Role of mitogen-activated protein kinase (MAPK) in troglitazone-induced osteoblastic cell death.

Troglitazone, a PPARgamma agonist, has been reported to induce cell death on different cell types. However, its mechanism of action remains unclear. The present study was undertaken to investigate the effect of troglitazone on cell death and to determine its underlying mechanism in MC3T3-E1 cells, an established osteoblast cell line. Troglitazone induced loss of cell viability in a dose- and time-dependent manner, which was accompanied by apoptosis. Troglitazone increased reactive oxygen species (ROS), but troglitazone-induced cell death was not affected by the antioxidant N-acetylcysteine, suggesting that the ROS generation is not involved in the cytotoxicity of troglitazone. Troglitazone-induced cell death was prevented by the PPARgamma antagonist GW9662. Troglitazone treatment inhibited activation of extracellular signal-regulated protein kinase (ERK) and stimulated p38 activation. Troglitazone-induced cell death was increased by the ERK inhibitor U0126 and prevented by transfection with constitutively active MEK1 and the p38 inhibitor SB203580. Troglitazone induced depolarization of mitochondrial membrane potential and its effect was blocked by SB203580 and GW9662. Caspase-3 was activated by troglitazone treatment and pharmacological inhibition of caspase blocked troglitazone-induced cell death. Taken together, these data suggest that troglitazone induces apoptosis via a caspase-dependent mechanism associated with down-regulation of ERK and up-regulation of p38.

Role of mitogen-activated protein kinases in hydrogen peroxide-induced cell death in osteoblastic cells.

Oxidative stress is known to induce cell death in a wide variety of cell types, apparently by modulating intracellular signaling pathways. However, the underlying mechanism by which oxidants induce cell death remains unclear. The present study was undertaken to determine the role of the mitogen-activated protein kinase subfamilies in hydrogen peroxide (H2O2)-induced cell death of osteoblastic cells. H2O2 resulted in a time- and dose-dependent cell death, which was, in part, attributed to apoptosis. H2O2-induced cell death was prevented by iron chelator, hydroxyl radical scavengers. But H2O2-induced cell death was not affected by 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase activation. H2O2 treatment caused a transient activation of extracellular signal-regulated kinase (ERK), followed by sustained activation. Cell death induced by H2O2 was prevented by PD98059, an inhibitor of ERK upstream kinase MEK1/2. But H2O2 induced a transient activation of p38 and c-Jun N-terminal kinase (JNK) without sustained activation and inhibitors of these kinses were not effective in preventing the cell death. H2O2 increased Bax expression and produced hyperpolarization of mitochondrial membrane potential and its effect was prevented by PD98059. The ERK activation and cell death induced by H2O2 were not dependent on the phosphorylation of epidermal growth factor receptor. Taken together, these findings suggest that the ERK signaling pathway plays an active role in mediating H2O2-induced apoptosis of osteoblasts and functions upstream of mitochondria-dependent pathway to initiate the apoptotic signal.

Management of cubitus varus and valgus.

BACKGROUND: Many types of osteotomy have been proposed for the treatment of cubitus varus and valgus, but they have limitations, such as poor internal fixation, residual protrusion of the lateral or medial condyle, technical difficulty, the need for long-term immobilization, a risk of neurovascular injury, and patient discomfort. We reviewed the results of a simple step-cut translation osteotomy that overcomes these limitations. METHODS: Between 1993 and 2002, we treated nineteen cases of cubitus varus and thirteen cases of cubitus valgus with use of a simple step-cut translation osteotomy and fixation with a Y-shaped humeral plate. After surgery, the patients were observed closely for more than one year. We compared preoperative and postoperative humerus-elbow-wrist angles, ranges of motion, and lateral or medial prominence indices for all patients. The results were evaluated according to the modified criteria of Oppenheim et al. The presence of tardy ulnar nerve palsy and its duration, and postoperative lazy-s deformity or unsightly scarring, were also noted. RESULTS: There were twenty-six excellent and six good results. In the nineteen patients with cubitus varus, the average amount of correction of the humerus-elbow-wrist angle was 26.0 degrees , to a mean postoperative angle of 8.6 degrees , and the average increase in the lateral prominence index was 8.2%. In the thirteen patients with cubitus valgus, the average correction in the humerus-elbow-wrist angle was 27.6 degrees , resulting in a final angle of 9.1 degrees , and the average increase in the medial prominence index was 11.9%. In all patients, the desired range of motion, good alignment, and complete union of the bone were achieved. CONCLUSIONS: Step-cut translation osteotomy, with a wedge-shaped osteotomized surface, fixed with a Y-shaped humeral plate is a relatively simple procedure resulting in very firm fixation that allows early movement of the joint with good clinical results.

The flavonoid quercetin induces apoptosis and inhibits migration through a MAPK-dependent mechanism in osteoblasts.

The present study was undertaken to evaluate effects of quercetin, a major dietary flavonoid occurring in foods of plant origin, on cell viability and migration of osteoblastic cells. Quercetin inhibited cell viability, which was largely attributed to apoptosis, in a dose-and time-dependent manner in osteoblastic cells. Similar cytotoxicity of quercetin was observed in adipose tissue-derived stromal cells. Quercetin exerted a protective effect against H(2)O(2)-induced cell death, whereas it increased TNF-alpha-induced cell death. Western blot analysis showed that quercetin induced activation of ERK and p38, but not JNK. Quercetin-induced cell death was prevented by the ERK inhibitor PD98059, but not by inhibitors of p38 and JNK. Quercetin increased Bax expression and caused depolarization of mitochondrial membrane potential, which were inhibited by PD98059. Quercetin induced caspase-3 activation, and the quercetininduced cell death was prevented by caspase inhibitors. Quercetin inhibited cell migration, and its effect was prevented by inhibitors of ERK and p38. Taken together, these findings suggest that quercetin induces apoptosis through a mitochondria-dependent mechanism involving ERK activation and inhibits migration through activation of ERK and p38 pathways. Quercetin may exert both protective and deleterious effects in bone repair.

Arthroscopic all-inside repair techniques of lateral meniscus anterior horn tear: a technical note.

Although the conventional outside-in technique is especially useful for repairing tears in the anterior portion of the meniscus, it has a disadvantage of making an additional 1-2 cm sized skin incision and tying knots subcutaneously over the capsule. Therefore we devised two all-inside repair techniques of lateral meniscus anterior horn tear according to the site of meniscal tear, meniscosynovial junction or red-red zone. Because these techniques are modified methods of the outside-in meniscal repair using a spinal needle, they are as simple as conventional outside-in technique. In addition they have advantages of vertical mattress suture, which is an important characteristic of the all-inside repair, and no additional incision. We recommend these techniques as an alternative method for repairing an anterior horn tear of the lateral meniscus.

Activation of peroxisome proliferator-activated receptor-gamma (PPARgamma) induces cell death through MAPK-dependent mechanism in osteoblastic cells.

The present study was undertaken to determine the role of the mitogen-activated protein kinase (MAPK) subfamilies in cell death induced by PPARgamma agonists in osteoblastic cells. Ciglitazone and troglitazone, PPARgamma agonists, resulted in a concentration- and time-dependent cell death, which was largely attributed to apoptosis. But a PPARalpha agonist ciprofibrate did not affect the cell death. Ciglitazone caused reactive oxygen species (ROS) generation and ciglitazone-induced cell death was prevented by antioxidants, suggesting an important role of ROS generation in the ciglitazone-induced cell death. ROS generation and cell death induced by ciglitazone were inhibited by the PPARgamma antagonist GW9662. Ciglitazone treatment caused activation of extracellular signal-regulated kinase (ERK) and p38. Activation of ERK was dependent on epidermal growth factor receptor (EGFR) and that of p38 was independent. Ciglitazone-induced cell death was significantly prevented by PD98059, an inhibitor of ERK upstream kinase MEK1/2, and SB203580, a p38 inhibitor. Ciglitazone treatment increased Bax expression and caused a loss of mitochondrial membrane potential, and its effect was prevented by N-acetylcysteine, PD98059, and SB203580. Ciglitazone induced caspase activation, which was prevented by PD98059 and SB203580. The general caspase inhibitor z-DEVD-FMK and the specific inhibitor of caspases-3 DEVD-CHO exerted the protective effect against the ciglitazone-induced cell death. The EGFR inhibitors AG1478 and suramin protected against the ciglitazone-induced cell death. Taken together, these findings suggest that the MAPK signaling pathways play an active role in mediating the ciglitazone-induced cell death of osteoblasts and function upstream of a mitochondria-dependent mechanism. These data may provide a novel insight into potential therapeutic strategies for treatment of osteoporosis.

Chronic radial head dislocation in children, Part 1: pathologic changes preventing stable reduction and surgical correction.

The pathologic changes in 15 elbows of 14 children (2 bilateral congenital, 12 unilateral posttraumatic, mean age 9.5 years) with radial head dislocation unreduced for at least 3 months (range 3-180 months) and their open treatment were reviewed. Common dysplastic changes observed in both congenital and posttraumatic groups included large deformed radial heads, slender radial necks, and ulnar bowing. Changes were bilateral and symmetrical in the congenital group. In traumatic dislocations, patients with more severe deformities had longer delays from time of injury to time of reduction. Persistent pain, limitation of motion, and deformity were unacceptable symptoms to both patients and their parents, prompting surgical intervention. To produce a smooth rotational arc for the radius and maintain it in stable reduction, restoration of the congruency of the capitello-radioulnar joint and correction of the various dysplastic changes were mandatory during open reduction.

Chronic radial head dislocation in children, Part 2: results of open treatment and factors affecting final outcome.

Fifteen elbows (3 congenital, 12 traumatic) in 14 children (mean age 9.5 years) with chronic radial head dislocation for at least 3 months (range 3-180 months) underwent radial head-sparing reconstructive surgery and were followed up at an average of 43.5 months postoperatively (range 12-105 months). At follow-up, the patients were evaluated radiographically and clinically using range-of-motion measurements and an elbow performance score based on four parameters (deformity, pain, motion, function). Ten cases had excellent results, two had good results, two had fair results, and one case had poor results. Scores at follow-up were evaluated with seven preoperative factors. Among those, the degree of preoperative carrying angle asymmetry associated with flexion contracture correlated significantly with the elbow scores. The most common complication was loss of pronation. The authors advocate radial head reduction and reconstruction in chronic radial head dislocations in children after obtaining informed consent from patient and parents.

Trochlear deformity occurring after distal humeral fractures: magnetic resonance imaging and its natural progression.

Eighteen children (mean age 50.7 months) with trochlear deformities occurring after and related to distal humeral fractures (12 Salter-Harris type 2, 5 supracondylar, 1 Salter-Harris type 4) were evaluated with serial radiographs. The carrying angle and range of motion were measured throughout the follow-up period (up to 13 years after trauma) after definitive treatment. Bony defects on the medial (17 patients) and central (1 patient) regions of the trochlea were observed at a mean of 3.4 months after the trauma. They also persisted up to 4 to 7 years (latest follow-up in an intermediate follow-up group) and eventually reossified by skeletal maturity (in a long-term follow-up group). Magnetic resonance imaging was performed on eight patients after a mean of 1.9 years from injury. Low signal intensity on T2 indicative of cartilage necrosis and an intact articular surface were found. Cubitus varus deformity, which developed in almost all patients, was observed to be nonprogressive after 3 to 4 years but persisted until maturity. Limitation of motion and late neuropathy were not seen.