Regulation and organization of connective tissues

It is difficult to study the regulation and interactions of the connective tissue macromolecules in vivo. However, studies of genetically determined diseases of the connective tissues have yielded a large amount of new information in these areas. Specific molecular defects can then be correlated with the functional and pathological changes in the tissues. We have concentrated on this approach which takes advantage of the large number of families with genetic diseases who come to our Hospital from all parts of Australasia and also takes advantage of developments in molecular biology in our Unit which were initiated with a RACS John Mitchell Crouch Fellowship. In addition to these studies on naturally occurring mutations we are also studying specific mutations that we are able to produce in specific regions of the collagen molecule. Another approach takes advantage of a unique model culture system developed in our Unit. These studies will be supplemented by various collaborative projects such as current ones involving smooth muscle cells in atherosclerosis, bone cells metabolism and myelofibrosis in leukaemia.

The spine in osteogenesis imperfecta

The natural history and treatment of spinal deformity is presented in light of the radiographic severity of the disease. The radiographic findings are grouped according to the changes over time and are prognostically significant for ambulation, spinal deformity, and life span.

Osteogenesis imperfecta

Major advances have occurred in the classification of OI and in the definition of underlying molecular defects. A clearer understanding of the pathogenesis of OI and of the relationships between the phenotypes and genotypes should emerge. The study of induced mutations in selected regions of the collagen genes with expression in cultured cells or transgenic mice should hasten this process. These advances will also provide a basis for studies into the large number of other genetically determined connective tissue disorders that are grouped together as the skeletal dysplasias. The results of recent studies in OI are providing a unique insight into many aspects of collagen and connective tissue biochemistry, physiology and pathology.

Perinatal lethal osteogenesis imperfecta: radiologic and pathologic evaluation of seven prenatally diagnosed cases

The radiologic and pathologic characteristics of 7 cases of lethal osteogenesis imperfecta (OI), diagnosed prenatally by ultrasound in the 15th to 34th week, are described. They include four variants of the Sillence classification: types IIA, IIB, IIC, and type III. The radiologic criteria that differentiate these types of OI are described. The histopathology of the bones differed only slightly in types IIA, IIB, and III; OI type IIC, however, differed markedly from the other types.

Osteogenesis imperfecta type III: an ancient mutation in Africa?

In a survey of institutions for crippled persons in Zimbabwe, 58 patients with osteogenesis imperfecta (OI) were identified; 42 had the rare OI Type III. The Shona and Ndebele people, who comprise the major tribal groups in Zimbabwe, both had a similar and relatively high gene frequency for this disorder. Both tribes were derived from common progenitors, but until 150 years ago had been geographically separated for 2 millenia. Subsequently, they have remained culturally and socially distinct. The implications are that the mutation for OI III in Africa occurred at least 2,000 years ago.

Osteogenesis imperfecta

It is now virtually certain that the brittle bone syndrome results from a variety of mutations in the alpha chains of type I collagen. Whilst the increasing biochemical knowledge makes prenatal diagnosis sometimes possible, the care of those with severe physical disability still provides a clinical challenge which is not always met. Future research in this disease therefore needs to be clinical as well as biochemical.

Psychosocial aspects of osteogenesis imperfecta

Osteogenesis imperfecta is a heterogeneous group of inherited disorders characterized by bone fragility and recurrent fractures. It is currently classified into four types on clinical grounds and appears to arise from different disorders of bone collagen synthesis. The biochemical identification of disturbances in collagen metabolism and the genetic delineation of new mutations of collagen genes have made prenatal diagnosis by molecular methods feasible in some cases. Most people with osteogenesis imperfecta suffer frequent fractures (and sometimes consequent serious disability), for which there are few effective preventive measures. This disorder may have a profound psychosocial influence on patients and their families. In this report the extent of this influence is reviewed and aspects important to the medical community are highlighted; these include the emotional burdens imposed by unfounded suspicions of child abuse, the social and financial costs of repeated hospitalization and immobility, and the frustrations generated by the lack of helpful, practical information for families and health care workers. An important social outcome has been the rise of self-help organizations, exemplified by the Canadian Osteogenesis Imperfecta Society. For Canadian families the society has been an important vehicle for exchange of information and an active, positive response to a lifelong, often severely disabling disorder.

Isolation and characterization of bone cells from a patient with osteogenesis imperfecta type 1b

The metabolic defect(s) in bone cells which manifests itself in the disease osteogenesis imperfecta (OI) type 1 is not known. Since this form of the disease displays both a variable tissue involvement and the possibility of remission it is difficult to attribute its expression to a primary mutation in the structural gene for type I collagen (as can the perinatal lethal forms of OI). In an attempt to more fully understand OI type 1 we have isolated and characterized a subpopulation of cells obtained from a sample of bone from a patient with OI type 1b. This subpopulation of cells has been shown to morphologically resemble the osteoblast phenotype, to contain the highest level of alkaline phosphatase of the cells isolated, to synthesize collagen, to respond to bone target hormones such as 1,25(OH)2D3 and parathyroid hormone, and to proliferate rapidly. Moreover, the response of these cells to the vitamin D metabolites, from the standpoint of growth regulation, is qualitatively different from normal bone cells. We intend to use these cells as a model system for studying the defect in OI type 1b.

[Genetic heterogeneity of osteogenesis imperfecta. Study of 6 cases]

Osteogenesis imperfecta one of the most common disorders of connective tissue, has been known for centuries. The most characteristic alterations which define it are: osteoporosis, osseous fragility with multiple fractures, blue sclerae, deafness and imperfect dentinogenesis. Important advances in the biochemical, anatomopathological, genetic, therapeutic and prophylactic fields have resulted in a great present-day interest in this disease. In this work we report six cases of osteogenesis imperfecta according to the current classification and we review the most outstanding aspects.

Heterogeneity of osteogenesis imperfecta. Biochemical and morphological findings in a case of type III according to Sillence

A male infant with pale-blue sclerae, who died at the age of 6 weeks through the aspiration of food, presented multiple fractures and deformation of the long tubular bones. The clinical and radiological findings and the course indicated osteogenesis imperfecta, type III, according to Sillence's classification. The family history was unremarkable. Light and electron microscopic studies of iliac crest bone obtained postmortem, showed an abrupt interruption of endochondral ossification, with an active periosteal ossification. In the region of the fractures, a mixed desmochondral callus was seen. The endoplasmic reticulum of the osteoblasts was markedly dilated, the mitochondria were swollen. The osteoid was reduced in quantity. A postmortem analysis of the collagen types I, II and III obtained from skin, cartilage and bone yielded chromatographically normal collagen constituents. An analysis of the amino acids of the collagen alpha-chains showed an increased hydroxylysine content. The radiological findings and the clinical course both indicated type III osteogenesis imperfecta: identical biochemical findings have been described only for type II. The morphological and biochemical findings described here may be a manifestation of a variable expressivity of type III osteogenesis imperfecta. On the other hand, heterogeneity of type II osteogenesis imperfecta cannot be ruled out.

[Antenatal forms of osteogenesis imperfecta. Classification trial]

A classification of the different types of osteogenesis imperfecta is proposed. There are 3 main groups: the lethal type, the severe type and the so-called regressive type, with a more favorable course. This classification was established to allow for a more precise definition of the prognosis at the time of birth, or even in utero when diagnosis is made by ultrasonography. It should also allow for better classification of the data obtained by the study of the molecular collagen. This project is different from Sillence's one by the exclusion of type II B lethal types, which are often compatible with survival. In view of the frequent occurrence of a dominant mutation in the type II A, the more generally accepted recessive transmission is discussed.

Osteogenesis imperfecta type III. Delineation of the phenotype with reference to genetic heterogeneity

The existence of a rare form of osteogenesis imperfecta, OI type III, has been postulated. This is characterized by autosomal recessive inheritance with neonatal manifestations of bone fragility or deformability. It is usually nonlethal. Studies of some 345 pedigrees of OI in the last 8 years confirm that patients falling into this group are rare. They should be distinguished as a special group within the group of OI subjects with a progressively deforming OI phenotype delineated in previous publications [Sillence et al, 1979a, b]. The OI type III phenotype does not necessarily equate with progressively deforming OI, and probably only a proportion of cases with severe deformity and normal sclerae have OI type III. On the other hand, distinction between these patients and those with a milder form of perinatally lethal OI type II might be difficult. Whereas the natural history of skeletal deformity and fractures in patients with OI type III has certain similarities, variable severity between families indicates that OI type III is likely to be genetically heterogeneous.

Urinary-free amino acids in osteogenesis imperfecta

Free urinary amino acids were analyzed in patients with osteogenesis imperfecta to determine whether there were any abnormalities that could be used to improve the diagnosis and classification of this syndrome. The results obtained from 15 patients, who had either the type 1, 2, or 3 form of osteogenesis imperfecta, were compared to the values obtained from 115 age-matched controls. Elevated free amino acid levels were not found in any patient with osteogenesis imperfecta.

Demineralization of dentin with EDTA in organic solvent: immunofluorescence of collagen in osteogenesis imperfecta and normal teeth

The immunofluorescence of dentin collagen(s) after demineralization with ethanolic trimethylammonium ethylenediaminetetra-acetic acid (EtOH-TMA-EDTA) was studied using normal deciduous teeth, and deciduous and permanent teeth from three patients with Osteogenesis imperfecta (OI). Sections of the demineralized teeth were immunostained with anti type I, III and IV collagen sera. Preservation of the antigenicity of the collagens after treatment with EtOH-TMA-EDTA was confirmed by staining of the soft tissue controls. Anti type I collagen sera stained the normal dentin matrix peritubularly only. In OI, a homogeneous fluorescence of the mantle dentin and the dentin zone surrounding the abnormal canal-like structures was observed. With anti type III collagen serum, the normal dentin matrix failed to stain. In OI, the staining pattern was a narrow halo surrounding the canal-like structures. Alteration in the collagen or the noncollagenous components of the dentin matrix may explain the staining reactions of the various collagens in OI.

Reduced strength of skin in osteogenesis imperfecta

The biochemical properties and ratio collagen type I/type III of skin biopsies from nine patients with osteogenesis imperfecta and nine age- and sex-matched controls were studied. Four of six patients with osteogenesis imperfecta Sillence type I had pronounced reductions in skin tensile strength, decreased ratios of collagen type I/type III, primarily accomplished by reduced amounts of collagen type I, moderate or no disability. The three patients with osteogenesis imperfecta Sillence type III had severe skeletal deformities, but normal skin tensile strength, and ratios of collagen type I/type III within the normal range. These observations may be explained as resulting from various structural defects in the type I collagen of patients with osteogenesis imperfecta.

Costovertebral anomalies in osteogenesis imperfecta

Study of 16 patients with Type III osteogenesis imperfecta showed marked elongation of the pedicles of the vertebrae in all cases, a deformity which was not seen in other types of the disease. Posterior rib angulation was also noted in Type III disease. These features have proved useful in suggesting the diagnosis of osteogenesis imperfecta even before long bones have fractured and in categorizing patients with osteogenesis imperfecta into the correct type for prognostic purposes.