Increased cochlear otic capsule thickness and intracortical canal porosity in the oim mouse model of osteogenesis imperfecta.

Osteogenesis imperfecta (OI or brittle bone disease) is a group of genetic disorders of the connective tissues caused mainly by mutations in the genes encoding collagen type I. Clinical manifestations of OI include skeletal fragility, bone deformities, and severe functional disabilities, such as hearing loss. Progressive hearing loss, usually beginning in childhood, affects approximately 70% of people with OI with more than half of the cases involving the inner ear. There is no cure for OI nor a treatment to ameliorate its corresponding hearing loss, and very little is known about the properties of OI ears. In this study, we investigate the morphology of the otic capsule and the cochlea in the inner ear of the oim mouse model of OI. High-resolution 3D images of 8-week old oim and WT inner ears were acquired using synchrotron microtomography. Volumetric morphometric measurements were conducted for the otic capsule, its intracortical canal network and osteocyte lacunae, and for the cochlear spiral ducts. Our results show that the morphology of the cochlea is preserved in the oim ears at 8 weeks of age but the otic capsule has a greater cortical thickness and altered intracortical bone porosity, with a larger number and volume density of highly branched canals in the oim otic capsule. These results portray a state of compromised bone quality in the otic capsule of the oim mice that may contribute to their hearing loss.

Mechanisms of Bone Fragility: From Osteogenesis Imperfecta to Secondary Osteoporosis.

Bone material strength is determined by several factors, such as bone mass, matrix composition, mineralization, architecture and shape. From a clinical perspective, bone fragility is classified as primary (i.e., genetic and rare) or secondary (i.e., acquired and common) osteoporosis. Understanding the mechanism of rare genetic bone fragility disorders not only advances medical knowledge on rare diseases, it may open doors for drug development for more common disorders (i.e., postmenopausal osteoporosis). In this review, we highlight the main disease mechanisms underlying the development of human bone fragility associated with low bone mass known to date. The pathways we focus on are type I collagen processing, WNT-signaling, TGF-ß signaling, the RANKL-RANK system and the osteocyte mechanosensing pathway. We demonstrate how the discovery of most of these pathways has led to targeted, pathway-specific treatments.

Cesarean delivery is not associated with decreased at-birth fracture rates in osteogenesis imperfecta.

PURPOSE: Osteogenesis imperfecta (OI) predisposes to recurrent fractures. Patients with the moderate to severe forms of OI present with antenatal fractures, and the mode of delivery that would be safest for the fetus is not known. METHODS: We conducted systematic analyses of the largest cohort of individuals with OI (n = 540) enrolled to date in the OI Linked Clinical Research Centers. Self-reported at-birth fracture rates were compared among individuals with OI types I, III, and IV. Multivariate analyses utilizing backward-elimination logistic regression model building were performed to assess the effect of multiple covariates, including method of delivery, on fracture-related outcomes. RESULTS: When accounting for other covariates, at-birth fracture rates did not differ based on whether delivery was by vaginal route or by cesarean delivery (CD). Increased birth weight conferred higher risk for fractures irrespective of the delivery method. In utero fracture, maternal history of OI, and breech presentation were strong predictors for choosing CD. CONCLUSION: Our study, the largest to analyze the effect of various factors on at-birth fracture rates in OI, shows that CD is not associated with decreased fracture rate. With the limitation that the fracture data were self-reported in this cohort, these results suggest that CD should be performed only for other maternal or fetal indications, not for the sole purpose of fracture prevention in OI.Genet Med 18 6, 570-576.

[Clinical condition and therapy of bone diseases].

Skeletal dysplasia is the term which represents disorders including growth and differentiation of bone, cartilage and ligament. A lot of diseases are included, and new disorders have been added. However, the therapy of most bone diseases is less well-established. Achondroplasia, hypochondroplasia, and osteogenesis imperfecta are most frequent bone diseases. There is no curative treatment for these diseases, however, supportive therapies are available ; for example, growth-hormone therapy for achondroplasia and hypochondroplasia, and bisphosphonate therapy for osteogenesis imperfecta. In addition, enzyme replacement therapy for hypophosphatasia is now on clinical trial.

Mutation characteristics in type I collagen genes in Chinese patients with osteogenesis imperfecta.

Osteogenesis imperfecta is normally caused by an autosomal dominant mutation in the type I collagen genes COL1A1 and COL1A2. The severity of osteogenesis imperfecta varies, ranging from perinatal lethality to a very mild phenotype. Although there have been many reports of COL1A1 and COL1A2 mutations, few cases have been reported in Chinese people. We report on five unrelated families and three sporadic cases. The mutations were detected by PCR and direct sequencing. Four mutations in COL1A1 and one in COL1A2 were found, among which three mutations were previously unreported. The mutation rates of G>C at base 128 in intron 31 of the COL1A1 gene and G>A at base 162 in intron 30 of the COL1A2 gene were higher than normal. The patients' clinical characteristics with the same mutation were variable even in the same family. We conclude that mutations in COL1A1 and COL1A2 also have an important role in osteogenesis imperfecta in the Chinese population. As the Han Chinese people account for a quarter of the world's population, these new data contribute to the type I collagen mutation map.

[Prenatal diagnose of abnormalities of fetal limb bone].

OBJECTIVE: to discuss the prenatal diagnosis of abnormalities of fetal limb bone. METHODS: we selected 18 cases which long bone of fetus less than 2SD of average volume of gestational weeks or long bone changed into angle or other fetus's abnormalities by first B-mode ultrasonic. All above cases was delivered at Capital Medical University of Obstetric and Gynecological Hospital during Jan. 2006 to Dec. 2009. We B-mode ultrasonic was used to measure fetus's biparietal diameter (BPD), femur length (FL), abdominal circumference (AC), head circumference (HC), humerus length (HL), amniotic fluid index (AFI) and structures of organ and calculated FL/AC, growth speed of long bone. The standard of achondroplasia is that FL and HL are less than 4SD of average of gestational weeks or FL/AC less than 0.16. The standard of Osteogenesis Imperfecta is fetal long bone of fetus shows short and thick, curves into angle, fracture in uterus by X-ray, or skull shows thin or sink by X-ray. RESULTS: (1) by B-mode ultrasonic and X-ray exam of all 18 cases: 7 cases shows that HC > 2SD, 10 cases shows too much amniotic fluid, 12 cases shows AFI > 18.0, 9 cases shows abnormalities of narrow cavitas thoracis, disordered vertebral column, or unusual architecture of heart. For cases 1 to 14 are achondroplasia, among which, 11 cases are FL < 4SD and HL < 4SD, 2 cases are FL < 3SD and HL < 4SD, 1 case is not only FL < 2SD and HL < 3SD but also hydroncus all over the body of fetus. The growth velocity of long bone of fetus in all the 14 cases is more slowly than the normal rate. For all the above 14 cases, 12 cases FL/AC < 0.16, 1 case FL/AC = 0.19, 1 case FL/AC = 0.20. The length of femur or humerus is shorter than the normal rate and have other abnormalities the above last two cases. For case 15 and 16, they don't show any abnormalities of bone growth though one year's follow up studying. For case 17 and 18, they are osteogenesis imperfecta. (2) The result of fetal perinatal period fate and autopsy: there are 8 female and 10 male in all the 18 cases. One case is labored after 39 weeks pregnancy, and it is low birth weight infant, weight < 3%th. All the other cases are normally birth weight infant. All the 18 cases of abnormalities of fetal limb bone are examined by chromosomes check, among which, 9 cases are amniocentesis, 7 cases are cordocentesis, 2 cases are checked chromosomes by fetus cord blood, all the caryotype are normal. In the 16 autopsy cases, 14 cases are achondroplasia or hypochondroplasis. It can be seen amplifying extremities, hyperplasia chondrocytes of tubiform born, karyomegaly, anachromasis, hyperplasia capillaries though microscope and grow up into cartilage irregularly. Also can be seen hyperplasia chondrocytes of epiphyses, delaying osteosis. 2 cases are osteogenesis imperfecta. It can be seen broadening of metaphyses, exility of bone trabeculae. For the other two cases which the fetus is alive, we do the follow up studying to their one year old one of them is low birth weight new born, their limb and height are all normal. CONCLUSIONS: to diagnose fetal Achondroplasia, it is not only based on the significantly shorter of femur or humerus length but also based on the dynamics observing the long bone growth velocity and calculating FL/AC. For osteogenesis imperfecta fetus, it should be diagnosed by fractures in uterus though X-ray.

Osteogénesis Imperfecta / Osteogenesis Imperfecta

La osteogenesis imperfecta (OI) es un grupo de trastornos del tejido conectivo que genera anomalías esqueléticas caracterizadas por fragilidad y deformidades óseas. Las características genéticas son variables y se han descrito nuevos subgrupos los últimos años agregando información a las clasificaciones tradicionales. Su incidencia es de 1/10.000 a 20.000 RN vivos. Existe un amplio espectro de manifestaciones clínicas, que van desde una leve fragilidad ósea, en niños asintomáticos, hasta versiones que son letales al momento de nacer. El diagnóstico es principalmente clínico y debe diferenciarse de otras anomalías del esqueleto que producen fragilidad y de lesiones por maltrato infantil. El tratamiento es multidisciplinario y está orientado a mejorar la calidad de vida de los pacientes. Para lo que se debe mejorar la densidad ósea, a través de medicamentos, buena musculatura y cargas fisiológicas. Las fracturas se tratan con períodos cortos de inmovilización y carga precoz, o con cirugías que limiten el tiempo de inmovilización. Por otro lado, las deformidades esqueléticas deben tratarse en forma quirúrgica utilizando osteosíntesis que sean extensibles y mantengan la corrección a medida que el niño crece. El manejo coordinado de los distintos profesionales involucrados es de gran importancia para lograr los mejores resultados en esta enfermedad crónica que involucra al niño y todo su entorno

Osteogenesis Imperfecta (OI) is a group of connective tissue disorders involved in skeletal abnormalities characterized by bone fragility and deformities. Genetic abnormalities are variable and new subgroups have been described recently, adding information to traditional classifications. There is a wide spectrum of clinical manifestations, ranging from mild bone fragility, in otherwise asymptomatic children, to versions that are lethal at birth. Its incidence is 1/10.000-20.000 newborns. The diagnosis is mainly clinical and must be distinguished from other skeletal abnormalities and child abuse. The treatment is multidisciplinary, and it is aimed to improve the quality of life of patients. For which the bone density must be improved, through medications, strong musculature, and physiological loads. Fractures are treated by immobilizing for short periods, trying to load at soon as possible, or by surgeries that limit immobilization time. On the other hand, skeletal deformities should be treated surgically using dynamic rods that are extensible and maintain correction as the child grows. The coordinated management of the different professionals involved is of the utmost importance to achieve the best results in this chronic disease that involves the child and his entire environment

A cryptic balanced translocation involving COL1A2 gene disruption cause a rare type of osteogenesis imperfecta.

BACKGROUND: Osteogenesis imperfecta (OI) is a group of hereditary disorders characterized by low bone mass and recurrent fractures. Most OI cases follow an autosomal dominant pattern of inheritance and are attributed to mutations in genes encoding type I collagen (COL1A1/COL1A2). Genomic structural variations involving type I collagen genes are extremely rare in OI. CASE REPORT: In this study, we characterized a de novo balanced translocation of t(5;7)(q32;q21.3) that caused an extremely rare type of OI in a patient from a non-consanguineous family. The clinical phenotypes of this OI included recurrent fractures, low bone mass, macrocephaly, blue sclera and failure to thrive. Next-generation sequencing was used to identify the translocation, and Sanger sequencing was used to validate and map the breakpoints. The breakpoint on chromosome 7 disrupted the COL1A2 gene in the 17th exon, presumed to affect type I collagen production and give rise to OI. The breakpoint on chromosome 5 disrupted the protein phosphatase 2 regulatory subunit B, beta gene (PPP2R2B) within the first intron. CONCLUSIONS: This is the first report of a copy-neutral structural variant involving COL1A2 that leads to a rare type of OI. This study expands the genotypic spectrum of OI and demonstrates the effectiveness of targeted sequencing for breakpoint mapping.

Changes in thermal stability and microunfolding pattern of collagen helix resulting from the loss of alpha2(I) chain in osteogenesis imperfecta murine.

Homozygous mutations resulting in formation of alpha1(I)(3) homotrimers instead of normal type I collagen cause mild to severe osteogenesis imperfecta (OI) in humans and mice. Limited studies of changes in thermal stability of type I homotrimers were reported previously, but the results were not fully consistent. We revisited this question in more detail using purified tendon collagen from wild-type (alpha1(I)(2)alpha2(I) heterotrimers) and oim (alpha1(I)(3)) mice as well as artificial alpha1(I)(3) homotrimers obtained by refolding of rat-tail-tendon collagen. We found that at the same heating rate oim homotrimers completely denature at approximately 2.5deg.C higher temperature than wild-type heterotrimers, as determined by differential scanning calorimetry. At the same, constant temperature, homotrimers denature approximately 100 times slower than heterotrimers, as determined by circular dichroism. Detailed analysis of proteolytic cleavage at different temperatures revealed that microunfolding of oim homotrimers and wild-type heterotrimers occurs at similar rate but within a number of different sites. In particular, the weakest spot on the oim triple helix is located approximately 100 amino acid residues from the C-terminal end within the cyanogen bromide peptide CB6. The same microunfolding site is also present in wild-type collagen, but the weakest spot of the latter is located close to the N-terminal end of CB8. Amino acid analysis and differential gel electrophoresis showed virtually no posttranslational overmodification of oim mouse tendon collagen. Moreover, thermal stability and microunfolding of artificial rat-tail-tendon homotrimers were similar to oim homotrimers. Thus, the observed changes are associated with difference in the amino acid composition of alpha1(I) and alpha2(I) chains rather than posttranslational overmodification.

Testing for osteogenesis imperfecta in cases of suspected non-accidental injury.

To evaluate if laboratory testing for osteogenesis imperfecta (OI) identifies children unrecognised by clinical examination in instances where non-accidental injury (NAI) is suspected as the likely cause of fracture, we carried out a retrospective review of available medical records and biochemical test results from 262 patients. Cultured fibroblasts were received for biochemical testing for OI from children in whom the diagnosis of NAI was suspected. Eleven of the samples had alterations in the amount or structure of type I collagen synthesised, consistent with the diagnosis of OI, and in 11 others we could not exclude OI. Referring physicians correctly identified children with OI in six of the 11 instances established by biochemical studies, did not identify OI by clinical examination in three, and there was inadequate clinical information to know in two others. Biochemical testing was inconclusive in 11 infants in whom the diagnosis of OI could not be excluded, none of whom were thought to be affected by the referring clinicians. Four children believed to have OI by clinical examination had normal biochemical studies, a false positive clinical diagnosis attributed, in large part, to the use of scleral hue (a feature that is age dependent) as a major diagnostic criterion. Given the inability to identify all children with OI by clinical examination in situations of suspected NAI, laboratory testing for OI (and other genetic predispositions for fractures) is a valuable adjunct in discerning the basis for fractures and may identify a small group of children with previously undiagnosed OI.

Mutations in type 1 procollagen that cause osteogenesis imperfecta: effects of the mutations on the assembly of collagen into fibrils, the basis of phenotypic variations, and potential antisense therapies.

Work by a large number of investigators over the last decade has established that over 90% of patients with osteogenesis imperfecta have mutations in one of the two genes for type I procollagen, that most unrelated probands have different mutations in the genes, and that the mutations found in most of the serious variants of the disease cause synthesis of abnormal pro alpha chains of the protein. The results have demonstrated that synthesis of structurally abnormal but partially functional pro alpha chains can interfere with folding of the central region of the protein into a triple-helical conformation, prevent processing of the N-terminal propeptides of procollagen, or produce subtle alterations in conformation that interfere with the self-assembly of the protein into collagen fibrils. One of the unsolved mysteries about the disease is why some mutations produce severe phenotypes, whereas very similar mutations produce mild phenotypes. Recent studies in transgenic mice suggest that nongenetic factors, such as stochastic events during development, may determine the severity of the disease phenotype produced by a specific mutation. Also, recent results raised the possibility that strategies of antisense gene therapy may be effective in treating the disease some time in the future. Specific inhibition of expression of a mutated collagen gene has been obtained with antisense oligonucleotides in cell culture experiments. However, there is no means of selective delivery of antisense oligonucleotides to the appropriate tissues.

Heterozygous oim mice exhibit a mild form of osteogenesis imperfecta.

The oim strain of mice is one of several rodent models that exhibit an osteogenesis imperfecta (OI) phenotype. These mice have a mutation in the gene encoding alpha-2 chain of type I procollagen that prevents proper assembly of this propeptide with alpha-1 propeptides. Homozygous oim mice experience multiple bone fractures under standard laboratory animal housing conditions and are representative of moderate to severe forms of OI. Because fractures are not typically experienced by heterozygous oim mice, they have not been studied extensively. The present studies show that the organization of cortical bone is deficient in heterozygotes, exhibiting a morphology intermediate to specimens from homozygotes and wild-type mice. The biomechanical properties of femurs isolated from heterozygous oim mice are also intermediate to homozygotes and wild-type mice when tested in four-point bending. Although it is not possible to distinguish visually between heterozygous oim and wild-type mice, the quality and biomechanical properties of bone in heterozygotes is significantly reduced by twelve weeks of age. Heterozygous oim mice are useful as a model for a mild form of OI.

Possible role of overglycosylation in the type I collagen triple helical domain in the molecular pathogenesis of osteogenesis imperfecta.

The underlying defect in patients affected by a form of osteogenesis imperfecta (OI) clarified at the molecular level regards the amount or the structure of type I collagen synthesized. This leads to a decreased and/or abnormal mineral deposition in bone and affects bone mass and/or strength. Abnormal interactions between collagen molecules in the presence of mutant trimers could give rise to abnormal fibrils, which, in turn, can determine incorrect interactions with noncollagenous matrix macromolecules. The interactions can be disturbed or modulated by an abnormal distribution on the collagen fibril surface of electrically charged or hydrophobic groups, or by an increased presence of sugar moieties linked to hydroxylysyl residues due to chain post-translational overmodifications (lysyl overhydroxylation and hydroxylysyl overglycosylation) of the portion of the triple helical domain of abnormal type I collagen molecules N-terminal with respect to the defect localization.

Excess paternal age in apparently sporadic osteogenesis imperfecta.

The objective of this study was to examine whether parental age is associated with the occurrence of apparently sporadic osteogenesis imperfecta (OI). We compared parental age and the joint distribution of maternal and paternal age with expected distributions based on statutory birth records for each year and location of birth. The study included patients with OI based in the United Kingdom. The study was restricted to cases born in England, Wales, and Scotland between 1961 and 1998. Subgroup analysis was by clinical type [Sillence et al., 1979: J Med Genet 16:101-116] and apparent mode of inheritance based on pedigree analysis. Of 730 eligible cases, 357 were apparently sporadic. The mean age of fathers at birth of children with apparently sporadic OI was 0.87 years greater than expected (P = 0.010; 95% confidence interval = 0.21 to 1.54 years). The relative risk was 1.62 for fathers in the highest quintile of paternal age compared with fathers in the lowest quintile. The magnitude of the paternal age excess did not differ significantly between Sillence types (analysis of variance P = 0.534). In sporadic cases, paternal age was 0.51 years greater than expected, given maternal age, year, and location of birth (P = 0.033). In contrast, in familial cases, there was no significant paternal age excess, and paternal age was not significantly different from that expected given maternal age. Increased paternal age is a significant risk factor for sporadic OI. This effect is not accounted for by increasing maternal age. The magnitude of the paternal age excess is small in comparison with that in some other autosomal dominant disorders.

Interaction between osteoblast and osteoclast: impact in bone disease.

The intercellular communication between osteoblasts and osteoclasts is crucial to bone homeostasis. Since Rodan and Martin proposed the control of osteoclasts by osteoblasts in the 1980s, many factors have been isolated from osteoblasts and shown to regulate the differentiation and function of osteoclasts. However, the mechanism by which osteoblasts regulate osteoclasts during bone remodelling is still unclear. On the other hand, it is well accepted that many metabolic bone diseases are associated with the disruption of the communication between osteoblast and osteoclasts. Thus, this review focuses on the cross-talk between osteoblasts and osteoclasts and its impact in bone disease.

The role of dual energy x-ray absorptiometry in aiding the diagnosis of pediatric osteogenesis imperfecta.

The role of dual energy x-ray absorptiometry (DEXA) in the evaluation of the pediatric patient with multiple fractures has not been well established. We retrospectively examined the medical records of 45 patients who had presented to our institution with multiple fractures of unknown cause, who were not known to have osteogenesis imperfecta, and who had obtained DEXA as part of their evaluation. Of these, 26 patients had sufficient clinical data for inclusion in this study. Patients underwent DEXA of the anteroposterior spine and whole body. A z score was calculated to normalize the DEXA values for age. The diagnosis of osteogenesis imperfecta was correlated with the outcome of each DEXA scan to assess the validity of DEXA as a diagnostic tool. The DEXA of the anteroposterior spine had the highest sensitivity at 91.7%, while DEXA of the whole body had the highest specificity at 100.0%. Decreased bone mineral density may be associated with osteogenesis imperfecta, and DEXA is helpful in detecting low bone mineral density that may be missed on plain radiographs of children with milder forms of osteogenesis imperfecta.

[Developmental bone abnormalities, their variants and the delay of osteogenesis in children with leukemia]. / Csontfejlödési rendellenességek, variánsok és csontosodási kor lemaradása leukémiás gyermekekben.

When analyzing the Roentgen documentation of 102 leukaemic children, the prevalence of bone anomalies of the extremities, pelvis and vertebral column was studied. The frequency of the abnormal or unusual findings was compared with that of 660 control subjects. The frequency of osseous anomalies proved to be 2 to 3 times higher in leukaemic children tha in the controls. Considering the number of ossification centers and the presence nutritional canal of vertebrae, in leukaemic children the ossification seemed to be retarded.

[Osteoporosis in congenital disorders].

Osteogenesis imperfecta (OI) is the most prevalent osteoporosis syndrome in childhood and is characterized by fractures and skeletal deformities. In almost all individuals, OI results from mutations in one of the two genes (COL1A1 and COL1A2) that encode the chains of type I collagen. OI can be divided into four major groups, type I, II, III, and IV, that differ in clinical presentation, mode of inheritance, radiographic picture, and, for the most part, the biochemical basis of the connective disorder. The molecular basis of OI is mainly discussed.

[Children with osteogenesis imperfecta. An infrequent but important disease]. / El niño con osteogénesis imperfecta. Una enfermedad infrecuente pero importante.

Imperfect osteogenesis is a disease which is included in the group of the osseous dysplasias having a heterogeneous genetic character and whose basic defect is an alteration in the synthesis of Procollagen I. This leads to a serious fragility in skeletal structures as well as in exoskeletal structures, causing multiple fractures and deformities. The absence of a truly effective medical, surgical or orthopedic treatment makes correctly planned nursing care acquire vital importance in order to succeed in avoiding, and diminishing, fractures and deformities due to an inadequate handling of these patients; while to the contrary contributing to success in integrating these patients into society in the best possible conditions. This is the first of two articles which the authors will dedicate to this disease; this disease will be described in this first article, while the second one will concentrate exclusively on nursing treatments recommended for patients suffering from this disease.