Expanding the Clinical Spectrum of Osteogenesis Imperfecta Type V: 13 Additional Patients and Review

Imaging in osteogenesis imperfecta: Where we are and where we are going

Osteogenesis imperfecta (OI) is a rare phenotypically and genetically heterogeneous group of inherited skeletal dysplasias. The hallmark features of OI include bone fragility and susceptibility to fractures, bone deformity, and diminished growth, along with a plethora of associated secondary features (both skeletal and extraskeletal). The diagnosis of OI is currently made on clinical grounds and may be confirmed by genetic testing. However, imaging remains pivotal in the evaluation of this disease. The aim of this article is to review the current role played by the various radiologic techniques in the diagnosis and monitoring of OI in the postnatal setting as well as to discuss recent advances and future perspectives in OI imaging. Conventional Radiography and Dual-energy X-ray Absorptiometry (DXA) are currently the two most used imaging modalities in OI. The cardinal radiographic features of OI include generalized osteopenia/osteoporosis, bone deformities, and fractures. DXA is currently the most available technique to assess Bone Mineral Density (BMD), specifically areal BMD (aBMD). However, DXA has important limitations and cannot fully characterize bone fragility in OI based on aBMD. Novel DXA-derived parameters, such as Trabecular Bone Score (TBS), may provide further insight into skeletal changes induced by OI, but evidence is still limited. Techniques like Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) can be useful as problem-solvers or in specific settings, including the evaluation of cranio-cervical abnormalities. Recent evidence supports the use of High-Resolution peripheral Quantitative Computed Tomography (HR-pQCT) as a promising tool to improve the characterization of bone fragility in OI. However, HR-pQCT remains a primarily research technique at present. Quantitative Computed Tomography (QCT) is an alternative to DXA for the determination of BMD at central sites, with distinct advantages but considerably higher radiation exposure. Quantitative Ultrasound (QUS) is a portable, inexpensive, and radiation-free modality that may complement DXA evaluation, providing information on bone quality. However, evidence of usefulness of QUS in OI is poor. Radiofrequency Echographic Multi Spectrometry (REMS) is an emerging non-ionizing imaging method that holds promise for the diagnosis of low BMD and for the prediction of fracture risk, but so far only one published study has investigated its role in OI. To conclude, several different radiologic techniques have proven to be effective in the diagnosis and monitoring of OI, each with their own specificities and peculiarities. Clinicians should be aware of the strategic role of the various modalities in the different phases of the patient care process. In this scenario, the development of international guidelines including recommendations on the role of imaging in the diagnosis and monitoring of OI, accompanied by continuous active research in the field, could significantly improve the standardization of patient care.

Retrospective analyses of clinical features in 28 Chinese patients with type V osteogenesis imperfecta: new perspectives in an old issue

Type V osteogenesis imperfecta (OI) is a form of OI characterized by radial head dislocation (RHD), calcification of interosseous membrane (CIM), and hyperplastic callus (HPC). In this study, we characterized the clinical features of 28 type V OI patients. We presented that dysfunctions of elbow, hip joint, and abnormal epiphyseal growth plate were associated with ectopic calcification and summarized the history of HPC progression and treatment.

INTRODUCTION

The current study aims to systematically characterize the skeletal phenotypes of patients with type V OI and suggested possible surgical solutions.

METHODS

A total of 28 patients were admitted for inpatient care at The Hong Kong University-Shenzhen Hospital diagnosed with type V OI (either clinically diagnosed or genetically confirmed with the IFITM5 c.-14C > T mutation).

RESULTS

Prevalence of type V radiological features was comparable to previous literatures (RHD, 100%; CIM, 100%; HPC, 44%; and scoliosis, 50%). Novel skeletal phenotypes were presented including extension of coronoid process, acetabular labrum, acetabular protrusion, spontaneous autofusion of the hip, bulbous epiphysis, and popcorn calcification. Significant increase in BMD was observed in patients with bisphosphonate treatment. Twenty-five percent (3/12) of patients with preoperative use of indomethacin developed HPC postoperatively, and HPCs were absorbed in 2 young patients 2 years later.

CONCLUSION

This retrospective study summarized the clinical features and highlighted the abnormalities in elbow, hip joint, and growth plate in type V OI patients. Our study contributed to a more comprehensive clinical spectrum of type V OI. We also characterized the natural progression of HPC formation and resorption in patients in different ages. The use of bisphosphonate treatment is effective in improving bone mineral density in type V OI patients, and whether indomethacin can reduce incidence of HPC formation deserves further investigation.

Exploration of the skeletal phenotype of the Col1a1 +/Mov13 mouse model for haploinsufficient osteogenesis imperfecta type 1

INTRODUCTION

Osteogenesis Imperfecta is a rare genetic connective tissue disorder, characterized by skeletal dysplasia and fragile bones. Currently only two mouse models have been reported for haploinsufficient (HI) mild Osteogenesis Imperfecta (OI); the Col1a1 ^+/Mov13 (Mov13) and the Col1a1 ^+/-365 mouse model. The Mov13 mice were created by random insertion of the Mouse Moloney leukemia virus in the first intron of the Col1a1 gene, preventing the initiation of transcription. Since the development of the Mov13 mice almost four decades ago and its basic phenotypic characterization in the 90s, there have not been many further studies. We aimed to extensively characterize the Mov13 mouse model in order to critically evaluate its possible use for preclinical studies of HI OI.

METHODS

Bone tissue from ten heterozygous Mov13 and ten wild-type littermates (WT) C57BL/6J mice (50% males per group) was analyzed at eight weeks of age with bone histomorphometry, micro computed tomography (microCT), 3-point bending, gene expression of different collagens, as well as serum markers of bone turnover.

RESULTS

The Mov13 mouse presented a lower bone strength and impaired material properties based on our results of 3-point bending and microCT analysis respectively. In contrast, no significant differences were found for all histomorphometric parameters. In addition, no significant differences in Col1a1 bone expression were present, but there was a significant lower P1NP concentration, a bone formation marker, measured in serum. Furthermore, bone tissue of Mov13 mice presented significantly higher expression of collagens (Col1a2, Col5a1 and Col5a2), and bone metabolism markers (Bglap, Fgf23, Smad7, Edn1 and Eln) compared to WT. Finally, we measured a significantly lower Col1a1 expression in heart and skin tissue and also determined a higher expression of other collagens in the heart tissue.

CONCLUSION

Although we did not detect a significant reduction in Col1a1 expression in the bone tissue, a change in bone structure and reduction in bone strength was noted. Regrettably, the variability of the bone phenotype and the appearance of severe lymphoma in adult Mov13 mice, does not favor their use for the testing of new long-term drug studies. As such, a new HI OI type 1 mouse model is urgently needed.

Osteogenesis imperfecta and rheumatoid arthritis: connective issues

The coexistence of osteogenesis imperfecta and inflammatory arthritis has been very rarely described. Nevertheless, systemic inflammation has been found in osteogenesis imperfecta. The COL1A1 mutations may affect collagen synthesis as well as post-translational modifications, extracellular matrix interactions, and receptor-mediated signaling. Major collagen binding ligands forming the interactome, such as cytokines, cell adhesion molecules, matrix metalloproteinases, proteoglycans, and other molecules, are autoimmunity targets involved in rheumatoid arthritis pathogenesis. Cross-talk between bone remodeling and inflammatory pathways involving osteoclasts is important in osteogenesis imperfecta and rheumatoid arthritis. In osteogenesis imperfecta, the structural abnormalities and repeated traumatism, including fractures, could activate locally the innate immunity and trigger arthritis, similar to post-traumatic arthritis. Currently, the therapy of osteogenesis imperfecta is a suboptimally met need. Understanding the complex putative pathogenic links between osteogenesis imperfecta and inflammatory arthritis could hopefully lead to new therapeutic targets. Raising awareness regarding a possible association between osteogenesis imperfecta and arthritis could help improve the quality of life in these patients.

Does the c.-14C>T Mutation in the IFITM5 Gene Provide Identical Phenotypes for Osteogenesis Imperfecta Type V? Data from Russia and a Literature Review

Osteogenesis imperfecta (OI) is a large group of genetically heterogeneous diseases resulting from decreased bone density and an abnormal microarchitecture, which are clinically manifested by abnormal bone fractures. A distinctive clinical feature of this group of diseases is the presence of spontaneous fractures and skeletal deformities. However, the clinical manifestations of different types of OI are characterized by marked polymorphism with variable severity of skeletal and extra-skeletal features. Previous studies have shown that a mutation (c.-14C>T) in the IFITM5 gene is responsible for autosomal dominant OI type V. However, the mutation has a variable expression pattern and marked clinical heterogeneity. In this study, a clinical and genetic analysis of 12 cases with molecularly confirmed OI type V from 12 unrelated families was performed. Significant clinical heterogeneity of the disease with the same molecular defect was detected. In six subjects (50%), there were no classic signs of OI type V (formation of a hyperplastic bone callus, calcification of the interosseous membrane and dislocation of the radial head). In all cases, the mutation occurred de novo.

Quantitative increase in T regulatory cells enhances bone remodeling in osteogenesis imperfecta

Osteogenesis imperfecta (OI) is characterized by repeated bone fractures. Recent studies have shown that T lymphocytes and regulatory T cells (Tregs) regulate the functions of osteoclasts and osteoblasts, thus playing a role in bone turnover. We demonstrate an activated effector phenotype and higher secretion of pro-inflammatory cytokines, IFN-γ, and TNF-α in OI peripheral T cells as compared with wild-type (WT). Suppressive Tregs (spleen and thymus) were qualitatively similar, whereas there was a quantitative decrease in OI versus WT. Restoring Treg numbers by systemic transplantation in OI mice resulted in reduced T cell activation and effector cytokine secretion that correlated with significant improvements in tibial trabecular and cortical bone parameters and stiffness of femur, along with increased osteoblast mineralization and decreased osteoclast numbers. Therefore, Tregs can dampen the pro-inflammatory environment and enhance bone remodeling in OI mice. Thus, this study will be helpful in developing future autologous immunotherapy-based treatment modalities for OI.

Lessons learnt from prenatal exome sequencing

Background

Prenatal exome sequencing (ES) for monogenic disorders in fetuses with structural anomalies increases diagnostic yield. In England there is a national trio ES service delivered from two laboratories. To minimise incidental findings and reduce the number of variants investigated, analysis uses a panel of 1205 genes where pathogenic variants may cause abnormalities presenting prenatally. Here we review our laboratory's early experience developing and delivering ES to identify challenges in interpretation and reporting and inform service development.

Methods

A retrospective laboratory records review from 01.04.2020 to 31.05.2021.

Results

Twenty‐four of 116 completed cases were identified as challenging including 13 resulting in difficulties in analysis and reporting, nine where trio inheritance filtering would have missed the diagnosis, and two with no prenatal diagnosis; one due to inadequate pipeline sensitivity, the other because the gene was not on the panel. Two cases with copy number variants identified were not detectable by microarray.

Conclusions

Variant interpretation requires close communication between referring clinicians, with occasional additional examination of the fetus or parents and communication of evolving phenotypes. Inheritance filtering misses ∼5% of diagnoses. Panel analysis reduces but does not exclude incidental findings. Regular review of published literature is required to identify new reports that may aid classification.

What's already known about this topic?

Prenatal exome sequencing (ES) for monogenic disorders in fetuses with structural anomalies is known to increase diagnostic yield

Diagnostic prenatal ES services are being embedded into clinical practice internationally

What does this study add?

This study identifies challenges encountered running a diagnostic prenatal ES service including those in variant interpretation and reporting, incidental findings and ethical issues

It demonstrates that solely relying on trio inheritance filtering will miss ∼5% of diagnoses

Close communication between scientists and referring clinicians is essential to identify evolving phenotypes

Regular review of published literature is required to identify new reports that may alter variant classification

Specific Characteristic of Hyperplastic Callus in a Larger Cohort of Osteogenesis Imperfecta Type V

Hyperplastic callus (HPC) is the most conspicuous features of osteogenesis imperfecta (OI) type V, of which accurate diagnosis and treatment are facing challenges. We investigate the clinical features, and impact factors of HPC in OI type V patients. In this retrospective single-center study, a total of 21 patients with type V OI confirmed by IFITM5 mutation were included. Radiological characteristics of bone were evaluated by X-rays, dual-energy X-ray absorptiometry, and computed tomography scan. Bone biopsy specimens were performed and stained by routine hematoxylin-eosin. The effects of bisphosphonates on HPC were investigated. Eleven patients (52.3%) had HPCs at 19 skeletal sites, 11 of which affected the femur. Three patients developed four (21.1%) HPCs after fractures, and 15 (78.9%) HPCs occurred in absence of bone fracture. The progress of HPCs was variable, of which most HPCs enlarged in the initial phase and remained stable, and only one HPC dwindled in size. One patient had a rapidly growing mass on the right humerus, and biopsy showed irregular trabeculae of woven bone and immature bone and cartilage in the loose and edematous collagenous network without signs of tumor. Bisphosphonates treatment had no significant effects on HPC of OI patients. HPC is the specific characteristic of OI type V patients, and its location, shape, size, and progression are variable, and the femur is the most frequently involved site. It is very important to make a diagnosis of HPC through detecting IFITM5 mutation and completing pathological diagnosis if necessary. The treatment of HPC is worth further exploration.

The Osteogenesis Imperfecta Type V Mutant BRIL/IFITM5 Promotes Transcriptional Activation of MEF2, NFATc, and NR4A in Osteoblasts

BRIL (bone restricted ifitm-like; also known as IFITM5) is a transmembrane protein expressed in osteoblasts. Although its role in skeletal development and homeostasis is unknown, mutations in BRIL result in rare dominant forms of osteogenesis imperfecta. The pathogenic mechanism has been proposed to be a gain-of or neomorphic function. To understand the function of BRIL and its OI type V mutant (MALEP BRIL) and whether they could activate signaling pathways in osteoblasts, we performed a luciferase reporter assay screen based on the activity of 26 transcription factors. When overexpressed in MC3T3-E1 and MLO-A5 cells, the MALEP BRIL activated the reporters dependent on MEF2, NFATc, and NR4A significantly more. Additional co-transfection experiments with MEF2C and NFATc1 and a number of their modulators (HDAC4, calcineurin, RCAN, FK506) confirmed the additive or synergistic activation of the pathways by MALEP, and suggested a coordinated regulation involving calcineurin. Endogenous levels of Nr4a members, as well as Ptgs2, were upregulated by MALEP BRIL. Y2H and co-immunoprecipitation indicated that BRIL interacted with CAML, but its contribution as the most upstream stimulator of the Ca²⁺-calcineurin-MEF2/NFATc cascade was not confirmed convincingly. Altogether the data presented provide the first ever readout to monitor for BRIL activity and suggest a potential gain-of-function causative effect for MALEP BRIL in OI type V, leading to perturbed signaling events and gene expression.

An Unusual Presentation of Osteogenesis Imperfecta: A Case Report

CASE

We report an 18-year-old patient with a clinical phenotype consistent with severe osteogenesis imperfecta (OI) with frequent fractures, short stature, shortening and bowing of extremities, and unusual radiographic features of severe fibrous dysplasia, including lytic lesions and a "ground-glass" appearance. Genetic testing for the patient was notable for a c.119C>T (p.Ser40Leu) variant in exon 1 of IFITM5 and a c.676C>A (Pro226Thr) variant in exon 5 of CREB3L1.

CONCLUSION

This unusual skeletal presentation was in the setting of a rare IFITM5 mutation and represents a unique case of severe OI.

Genotypic and Phenotypic Characteristics of 29 Patients With Rare Types of Osteogenesis Imperfecta: Average 5 Years of Follow-Up

Osteogenesis imperfecta (OI) is a rare genetic disorder characterized by bone fragility and abnormal connective tissue. Ninety percent of OI patients are caused by two mutations of COL1A1 and COL1A2, and more investigation was needed to better understand the rare types of OI. We followed up 29 patients with rare types of OI for an average of 5.4 years, and genotype, height, bone mineral density (BMD), blood biochemical indexes, misdiagnosis, and fracture were recorded. IFITM5 gene mutation was found in 18 patients (62.1%), which represents the most common pathogenic gene of rare types of OI in Chinese population. Thirteen cases had once been misdiagnosed, and the initial misdiagnosis rate was 44.8% (13/29). The higher misdiagnosis rate should be paid attention to by clinicians and healthcare providers, and we also give corresponding suggestions. Compared with the non-bisphosphonate treatment group, patients treated with bisphosphonates had higher lumbar spine BMD, fewer fractures, and lower levels of β-CTX and osteocalcin. However, there was no significant difference between OI type V patients and non-type V patients. Our study enriched the knowledge of genotype and phenotype characteristics of OI patients with rare types and bisphosphonate therapy.

Hospital admissions of patients with osteogenesis imperfecta in the English NHS

Hospital use by patients with osteogenesis imperfecta was largely unknown. This study found that the English NHS provides a significant number of hospital admissions to these patients, translating into large costs to the NHS. Admissions and costs both increased over time. Children under 14 years old accounted for more of the admissions and costs than any other age group.

INTRODUCTION

The aim of this study was to characterise hospital use by patients with osteogenesis imperfecta (OI) in the English National Health Service (NHS).

METHODS

Routinely collected aggregate data about all inpatient hospital records from patients with OI were used for the period 1 April 2014 to 31 March 2018. Information was extracted on number of admissions, number of patients, length of stay, and costs. Hospital use was summarised using descriptive statistics, categorising patients into 5-year age groups.

RESULTS

There were 16,245 hospital admissions for OI patients during the analysis period, with a total cost to the NHS of £24,052,451. Of the 4370 patients involved, 2700 (62%) were female. Female patients averaged 3.3 admissions per year and male patients 4.4 admissions per year. Patients aged 0 to 14 years old accounted for 54% of all admissions. Those aged 90 to 94 years had the longest average length of stay per admission (10.5 days) of any age group. Elective admissions cost on average £1260 and non-elective admissions £2529. Over the 4-year study period, number of admissions increased on average by 2.1% per year and number of patients by 6.4% per year.

CONCLUSION

The treatment of patients with OI is associated with a significant number of hospital admissions at an important cost for the NHS, with both number of admissions and costs increasing over time. Children below the age of 14 years had more admissions at a greater total cost than other ages, while the oldest adults had longer average stays and higher costs per admission.

Osteogenesis imperfecta: Novel genetic variants and clinical observations from a clinical exome study of 54 Indian patients

Osteogenesis imperfecta (OI) is a group of inherited disorders with increased bone fragility and wide genetic heterogeneity. We report the outcome of clinical exome sequencing validated by Sanger sequencing in clinically diagnosed 54 OI patients in Indian population. In 52 patients, we report 20 new variants involving both dominant and recessive OI-specific genes and correlate these with phenotypes. COL1A1 and COL1A2 gene variants were identified in 44.23%, of which 28.84% were glycine substitution abnormalities. Two novel compound heterozygous variants in the FKBP10 gene were seen in two unrelated probands. A novel heterogeneous duplication of chromosomal region chr17: 48268168-48278884 from exons 1-33 of the COL1A1 gene was found in one proband. In five probands, there were additional variants in association with OI. These were ANO5 in association with CRTAP in two probands of the same family causing gnathodiaphyseal dysplasia, COL5A2 with LEPRE1 causing Ehlers Danlos syndrome, COL11A1 in addition to COL1A1 causing Stickler syndrome, and a previously unreported combination of SLC34A1 gene variant with FKBP10 leading to Fanconi renal tubular syndrome type II. Our findings demonstrate the efficacy of clinical exome sequencing in screening OI patients, classifying its subtypes, and identifying associated disorders in consanguineous populations.

Immunomodulatory Effects of MSCs in Bone Healing

Mesenchymal stem cells (MSCs) are capable of differentiating into multilineage cells, thus making them a significant prospect as a cell source for regenerative therapy; however, the differentiation capacity of MSCs into osteoblasts seems to not be the main mechanism responsible for the benefits associated with human mesenchymal stem cells hMSCs when used in cell therapy approaches. The process of bone fracture restoration starts with an instant inflammatory reaction, as the innate immune system responds with cytokines that enhance and activate many cell types, including MSCs, at the site of the injury. In this review, we address the influence of MSCs on the immune system in fracture repair and osteogenesis. This paradigm offers a means of distinguishing target bone diseases to be treated with MSC therapy to enhance bone repair by targeting the crosstalk between MSCs and the immune system.