Protein-Degrading Enzymes in Osteoarthritis.

OBJECTIVE: TGFß1 plays an important role in the metabolism of articular cartilage and bone; however, the pathological mechanism and targets of TGFß1 in cartilage degradation and uncoupling of subchondral bone remodeling remain unclear. Therefore, in this study, we investigated the relationship between TGFß1 and major protein-degrading enzymes, and evaluated the role of high levels of active TGFß1 in the thickening of subchondral bone and calcification of articular cartilage. MATERIALS AND METHODS: The expression of TGFß1 and protein-degrading enzymes in clinical samples of articular cartilage and subchondral bone obtained from the knee joint of patients with osteoarthritis was detected by immunohistochemistry. The expression levels of TGFß1, MMP-3, MMP-13 and IL-1ß in cartilage and subchondral bone tissues were detected by absolute real-time quantitative RT-PCR. The expression of TGFß1, nestin and osterix in subchondral bone was detected by Western blot analysis and immunohistochemistry. The degree of subchondral bone thickening was determined by micro-computed tomography (CT) imaging. RESULTS: Expression of TGFß1 and cartilage-degrading enzymes was higher in the cartilage-disrupted group than that in the intact group. Furthermore, expression of TGFß1, nestin and osterix was significantly higher in the OA group than that in the control group. Micro-CT imaging showed that in the OA group, the subchondral bone plate is thickened and the density is increased. The trabecular bone structure is thick plate-like structure, the thickness of the trabecular bone is increased and the gap is small. CONCLUSIONS: The data suggest that highly active TGFß1 activates the expression of cartilage-degrading enzymes. Abnormally activated TGFß1 may induce formation of the subchondral bone and expansion of the calcified cartilage area, eventually leading to degradation of the cartilage tissue.

Recent Insights into Long Bone Development: Central Role of Hedgehog Signaling Pathway in Regulating Growth Plate.

The longitudinal growth of long bone, regulated by an epiphyseal cartilaginous component known as the "growth plate", is generated by epiphyseal chondrocytes. The growth plate provides a continuous supply of chondrocytes for endochondral ossification, a sequential bone replacement of cartilaginous tissue, and any failure in this process causes a wide range of skeletal disorders. Therefore, the cellular and molecular characteristics of the growth plate are of interest to many researchers. Hedgehog (Hh), well known as a mitogen and morphogen during development, is one of the best known regulatory signals in the developmental regulation of the growth plate. Numerous animal studies have revealed that signaling through the Hh pathway plays multiple roles in regulating the proliferation, differentiation, and maintenance of growth plate chondrocytes throughout the skeletal growth period. Furthermore, over the past few years, a growing body of evidence has emerged demonstrating that a limited number of growth plate chondrocytes transdifferentiate directly into the full osteogenic and multiple mesenchymal lineages during postnatal bone development and reside in the bone marrow until late adulthood. Current studies with the genetic fate mapping approach have shown that the commitment of growth plate chondrocytes into the skeletal lineage occurs under the influence of epiphyseal chondrocyte-derived Hh signals during endochondral bone formation. Here, we discuss the valuable observations on the role of the Hh signaling pathway in the growth plate based on mouse genetic studies, with some emphasis on recent advances.

Early-phase musculoskeletal adaptations to different levels of eccentric resistance after 8 weeks of lower body training.

PURPOSE: Eccentric muscle actions are important to the development of muscle mass and strength and may affect bone mineral density (BMD). This study's purpose was to determine the relative effectiveness of five different eccentric:concentric load ratios to increase musculoskeletal parameters during early adaptations to resistance training. METHODS: Forty male subjects performed a supine leg press and calf press training program 3 days week(-1) for 8 weeks. Subjects were matched for pre-training leg press 1-repetition maximum strength (1-RM) and randomly assigned to one of five training groups. Concentric training load (% 1-RM) was constant across groups, but within groups, eccentric load was 0, 33, 66, 100, or 138% of concentric load. Muscle mass (dual energy X-ray absorptiometry; DXA), strength (1-RM), and BMD (DXA) were measured pre- and post-training. Markers of bone metabolism were assessed pre-, mid- and post-training. RESULTS: The increase in leg press 1-RM in the 138% group (20 ± 4%) was significantly greater (P < 0.05) than the 0% (8 ± 3%), 33% (8 ± 5%) and 66% (8 ± 4%) groups, but not the 100% group (13 ± 6 %; P = 0.15). All groups, except the 0% group, increased calf press 1-RM (P < 0.05). Leg lean mass and greater trochanter BMD were increased only in the 138% group (P < 0.05). CONCLUSIONS: Early-phase adaptations to eccentric overload training include increases in muscle mass and site-specific increases in BMD and muscle strength which are not present or are less with traditional and eccentric underload training. Eccentric overload provides a robust musculoskeletal stimulus that may benefit bedridden patients, individuals recovering from injury or illness, and astronauts during spaceflight.

Adiponectin is a candidate biomarker of lower extremity bone density in men with chronic spinal cord injury.

Adipose tissue is a major regulator of bone metabolism and in the general population obesity is associated with greater bone mineral density (BMD). However, bone-fat interactions are multifactorial, and may involve pathways that influence both bone formation and resorption with competing effects on the skeleton. One such pathway involves adipocyte production of adipokines that regulate bone metabolism. In this study we determined the association between BMD, walking status, and circulating adipokines (adiponectin and leptin) in 149 men with chronic spinal cord injury (SCI). Although adipokine levels did not vary significantly based on walking status, there was a significant inverse association between adiponectin and BMD in wheelchair users independent of body composition. We found no association between adiponectin and BMD in the walkers and no association between leptin and BMD in either group. These findings suggest that for subjects with chronic SCI, walking may mitigate the effect of adiponectin mediated bone loss. For wheelchair users, adipose-derived adiponectin may contribute to SCI-induced osteoporosis because the osteoprotective benefits of obesity appear to require mechanical loading during ambulation.

Combination therapy of dexamethasone with epigallocatechin enhances tibiotarsal bone articulation and modulates oxidative status correlates with cartilage cytokines expression in the early phase of experimental arthritis.

The inclusion of antioxidant for the treatment of arthritis, especially under the therapy with immunosuppressant, is motivated because antioxidant plays an essential role in disease progression and moreover, immunosuppressive treatment suffers redox homeostasis balance of the organism. The aim of the present study was to evaluate the enhancement of anti-arthritic effect of dexamethasone in combination with epigallocatechin on the progression of adjuvant-induced arthritis in rats. Adjuvant arthritic rats were treated with dexamethasone (0.2mg/kg), epigallocatechin (100mg/kg) and combination of dexamethasone (0.1mg/kg) with epigallocatechin (100mg/kg) daily for a period of 28 days. Paw swelling changes, estimation of serum albumin level, alteration of bone mineral density, histopathological, and radiographical analysis were assessed to evaluate the anti-arthritic effect. Lipid peroxidation and antioxidant enzyme activities in joint tissue homogenate were performed along with the expression of different pro-inflammatory cartilage cytokines like TNF-α and IL-6. Dexamethasone and epigallocatechin combination potentiated both the antiarthritic (decrease of hind paw volume) and the antioxidant effect (lipid peroxidation, superoxide dismutase, glutathione reductase and catalase). In combination with dexamethasone, epigallocatechin markedly potentiated the beneficial effect of dexamethasone which resulted in more significant increment of serum albumin and bone mineral density. Improvement of anti-arthritic effect of combination therapy was supported by histopathological, radiographical alterations, and attenuation of over-expression of cartilage cytokines. Epigallocatechin act as potent antioxidant and combined administration of dexamethasone with epigallocatechin increased the anti-arthritic efficacy of basal dexamethasone therapy and suppressed the development phase of arthritic progression in rats.

Orthopaedic and dental abnormalities in osteogenesis imperfecta: a review of the literature.

Osteogenesis imperfecta is one of the most commonly recognized inheritable disorders of the connective tissue leading to bone fragility. Usually it is associated to a genetic mutation inducing a reduction in collagen quality and entity production. It involves either modification in dentin formation or multiple bone fractures. The authors reviewed the clinical aspects of these disorders, focusing on oral and orthopaedic concerns, especially related to the histological features of the fracture callus, with respect to new trends in pharmacological and surgical treatments of bone fractures. Surgical treatment varies, according to the age of the patient. In children, surgical orthopaedic procedures include multiple osteotomies and the use of telescopic rods. Medical therapy has always to be associated to surgery and is designed to reduce the incidence of fractures, to increase growth velocity and to ally pain in order to improve mobility and independence. Bisphosphonates (BP) are considered potent inhibitors of bone resorption decreasing the osteoclast population and its activity and bone turn over.

Systemic regulation of angiogenesis and matrix degradation in bone regeneration--distraction osteogenesis compared to rigid fracture healing.

Aim of this study was the investigation of systemic biochemical regulation mechanisms of bone regeneration by angiogenic and matrix-degrading enzymes during distraction osteogenesis compared to rigid osteotomy bone healing. Serum samples of 10 otherwise healthy patients with callus distraction for lower limb-lengthening and 10 osteotomy patients undergoing elective axis correction have been collected prospectively in a standardized time schedule before and up to 6 months after the procedure. At the end of the individual investigation period, concentrations of metalloproteinases (MMP-9, -13), tissue inhibitors of metalloproteinases (TIMP-1, TIMP-2) and the angiogenic factors angiogenin and VEGF have been detected by use of commercially available enzyme immunoassays. Results have been compared to our preliminary study on proMMP-1-3. In distraction osteogenesis, significantly elevated serum concentrations compared to baseline could be detected postoperatively for proMMP-1, MMP-9, TIMP-1, angiogenin and VEGF but not for proMMP-2, proMMP-3 or TIMP-2. In patients with rigid osteotomy healing, MMP-9, TIMP-1, TIMP-2, angiogenin and VEGF were significantly increased respectively. Comparison of both patient collectives revealed significantly higher increases of serum proMMP-1, VEGF and TIMP-1 in distraction patients during the lengthening period and significantly higher serum concentrations of TIMP-2 in late fracture healing period in osteotomy patients. Serum levels of MMP-13 were below the lowest standards, and therefore quantitative analysis was not possible. Bone regeneration in distraction osteogenesis and rigid osteotomy healing is accompanied by systemic increase of matrix-degrading and angiogenic factors in a certain time course and quantity. This might reflect biochemical regulation of local bone healing in the circulation. ProMMP-1, VEGF and TIMP-1 seem to be key regulatory factors during distraction osteogenesis.