The recently identified hexosaminidase D enzyme substantially contributes to the elevated hexosaminidase activity in rheumatoid arthritis.

Since the 1970s, numerous reports have described elevated hexosaminidase activities in rheumatoid arthritis. However, due to the overlapping substrate specificities of different hexosaminidases, identification of the exact enzyme(s) responsible for the elevated activity remains incomplete. In this work we tested if the recently described enzyme, hexosaminidase D was expressed in human arthritic joints, and could contribute to the elevated hexosaminidase activity in rheumatoid arthritis. Thermostable ß-d-N-acetyl-galactosaminidase (hexosaminidase D) activities were determined in synovial fluid samples, synovial membranes, synovial fibroblast cell strains and synovial fibroblast-derived extracellular vesicles of patients with rheumatoid arthritis and osteoarthritis using chromogenic substrates. Expression of the HEXDC gene was detected both in steady state and in TGF-ß treated synovial fibroblasts by real time PCR. Strikingly, hexosaminidase D accounted for approximately 50% of the total ß-N-acetyl-galactosaminidase activity in synovial membranes and synovial fibroblasts, and it was responsible for the vast majority of the ß-d-N-acetyl-galactosaminidase activity in synovial fluid samples. TGF-ß downregulated the expression of hexosaminidase D in synovial fibroblasts dose-dependently. Of note, significant activity of hexosaminidase D was also found in association with extracellular vesicles released by synovial fibroblasts. This first study that describes the expression and disease relevance of the HEXDC gene in humans demonstrates the expression of this novel enzyme within the joints, and suggests that its activity may significantly contribute to the overall local exoglycosidase activity.

Biomechanical comparison of three cemented stem removal techniques in revision hip surgery.

BACKGROUND: There are various techniques available to remove a cemented femoral component and distal cement in the case of septic or aseptic loosening, periprosthetic or component fracture. The present study describes the mechanical effects of three techniques: the transfemoral approach (TFA), the distal fenestration technique (DF) and the retrograde stem removal technique (RSR). An experiment on cadaveric femora was performed to establish if there are any differences in the resistance to fracture in and between the various groups. METHODS: Twenty-two paired femora were recovered from human cadavers and were frozen. These were later subdivided into three groups to provide similar specimens in each group (TFA, DF, RSR). The femora were tested using an Instron 8874 biaxial testing system. The torque required to fracture was measured. Intra- and intergroup statistical analysis was performed. RESULTS: In the TFA group, the force required till fracture was significantly less than in controls. (p = 0.018). Similar results were found in the DF group (p = 0.048). There was no difference in the RSR group (p = 1). Intergroup analysis showed the following: Femora in the TFA group required significantly less force to fracture than specimens in the DF group (p = 0.018) or the RSR group (p = 0.0055). Femora in the DF group required significantly less force to fracture than specimens in the RSR (p = 0.037). CONCLUSIONS: The TFA technique decreases the mechanical resistance of human cadaveric femora very significantly against rotational forces. The DF technique in the same setup also significantly decreases the resistance of bone, whilst no significant change is seen with the RSR technique.

Synovial fluid ß-endorphin level in avascular necrosis, rheumatoid arthritis, and osteoarthritis of the femoral head and knee. A controlled pilot study.

The goal of this study is to determine and compare the ß-endorphin levels in the synovial fluid of patients with different joint disorders (avascular necrosis, AVN; osteoarthritis, OA; and rheumatoid arthritis, RA of the hip or knee). Eighty-seven patients were involved in our study with an average age of 62 years. Thirty-three patients had AVN (18 hips, 15 knees). Twenty-three patients were diagnosed with OA (14 hips, 9 knees), and 31 patients suffered from RA (12 hips, 19 knees). We measured the ß-endorphin levels of the synovial fluids -harvested from surgery-with radioimmunoassay. No significant difference was found in the ß-endorphin levels of the synovial fluid from AVN comparing to OA and RA, however ß-endorphin level was significantly higher in RA group than among patients with OA (p = 0.01). Synovial ß-endorphin level was slightly lower in knee comparing to hip joint p = (0.06). When examining the different joints separately in compliance with diagnoses, we concluded that the synovial ß-endorphin level from AVN was between the values of OA and RA without significant difference, whereas it was significantly higher in the knee of RA, than of OA groups (p = 0.05 knee, p = 0.2 hip). Our results confirmed those experiments which stated that there is a significant increase in synovial ß-endorphin level in patients with inflammatory autoimmune diseases (e.g., RA), comparing to the level measured in degenerative conditions (e.g., OA).

Fixation of Akin osteotomy for hallux abductus with absorbable suture.

BACKGROUND: The Akin osteotomy is a widely used procedure where various fixation methods are available, predominantly with the use of metallic component (wire, screw, staple etc.). The aim of this study is to demonstrate the results of our modified Akin procedures, where the fixation of the phalangeal osteotomy is achieved by absorbable suture, without metallic component. MATERIALS AND METHODS: Between July 2004 and October 2008, authors performed their first 22 consecutive Akin procedures with the above technique. Mean age of patients was 49 [standard deviation (SD) 17, range 19-69] years. Mean follow-up time was 26 (SD 13, range 8-57) months. RESULTS: Mean correction of the distal articular set angle (DASA) was 9.4 (SD 7.1, range 5-28) degrees. Mean shortening of the proximal phalanx was 1.8 (SD 1.0, range 0.3-4.1) mm. Among the 22 osteotomies, there was no evidence of non-union, delayed union, excessive bone callus, or loss of correction. 100% of the patients would undergo the procedure again, 91% (20/22) were completely satisfied; and 9% (2/22) were satisfied, including the one complication case. CONCLUSION: The method presented in this study for fixation of the akin osteotomy showed results identical to the ones using conventional (metal) fixation techniques concerning radiological (correction of DASA, shortening of the proximal phalanx), and clinical (complication rate, subjective satisfaction rate) findings, without the risk of complication due to hardware irritation.

Gene expression and activity of cartilage degrading glycosidases in human rheumatoid arthritis and osteoarthritis synovial fibroblasts.

INTRODUCTION: Similar to matrix metalloproteinases, glycosidases also play a major role in cartilage degradation. Carbohydrate cleavage products, generated by these latter enzymes, are released from degrading cartilage during arthritis. Some of the cleavage products (such as hyaluronate oligosaccharides) have been shown to bind to Toll-like receptors and provide endogenous danger signals, while others (like N-acetyl glucosamine) are reported to have chondroprotective functions. In the current study for the first time we systematically investigated the expression of glycosidases within the joints. METHODS: Expressions of beta-D-hexosaminidase, beta-D-glucuronidase, hyaluronidase, sperm adhesion molecule 1 and klotho genes were measured in synovial fibroblasts and synovial membrane samples of patients with rheumatoid arthritis and osteoarthritis by real-time PCR. beta-D-Glucuronidase, beta-D-glucosaminidase and beta-D-galactosaminidase activities were characterized using chromogenic or fluorogenic substrates. Synovial fibroblast-derived microvesicles were also tested for glycosidase activity. RESULTS: According to our data, beta-D-hexosaminidase, beta-D-glucuronidase, hyaluronidase, and klotho are expressed in the synovial membrane. Hexosaminidase is the major glycosidase expressed within the joints, and it is primarily produced by synovial fibroblasts. HexA subunit gene, one of the two genes encoding for the alpha or the beta chains of hexosaminidase, was characterized by the strongest gene expression. It was followed by the expression of HexB subunit gene and the beta-D-glucuronidase gene, while the expression of hyaluronidase-1 gene and the klotho gene was rather low in both synovial fibroblasts and synovial membrane samples. Tumor growth factor-beta1 profoundly downregulated glycosidase expression in both rheumatoid arthritis and osteoarthritis derived synovial fibroblasts. In addition, expression of cartilage-degrading glycosidases was moderately downregulated by proinflammatory cytokines including TNFalpha, IL-1beta and IL-17. CONCLUSIONS: According to our present data, glycosidases expressed by synovial membranes and synovial fibroblasts are under negative regulation by some locally expressed cytokines both in rheumatoid arthritis and osteoarthritis. This does not exclude the possibility that these enzymes may contribute significantly to cartilage degradation in both joint diseases if acting in collaboration with the differentially upregulated proteases to deplete cartilage in glycosaminoglycans.