Inhibition of beta-catenin signaling by Pb leads to incomplete fracture healing

There is strong evidence in the clinical literature to suggest that elevated lead (Pb) exposure impairs fracture healing. Since Pb has been demonstrated to inhibit bone formation, and Wnt signaling is an important anabolic pathway in chondrocyte maturation and endochondral ossification, we investigated the impact of Wnt therapy on Pb-exposed mice undergoing bone repair in a mouse tibial fracture model. We established that tibial fracture calluses from Pb-treated mice were smaller and contained less mineralized tissue than vehicle controls. This resulted in the persistence of immature cartilage in the callus and decreased β-catenin levels. Reduction of β-catenin protein was concurrent with systemic elevation of LRP5/6 antagonists DKK1 and sclerostin in Pb-exposed mice throughout fracture healing. β-catenin stimulation by the GSK3 inhibitor BIO reversed these molecular changes and restored the amount of mineralized callus. Overall, Pb is identified as a potent inhibitor of endochondral ossification in vivo with correlated effects on bone healing with noted deficits in β-catenin signaling, suggesting the Wnt/β-catenin as a pivotal pathway in the influence of Pb on fracture repair.

Hypertrophic chondrocytes in the rabbit growth plate can proliferate and differentiate into osteogenic cells when capillary invasion is interposed by a membrane filter

The fate of hypertrophic chondrocytes during endochondral ossification remains controversial. It has long been thought that the calcified cartilage is invaded by blood vessels and that new bone is deposited on the surface of the eroded cartilage by newly arrived cells. The present study was designed to determine whether hypertrophic chondrocytes were destined to die or could survive to participate in new bone formation. In a rabbit experiment, a membrane filter with a pore size of 1 µm was inserted in the middle of the hypertrophic zone of the distal growth plate of ulna. In 33 of 37 animals, vascular invasion was successfully interposed by the membrane filter. During 8 days, the cartilage growth plate was enlarged, making the thickness 3-fold greater than that of the nonoperated control side. Histological examination demonstrated that the hypertrophic zone was exclusively elongated. At the terminal end of the growth plate, hypertrophic chondrocytes extruded from their territorial matrix into the open cavity on the surface of the membrane filter. The progenies of hypertrophic chondrocytes (PHCs) were PCNA positive and caspase-3 negative. In situ hybridization studies demonstrated that PHCs did not express cartilage matrix proteins anymore but expressed bone matrix proteins. Immunohistochemical studies also demonstrated that the new matrix produced by PHCs contained type I collagen, osteonectin, and osteocalcin. Based on these results, we concluded that hypertrophic chondrocytes switched into bone-forming cells after vascular invasion was interposed in the normal growth plate.

Delayed fracture healing and increased callus adiposity in a C57BL/6J murine model of obesity-associated type 2 diabetes mellitus

Introduction

Impaired healing and non-union of skeletal fractures is a major public health problem, with morbidity exacerbated in patients with diabetes mellitus (DM). DM is prevalent worldwide and affects approximately 25.8 million US adults, with >90% having obesity-related type 2 DM (T2DM). While fracture healing in type 1 DM (T1DM) has been studied using animal models, an investigation into delayed healing in an animal model of T2DM has not yet been performed.

Methods

Male C57BL/6J mice at 5 weeks of age were placed on either a control lean diet or an experimental high-fat diet (HFD) for 12 weeks. A mid-diaphyseal open tibia fracture was induced at 17 weeks of age and a spinal needle was used for intra-medullary fixation. Mice were sacrificed at days 7, 10, 14, 21, 28, and 35 for micro-computed tomography (μCT), histology-based histomorphometry and molecular analyses, and biomechanical testing.

Results

HFD-fed mice displayed increased body weight and impaired glucose tolerance, both characteristic of T2DM. Compared to control mice, HFD-fed mice with tibia fractures showed significantly (p<0.001) decreased woven bone at day 28 by histomorphometry and significantly (p<0.01) decreased callus bone volume at day 21 by μCT. Interestingly, fracture calluses contained markedly increased adiposity in HFD-fed mice at days 21, 28, and 35. HFD-fed mice also showed increased PPARγ immunohistochemical staining at day 14. Finally, calluses from HFD-fed mice at day 35 showed significantly (p<0.01) reduced torsional rigidity compared to controls.

Discussion

Our murine model of T2DM demonstrated delayed fracture healing and weakened biomechanical properties, and was distinctly characterized by increased callus adiposity. This suggests altered mesenchymal stem cell fate determination with a shift to the adipocyte lineage at the expense of the osteoblast lineage. The up-regulation of PPARγ in fracture calluses of HFD-fed mice is likely involved in the proposed fate switching.

Aging periosteal progenitor cells have reduced regenerative responsiveness to bone injury and to the anabolic actions of PTH 1-34 treatment

A stabilized tibia fracture model was used in young (8-week old) and aged (1-year old) mice to define the relative bone regenerative potential and the relative responsiveness of the periosteal progenitor population with aging and PTH 1-34 (PTH) systemic therapy. Bone regeneration was assessed through gene expressions, radiographic imaging, histology/histomorphometry, and biomechanical testing. Radiographs and microCT showed increased calcified callus tissue and enhanced bone healing in young compared to aged mice. A key mechanism involved reduced proliferation, expansion, and differentiation of periosteal progenitor cell populations in aged mice. The experiments showed that PTH increased calcified callus tissue and torsional strength with a greater response in young mice. Histology and quantitative histomorphometry confirmed that PTH increased callus tissue area due primarily to an increase in bone formation, since minimal changes in cartilage and mesenchyme tissue area occurred. Periosteum examined at 3, 5, and 7 days showed that PTH increased cyclin D1 expression, the total number of cells in the periosteum, and width of the periosteal regenerative tissue. Gene expression showed that aging delayed differentiation of both bone and cartilage tissues during fracture healing. PTH resulted in sustained Col10a1 expression consistent with delayed chondrocyte maturation, but otherwise minimally altered cartilage gene expression. In contrast, PTH 1-34 stimulated expression of Runx2 and Osterix, but resulted in reduced Osteocalcin. β-Catenin staining was present in mesenchymal chondroprogenitors and chondrocytes in early fracture healing, but was most intense in osteoblastic cells at later times. PTH increased active β-catenin staining in the osteoblast populations of both young and aged mice, but had a lesser effect in cartilage. Altogether the findings show that reduced fracture healing in aging involves decreased proliferation and differentiation of stem cells lining the bone surface. While PTH 1-34 enhances the proliferation and expansion of the periosteal stem cell population and accelerates bone formation and fracture healing, the effects are proportionately reduced in aged mice compared to young mice. β-Catenin is induced by PTH in early and late fracture healing and is a potential target of PTH 1-34 effects.

BMP-2 induces ATF4 phosphorylation in chondrocytes through a COX-2/PGE2 dependent signaling pathway

OBJECTIVE

Bone morphogenic protein (BMP)-2 is approved for fracture non-union and spine fusion. We aimed to further dissect its downstream signaling events in chondrocytes with the ultimate goal to develop novel therapeutics that can mimic BMP-2 effect but have less complications.

METHODS

BMP-2 effect on cyclooxygenase (COX)-2 expression was examined using Real time quantitative PCR (RT-PCR) and Western blot analysis. Genetic approach was used to identify the signaling pathway mediating the BMP-2 effect. Similarly, the pathway transducing the PGE2 effect on ATF4 was investigated. Immunoprecipitation (IP) was performed to assess the complex formation after PGE2 binding.

RESULTS

BMP-2 increased COX-2 expression in primary mouse costosternal chondrocytes (PMCSC). The results from the C9 Tet-off system demonstrated that endogenous BMP-2 also upregulated COX-2 expression. Genetic approaches using PMCSC from ALK2(fx/fx), ALK3(fx/fx), ALK6(-/-), and Smad1(fx/fx) mice established that BMP-2 regulated COX-2 through activation of ALK3-Smad1 signaling. PGE-2 EIA showed that BMP-2 increased PGE2 production in PMCSC. ATF4 is a transcription factor that regulates bone formation. While PGE2 did not have significant effect on ATF4 expression, it induced ATF4 phosphorylation. In addition to stimulating COX-2 expression, BMP-2 also induced phosphorylation of ATF4. Using COX-2 deficient chondrocytes, we demonstrated that the BMP-2 effect on ATF4 was COX-2-dependent. Tibial fracture samples from COX-2(-/-) mice showed reduced phospho-ATF4 immunoreactivity compared to wild type (WT) ones. PGE2 mediated ATF4 phosphorylation involved signaling primarily through the EP2 and EP4 receptors and PGE2 induced an EP4-ERK1/2-RSK2 complex formation.

CONCLUSIONS

BMP-2 regulates COX-2 expression through ALK3-Smad1 signaling, and PGE2 induces ATF4 phosphorylation via EP4-ERK1/2-RSK2 axis.

Early changes in muscle atrophy and muscle fiber type conversion after spinal cord transection and peripheral nerve transection in rats

Background

Spinal cord transection and peripheral nerve transection cause muscle atrophy and muscle fiber type conversion. It is still unknown how spinal cord transection and peripheral nerve transection each affect the differentiation of muscle fiber type conversion mechanism and muscle atrophy. The aim of our study was to evaluate the difference of muscle weight change, muscle fiber type conversion, and Peroxisome proliferator-activated receptor-γ coactivatior-1α (PGC-1α) expression brought about by spinal cord transection and by peripheral nerve transection.

Methods

Twenty-four Wistar rats underwent surgery, the control rats underwent a laminectomy; the spinal cord injury group underwent a spinal cord transection; the denervation group underwent a sciatic nerve transection. The rats were harvested of the soleus muscle and the TA muscle at 0 week, 1 week and 2 weeks after surgery. Histological examination was assessed using hematoxylin and eosin (H&E) staining and immunofluorescent staing. Western blot was performed with 3 groups.

Results

Both sciatic nerve transection and spinal cord transection caused muscle atrophy with the effect being more severe after sciatic nerve transection. Spinal cord transection caused a reduction in the expression of both sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection produced an increase in expression of sMHC protein and PGC-1α protein in the soleus muscle. The results of the expression of PGC-1α were expected in other words muscle atrophy after sciatic nerve transection is less than after spinal cord transection, however muscle atrophy after sciatic nerve transection was more severe than after spinal cord transection.

Conclusion

In the conclusion, spinal cord transection diminished the expression of sMHC protein and PGC-1α protein in the soleus muscle. On the other hand, sciatic nerve transection enhanced the expression of sMHC protein and PGC-1α protein in the soleus muscle.

Angiogenesis and myogenesis in mouse tibialis anterior muscles during distraction osteogenesis: VEGF, its receptors, and myogenin genes expression

Angiogenesis and myogenesis occur in the surrounding skeletal muscles following distraction osteogenesis, but their molecular mechanisms remain unclear. The present study investigated morphological features of lengthened muscles and the time course change of vascular endothelial growth factor (VEGF), its receptors (VEGFR-1 and VEGFR-2) and myogenin gene expression profiles related to angiogenesis and myogenesis in tibialis anterior (TA) muscles with a mouse model of distraction osteogenesis, which involves 1 week of waiting period (latency phase), 2 weeks of intermittent distraction (distraction phase), and 5 weeks of remodeling period (consolidation phase). Macroscopic findings showed that lengthened TA muscles increased to approximately 42% longer and 10% heavier at the end of the process when compared to pre-surgery. During the distraction phase, VEGF and its receptors were induced in the vascular endothelial cells, myogenin-positive satellite cells and myocytes, and subsequently, capillary progression and myogenesis were increased. Real-time RT-PCR showed that Vegf, Vegfr-1, Vegfr-2, and myogenin genes expression was enhanced during the muscle lengthening. Vegf and Vegfr-1 were upregulated following the recession of angiogenesis at the consolidation phase. We conclude that upregulation of VEGF and its receptors by mechanical tension-stress could be involved in the process of angiogenesis and myogenesis in lengthened muscles.

Aryl hydrocarbon receptor-mediated impairment of chondrogenesis and fracture healing by cigarette smoke and benzo(a)pyrene

The clinical literature strongly suggests that bone healing in cigarette smokers is impaired. Since cigarette smoke (CS) contains numerous polycyclic aromatic hydrocarbons (PAHs), and since dioxins impair bone formation in vivo via the Aryl Hydrocarbon Receptor (AHR), we investigated the impact of PAH/AHR signaling on chondrogenesis and on healing in a mouse tibial fracture model. We established that CS activates AHR signaling in fractures by up-regulating the AHR target gene cytochrome p4501A1 (Cyp1A1). For in vitro studies, we employed the mouse limb bud micromass chondrogenesis model. After confirming that chondrocytes express AHR during differentiation, we treated cells with a prototypical PAH found in CS, benzo(a)pyrene (BaP), or cigarette smoke extract (CSE). Both BaP and CSE strongly inhibited chondrogenesis in mesenchymal cells generated from E11 limb buds, with BaP also accelerating chondrocyte hypertrophy in cultures generated from E12 limb buds. Detection of DNA adducts in the BaP-treated cultures suggests that the distinct phenotypic effects of BaP may be due to the formation of reactive metabolites. Blockade of AHR signaling with the AHR antagonist MNF reverses the effects of BaP, but not CSE, suggesting that CSE inhibition of chondrogenesis is AHR-independent. Correlating with these results, tibial fracture calluses from BaP-treated mice were smaller and contained less mineralized tissue than vehicle controls. Overall, BaP is identified as a potent inhibitor of chondrogenesis in vitro with correlated effects on fracture healing similar to those of CS itself, suggesting a basis for PAHs as key compounds in the influence of CS on fracture repair.

DELAYED RUPTURE OF EXTENSOR DIGITORUM COMMUNIS TENDON FOLLOWING VOLAR PLATING OF DISTAL RADIUS FRACTURE

We present a case of delayed rupture of extensor digitorum communis tendon seven years after volar plating of distal radius fracture. Drill bit penetration during surgery and prominent screw tips into the fourth extensor compartment have a potential risk to damage the tendons. Careful and accurate use of internal fixation instruments is necessary to avoid this complication.

Attritional rupture of the flexor tendons to the small finger caused by osteophyte of the ulnar head: case report

We present a rare case of attritional rupture of the flexor tendons to the small finger caused by an osteophyte of the volar aspect of the ulnar head.

Vascularized pedicled bone graft for avascular necrosis of the capitate: case report

Avascular necrosis of the capitate is a rare disorder of unknown etiology that causes wrist pain and limitation of function. We present a case of a 15-year-old boy successfully treated with vascularized pedicled bone graft from the dorsal aspect of the distal radius.

Expression of HMGA2-LPP and LPP-HMGA2 fusion genes in lipoma: identification of a novel type of LPP-HMGA2 transcript in four cases

BACKGROUND

In a subset of lipoma, a specific t(3;12)(q27-28;q14-15) chromosomal translocation leads to the fusion of the high mobility group A2 (HMGA2) gene and the lipoma preferred partner (LPP) gene. Although the expression of HMGA2-LPP fusion gene has been reported in lipomas, the reciprocal LPP-HMGA2 fusion gene has rarely been described.

MATERIALS AND METHODS

Ninety-eight cases of lipoma were analyzed for the possible expression of HMGA2-LPP and LPP-HMGA2 fusion genes using a reverse-transcription polymerase chain reaction method.

RESULTS

Ten lipomas (10%) revealed both HMGA2-LPP and LPP-HMGA2 fusion transcripts, nine (9%) only HMGA2-LPP, and three (3%) only LPP-HMGA2. DNA sequencing analysis demonstrated that the HMGA2-LPP transcript in 19 lipomas consisted of exons 1-3 of HMGA2 and exons 9-11 of LPP, which was described previously. Out of 13 lipomas with LPP-HMGA2 transcript, 9 were associated with a previously reported LPP-HMGA2 fusion transcript, which fuses exon 8 of LPP to exon 4 of HMGA2, while 4 with a novel type of LPP-HMGA2 fusion transcript, which fuses exon 7 of LPP to exon 4 of HMGA2.

CONCLUSION

In addition to the HMGA2-LPP fusion gene, the LPP-HMGA2 fusion gene could have some specific roles for lipomagenesis. The biological implications of the expression and the variation of LPP-HMGA2 fusion transcripts need to be elucidated.

Early breakage of a titanium volar locking plate for fixation of a distal radius fracture: case report

This report presents a case demonstrating the early breakage of a titanium volar locking plate implanted for internal fixation of a dorsally displaced distal radius fracture in which the dorsal cortex was severely comminuted. Careful selection of the proper plate and appropriate surgical technique and postoperative management are necessary to avoid this complication.

[Bone fracture and the healing mechanisms. The mechanical stress for fracture healing in view of distraction osteogenesis]

It is generally accepted that moderate mechanical stress influences the course of fracture healing. A flexible fixation of the fractured site can induce fracture callus formation, whereas an unstable fixation can lead to a nonunion. The relationship between mechanical stress and the process of bone regeneration or healing remains incompletely understood. Distraction osteogenesis is a surgical technique that, using appropriate mechanical tension-stress, does not break the callus but rather it stimulates and maintains osteogenesis. The common principles of distraction osteogenesis are osteotomy and slow progressive distraction by an external fixation device. Interest in bone regeneration associated with mechanical stress might lead to better understanding of the fracture healing process.

Optimal increase in bone mass by continuous local infusion of alendronate during distraction osteogenesis in rabbits

Several methods have been used to increase bone mass in distraction osteogenesis. Since bone resorption as well as regeneration is stimulated in the distracted segment, bisphosphonate can be a beneficial agent for distraction osteogenesis. Here, we examined the effects of bisphosphonate injected continuously into the regenerate on bone volume, and architectural and mechanical properties of distraction osteogenesis. The left tibia of Japanese White rabbits (n=66) was subjected to slow distraction using an external fixator. At the beginning of the consolidation phase, alendronate (7 microg/kg/day) was infused directly into the lengthened segment for 14 days using an osmotic pump. Control rabbits were infused with phosphate buffered saline (PBS). The tibiae were monitored weekly by soft X-ray and dual-energy X-ray absorptiometry (DXA). The animals were sacrificed at 4, 6, and 8 weeks after operation to examine bone mineral density (BMD) and cortical bone thickness (CBT) by peripheral quantitative computerized tomography (pQCT), while the mechanical property of the lengthened tibia was measured by three-point bending test. In PBS-infused control animals, bone mineral content around the lengthened segment began to decrease after the first week of consolidation phase, forming a tubular bone structure with thin cortex. Infusion of alendronate increased peak bone mineral content around the lengthened segment. At the end of the experiment, volumetric BMD, CBT and mechanical strength of the lengthened segment of the treatment group were approximately twice those of the control animals. Alendronate infused in this manner significantly prevented the osteopenia that critically began early in the consolidation phase, though the dose used in this study was relatively low and no adverse events were noted.

Altered fracture callus formation in chondromodulin-I deficient mice

Chondromodulin-I (Chm-I) is a glycoprotein that stimulates the growth of chondrocytes and inhibits angiogenesis in vitro. Mice lacking the Chm1 gene show abnormal bone metabolism and pathological angiogenesis in cardiac valves in the mature stage although they develop normally without aberrations in endochondral bone formation during embryogenesis or in cartilage development during growth. These findings indicate that Chm-I is critical under conditions of stress such as bone repair through endochondral ossification of a fracture callus. We carried out the present study to examine the expression and role of Chm-I in bone repair using a stabilized tibial fracture model, and compared fracture healing in Chm1 knockout (Chm1(-/-)) mice with that in wild-type mice. Chm-I mRNA and protein localized in the external cartilaginous callus in the reparative phase of fracture healing. Radiological examination showed a delayed union in Chm1(-/-) mice although the fracture site was covered with both external and internal calluses. Chm1 null mutation reduced external cartilaginous callus formation as judged by marked decrease of type X collagen alpha 1 (Col10a1) expression and the total amount of cartilage matrix. Interestingly, the majority of chondrocytes in the periosteal callus failed to differentiate into mature chondrocytes in Chm1(-/-) mice, while the hypertrophic maturation of chondrocytes between the cortices was not affected. These results suggest that Chm-I is involved in hypertrophic maturation of periosteal chondrocytes. Although a direct effect of Chm-I on bones is still unclear, bony callus formation was increased while external cartilaginous callus decreased in Chm1(-/-) mice. We conclude that in the absence of Chm1, predominant primary bone healing occurs due to an indirect effect induced by reduction of cartilaginous callus rather than to a direct effect on osteogenic function, resulting in a delayed union.

Callus formation during healing of the repaired tendon-bone junction. A rat experimental model

This study was undertaken to elucidate the mechanism of biological repair at the tendon-bone junction in a rat model. The stump of the toe flexor tendon was sutured to a drilled hole in the tibia (tendon suture group, n = 23) to investigate healing of the tendon-bone junction both radiologically and histologically. Radiological and histological findings were compared with those observed in a sham control group where the bone alone was drilled (n = 19). The biomechanical strength of the repaired junction was confirmed by pull-out testing six weeks after surgery in four rats in the tendon suture group. Callus formation was observed at the site of repair in the tendon suture group, whereas in the sham group callus formation was minimal. During the pull-out test, the repaired tendon-bone junction did not fail because the musculotendinous junction always disrupted first. In order to understand the factors that influenced callus formation at the site of repair, four further groups were evaluated. The nature of the sutured tendon itself was investigated by analysing healing of a tendon stump after necrosis had been induced with liquid nitrogen in 16 cases. A proximal suture group (n = 16) and a partial tenotomy group (n = 16) were prepared to investigate the effects of biomechanical loading on the site of repair. Finally, a group where the periosteum had been excised at the site of repair (n = 16) was examined to study the role of the periosteum. These four groups showed less callus formation radiologically and histologically than did the tendon suture group. In conclusion, the sutured tendon-bone junction healed and achieved mechanical strength at six weeks after suturing, showing good local callus formation. The viability of the tendon stump, mechanical loading and intact periosteum were all found to be important factors for better callus formation at a repaired tendon-bone junction.

Continuous local infusion of fibroblast growth factor-2 enhances consolidation of the bone segment lengthened by distraction osteogenesis in rabbit experiment

Experimental tibial lengthening was achieved in 61 rabbits to examine the effect of continuous local infusion of recombinant human fibroblast growth factor-2 (rhFGF-2) on bone healing of the lengthened segment. The tibial diaphysis was separated by osteotomy and was subjected to slow progressive distraction (rate: 0.35 mm/12 h) using a monolateral external fixator. There were a lag phase for 1 week, a distraction phase for 2 weeks, and a consolidation phase for 5 weeks in this experiment. At various stages of distraction, rhFGF-2 was infused continuously for 2 weeks into the lengthened segment (rate: 14.28 microg/60 microl/day) using an osmotic pump implanted under the skin. Bone healing was significantly accelerated when rhFGF-2 was infused in the beginning of consolidation phase, but not in the distraction phase or in the lag phase. Infusion of normal saline (N/S) using the same osmotic pump had no effect. Dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (pQCT) studies demonstrated that rhFGF-2-treated tibia had increased bone mineral density (BMD), bone mineral content (BMC) and cortical bone thickness (CBT) when compared with N/S-treated tibia. Three-point bending test demonstrated that rhFGF-2-treated bone had significantly stronger mechanical properties than N/S-treated bone. Finally, distribution of the infused materials was checked by using Indian ink or radio-opaque. The dyes distributed widely but exclusively in the lengthened segment. Based on these results, we conclude that direct delivery of rhFGF-2 into the lengthened segment can shorten the consolidation phase of limb lengthening and the method is applicable to the clinical treatment.

Treatment of dysplastic osteoarthritis with labral tear by Chiari pelvic osteotomy: outcomes after more than 10 years follow-up

INTRODUCTION

The presence of a damaged labrum is one of many factors influencing the outcomes of Chiari pelvic osteotomy. However, there are few previous papers describing the long-term outcomes of Chiari pelvic osteotomy with labrectomy. The purpose of this study was to evaluate the long-term clinical and radiological outcomes of Chiari pelvic osteotomy for dysplastic hips with labral tears. We compared outcomes between labrectomy (+) and labrectomy (-) groups.

PATIENTS AND METHODS

Chiari pelvic osteotomies were performed by one surgeon on 34 dysplastic hips with labral tears between 1983 and 1996, in which labrectomy was performed on 23 hips but not on 11 hips. Three patients undergoing labrectomy were lost to follow-up evaluation within 5 years after surgery. The average age of the remaining 31 patients was 35.5 years (range, 16-54 years). The clinical and radiographic surveillance averaged 16.0 years (range, 10-23.3 years).

RESULTS

In all patients, pain disappeared after the operation. At the end of the study, 8 of the 31 patients displayed clinical deterioration. Progression of osteoarthritis (OA) was observed in 11 hips. Patients with poor results have not opted for revision surgery except for one patient. In the labrectomy (+) group, 10 of the 20 hips showed progression of OA and the clinical outcomes of 6 patients deteriorated. In the labrectomy (-) group, 1 of the 11 hips showed progression of OA and 2 patients deteriorated clinically. Radiological outcomes differed significantly between the two groups.

CONCLUSION

Labrectomy accompanying Chiari pelvic osteotomy is an acceptable procedure for relieving pain caused by the damaged labrum, but the outcomes have a tendency to deteriorate after 10 or more years postoperatively.

Distinct expression of mast cell tryptase and protease activated receptor-2 in synovia of rheumatoid arthritis and osteoarthritis

The objective of this study is to examine the differential expression of mast cell tryptase and its receptor, protease-activated receptor-2 (PAR-2), in the synovium and synovial fluid of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Biochemical and immunohistochemical analyses were performed to determine whether the trypsin-like protease in the synovium is identical to mast cell tryptase. The effects of mast cell tryptase on the proliferation of synovial fibroblast-like cells (SFCs) and the release of IL-8 thereof were evaluated by the [3H]-thymidine incorporation and ELISA, respectively. The trypsin-like protease in the synovium of RA patients was identical to human mast cell tryptase, which was composed of two subunits: 33 and 34 kDa. The 33- and 34-kDa proteins are different glycosylated forms of the 31-kDa protein, which was unglycosylated. Mast cell tryptase activity in RA synovial fluid was significantly higher than that in OA synovial fluid, while their activities and expression in the synovium were similar. Expression of PAR-2 mRNA in the synovium was higher in RA than in OA. Mast cell tryptase containing the unglycosylated 31-kDa subunit was the predominant form in synovial fluid. RA patients had higher amounts of this subunit in their synovial fluid than OA patients. Mast cell tryptase and PAR-2 activating peptide stimulated the proliferation of SFCs and release of IL-8 from these cells. Mast cell tryptase secretion into RA synovial fluid is higher than OA synovial fluid. Mast cell tryptase in synovial fluid stimulates the proliferation of SFCs and the release of pro-inflammatory cytokines via PAR-2, which may contribute to exacerbation of synovitis in RA.

Asynchronous progressive diaphyseal dysplasia

We report the case of a 42-year-old Japanese woman with unusual diaphyseal dysplasia of bilateral femora. Radiographs showed thickening and sclerosis of the cortex with resultant enlargement of the diaphysis, unclear demarcation of the surface of the cortex, and no periosteal reaction. These changes were found on the left femur at the first presentation, and those on the right femur developed within several years. Although this patient partly presented characteristics of Ribbing disease and Camurati-Engelmann disease, the focal involvement of bilateral femora suggested an unknown pathogenesis.

Bisphosphonate modulates morphological and mechanical properties in distraction osteogenesis through inhibition of bone resorption

Despite the general clinical acceptance of distraction osteogenesis and much attention to bone formation in this method, little is recognized about activated bone resorption in the regenerated bone. The purpose of this study was to demonstrate the simultaneously activated bone resorption with activated bone formation and to investigate the role and efficacy of bisphosphonate in distraction osteogenesis. Left tibiae of 54 immature rabbits were lengthened for 3 weeks at a rate of 0.7 mm/day after a 1-week lag. Regenerated bone was quantitatively investigated by radiographic bone density, bone histomorphometry, and three-point bending testing. Animals received either vehicle or nitrogen-containing bisphosphonate (N-BP), YM529/ONO5920 at doses of 0.4 mg/kg/w or 0.004 mg/kg/w for 6 weeks. Regenerated bone of the vehicle group showed a radiologically characteristic zone structure containing the osteopenic zones adjacent to the sclerotic zones. The regenerated bone of the 0.4-mg/kg/w group showed no osteopenic zones during the course and eventually became homogeneously radiodense. The bone volume corresponding to the osteopenic zone of this group was 5.6-fold greater compared with that of the vehicle group. The lengthened bone strength of this group was 3.3-fold greater in ultimate force than that of the vehicle group and equivalent to the contralateral tibia. The 0.004-mg/kg/w group had no substantial differences compared with the vehicle group, despite radiological enhancement of the mineralized front as well as somewhat delayed bone resorption. These results demonstrate that not only bone formation but also bone resorption is highly activated in the regenerated bone, implying high bone turnover. Sufficient N-BP caused a notable modulation in morphological properties of the regenerated bone through inhibition of highly activated bone resorption and eventually increased mechanical properties.