Ichiro Owan

Constitutively Activated ALK2 and Increased SMAD1/5 Cooperatively Induce Bone Morphogenetic Protein Signaling in Fibrodysplasia Ossificans Progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder characterized by congenital malformation of the great toes and by progressive heterotopic bone formation in muscle tissue. Recently, a mutation involving a single amino acid substitution in a bone morphogenetic protein (BMP) type I receptor, ALK2, was identified in patients with FOP. We report here that the identical mutation, R206H, was observed in 19 Japanese patients with sporadic FOP. This mutant receptor, ALK2(R206H), activates BMP signaling without ligand binding. Moreover, expression of Smad1 and Smad5 was up-regulated in response to muscular injury. ALK2(R206H) with Smad1 or Smad5 induced osteoblastic differentiation that could be inhibited by Smad7 or dorsomorphin. Taken together, these findings suggest that the heterotopic bone formation in FOP may be induced by a constitutively activated BMP receptor signaling through Smad1 or Smad5. Gene transfer of Smad7 or inhibition of type I receptors with dorsomorphin may represent strategies for blocking the activity induced by ALK2(R206H) in FOP.

The role of calcitonin gene-related peptide (CGRP) in macrophages: the presence of functional receptors and effects on proliferation and differentiation into osteoclast-like cells

It has been shown that both calcitonin gene-related peptide (CGRP) and amylin bind weakly to calcitonin (CT) receptors in osteoclast-like cells formed in vitro and inhibit bone resorption by a cAMP-dependent mechanism. Osteoclasts are thought to be derived from cells of the monocyte macrophage lineage, in which CGRP, but not CT, induces cAMP production. In this study, we determined the presence of functional receptors for CGRP in mouse alveolar macrophages and the effects of this peptide on proliferation and osteoclastic differentiation in mouse alveolar and bone marrow-derived macrophages. Human CT did not stimulate cAMP production in macrophages. Human CGRP stimulated cAMP production in mouse alveolar macrophages and bone marrow-derived macrophages dose-dependently. Human amylin, which has 43% homology with human CGRP, also stimulated these macrophages to produce cAMP, but only at a 100-fold higher concentration. The increment in cAMP production induced by human CGRP and amylin was abolished by the addition of human CGRP(8-37), a selective antagonist for CGRP receptors. Specific binding of [125I]human CGRP to alveolar macrophages was detected (dissociation constant, 2.5 x 10(-8) M; binding sites, 1.4 x 10(4)/cell). Amylin, but not CT, displaced the bound [125I]human CGRP from alveolar macrophages, but at a 100-fold higher concentration. No specific binding of [125I]human CT and [125I]human amylin to alveolar macrophages could be detected. Pretreatment with human CGRP for 24 h dose-dependently suppressed DNA synthesis in alveolar macrophages induced by granulocyte-macrophage colony-stimulating factor (GM-CSF). CGRP also suppressed the number of macrophage colonies formed from bone marrow cells induced by macrophage colony-stimulating factor (M-CSF).(ABSTRACT TRUNCATED AT 250 WORDS)

A unique mutation of ALK2, G356D, found in a patient with fibrodysplasia ossificans progressiva is a moderately activated BMP type I receptor

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant congenital disorder characterized by progressive heterotopic bone formation in muscle tissues. A common mutation among FOP patients has been identified in ALK2, ALK2(R206H), which encodes a constitutively active bone morphogenetic protein (BMP) receptor. Recently, a unique mutation of ALK2, ALK2(G356D), was identified to be a novel mutation in a Japanese FOP patient who had unique clinical features. Over-expression of ALK2(G356D) induced phosphorylation of Smad1/5/8 and activated Id1-luc and alkaline phosphatase activity in myoblasts. However, the over-expression failed to activate phosphorylation of p38, ERK1/2, and CAGA-luc activity. These ALK2(G356D) activities were weaker than those of ALK2(R206H), and they were suppressed by a specific inhibitor of the BMP-regulated Smad pathway. These findings suggest that ALK2(G356D) induces heterotopic bone formation via activation of a BMP-regulated Smad pathway. The quantitative difference between ALK2(G356D) and ALK2(R206H) activities may have caused the phenotypic differences in these patients.

Multiinstitutional epidemiological study regarding osteoarthritis of the hip in Japan

Background. Osteoarthritis (OA) of the hip is a major disease that affects the healthy lifespan of a population. It is necessary to fully understand the patients’ conditions before a systematic treatment can be applied. However, a nationwide epidemiological study regarding hip OA has not yet been conducted in Japan. The present study examined the current status of patients with hip OA, including the disease etiology. Methods. This is a multiinstitutional study of new patients presenting with hip OA at the orthopedic outpatient clinics of 15 institutions in fi ve geographical areas of Japan. The collected data from each patient included the sex, age, treatment history for developmental dysplasia of the hip (DDH), the clinical score of the hip joints based on the Japanese Orthopaedic Association (JOA) scoring system, and the pelvic inclination according to anteroposterior radiographs. In addition, the etiology was determined from the following 17 options: primary OA, acetabular dysplasia, intragluteal dislocation, osteonecrosis, trauma, Perthes disease, slipped capital femoral epiphysis, infection, rheumatoid arthritis, ankylosing spondylitis, neuroarthropathy, endocrine diseases, metabolic diseases, hereditary bone diseases, synovial chondromatosis, generalized OA, and others. Results. There were a substantially larger number of female patients than male patients. This difference regarding sex was present in each generation. The mean age of the patients was 58 ± 14 years. The peak age at presentation was approximately 50 years. Most patients had no history of therapy for DDH. The older patients had lower gait and activities of daily living scores. The etiology was assessed to be acetabular dysplasia in most of the patients. A lower frequency of elderly patients demonstrated acetabular dysplasia. The patients who had a pelvic posterior inclination increased with increasing age. Conclusions. The patients with hip OA in Japan were unique in regard to age distribution, sexual heterogeneity, and disease

Mutations in CD96, a Member of the Immunoglobulin Superfamily, Cause a Form of the C (Opitz Trigonocephaly) Syndrome

The C syndrome is characterized by trigonocephaly and associated anomalies, such as unusual facies, psychomotor retardation, redundant skin, joint and limb abnormalities, and visceral anomalies. In an individual with the C syndrome who harbors a balanced chromosomal translocation, t(3;18)(q13.13;q12.1), we discovered that the TACTILE gene for CD96, a member of the immunoglobulin superfamily, was disrupted at the 3q13.3 breakpoint. In mutation analysis of nine karyotypically normal patients given diagnoses of the C or C-like syndrome, we identified a missense mutation (839C-->T, T280M) in exon 6 of the CD96 gene in one patient with the C-like syndrome. The missense mutation was not found among 420 unaffected Japanese individuals. Cells with mutated CD96 protein (T280M) lost adhesion and growth activities in vitro. These findings indicate that CD96 mutations may cause a form of the C syndrome by interfering with cell adhesion and growth.

A novel mutation of ALK2, L196P, found in the most benign case of fibrodysplasia ossificans progressiva activates BMP-specific intracellular signaling equivalent to a typical mutation, R206H

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant congenital disorder characterized by progressive heterotopic ossification in muscle tissues. Constitutively activated mutants of a bone morphogenetic protein (BMP) receptor, ALK2, have been identified in patients with FOP. Recently, a novel ALK2 mutation, L196P, was found in the most benign case of FOP reported thus far. In the present study, we examined the biological activities of ALK2(L196P) in vitro. Over-expression of ALK2(L196P) induced BMP-specific activities, including the suppression of myogenesis, the induction of alkaline phosphatase activity, increased BMP-specific luciferase reporter activity, and increased phosphorylation of Smad1/5 but not Erk1/2 or p38. The activities of ALK2(L196P) were higher than those of ALK2(G356D), another mutant ALK2 allele found in patients with FOP and were equivalent to those of ALK2(R206H), a typical mutation found in patients with FOP. ALK2(L196P) was equally or more resistant to inhibitors in comparison to ALK2(R206H). These findings suggest that ALK2(L196P) is an activated BMP receptor equivalent to ALK2(R206H) and that ALK2(L196P) activity may be suppressed in vivo by a novel molecular mechanism in patients with this mutation.

Osteoarthritis hip joints in Japan: involvement of acetabular dysplasia

BackgroundWe conducted a nationwide epidemiologic study regarding hip osteoarthritis (OA) in Japan, and a previous report found these patients to be unique in comparison to Caucasians. This report focused on the data regarding each hip joint, and the involvement of acetabular dysplasia with hip OA was analyzed.MethodsSeven hundred twenty OA hips were examined. Sixty-five joints with osteonecrosis of the femoral head and 215 non-OA contralateral joints of the unilateral patients were examined as controls. The revised system of stage classification for hip OA of the Japanese Orthopedic Association (JOA) was used according to the reproducibility in order to ensure reliable data from the multiple institutions. The acetabular dysplasia indexes were also chosen according to the reproducibility and measured in the radiograph of bilateral hip joints. The clinical score was assessed using the JOA scoring system. The relative risk of the grade of acetabular dysplasia indexes for hip OA was calculated as the odds ratio and the 95% confidence interval.ResultsThe stage of the OA joints deteriorated with increasing age. The clinical scores also decreased. The grade of the acetabular dysplasia indexes of the OA joints was significantly higher than that of the control joints. Each index of acetabular dysplasia demonstrated significantly increased odds ratios for hip OA. Among the OA joints, the deterioration of the OA stage was found to be significantly associated with an increasing grade of acetabular dysplasia. The odds ratio for OA deterioration in the acetabular dysplasia index was also obtained. The joints of females tended to have a higher grade and prevalence of acetabular dysplasia than those of males.ConclusionsThese findings confirmed a high prevalence of acetabular dysplasia in hip OA joints in Japan. Acetabular dysplasia was one of the most important factors associated with hip OA.

Analysis of interobserver reliability for radiographic staging of coxarthrosis and indexes of acetabular dysplasia : a preliminary study

BackgroundWe are planning a multicenter survey on coxarthrosis and acetabular dysplasia in Japan. To collect reliable data, we performed a preliminary study to elucidate the observer agreement on assessment items.MethodsWe collected radiographs of hip joints in eight patients with various findings of coxarthrosis. Twelve registered orthopedic specialists evaluated them regarding the roentgenographic stage of coxarthrosis and five indexes of acetabular dysplasia (acetabular angle, center-edge angle, acetabular roof obliquity, acetabular head quotient, approximate acetabular quotient). To assess observer agreement, we calculated the value of the kappa statistic for stages and the coefficient of variation for the indexes. The same 12 specialists then assessed the coxarthritis stage on the same radiographs 1 month after the first evaluation based on our own descriptions of the roentgenographic stages.ResultsFor the first evaluation of the roentgenographic stage, the value of the kappa statistic was 0.448; and for the second evaluation it was 0.600. The results of the coefficient of variation for the indexes of acetabular dysplasia, ranked in ascending order, were as follows: acetabular angle, acetabular head quotient, acetabular roof obliquity, center-edge angle, approximate acetabular quotient.ConclusionsFor the upcoming multicenter survey, clear descriptions of the stages of coxarthrosis and selection of appropriate indexes can be helpful for collecting dependable results.

Relationship of acetabular dysplasia in females with osteoarthritis of the hip to the distance between both anterior superior iliac spines

Background Acetabular dysplasia (AD) is the main cause of hip osteoarthritis in Japan. A simple method to evaluate acetabular dysplasia would be helpful for early treatment or prevention of hip osteoarthritis. Acetabular dysplasia is reported to be associated with pathological transverse growth of the pelvis, indicating that the distance between the 2 anterior superior iliac spines might be useful for screening and detection of acetabular dysplasia. The purpose of this study was to determine if the acetabular dysplasia radiographic parameters are related to the distance between the 2 anterior superior iliac spines in patients with hip osteoarthritis. Material/Methods In this study, data obtained in a previous multi-institutional examination of patients with hip osteoarthritis in Japan were evaluated. The anterior superior iliac spine distances of 176 female patients (mean age, 54 years; range, 18–85 years) were measured by physical examination. The relationship between the anterior superior iliac spine distance and acetabular dysplasia was analyzed, and the anterior superior iliac spine distances of the patients with acetabular dysplasia who were at relatively high risk for hip osteoarthritis were compared with that of the patients at lower risk. Results A statistically significant relationship between the anterior superior iliac spine distance and all of the acetabular dysplasia parameters was observed. The anterior superior iliac spine distances of the acetabular dysplasia patients with a relatively high risk for radiographic acetabular dysplasia parameters were significantly smaller than those of patients at lower risk. Even after adjustment for age, height, and weight, significantly increased relative risk for having high risk AD was found in patients with an ASIS distance of less than 24.5 cm. Conclusions There was a significant relationship between the anterior superior iliac spine distance and the degree of acetabular dysplasia.

Factors associated with functional limitations in the daily living activities of Japanese hip osteoarthritis patients

As society ages, there is a vast number of elderly people with locomotive syndrome. In this study, the factors associated with functional limitations in daily living activities evaluated by female hip osteoarthritis (OA) patients were investigated.