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.

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.

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.