Application of Adipose Stem Cells in 3D Nerve Guidance Conduit Prevents Muscle Atrophy and Improves Distal Muscle Compliance in a Peripheral Nerve Regeneration Model

BACKGROUND

Peripheral nerve injuries (PNIs) represent a significant clinical problem, and standard approaches to nerve repair have limitations. Recent breakthroughs in 3D printing and stem cell technologies offer a promising solution for nerve regeneration. The main purpose of this study was to examine the biomechanical characteristics in muscle tissue distal to a nerve defect in a murine model of peripheral nerve regeneration from physiological stress to failure.

METHODS

In this experimental study, we enrolled 18 Wistar rats in which we created a 10 mm sciatic nerve defect. Furthermore, we divided them into three groups as follows: in Group 1, we used 3D nerve guidance conduits (NGCs) and adipose stem cells (ASCs) in seven rats; in Group 2, we used only 3D NGCs for seven rats; and in Group 3, we created only the defect in four rats. We monitored the degree of atrophy at 4, 8, and 12 weeks by measuring the diameter of the tibialis anterior (TA) muscle. At the end of 12 weeks, we took the TA muscle and analyzed it uniaxially at 10% stretch until failure.

RESULTS

In the group of animals with 3D NGCs and ASCs, we recorded the lowest degree of atrophy at 4 weeks, 8 weeks, and 12 weeks after nerve reconstruction. At 10% stretch, the control group had the highest Cauchy stress values compared to the 3D NGC group (0.164 MPa vs. 0.141 MPa, p = 0.007) and the 3D NGC + ASC group (0.164 MPa vs. 0.123 MPa, p = 0.007). In addition, we found that the control group (1.763 MPa) had the highest TA muscle stiffness, followed by the 3D NGC group (1.412 MPa), with the best muscle elasticity showing in the group in which we used 3D NGC + ASC (1.147 MPa). At failure, TA muscle samples from the 3D NGC + ASC group demonstrated better compliance and a higher degree of elasticity compared to the other two groups (p = 0.002 and p = 0.008).

CONCLUSIONS

Our study demonstrates that the combination of 3D NGC and ASC increases the process of nerve regeneration and significantly improves the compliance and mechanical characteristics of muscle tissue distal to the injury site in a PNI murine model.

POS0446 Arp2/3 AS A Lasp1 INTERACTION PARTNER REGULATES CELL-TO-CELL CONTACT FORMATION OF FIBROBLAST-LIKE SYNOVIOCYTES IN RA

Background

In rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) undergo a stable transformation resulting in an aggressive phenotype mediating cartilage damage by increased levels of adhesion molecules. In this context, Lasp1 and the Arp2/3 complex are of interest because they modulate actin organization and focal adhesion turnover.

Objectives

In this study, the effects of Arp2/3 on cadherin-11 mediated cell-to-cell contact formation have been investigated using the arthritic hTNFtg mouse model.

Methods

Expression levels of Lasp1 and Arp2/3 protein complex were investigated in synovial tissue of wild type (wt) and hTNFtg hind paws by immunohistochemistry. Primary FLS were analysed, respectively and co-immunoprecipitation experiments were performed. In addition, lasp1-/- mice were interbred with hTNFtg animals and offspring were evaluated for disease progression and joint destruction. To further study the role of Arp2/3 in the function of the cadherin-11 adhesion complex, the effects of an Arp2/3 inhibitor (CK666) on cell-to-cell contact formation in FLS derived from hTNFtg and lasp1-/-hTNFtg mice were investigated by stainings. To assess signaling pathway activation, cells were stimulated with the growth factor PDGF.

Results

Upregulated Lasp1 levels were found in synovial tissue and FLS of hTNFtg compared to wt mice. Assays showed that Arp2/3 is part of the adherens junction (AJ) machinery in FLS although Arp2/3 expression levels were not changed between the genotypes. In vivo evaluation of lasp1-/-hTNFtg mice revealed a milder arthritis score, less cartilage degradation and reduced FLS attachment to articular cartilage compared to hTNFtg mice. In vitro, the loss of Lasp1 led to clear alterations in AJ arrangement indicated by altered β-catenin pattern. As expected, β-catenin expression was mainly located at adhesion sites between adjacent cells. In hTNFtg FLS, these structures were characterized by a zipper-like pattern. In contrast, these structures were disrupted in lasp1-/-hTNFtg FLS. Interestingly, CK666 induced zipper-like structures in hTNFtg FLS comparable to the pattern found in lasp1-/-hTNFtg cells. Furthermore, lasp1-/-hTNFtg FLS showed decreased Src phosphorylation following PDGF stimulation in comparison to hTNFtg FLS.

Conclusion

Lasp1 represents an interesting target involved in RA-caused joint destruction, because its loss results in significantly reduced cartilage destruction and altered FLS contacts mediated by Arp2/3.

Disclosure of Interests

None declared.

AB0089 INTEGRIN α11β1 DEFICIENCY AFFECTS THE COURSE OF DISEASE IN THE ARTHRITIC hTNFtg MOUSE

Background

Rheumatoid arthritis (RA) is an autoimmune disorder conducted by fibroblast-like synoviocytes (FLS), which acquire a tumor-like phenotype causing irreversible cartilage and bone damage. FLS attache to the extracellular matrix (ECM) invading the joints, a process mediated by integrins. Integrins are transmembrane proteins regulating several cell functions like cell migration, cell proliferation, tissue invasion and cytokine expression – key mechanisms during the pathogenesis of RA. The collagen-binding Integrin α11β1 (α11) is expressed on FLS mediating their adhesion to the ECM and in this study, we analysed its implication in RA.

Objectives

We examined the pathogenesis of RA in a murine arthritis model (hTNFtg) lacking α11 to analyze its contribution to joint destructions and the disease course.

Methods

Expression levels of α11 were analysed by Western Blot and immunofluorescence staining using FLS and synovial tissue of patients with RA and hTNFtg mice in comparison to their respective controls. Crossbreeding hTNFtg with α11 deficient (itga11-/-) mice enabled us to evaluate arthritis progression using clinical parameters like paw swelling and grip strength. Inflammation area and cartilage damage were quantified by histomorphological techniques such as toluidine blue staining of in paraffin-embedded sections from hind paws. Bone erosion was visualized by µCT imaging and quantification of the bone volume in the tarsal bone area.

Results

High expression levels of α11 could be detected in hTNFtg and human RA samples in comparison to their controls. The progression of arthritis in itga11-/-hTNFtg was slower and less severe in comparison to hTNFtg mice, visible in a stronger grip strength and reduced paw swelling at the same timepoint. The histomorphology analysis confirmed these results showing higher cartilage area (3.21% vs 5.22%, p < 0.05), less cartilage destruction (51.73% vs 35.65%, p < 0.05) and reduced inflammation (28.28% vs 12.00%) in itga11-/-hTNFtg compared to the hTNFtg mice. Also, the quantification of the tarsal bone area revealed a higher bone volume (77.94% vs 84.92%, p < 0.01) in itga11-/-hTNFtg.

Conclusion

This study showed the important role of α11 in the progression of joint destruction as it is highly expressed in hTNFtg mice and in human synovial tissue of patients with RA. Its absence results in less severe arthritis progression and joint destruction, therefore a possible and interesting target for RA treatment.

Disclosure of Interests

None declared

MMP-9 mediated Syndecan-4 shedding correlates with osteoarthritis severity

OBJECTIVE

Osteoarthritis (OA) is a degenerative joint disease inducing the degradation of the articular cartilage. Syndecan-4 (Sdc4) is a heparan sulfate proteoglycan, expressed under inflammatory conditions and by chondrocytes during OA. Little is known about Sdc4 shedding and its regulation in OA. Therefore, we investigated the regulation of Sdc4 shedding and underlying shedding mechanisms under OA conditions.

DESIGN

Articular cartilage, serum, synovial fluid and synovial membrane from OA patients with different radiological severity were analyzed. ELISA, RT-qPCR and IHC for Sdc4, MMP-2 and -9 were performed. MMP inhibitors and siRNA were evaluated for their effect on Sdc4 shedding by ELISA and on IL-1 signaling by western blot (pERK/ERK).

RESULTS

Shed Sdc4 was increased in synovial fluid of OA patients, but not in the serum and is a good predictor (AUC = 0.72) for OA severity with a sensitivity of 67.5% and specificity 65.2%. MMP-9, but not MMP-2, was increased in cartilage and synovial membrane at mRNA levels and in the synovial fluid at protein levels. Shed Sdc4 correlated with the amount of MMP-9 in synovial fluid. Further, the inhibition and knock-down of MMP-9 decreased the amount of shed Sdc4 in vitro. Increased Sdc4 shedding resulted in less phosphorylation of ERK upon IL-1β stimulation.

CONCLUSION

Shed Sdc4 might be a good prognostic biomarker for OA mediated cartilage degradation. MMP-9 seems to be the relevant sheddase for Sdc4 under OA conditions, desensitizing chondrocytes towards IL-1 signaling.

An altered heparan sulfate structure in the articular cartilage protects against osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is a progressive degenerative disease of the articular cartilage caused by an unbalanced activity of proteases, cytokines and other secreted proteins. Since heparan sulfate (HS) determines the activity of many extracellular factors, we investigated its role in OA progression.

METHODS

To analyze the role of the HS level, OA was induced by anterior cruciate ligament transection (ACLT) in transgenic mice carrying a loss-of-function allele of Ext1 in clones of chondrocytes (Col2-rtTA-Cre;Ext1e2fl/e2fl). To study the impact of the HS sulfation pattern, OA was surgically induced in mice with a heterozygous (Ndst1+/-) or chondrocyte-specific (Col2-Cre;Ndst1fl/fl) loss-of-function allele of the sulfotransferase Ndst1. OA progression was evaluated using the OARSI scoring system. To investigate expression and activity of cartilage degrading proteases, femoral head explants of Ndst1+/- mutants were analyzed by qRT-PCR, Western Blot and gelatin zymography.

RESULTS

All investigated mouse strains showed reduced OA scores (Col2-rtTA-Cre;Ext1e2fl/e2fl: 0.83; 95% HDI 0.72-0.96; Ndst1+/-: 0.83, 95% HDI 0.74-0.9; Col2-Cre;Ndst1fl/fl: 0.87, 95% HDI 0.76-1). Using cartilage explant cultures of Ndst1 animals, we detected higher amounts of aggrecan degradation products in wildtype samples (NITEGE 4.24-fold, 95% HDI 1.05-18.55; VDIPEN 1.54-fold, 95% HDI 1.54-2.34). Accordingly, gelatin zymography revealed lower Mmp2 activity in mutant samples upon RA-treatment (0.77-fold, 95% HDI: 0.60-0.96). As expression of major proteases and their inhibitors was not altered, HS seems to regulate cartilage degeneration by affecting protease activity.

CONCLUSION

A decreased HS content or a reduced sulfation level protect against OA progression by regulating protease activity rather than expression.

THU0435 CALCIUM PYROPHOSPHATE DIHYDRATE (CPPD) CRYSTALS BUT NOT BASIC CALCIUM PHOSPHATE (BCP) CRYSTALS INDUCE SYNDECAN-4 EXPRESSION IN CARTILAGE

Background:

Chondrocalcinosis is a painful rheumatic condition caused by the deposition of calcium pyrophosphate dihydrate crystals (CPPD) in joint tissues, and especially in cartilage. It is known that CPPD crystals cause inflammation and degenerative changes in joint, but the underlying mechanisms remain poorly understood. In particular, nothing is known about how these crystals regulates transmembrane heparan sulphate proteoglycans (HSPGs). Our attention focused on one family of HSPGs called syndecans as they have important roles both as adhesion molecules, by mediating chondrocyte-extracellular matrix interactions, and as modulators of intracellular signaling triggered by cytokines and growth factors.

Objectives:

The aim of this study was to evaluate how CPPD crystals modulates syndecan expression in chondrocytes and in cartilage, and how this modulation can be ultimately linked to cartilage damage during chondrocylcinosis.

Methods:

Murine chondrocitic ATDC5 cells were stimulated with 0,1 ng/ml CPPD crystals or with 0,1 ng/ml basic-calcium phosphate crystals (BCP), a family of calcium-containing crystals found in other rheumatic conditions such as osteoarthritis (OA). Cytotoxicity was evaluated by lactate dehydrogenase (LDH) release in the supernatant at 30 minutes, and 3, 6, 24 hours after stimulation. At the same time-points, mRNA expression levels of syndecans (Synd-1, -2, -3, -4) and of matrix-degrading enzymes (Mmp-3, -9, -13; Adamts-4, -5) was analysed by qRT-PCR. Finally, Syndecan-4 protein expression was studied by immunohistochemistry (IHC) in cartilage samples of patients with chondrocalcinosis and in samples of patients with severe OA without chondrocalcinosis as control.

Results:

LDH assay revealed no increased cytotoxicity by CPPD or BCP at any time-point. qRT-PCR indicated that CPPD crystals but not BCP crystals induced Synd-2 and -3 upregulation at 30 minutes after stimulation and Synd-4 upregulation at 3 hours, while no modulation of syndecans was seen at later time-points. CPPD also induced Adamts-4 expression at 3 hours after stimulation, and Mmp-9 expression at 3 and 6 hours. The expression of the other matrix-degrading enzymes was not affected. Human chondrocalcinosis cartilage exhibited enhanced Synd-4 expression compared to severe OA cartilage containing BCP calcification. Interestingly, Synd-4 expression was observed in the extracellular matrix but not on cell membrane, suggesting that maybe Synd-4 undergoes shedding (Figure 1).

Figure 1.

Representative Synd-4 IHC in control patients (Ctrl, severe OA) and chondrocalcinosis patients (CPPD). Note increased Synd-4 expression in extracellular matrix of CPPD patients compared to Ctrl ones.

Conclusion:

BCP and CPPD crystals seem to trigger differential effects in terms of modulation of syndecans in chondrocitic cells. CPPD crystals induce Synd-4 and Adamts-4 and Mmp-9 which are not induced by BCP crystals. It remains to be clarified whether the two events are interlinked. In particular, further studies are required to investigate if Adamts-4 and Mmp-9 are involved in Synd-4 shedding or if vice versa Synd-4 regulates Adamts-4 and Mmp-9 activation and downstream cartilage breakdown in chondrocalcinosis.

Disclosure of Interests: :

Sonia Nasi: None declared, Jessica Bertrand Grant/research support from: Pfizer, Speakers bureau: Pfizer, Miriam Bollmann: None declared, Richard Stange: None declared, Thomas Pap: None declared

Targeting β-catenin dependent Wnt signaling via peptidomimetic inhibitors in murine chondrocytes and OA cartilage

OBJECTIVE

The canonical Wnt signaling pathway has been shown to be involved in regulating chondrocyte hypertrophic differentiation during Osteoarthritis (OA). The aim of this study was to test the therapeutic potential of two stapled peptide canonical Wnt inhibitors - SAH-Bcl9 and StAx-35R - in preventing Wnt induced cartilage changes in OA.

METHODS

Primary neonatal murine chondrocytes and cartilage explants from OA patients undergoing total joint replacement for knee OA, were used for microscopy to determine matrix and cell penetrating capacity of fluorescein isothiocyanate FITC-tagged SAH-Bcl9 and StAx-35R peptides. T cell factor/lymphoid enhancer-binding factor (TCF/LEF) reporter assays were used to monitor the inhibition of Wnt3a induced β-catenin signaling by each peptide. Changes in chondrocyte phenotypic marker gene expression were analyzed by qRT PCR.

RESULTS

Both peptides localized intercellular in primary murine chondrocytes and cartilage explants. They inhibited Wnt3a induced TCF/LEF promoter activity in primary murine chondrocytes. Both inhibitors did not rescue Wnt3a altered expression of chondrocyte phenotypic genes (Sox9, Col2a1, Acan) and hypertrophy marker gene (Col10a1) at high doses (100 ng/ml). Upon application of 10 ng/ml Wnt3a, StAx-35R partially reversed the Wnt effect on Sox9 and Col2a1 gene expression. Both peptides, however, reversed the downregulation of SOX9 and aggrecan (ACAN), and decrease of COL10A1 gene expression in preserved human OA cartilage explants.

CONCLUSION

These data indicate that blockade of canonical Wnt signaling might be a therapeutic strategy to treat early OA cases and protect further cartilage degradation by preventing chondrocyte hypertrophic differentiation.

Chondrocyte secretome: a source of novel insights and exploratory biomarkers of osteoarthritis

The extracellular matrix (ECM) of articular cartilage is comprised of complex networks of proteins and glycoproteins, all of which are expressed by its resident cell, the chondrocyte. Cartilage is a unique tissue given its complexity and ability to resist repeated load and deformation. The mechanisms by which articular cartilage maintains its integrity throughout our lifetime is not fully understood, however there are numerous regulatory pathways known to govern ECM turnover in response to mechanical stimuli. To further our understanding of this field, we envision that proteomic analysis of the secretome will provide information on how the chondrocyte remodels the surrounding ECM in response to load, in addition to providing information on the metabolic state of the cell. In this review, we attempt to summarize the recent mass spectrometry-based proteomic discoveries in healthy and diseased cartilage and chondrocytes, to facilitate the discovery of novel biomarkers linked to degenerative pathologies, such as osteoarthritis (OA).

The role of stromal cells in inflammatory bone loss

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation, local and systemic bone loss and a lack of compensatory bone repair. Fibroblast-like synoviocytes (FLS) are the most abundant cells of the stroma and a key population in autoimmune diseases such as RA. An increasing body of evidence suggests that these cells play not only an important role in chronic inflammation and synovial hyperplasia, but also impact bone remodelling. Under inflammatory conditions FLS release inflammatory cytokines, regulate bone destruction and formation and communicate with immune cells to control bone homeostasis. Other stromal cells, such as osteoblasts and terminally differentiated osteoblasts, termed osteocytes, are also involved in the regulation of bone homeostasis and are dysregulated during inflammation. This review highlights our current understanding of how stromal cells influence the balance between bone formation and bone destruction. Increasing our understanding of these processes is critical to enable the development of novel therapeutic strategies with which to treat bone loss in RA.

Articular cartilage calcification of the hip and knee is highly prevalent, independent of age but associated with histological osteoarthritis: evidence for a systemic disorder

OBJECTIVES

Based on the concept of a systemic predisposition for articular cartilage calcification (CC), the aim of this study was to determine the prevalence and amount of bilateral CC of hip and knee joints in an unselected sample cohort by high-resolution digital contact radiography (DCR) and to analyze the association of CC with histological OA.

METHODS

Both hip and knee joints of 87 donors (48 m and 39 f; mean age 62) were analyzed by DCR in this post-mortem study of an unselected cohort of donors. Histological OA (OARSI) of the main load bearing area of femoral heads and medial femoral condyles was determined.

RESULTS

The prevalence of CC of the femoral head was 96.6%, of the knee 94.3%. Bilateral calcification was detected in 79.3% of hips and 86.2% of knees. Concomitant CC of all four joints was detected in 69.0% of donors. There was no difference between the amount of CC of hips and knees (P = 0.47). The amount of CC of any given hip or knee correlated with that of the contralateral hip (r_s = 0.54, P < 0.001) or knee (r_s = 0.50, P < 0.001). There was a correlation between the amount of CC and histological OA (hips r_s = 0.48, P < 0.001, knees r_s = 0.30, P = 0.004), but not between CC and age (hips r_s = -0.09, P = 0.42; knees r_s = 0.10, P = 0.34).

CONCLUSIONS

These data support the concept that articular CC occurs as the result of a systemic disorder. CC appears to be an early element of hip and knee OA pathogenesis independent of age.

[Fibroblasts as pathogenic cells in rheumatic inflammation]

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovitis, synovial hyperplasia and progressive degeneration of affected joints. These processes are mediated by cells of the immune system as well as by synovial fibroblasts (RASF) originating from the lining layer of the synovium. In this scenario RASFs display an activated phenotype: they show an altered expression of adhesion molecules which allows attachment to articular cartilage and by synthesis of proteases they mediate progressive cartilage and bone destruction. Furthermore, they produce various cytokines and chemokines, which are essential for promoting the inflammatory response. In recent years it has become evident that RASFs not only passively respond to the proinflammatory milieu in the joints of RA patients but also actively contribute by the overproduction of several cytokines and chemokines. These proinflammatory cytokines trigger the transformation of RASFs into an aggressive and invasive phenotype. Additionally, the primarily altered genuine RASFs are actively involved in the recruitment and activation of immune cells. Taken together, they are key players in the development of the well-known chronic, destructive inflammatory response in joints affected by RA.

"Inverse wrap": an improved implantation technique for virus-transduced synovial fibroblasts in the SCID mouse model for rheumatoid arthritis

Abstract The SCID mouse model for rheumatoid arthritis (RA) is an established and reliable approach to examining the distinct mechanisms operative in RA synovium, and evaluating novel gene therapy strategies. However, serum concentrations of circulating gene therapy products following gene transfer are frequently too low to allow detection. This problem stimulated us to develop a novel implantation technique to improve the yield of these soluble gene products. Synovial fibroblasts from patients with RA were cultured, passaged, and transduced with Ad5 sTNFRp55:Ig. sTNFRp55:Ig production was confirmed by ELISA, and then cells were implanted into SCID mice using a novel implantation strategy in which pieces of human cartilage were engrafted into a fibroblast-saturated inert sponge. Thereafter, the sponges were implanted under the skin of the mice instead of under the kidney capsule, as in the original approach, allowing co-implantation of larger pieces of cartilage together with higher numbers of adenovirus-transduced RA synovial fibroblasts. The improved implantation technique not only resulted in a reduction in the number of mice needed in each experiment by approximately 60%, and a reduction of the time taken for surgery by about 50%, but also considerably enhanced the serum concentrations of the gene product sTNFRp55-Ig, allowing detection of the soluble TNF receptor p55 by standard ELISA. In summary, the improved implantation technique for the SCID mouse model for RA results in more economic animal treatment, and facilitates the detection and quantification of circulating gene products following adenovirus-based gene transfer into synovial fibroblasts.