end-stage OA knees and 11 control knees. First, cDNA microarray analysis was performed and the expression of 9 genes involved in collagen fibrillogenesis was compared between OA and control cartilages. Then their expression was investigated in further detail by a quantitative polymerase chain reaction (qPCR) analysis combined with laser capture microdissection. Finally, collagen fibril formation was compared between OA and control cartilage by transmission electron microscopy.

Results

The result of the microarray analysis suggested that the expression of type IX and type XI collagens and fibrillogenesis-related small leucine-rich proteoglycans (SLRPs) may be reduced in OA cartilage relative to the type II collagen expression. The qPCR analysis confirmed these results and further indicated that the relative reduction in the minor collagen and SLRP expression may be more obvious in degenerated areas of OA cartilage. An ultrastructural analysis suggested that thicker collagen fibrils may be formed by OA chondrocytes possibly through reduction in the minor collagen and SLRP expression.

Conclusions

This may be the first study to report the possibility of altered collagen fibrillogenesis in OA cartilage. Disturbance in collagen fibril formation may be a previously unidentified mechanism underlying the loss of cartilage matrix in OA.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2596-y) contains supplementary material, which is available to authorized users.

Non-Invasive Monitoring of Functional State of Articular Cartilage Tissue with Label-Free Unsupervised Hyperspectral Imaging

Damage and degradation of articular cartilage leads to severe pain and loss of mobility. The development of new therapies for cartilage regeneration for monitoring their effect requires further study of cartilage, ideally at a molecular level and in a minimally invasive way. Hyperspectral microscopy is a novel technology which utilises endogenous fluorophores to non-invasively assess the molecular composition of cells and tissue. In this study, we applied hyperspectral microscopy to healthy bovine articular cartilage and osteoarthritic human articular cartilage to investigate its capacity to generate informative molecular data and characterise disease state and treatment effects. We successfully demonstrated label-free fluorescence identification of collagen type I and II - isolated in cartilage here for the first time and the co-enzymes free NADH and FAD which together give the optical redox ratio that is an important measure of metabolic activity. The intracellular composition of chondrocytes was also examined. Differences were observed in the molecular ratios within the superficial and transitional zones of the articular cartilage which appeared to be influenced by disease state and treatment. These findings show that hyperspectral microscopy could be useful for investigating the molecular underpinnings of articular cartilage degradation and repair. As it is non-invasive and non-destructive, samples can be repeatedly assessed over time, enabling true time-course experiments with in-depth molecular data. Additionally, there is potential for the hyperspectral approach to be adapted for patient examination to allow the investigation of cartilage state. This could be of advantage for assessment and diagnosis as well as treatment monitoring.

Understanding chondrodysplasia (cho): A comprehensive review of cho as an animal model of birth defects, disorders, and molecular mechanisms

BACKGROUND

The mutant chondrodysplasia (cho) is a cartilage-targeting disorder in C57BL mice that results in dwarfing and other malformations stemming from this collagenopathy. Clarke Fraser made the discovery of the mutation accidentally in the early 1960s during the thalidomide tragedy.

METHODS

For this review we identified key research on cho as since its discovery. Relevant data were compiled to make a comprehensive review that details discoveries associated with the cho mutation, that describes the associated phenotypes and molecular mechanisms, and that provides a discussion surrounding its current clinical relevance.

RESULTS

Mechanistically, cho acts by hindering chondrogenesis and endochondral bone formation. The phenotype results from a 1-nt deletion in the gene encoding the alpha 1 chain of type XI collagen. For more than half a century, researchers have studied the pathogenesis of the cho mutation in relation to a variety of mouse models of human birth defects and disease. These studies have resulted in several discoveries linking cho with such human disorders as dwarfism, tracheal stenosis, cleft palate, pulmonary hypoplasia, and osteoarthritis (OA).

CONCLUSION

The study of cho has led to numerous advances in understanding human birth defects, congenital disorders, and adult human disease. The most recent studies have suggested a role for the TGF-Beta, HtrA1, Ddr2, and Mmp-13 pathway in the degradation of articular cartilage and the development of OA in cho/+ mice. We have shown that the anti-hypertension drug Losartan is a TGF-Beta blocker that could be used to treat OA in Stickler syndrome, and thereby rescue the WT phenotype.

Combination of bioactive factors and IEIK13 self-assembling peptide hydrogel promotes cartilage matrix production by human nasal chondrocytes

Nasal reconstruction remains a challenge for every reconstructive surgeon. Alloplastic implants are proposed to repair nasal cartilaginous defects but they are often associated with high rates of extrusion and infection and poor biocompatibility. In this context, a porous polymeric scaffold filled with an autologous cartilage gel would be advantageous. In this study, we evaluated the capacity of IEIK13 self-assembling peptide (SAP) to serve as support to form such cartilage gel. Human nasal chondrocytes (HNC) were first amplified with FGF-2 and insulin, and then redifferentiated in IEIK13 with BMP-2, insulin, and T3 (BIT). Our results demonstrate that IEIK13 fosters HNC growth and survival. HNC phenotype was assessed by RT-PCR analysis and neo-synthesized extracellular matrix was characterized by western blotting and immunohistochemistry analysis. BIT-treated cells embedded in IEIK13 displayed round morphology and expressed cartilage-specific markers such as type II and type IX collagens and aggrecan. In addition, we did not detect significant production of type I and type X collagens and gene products of dedifferentiated and hypertrophic chondrocytes that are unwanted in hyaline cartilage. The whole of these results indicates that the SAP IEIK13 represents a suitable support for hydrogel-based tissue engineering of nasal cartilage. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 893-903, 2019.

The mechanical impact of col11a2 loss on joints; col11a2 mutant zebrafish show changes to joint development and function, which leads to early-onset osteoarthritis

Collagen is the major structural component of cartilage, and mutations in the genes encoding type XI collagen are associated with severe skeletal dysplasias (fibrochondrogenesis and Stickler syndrome) and early-onset osteoarthritis (OA). The impact of the lack of type XI collagen on cell behaviour and mechanical performance during skeleton development is unknown. We studied a zebrafish mutant for col11a2 and evaluated cartilage, bone development and mechanical properties to address this. We show that in col11a2 mutants, type II collagen is made but is prematurely degraded in maturing cartilage and ectopically expressed in the joint. These changes are correlated with increased stiffness of both bone and cartilage; quantified using atomic force microscopy. In the mutants, the skeletal rudiment terminal region in the jaw joint is broader and the interzone smaller. These differences in shape and material properties impact on joint function and mechanical performance, which we modelled using finite element analyses. Finally, we show that col11a2 heterozygous carriers reach adulthood but show signs of severe early-onset OA. Taken together, our data demonstrate a key role for type XI collagen in maintaining the properties of cartilage matrix; which when lost leads to alterations to cell behaviour that give rise to joint pathologies.This article is part of the Theo Murphy meeting issue 'Mechanics of development'.

Recombinant Extracellular Matrix Protein Fragments Support Human Embryonic Stem Cell Chondrogenesis

We previously developed a 14-day culture protocol under potentially GMP, chemically defined conditions, to generate chondroprogenitors from human embryonic stem cells (hESCs). In vivo work has confirmed the cartilage repair capacity of these cells in a nude rat osteochondral defect model. Aiming to enhance hESC-chondrogenesis, we screened a range of extracellular matrix (ECM) molecules for their ability to support differentiation of hESCs toward chondrocytes. We identified two novel ECM protein fragments that supported hESC-chondrogenesis: Fibronectin III (fibronectin 7-14 protein fragments, including the RGD domain, syndecan-binding domain, and heparin-binding domain) and fibrillin-1 (FBN1) fragment PF8 (encoded by exons 30-38, residues 1238-1605, which contains the RGD motif but not heparin-binding site). These two protein fragments support hESC-chondrogenesis compared with the substrates routinely used previously (a mixture of fibronectin and gelatin) in our directed chondrogenic protocol. We have identified recombinant fibronectin fragment (FN III) and FBNI fragment (PF8) as alternative coating substrates to promote expression of genes known to regulate chondrocytes and code for chondrocyte ECM components. These recombinant protein fragments are likely to have better batch to batch stability than full-length molecules, especially where extracted from tissue/serum.

A Shared Epitope of Collagen Type XI and Type II Is Recognized by Pathogenic Antibodies in Mice and Humans with Arthritis

Background

Collagen XI (CXI) is a heterotrimeric molecule with triple helical structure in which the α3(XI) chain is identical to the α1(II) chain of collagen II (CII), but with extensive posttranslational modifications. CXI molecules are intermingled in the cartilage collagen fibers, which are mainly composed of CII. One of the alpha chains in CXI is shared with CII and contains the immunodominant T cell epitope, but it is unclear whether there are shared B cell epitopes as the antibodies tend to recognize the triple helical structures.

Methods

Mice expressing the susceptible immune response gene Aq were immunized with CII or CXI. Serum antibody responses were measured, monoclonal antibodies were isolated and analyzed for specificity to CII, CXI, and triple helical collagen peptides using bead-based multiplex immunoassays, enzyme-linked immunosorbent assays, and Western blots. Arthritogenicity of the antibodies was investigated by passive transfer experiments.

Results

Immunization with CII or CXI leads to a strong T and B cell response, including a cross-reactive response to both collagen types. Immunization with CII leads to severe arthritis in mice, with a response toward CXI at the chronic stage, whereas CXI immunization induces very mild arthritis only. A series of monoclonal antibodies to CXI were isolated and of these, the L10D9 antibody bound to both CXI and CII equally strong, with a specific binding for the D3 epitope region of α3(XI) or α1(II) chain. The L10D9 antibody binds cartilage in vivo and induced severe arthritis. In contrast, the L5F3 antibody only showed weak binding and L7D8 antibody has no binding to cartilage and did not induce arthritis. The arthritogenic L10D9 antibody bound to an epitope shared with CII, the triple helical D3 epitope. Antibody levels to the shared D3 epitope were elevated in the sera from mice with arthritis as well as in rheumatoid arthritis.

Conclusion

CXI is immunologically not exposed in healthy cartilage but contains T and B cell epitopes cross-reactive with CII, which could be activated in both mouse and human arthritis and could evoke an arthritogenic response.

A Human Chondrocyte-Derived In Vitro Model of Alcohol-Induced and Steroid-Induced Femoral Head Necrosis

BACKGROUND Worldwide, femoral head necrosis (FHN), which is also known as avascular necrosis of the femoral head or osteonecrosis of the femoral head, affects millions of people. Excess alcohol intake and steroid use are two common associations with FHN, but their pathogenesis remains unknown. The aim of this study was to develop an in vitro model using human chondrocytes to study alcohol-induced and steroid-induced FHN. MATERIAL AND METHODS In this study, the in vitro model used a monolayer culture of articular chondrocytes derived from patients with non-traumatic FHN (Ficat and Arlet, Stage III). Normal chondrocytes were obtained from patients with femoral neck fracture resulting from road traffic accident (Garden, Stage IV). Alcohol-stimulated and steroid-stimulated articular chondrocytes were evaluated by a cell proliferation assay, measurement of calcium levels (alizarin red), measurement of alkaline phosphatase (ALP) levels, detection of glycosaminoglycan (GAG) secretion using safranin O histochemical staining, and analysis of cartilage-specific genes, ACAN, SOX9, OPG, TGF-β, RANKL, and RUNX2, using quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS Both alcohol and steroids, but especially steroids, accelerated the degradation of cartilage by suppression of chondrogenesis while promoting chondrocyte hypertrophy and activating osteogenic differentiation, as assessed by cell proliferation assay, detection of glycosaminoglycan (GAG) secretion, and analysis of cartilage-specific genes. CONCLUSIONS A human chondrocyte-derived in vitro model of alcohol-induced and steroid-induced FHN demonstrated chondrocyte hypertrophy and activated osteogenic differentiation.

Hypoxia Is a Critical Parameter for Chondrogenic Differentiation of Human Umbilical Cord Blood Mesenchymal Stem Cells in Type I/III Collagen Sponges

Umbilical cord blood (UCB) is an attractive alternative to bone marrow for isolation of mesenchymal stem cells (MSCs) to treat articular cartilage defects. Here, we set out to determine the growth factors (bone morphogenetic protein 2 (BMP-2) and transforming growth factor-β (TGF-β1)) and oxygen tension effects during chondrogenesis of human UCB-MSCs for cartilage engineering. Chondrogenic differentiation was induced using 3D cultures in type I/III collagen sponges with chondrogenic factors in normoxia (21% O₂) or hypoxia (<5% O₂) for 7, 14 and 21 days. Our results show that UCB-MSCs can be committed to chondrogenesis in the presence of BMP-2+TGF-β1. Normoxia induced the highest levels of chondrocyte-specific markers. However, hypoxia exerted more benefit by decreasing collagen X and matrix metalloproteinase-13 (MMP13) expression, two chondrocyte hypertrophy markers. However, a better chondrogenesis was obtained by switching oxygen conditions, with seven days in normoxia followed by 14 days in hypoxia, since these conditions avoid hypertrophy of hUCB-MSC-derived chondrocytes while maintaining the expression of chondrocyte-specific markers observed in normoxia. Our study demonstrates that oxygen tension is a key factor for chondrogenesis and suggests that UBC-MSCs 3D-culture should begin in normoxia to obtain a more efficient chondrocyte differentiation before placing them in hypoxia for chondrocyte phenotype stabilization. UCB-MSCs are therefore a reliable source for cartilage engineering.

Characterization of the chondrocyte secretome in photoclickable poly(ethylene glycol) hydrogels

Poly(ethylene glycol) (PEG) hydrogels are highly tunable platforms that are promising cell delivery vehicles for chondrocytes and cartilage tissue engineering. In addition to characterizing the type of extracellular matrix (ECM) that forms, understanding the types of proteins that are secreted by encapsulated cells may be important. Thus, the objectives for this study were to characterize the secretome of chondrocytes encapsulated in PEG hydrogels and determine whether the secretome varies as a function of hydrogel stiffness and culture condition. Bovine chondrocytes were encapsulated in photoclickable PEG hydrogels with a compressive modulus of 8 and 46 kPa and cultured under free swelling or dynamic compressive loading conditions. Cartilage ECM deposition was assessed by biochemical assays and immunohistochemistry. The conditioned medium was analyzed by liquid chromatography-tandem mass spectrometry. Chondrocytes maintained their phenotype within the hydrogels and deposited cartilage-specific ECM that increased over time and included aggrecan and collagens II and VI. Analysis of the secretome revealed a total of 64 proteins, which were largely similar among all experimental conditions. The identified proteins have diverse functions such as biological regulation, response to stress, and collagen fibril organization. Notably, many of the proteins important to the assembly of a collagen-rich cartilage ECM were identified and included collagen types II(α1), VI (α1, α2, and α3), IX (α1), XI (α1 and α2), and biglycan. In addition, many of the other identified proteins have been reported to be present within cell-secreted exosomes. In summary, chondrocytes encapsulated within photoclickable PEG hydrogels secrete many types of proteins that diffuse out of the hydrogel and which have diverse functions, but which are largely preserved across different hydrogel culture environments. Biotechnol. Bioeng. 2017;114: 2096-2108. © 2017 Wiley Periodicals, Inc.

Endoplasmic Reticulum Stress and Unfolded Protein Response in Cartilage Pathophysiology; Contributing Factors to Apoptosis and Osteoarthritis

Chondrocytes of the growth plate undergo apoptosis during the process of endochondral ossification, as well as during the progression of osteoarthritis. Although the regulation of this process is not completely understood, alterations in the precisely orchestrated programmed cell death during development can have catastrophic results, as exemplified by several chondrodystrophies which are frequently accompanied by early onset osteoarthritis. Understanding the mechanisms that underlie chondrocyte apoptosis during endochondral ossification in the growth plate has the potential to impact the development of therapeutic applications for chondrodystrophies and associated early onset osteoarthritis. In recent years, several chondrodysplasias and collagenopathies have been recognized as protein-folding diseases that lead to endoplasmic reticulum stress, endoplasmic reticulum associated degradation, and the unfolded protein response. Under conditions of prolonged endoplasmic reticulum stress in which the protein folding load outweighs the folding capacity of the endoplasmic reticulum, cellular dysfunction and death often occur. However, unfolded protein response (UPR) signaling is also required for the normal maturation of chondrocytes and osteoblasts. Understanding how UPR signaling may contribute to cartilage pathophysiology is an essential step toward therapeutic modulation of skeletal disorders that lead to osteoarthritis.

The binding capacity of α1β1-, α2β1- and α10β1-integrins depends on non-collagenous surface macromolecules rather than the collagens in cartilage fibrils

Interactions of cells with supramolecular aggregates of the extracellular matrix (ECM) are mediated, in part, by cell surface receptors of the integrin family. These are important molecular components of cell surface-suprastructures regulating cellular activities in general. A subfamily of β1-integrins with von Willebrand-factor A-like domains (I-domains) in their α-chains can bind to collagen molecules and, therefore, are considered as important cellular mechano-receptors. Here we show that chondrocytes strongly bind to cartilage collagens in the form of individual triple helical molecules but very weakly to fibrils formed by the same molecules. We also find that chondrocyte integrins α1β1-, α2β1- and α10β1-integrins and their I-domains have the same characteristics. Nevertheless we find integrin binding to mechanically generated cartilage fibril fragments, which also comprise peripheral non-collagenous material. We conclude that cell adhesion results from binding of integrin-containing adhesion suprastructures to the non-collagenous fibril periphery but not to the collagenous fibril cores. The biological importance of the well-investigated recognition of collagen molecules by integrins is unknown. Possible scenarios may include fibrillogenesis, fibril degradation and/or phagocytosis, recruitment of cells to remodeling sites, or molecular signaling across cytoplasmic membranes. In these circumstances, collagen molecules may lack a fibrillar organization. However, other processes requiring robust biomechanical functions, such as fibril organization in tissues, cell division, adhesion, or migration, do not involve direct integrin-collagen interactions.

Spectral Unmixing Methods and Tools for the Detection and Quantitation of Collagen and Other Macromolecules in Tissue Specimens

Collagen and other components in the extracellular matrix are proving of increasing importance for the understanding of complex cell and tissue interactions in a variety of settings. Detection and quantitation of these components can still prove challenging, and a number of techniques have been developed. We focus here on methods in fluorescence-based assessments, including multiplexed immunodetection and the use of simpler histochemical stains, both complemented by linear unmixing techniques. Typically, differentiating these components requires the use of a set of optical filters to isolate each fluorescent compound from each other and from often bright background autofluorescence signals. However, standard fluorescent microscopes are usually only able to separate a limited number of components. If the emission spectra of the fluorophores are spectrally distinct, but overlapping, sophisticated spectral imaging or computational methods can be used to optimize separation and quantitation. This chapter describes spectral unmixing methodology and associated open-source software tools available to analyze multispectral as well as simple color (RGB) images.

Supramolecular Organization of Collagen Fibrils in Healthy and Osteoarthritic Human Knee and Hip Joint Cartilage

Cartilage matrix is a composite of discrete, but interacting suprastructures, i.e. cartilage fibers with microfibrillar or network-like aggregates and penetrating extrafibrillar proteoglycan matrix. The biomechanical function of the proteoglycan matrix and the collagen fibers are to absorb compressive and tensional loads, respectively. Here, we are focusing on the suprastructural organization of collagen fibrils and the degradation process of their hierarchical organized fiber architecture studied at high resolution at the authentic location within cartilage. We present electron micrographs of the collagenous cores of such fibers obtained by an improved protocol for scanning electron microscopy (SEM). Articular cartilages are permeated by small prototypic fibrils with a homogeneous diameter of 18 ± 5 nm that can align in their D-periodic pattern and merge into larger fibers by lateral association. Interestingly, these fibers have tissue-specific organizations in cartilage. They are twisted ropes in superficial regions of knee joints or assemble into parallel aligned cable-like structures in deeper regions of knee joint- or throughout hip joints articular cartilage. These novel observations contribute to an improved understanding of collagen fiber biogenesis, function, and homeostasis in hyaline cartilage.

Keratocytes are induced to produce collagen type II: A new strategy for in vivo corneal matrix regeneration

The stroma, the middle layer of the cornea, is a connective tissue making up most of the corneal thickness. The stromal extracellular matrix (ECM) consists of highly organised lamellae which are made up of tightly packed fibrils primarily composed of collagens type I and V. This layer is interspersed with keratocytes, mesenchymal cells of neural crest origin. We have previously shown that adult corneal keratocytes exhibit phenotypic plasticity and can be induced into a neuronal phenotype. In the current study we evaluated the potential of keratocytes to produce collagen type II via phenotypic reprogramming with exogenous chondrogenic factors. The cornea presents a challenge to tissue engineers owing to its high level of organisation and the phenotypic instability of keratocytes. Traditional approaches based on a scar model do not support the engineering of functional stromal tissue. Type II collagen is not found in the adult cornea but is reported to be expressed during corneal development, raising the possibility of using such an approach to regenerate the corneal ECM. Keratocytes in culture and within intact normal and diseased tissue were induced to produce collagen type II upon treatment with transforming growth factor Beta3 (TGFβ3) and dexamethasone. In vivo treatment of rat corneas also resulted in collagen type II deposition and a threefold increase in corneal hardness and elasticity. Furthermore, the treatment of corneas and subsequent deposition of collagen type II did not cause opacity, fibrosis or scarring. The induction of keratocytes with specific exogenous factors and resulting deposition of type II collagen in the stroma can potentially be controlled by withdrawal of the factors. This might be a promising new approach for in vivo corneal regeneration strategies aimed at increasing corneal integrity in diseases associated with weakened ectatic corneal tissue such as keratoconus.

Preserving the longevity of long-lived type II collagen and its implication for cartilage therapeutics

Human life expectancy has been steadily increasing at a rapid rate, but this increasing life span also brings about increases in diseases, dementia, and disability. A global burden of disease 2010 study revealed that hip and knee osteoarthritis ranked the 11th highest in terms of years lived with disability. Wear and tear can greatly influence the quality of life during ageing. In particular, wear and tear of the articular cartilage have adverse effects on joints and result in osteoarthritis. The articular cartilage uses longevity of type II collagen as the foundation around which turnover of proteoglycans and the homeostatic activity of chondrocytes play central roles thereby maintaining the function of articular cartilage in the ageing. The longevity of type II collagen involves a complex interaction of the scaffolding needs of the cartilage and its biochemical, structural and mechanical characteristics. The covalent cross-linking of heterotypic polymers of collagens type II, type IX and type XI hold together cartilage, allowing it to withstand ageing stresses. Discerning the biological clues in the armamentarium for preserving cartilage appears to be collagen cross-linking. Therapeutic methods to crosslink in in-vivo are non-existent. However intra-articular injections of polyphenols in vivo stabilize the cartilage and make it resistant to degradation, opening a new therapeutic possibility for prevention and intervention of cartilage degradation in osteoarthritis of aging.

BMP1-like proteinases are essential to the structure and wound healing of skin

Closely related extracellular metalloproteinases bone morphogenetic protein 1 (BMP1) and mammalian Tolloid-like 1 (mTLL1) are co-expressed in various tissues and have been suggested to have overlapping roles in the biosynthetic processing of extracellular matrix components. Early lethality of mice null for the BMP1 gene Bmp1 or the mTLL1 gene Tll1 has impaired in vivo studies of these proteinases. To overcome issues of early lethality and functional redundancy we developed the novel BT^KO mouse strain, with floxed Bmp1 and Tll1 alleles, for induction of postnatal, simultaneous ablation of the two genes. We previously showed these mice to have a skeletal phenotype that includes elements of osteogenesis imperfecta (OI), osteomalacia, and deficient osteocyte maturation, observations validated by the finding of BMP1 mutations in a subset of human patients with OI-like phenotypes. However, the roles of BMP1-like proteinase in non-skeletal tissues have yet to be explored, despite the supposed importance of putative substrates of these proteinases in such tissues. Here, we employ BT^KO mice to investigate potential roles for these proteinases in skin. Loss of BMP1-like proteinase activity is shown to result in markedly thinned and fragile skin with unusually densely packed collagen fibrils and delayed wound healing. We demonstrate deficits in the processing of collagens I and III, decorin, biglycan, and laminin 332 in skin, which indicate mechanisms whereby BMP1-like proteinases affect the biology of this tissue. In contrast, lack of effects on collagen VII processing or deposition indicates this putative substrate to be biosynthetically processed by non-BMP1-like proteinases.

Adeno-associated virus gene therapy vector scAAVIGF-I for transduction of equine articular chondrocytes and RNA-seq analysis

OBJECTIVE

IGF-I is one of several anabolic factors being investigated for the treatment of osteoarthritis (OA). Due to the short biological half-life, extended administration is required for more robust cartilage healing. Here we create a self-complimentary adeno-associated virus (AAV) gene therapy vector utilizing the transgene for IGF-I.

DESIGN

Various biochemical assays were performed to investigate the cellular response to scAAVIGF-I treatment vs an scAAVGFP positive transduction control and a negative for transduction control culture. RNA-sequencing analysis was also performed to establish a differential regulation profile of scAAVIGF-I transduced chondrocytes.

RESULTS

Biochemical analyses indicated an average media IGF-I concentration of 608 ng/ml in the scAAVIGF-I transduced chondrocytes. This increase in IGF-I led to increased expression of collagen type II and aggrecan and increased protein concentrations of cellular collagen type II and media glycosaminoglycan vs both controls. RNA-seq revealed a global regulatory pattern consisting of 113 differentially regulated GO categories including those for chondrocyte and cartilage development and regulation of apoptosis.

CONCLUSIONS

This research substantiates that scAAVIGF-I gene therapy vector increased production of IGF-I to clinically relevant levels with a biological response by chondrocytes conducive to increased cartilage healing. The RNA-seq further established a set of differentially expressed genes and gene ontologies induced by the scAAVIGF-I vector while controlling for AAV infection. This dataset provides a static representation of the cellular transcriptome that, while only consisting of one time point, will allow for further gene expression analyses to compare additional cartilage healing therapeutics or a transient cellular response.

Overexpression of α1 chain of type XI collagen (COL11A1) aids in the diagnosis of invasive carcinoma in endoscopically removed malignant colorectal polyps

INTRODUCTION

The histologic distinction between benign misplaced adenomatous mucosa and invasive adenocarcinoma in colorectal polyps can be challenging. The α1 chain of type XI collagen (COL11A1) has been shown to be overexpressed in cancer-associated stromal fibroblasts. The aim of this study was to investigate the operating characteristics of COL11A1 immunostaining in benign and malignant colorectal polyps as a potential diagnostic aid.

MATERIALS AND METHODS

Sixty-six endoscopically-removed paraffin-embedded colorectal polyps were stained with anti-COL11A1 antibody. They comprised 50 malignant polyps (MPs) with invasive adenocarcinoma (including 5 with concurrent benign misplaced adenomatous mucosa) and 16 adenomas, 11 with and 5 without benign misplaced adenomatous mucosa.

RESULTS

COL11A1 was expressed either diffusely or focally in cancer-associated desmoplastic fibroblasts in 72.0% (36/50) of MPs. The rates of COL11A1 expression and the immunohistochemical staining patterns of the COL11A1 were positively correlated with the depth of cancer invasion in MPs. COL11A1 was expressed in all 9 (100%) MPs with a mucinous component and in 16/18 (88.9%) MPs associated with significant electrocautery effects. COL11A1 was not expressed adjacent to conventional adenomas or in the stroma adjacent to misplaced adenomatous mucosa.

CONCLUSIONS

COL11A1 antibody can assist in distinguishing the cancer-associated desmoplastic stroma from that associated with misplaced adenomatous mucosa. It is particularly helpful when electrocautery artifacts or mucin pools interfere with the diagnosis of invasive carcinoma. However, COL11A1 has limited value in diagnosing superfically invasive carcinomas with very little desmoplastic stroma due to its low positive rate and focal expression in some cases.

Elucidating the Molecular Composition of Cartilage by Proteomics

Articular cartilage consists of chondrocytes and two major components, a collagen-rich framework and highly abundant proteoglycans. Most prior studies defining the zonal distribution of cartilage have extracted proteins with guanidine-HCl. However, an unextracted collagen-rich residual is left after extraction. In addition, the high abundance of anionic polysaccharide molecules extracted from cartilage adversely affects the chromatographic separation. In this study, we established a method for removing chondrocytes from cartilage sections with minimal extracellular matrix protein loss. The addition of surfactant to guanidine-HCl extraction buffer improved protein solubility. Ultrafiltration removed interference from polysaccharides and salts. Almost four-times more collagen peptides were extracted by the in situ trypsin digestion method. However, as expected, proteoglycans were more abundant within the guanidine-HCl extraction. These different methods were used to extract cartilage sections from different cartilage layers (superficial, intermediate, and deep), joint types (knee and hip), and disease states (healthy and osteoarthritic), and the extractions were evaluated by quantitative and qualitative proteomic analyses. The results of this study led to the identifications of the potential biomarkers of osteoarthritis (OA), OA progression, and the joint specific biomarkers.