Sympathectomy aggravates subchondral bone changes during osteoarthritis progression in mice without affecting cartilage degeneration or synovial inflammation.

OBJECTIVE: Osteoarthritis (OA) pathogenesis involves the interaction of articular cartilage with surrounding tissues, which are innervated by tyrosine hydroxylase-positive (TH+) sympathetic nerve fibers suggesting a role of the sympathetic nervous system (SNS) during OA progression. We analyzed the effects of sympathectomy (Syx) in a murine OA model. METHODS: Peripheral Syx was generated by 6-hydroxydopamine (6-OHDA) injections in male C57BL/6 mice. OA was induced in wild-type (WT) and Syx mice by destabilization of the medial meniscus (DMM). TH+ fibers and splenic NE were analyzed to evaluate Syx efficiency. OA progression was examined by OARSI and synovitis scores and micro-CT. Expression of TH, α2A- and ß2-adrenergic receptors (AR), and activity of osteoblasts (ALP) and osteoclasts (TRAP) was investigated by stainings. RESULTS: Syx resulted in synovial TH+ fiber elimination and splenic NE decrease. Cartilage degradation and synovitis after DMM were comparably progressive in both WT and Syx mice. Calcified cartilage (CC) and subchondral bone plate (SCBP) thickness and bone volume fraction (BV/TV) increased in Syx mice due to increased ALP and decreased TRAP activities compared to WT 8 weeks after DMMWT and Syx mice developed osteophytes and meniscal ossicles without any differences between the groups. AR numbers decreased in cartilage but increased in synovium and osteophyte regions after DMM in both WT and Syx mice. CONCLUSION: Peripheral dampening of SNS activity aggravated OA-specific cartilage calcification and subchondral bone thickening but did not influence cartilage degradation and synovitis. Therefore, SNS might be an attractive target for the development of novel therapeutic strategies for pathologies of the subchondral bone.

The Matrilin-3 T298M mutation predisposes for post-traumatic osteoarthritis in a knock-in mouse model.

OBJECTIVE: The human matrilin-3 T303M (in mouse T298M) mutation has been proposed to predispose for osteoarthritis, but due to the lack of an appropriate animal model this hypothesis could not be tested. This study was carried out to identify pathogenic mechanisms in a transgenic mouse line by which the mutation might contribute to disease development. METHODS: A mouse line carrying the T298M point mutation in the Matn3 locus was generated and features of skeletal development in ageing animals were characterized by immunohistology, micro computed tomography, transmission electron microscopy and atomic force microscopy. The effect of transgenic matrilin-3 was also studied after surgically induced osteoarthritis. RESULTS: The matrilin-3 T298M mutation influences endochondral ossification and leads to larger cartilage collagen fibril diameters. This in turn leads to an increased compressive stiffness of the articular cartilage, which, upon challenge, aggravates osteoarthritis development. CONCLUSIONS: The mouse matrilin-3 T298M mutation causes a predisposition for post-traumatic osteoarthritis and the corresponding knock-in mouse line therefore represents a valid model for investigating the pathogenic mechanisms involved in osteoarthritis development.

Collagen IX deficiency leads to premature vascularization and ossification of murine femoral heads through an imbalance of pro- and antiangiogenic factors.

OBJECTIVE: The vascular invasion of cartilage is an essential process in the endochondral ossification of long bones. In contrast, vascularization of articular cartilage constitutes a pathological mechanism in the development of osteoarthritis. Polymorphisms of Col9a1 have been described as risk factors for hip osteoarthritis (OA) and the loss of collagen IX is known to lead to premature OA of the hip joint in mice but the underlying mechanism is so far unknown. DESIGN: To understand the contribution of collagen IX to OA development in the hip joint, we analyzed the early development of murine Col9a1-/- femoral heads between newborn stage and 16 weeks of age. RESULTS: We found significantly accelerated ossification of the femoral heads in the absence of collagen IX as well as premature vascular and osteoclast invasion, even though hypertrophic differentiation was delayed. The loss of collagen IX led to anatomically altered femoral heads lacking the epiphyseal tubercle. Interestingly, this region was found to contain highest levels of the antiangiogenic protein thrombospondin-1 (TSP-1). Hence, TSP-1 levels were strongly reduced in the Col9a1-/- femoral heads. In addition, antiangiogenic matrilin-1 was found to be decreased, while proangiogenic active MMP-9 levels were increased in the collagen IX deficient mice compared to wildtype controls. CONCLUSION: We conclude that collagen IX protects against premature vascularization and cartilage to bone transition in femoral heads by increasing the levels of antiangiogenic TSP-1 and matrilin-1 and decreasing the levels of proangiogenic active MMP-9.

Effect of different running modes on the morphological, biochemical, and mechanical properties of articular cartilage.

Mechanical loading plays an important role not solely in cartilage development, but also in cartilage degeneration. Its adaptation behavior to mechanical loading has not been clearly delineated. The aim of the study was to examine the effect of different running modes (with different muscle contraction types) on morphological, biochemical, and mechanical properties of articular cartilage in the knee of growing rats. Thirty-six female Sprague-Dawley rats were randomly assigned into a nonactive age-matched control (AMC), level (LEVEL), and 20° downhill (DOWN) running group (n = 12 each). Running groups were trained on a treadmill for 30 min/day, 5 days/week for 6 weeks. Immunohistochemical staining and analysis of expression for collagen II, collagen IX, cartilage oligomeric matrix protein (COMP), and matrilin-3, histomorphometry of femoral cartilage height and femoral COMP staining height, and indentation testing of tibial articular cartilage were performed. Rats subjected to downhill running showed a significantly (P = 0.015) higher COMP staining height and a tendentially (P = 0.084) higher cartilage height in the high-weight bearing area of femoral articular cartilage. Cartilage thickness, mechanical properties, and expression of cartilage network proteins in tibial cartilage remained unaffected by different running modes. Our data suggest that joint loading induced by eccentric muscle contractions during downhill running may lead to a site-specific adaptation.

Deformational behaviour of knee cartilage and changes in serum cartilage oligomeric matrix protein (COMP) after running and drop landing.

OBJECTIVE: To investigate (1) the effect of running and drop landing interventions on knee cartilage deformation and serum cartilage oligomeric matrix protein (COMP) concentration and (2) if the changes in cartilage volume correlate with the changes in serum COMP level. METHODS: Knee joint cartilage volume and thickness were determined using magnetic resonance imaging (MRI) as well as COMP concentration from serum samples before and after in vivo loading of 14 healthy adults (seven male and seven female). Participants performed different loading interventions of 30 min duration on three different days: (1) 100 vertical drop landings from a 73 cm high platform, (2) running at a velocity of 2.2m/s (3.96 km), and (3) resting on a chair. Blood samples were taken immediately before, immediately after and 0.5h, 1h, 2h and 3h post intervention. Pre- and post-loading coronal and axial gradient echo MR images with fat suppression were used to determine the patellar, tibial and femoral cartilage deformation. RESULTS: Serum COMP levels increased immediately after the running (+30.7%, pre: 7.3U/l, 95% confidence interval (CI): 5.6, 8.9, post: 9.1U/l, 95% CI: 7.2, 11.0, P=0.001) and after drop landing intervention (+32.3%, pre: 6.8U/l, 95% CI: 5.3, 8.4; post: 8.9U/l, 95% CI: 6.8, 10.9, P=0.001). Cartilage deformation was more pronounced after running compared to drop landing intervention, with being significant (volume: P=0.002 and thickness: P=0.001) only in the lateral tibia. We found a significant correlation (r(2)=0.599, P=0.001) between changes in serum COMP (%) and in cartilage volume (%) after the drop landing intervention, but not after running. CONCLUSIONS: In vivo exercise interventions differentially regulate serum COMP concentrations and knee cartilage deformations. The relation between changes in COMP and in cartilage volume seems to depend on both mechanical and biochemical factors.

Spatiotemporal distribution of thrombospondin-4 and -5 in cartilage during endochondral bone formation and repair.

During skeletal development most bones are first formed as cartilage templates, which are gradually replaced by bone. If later in life those bones break, temporary cartilage structures emerge to bridge the fractured ends, guiding the regenerative process. This bone formation process, known as endochondral ossification (EO), has been widely studied for its potential to reveal factors that might be used to treat patients with large bone defects. The extracellular matrix of cartilage consists of different types of collagens, proteoglycans and a variety of non-collagenous proteins that organise the collagen fibers in complex networks. Thrombospondin-5, also known as cartilage oligomeric matrix protein (TSP-5/COMP) is abundant in cartilage, where it has been described to enhance collagen fibrillogenesis and to interact with a variety of growth factors, matrix proteins and cellular receptors. However, very little is known about the skeletal distribution of its homologue thrombospondin-4 (TSP-4). In our study, we compared the spatiotemporal expression of TSP-5 and TSP-4 during postnatal bone formation and fracture healing. Our results indicate that in both these settings, TSP-5 distributes across all layers of the transient cartilage, while the localisation of TSP-4 is restricted to the population of hypertrophic chondrocytes. Furthermore, in fractured bones we observed TSP-4 sparsely distributed in the periosteum, while TSP-5 was absent. Last, we analysed the chemoattractant effects of the two proteins on endothelial cells and bone marrow stem cells and hypothesised that, of the two thrombospondins, only TSP-4 might promote blood vessel invasion during ossification. We conclude that TSP-4 is a novel factor involved in bone formation. These findings reveal TSP-4 as an attractive candidate to be evaluated for bone tissue engineering purposes.

Matrilin-3 mutations that cause chondrodysplasias interfere with protein trafficking while a mutation associated with hand osteoarthritis does not.

Several mutations in the extracellular matrix protein matrilin-3 cause a heterogeneous disease spectrum affecting skeletal tissues. We introduced three disease causing point mutations leading to single amino acid exchanges (R116W, T298M, C299S) in matrilin-3 and expressed the corresponding proteins in primary articular chondrocytes to elucidate pathogenic mechanisms at the cellular level. Expression levels, processing, and the secretion pattern of a mutation linked to hand osteoarthritis (T298M) were similar to the wildtype protein, whereas the two other mutants were poorly expressed and hardly detectable in supernatants of transiently transfected cells. Using immunofluorescence staining, we demonstrated that mutants R116W and C299S are retained and accumulate within the endoplasmatic reticulum (ER). Their further trafficking to the Golgi compartment seems to be disturbed, whereas T298M is secreted normally. In cells transfected with the wildtype and T298M constructs, a matrilin-3 containing filamentous network was formed surrounding the cells, whereas in the case of R116W and C299S such structures were completely absent. These observations are similar to those for mutations in the cartilage oligomeric matrix protein (COMP) leading to multiple epiphyseal dysplasia and pseudoachondroplasia suggesting that retention and accumulation of cartilage proteins in the ER might be a general mechanism involved in the pathogenesis of chondrodysplasias.

The structure of organometals determines cytotoxicity and alteration of calcium homeostasis in HL-60 cells.

There is increasing concern about the degradation and metabolisation as well as the biochemical mechanisms of action of organometallic compounds. They are known to be immunotoxic and/or neurotoxic. Because of their different toxic capacities, the development of a reliable correlation between molecular parameters and biochemical effects, which could be helpful in risk assessment, was an aim of this study. The tested organolead and -tin compounds decrease the viability of human cells in culture in a time- and concentration-dependent manner. Parabolic QSAR(1)(1) The abbreviations used are: TMT, trimethyltin chloride; TET, triethyltin bromide; TPT, tripropyltin chloride; TBT, tri- n-butyltin chloride; DBT, di- n-butyltin dichloride; TEL, triethyllead chloride; DEL, diethyllead dichloride; TML, trimethyllead chloride; TPhL, triphenyllead chloride; QSAR, quantitative structure-activity relationships; TSA, total surface area; MW(ion), ionic molecular weight; fMLP, N-formyl-L-methionyl-L-leucyl-L-phenylalanine; fluo-3, fluo-3 free acid; fluo-3 AM, fluo-3 acetoxymethyl ester; Me(2)SO, dimethyl sulfoxide; PLA(2), phospholipase A(2) (EC 3.1.1.4); FCS, fetal calf serum; HEPES, 4-(2-hydroxy-ethyl)-1-piperazineethanesulfonic acid; EGTA, [ethylene-bis(oxyethylenenitrilo)]tetraacetic acid; [Ca(2+)](i), cytosolic free Ca(2+) concentration models yield an adequate correlation between toxicity expressed as LC(50) and structural parameters like ionic molecular weight (MW(ion)) or total surface area (TSA). Two main chemical attributes of the organometals are probably responsible for such a parabolic relationship: the hydrophobic side chain and the polar metal atom. Furthermore, all tested organometal compounds evoke a persistent increase of the cytosolic free calcium concentration [Ca(2+)](i). This effect is mainly due to an influx from the extracellular space. Further results suggest that Ca(2+) enters the cell via opened calcium channels. Based on the essential role of Ca(2+) within cellular signalling, the perturbation of calcium homeostasis appears to be an important event in final cell killing by organometals and it is most likely that other biochemical mechanisms, e.g. activation of phospholipase A(2), are possibly mediated by an increase of [Ca(2+)](i).

Trigeminal nerve injury-induced thrombospondin-4 up-regulation contributes to orofacial neuropathic pain states in a rat model.

BACKGROUND: Injury to the trigeminal nerve often results in the development of chronic pain states including tactile allodynia, or hypersensitivity to light touch, in orofacial area, but its underlying mechanisms are poorly understood. Peripheral nerve injury has been shown to cause up-regulation of thrombospondin-4 (TSP4) in dorsal spinal cord that correlates with neuropathic pain development. In this study, we examined whether injury-induced TSP4 is critical in mediating orofacial pain development in a rat model of chronic constriction injury to the infraorbital nerve. METHODS: Orofacial sensitivity to mechanical stimulation was examined in a unilateral infraorbital nerve ligation rat model. The levels of TSP4 in trigeminal ganglia and associated spinal subnucleus caudalis and C1/C2 spinal cord (Vc/C2) from injured rats were examined at time points correlating with the initiation and peak orofacial hypersensitivity. TSP4 antisense and mismatch oligodeoxynucleotides were intrathecally injected into injured rats to see if antisense oligodeoxynucleotide treatment could reverse injury-induced TSP4 up-regulation and orofacial behavioural hypersensitivity. RESULTS: Our data indicated that trigeminal nerve injury induced TSP4 up-regulation in Vc/C2 at a time point correlated with orofacial tactile allodynia. In addition, intrathecal treatment with TSP4 antisense, but not mismatch, oligodeoxynucleotides blocked both injury-induced TSP4 up-regulation in Vc/C2 and behavioural hypersensitivity. CONCLUSIONS: Our data support that infraorbital nerve injury leads to TSP4 up-regulation in trigeminal spinal complex that contributes to orofacial neuropathic pain states. Blocking this pathway may provide an alternative approach in management of orofacial neuropathic pain states.

Thrombospondin-4 contributes to spinal cord injury-induced changes in nociception.

BACKGROUND: Our previous data have indicated that nerve injury-induced up-regulation of thrombospondin-4 (TSP4) proteins in dorsal spinal cord plays a causal role in neuropathic pain state development in a spinal nerve ligation model. To investigate whether TSP4 proteins also contribute to the development of centrally mediated changes in nociception after spinal cord injury (SCI), we investigated whether SCI induced TSP4 dysregulation, and if so, whether this change correlated with changes in nociception in a T9 spinal cord contusion injury model. METHODS: Behavioural sensitivity to mechanical, thermal stimuli and locomotor function recovery were tested blindly in SCI or sham rats post-injury. Intrathecal antisense or mismatch control oligodeoxynucleotides were used to treat SCI rats with nociceptive hyperreflexia, and Western blots were used to measure TSP4 protein levels in dorsal spinal cord samples. RESULTS: SCI induced below-level hindpaw hypersensitivity to stimuli. TSP4 protein levels are up-regulated in dorsal spinal cord of SCI rats with nociceptive hyperreflexia, but not in SCI rats without nociceptive hyperreflexia. There was no significant difference in motor function recovery post-injury between SCI rats with or without nociceptive hyperreflexia. Intrathecal treatment with TSP4 antisense, but not mismatch control, oligodeoxynucleotides led to reversal of injury-induced TSP4 up-regulation and nociceptive hyperreflexia in SCI rats. CONCLUSIONS: SCI leads to TSP4 up-regulation in lumbar spinal cord that may play a critical role in mediating centrally mediated behavioural hypersensitivity. Blocking this pathway may be helpful in management of SCI-induced changes in nociception.

Combined role of type IX collagen and cartilage oligomeric matrix protein in cartilage matrix assembly: cartilage oligomeric matrix protein counteracts type IX collagen-induced limitation of cartilage collagen fibril growth in mouse chondrocyte cultures.

OBJECTIVE: Defects in the assembly and composition of cartilage extracellular matrix are likely to result in impaired matrix integrity and increased susceptibility to cartilage degeneration. The aim of this study was to determine the functional interaction of the collagen fibril-associated proteins type IX collagen and cartilage oligomeric matrix protein (COMP) during cartilage matrix formation. METHODS: Primary chondrocytes from mice deficient in type IX collagen and COMP (double-deficient) were cultured in monolayer or alginate beads. Anchorage of matrix proteins, proteoglycan and collagen content, collagen crosslinks, matrix metalloproteinase activity, and mechanical properties of the matrix were measured. Electron microscopy was used to study the formation of fibrillar structures. RESULTS: In cartilage lacking both type IX collagen and COMP, matrilin 3 showed decreased matrix anchorage. Less matrilin 3 was deposited in the matrix of double-deficient chondrocytes, while larger amounts were secreted into the medium. Proteoglycans were less well retained in the matrix formed in alginate cultures, while collagen deposition was not significantly affected. Electron microscopy revealed similar cartilage collagen fibril diameters in the cultures of double-deficient and wild-type chondrocytes. In contrast, a larger fibril diameter was observed in the matrix of chondrocytes deficient in only type IX collagen. CONCLUSION: Our results show that type IX collagen and COMP are involved in matrix assembly by mediating the anchorage and regulating the distribution of other matrix macromolecules such as proteoglycans and matrilins and have counteracting effects on collagen fibril growth. Loss of type IX collagen and COMP leads to matrix aberrations that may make cartilage more susceptible to degeneration.

The Uromodulin C744G mutation causes MCKD2 and FJHN in children and adults and may be due to a possible founder effect.

Autosomal dominant medullary cystic kidney disease type 2 (MCKD2) is a tubulo-in terstitial nephropathy that causes renal salt wasting, hyperuricemia, gout, and end-stage renal failure in the fifth decade of life. This disorder was described to have an age of onset between the age of 20-30 years or even later. Mutations in the Uromodulin (UMOD) gene were published in patients with familial juvenile hyperuricemic nephropathy (FJHN) and MCKD2. Clinical data and blood samples of 16 affected individuals from 11 different kindreds were collected. Mutational analysis of the UMOD gene was performed by exon polymerase chain reaction (PCR) and direct sequencing. We found the heterozygous C744G (Cys248Trp) mutation, which was originally published by our group, in an additional four kindreds from Europe and Turkey. Age of onset ranged from 3 years to 39 years. The phenotype showed a variety of symptoms such as urinary concentration defect, vesicoureteral reflux, urinary tract infections, hyperuricemia, hypertension, proteinuria, and renal hypoplasia. Haplotype analysis showed cosegragation with the phenotype in all eight affected individuals indicating that the C744G mutation may be due to a founder effect. Moreover, we describe a novel T229G (Cys77Gly) mutation in two affecteds of one kindred. Three of the affected individuals were younger than 10 years at the onset of MCKD2/FJHN. Symptoms include recurrent urinary tract infections compatible with the published phenotype of the Umod knockout mouse model. This emphasizes that MCKD2 is not just a disease of the young adult but is also relevant for children.

Galectin-3 is induced in rheumatoid arthritis synovial fibroblasts after adhesion to cartilage oligomeric matrix protein.

BACKGROUND: Galectin-3 is expressed in the synovial tissue of patients with rheumatoid arthritis (RA), particularly at sites of joint destruction. OBJECTIVE: To explore the possibilities that galectin-3 is induced either by proinflammatory cytokines or by adhesion to cartilage components. METHODS: Cell culture plates were coated with fibronectin, collagens I-VI, or cartilage oligomeric matrix protein (COMP), and the suspended cells were then added. The medium was changed after 1 hour at 37 degrees C. Adherent cells were further incubated for 18 hours in the presence or absence of tumour necrosis factor alpha (TNF alpha) or interleukin 1 beta. Cells were pretreated with murine IgG1, anti-CD29, -CD51, -CD61 (integrins), or -CD3 monoclonal antibodies and transferred to culture plates coated with COMP. Adherent cells were counted by light microscopy. The expression of intracellular galectin-3, or cell surface CD29, CD51, and CD61 was determined by flow cytometry before and after adhesion. RESULTS: Four times more RA synovial fibroblasts (SF) than osteoarthritis SF adhered to COMP. RA SF presented more cell surface integrins, and monoclonal antibodies against CD51 inhibited the adhesion to COMP by 80%. TNF alpha reduced the expression of CD61 and the adhesion to COMP, but did not reverse the adhesion once it had taken place. The adhesion of RA SF to COMP was found to increase the intracellular level of galectin-3. In contrast, intracellular galectin-3 decreased after exposure to TNF alpha. CONCLUSION: The increase of galectin-3 occurs after adhesion to COMP, and the alpha V beta 3 receptor (CD51/CD61) has a pivotal role in this process.

Cartilage oligomeric matrix protein (COMP) and collagen IX are sensitive markers for the differentiation state of articular primary chondrocytes.

Primary chondrocytes dedifferentiate in serial monolayer with respect to their morphological and biosynthetic phenotype. They change from a round to a flattened fibroblast-like shape, and collagen I is secreted instead of the cartilage-specific collagen II. We analysed in detail the time course of dedifferentiation of mature bovine articular chondrocytes in monolayer for up to 32 weeks. Assessment of RNA expression by reverse transcription-PCR led to the identification of two novel phenotypical markers, the cartilage oligomeric matrix protein (COMP) and collagen IX, which are down-regulated faster than the widely accepted marker, collagen II. The different kinetics of COMP and collagen expression suggest differential regulation at the level of transcription. Immunostaining and metabolic labelling experiments confirmed the switch in the collagen expression pattern and the rapid down-regulation of de novo synthesis of COMP and collagen IX. Culture of chondrocytes in a three-dimensional matrix is known to stabilize the chondrocytic phenotype. We maintained cells for up to 28 weeks in an alginate bead system, which prevented dedifferentiation and led to a stabilization of collagen and COMP expression. Immunohistochemical analysis of the alginate beads revealed a similar distribution of matrix proteins to that found in vivo. Chondrocytes were transferred after a variable length of monolayer culture into the alginate matrix and the potential for redifferentiation was investigated. The re-expression of COMP and collagen IX was differentially regulated. The expression of COMP was re-induced within days after transfer into the three-dimensional matrix, while the expression of collagen IX was irreversibly down-regulated. In summary, these results demonstrate that the potential for redifferentiation decreases with increasing length of monolayer culture and show that the alginate bead system represents an attractive in vitro model to study the chondrocyte de- and re-differentiation processes, as well as extracellular matrix assembly.

Comparison of long-term transgene expression after non-viral and adenoviral gene transfer into primary articular chondrocytes.

Different gene transfer approaches to achieve long-term transgene expression in cultured primary bovine chondrocytes were compared using enhanced green fluorescent protein (EGFP) as a reporter. Transduction with a high-capacity adenoviral vector was 82% efficient when analysed by fluorescence microscopy, while up to 42% of plasmid-transfected cells were EGFP positive with FuGene as a transfection reagent. Rapid dominant marker selection of plasmid-transfected cells was achieved in monolayer culture. With either method of gene transfer, a high proportion of the chondrocytes remained transgene positive during prolonged alginate culture. Transgene transcription in single cells was quantified with a confocal laser scanning microscope. Detection of EGFP expression was more sensitive with this method, identifying more transgene-expressing cells than conventional fluorescence microscopy. Long-term EGFP expression was higher in adenovirally transduced chondrocytes embedded in alginate as compared to plasmid-transfected cells cultured in monolayer or in alginate. Both the adenoviral and the plasmid-based approach appear suited for studies of the molecular and cellular mechanisms by which mutations in cartilage matrix proteins cause disease.