Aim

Aim of this study is to present the first clinical trial on an antibiotic-loaded fast-resorbable hydrogel coating*, in patients undergoing internal osteosynthesis for closed fractures.

Aim

Infection remains among the first reasons of failure of joint prosthesis. According to various preclinical reports, antibacterial coatings of implants may prevent bacterial adhesion and biofilm formation. Aim of this study is to present the first clinical trial on an antibiotic-loaded fast-resorbable hydrogel coating*, in patients undergoing hip or knee prosthesis.

Toll-like receptors (TLRs) are crucial components of the immune system that recognize microbial infection and trigger anti-microbial host defense responses. Gram positive bacteria are causative factors of bone infections, as they alter the balance of coordinated activities during bone remodeling, stimulating osteoclastogenesis. The aim of the study was to investigate whether genetic variation in TLR2 and TLR4 genes predisposes to bone infections’ susceptibility.

One hundred and twenty patients with bone infections (osteomyelitis) and 200 healthy controls were genotyped for two single nucleotide polymorphisms (SNPs), R753Q [A/G] in TLR2 gene and T399I [C/T] in TLR4 gene. DNA was extracted from whole blood and the above SNPs were typed with PCR-RFLP (Polymerase Chain Reaction- Restriction Fragment Length Polymorphism) method for genotype identification. All patients were infected by Gram-positive bacteria, predominantly Staphylococcus aureus. Statistical analysis was carried out using the chi-square test.

We observed a significantly increased frequency in patients carrying the GA genotype of TLR2 R753Q polymorphism compared to controls (p<0.05). We also found that the A allele was more common in patients than in controls. All individuals carrying the A allele were heterozygous for this variant, while homozygous mutant individuals were not detected in the patients and the control group. In contrast, we found that the TLR4 T399I [C/T] SNP was similarly distributed among the two groups (patients and controls). The mechanism through which TLR2 mediates its effect in bone infections is under investigation.

A significant difference was observed in the genotype frequency of TLR2 R753Q [A/G] polymorphism in patients, suggesting that genetic variability in TLR2 gene may be associated with susceptibility to osteomyelitis in response to bacterial invasion in the bone.

Report of a case of migrating periprosthetic infection from a hip replacement to a contralateral knee joint undergoing a total knee replacement.

We present a 74-year old female patient who underwent a total hip arthroplasty of the left hip after a subcapital fracture of the femur. Four months after the index procedure the patient presented with signs and symptoms of infection of the operated joint. Staph aureus and Enterococcus faecalis were recognized as the infecting bacteria. The implants were removed, cement spacers were placed and a total hip arthroplasty was performed again after three months. Unfortunately, infection ensued again and the patient underwent three more procedures until the joint was considered clean and t he hip remained flail without implants. The patient elected to undergo a total knee arthroplasty due to severe osteoarthritis of right knee. Intraoperatively tissue samples were taken and sent for cultures which identified Enterococcus faecalis present in the knee joint. Enterococcus migrated from the infected hip to nonoperated knee joint. Intravenous antibiotics were administered for three weeks but the knee presented with infection of the arthroplasty ten months after its insertion. The implants were removed the joint was debrided and cement spacers were inserted.

The patient decided not to proceed with another procedure and she remains with the cement spacers in her knee.

Rare report of migrating periprosthetic infection. Nosocomial enterococci acquired resistance cannot be ruled out. Unique characteristics in enterococci antibiotic resistance and biofilm formation.

Infection is among the first reasons for failure of orthopedic implants. Various antibacterial coatings for implanted biomaterials are under study, but only few technologies are currently available in the clinical setting. Previous studies showed the in vitro and in vivo efficacy and safety of a fast resorbable (<96 h) hyaluronic and polylactic acid based hydrogel, loaded with antibiotic or antibiofilm agents (DAC®, Novagenit Srl, Mezzolombardo, TN). Aim of this study is to report the results of the largest clinical trial in trauma and orthopedic patients.

In this prospective, controlled, study, a total of 184 patients (86 treated with internal osteosinthesis for closed fractures and 98 undergoing cementless total hip or knee joint prosthesis) were randomly assigned in three European orthopaedic centers to receive antibiotic-loaded DAC coating or to a control group, without coating. Pre- and post-operative assessment of laboratory tests, wound healing (ASEPSIS score), clinical score (SF-12 score) and x-rays were performed at fixed time intervals. Statistical analysis was performed with Fisher exact test or Student's t test. Significance level was set at p<0.05.

The study was approved by the local Ethical Committee and all patients provided a written informed consent.

On average, wound healing, clinical scores, laboratory tests and radiographic findings did not show any significant difference between the two-groups at a mean 12 months follow-up (min: 6, max: 18 months).

Four surgical site infections and two delayed union were observed in the control group compared to none in the treated group.

No local or systemic side effects, that could be related to DAC hydrogel coating, were noted and no detectable interference with bone healing or osteointegration could be found

This is the largest study, with the longest follow-up, reporting on clinical results after the use of a fast-resosrbable anti-bacterial hydrogel coating for orthopaedic and trauma implants. Our results show the safety of the tested coating in different indications; although not statistically significant, the data also show a trend towards surgical site infection reduction, as previously demonstrated in the animal models.

Of the 6075 patients enrolled in EU-CORE registry, 206 patients had orthopaedic device-related infections. Significant underlying diseases were reported in 71% patients, most frequently cardiovascular disease (38%). The common sites of infection were knee (40%) and hip (33%). Among the 170 patients with available culture results, 135 (79%) were positive. Coagulase-negative staphylococci (CoNS, 44%) and Staphylococcus aureus (43%, of those 47% were methicillin resistant) were the most commonly isolated pathogens. Daptomycin was used empirically in 48% patients and as second-line therapy in 67% patients. During daptomycin therapy, 67% patients had undergone surgery (debridement, 61%; removal of foreign device, 39%; incision and drainage, 9%). Over half of the inpatients (54%) received concomitant antibiotics. Daptomycin was most frequently prescribed at a dose of 6 mg/kg/day (48%), with a median duration of therapy of 16 (range, 1–176) days. The overall clinical success rate was 85%, and was similar whether daptomycin was administered as first- or second-line therapy. The success rates achieved for infections caused by S. aureus and CoNS were 86% and 83%, respectively. Among the 79 patients who entered the long-term follow-up, 85% had a sustained response. Adverse events (AEs) and serious AEs possibly related to daptomycin were reported in 4.4% and 1.9% patients, respectively.

Results from this real-world clinical experience showed that daptomycin is an effective and well-tolerated treatment option for orthopaedic device-related infections with a high success rate up to 2 years of follow-up.

Aim

To determine the overall survival of patients with Pelvic Ewing's Sarcoma treated in our unit and to identify prognostic factors in pelvic primaries that could be used to select patients who would most likely benefit from high intensity treatment.

Avascular necrosis (AVN) is a disorder leading to femoral head (FH) destruction, while BMPs are known for their osteogenic ability. In this study we analyzed BMP-2, BMP-4, BMP-6 and BMP-7 expression at the RNA and protein level in the normal and necrotic sites of the FHs.

Quantitative RT-PCR for BMP-2,-4,-6,-7 genes was performed in samples from the normal and necrotic sites of 52 FHs with AVN. Protein levels of BMP-2,-4,-6 were estimated by Western Blot analysis. Statistical analysis was performed using the t-test (p< 0.05).

BMP-2 and BMP-6 mRNA levels were higher in the normal than the necrotic site (BMP-2 and BMP-6, normal vs necrotic: 16.8 vs 7.5 and 2 vs 1.66, respectively). On the contrary, BMP-4 mRNA levels were higher in the necrotic (1.2) than the normal site (0.97), while BMP-7 mRNA levels were low in both sites. At the protein level, BMP-2 expressed higher in the normal (0.63) than the necrotic region (0.58), while BMP-4 and BMP-6 detected at higher levels in the necrotic site (BMP-4 and BMP-6, normal vs necrotic: 0.51 vs 0.61 and 0.52 vs 0.57, respectively).

Different mRNA levels between the normal and necrotic site, as well as discrepancies between the gene and protein BMPs expression levels suggest a different regulation mechanism between the two regions. Better understanding of the expression pattern of BMPs could lead to a more successful use of these molecules in the prevention and treatment of AVN

The evaluation of the outcome of CCK prostheses in primary TKA

Between 2002 and 2008 we implanted 34 CCK knees in 31 patients. Mean age was 69 (58–79) 10 patients were operated because of valgus knee and lateral compartment arthritis, 8 because of post-traumatic ligamentous laxity and/or bone loss and the remaining patients presented with advanced OA and varus deformity exceeding 30 degrees. All patients were followed regularly with radiographs annually and there were assessed clinically with KSS and Womac score. The findings were compared with a group of patients with similar characteristics and a CR prosthesis.

Mean follow-up was 3 years (6–1) There was no revision in this group neither was any radiological abnormality. Clinical outcome in terms of KSS and WOMAC score was excellent and comparable to the CR group.

The main indication for a CCK prosthesis is the ligamentous insufficiency. There is enough evidence to support its superiority as a treatment option in valgus knees but long term performance is yet unclear.

CCK prostheses are a reliable solution for unstable or imbalanced knees their long term behaviour though, is yet unclear

Periosteum is a specialized connective tissue that surrounds bone, containing progenitor cells that develop into osteoblasts. The osteo-progenitor cells along with growth factors, such as BMPs, play critical role in development, reconstruction and bone formation. Aim: to evaluate the expression of BMPs in human periosteum and in different subrgroups, including different donor sites, gender, and smoking habits.

Gene expression of BMPs 2,4,6,7 was performed in 60 periosteal samples using quantitative RT-PCR. Samples were obtained from 32 men/28 women, 22 smokers/38 non-smokers, 29 lower/31 upper extremities.

BMP2 gene expression was significantly higher (median: 12.02, p< 0.05) than the mRNA levels of BMPs 4,6,7 (median: 1.36, 2.55, 0.04) in all samples. BMP2 mRNA levels were higher in large compared to small bones (median: 13.4 vs 9.48), while BMPs 4,6,7 gene expression was similar (1.3 vs 1.4, 2.7 vs 2.1, 0.04 vs 0.03, respectively). In lower extremities, BMPs mRNA levels were higher than in the upper; the same was detected in non-smokers versus smokers group (BMPs2,4,6,7: 13.9 vs 1.5, 3.1 vs 0.048, 8.7 vs 1.06, 1.6 vs 0.026, respectively). mRNA transcripts of BMP2 were higher in men than women (median: 13.1 vs 10.8).

In our study, BMP2 expression is characteristically higher than that of BMP4, BMP6 and BMP7, highlighting the critical role that BMP2 plays in bone homeostasis. Furthermore, the elevated expression of BMP2 in men towards women, and of all BMPs of the lower extremity samples indicate the effect of hormones and mechanical factors in periosteal BMPs gene regulation; while the effect of smoking is reflected in the reduction of BMPs expression in smokers.

The evaluation of the middle term behaviour of the Wagner-type stems in dysplastic femurs and the presentation of the technical and surgical differences with the implantation of a Wagner stem.

Between 1997 and 2008 we implanted 64 Wagner stems in 58 patients. Average age at the time of implantation was 64 years. 52 patients was operated because of DDH, and 12 had had previous osteotomy. All patients were prospectively evaluated radiographically and clinically at annual intervals. Functional outcome was assessed with Harris Hip Score and Oxford Score.

Mean follow-up of these series was 4 years (11-1)One stem was revised because of fracture of the lesser trochander and two more patients were re-operated for open reduction. With the re-operation as end-point and 95% Confidence Interval survivorship rate was 98, 5%. There were no progressive radiolucent lines. Stem migration was at an average 2mm (1–6) during the first two years and remained stable thereafter. There was no deep infection in these series. After the second year a dense zone is evident in all Gruen zones at the implant –bone interface with a width of 2–3 mm.

Dysplasia of the proximal femur may pose significant technical problems during THA due to the distortion of the geometry and the narrowing of the femoral canal. The sort, conical Wagner type stems can offer a very good alternative is such patients. They allow control of the anteversion and they are able get a good press-fit despite the metaphyseal/diaphyseal mismatch and the femoral bowing.

Wagner type stems are a reliable alternative when performing THA in patients with dysplastic femurs.

The aim of the study was to investigate the expression of genes regulating cholesterol efflux in human chondrocytes and to study the effect of an LXR agonist on cholesterol efflux and lipid accumulation in osteoarthritic chondrocytes.

Human cartilage was obtained from 24 patients with primary osteoarthritis (OA) undergoing total knee replacement surgery. Normal cartilage was obtained from 8 individuals undergoing fracture repair surgery, with no history of joint disease. ATP-binding-cassette transporter A1(ABCA1), apolipoprotein A1 (ApoA1), and liver X receptors(LXRα and LXRβ) mRNA expression levels were evaluated using real-time PCR. The effect of the synthetic LXR agonist TO-901317 was studied after treatment of osteoarthritic chondrocytes and subsequent investigation of ABCA1 and ApoA1 mRNA expression levels. Cholesterol efflux was evaluated in osteoarthritic chondrocytes radiolabeled with [1,2(n)-3H] cholesterol after LXR treatment, while intracellular lipid accumulation was studied after Oil-red-O staining. Apoptosis was evaluated using flow cytometry.

ApoA1, ABCA1, LXRα and LXRβ mRNA expressions were significantly lower in osteoarthritic chondrocytes compared to normal. Treatment of osteoarthritic chondrocytes with the LXR agonist TO-901317 significantly increased ApoA1 and ABCA1 mRNA expression levels as well as cholesterol efflux, while it significantly reduced apoptosis. Additionally, osteoarthritic chondrocytes presented intracellular lipids deposits, while no deposits were found after treatment with TO-901317.

Our findings suggest that impaired expression of genes regulating cholesterol efflux may be a critical player in osteoarthritis, while the ability of the LXR agonist to facilitate cholesterol efflux and decrease apoptosis suggests that it may be a target for therapeutic intervention in osteoarthritis.

Percutaneous fixation with iliosacral screws has been shown to be a safe and reproducible method for the management of certain posterior pelvic injuries. However, the method is contraindicated in patients with sacral anatomical variations and dysmorphism. The incidence and the pattern of S1 anatomical variations were evaluated in 61 volunteers (35 women and 26 men) using MRI scans of the sacrum. S1 dimensions (12 parameters) in both the transverse and coronal planes were recorded and evaluated. Individuals were divided in four groups based on the S1 body size and the asymmetry of dimensions on the transverse and coronal planes. In 48 (78.6%) patients, dimensions in both planes were symmetrical despite the varying size of the S1 body. In 9 (14.8%) patients, coronal plane dimensions were disproportionally smaller compared to those of the transverse plane with a varying size of S1 body making effective iliosacral screw insertion a difficult task. In 2 (3.3%) patients there was a combination of large transverse plane and small coronal plane dimensions, with large S1 body size. A preoperative imaging study of S1 body size and coronal plane dimensions and an intraoperative fluoroscopic control of S1 dimensions on the coronal plane are suggested for safe iliosacral screw fixation

Advance medial pivot total knee replacement has been designed to reflect contemporary data regarding knee kinematics. We report the clinical outcome of 284 replacements in 225 consecutive patients. All patients were prospectively followed for a mean of 7.6 years (5 to 9) using validated rating systems, both objective and subjective.

All patients showed a statistically significant improvement (p~0.01) on the Knee Society clinical rating system, WOMAC questionnaire, SF-12 questionnaire, and Oxford knee score. The majority of patients (92%) were able to perform age appropriate activities with a mean knee flexion of 117° (85 to 135). Survival analysis showed a cumulative success rate of 99.1% (95% CI, 86.6 to 100) at five years and 97.5% (95% CI, 65.6 to 100) at seven years. Two (0.7%) replacements were revised due to aseptic loosening, one (0.35%) due to infection and one (0.35%) due to a traumatic dislocation. In only two (0.7%) replacements, progressive radiological lucent lines (combined with beta angle of 85°) were observed

The Wnt/b-catenin signaling pathway participates in normal adult bone and cartilage biology and seems to be involved in cartilage degeneration and subsequent OA progression. The aim of this study was to investigate the activation of Wnt/b-catenin pathway in osteoarthritis and the role of LRP5, a coreceptor of Wnt/b-catenin pathway, in human osteoarhritic chondrocytes.

Human cartilage was obtained from 11 patients with primary osteoarthritis (OA) undergoing total knee and hip replacement surgery. Normal cartilage was obtained from 5 healthy individuals. b-catenin and LRP5 mRNA and protein levels were investigated using real time PCR and western blot analysis, respectively. Blocking LRP5 expression was performed using small interfering (siRNA) against LRP5 and subsequent MMP-13 mRNA and protein levels were evaluated by real time RCR and western blot analysis, respectively.

We confirmed the activation of Wnt/b-catenin pathway in osteoarthritis, as we observed significant upregulation of b-catenin mRNA and protein expression in osteoarthritic chondrocytes. We also observed that LRP5 mRNA and protein expression was significantly up-regulated in osteoarthritic cartilage compared to normal. Also, blocking LRP5 expression using siRNA against LRP5 resulted in a significant decrease in MMP-13 mRNA and protein expressions.

Our findings suggest that the upregulation of LRP5 mRNA and protein expression in osteoarthritic chondrocytes results in an increased activation of Wnt/b-catenin pathway in osteoarthritis. The observed reduction of MMP-13 expression after blocking LRP5 expression in osteoarthritic chondrocytes, suggests the involvement of LRP5 in the progression and pathogenesis of osteoarthritis.

Cartilage calcification induces the synthesis of degrading enzymes, such as matrix metalloproteinases (MMPs) and prostaglandin E2 leading to tissue degeneration. The aim of the study was to investigate the effect of vitamin D on the calcification process in osteoarthritic cartilage.

We evaluated the effect of vitamin D on klotho (KL), Fibroblast Growth Factor 23 (FGF23) and Fibroblast Growth Factor Receptor 1c (FGFR1c) mRNA and protein expression levels by real-time PCR and western blot analysis, respectively. Possible interactions between klotho and FGF23 on the receptor FGFR1c in normal chondrocytes were investigated using immunoprecipitation assay. The direct effect of 1,25 dihydroxyvitamin D3 (1,25D) on KL, FGF23 and FGFR1c promoter was also evaluated.

We found that FGF23 and FGFR1c mRNA expression levels were significantly increased in osteoarthritic chondrocytes compared to normal, while KL mRNA levels were decreased (p=0.001 for all genes). We showed that klotho-FGF23-FGFR1c form complexes in normal chondrocytes and confirmed the participation of klotho in the initiation of FGF23-FGFR1c signalling. Treatment of normal chondrocytes with 1,25D resulted in a significant dose and time dependent increase of FGF23 and FGFR1c mRNA levels and in an increase of KL mRNA levels in osteoarthritic chondrocytes compared to untreated (p=0.001). We revealed, for the fist time, the presence of conserved, canonical VDREs in the proximal promoters of KL, FGF23 and FGFR1c.

We propose a common regulatory scheme of mineral homeostasis and aging in osteoarthritic chondrocytes evidenced by the positive/negative feedback actions by KL, FGF23, FGFR1c and 1,25D, through binding of vitamin D receptor (VDR) on the promoters of the above mentioned genes.

Our study aimed to investigate the role of an HMG-CoA reductase inhibitor (atorvastatin) in human osteoarthritic chondrocytes and to test the in vivo effects of intra-articular injections of atorvastatin in a rabbit experimental osteoarthritis model.

Human articular osteoarthritic chondrocytes were cultured in the presence and absence of atorvastatin. mRNA and protein expression of MMP-13, COL2A1 and aggrecan were measured using real-time PCR and Western Blot analysis.

New Zealand rabbits (n=15) underwent bilateral anterior cruciate ligament transection (ACLT) to induce osteoarthritic degeneration and received intra-articular injections of atorvastatin and normal saline in the left and right knees respectively. The first injection was at the time of ACLT and injections were repeated every 3 days for 3 weeks. Data were obtained from macroscopic and histological evaluation as well as from gene expression analysis for COL2A1, aggrecan and MMP-13.

Incubation of the cultures with atorvastatin produced a decreasing effect in MMP-13 expression. Regarding aggrecan and COL2A1 expression a significant increase was observed.

Gross morphologic evaluation showed that the joints which received atorvastatin injections, showed minimal cartilage erosion, compared to the non-treated knees where the cartilage was markedly eroded, especially on the medial knee compartment. These results were supported by histological and gene expression analysis. The mRNA expression of MMP-13 was significantly reduced in the cartilage of the statin-treated knee joints, while the expression of COL2A1 and aggrecan was increased.

The clinical relevance of our results indicates a potential protective effect of atorvastatin on articular cartilage undergoing osteoarthritic degeneration.

We evaluated the contribution of specific gene polymorphisms of IL-1a/IL-1R/IL-1RA/IL-4Ra/IL-1b/IL-12/γIFN/TGF-b/TNF-a/IL-2/IL-4/IL-6/IL-10 cytokines in patients with AVN.

DNA was extracted from 112 patients and 238 healthy Greek individuals. DNA analysis was performed by the PCR-SSP method and the use of the Protrans kit. Statistical analysis was performed by χ2 test.

In the patients, the TC frequency of the IL-1a (nt-889) was 52% while in normal was 40%. The C/G allele frequency of TGF-b codon 25 in patients was 9% C and 91% G vs 13% C and 87% G in normal. At position −238 of TNFa, 11% of the patients had the GA genotype in contrast to 1% of the controls. The GG/GG haplotype of TNFa gene promoter (nt. −308 and −238) was more frequent in both groups, while the GG/GA haplotype detected in 9% and 1% of the patients and controls, respectively. At the −1082 position of the IL-10 gene, the GG genotype was detected in 15% of the controls and 7% of the patients. Also, the GCC/GCC haplotype in IL-10 (positions -1082/-819/-592) was higher in the controls (15%) than the patients (7%).

The genotypes TC (nt-889) of IL-1a, GC (codon 25) of TGF-b, GC (nt-1082) of IL-10 and GA (nt −238) of TNFa, are more prevalent in the patients than the healthy individuals (p< 0.05). Based on our results, the presence of one of the above mentioned polymorphisms or the simultaneous carriage of more than one may contribute to the risk for osteonecrosis

Introduction: Osteoporosis is a common skeletal disease characterized by a combination of low bone mass and altered bone microarchitecture with a consequent increase of fragility. The human CER1 is a novel candidate gene for osteoporosis that can bind directly to bone morphogenetic proteins and inhibit their activity. In this study we evaluated the contribution of five novel gene single-nucleotide polymorphisms (SNPs) of CER1 in blood samples from osteoporotic and control groups.

Materials and Methods: Peripheral blood samples from 100 postmenopausal women with osteoporosis and 50 healthy Greek women, between 45 and 85 years of age, were collected and DNA was extracted. CER1 polymorphisms genotyping was carried out by PCR and sequencing of the whole gene. Bone mineral density (BMD) was examined by DXA. Statistical analysis was performed using Pearson χ2 or Fisher’s exact test in order to compare allelic frequency distribution.

Results: Genetic analysis of the CER1 gene revealed five SNPs at the positions 239C> G (rs3747532), 1058G> T (rs1494360), 2160A> G, 2355A> G (rs17289263), and 2749T> C of the CER1 gene. The above genotypes were distributed differently among osteoporotic and controls. In osteoporotic patients, the SNPs frequencies were: 78.6% heterozygotes and 3.6% homozygotes for 239C> G SNP, 66.7% and 4.3% heterozygotes and homozygotes, respectively, with T allele at the position 1058, 52.4% heterozygotes and 9.5% homozygotes for the polymorphic site A> G nt.2160, 51.2% heterozygotes and 2.4% homozygotes for the G allele at 2355 position of the CER1 gene, whereas only heterozygotes (38.9%) for the 2749T> C polymorphic site were determined (P< 0.001). However, in the control group the polymorphisms were detected only in heterozygosity and the overall distributions of the polymorphisms 239C> G, 1058G> T, 2160A> G, 2355A-> G, and 2749T> C, were 38.9%, 31.3%, 15.6%, 9.4%, 6.9% (P< 0.001), respectively.

Discussion: All the above polymorphisms, except the SNP rs3747532, are correlated with osteoporotic patients for the first time. Allele frequencies of the control group are significantly lower than those of osteoporotic for any of the five polymorphisms. These data provide the first evidence of an association (and most possible significant cumulative contribution) between the aforementioned genotypes in CER1 gene and the risk for osteoporosis in postmenopausal women.

Osteoarthritis is a complex joint disease in which all involved tissues play an important role in its onset and progression. It has been suggested that osteoarthritis is likely to be a systemic disease involving stromal cell differentiation and lipid metabolism while altered lipid metabolism has been implicated as a critical player in its pathogenesis.

As excessive accumulation of free cholesterol is toxic for the cells, the accumulation of lipids in chondrocytes may signify a causal relationship to development and/or progression of osteoarthritis; therefore we investigated the expression of genes regulating reverse cholesterol transport, as ABCA1, ApoA1, LXRa, LXR_, in human osteoarthritic chondrocytes. We also investigated the effect of an LXR agonist on ABCA1 and ApoA1 expression and, for the first time, on cholesterol effiux and lipid accumulation in osteoarthritic chondrocytes.

Articular cartilage samples were obtained from femoral condyles and tibial plateaus of patients with primary OA undergoing knee replacement surgery while normal cartilage was obtained from eight individuals undergoing fracture repair surgery, with no history of joint disease. Total cellular RNA was extracted from all samples and ABCA1, ApoA1, and LXRα and LXRβ mRNA and protein expression levels were evaluated using real-time PCR and Western blot analysis respectively.

The effect of the synthetic LXR agonist TO-901317 was studied after treatment of osteoarthritic chondrocytes and subsequent investigation of ABCA1 and ApoA1 mRNA expression levels. Cholesterol effiux was evaluated in osteoarthritic chondrocytes radiolabeled with [1,2(n)-3H] cholesterol after LXR treatment, while intracellular lipid accumulation was studied after Oil-red-O staining.

ApoA1 and ABCA1 mRNA levels were significantly lower in osteoarthritic cartilage compared to normal (p< 0.01 and p< 0.001 respectively). In addition, the two subtypes of the LXR, namely LXRα and LXRβ, mRNA levels were also found to be significantly lower in osteoarthritic cartilage (p< 0.05 and p< 0.01 respectively). The differential expression pattern of the cholesterol effiux genes between normal and osteoarthritic cartilage remained the same at the protein level as well. Treatment of osteoarthritic chondrocytes with the LXR agonist TO-901317 significantly increased ApoA1 and ABCA1 expression levels, as well as cholesterol effiux. Additionally, osteoarthritic chondrocytes presented intracellular lipids deposits, while no deposits were found after treatment with TO-901317.

Our findings suggest that impaired expression of genes regulating cholesterol effiux may be a critical player in osteoarthritis, while the ability of the LXR agonist to facilitate cholesterol effiux suggests that it may be a target for therapeutic intervention in osteoarthritis.