Osteogenesis imperfecta in childhood: cardiac and renal manifestations

Investigation of oral health findings and genotype correlations in osteogenesis imperfecta

Osteogenesis imperfecta, a common genetic connective tissue disorder affecting bone with multisystemic implications, is caused by genomic alterations at various levels that disrupt the biosynthesis stages of collagen Type I. This study evaluated the intraoral and clinical findings of 43 OI cases in relation to genetic variants, aiming to contribute new insights into the roles of collagen and non-collagen genes in the oral-dental pathology of OI. Significant associations were found between OI variants and dental anomalies such as dentinogenesis imperfecta, enamel hypoplasia, taurodontism, and hypodontia. COL1A1/2-truncated variants were linked to atypical intercanine width, and midface hypoplasia correlated with reduced overjet and overbite. Bisphosphonate treatment, especially when initiated before age two, was associated with enamel hypoplasia. Oral hygiene habits, including brushing frequency and use of additional products, were linked to lower DMFT. In the OI group, significant associations were noted between Angle Class III malocclusion and reduced brushing frequency, as well as between deep palatal vault and increased DMFT. A correlation was also observed between maximum mouth opening and joint hypermobility. These findings, along with new dental observations related to non-collagen variants, shed light on the oral health challenges in OI patients. Our study underscores the importance of multidisciplinary collaboration between dentistry and medical genetics in understanding complex conditions like OI. The comprehensive analysis of oral and dental findings in OI cases is expected to inform future research and enhance clinical approaches to managing the dental challenges associated with this disorder.

Collagen formation, function and role in kidney disease

Highly abundant in mammals, collagens define the organization of tissues and participate in cell signalling. Most of the 28 vertebrate collagens, with the exception of collagens VI, VII, XXVI and XXVIII, can be categorized into five subgroups: fibrillar collagens, network-forming collagens, fibril-associated collagens with interrupted triple helices, membrane-associated collagens with interrupted triple helices and multiple triple-helix domains with interruptions. Collagen peptides are synthesized from the ribosome and enter the rough endoplasmic reticulum, where they undergo numerous post-translational modifications. The collagen chains form triple helices that can be secreted to form a diverse array of supramolecular structures in the extracellular matrix. Collagens are ubiquitously expressed and have been linked to a broad spectrum of disorders, including genetic disorders with kidney phenotypes. They also have an important role in kidney fibrosis and mass spectrometry-based proteomic studies have improved understanding of the composition of fibrosis in kidney disease. A wide range of therapeutics are in development for collagen and kidney disorders, including genetic approaches, chaperone therapies, protein degradation strategies and anti-fibrotic therapies. Improved understanding of collagens and their role in disease is needed to facilitate the development of more specific treatments for collagen and kidney disorders.

Echocardiographic abnormalities and joint hypermobility in Chinese patients with Osteogenesis imperfecta

BACKGROUND

Very little is known about the characteristics of echocardiographic abnormalities and joint hypermobility in Chinese patients with osteogenesis imperfecta (OI). The aim of our study was to investigate the characteristics, prevalence and correlation of echocardiographic abnormalities and joint hypermobility in Chinese patients with OI.

METHODS

A cross-sectional comparative study was conducted in pediatric and adult OI patients who were matched in age and sex with healthy controls. Transthoracic echocardiography was performed in all patients and controls, and parameters were indexed for body surface area (BSA). The Beighton score was used to evaluate the degree of joint hypermobility.

RESULTS

A total of 48 patients with OI (25 juveniles and 23 adults) and 129 age- and sex-matched healthy controls (79 juveniles and 50 adults) were studied. Four genes (COL1A1, COL1A2, IFITM5, and WNT1) and 39 different mutation loci were identified in our study. Mild valvular regurgitation was the most common cardiac abnormality: mild mitral and tricuspid regurgitation was found in 12% and 36% of pediatric OI patients, respectively; among 23 OI adults, 13% and 17% of patients had mild mitral and tricuspid regurgitation, respectively, and 4% had mild aortic regurgitation. In multiple regression analysis, OI was the key predictor of left atrium diameter (LAD) (β=-3.670, P < 0.001) and fractional shortening (FS) (β = 3.005, P = 0.037) in juveniles, whereas for adults, OI was a significant predictor of LAD (β=-3.621, P < 0.001) and left ventricular mass (LVM) (β = 58.928, P < 0.001). The percentages of generalized joint hypermobility in OI juveniles and adults were 56% and 20%, respectively. Additionally, only in the OI juvenile group did the results of the Mann‒Whitney U test show that the degree of joint hypermobility was significantly different between the echocardiographic normal and abnormal groups (P = 0.004).

CONCLUSIONS

Mild valvular regurgitation was the most common cardiac abnormality in both OI juveniles and adults. Compared with OI adults, OI juveniles had more prevalent and wider joint hypermobility. Echocardiographic abnormalities may imply that the impairment of type I collagen is more serious in OI. Baseline echocardiography should be performed in OI patients as early as possible.

Is Osteogenesis Imperfecta Associated with Cardiovascular Abnormalities? A Systematic Review of the Literature

Osteogenesis imperfecta (OI) is a rare genetic disorder caused by abnormal collagen type I production. While OI is primarily characterized by bone fragility and deformities, patients also have extraskeletal manifestations, including an increased risk of cardiovascular disease. This review provides a comprehensive overview of the literature on cardiovascular diseases in OI patients in order to raise awareness of this understudied clinical aspect of OI and support clinical guidelines. In accordance with the PRISMA guidelines, a systematic literature search in PubMed, Embase, Web of Science and Scopus was conducted that included articles from the inception of these databases to April 2023. Valvular disease, heart failure, atrial fibrillation, and hypertension appear to be more prevalent in OI than in control individuals. Moreover, a larger aortic root was observed in OI compared to controls. Various cardiovascular diseases appear to be more prevalent in OI than in controls. These cardiovascular abnormalities are observed in all types of OI and at all ages, including young children. As there are insufficient longitudinal studies, it is unknown whether these abnormalities are progressive in nature in OI patients. Based on these findings, we would recommend referring individuals with OI to a cardiologist with a low-threshold.

Efficacy of Bisphosphonate for Urolithiasis Complicated by Osteogenesis Imperfecta

A 44-year-old man with osteogenesis imperfecta presented with left renal colic. Non-contrast computed tomography revealed a stone (10×9 mm) in the left upper ureter. Ureteroscopic lithotripsy was performed twice and stone-free status was achieved. An analysis of the stone revealed a mixed composition including calcium oxalate and calcium phosphate. Postoperatively, we administered bisphosphonates to prevent recurrence of urolithiasis, as 24-hour urine collection revealed marked hypercalciuria. Eighteen months after surgery, the urinary calcium levels had normalized, and there was no recurrence of urolithiasis. Osteogenesis imperfecta can be complicated by urolithiasis, but bisphosphonates may be useful in preventing recurrence of this disease.

Novel splice site variant of TMEM38B in osteogenesis imperfecta type XIV

Osteogenesis imperfecta (OI) is a rare genetic disorder characterized by brittle bones. In this case report, we describe a patient who suffered from OI type XIV with a novel splice site variant in the TMEM38B gene. Further research is needed to better understand the relationship between the phenotype of OI type XIV and this variant.

A single-centre study of genetic mutations, audiology, echocardiogram and pulmonary function in Saudi children with osteogenesis imperfecta

OBJECTIVES

Osteogenesis imperfecta (OI) is a heterogeneous group of inherited connective tissue disorders, characterised by skeletal fragility. Patients with OI may also exhibit extra-skeletal features like blue or grey scleral colour, fragile skin, easy bruising, joint laxity, short stature, deafness, cardiac valve abnormalities and abnormal pulmonary function. The objective of this study is to describe genetic mutations, prevalence of hearing issues, cardiac complications and impaired pulmonary function in children with OI.

METHODS

This is a cross-sectional study of 23 Saudi children aged 6 months to 18 years who were diagnosed with OI. The revised Sillence classification (2,105) was used to classify the OI type. Whole exome sequencing was performed for genetic mutations. The hearing was assessed by either pure-tone audiometry and/or otoacoustic emission testing. Cardiac defects were screened by echocardiograms. Spirometry was performed to assess pulmonary function. Data were analysed with descriptive statistics.

RESULTS

Based on the Sillence classification, 16 patients had OI type III, 6 had type IV and 1 had type I. Of the18 patients who had genetic sequencing, 66.6% had autosomal dominant and 33.3% had autosomal recessive mutations. Among children who had screening, hearing loss was diagnosed in 53% (9/17), congenital cardiac malformations in 26% (5/19) and restrictive lung disease in 70% (7/10).

CONCLUSIONS

We found significant extra-skeletal features and a high yield of genetic mutations associated with OI. We suggest further studies to develop a screening protocol for extra-skeletal features in children with OI.

Cardiovascular abnormalities and its correlation with genotypes of children with osteogenesis imperfecta

BACKGROUND AND OBJECTIVES

Osteogenesis imperfecta (OI) is a rare disorder of abnormal production or modification of type I collagen, which is caused by mutations in COL1A1, COL1A2 or other genes. We investigate the cardiac abnormalities and its correlation with pathogenic mutations in OI children.

METHODS

A cross-sectional comparative study was completed in a relatively large sample of OI children, who were matched in body surface area (BSA) with healthy controls. All echocardiography was performed by experienced cardiologists using Vivid 7 equipment (GE Medical Systems, Horton, Norway). The resting standard 12-lead electrocardiogram (ECG) were obtained in OI patients by FX-8600 machine. Skeletal phenotypes of OI patients were evaluated, including information of bone fractures, deformities, motility, and bone mineral density (BMD). Pathogenic mutations of OI were detected by a next-generation sequencing panel and confirmed by Sanger sequencing.

RESULTS

A total of 69 OI children and 42 healthy children matched in BSA were enrolled. Abnormalities of echocardiography were found in 6 OI children, including enlarged left atrium (n=5), increased internal diameter of the left ventricle (n=1), who all carried the COL1A1 mutation. Mild regurgitation of mitral or tricuspid valves was observed in 26 OI patients. Abnormal ECG manifestations were found in 8 OI children, including deep Q wave, T wave change, premature ventricular complexes, short P-R interval, incomplete bundle branch block and high voltage of left ventricular. Compared with healthy controls, OI children had significant larger values in the main pulmonary artery (1.84 vs 1.60 cm, P < 0.01), left atrial diameter (2.58 vs 2.11 cm, P < 0.001), left ventricular internal dimension at end-diastolic (LVEDd) (3.85 vs 3.50 cm, P < 0.05) and lower left ventricular ejection fraction (LVEF) (68.40% vs 71.74%, P < 0.01). Moreover, OI patients with COL1A1 mutation tended to have greater main pulmonary artery, larger diameters of left atrial and LVEDd, and lower LVEF than healthy controls. COL1A1 mutation was correlated to dilated MPA (β = 1.557, P < 0.01), LAD (β = 3.915, P < 0.001), and LVEDd (β = 2.714, P < 0.01), and decreased LVEF (β = -3.249, P < 0.01).

CONCLUSIONS

Cardiovascular alterations were identified in OI children, including increased dimensions of the main pulmonary artery and left chamber, and low LVEF. The cardiovascular abnormalities seemed to be correlated to COL1A1 mutation and defects of type I collagen, which expanded our understandings of the cardiac phenotypes of OI children.

Mitral Valve Prolapse and Its Motley Crew-Syndromic Prevalence, Pathophysiology, and Progression of a Common Heart Condition

Mitral valve prolapse (MVP) is a commonly occurring heart condition defined by enlargement and superior displacement of the mitral valve leaflet(s) during systole. Although commonly seen as a standalone disorder, MVP has also been described in case reports and small studies of patients with various genetic syndromes. In this review, we analyzed the prevalence of MVP within syndromes where an association to MVP has previously been reported. We further discussed the shared biological pathways that cause MVP in these syndromes, as well as how MVP in turn causes a diverse array of cardiac and noncardiac complications. We found 105 studies that identified patients with mitral valve anomalies within 18 different genetic, developmental, and connective tissue diseases. We show that some disorders previously believed to have an increased prevalence of MVP, including osteogenesis imperfecta, fragile X syndrome, Down syndrome, and Pseudoxanthoma elasticum, have few to no studies that use up-to-date diagnostic criteria for the disease and therefore may be overestimating the prevalence of MVP within the syndrome. Additionally, we highlight that in contrast to early studies describing MVP as a benign entity, the clinical course experienced by patients can be heterogeneous and may cause significant cardiovascular morbidity and mortality. Currently only surgical correction of MVP is curative, but it is reserved for severe cases in which irreversible complications of MVP may already be established; therefore, a review of clinical guidelines to allow for earlier surgical intervention may be warranted to lower cardiovascular risk in patients with MVP.

Extracellular Matrix in Vascular Disease, Part 2/4: JACC Focus Seminar

Medium-sized and large arteries consist of 3 layers: the tunica intima, tunica media, and tunica adventitia. The tunica media accounts for the bulk of the vessel wall and is the chief determinant of mechanical compliance. It is primarily composed of circumferentially arranged layers of vascular smooth muscle cells that are separated by concentrically arranged elastic lamellae; a form of extracellular matrix (ECM). The tunica media is separated from the tunica intima and tunica adventitia, the innermost and outermost layers, respectively, by the internal and external elastic laminae. This second part of a 4-part JACC Focus Seminar discusses the contributions of the ECM to vascular homeostasis and pathology. Advances in genetics and proteomics approaches have fostered significant progress in our understanding of vascular ECM. This review highlights the important role of the ECM in vascular disease and the prospect of translating these discoveries into clinical disease biomarkers and potential future therapies.

Echocardiographic study in children with osteogenesis imperfecta

BACKGROUND

Osteogenesis imperfecta is a collagen type I bone disorder. Recently, extra-skeletal manifestations have been described, including many cardiovascular alterations. This study aims to report echocardiogram study in children with osteogenesis imperfecta compared to a control group.

METHODS

A cross-sectional comparative study took place in the Reference Center for Treatment of Osteogenesis Imperfecta in Southern Brazil. Fifty-four patients with osteogenesis imperfecta were paired with 54 controls, based on body surface area, and echocardiogram findings were compared.

RESULTS

All cases were asymptomatic for cardiac manifestations. The case group presented significant larger values in aortic diameter, left atrium diameter, left ventricule end-diastolic diameter, left ventricule end-systolic diameter, and right ventricle diameter compared with the control group. The analysis considering the severity of osteogenesis imperfecta shows that in mild osteogenesis imperfecta, the aortic diameter (p < 0.001), left atrium diameter (p = 0.002), left ventricule end-diastolic diameter (p = 0.001), left ventricule end-systolic diameter (p = 0.026), and right ventricle diameter (p < 0.001) were significantly larger than in the control group. Patients with moderate/severe osteogenesis imperfecta had similar results, with aortic diameter (p < 0.001), left atrium diameter (p < 0.001), left ventricule end-diastolic diameter (p = 0.013), and left ventricule end-systolic diameter (0.004) statistically larger than controls. Twenty-six (48.1%) of the cases had physiological tricuspid regurgitation and in controls this finding was observed in eight (14.8%) (p < 0.001).

CONCLUSION

Children with osteogenesis imperfecta presented cardiac function within the normal pattern, but dimensions of left ventricular dimensions were increased compared to the ones of the controls.

A Unique Association of Osteogenesis Imperfecta with Bilateral Renal Osteodystrophy and Gastroenteritis in a Three-year-old Boy

We describe a three-year-old male child who presented to the pediatrics out-patient department with a history of decrease in appetite, generalized weakness, on and off loose motions for one year, inability to walk and sit for eight months with a loss of neck holding for 14 days. On examination, the patient had a classic frog-shaped leg posture. X-rays of chest, skull, pelvis and long bones were performed which showed osteopenic bones, frontal bossing and multiple microfractures, which were classic for osteogenesis Imperfecta but the child did not have other salient features such as blue sclera, otosclerosis, and respiratory difficulty. The patient also had urinary complaints due to which ultrasound of kidney ureters and bladder (KUB) was performed, which showed bilateral renal calculi and grade 2 renal parenchymal changes. This case report illustrates the evaluation of the child with osteogenesis imperfecta, as well as the unique association of renal osteodystrophy and gastroenteritis with it.

Aortic aneurysm/dissection and osteogenesis imperfecta: Four new families and review of the literature

Osteogenesis imperfecta (OI) is the commonest form of heritable bone fragility. It is mainly characterized by fractures, hearing loss and dentinogenesis imperfecta. OI patients are at increased risk of cardiovascular disease of variable severity. Aortic aneurysm/dissection is one of the rarer but potentially serious cardiovascular complications of OI. So far, only six patients with aortic dissection and OI have been reported. As such, present OI diagnostic guidelines do not recommend systematic screening of patients for aortopathy. Here, we report on the clinical and molecular characteristics of three new OI patients and one additional patient with a first degree relative who presented with aortic dissection and/or aneurysm surgery. This observation further opens up the discussion on the need for and extent of cardiovascular screening in adult patients with OI.

Osteogenesis imperfecta

Skeletal deformity and bone fragility are the hallmarks of the brittle bone dysplasia osteogenesis imperfecta. The diagnosis of osteogenesis imperfecta usually depends on family history and clinical presentation characterized by a fracture (or fractures) during the prenatal period, at birth or in early childhood; genetic tests can confirm diagnosis. Osteogenesis imperfecta is caused by dominant autosomal mutations in the type I collagen coding genes (COL1A1 and COL1A2) in about 85% of individuals, affecting collagen quantity or structure. In the past decade, (mostly) recessive, dominant and X-linked defects in a wide variety of genes encoding proteins involved in type I collagen synthesis, processing, secretion and post-translational modification, as well as in proteins that regulate the differentiation and activity of bone-forming cells have been shown to cause osteogenesis imperfecta. The large number of causative genes has complicated the classic classification of the disease, and although a new genetic classification system is widely used, it is still debated. Phenotypic manifestations in many organs, in addition to bone, are reported, such as abnormalities in the cardiovascular and pulmonary systems, skin fragility, muscle weakness, hearing loss and dentinogenesis imperfecta. Management involves surgical and medical treatment of skeletal abnormalities, and treatment of other complications. More innovative approaches based on gene and cell therapy, and signalling pathway alterations, are under investigation.

Minimally invasive percutaneous nephrolithotomy guided by ultrasonography to treat upper urinary tract calculi complicated with severe spinal deformity

Objective:

To report our experience of minimally invasive percutaneous nephrolithotomy(MPCNL) in managing upper urinary tract calculi complicated with severe spinal deformity.

Materials and Methods:

Between August 2001 to December 2012, 16 upper urinary calculi in 13 patients with severe spinal deformity were treated by MPCNL. Preoperative investigation of the respiratory function, evaluation of anatomy by intravenous urography (IVU) and CT scan, and preoperative kidney ultrasonagraphy with simulation of the percutaneous puncture were performed in all patients. The percutaneous puncture was guided by ultrasonography.

Results:

A total of 19 MPCNL procedures were performed in 16 kidneys, with an average 1.2 procedures in each kidney. Three kidneys needed two sessions of MPCNL, and 2 kidneys needed combined treatment with retrograde flexible ureterscopic lithotripsy. All procedures were successfully completed with no major complications during or after surgery. The mean (range) operative duration was 67 (20-150) min and the mean postoperative haemoglobin drop was 1.0 (0.2-3.1) g/dL. Complete stone-free status was achieved in 14 kidneys. At a mean follow-up of 48(3-86) months, recurrence of small lower calyx stone was detected in one patient. Recurrent UTI was documented by urine culture in two patients and managed with sensitive antibiotics.

Conclusion:

PCNL for patients with severe spinal deformities is challenging. Ultrasonography-assisted puncture can allow safe and successfully establishment of PCN tract through a narrow safety margin of puncture and avoid the injury to the adjacent organs. However, the operation should be performed in tertiary centers with significant expertise in managing complex urolithiasis.

Echocardiographic Evidence of Early Diastolic Dysfunction in Asymptomatic Children with Osteogenesis Imperfecta

OBJECTIVES

Structural and functional cardiovascular abnormalities have been reported in adults with osteogenesis imperfecta (OI); however, there is a lack of paediatric literature on this topic. This study aimed to investigate cardiovascular abnormalities in children with OI in comparison to a control group.

METHODS

This case-control study was conducted at the Sultan Qaboos University Hospital in Muscat, Oman, between May 2013 and August 2014. Data from eight patients with OI and 24 healthy controls were compared using conventional and tissue Doppler echocardiography (TDE).

RESULTS

The OI group had significantly lower peak early mitral valve flow velocity (P = 0.027), peak a-wave reversal in the pulmonary vein (P = 0.030) and peak early diastolic velocity of the mitral valve and upper septum (P = 0.001 each). The peak late diastolic velocities of the mitral valve (P = 0.002) and the upper septum (P = 0.037) were significantly higher in the OI group; however, the peak early/late diastolic velocity ratios of the mitral valve (P = 0.002) and upper septum (P = 0.001) were significantly lower. Left ventricular dimensions and aortic and pulmonary artery diameters were larger in the OI group when indexed for body surface area. Both groups had normal systolic cardiac function.

CONCLUSION

Children with OI had normal systolic cardiac function. However, changes in myocardial tissue Doppler velocities were suggestive of early diastolic cardiac dysfunction. They also had increased left ventricular dimensions and greater vessel diameters. These findings indicate the need for early and detailed structural and functional echocardiographic assessment and follow-up of young patients with OI.

Ventricular septal defect closure in a child with osteogenesis imperfecta: risk factors and management

Cardiac surgery in patients with osteogenesis imperfecta is challenging as the friability of the tissues can be hazardous before, during, and after the operation. A multidisciplinary approach with a planned strategy is essential for the successful management of these patients. We present a 6-year old child with osteogenesis imperfecta, who underwent ventricular septal defect closure without any complication.

Radiographic features of osteogenesis imperfecta

Background

Osteogenesis imperfecta (OI), commonly called “brittle bone disease”, is a genetic disorder characterised by increased bone fragility and decreased bone density due to quantitative and/or qualitative abnormalities of type I collagen. Different types of OI exist, from mild to severe; they may lead to death, multiple bone fractures, skeletal deformity and short stature.

Methods

Severe cases are usually diagnosed before birth and may incite the parents to choose therapeutic abortion, whereas milder cases are much more difficult to diagnose and may be sometimes confused with non-accidental injury (NAI) (“child abuse”) in young children. Whatever the degree of severity, conventional radiography still remains the mainstay in diagnosing OI.

Results

The prognosis of this disorder has changed in the last few years thanks to biphosphonate therapy.

Conclusion

The aim of this pictorial review is to illustrate the radiographic manifestations of OI, including in children receiving biphosphonates, and to outline specific patterns that help differentiate OI from NAI when necessary.

Key Points

• The main radiographic features of OI are osteopenia, bone fractures and bone deformities.

• Some radiographic features depend on the type of OI or may be encountered with biphosphonates.

Right ventricular and pulmonary arterial dimensions in adults with osteogenesis imperfecta

We examined right ventricular (RV) and ascending pulmonary artery (PA1) dimensions in adults with osteogenesis imperfecta (OI). The survey included 99 adults with OI divided in 3 clinical types (I, III, and IV) and 52 controls. RV and PA1 dimensions were measured by echocardiography and indexed for body surface area. Scoliosis was registered, and spirometry was performed in 75 patients with OI. All RV dimensions indexed by body surface area were significantly larger in the OI group compared to controls (RV basal dimension 1.9 ± 0.5 vs 1.7 ± 0.3 cm/m(2), p <0.05; RV midcavity dimension 1.7 ± 0.5 vs 1.5 ± 0.3 cm/m(2), p <0.05; RV longitudinal dimension 4.3 ± 1.1 vs 4.0 ± 0.9 cm/m(2), p <0.05). RV outflow tract (RVOT) proximal diameter (1.8 ± 0.4 vs 1.5 ± 0.2 cm/m(2), p <0.05), RVOT distal diameter (1.2 ± 0.2 vs 1.0 ± 0.1 cm/m(2), p <0.05), and PA1 (1.2 ± 0.3 vs 1.0 ± 0.2 cm/m(2), p <0.05) were also significantly larger in the OI group. Furthermore, all RV dimensions and PA1 were significantly larger in patients with OI type III compared to patients with OI types I and IV and controls. There were no differences in RV, RVOT, or PA1 dimensions between patients presenting a restrictive ventilatory pattern (n = 11) and patients a normal ventilatory pattern. Scoliosis was registered in 42 patients. Patients with OI type III had greater RV and PA1 dimensions compared to controls and patients with OI types I and IV. Impaired ventilatory patterns and scoliosis did not have any impact on RV dimensions in these patients. In conclusion, patients with OI had increased RV and PA1 dimensions compared to the control group.

Cardiopulmonary dysfunction in the Osteogenesis imperfecta mouse model Aga2 and human patients are caused by bone-independent mechanisms

Osteogenesis imperfecta (OI) is an inherited connective tissue disorder with skeletal dysplasia of varying severity, predominantly caused by mutations in the collagen I genes (COL1A1/COL1A2). Extraskeletal findings such as cardiac and pulmonary complications are generally considered to be significant secondary features. Aga2, a murine model for human OI, was systemically analyzed in the German Mouse Clinic by means of in vivo and in vitro examinations of the cardiopulmonary system, to identify novel mechanisms accounting for perinatal lethality. Pulmonary and, especially, cardiac fibroblast of perinatal lethal Aga2/+ animals display a strong down-regulation of Col1a1 transcripts in vivo and in vitro, resulting in a loss of extracellular matrix integrity. In addition, dysregulated gene expression of Nppa, different types of collagen and Agt in heart and lung tissue support a bone-independent vicious cycle of heart dysfunction, including hypertrophy, loss of myocardial matrix integrity, pulmonary hypertension, pneumonia and hypoxia leading to death in Aga2. These murine findings are corroborated by a pediatric OI cohort study, displaying significant progressive decline in pulmonary function and restrictive pulmonary disease independent of scoliosis. Most participants show mild cardiac valvular regurgitation, independent of pulmonary and skeletal findings. Data obtained from human OI patients and the mouse model Aga2 provide novel evidence for primary effects of type I collagen mutations on the heart and lung. The findings will have potential benefits of anticipatory clinical exams and early intervention in OI patients.

Cardiovascular abnormalities in adults with osteogenesis imperfecta

BACKGROUND

The aim of this study was to investigate cardiac abnormalities in adults with osteogenesis imperfecta (OI).

METHODS

The clinical and echocardiographic survey included 99 adults with OI divided into 3 clinical types-I, III, and IV-and 52 controls. Left ventricular end-diastolic dimensions (LVIDds), mass, and 4 aortic diameters were measured by standard echocardiography and indexed for body surface area.

RESULTS

Hypertension was registered in 37 individuals (37.4%). The OI group had significantly lower body surface area than the control individuals, 1.7 ± 0.3 versus 1.9 ± 0.2 m(2) (P < .05). The LVIDd and LV mass were significantly larger in the OI group when compared with the controls, 2.98 ± .64 versus 2.59 ± .26 cm/m(2) (P < .05) and 97.3 ± 30.1 versus 73.3 ± 18.0 g/m(2) (P < .05), respectively. Type III OI showed significantly enlarged LVIDd as compared with types I and IV OI, 4.33 ± 1.10 versus 2.83 ± .33 (P < .05) versus 2.85 ± .37 cm/m(2) (P < .05), respectively. All aortic diameters were significantly larger in the OI group than in the control group, as they were in type III compared with types I and IV; 10.1% mild aortic regurgitation (AR), 10.1% moderate AR, and 7.1% moderate mitral regurgitation were registered in the OI group.

CONCLUSIONS

Increased LVIDd, LV mass, mitral regurgitation, and AR were found in adult patients with OI compared with the control group. The changes in LV and dilatation of aorta seemed to be more pronounced in patients with type III compared with types I and IV OI.

Generalized connective tissue disease in Crtap-/- mouse

Mutations in CRTAP (coding for cartilage-associated protein), LEPRE1 (coding for prolyl 3-hydroxylase 1 [P3H1]) or PPIB (coding for Cyclophilin B [CYPB]) cause recessive forms of osteogenesis imperfecta and loss or decrease of type I collagen prolyl 3-hydroxylation. A comprehensive analysis of the phenotype of the Crtap-/- mice revealed multiple abnormalities of connective tissue, including in the lungs, kidneys, and skin, consistent with systemic dysregulation of collagen homeostasis within the extracellular matrix. Both Crtap-/- lung and kidney glomeruli showed increased cellular proliferation. Histologically, the lungs showed increased alveolar spacing, while the kidneys showed evidence of segmental glomerulosclerosis, with abnormal collagen deposition. The Crtap-/- skin had decreased mechanical integrity. In addition to the expected loss of proline 986 3-hydroxylation in alpha1(I) and alpha1(II) chains, there was also loss of 3Hyp at proline 986 in alpha2(V) chains. In contrast, at two of the known 3Hyp sites in alpha1(IV) chains from Crtap-/- kidneys there were normal levels of 3-hydroxylation. On a cellular level, loss of CRTAP in human OI fibroblasts led to a secondary loss of P3H1, and vice versa. These data suggest that both CRTAP and P3H1 are required to maintain a stable complex that 3-hydroxylates canonical proline sites within clade A (types I, II, and V) collagen chains. Loss of this activity leads to a multi-systemic connective tissue disease that affects bone, cartilage, lung, kidney, and skin.

Extraperitoneal laparoscopy-assisted percutaneous nephrolithotomy in a patient with osteogenesis imperfecta

Osteogenesis imperfecta (OI) patients represent a challenge to all physicians, as they do for anesthetists and urologists, when they develop symptomatic stones in the urinary tract. We recently treated an OI patient with renal pelvic stone by extraperitoneal laparoscopy-assisted percutaneous nephrolithotomy (PCNL). To our knowledge, this combined treatment modality has not been reported previously in OI. An 18-year-old paraplegic girl with OI presented to our urology department because of right-sided flank pain. She pointed out that she had right kidney stone for the previous 2 years, and because of risks of general anesthesia and surgical procedures, surveillance was recommended. Intravenous pyelography was performed and an 11.9-mm stone at the pelvis of the right kidney and grade 1-2 hydronephrosis at the same side with normal kidney functions and severe left-sided scoliosis were detected. After explanation of risks of the treatment modality and general anesthesia to the patient, extraperitoneal laparoscopy-assisted PCNL was performed. No complications occurred due to general anesthesia or surgical procedure. The operation time was 95 min and no blood transfusion was required. The nephrostomy tube and retroperitoneal drain were removed 2 and 3 days after the procedure, respectively. The patient was doing well at a follow-up of 6 months. Extraperitoneal laparoscopy-assisted PCNL approach may decrease the risk of surgery as an alternative treatment modality for OI patients. Such cases should be operated on at centers with significant experience in the field of endourology, where all the equipment and specialized personnel are readily available.

Null mutations in LEPRE1 and CRTAP cause severe recessive osteogenesis imperfecta

Classical osteogenesis imperfecta (OI) is a dominant genetic disorder of connective tissue caused by mutations in either of the two genes encoding type I collagen, COL1A1 and COL1A2. Recent investigations, however, have generated a new paradigm for OI incorporating many of the prototypical features that distinguish dominant and recessive conditions, within a type I collagen framework. We and others have shown that the long-sought cause of the recessive form of OI, first postulated in the Sillence classification, lies in defects in the genes encoding cartilage-associated protein (CRTAP) or prolyl 3-hydroxylase 1 (P3H1/LEPRE1). Together with cyclophilin B (PPIB), CRTAP and P3H1 comprise the collagen prolyl 3-hydroxylation complex, which catalyzes a specific posttranslational modification of types I, II, and V collagen, and may act as a general chaperone. Patients with mutations in CRTAP or LEPRE1 have a lethal to severe osteochondrodystrophy that overlaps with Sillence types II and III OI but has distinctive features. Infants with recessive OI have white sclerae, undertubulation of the long bones, gracile ribs without beading, and a small to normal head circumference. Those who survive to childhood or the teen years have severe growth deficiency and extreme bone fragility. Most causative mutations result in null alleles, with the absence or severe reduction of gene transcripts and proteins. As expected, 3-hydroxylation of the Pro986 residue is absent or severly reduced, but bone severity and survival length do not correlate with the extent of residual hydroxylation. Surprisingly, the collagen produced by cells with an absence of Pro986 hydroxylation has helical overmodification by lysyl hydroxylase and prolyl 4-hydroxylase, indicating that the folding of the collagen helix has been substantially delayed.

Transplantation of human fetal mesenchymal stem cells improves glomerulopathy in a collagen type I alpha 2-deficient mouse

Fetal mesenchymal stem cell (fetal MSC) therapy has potential to treat genetic diseases with early onset, including those affecting the kidney and urinary tract. A collagen type I alpha 2-deficient mouse has a deletion in the alpha2 chain of the procollagen type I gene, resulting in the synthesis of abnormal alpha1(I)(3) homotrimers, which replace normal alpha 1(I)2 alpha 2(I)1 heterotrimers and a glomerulopathy. We first confirmed that col1 alpha 2-deficient homozygous mice show abnormal collagen deposition in the glomeruli, which increases in frequency and severity with postnatal age. Intrauterine transplantation of human MSCs from first trimester fetal blood led postnatally to a reduction of abnormal homotrimeric collagen type I deposition in the glomeruli of 4-12 week-old col1 alpha 2-deficient mice. Using bioluminescence imaging, in situ hybridization and immunohistochemistry in transplanted col1 alpha 2-deficient mice, we showed that the damaged kidneys preferentially recruited donor cells in glomeruli, around mesangial cells. Real-time RT-PCR demonstrated that this effect was seen at an engraftment level of 1% of total cells in the kidney, albeit higher in glomeruli. We conclude that intrauterine transplantation of human fetal MSCs improves renal glomerulopathy in a collagen type I-deficient mouse model. These data support the feasibility of prenatal treatment for hereditary renal diseases.

Alpha 2(I) collagen deficient oim mice have altered biomechanical integrity, collagen content, and collagen crosslinking of their thoracic aorta

Collagen and elastin are the primary determinants of vascular integrity, with elastin hypothesized to be the major contributor to aortic compliance and type I collagen the major contributor to aortic strength and stiffness. Type I collagen is normally heterotrimeric composed of two alpha1(I) and one alpha2(I) collagen chains, alpha1(I)(2)alpha2(I). Recent investigations have reported that patients with recessively inherited forms of Ehlers Danlos syndrome that fail to synthesize proalpha2(I) chains have increased risks of cardiovascular complications. To assess the role of alpha2(I) collagen in aortic integrity, we used the osteogenesis imperfecta model (oim) mouse. Oim mice, homozygous for a COL1A2 mutation, synthesize only homotrimeric type I collagen, alpha1(I)3. We evaluated thoracic aortas from 3-month-old oim, heterozygote, and wildtype mice biomechanically for circumferential breaking strength (Fmax) and stiffness (IEM), histologically for morphological differences, and biochemically for collagen content and crosslinking. Circumferential biomechanics of oim and heterozygote descending thoracic aortas demonstrated the anticipated reduced Fmax and IEM relative to wildtype mice. Histological analyses of oim descending aortas demonstrated reduced collagen staining relative to wildtype aortas suggesting decreased collagen content, which hydroxyproline analyses of ascending and descending oim aortas confirmed. These findings suggest the reduced oim thoracic aortic integrity correlates with the absence of the alpha2(I)collagen chains and in part with reduced collagen content. However, oim ascending aortas also demonstrated a significant increase in pyridinoline crosslinks/collagen molecule as compared to wildtype ascending aortas. The role of increased collagen crosslinks is uncertain; increased crosslinking may represent a compensatory mechanism for the decreased integrity.

Novel collagen glomerulopathy in a homotrimeric type I collagen mouse (oim)

BACKGROUND

Oim/oim mice [osteogenesis imperfecta model; homozygous null for the proalpha2(I) collagen gene] synthesize exclusively the homotrimeric type I collagen isotype, alpha1(I)3, and are unable to synthesize the normal heterotrimeric type I collagen isotype, alpha1(I)2alpha2(I). Previous studies of the oim/oim mouse have focused on the musculoskeletal system, with no systematic evaluation of other organ systems.

METHODS

Multiple tissues from oim/oim, oim/+ (heterozygous) and +/+ (wild-type) mice were examined for gross and histological abnormalities. Tissues were stained with (1) hematoxylin and eosin (to assess lesion formation), (2) picrosirius red (collagen content), and (3) periodic acid methenamine silver (basement membrane). Kidneys were further evaluated ultrastructurally by electron microscopy and immunohistochemically with anti-alpha1(I) and anti-alpha1(III) collagen antibodies.

RESULTS

Histological analyses revealed accumulations of picrosirius red-positive material, consistent with collagen, in glomeruli of 28/29 oim/oim mice, with no evidence of mesangial cell proliferation. Only the most severely affected animals had evidence of increased capillary basement membrane thickening or mild inflammation around the affected glomeruli. Electron microscopy confirmed the presence of fibrillar collagen. Immunohistochemistry with anti-alpha1(I) collagen antibodies confirmed accumulation of type I collagen in the oim/oim glomeruli. The +/+ and oim/+ kidneys had normal mesangium with no evidence of infiltration of collagenous material.

CONCLUSIONS

This study demonstrates the first evidence, to our knowledge, of abnormal glomerular collagen deposition associated with a type I collagen defect. Further in vivo and in vitro studies are necessary to elucidate the mechanistic, functional, and pathological significance of the oim/oim collagen glomerulopathy.

Aspects of the history of osteogenesis imperfecta (Vrolik's syndrome)

Osteogenesis imperfecta (OI) or Vrolik's syndrome is a heterogeneous group of inherited conditions arising from a variety of biochemical and morphological collagen defects. It was Willem Vrolik, Professor of Anatomy, Pathological Anatomy and Zoology at the Athenaeum Illustre (University of Amsterdam), who described in his Handbook of Pathological Anatomy (1842-1844) and Tabulae ad illustrandam embryogenesin hominis et mammalium, naturalem tam abnormem (1844-1849) a newborn infant with numerous fractures and hydrocephalus. In the Tabulae, having both Latin and Dutch texts, in the Latin text Vrolik used in the heading of Plate 91 the term Osteogenesis imperfecta (in Dutch: gebrekkige beenwording). Vrolik also mentioned that the infant lived three days and that both the parents were suffering from lues universalis at the time of birth. On our reexamination, the whole skeleton appeared poorly mineralised. The fairly large skull exhibited a broad and high forehead, large fontanels, frontal and temporal bossing, shallow orbits, and a protruding occiput. The calvaria consisted of many Wormian bones. The tubular bones, although of normal length and only slightly curved, were very thin, as were the ribs. All the skeletal structures showed one or more fractures and many fractures showed callus formation. In 1998 we re-diagnosed the condition of the specimen as osteogenesis imperfecta type II. Willem Vrolik was one of the first to realize that many skeletal dysplasias were not the result of a postnatal acquired disease, such as "rickets" or "osteomalacia" as many of his contemporaries believed. He thought that it might be due to insufficient intrinsic "generative energy." He substantiated this by stating that in this specimen a primary impairment of ossification is present and not a secondary degeneration. The descriptions given by Willem Vrolik in some of the specimens generated the term Osteogenesis imperfecta and the eponym Vrolik's syndrome for this genetic disorder characterized by increased fragility.

The role of type I collagen in aortic wall strength with a homotrimeric

PURPOSE

Elastin and collagen (types I and III) are the primary load-bearing elements in aortic tissue. Deficiencies and derangements in elastin and type III collagen have been associated with the development of aneurysmal disease. However, the role of type I collagen is less well defined. The purpose of this study was to define the role of type I collagen in maintaining biomechanical integrity in the thoracic aorta, with a mouse model that produces homotrimeric type I collagen [alpha1(I)]3, rather than the normally present heterotrimeric [alpha1(I)]2 alpha2(I) type I collagen isotype.

METHODS

Ascending and descending thoracic aortas from homozygous (oim/oim ), heterozygous (oim /+), and wildtype (+/+) mice were harvested. Circumferential and longitudinal load-extension curves were used as a means of determining maximum breaking strength (Fmax) and incremental elastic modulus (IEM). Histologic analyses and hydroxyproline assays were performed as a means of determining collagen organization and content.

RESULTS

Circumferentially, the ascending and descending aortas of oim /oim mice demonstrated significantly reduced Fmax, with an Fmax of only 60% and 23%, respectively, of wildtype mice aortas. Oim/oim descending aortas demonstrated significantly greater compliance (decreased IEM), and the ascending aortas also exhibited a trend toward increased compliance. Reduced breaking strength was also demonstrated with longitudinal extension of the descending aorta.

CONCLUSION

The presence of homotrimeric type I collagen isotype (absence of alpha2(I) collagen) significantly weakens the aorta. This study demonstrates the integral role of type I collagen in the biomechanical and functional properties of the aorta and may help to elucidate the role of collagen in the development of aneurysmal aortic disease or dissection.

Hypercalcaemia in osteogenesis imperfecta treated with pamidronate

The response to the bisphosphonate, pamidronate, is reported in a child with osteogenesis imperfecta who had recurrent symptomatic hypercalcaemia after immobilisation following fractures. Oral clodronate was effective in the prevention of immobilisation hypercalcaemia in the same child. The bisphosphonates may have other roles in osteogenesis imperfecta by decreasing bone turnover.

Osteogenesis imperfecta and cardiovascular diseases

Aortic and mitral valvular insufficiency in patients with osteogenesis imperfecta result from an underlying defect in connective tissue formation. The surgical cases reported in the literature have included mechanical and bioprosthetic valve replacement as well as attempts at repair and reconstruction. Despite complications related to bleeding and tissue friability, acceptable results have been obtained. In this report, we describe aortic regurgitation secondary to osteogenesis imperfecta treated with homograft replacement. The unique cardiovascular complications of osteogenesis imperfecta and the available therapeutic options are discussed in light of the literature review.

Hypercalciuria in osteogenesis imperfecta: a follow-up study to assess renal effects

In 1991, we reported that hypercalciuria is a common finding in our pediatric patient population with osteogenesis imperfecta (OI) (17 of 47 = 36%). Here, we prospectively screened 12 of these hypercalciuric children, on average 4 years subsequent to the discovery of elevated urine calcium levels, for adverse effects on renal function. Despite an ad libitum decrease since initial investigation of about 30% in their previously normal dietary calcium intake (adjusted for body weight), 8 of the 12 patients remained hypercalciuric (urine calcium/creatinine > 0.62 mmol/mmol). We found, once again, that urinary calcium levels significantly correlated with the severity of the skeletal disease as assessed by z-score for height (r = -0.75, p = 0.005). Evaluation of kidney function, however, revealed: (i) normal routine urinalysis in all but 1 subject who had transient microscopic hematuria; (ii) unremarkable concentrating ability determined by fasting urine osmolality; (iii) normal creatinine clearance, and (iv) unremarkable ultrasonography to measure renal size and to screen for nephrocalcinosis or nephrolithiasis. Although no significant renal compromise was detected with these studies in our hypercalciuric pediatric OI patients, investigation of affected adults, especially those severely affected, will be important to assess whether this is a long-term problem and if adverse effects on the kidneys do develop.

An unusual renal complication in a patient with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a common 'rare' disorder with a reported incidence of 1/15,000 to 1/20,000 in newborns. Skeletal abnormalities in this condition are so striking that its equally important and diverse extraskeletal manifestations frequently remain unnoticed. Sensorineural deafness, blue sclerae, myopia, easy bruisability, dental anomalies, and floppy mitral valves are some of its more frequently reported extraskeletal features. Other less common features include pulmonary hypoplasia, joint contractures, hydrocephalus, and osteogenic sarcoma. Our patient, a 16-year-old boy, developed a previously unreported complication: chronic renal failure, which on subsequent evaluation was attributed to obstructive uropathy secondary to bony pelvic outlet deformities.

Clinical management of osteogenesis imperfecta

Knowledge of the natural history of different types of OI permits planning of rehabilitation goals for children with OI. Notwithstanding this knowledge, rehabilitation will need to be modified to accommodate unexpected fractures and the highly variable chance of deformity in each individual. Immobilisation should be minimized to avoid immobilization osteoporosis. New rehabilitation issues include basilar impression, recommencement of fractures in postmenopausal women with OI, pregnancy related bone loss and sleep apnoea.

Bone resorption assessed by immunoassay of urinary cross-linked collagen peptides in patients with osteogenesis imperfecta

Urinary excretion of type I collagen cross-linked N-telopeptides was studied in 52 children and adolescents with osteogenesis imperfecta (OI) and found to be above the 75th percentile of controls in 44 of the patients. OI patients suffering from fractures during the preceding 6 months had significantly higher values (p < 0.05). In contrast, patients with better motor performance tended to have lower values (p = 0.059). The concentration of urinary type I collagen cross-linked N-telopeptides was positively correlated with urinary calcium excretion (p < 0.05), which was found to be elevated in 20 of the patients. Our results show that during childhood and adolescence in OI not only the synthesis but also the turnover of mature cross-linked type I collagen is disturbed and provide evidence that bone resorption rates are elevated.

Osteogenesis imperfecta: a clinical study of the first ten years of life

One hundred twenty-seven children with osteogenesis imperfecta (O.I.) were studied during the first 10 years of life. According to Sillence, 40 patients were assigned to type I, 39 to type III, and 48 to type IV O.I. Centiles for height, weight, and the annual number of fractures could be established for the different types of O.I. The development of the skeletal changes could be documented for the different forms of the disease. At birth, the skeletal changes were significantly more severe in type III than in type IV patients. During the first 10 years of life the number of fractures, extent of skeletal deformities, and growth retardation did not differ between types III and IV. Only fracture nonunion, dentinogenesis imperfecta, and congenital cardiac malformations were more frequent in type III than in type IV. Papillary calcifications of the kidney and kidney stones were diagnosed in 4 type III and 2 type IV patients. Hemihypertrophy of the body developed in 2 type I patients. Although types III and IV patients suffered from severe short stature, serum insulin-like growth factor (IGF) I was in the normal range.

Hypercalciuria in children severely affected with osteogenesis imperfecta

To investigate our impression that hypercalciuria is relatively common in children with osteogenesis imperfecta, we performed a retrospective study of data accumulated from our pediatric population with this skeletal disorder. Children with osteogenesis imperfecta (17 girls, 30 boys; mean (+/- SD) age 7.8 +/- 4.6 years; range 0.7 to 16.8 years) had undergone detailed inpatient evaluation of mineral homeostasis during periods of clinical stability and controlled dietary calcium intake. Hypercalciuria was found in 36% of the patients and averaged (+/- SEM) 6.1 +/- 0.3 mg/kg per 24 hours (0.15 +/- 0.01 mmol/kg per 24 hours) or 392 +/- 28 mg/gm of creatinine (1.10 +/- 0.07 mmol calcium/mmol creatinine) in the group with hypercalciuria. There were no statistically significant differences in age, gender, or dietary calcium intake (per kilogram of body weight) between the normocalciuric and hypercalciuric children. However, the group with hypercalciuria was shorter than the normocalciuric group and had a greater lifelong fracture rate. When patient height z scores were regressed against urinary calcium levels, a significant negative correlation was found in the group with hypercalciuria (r = -0.76; p less than 0.001). Although serum alkaline phosphatase activity was lower in the group with hypercalciuria, no difference was found between groups with regard to serum levels of calcium, phosphate, magnesium, creatinine, immunoreactive parathyroid hormone, or osteocalcin. The groups were also similar with respect to both their total body mineral density, as determined by dual-photon absorptiometry (n = 17), and their static indexes of bone formation and resorption, as assessed histomorphometrically with iliac crest specimens (n = 19). We conclude that hypercalciuria occurs frequently in children with osteogenesis imperfecta, and that its magnitude appears to reflect the severity of the skeletal disease.