Articular Cartilage Formation Research Articles

Stiffness Matters: Fine-Tuned Hydrogel Elasticity Alters Chondrogenic Redifferentiation.

Biomechanical cues such as shear stress, stretching, compression, and matrix elasticity are vital in the establishment of next generation physiological in vitro tissue models. Matrix elasticity, for instance, is known to guide stem cell differentiation, influence healing processes and modulate extracellular matrix (ECM) deposition needed for tissue development and maintenance. To better understand the biomechanical effect of matrix elasticity on the formation of articular cartilage analogs in vitro, this study aims at assessing the redifferentiation capacity of primary human chondrocytes in three different hydrogel matrices of predefined matrix elasticities. The hydrogel elasticities were chosen to represent a broad spectrum of tissue stiffness ranging from very soft tissues with a Young’s modulus of 1 kPa up to elasticities of 30 kPa, representative of the perichondral-space. In addition, the interplay of matrix elasticity and transforming growth factor beta-3 (TGF-β3) on the redifferentiation of primary human articular chondrocytes was studied by analyzing both qualitative (viability, morphology, histology) and quantitative (RT-qPCR, sGAG, DNA) parameters, crucial to the chondrotypic phenotype. Results show that fibrin hydrogels of 30 kPa Young’s modulus best guide chondrocyte redifferentiation resulting in a native-like morphology as well as induces the synthesis of physiologic ECM constituents such as glycosaminoglycans (sGAG) and collagen type II. This comprehensive study sheds light onto the mechanobiological impact of matrix elasticity on formation and maintenance of articular cartilage and thus represents a major step toward meeting the need for advanced in vitro tissue models to study both re- and degeneration of articular cartilage.

Theobromine mitigates IL-1β-induced oxidative stress, inflammatory response, and degradation of type II collagen in human chondrocytes

Osteoarthritis is one of the major causes of disability in elderly adults. Chondrocytes are responsible for the formation and remodeling of articular cartilage in joint tissue. The dysfunction of chondrocytes is a significant factor in the development of osteoarthritis. In the current study, we found that theobromine, a constituent of the cacao plant, possesses a preventive effect against interleukin (IL)-1β-induced chondrocyte dysfunction. Theobromine ameliorates IL-1β-induced production of cellular reactive oxygen species (ROS) and inflammatory mediators including cyclooxygenase-2 (COX-2) and prostaglandin E2 (PGE2). The presence of theobromine suppresses IL-1β-induced inducible nitro oxide synthase (iNOS) expression and cellular nitro oxide (NO) production. Theobromine also suppresses IL-1β-induced production of the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1), as well as matrix metalloproteinases (MMP)-3 and MMP-13. Additionally, theobromine mitigates IL-1β-induced type II collagen degradation. Mechanistically, we show that theobromine inhibits IL-1β-induced IκBα activation, nuclear factor-κB (NF-κB) protein p65 accumulation, and transfected NF-κB promoter activity, indicating that theobromine suppresses the NF-κB pathway in chondrocytes. Collectively, our study demonstrates that the natural molecule theobromine has a protective effect to counter cytokine-induced chondrocyte dysfunction, implying its beneficial effect in the prevention of osteoarthritis.

The efficacy of intraarticular PRP, ozone and PRP + ozone injections in patients with osteoarthritis [abstract

BACKGROUND: Osteoarthritis (OA) is the most common form of arthritis and some joints are predisposed more than others. The prevalence of OA increases with age and it represents the major problem for functional impairment in older patients.
 
 PURPOSE: This study was performed to determine efficiency of ozone + PRP (platelet rich plasma) injections on pain in patients with knee osteoarthritis.
 
 MATERIAL and METHODS: 102 patients with the diagnosis of OA according to the criteria of the American College of Rheumatology were enrolled in this study. Patients were randomized into three equal groups (34 patients each group).
 Patients in the first group were treated with intra-articular injections of ozone 2 times/week, with 10 ?g/ml ozone, 5ml in volume for a total of 12 times .
 Patients in the second group were treated with intra-articular injections of PRP + ozone (10 ?g/ml ozone, 5 ml volume) once a week for a total of 3 times.
 Patients in the third group were treated only with PRP injections once a week for a total of 3 times.
 The pain levels of patients were measured with visual analog scale (VAS).We chose the patients with VAS score 5 and above.
 The improvement strength has been evaluated according to Clinical Global image scale.
 
 RESULTS: In a retrospective study, Evaluation of the Clinical Global impression scale in the intra-articular injection of all patients (102 patients in total); 36 males and 66 females of 102 patients were found to have an average age of 56.11.
 The stress subscale of the 34 patients who had only ozone injections decreased from 5.17 to the healing scale of 2.91
 In the 34 patients who received Ozone + PRP combination, the stress subscale decreased from 5,.14 to the healing scale 1.52.
 In the 34 patients who had only PRP, the subscale of stress subscale decreased from 4.9 to the healing scale 1.85.
 When the mean recovery scores were evaluated, it was 2.26 in the ozone alone group, 3.62 in the ozone + PRP combination and 3.06 in the PRP patients only.
 The recovery scores of the patients who received the ozone + PRP combination were significantly better than ozone or PRP injections alone.
 No side effects were observed during and after the treatments.
 
 DISCUSSION: OA is a degenerative joint disease that increases with age and causes pain and disability to significantly impair an individual's quality of life.
 It is considered to be an organ disease that affects cartilage destruction and changes in the subchondral bone, and all the joints and tissues around the joint. Pathologically, destruction and loss of articular cartilage, subchondral sclerosis and osteophyte formation are often accompanied by synovial inflammation and destruction of other structures that support joint. The loss of pain and functioning impairs the patient to a wide variety of treatment seeking, but unfortunately there are no medical or physical methods that have proven scientifically and proven to be effective in humans to prevent joint cartilage degradation and therefore all treatment approaches are aimed at relieving symptomatic pain and minimizing functional deficits . The goal of treatment in knee OA should be to control pain, to preserve and correct joint functions, to provide functional independence and to improve quality of life. In order to achieve these goals, knee OA therapy should include non pharmacologic, pharmacologic and if necessary, surgical methods. Treatment should be tailored to each patient. Non-steroidal anti-inflammatory (NSAID) drugs are thought to be the standard treatment for OA in many cases but many patients are not able to tolerate these drugs or are exposed to side effects, while only analgesics are adequate in some patients.
 As we have seen in the study above; ozone or PRP injections alone can be used for the patients with knee OA but the results of Ozone + PRP injections in knee OA reduced the pain more than the ozone and PRP injections alone.
 This might be because of the anti inflammatory effect of ozone has been supported by the release of the growth factors from the platelets in PRP.
 Therefore we can add ozone + PRP injections to patients who has OA without hesitation in additional to the classical treatment .
 For further studies we can use Major Autohemotherapy for regeneration in addition to the injections of ozone, PRP, Ozone + PRP.
 
 CONCLUSION: The combination of ozone + PRP offers the best results compared with PRP or ozone alone.
 We could not get any biopsy from the cartilage so we could not show the healing or changes of the cartilage according to the decrease of pain and the increase of quality of life.
 For further studies we could include biopsy and the measurement of inflammatory and anti inflammatory markers from the cartilage tissue before and after treatment.

Linagliptin protects human chondrogenic ATDC5 cells against advanced glycation end products (AGEs)-induced apoptosis via a mitochondria-dependent pathway

Chondrocytes in joints are responsible for the formation and remodeling of articular cartilage. The accumulation of advanced glycation end products (AGEs) in cartilage is detrimental to the survival of chondrocytes. Linagliptin is one of the most commonly used anti-diabetes agents, and recent work indicates that it exerts an anti-inflammatory effect in different cell types. In this study, we showed that Linagliptin had a protective role in AGEs-induced chondrocyte injury. The presence of Linagliptin ameliorated AGEs-induced reactive oxygen species (ROS) induction and reduced cellular protein carboxyl content. Linagliptin mitigated AGEs-induced mitochondrial membrane potential (ΔΨm) reduction and NAPDH oxidase subunit NOX-4 induction, indicating that Linagliptin is a potent anti-ROS agent in chondrocytes. Additionally, Linagliptin inhibited AGEs-induced production of high mobility group box chromosomal protein 1 (HMGB-1), and the expression of matrix metalloproteases (MMPs)-2 and −9. Flow cytometry experimentation showed that Linagliptin inhibited AGEs-induced apoptotic subpopulation. Moreover, Linagliptin inhibited the AGEs-induced increased ratio of Bax to Bcl-2, translocation of cytochrome C from mitochondria to the cytoplasm, and release of cleaved caspase-3. Collectively, our data indicate that the anti-diabetes drug Linagliptin has a new role in rescuing chondrocyte from insult by AGEs, and may, therefore, have the potential to treat joint disorders.

Induction of Articular Chondrogenesis by Chitosan/Hyaluronic-Acid-Based Biomimetic Matrices Using Human Adipose-Derived Stem Cells.

Cartilage repair using tissue engineering is the most advanced clinical application in regenerative medicine, yet available solutions remain unsuccessful in reconstructing native cartilage in its proprietary form and function. Previous investigations have suggested that the combination of specific bioactive elements combined with a natural polymer could generate carrier matrices that enhance activities of seeded stem cells and possibly induce the desired matrix formation. The present study sought to clarify this by assessing whether a chitosan-hyaluronic-acid-based biomimetic matrix in conjunction with adipose-derived stem cells could support articular hyaline cartilage formation in relation to a standard chitosan-based construct. By assessing cellular development, matrix formation, and key gene/protein expressions during in vitro cultivation utilizing quantitative gene and immunofluorescent assays, results showed that chitosan with hyaluronic acid provides a suitable environment that supports stem cell differentiation towards cartilage matrix producing chondrocytes. However, on the molecular gene expression level, it has become apparent that, without combinations of morphogens, in the chondrogenic medium, hyaluronic acid with chitosan has a very limited capacity to stimulate and maintain stem cells in an articular chondrogenic state, suggesting that cocktails of various growth factors are one of the key features to regenerate articular cartilage, clinically.

CD271-selected mesenchymal stem cells from adipose tissue enhance cartilage repair and are less angiogenic than plastic adherent mesenchymal stem cells

CD271 is a marker of bone marrow MSCs with enhanced differentiation capacity for bone or cartilage repair. However, the nature of CD271+ MSCs from adipose tissue (AT) is less well understood. Here, we investigated the differentiation, wound healing and angiogenic capacity of plastic adherent MSCs (PA MSCs) versus CD271+ MSCs from AT. There was no difference in the extent to which PA MSCs and CD271+ MSCs formed osteoblasts, adipocytes or chondrocytes in vitro. In contrast, CD271+ MSCs transplanted into athymic rats significantly enhanced osteochondral wound healing with reduced vascularisation in the repair tissue compared to PA MSCs and control animals; there was little histological evidence of mature articular cartilage formation in all animals. Conditioned medium from CD271+ MSC cultures was less angiogenic than PA MSC conditioned medium, and had little effect on endothelial cell migration or endothelial tubule formation in vitro. The low angiogenic activity of CD271+ MSCs and improved early stage tissue repair of osteochondral lesions when transplanted, along with a comparable differentiation capacity along mesenchymal lineages when induced, suggests that these selected cells are a better candidate than PA MSCs for the repair of cartilaginous tissue.

Pharmacological Treatment of Pain in Osteoarthritis: A Descriptive Review.

Osteoarthritis (OA) is the most common form of arthritis that is characterized by loss of articular cartilage and new formation of bone. Pain and functional disability are common features that lead to disability and poor quality of life. This review discusses the current state of knowledge concerning the treatment of pain in OA, with a focus on pharmacological treatments. This includes the use of non-steroidal anti-inflammatory drugs, acetaminophen, and other disease-modifying agents. An updated review of the role of anti-nerve growth factor monoclonal antibodies and other novel agents in the treatment of OA is also presented. In addition, a discussion of current research on biological agents such as small molecules targeting ion channels and G protein-coupled receptors is included. These new pharmacological interventions expand the frontier for treatment of patients with OA. The purpose of the review is to provide clinicians with information about the effectiveness of different pharmacological modalities in order to enable them to make the best choices for the treatment of their patients.

Scaffold with Orientated Microtubule Structure Containing Polylysine-Heparin Sodium Nanoparticles for the Controlled Release of TGF-β1 in Cartilage Tissue Engineering.

Articular cartilage defects cannot adequately self-repair because of avascular and complex tissues. Although various scaffold materials have been reported to promote cartilage repair, challenges remain in this field. In the present study, an orientated microtubules scaffold that consisted of collagen, chitosan, silk fibroin, and polylysine-heparin sodium nanoparticles containing transforming growth factor β1 (TGF-β1), was constructed using a unidirectional freeze-drying method. The collagen/chitosan/0.5silk fibroin scaffolds showed optimal properties via the evaluation of physicochemical characterization, mechanical properties and biocompatibility. The collagen/chitosan/0.5silk fibroin scaffolds containing polylysine-heparin sodium nanoparticles loaded with TGF-β1 (COL/CS/0.5SF-TPHNs) could control the slow release of TGF-β1. Simultaneously, the in vitro COL/CS/0.5SF-TPHNs scaffolds exhibited not only an excellent biocompatibility to support mouse mesenchymal stem cells (mBMSCs) adhesion and proliferation, but also exhibited excellent repair effect in cartilage defects of rabbit models in vivo. Our results showed that the COL/CS/0.5SF-TPHNs scaffolds have the potential to induce articular cartilage formation, mainly because TGF-β1 could induce the mBMSCs to differentiate into chondrocytes and osteoblasts. Consequently, the current study can achieve cartilage repair, and COL/CS/0.5SF-TPHNs scaffolds are expected to be potential composites for cartilage tissue engineering.

Epigenetic dynamic during endochondral ossification and articular cartilage development.

Within the last decade epigenetics has emerged as fundamental regulator of numerous cellular processes, including those orchestrating embryonic and fetal development. As such, epigenetic factors play especially crucial roles in endochondral ossification, the process by which bone tissue is created, as well during articular cartilage formation. In this review, we summarize the recent discoveries that characterize how DNA methylation, histone post-translational modifications and non-coding RNA (e.g., miRNA and lcnRNA) epigenetically regulate endochondral ossification and chondrogenesis.

Bone Research Society Abstracts

Bone Research Society Abstracts

An Investigation on the Regenerative Effects of Intra Articular Injection of Co-Cultured Adipose Derived Stem Cells with Chondron for Treatment of Induced Osteoarthritis.

Purpose: Adipose tissue derived stem cells (ASCs) and chondrocytes are best cells for articular cartilage regeneration. Chondrocyte with peri-cellular matrix (PCM) is called chondron provides ideal microenviroment than chondrocytes. We aimed to evaluate the regenerative effects of intra-articular injection of ASCs co-cultures with chondron in induced osteoarthritis (OA).Methods: ASC, from the peri-renal fat of male rat and chondron from primary newborn rat hyaline cartilage were isolated. ASCs were cultured for at least three passages in vitro. Six weeks after OA induction, rats were randomly distributed in five groups of control, osteoarthritic, ASC, chondron and co-cultured. ASCs (107), chondrons (107) and combination of chondrons and ASCs (107) were injected into intra-articular space of the rat knee. The effect of treatments was evaluated by macroscopic and microscopic examinations. The expression levels of collagen type ΙΙ was studied by immunohistochemistry.Results: Macroscopic appearance of the co-cultured group, showed much enhanced articular cartilage regeneration compared to ASC and chondron groups. H&E showed evidence of repair site of articular surface without erosion and fibrillation versus OA group which showed thin layer of hyaline cartilage over tidemark and spontaneous fibrocartilage formation. Metachromatic regions stained with toluidine blue were larger in treatment groups versus OA group. Strong intensity of type ΙΙ collagen staining was observed in co-culture group compared to other groups.Conclusion: Co-culture of chondrons and ASCs increased articular hyaline cartilage formation and provides a useful tool to improve limitations of each of applied cells in this model.

A computational model for the joint onset and development

Joints connect the skeletal components and enable movement. The appearance and development of articulations is due to different genetic, biochemical, and mechanical factors. In the embryonic stage, controlled biochemical processes are critical for organized growth. We developed a computational model, which predicts the appearance, location, and development of joints in the embryonic stage. Biochemical events are modeled with reaction diffusion equations with generic molecules representing molecules that 1) determine the site where the articulation will appear, 2) promote proliferation, and matrix synthesis, and 3) define articular cartilage. Our model accounts for cell differentiation from mesenchymal cells to pre-cartilaginous cells, then cartilaginous cells, and lastly articular cartilage. These reaction-diffusion equations were solved using the finite elements method. From a mesenchymal ‘bud’ of a phalanx, the model predicts growth, joint cleavage, joint morphology, and articular cartilage formation. Our prediction of the gene expression during development agrees with molecular expression profiles of joint development reported in literature. Our computational model suggests that initial rudiment dimensions affect diffusion profiles result in Turing patterns that dictate sites of cleavage thereby determining the number of joints in a rudiment.

TPX-100 leads to marked, sustained improvements in subjects with knee osteoarthritis: pre-clinical rationale and results of a controlled clinical trial

Purpose: TPX-100 is a 23-amino acid peptide derived from Matrix Extracellular Phosphoglycoprotein (MEPE), a Small Integrin-Binding Ligand, N-linked Glycoprotein (SIBLING) family protein. TPX-100 has been shown to induce articular cartilage proliferation in goats (N = 8/ dose group) after a standardized full-thickness chondral defect and treatment with 4 weekly intra-articular (IA) injections of TPX-100 vs. vehicle (25, 125 or 250 mg/injection). After 6 months, histopathological staining in TPX-100-treated joints indicated robust articular (hyaline) cartilage formation. Additionally, IA TPX-100 reduced joint damage and improved osteoarthritis scores vs. vehicle in rats after standardized ACL transection and partial medial meniscectomy. This Phase 2 study evaluated safety, tolerability and preliminary efficacy of TPX-100 by IA administration in subjects with bilateral patellofemoral osteoarthritis (PFOA). Each subject served as his/her own control, intended to minimize effects of age, sex, genetic factors, and activity levels on outcome measures. Methods: Subjects with ICRS grade 2-3 PFOA, confirmed by centrally-read screening MRI, were enrolled at 15 sites. One knee was randomly assigned to receive 4 weekly injections of TPX-100, while the contralateral knee received placebo injections. Investigator, subject, site and sponsor were blinded to treatment assignment. In Part A of the study, 4 dose cohorts (n = 6–9 subjects/cohort) received 20, 50, 100 or 200 mg/injection. Safety/tolerability of each cohort was evaluated by a Safety Review Committee (SRC). In Part B, all subjects received 200 mg/injection. Quantitative MRIs, obtained at baseline, 6 and 12 months, were read centrally. Validated patient-reported outcomes (PROs) included the Knee Osteoarthritis Outcome Score (KOOS), appropriate for younger, more athletic subjects, and the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC). Results: All subjects who received 4 weekly 200 mg injections, with at least one follow-up MRI, were analyzed (n = 93 subjects, 186 knees). The study population was typical of the knee OA population in the U.S. (median age, 58.4 years; BMI 30.3), and 68 of 93 subjects (73%) also had ICRS grade 2 – 4 mild to severe bilateral tibio-femoral osteoarthritis (TFOA). Safety: There were no drug-related SAEs and no dose-limiting toxicities across doses. Common adverse events such as knee pain had virtually identical incidences in control and TPX-100-treated knees. Efficacy: Only 14% of knees changed in cartilage thickness/volume over the 12 months of the study. Quantitative MRI revealed no measurable between-knee structural differences in this small sample. However, statistically significant (P<0.05) and clinically meaningful differences in KOOS and WOMAC scores were demonstrated compared with placebo-exposed knees at 6 or 12 months or both, including activities of daily living, sports activities, and knee-related quality of life. Comparing TPX-100 treated knees vs. control knees, at 12 months; there was a significant difference in pain ascending and descending stairs, a chief complaint in PFOA. Overall, use of analgesics, including non-steroidal anti-inflammatory medications, declined markedly (62.5%) during the study. Conclusions: TPX-100, administered in 4 weekly intra-articular injections (200 mg/injection), is safe, well tolerated, and associated with statistically significant and clinically meaningful functional benefits sustained to at least 12 months. Improvement in knee functional status with reduction in disease burden represents a key therapeutic goal in OA therapeutic development. The small sample size of knees with MRI changes in cartilage thickness/volume limited the power of this study to detect differences between knees in these measures. However, pre-clinical large and small animal data indicate the structure-modifying potential of TPX-100, which may be demonstrated with a longer study involving a larger sample size.

Mesenchymal stromal cell lineages in synovium and their contribution to osteoarthritis and cartilage repair

In recent years, landmark studies using genetic lineage tracing models in mice have identified and functionally characterised skeletal stem and progenitor cell populations in bone marrow, providing important insights in the regulation of bone homeostasis and repair, as well as the control of haematopoiesis. By comparison, the stem and progenitor cells that are resident in the synovial joint and maintain and repair joint tissues such as articular cartilage remained poorly defined, but recent work from our lab and others is starting to shed light on this. Lineage tracing of progenitor cells in cartilage has provided important new insights into the process of articular cartilage formation and maintenance. Our work has focused on characterising stem and progenitor cells in the synovial membrane, and how these cells respond to cartilage injury. Tracing of cells from the embryonic joint interzone, using Gdf5 as driver, showed that Gdf5-lineage cells persist in adult knee synovium up to at least one year of age as a mesenchymal stromal cell population with progenitor activity, which is largely distinct from the skeletal stem/progenitor cell populations identified in bone marrow. After purification, Gdf5-lineage cells display a differentiation potency in vitro that is skewed towards formation of cartilage and a synovial lining-like layer, while showing poor osteogenic ability. Cartilage injury in vivo triggers Gdf5-lineage cells in synovium to undergo proliferation leading to synovial lining hyperplasia, a process that is dependent on the activity of the transcriptional co-factor Yap in these cells. Gdf5-lineage cells also contribute to repair of traumatic joint surface defects, though they do not seem to be the sole cell population able to populate the repair tissue. We further find that in pathology, using the destabilisation of the medial meniscus model of osteoarthritis, Gdf5-lineage cells contribute to chondro-osteophyte formation and subchondral bone remodeling. In conclusion, recent findings are starting to unravel distinct mesenchymal stromal cell subsets in the adult synovium, identifying the key players in joint pathophysiology and promising therapeutic targets for cartilage repair and treatment of osteoarthritis.

Euglena gracilis Z and its carbohydrate storage substance relieve arthritis symptoms by modulating Th17 immunity.

Euglena gracilis Z is a microorganism classified as a microalga and is used as a food or nutritional supplement. Paramylon, the carbohydrate storage substance of E. gracilis Z, is reported to affect the immunological system. This study evaluated the symptom-relieving effects of E. gracilis Z and paramylon in rheumatoid arthritis in a collagen-induced arthritis mouse model. The efficacy of both substances was assessed based on clinical arthritis signs, as well as cytokine (interleukin [IL]-17, IL-6, and interferon [IFN]-γ) levels in lymphoid tissues. Additionally, the knee joints were harvested and histopathologically examined. The results showed that both substances reduced the transitional changes in the visual assessment score of arthritis symptoms compared with those in the control group, indicating their symptom-relieving effects on rheumatoid arthritis. Furthermore, E. gracilis Z and paramylon significantly reduced the secretion of the cytokines, IL-17, IL-6, and IFN-γ. The histopathological examination of the control group revealed edema, inflammation, cell hyperplasia, granulation tissue formation, fibrosis, and exudate in the synovial membrane, as well as pannus formation and articular cartilage destruction in the femoral trochlear groove. These changes were suppressed in both treatment groups. Particularly, the E. gracilis Z group showed no edema, inflammation, and fibrosis of the synovial membrane, or pannus formation and destruction of articular cartilage in the femoral trochlear groove. Furthermore, E. gracilis Z and paramylon exhibited symptom-relieving effects on rheumatoid arthritis and suppressed the secretion of cytokines IL-17, IL-6, and IFN-γ. These effects were likely mediated by the regulatory activities of E. gracilis Z and paramylon on Th17 immunity. In addition, the symptom-relieving effects of both substances were comparable, which suggests that paramylon is the active component of Euglena gracilis Z.

Application of tissue engineering technology for formation of human articular cartilage in perfusion bioreactor

Formation of tissue-engineered construct was performed in a specially developed bioreactor. At first, a cellengineered construct of human cartilage tissue consisting of biopolymer microstructured collagen-containing hydrogel, mesenchymal stromal cells of human adipose tissue (hADMSCs) and induction chondrogenic culture medium was prepared and placed in a perfusion bioreactor. As a result, on the 16th day of the study hADMSCs obtain a flattened shape typical for chondroblasts and demonstrate high proliferative activity with the formation of their own extracellular matrix. Histological analysis of the cultured system indicates the beginning of the formation of a tissue-engineered construct of human cartilage tissue.

Oral administration of undenatured native chicken type II collagen (UC-II) diminished deterioration of articular cartilage in a rat model of osteoarthritis (OA).

The aim of this study was to determine the ability of undenatured native chicken type II collagen (UC-II) to prevent excessive articular cartilage deterioration in a rat model of osteoarthritis (OA). Twenty male rats were subjected to partial medial meniscectomy tear (PMMT) surgery to induce OA. Immediately after the surgery 10 rats received vehicle and another 10 rats oral daily dose of UC-II at 0.66mg/kg for a period of 8 weeks. In addition 10 naïve rats were used as an intact control and another 10 rats received sham surgery. Study endpoints included a weight-bearing capacity of front and hind legs, serum biomarkers of bone and cartilage metabolism, analyses of subchondral and cancellous bone at the tibial epiphysis and metaphysis, and cartilage pathology at the medial tibial plateau using histological methods. PMMT surgery produced moderate OA at the medial tibial plateau. Specifically, the deterioration of articular cartilage negatively impacted the weight bearing capacity of the operated limb. Immediate treatment with the UC-II preserved the weight-bearing capacity of the injured leg, preserved integrity of the cancellous bone at tibial metaphysis and limited the excessive osteophyte formation and deterioration of articular cartilage. Study results demonstrate that a clinically relevant daily dose of UC-II when applied immediately after injury can improve the mechanical function of the injured knee and prevent excessive deterioration of articular cartilage.

Selective laser sintering scaffold with hierarchical architecture and gradient composition for osteochondral repair in rabbits.

Osteochondral defects cannot be adequately self-repaired due to the presence of the sophisticated hierarchical structure and the lack of blood supply in cartilage. Thus, one of the major challenges remaining in this field is the structural design of a biomimetic scaffold that satisfies the specific requirements for osteochondral repair. To address this hurdle, a bio-inspired multilayer osteochondral scaffold that consisted of the poly(ε-caprolactone) (PCL) and the hydroxyapatite (HA)/PCL microspheres, was constructed via selective laser sintering (SLS) technique. The SLS-derived scaffolds exhibited an excellent biocompatibility to support cell adhesion and proliferation invitro. The repair effect was evaluated by implanting the acellular multilayer scaffolds into osteochondral defects of a rabbit model. Our findings demonstrated that the multilayer scaffolds were able to induce articular cartilage formation by accelerating the early subchondral bone regeneration, and the newly formed tissues could well integrate with the native tissues. Consequently, the current study not only achieves osteochondral repair, but also suggests a promising strategy for the fabrication of bio-inspired multilayer scaffolds with well-designed architecture and gradient composition via SLS technique.

Synthesis of strontium chondroitin sulfate and the evaluation of its capability to attenuate osteoarthritis

Osteoarthritis (OA) is the most prevalent musculoskeletal disorder and the leading cause of joint disability in elderly patients. In this study, we fabricated strontium chondroitin sulfate (SrCS), a new polysaccharide-metal ion complex that is the combination of chondroitin sulfate and strontium, which are two widely adopted chemicals in OA clinical management. The structural, chemical compositions and morphology of as-fabricated SrCS were systematically investigated. Cell proliferation test, RT-PCR and preliminary animal studies were conducted to evaluate the clinical potential of SrCS on OA treatment. The materials characterization results verified that the Sr was successfully integrated into CS by replacing sodium in the original structure and formed a new polysaccharide-metal ion complex. The cell proliferation results indicated that the SrCS has excellent biocompatibility for both chondrocyte and osteoblast. The RT-PCR results showed that the SrCS can significantly increase the expression of COLII and ACAN, decrease MMP1 and MMP13 in chondrocyte and decrease the IL-6 and IL-1β in both chondrocyte and osteoblast. Preliminary animal studies demonstrated that SrCS can effectively simulate the articular cartilage formation in SD-rats after modified Hulth’s OA modeling surgery. We therefore believed that the SrCS should be a rather effective chemical for OA clinical management as well as a beneficial component for various biomaterials in cartilage tissue engineering.

Cell origin, volume and arrangement are drivers of articular cartilage formation, morphogenesis and response to injury in mouse limbs

Limb synovial joints are composed of distinct tissues, but it is unclear which progenitors produce those tissues and how articular cartilage acquires its functional postnatal organization characterized by chondrocyte columns, zone-specific cell volumes and anisotropic matrix. Using novel Gdf5CreERT2 (Gdf5-CE), Prg4-CE and Dkk3-CE mice mated to R26-Confetti or single-color reporters, we found that knee joint progenitors produced small non-migratory progenies and distinct local tissues over prenatal and postnatal time. Stereological imaging and quantification indicated that the columns present in juvenile-adult tibial articular cartilage consisted of non-daughter, partially overlapping lineage cells, likely reflecting cell rearrangement and stacking. Zone-specific increases in cell volume were major drivers of tissue thickening, while cell proliferation or death played minor roles. Second harmonic generation with 2-photon microscopy showed that the collagen matrix went from being isotropic and scattered at young stages to being anisotropic and aligned along the cell stacks in adults. Progenitor tracing at prenatal or juvenile stages showed that joint injury provoked a massive and rapid increase in synovial Prg4+ and CD44+/P75+ cells some of which filling the injury site, while neighboring chondrocytes appeared unresponsive. Our data indicate that local cell populations produce distinct joint tissues and that articular cartilage growth and zonal organization are mainly brought about by cell volume expansion and topographical cell rearrangement. Synovial Prg4+ lineage progenitors are exquisitely responsive to acute injury and may represent pioneers in joint tissue repair.