Intra-articular injections of bone morphogenetic protein-7 retard progression of existing cartilage degeneration

Chondroprotective Effects of Chondrogenic Differentiated Adipose-Derived Mesenchymal Stem Cells Sheet on Degenerated Articular Cartilage in an Experimental Rabbit Model

Adipose-derived stem cells (ADSCs) have been studied for many years as a therapeutic option for osteoarthritis (OA); however, their efficacy remains insufficient. Since platelet-rich plasma (PRP) induces chondrogenic differentiation in ADSCs and the formation of a sheet structure by ascorbic acid can increase the number of viable cells, we hypothesized that the injection of chondrogenic cell sheets combined with the effects of PRP and ascorbic acid may hinder the progression of OA. The effects of induction of differentiation by PRP and formation of sheet structure by ascorbic acid on changes in chondrocyte markers (collagen II, aggrecan, Sox9) in ADSCs were evaluated. Changes in mucopolysaccharide and VEGF-A secretion from cells injected intra-articularly in a rabbit OA model were also evaluated. ADSCs treated by PRP strongly chondrocyte markers, including type II collagen, Sox9, and aggrecan, and their gene expression was maintained even after sheet-like structure formation induced by ascorbic acid. In this rabbit OA model study, the inhibition of OA progression by intra-articular injection was improved by inducing chondrocyte differentiation with PRP and sheet structure formation with ascorbic acid in ADSCs.

Runx1 is a key regulator of articular cartilage homeostasis by orchestrating YAP, TGFβ, and Wnt signaling in articular cartilage formation and osteoarthritis

Runt-related transcription factor 1 (Runx1) plays a key role in cartilage formation, but its function in articular cartilage formation is unclear. We generated non-inducible and inducible Runx1-deficient mice (Runx1f/fCol2α1-Cre and Runx1f/fCol2α1-CreER mice) and found that chondrocyte-specific Runx1-deficient mice developed a spontaneous osteoarthritis (OA)-like phenotype and showed exacerbated articular cartilage destruction under OA, characterized by articular cartilage degradation and cartilage ossification, with decreased Col2α1 expression and increased Mmp13 and Adamts5 expression. RNA-sequencing analysis of hip articular cartilage from the Runx1f/fCol2α1-Cre mice compared to that from wild-type mice and subsequent validation analyses demonstrated that Runx1 is a central regulator in multiple signaling pathways, converging signals of the Hippo/Yap, TGFβ/Smad, and Wnt/β-catenin pathways into a complex network to regulate the expression of downstream genes, thereby controlling a series of osteoarthritic pathological processes. RNA-sequencing analysis of mutant knee joints showed that Runx1's role in signaling pathways in articular cartilage is different from that in whole knee joints, indicating that Runx1 regulation is tissue-specific. Histopathologic analysis confirmed that Runx1 deficiency decreased the levels of YAP and p-Smad2/3 and increased the levels of active β-catenin. Overexpression of Runx1 dramatically increased YAP expression in chondrocytes. Adeno-associated virus-mediated Runx1 overexpression in the knee joints of osteoarthritic mice showed the protective effect of Runx1 on articular cartilage damaged in OA. Our results notably showed that Runx1 is a central regulator of articular cartilage homeostasis by orchestrating the YAP, TGFβ, and Wnt signaling pathways in the formation of articular cartilage and OA, and targeting Runx1 and its downstream genes may facilitate the design of novel therapeutic approaches for OA.

Osteoarthritis: Novel Molecular Mechanisms Increase Our Understanding of the Disease Pathology

Although osteoarthritis (OA) is the most common musculoskeletal condition that causes significant health and social problems worldwide, its exact etiology is still unclear. With an aging and increasingly obese population, OA is becoming even more prevalent than in previous decades. Up to 35% of the world’s population over 60 years of age suffers from symptomatic (painful, disabling) OA. The disease poses a tremendous economic burden on the health-care system and society for diagnosis, treatment, sick leave, rehabilitation, and early retirement. Most patients also experience sleep disturbances, reduced capability for exercising, lifting, and walking and are less capable of working, and maintaining an independent lifestyle. For patients, the major problem is disability, resulting from joint tissue destruction and pain. So far, there is no therapy available that effectively arrests structural deterioration of cartilage and bone or is able to successfully reverse any of the existing structural defects. Here, we elucidate novel concepts and hypotheses regarding disease progression and pathology, which are relevant for understanding underlying the molecular mechanisms as a prerequisite for future therapeutic approaches. Emphasis is placed on topographical modeling of the disease, the role of proteases and cytokines in OA, and the impact of the peripheral nervous system and its neuropeptides.

Cryopreserved, Thin, Laser-Etched Osteochondral Allograft maintains the functional components of articular cartilage after 2 years of storage

BACKGROUND

Despite improvements in treatment options and techniques, articular cartilage repair continues to be a challenge for orthopedic surgeons. This study provides data to support that the 2-year Cryopreserved, Thin, Laser-Etched Osteochondral Allograft (T-LE Allograft) embodies the necessary viable cells, protein signaling, and extracellular matrix (ECM) scaffold found in fresh cartilage in order to facilitate a positive clinical outcome for cartilage defect replacement and repair.

METHODS

Viability testing was performed by digestion of the graft, and cells were counted using a trypan blue assay. Growth factor and ECM protein content was quantified using biochemical assays. A fixation model was introduced to assess tissue outgrowth capability and cellular metabolic activity in vitro. Histological and immunofluorescence staining were employed to confirm tissue architecture, cellular outgrowth, and presence of ECM. The effects of the T-LE Allograft to signal bone marrow-derived mesenchymal stem cell (BM-MSC) migration and chondrogenic differentiation were evaluated using in vitro co-culture assays. Immunogenicity testing was completed using flow cytometry analysis of cells obtained from digested T-LE Allografts and fresh articular cartilage.

RESULTS

Average viability of the T-LE Allograft post-thaw was found to be 94.97 ± 3.38%, compared to 98.83 ± 0.43% for fresh articular cartilage. Explant studies from the in vitro fixation model confirmed the long-term viability and proliferative capacity of these chondrocytes. Growth factor and ECM proteins were quantified for the T-LE Allograft revealing similar profiles to fresh articular cartilage. Cellular signaling of the T-LE Allograft and fresh articular cartilage both exhibited similar outcomes in co-culture for migration and differentiation of BM-MSCs. Flow cytometry testing confirmed the T-LE Allograft is immune-privileged as it is negative for immunogenic markers and positive for chondrogenic markers.

CONCLUSIONS

Using our novel, proprietary cryopreservation method, the T-LE Allograft, retains excellent cellular viability, with native-like growth factor and ECM composition of healthy cartilage after 2 years of storage at - 80 °C. The successful cryopreservation of the T-LE Allograft alleviates the limited availably of conventionally used fresh osteochondral allograft (OCA), by providing a readily available and simple to use allograft solution. The results presented in this paper supports clinical data that the T-LE Allograft can be a successful option for repairing chondral defects.

Periodic injections of adipose-derived stem cell sheets attenuate osteoarthritis progression in an experimental rabbit model

Background

Subcutaneous adipose tissue represents an abundant source of multipotent adult stem cells named as Adipose-derived stem cells (ADSCs). With a cell sheet approach, ADSCs survive longer, and can be delivered in large quantities. We investigated whether intra-articular ADSC sheets attenuated osteoarthritis (OA) progression in a rabbit anterior cruciate ligament transection (ACLT) model.

Methods

Fabricating medium containing ascorbate-2-phosphate was used to enhance collagen protein secretion by the ADSCs to make ADSC sheets. At 4 weeks after ACLT, autologous ADSC sheets were injected intra-articularly into the right knee (ADSC sheets group), and autologous cell death sheets treated by liquid nitrogen were injected into the left knee (control group). Subsequent injections were administered once weekly. Femoral condyles were compared macroscopically and histologically.

Results

Macroscopically, OA progression was significantly milder in the ADSC sheets than in the control groups. Histologically, control knees showed obvious erosions in the medial and lateral condyles, while cartilage was retained predominantly in the ADSC sheets group. Immunohistochemically, MMP-1, MMP-13, ADAMTS-4 were less expressive in the ADSC sheets than in the control groups.

Conclusions

Periodic ADSC sheets injections inhibited articular cartilage degeneration without inducing any adverse effects. A large quantity of autologous ADSCs delivered by cell sheets homed to the synovium and protected chondrocytes.

Drug delivery in intervertebral disc degeneration and osteoarthritis: Selecting the optimal platform for the delivery of disease-modifying agents

Osteoarthritis (OA) and intervertebral disc degeneration (IVDD) as major cause of chronic low back pain represent the most common degenerative joint pathologies and are leading causes of pain and disability in adults. Articular cartilage (AC) and intervertebral discs are cartilaginous tissues with a similar biochemical composition and pathophysiological aspects of degeneration. Although treatments directed at reversing these conditions are yet to be developed, many promising disease-modifying drug candidates are currently under investigation. Given the localized nature of these chronic diseases, drug delivery systems have the potential to enhance therapeutic outcomes by providing controlled and targeted release of bioactives, minimizing the number of injections needed and increasing drug concentration in the affected areas. This review provides a comprehensive overview of the currently most promising disease-modifying drugs as well as potential drug delivery systems for OA and IVDD therapy.

Tenascin-C Prevents Articular Cartilage Degeneration in Murine Osteoarthritis Models

Objective The objective of this study was to determine whether intra-articular injections of tenascin-C (TNC) could prevent cartilage damage in murine models of osteoarthritis (OA). Design Fluorescently labeled TNC was injected into knee joints and its distribution was examined at 1 day, 4 days, 1 week, 2 weeks, and 4 weeks postinjection. To investigate the effects of TNC on cartilage degeneration after surgery to knee joints, articular spaces were filled with 100 μg/mL (group I), 10 μg/mL (group II) of TNC solution, or control (group III). TNC solution of 10 μg/mL was additionally injected twice after 3 weeks (group IV) or weekly after 1 week, 2 weeks, and 3 weeks (group V). Joint tissues were histologically assessed using the Mankin score and the modified Chambers system at 2 to 8 weeks after surgery. Results Exogenous TNC was maintained in the cartilage and synovium for 1 week after administration. Histological scores in groups I and II were better than scores in group III at 4 and 6 weeks, but progressive cartilage damage was seen in all groups 8 weeks postoperatively. Sequential TNC injections (groups IV and V) showed significantly better Mankin score than single injection (group II) at 8 weeks. Conclusion TNC administered exogenously remained in the cartilage of knee joints for 1 week, and could decelerate articular cartilage degeneration in murine models of OA. We also showed that sequential administration of TNC was more effective than a single injection. TNC could be an important molecule for prevention of articular cartilage damage.

Advances and Prospects in Stem Cells for Cartilage Regeneration

The histological features of cartilage call attention to the fact that cartilage has a little capacity to repair itself owing to the lack of a blood supply, nerves, or lymphangion. Stem cells have emerged as a promising option in the field of cartilage tissue engineering and regenerative medicine and could lead to cartilage repair. Much research has examined cartilage regeneration utilizing stem cells. However, both the potential and the limitations of this procedure remain controversial. This review presents a summary of emerging trends with regard to using stem cells in cartilage tissue engineering and regenerative medicine. In particular, it focuses on the characterization of cartilage stem cells, the chondrogenic differentiation of stem cells, and the various strategies and approaches involving stem cells that have been used in cartilage repair and clinical studies. Based on the research into chondrocyte and stem cell technologies, this review discusses the damage and repair of cartilage and the clinical application of stem cells, with a view to increasing our systematic understanding of the application of stem cells in cartilage regeneration; additionally, several advanced strategies for cartilage repair are discussed.

Disease-modifying treatments for osteoarthritis (DMOADs) of the knee and hip: lessons learned from failures and opportunities for the future

Osteoarthritis (OA) is the biggest unmet medical need among the many musculoskeletal conditions and the most common form of arthritis. It is a major cause of disability and impaired quality of life in the elderly. We review several ambitious but failed attempts to develop joint structure-modifying treatments for OA. Insights gleaned from these attempts suggest that these failures arose from unrealistic hypotheses, sub-optimal selection of patient populations or drug dose, and/or inadequate sensitivity of the trial endpoints. The long list of failures has prompted a paradigm shift in OA drug development with redirection of attention to: (1) consideration of the benefits of localized vs systemic pharmacological agents, as indicated by the increasing number of intra-articularly administered compounds entering clinical development; (2) recognition of OA as a complex disease with multiple phenotypes, that may each require somewhat different approaches for optimizing treatment; and (3) trial enhancements based on guidance regarding biomarkers provided by regulatory agencies, such as the Food and Drug Administration (FDA), that could be harnessed to help turn failures into successes.

Targets, models and challenges in osteoarthritis research

Osteoarthritis is a chronic degenerative disorder of the joint and represents one of the most common diseases worldwide. Its prevalence and severity are increasing owing to aging of the population, but treatment options remain largely limited to painkillers and anti-inflammatory drugs, which only provide symptomatic relief. In the late stages of the disease, surgical interventions are often necessary to partially restore joint function. Although the focus of osteoarthritis research has been originally on the articular cartilage, novel findings are now pointing to osteoarthritis as a disease of the whole joint, in which failure of different joint components can occur. In this Review, we summarize recent progress in the field, including data from novel ‘omics’ technologies and from a number of preclinical and clinical trials. We describe different in vitro and in vivo systems that can be used to study molecules, pathways and cells that are involved in osteoarthritis. We illustrate that a comprehensive and multisystem approach is necessary to understand the complexity and heterogeneity of the disease and to better guide the development of novel therapeutic strategies for osteoarthritis.

The paracrine effect of adipose-derived stem cells inhibits osteoarthritis progression

Background

This study aimed to determine whether intra-articularly injected adipose-derived stem cells (ADSCs) inhibited articular cartilage degeneration during osteoarthritis (OA) development in a rabbit anterior cruciate ligament transection (ACLT) model. The paracrine effects of ADSCs on chondrocytes were investigated using a co-culture system.

Methods

ACLT was performed on both knee joints of 12 rabbits. ADSCs were isolated from the subcutaneous adipose tissue. ADSCs with hyaluronic acid were intra-articularly injected into the left knee, and hyaluronic acid was injected into the right knee. The knees were compared macroscopically, histologically, and immunohistochemically at 8 and 12 weeks. In addition, cell viability was determined using co-culture system of ADSCs and chondrocytes.

Results

Macroscopically, osteoarthritis progression was milder in the ADSC-treated knees than in the control knees 8 weeks after ACLT. Histologically, control knees showed obvious erosions in both the medial and lateral condyles at 8 weeks, while cartilage was predominantly retained in the ADSC-treated knees. At 12 weeks, the ADSC-treated knees showed a slight suppression of cartilage degeneration, unlike the control knees.

Immunohistochemically, MMP-13 expression was less in the ADSC-treated cartilage than in the control knees. The cell viability of chondrocytes co-cultured with ADSCs was higher than that of chondrocytes cultured alone. TNF-alpha-induced apoptotic stimulation was similar between the two groups.

Conclusions

Intra-articularly injected ADSCs inhibited cartilage degeneration progression by homing to the synovium and secreting a liquid factor having chondro-protective effects such as chondrocyte proliferation and cartilage matrix protection.

The disease-modifying effect of dehydroepiandrosterone in different stages of experimentally induced osteoarthritis: a histomorphometric study

Background

Osteoarthritis (OA) is likely to become an increasing burden in the coming decades. Various agents have been developed to slow the progression of OA, and are collectively known as ‘disease-modifying drugs’, however, there is still little reliable evidence that such agents will be successful. Dehydroepiandrosterone (DHEA), a sex hormone precursor, has been recently proven as protective agent against OA, but the exact mechanism is still unkown. In the current study, the effects of weekly intra-articular injections of DHEA in preventing the progression of existing cartilage degeneration in an OA rabbit model were evaluated. The aim of the current study is to demonstrate the feature of its disease-modifying efficacy during OA progression.

Methods

Thirty male New Zealand white rabbits were used in this study. An anterior cruciate ligament transection (ACLT) model was used to create a progressive OA model in twenty rabbits. The animals were treated with DHEA or a placebo and were necropsied at 9 and 16 weeks. Ten rabbits receiving sham operations served as controls. The articular cartilage of the medial femoral condyle (MFC), lateral femoral condyle (LFC), medial tibial plateau (MTP) and lateral tibial plateau (LTP) was evaluated macroscopically and histologically.

Results

In the joints of the sham-operated rabbits, few histological changes were detected on the articular surfaces of the femoral condyles and tibial plateaus. ACLT obviously induced erosive changes on the cartilage surfaces. Compared to the placebo group, the macroscopic and Mankin score analyses demonstrated that the DHEA treatment markedly reduced the cartilage lesions and delayed cartilage degeneration in the four regions of the knee at 9 weeks after operation (macroscopic score: MFC P = 0.013; LFC P = 0.048; MTP P = 0.045; LTP P = 0.02, Mankin score: MFC P = 0.012; LFC P = 0.034; MTP P = 0.016; LTP P = 0.002). At 16 weeks, DHEA demonstrated chondroprotective effects on the lateral compartment of the knee compared to the placebo group, whereas the cartilage degeneration at the medial compartment of the knee did not differ among the groups (macroscopic score: LFC P = 0.046; LTP = 0.034, Mankin score: LFC P = 0.005; LTP P = 0.002).

Conclusion

The disease-modifying efficacy of DHEA aganist OA is time-specific and site-dependent. DHEA could be used as a disease-modifying strategy to limit the progression of OA, especially in the middle stage.

Intra-articular resveratrol injection prevents osteoarthritis progression in a mouse model by activating SIRT1 and thereby silencing HIF-2α

We investigated the feasibility of the intra-articular injection of resveratrol for preventing the progression of existing cartilage degeneration in a mouse model of osteoarthritis (OA). The effects of resveratrol on the expression of silent information regulator 2 type 1 (SIRT1), hypoxia-inducible factor-2α (HIF-2α) and catabolic factors in OA cartilage was explored. OA was induced in the mouse knee via destabilization of the medial meniscus (DMM). Resveratrol was injected weekly into the operated knee beginning 4 weeks after surgery. The OA phenotype was evaluated via histological and immunohistochemical analyses at 8 weeks after DMM. Western blot analysis was performed to identify whether resveratrol modulated the interleukin (IL)-1β-induced expression of HIF-2α in human chondrocytes. Histologically, resveratrol treatment preserved the structural homeostasis of the articular cartilage and the subchondral bone. Following resveratrol injection, the expression of collagen type II was retained, but the expression of inducible nitric oxide synthase and matrix metalloproteinase-13 was reduced in OA cartilage. Moreover, the administration of resveratrol significantly induced the activation of SIRT1 and the inhibition of HIF-2α expression in mouse OA cartilage and in IL-1β-treated human chondrocytes. These findings indicate that the intra-articular injection of resveratrol significantly prevents the destruction of OA cartilage by activating SIRT1 and thereby suppressing the expression of HIF-2α and catabolic factors.

Novel microinjector for carrying bone substitutes for bone regeneration in periodontal diseases

BACKGROUND/PURPOSE

Traditionally, guide bone regeneration (GBR) was a widely used method for repairing bone lost from periodontal disease. There were some disadvantages associated with the GBR method, such as the need for a stable barrier membrane and a new creative cavity during the surgical process. To address these disadvantages, the purpose of this study was to evaluate a novel microinjector developed for dental applications. The microinjector was designed to carry bone graft substitutes to restore bone defects for bone regeneration in periodontal diseases. The device would be used to replace the GBR method.

METHODS

In this study, the injected force and ejected volume of substitutes (including air, water, and ethanol) were defined by Hooke's law (n = 3). The optimal particle size of bone graft substitutes was determined by measuring the recycle ratio of bone graft substitutes from the microinjector (n = 3). Furthermore, a novel agarose gel model was used to evaluate the feasibility of the microinjector.

RESULTS

The current study found that the injected force was less than 0.4 N for obtaining the ejected volume of approximately 2 mL, and when the particle size of tricalcium phosphate (TCP) was smaller than 0.5 mm, 80% TCP could be ejected from the microinjector. Furthermore, by using an agarose model to simulate the periodontal soft tissue, it was also found that bone graft substitutes could be easily injected into the gel.

CONCLUSION

The results confirmed the feasibility of this novel microinjector for dental applications to carry bone graft substitutes for the restoration of bone defects of periodontal disease.

In vitro and in vivo evaluation of doxycycline-chondroitin sulfate/PCLmicrospheres for intraarticular treatment of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease, which has no complete treatment with medication yet. Intraarticular hyaluronan (HA) injection can decrease pain and modify the natural course of OA. This study was designed to provide long term delivery of an MMP (matrix-metalloproteinase) inhibitor agent-doxycycline, together with matrix regenerative agent-chondroitin sulfate for treating OA which progress with matrix degenerations. Doxycycline (D) and doxycycline-chondroitin sulfate (D-CS) loaded poly-ɛ-caprolactone (PCL) microspheres (MS) were prepared as intraarticular delivery systems. Bio-effectiveness of developed microspheres was first evaluated with three-dimensional in vitro model of OA where both MS showed significant reduction in MMP-13 levels compared to untreated OA-chondrocytes at 15 and 24 days. Significant decrease was observed in GAG release into the media for both D MS and D-CS MS treated groups at 15 and 24 days. Second, the microspheres were injected to rabbit knee in hyaluronan (HA) to evaluate the effectiveness of the treatment. Radiographic scores of D MS and D-CS MS groups improved after 8 weeks when compared to OA group. Mankin-Pitzker histological scores similarly showed improvement with D MS and D-CSMS groups when compared to OA group. Ex vivo hardness tests of cartilages demonstrated superior hardness values with both doses of D-CSMS compared to OA group. D MS showed promising improvement of OA in histology results. Although, both MS groups had similar effects on cells in the in vitro model, D-CSMS had a positive contribution on all in vivo treatment outcomes and showed potential as a new strategy for treatment when applied to OA knee joints.

Bevacizumab, an anti-vascular endothelial growth factor antibody, inhibits osteoarthritis

Introduction

Angiogenesis is an important factor in the development of osteoarthritis (OA). We investigated the efficacy of bevacizumab, an antibody against vascular endothelial growth factor and an inhibitor of angiogenesis, in the treatment of OA using a rabbit model of anterior cruciate ligament transection.

Methods

First, we evaluated the response of gene expression and histology of the normal joint to bevacizumab treatment. Next, in a rabbit model of OA induced by anterior cruciate ligament transection, we used macroscopic and histological evaluations and real-time polymerase chain reaction (PCR) to examine the responses to intravenous (systemic) administration of bevacizumab (OAB IV group). We also investigated the efficacy of intra-articular (local) administration of bevacizumab in OA-induced rabbits (OAB IA group).

Results

Histologically, bevacizumab had no negative effect in normal joints. Bevacizumab did not increase the expression of genes for catabolic factors in the synovium, subchondral bone, or articular cartilage, but it increased the expression of collagen type 2 in the articular cartilage. Macroscopically and histologically, the OAB IV group exhibited a reduction in articular cartilage degeneration and less osteophyte formation and synovitis compared with the control group (no bevacizumab; OA group). Real-time PCR showed significantly lower expression of catabolic factors in the synovium in the OAB IV group compared with the OA group. In articular cartilage, expression levels of aggrecan, collagen type 2, and chondromodulin-1 were higher in the OAB IV group than in the OA group. Histological evaluation and assessment of pain behaviour showed a superior effect in the OAB IA group compared with the OAB IV group 12 weeks after administration of bevacizumab, even though the total dosage given to the OAB IA group was half that received by the OAB IV group.

Conclusions

Considering the dosage and potential adverse effects of bevacizumab, the local administration of bevacizumab is a more advantageous approach than systemic administration. Our results suggest that intra-articular bevacizumab may offer a new therapeutic approach for patients with post-traumatic OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0427-y) contains supplementary material, which is available to authorized users.

Bone Morphogenetic Protein (BMP) signaling in development and human diseases

Bone Morphogenetic Proteins (BMPs) are a group of signaling molecules that belongs to the Transforming Growth Factor-β (TGF-β) superfamily of proteins. Initially discovered for their ability to induce bone formation, BMPs are now known to play crucial roles in all organ systems. BMPs are important in embryogenesis and development, and also in maintenance of adult tissue homeostasis. Mouse knockout models of various components of the BMP signaling pathway result in embryonic lethality or marked defects, highlighting the essential functions of BMPs. In this review, we first outline the basic aspects of BMP signaling and then focus on genetically manipulated mouse knockout models that have helped elucidate the role of BMPs in development. A significant portion of this review is devoted to the prominent human pathologies associated with dysregulated BMP signaling.

Antagonistic and synergistic effects of bone morphogenetic protein 2/7 and all-trans retinoic acid on the osteogenic differentiation of rat bone marrow stromal cells

The osteogenesis of bone marrow stromal cells (BMSCs) is of paramount importance for the repair of large-size bone defects, which may be compromised by the dietary-accumulated all-trans retinoic acid (ATRA). We have shown that heterodimeric bone morphogenetic protein 2/7 (BMP2/7) could induce bone regeneration in a significantly higher dose-efficiency in comparison with homodimeric BMPs. In this study, we evaluated the effects of ATRA and BMP2/7 on the proliferation, differentiation, mineralization and osteogenic genes. ATRA and BMP2/7 exhibited both antagonistic and synergistic effects on the osteogenesis of BMSCs. ATRA significantly inhibited proliferation and expression of osteocalcin but enhanced the activity of alkaline phosphatase of BMSCs. On day 21, 50 ng/mL BMP2/7 could antagonize the inhibitive effects of ATRA and significantly enhance osteogenesis of BMSCs. These findings suggested a promising application potential of heterodimeric BMP2/7 in clinic to promote bone regeneration for the cases with dietary accumulated ATRA.

Protective effect of a new biomaterial against the development of experimental osteoarthritis lesions in rabbit: a pilot study evaluating the intra-articular injection of alginate-chitosan beads dispersed in an hydrogel

OBJECTIVE

This study aimed to evaluate the structural benefit of a new biomaterial composed of alginate-chitosan (AC) beads dispersed in a hydrogel (H) derived from chitosan on the development of osteoarthritis (OA) in rabbit.

DESIGN

OA was induced by the surgical transection of the anterior cruciate ligament in rabbits. Animals received a single intra-articular injection (900 μl) of AC beads in H hydrogel, H hydrogel alone or saline a week after surgery. OA development was followed by X-rays. Blood samples were collected throughout the study to measure biological markers (Prostaglandins E2 - PGE2 and C reactive protein - CRP). Macroscopic observation and histological evaluation of articular cartilage and synovial membrane were performed 6 weeks after surgery.

RESULTS

AC beads in H hydrogel prevented from the development of OA based on the reduction of the Kellgren & Lawrence (K&L) score. It also significantly reduced the histological score of cartilage lesion severity. This effect was homogenous on every joint compartment. It was due to a significant effect on cartilage structure and cellularity scores. The injection of AC beads in H hydrogel also tended to reduce the synovial membrane inflammation. No significant variation of biological markers was noted.

CONCLUSIONS

The present pilot study provides interesting and promising results for the use of AC beads in H hydrogel in animal. It indeed prevented the development of OA cartilage lesions without inflammatory signs. The potencies of this biomaterial to protect OA joint should be further documented. It could then represent a new alternative for viscosupplementation in human OA management.

Key Pathways to Prevent Posttraumatic Arthritis for Future Molecule-Based Therapy

Joint injuries are common, especially among young adults aged 18 to 44 years. They are accompanied by a cascade of events that increase the risk of posttraumatic osteoarthritis (PTOA). Therefore, understanding of biological responses that predispose to PTOA should help in determining treatment modalities to delay and/or prevent the onset and progression of the disease. The vast majority of the literature pointed to chondrocyte death and apoptosis, inflammation and matrix damage/fragmentation being the earliest events that follow joint trauma. Together these events lead to the development of osteoarthritis-like focal cartilage lesions that if untreated have a tendency to expand and progress to fully developed disease. Currently, the only treatments available for joint trauma are surgical interventions. Experimental biologic approaches involve engineering of cartilage with the use of cells (stem cells or chondrocytes), juvenile or adult cartilage pieces, scaffolds, and various polymeric matrices. The major challenge for all of them is regeneration of normal functional mature hyaline cartilage that can sustain the load, resist compression, and most important, integrate with the host tissue. If the tissue is spontaneously repaired it fails to reproduce original structure and function and thus, may be more susceptible to re-injury. Thus, there is a critical need to develop novel molecular mechanism-based therapeutic approaches to biologic chondral and/or osteochondral repair. The focus of this review is on the earliest molecular and cellular manifestations of injury that can be grouped based on the following therapeutic options for PTOA: chondroprotection, anti-inflammatory, matrix protection, and matrix remodeling/matrix synthesis.

Efficacy Evaluation of a New Hyaluronan Derivative HYADD® 4-G to Maintain Cartilage Integrity in a Rabbit Model of Osteoarthritis

Objective: To test the efficacy of a hyaluronan derivative (HYADD^®4-G) in a model of osteoarthritis (anterior cruciate ligament [ACLT]) and to compare its efficacy with the injection of growth factors. Design: In a first experimental set-up, specially selected for treatment scheme with published studies on hyaluronan or growth factor efficacy in osteoarthritis, saline, HYADD^®4-G, rh-BMP-7, and the treatments of rh-BMP-7 or rh-BMP-2 with HYADD^®4-G were injected after ACLT, for five times starting 3 weeks after ACLT. Euthanasia was at day 70. The knees were evaluated by gross morphological observation, x-ray, and histology (Study A). In a second experimental set-up selected to evaluate the efficacy of three viscosupplement injections, starting 4 weeks after ACTL, HYADD^®4-G was compared to saline (Study B). Results: (A) X-ray analysis showed more damage in the saline group than all other treatment groups (2.67 ± 0.61 for saline, 0.83 ± 0.26 for HYADD^®4-G, 1.67 ± 0.82 for HYADD^®4-G with rh-BMP-2, 0.75 ± 0.76 for HYADD^®4-G with rh-BMP-7, and 1.58 ± 0.49 for rh-BMP-7), P < 0.05. In the femoral condyle, the Mankin's score for HYADD^®4-G with rh-BMP-2, HYADD^®4-G with rh-BMP-7, and rh-BMP7 alone was statistically lower compared to saline in the medial part; in the lateral part a significant lower value was observed in the HYADD^®4-G with the rh-BMP-2 group. (B) The Kellgren and Lawrence score and Mankin's score was lower in the HYADD^®4-G group than in the saline group (P < 0.002 and P = 0.0031). Conclusions: These two studies suggest that HYADD^®4-G delayed the cartilage degeneration and that the association of HYADD^®4-G with growth factors is synergistic.

Role of bone architecture and anatomy in osteoarthritis

When considering the pathogenesis of osteoarthritis (OA), it is important to review the contribution of bone in addition to the contribution of cartilage and synovium. Although bone clearly plays a role in determining the distribution of biomechanical forces across joints, which in turn plays a role in the initiation of OA, it has also more recently been appreciated that bone may contribute in a biological sense to the pathogenesis of OA. Far from being a static structure, bone is a dynamic tissue undergoing constant remodeling, and it is clear from a number of radiographic and biochemical studies that bone and cartilage degradation occurs hand in hand. Whether the initial instigating event in OA occurs in cartilage or bone is not known, but it is clear that bony changes occur very early in the pathogenesis of OA and often predate radiographic appearance of the disease. This review focuses on the structural variants of both hip and knee that have been associated with OA and the ultrastructural bone changes in these sites occurring in early OA pathogenesis. This article is part of a Special Issue entitled "Osteoarthritis".

Osteoarthritis, a disease bridging development and regeneration

The osteoarthritic diseases are common disorders characterized by progressive destruction of the articular cartilage in the joints, and associated with remodeling of the subchondral bone, synovitis and the formation of bone outgrowths at the joint margins, osteophytes. From the clinical perspective, osteoarthritis leads to joint pain and loss of function. Osteoarthritis is the leading cause of progressive disability. New data from genetic, translational and basic research have demonstrated that pathways with essential roles in joint and bone development also contribute to the postnatal homeostasis of the articular cartilage and are involved in osteoarthritis, making these potential therapeutic targets. Other systems of interest are the tissue-destructive enzymes that break down the extracellular matrix of the cartilage as well as mediators of inflammation that contribute to synovitis. However, the perspective of a durable treatment over years to decades highlights the need for a personalized medicine approach encompassing a global view on the disease and its management, thereby including nonpharmaceutical approaches such as physiotherapy and advanced surgical methods. Integration of novel strategies based on their efficacy and safety with the identification of individuals at risk and optimal individual rehabilitation management remains a major challenge for the medical community in particular, as the incidence of osteoarthritis is likely to further increase with the overall aging of the population.

The "bone morphogenic proteins" pathways in bone and joint diseases: translational perspectives from physiopathology to therapeutic targets

A large body of evidence supports an important role of bone morphogenic proteins (BMPs) pathways in skeletal development in the embryo. BMPs are also involved in skeletal homeostasis and diseases in the adult. They were first identified as major bone anabolic agents and recent advances indicate that they also regulate osteoclastogenesis and joint components via multiple cross-talks with other signaling pathways. This review attempts to integrate these data in the pathogenesis of bone and joints diseases, such as osteoporosis, fracture healing, osteoarthritis, inflammatory arthritis, or bone metastasis. The use of recombinant BMPs in bone tissue engineering and in the treatment of skeletal diseases, or future therapeutic strategies targeting BMPs signal and its regulators, will be discussed based on these considerations.

Anabolic/Catabolic balance in pathogenesis of osteoarthritis: identifying molecular targets

Osteoarthritis is the most common degenerative musculoskeletal disease. In healthy cartilage, a low turnover of extracellular matrix molecules occurs. Proper balance of anabolic and catabolic activities is thus crucial for the maintenance of cartilage tissue integrity and for the repair of molecular damages sustained during daily usage. In persons with degenerative diseases such as osteoarthritis, this balance of anabolic and catabolic activities is compromised, and the extent of tissue degradation predominates over the capacity of tissue repair. This mismatch eventually results in cartilage loss in persons with osteoarthritis. Tissue homeostasis is controlled by coordinated actions and crosstalk among a number of proanabolic and antianabolic and procatabolic and anticatabolic factors. In osteoarthritis, an elevation of antianabolic and catabolic factors occurs. Interestingly, anabolic activity is also increased, but this response fails to repair the tissue because of both quantitative and qualitative insufficiency. This review presents an overview of the anabolic and catabolic activities involved in cartilage degeneration and the interplay among different signaling and metabolic factors. Understanding the basic molecular mechanisms responsible for tissue degeneration is critical to identifying and developing means to efficiently block or reverse the pathobiological symptoms of osteoarthritis.