Inhibition of oncostatin M in osteoarthritic synovial fluid enhances GAG production in osteoarthritic cartilage repair

Mediators in the synovial fluid are thought to play a major role in osteoarthritic cartilage turnover. The purpose of the current study was to investigate the role of oncostatin M (OSM) in osteoarthritis (OA) by evaluating the presence of the cytokine and its receptors in the OA joint and interfering with its activity in synovial fluid co-cultured with cartilage explants. OSM levels were increased in the synovial fluid of osteoarthritic patients compared to healthy donors. Immunohistochemistry confirmed the presence of both the leukaemia inhibitory factor (LIF) and OSM receptors for OSM throughout the whole depth of osteoarthritic cartilage and synovial tissue, whereas in healthy cartilage their presence seemed more restricted to the superficial zone. Blocking OSM activity, using an activity inhibiting antibody, in 25 % osteoarthritic synovial fluid added to OA cartilage explant cultures increased glycosaminoglycan (GAG) content from 18.6 mg/g to 24.3 mg/g (P < 0.03) and total production from 7.0 mg/g to 11.9 mg/g (P < 0.003). However, OSM exogenously added to cartilage explant cultures reflecting low and high concentrations in the synovial fluid (5 and 50 pg/mL) did not affect cartilage matrix turnover, suggesting that factors present in the synovial fluid act in concert with OSM to inhibit GAG production. The current study indicates the potential to enhance cartilage repair in osteoarthritis by modulating the joint environment by interfering with OSM activity

Lack of high BMI-related features in adipocytes and inflammatory cells in the infrapatellar fat pad (IFP)

BACKGROUND: Obesity is associated with the development and progression of osteoarthritis (OA). Although the infrapatellar fat pad (IFP) could be involved in this association, due to its intracapsular localization in the knee joint, there is currently little known about the effect of obesity on the IFP. Therefore, we investigated cellular and molecular body mass index (BMI)-related features in the IFP of OA patients. METHODS: Patients with knee OA (N = 155, 68% women, mean age 65 years, mean (SD) BMI 29.9 kg/m2 (5.7)) were recruited: IFP volume was determined by magnetic resonance imaging in 79 patients with knee OA, while IFPs and subcutaneous adipose tissue (SCAT) were obtained from 106 patients undergoing arthroplasty. Crown-like structures (CLS) were determined using immunohistochemical analysis. Adipocyte size was determined by light microscopy and histological analysis. Stromal vascular fraction (SVF) cells were characterized by flow cytometry. RESULTS: IFP volume (mean (SD) 23.6 (5.4) mm(3)) was associated with height, but not with BMI or other obesity-related features. Likewise, volume and size of IFP adipocytes (mean 271 pl, mean 1933 μm) was not correlated with BMI. Few CLS were observed in the IFP, with no differences between overweight/obese and lean individuals. Moreover, high BMI was not associated with higher SVF immune cell numbers in the IFP, nor with changes in their phenotype. No BMI-associated molecular differences were observed, besides an increase in TNFα expression with high BMI. Macrophages in the IFP were mostly pro-inflammatory, producing IL-6 and TNFα, but little IL-10. Interestingly, however, CD206 and CD163 were associated with an anti-inflammatory phenotype, were the most abundantly expressed surface markers on macrophages (81% and 41%, respectively) and CD163(+) macrophages had a more activated and pro-inflammatory phenotype than their CD163(-) counterparts. CONCLUSIONS: BMI-related features usually observed in SCAT and visceral adipose tissue could not be detected in the IFP of OA patients, a fat depot implicated in OA pathogenesis

Mesenchymal stem cell secretome reduces pain and prevents cartilage damage in a murine osteoarthritis model

Mesenchymal stem cells (MSCs) represent a promising biological therapeutic option as an osteoarthritis (OA)-modifying treatment. MSCs secrete factors that can counteract inflammatory and catabolic processes and attract endogenous repair cells. The effects of intra-articular injection of MSC secretome on OA-related pain, cartilage damage, subchondral bone alterations and synovial inflammation were studied in a mouse collagenase-induced OA model. The MSC secretome was generated by stimulating human bone-marrow-derived MSCs with interferon gamma (IFNγ) and tumour necrosis factor alpha (TNFα). 54 mice were randomly assigned to injections with i) MSC secretome from 20,000 MSCs, ii) 20,000 MSCs or iii) medium (control). Pain was assessed by hind limb weight distribution. Cartilage damage, subchondral bone volume and synovial inflammation were evaluated by histology. MSC-secretome- and MSC-injected mice showed pain reduction at day 7 when compared to control mice. Cartilage damage was more abundant in the control group as compared to healthy knees, a difference which was not found in knees treated with MSC secretome or MSCs. No effects were observed regarding synovial inflammation, subchondral bone volume or the presence of different macrophage subtypes. Injection of MSC secretome, similarly to injection of MSCs, resulted in early pain reduction and had a protective effect on the development of cartilage damage in a murine OA model. By using the regenerative capacities of the MSC-secreted factors, it will be possible to greatly enhance the standardisation, affordability and clinical translatability of the approach. This way, this biological therapy could evolve towards a true disease-modifying anti-osteoarthritic drug

Bone Marrow–Harvesting Technique Influences Functional Heterogeneity of Mesenchymal Stem/Stromal Cells and Cartilage Regeneration

Background: Connective tissue progenitors (CTPs) from native bone marrow (BM) or their culture-expanded progeny, often referred to as mesenchymal stem/stromal cells, represents a promising strategy for treatment of cartilage injuries. But the cartilage regeneration capacity of these cells remains unpredictable because of cell heterogeneity. Hypothesis: The harvest technique of BM may highly influence stem cell heterogeneity and, thus, cartilage formation because these cells have distinct spatial localization within BM from the same bone. Study Design: Controlled laboratory study. Methods: CTPs obtained from the femur of patients undergoing total hip replacement by 2 harvest techniques—BM aspiration and BM collection—after bone rasping were immunophenotyped by flow cytometry and evaluated for chondrogenic ability. The spatial localization of different CTP subsets in BM was verified by immunohistochemistry. Results: Cells from the BM after rasping were significantly more chondrogenic than the donor-matched aspirate, whereas no notable difference in their osteogenic or adipogenic potential was observed. The authors then assessed whether distinct immunophenotypically defined CTP subsets were responsible for the different chondrogenic capacity. Cells directly isolated from BM after rasping contained a higher percentage (mean, 7.2-fold) of CD45–CD2711CD561 CTPs as compared with BM aspirates. The presence of this subset in the harvested BM strongly correlated with chondrogenic ability, showing that CD2711CD561 cells are enriched in chondroprogenitors. Furthermore, evaluation of these CTP subsets in BM revealed that CD2711CD561 cells were localized in the bone-lining regions whereas CD2711CD56– cells were found in the perivascular regions. Since the iliac crest remains a frequent site of BM harvest for musculoskeletal regeneration, the authors also compared the spatial distribution of these subsets in trabeculae of femoral head and iliac crest and found CD2711CD561 bone-lining cells in both tissues. Conclusion: Chondrogenically distinct CTP subsets have distinct spatial localization in BM; hence, the harvest technique of BM determines the efficiency of cartilage formation. Clinical Relevance: The harvest technique of BM may be of major importance in determining the clinical success of BM mesenchymal stem/stromal cells in cartilage repair

Two independent proteomic approaches provide a comprehensive analysis of the synovial fluid proteome response to Autologous Chondrocyte Implantation

Background: Autologous chondrocyte implantation (ACI) has a failure rate of approximately 20%, but it is yet to be fully understood why. Biomarkers are needed that can pre-operatively predict in which patients it is likely to fail, so that alternative or individualised therapies can be offered. We previously used label-free quantitation (LF) with a dynamic range compression proteomic approach to assess the synovial fluid (SF) of ACI responders and non-responders. However, we were able to identify only a few differentially abundant proteins at baseline. In the present study, we built upon these previous findings by assessing higher-abundance proteins within this SF, providing a more global proteomic analysis on the basis of which more of the biology underlying ACI success or failure can be understood. Methods: Isobaric tagging for relative and absolute quantitation (iTRAQ) proteomic analysis was used to assess SF from ACI responders (mean Lysholm improvement of 33; n = 14) and non-responders (mean Lysholm decrease of 14; n = 13) at the two stages of surgery (cartilage harvest and chondrocyte implantation). Differentially abundant proteins in iTRAQ and combined iTRAQ and LF datasets were investigated using pathway and network analyses. Results: iTRAQ proteomic analysis confirmed our previous finding that there is a marked proteomic shift in response to cartilage harvest (70 and 54 proteins demonstrating ≥ 2.0-fold change and p < 0.05 between stages I and II in responders and non-responders, respectively). Further, it highlighted 28 proteins that were differentially abundant between responders and non-responders to ACI, which were not found in the LF study, 16 of which were altered at baseline. The differential expression of two proteins (complement C1s subcomponent and matrix metalloproteinase 3) was confirmed biochemically. Combination of the iTRAQ and LF proteomic datasets generated in-depth SF proteome information that was used to generate interactome networks representing ACI success or failure. Functional pathways that are dysregulated in ACI non-responders were identified, including acute-phase response signalling. Conclusions: Several candidate biomarkers for baseline prediction of ACI outcome were identified. A holistic overview of the SF proteome in responders and non-responders to ACI  has been profiled, providing a better understanding of the biological pathways underlying clinical outcome, particularly the differential response to cartilage harvest in non-responders

Glucosamine increases hyaluronic acid production in human osteoarthritic synovium explants

Background. Glucosamine (GlcN) used by patients with osteoarthritis was demonstrated to reduce pain, but the working mechanism is still not clear. Viscosupplementation with hyaluronic acid (HA) is also described to reduce pain in osteoarthritis. The synthesis of HA requires GlcN as one of its main building blocks. We therefore hypothesized that addition of GlcN might increase HA production by synovium tissue. Methods. Human osteoarthritic synovium explants were obtained at total knee surgery and pre-cultured for 1 day. The experimental conditions consisted of a 2 days continuation of the culture with addition of N-Acetyl-glucosamine (GlcN-Ac; 5 mM), glucosamine-hydrochloride (GlcN-HCl; 0.5 and 5 mM), glucose (Gluc; 0.5 and 5 mM). Hereafter HA production was measured in culture medium supernatant using an enzyme-linked binding protein assay. Real time RT-PCR was performed for hyaluronic acid synthase (HAS) 1, 2 and 3 on RNA isolated from the explants. Results. 0.5 mM

Performance of different three-dimensional scaffolds for in vivo endochondral bone generation

Contains fulltext : 136497.pdf (publisher's version ) (Open Access)In the context of skeletal tissue development and repair, endochondral ossification has inspired a new approach to regenerate bone tissue in vivo using a cartilage intermediate as an osteoinductive template. The aim of this study was to investigate the behavior of mesenchymal stem cells (MSCs) in regard to in vitro cartilage formation and in vivo bone regeneration when combined with different three-dimensional (3D) scaffold materials, i.e., hydroxyapatite/tricalcium phosphate (HA/TCP) composite block, polyurethane (PU) foam, poly(lactic-co-glycolic acid)/poly(epsilon-caprolactone) electrospun fibers (PLGA/PCL) and collagen I gel. To this end, rat MSCs were seeded on these scaffolds and chondrogenically differentiated in vitro for 4 weeks followed by in vivo subcutaneous implantation for 8 weeks. Nonetheless, the quality and maturity of in vivo ectopic bone formation appeared to be scaffold/material-dependent. Eight weeks of implantation was not sufficient to ossify the entire PLGA/PCL constructs, albeit a comprehensive remodeling of the cartilage had occurred. For HA/TCP, PU and collagen I scaffolds, more mature bone formation with rich vascularity and marrow stroma development could be observed. These data suggest that chondrogenic priming of MSCs in the presence of different scaffold materials allows the establishment of reliable templates for generating functional endochondral bone tissue in vivo without using osteoinductive growth factors. The morphology and maturity of bone formation

Quantitative evaluation of mechanical properties in tissue-engineered auricular cartilage

Tissue-engineering (TE) efforts for ear reconstruction often fail due to mechanical incompetency. It is therefore key for successful auricular cartilage (AUC) TE to ensure functional competency, that is, to mimic the mechanical properties of the native ear tissue. A review of past attempts to engineer AUC shows unsatisfactory functional outcomes with various cell-seeded biodegradable polymeric scaffolds in immunocompetent animal models. However, promising improvements to construct stability were reported with either mechanically reinforced scaffolds or novel two-stage implantation techniques. Nonetheless, quantitative mechanical evaluation of the constructs is usually overlooked, and such an evaluation of TE constructs alongside a benchmark of native AUC would allow real-time monitoring and improve functional outcomes of auricular TE strategies. Although quantitative mechanical evaluation techniques are readily available for cartilage, these techniques are designed to characterize the main functional components of hyaline and fibrous cartilage such as the collagen matrix or the glycosaminoglycan network, but they overlook the functional role of elastin, which is a major constituent of AUC. Hence, for monitoring AUC TE, novel evaluation techniques need to be designed. These should include a characterization of the specific composition and architecture of AUC, as well as mechanical evaluation of all functional components. Therefore, this article reviews the existing literature on AUC TE as well as cartilage mechanical evaluation and proposes recommendations for designing a mechanical evaluation protocol specific for AUC, and establishing a benchmark for native AUC to be used for quantitative evaluation of TE AUC

Considerations on the use of ear chondrocytes as donor chondrocytes for cartilage tissue engineering

Articular cartilage is often used for research on cartilage tissue engineering. However, ear cartilage is easier to harvest, with less donor-site morbidity. The aim of this Study was to evaluate whether adult human ear chondrocytes were capable of producing cartilage after expansion in monolayer culture. Cell yield per gram of cartilage was twice as high for ear than for articular cartilage. Moreover, ear chondrocytes proliferated faster. Cell proliferation could be further stimulated by the use of serum-free medium with Fibroblast Growth Factor 2 (FGF2) in stead of medium with 10% serum. To evaluate chondrogenic capacity, Multiplied chondrocytes were suspended in alginate and implanted subcutaneously in athymic mice. After 8 weeks the constructs demonstrated a proteoglycan-rich matrix that contained collagen type II. Constructs of ear chondrocytes showed a faint staining for elastin. Quantitative RT-PCR revealed that expression of collagen type II was 2-fold upregulated whereas expression of collagen type I was 2-fold down regulated in ear chondrocytes expanded in serum-free medium with FGF2 compared to serum-containing medium. Expression of alkaline phosphatase and collagen type X were low indicating the absence of terminal differentiation. We conclude that ear chondrocytes can be used as donor chondrocytes for cartilage tissue engineering. Furthermore, it may proof to be a promising alternative cell Source to engineer cartilage for articular repair