Phenotypic Spectrum and Molecular Basis in a Chinese Cohort of Osteogenesis Imperfecta With Mutations in Type I Collagen

Multi-omics analyses reveal aberrant differentiation trajectory with WNT1 loss-of-function in type XV osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a group of severe genetic bone disorders characterized by congenital low bone mass, deformity, and frequent fractures. Type XV OI is a moderate to severe form of skeletal dysplasia caused by WNT1 variants. In this cohort study from southern China, we summarized the clinical phenotypes of patients with WNT1 variants and found that the proportion of type XV patients was around 10.3% (25 out of 243) with a diverse spectrum of phenotypes. Functional assays indicated that variants of WNT1 significantly impaired its secretion and effective activity, leading to moderate to severe clinical manifestations, porous bone structure, and enhanced osteoclastic activities. Analysis of proteomic data from human skeleton indicated that the expression of SOST (sclerostin) was dramatically reduced in type XV patients compared to patients with COL1A1 quantitative variants. Single-cell transcriptome data generated from human tibia samples of patients diagnosed with type XV OI and leg-length discrepancy, respectively, revealed aberrant differentiation trajectories of skeletal progenitors and impaired maturation of osteocytes with loss of WNT1, resulting in excessive CXCL12+ progenitors, fewer mature osteocytes, and the existence of abnormal cell populations with adipogenic characteristics. The integration of multi-omics data from human skeleton delineates how WNT1 regulates the differentiation and maturation of skeletal progenitors, which will provide a new direction for the treatment strategy of type XV OI and relative low bone mass diseases such as early onset osteoporosis.

Identification of a family with van der Hoeve's syndrome harboring a novel COL1A1 mutation and generation of patient-derived iPSC lines and CRISPR/Cas9-corrected isogenic iPSCs

Van der Hoeve's syndrome, also known as osteogenesis imperfecta (OI), is a genetic connective tissue disorder characterized by fragile, fracture-prone bone and hearing loss. The disease is caused by a gene mutation in one of the two type I collagen genes COL1A1 or COL1A2. In this study, we identified a novel frameshift mutation of the COL1A1 gene (c.1607delG) in a family with OI using whole-exome sequencing, bioinformatics analysis and Sanger sequencing. This mutation may lead to the deletion of a portion of exon 23 and the generation of a premature stop codon in the COL1A1 gene. To further investigate the impact of this mutation, we established two induced pluripotent stem cell (iPSC) lines from peripheral blood mononuclear cells of OI patients carrying a novel mutation in the COL1A1 gene. Osteoblasts (OB) derived from OI-iPSCs exhibited reduced production of type I collagen and diminished ability to differentiate into osteoblasts. Using a CRISPR-based homology-directed repair strategy, we corrected the OI disease-causing COL1A1 novel mutations in iPSCs generated from an affected individual. Our results demonstrated that the diminished expression of type I collagen and osteogenic potential were enhanced in OB induced from corrected OI-iPSCs compared to those from OI-iPSCs. Overall, our results provide new insights into the genetic basis of Van der Hoeve's syndrome and highlight the potential of iPSC technology for disease modeling and therapeutic development.

Osteogenesis imperfecta: a cross-sectional study of skeletal and extraskeletal features in a large cohort of Italian patients

Introduction

The present study aims to describe a large cohort of Italian patients affected by osteogenesis imperfecta, providing a picture of the clinical bony and non-bony features and the molecular background to improve knowledge of the disease to inform appropriate management in clinical practice.

Methods

A total of 568 subjects (from 446 unrelated Italian families) affected by osteogenesis imperfecta who received outpatient care at Istituto Ortopedico Rizzoli from 2006 to 2021 were considered in the present study.

Results

Skeletal and extraskeletal features were analyzed showing a lower height (mean z-scores equal to -1.54 for male patients and -1.47 for female patients) compared with the general Italian population. Half of the patient population showed one or more deformities, and most of the patients had suffered a relatively low number of fractures (<10). An alteration in the sclera color was identified in 447 patients. Similarly, several extraskeletal features, like deafness, dental abnormalities, and cardiac problems, were investigated. Additionally, inheritance and genetic background were evaluated, showing that most of the patients have a positive family history and the majority of pathogenic variants detected were on collagen genes, as per literature.

Conclusion

This study supports the definition of a clear picture of the heterogeneous clinical manifestations leading to variable severity in terms of skeletal and extra-skeletal traits and of the genetic background of an Italian population of osteogenesis imperfecta patients. In this perspective, this clearly highlights the crucial role of standardized and structured collection of high-quality data in disease registries particularly in rare disease scenarios, helping clinicians in disease monitoring and follow-up to improve clinical practice.

Genotype-phenotype relationship and comparison between eastern and western patients with osteogenesis imperfecta

PURPOSE

To evaluate the genotypic and phenotypic relationship in a large cohort of OI patients and to compare the differences between eastern and western OI cohorts.

METHODS

A total of 671 OI patients were included. Pathogenic mutations were identified, phenotypic information was collected, and relationships between genotypes and phenotypes were analyzed. Literature about western OI cohorts was searched, and differences were compared between eastern and western OI cohorts.

RESULTS

A total of 560 OI patients were identified as carrying OI pathogenic mutations, and the positive detection rate of disease-causing gene mutations was 83.5%. Mutations in 15 OI candidate genes were identified, with COL1A1 (n = 308, 55%) and COL1A2 (n = 164, 29%) being the most common mutations, and SERPINF1 and WNT1 being the most common biallelic variants. Of the 414 probands, 48.8, 16.9, 29.2 and 5.1% had OI types I, III, IV and V, respectively. Peripheral fracture was the most common phenotype (96.6%), and femurs (34.7%) were most commonly affected. Vertebral compression fracture was observed in 43.5% of OI patients. Biallelic or COL1A2 mutation led to more bone deformities and poorer mobility than COL1A1 mutation (all P < 0.05). Glycine substitution of COL1A1 or COL1A2 or biallelic variants led to more severe phenotypes than haploinsufficiency of collagen type I α chains, which induced the mildest phenotypes. Although the gene mutation spectrum varied among countries, the fracture incidence was similar between eastern and western OI cohorts.

CONCLUSION

The findings are valuable for accurate diagnosis and treatment of OI, mechanism exploration and prognosis judgment. Genetic profiles of OI may vary among races, but the mechanism needs to be explored.

Scoliosis in osteogenesis imperfecta: identifying the genetic and non-genetic factors affecting severity and progression from longitudinal data of 290 patients

BACKGROUND

Scoliosis is widely prevalent among osteogenesis imperfecta (OI) patients, and is progressive with age. However, factors affecting scoliosis in OI are not well known.

METHODS

We retrospectively retrieved longitudinal radiographic and clinical records of consecutive OI patients seeking treatments at our hospital from 2014 to 2022, graded their pre-operative spinal conditions into four outcome groups, estimated their progression rates, and descriptively and inferentially analyzed the genetic and non-genetic factors that may affect the outcomes and progression rates.

RESULTS

In all, 290 OI patients met the inclusion criteria, where 221 had genetic records. Of these 221, about 2/3 had mutations in COL1A1 or COL1A2, followed by mutations in WNT1 (9.0%), IFITM5 (9.0%) and other OI risk genes. With an average age of 12.0 years (interquartile range [IQR] 6.9-16.1), 70.7% of the cohort had scoliosis (Cobb angle > 10°), including 106 (36.5%) mild (10°-25°), 40 (13.8%) moderate (25°-50°), and 59 (20.3%) severe (> 50°) scoliosis patients. Patients with either COL1A1 and COL1A2 were strongly biased toward having mild or no scoliosis, whereas patients with mutations in IFITM5, WNT1 and other recessive genes were more evenly distributed among the four outcome grades. Lower-limb discrepancy, bone mineral density (BMD) and age of first drug used were all significantly correlated with severity outcomes. Using multivariate logistic regression, we estimated that each year older adds an odds ratio of 1.13 (95% confidence interval [CI] 1.07-1.2) in progression into advanced stages of scoliosis. We estimated a cohort-wide progression rate of 2.7 degrees per year (95% CI 2.4-3.0). Early-onset patients experienced fast progressions during both infantile and adolescent stages. Twenty-five of the 59 (42.8%) patients with severe scoliosis underwent spinal surgeries, enjoying an average Cobb angle reduction of 33° (IQR 23-40) postoperatively.

CONCLUSION

The severity and progression of scoliosis in osteogenesis imperfecta were affected by genetic factors including genotypes and mutation types, and non-genetic factors including age and BMD. As compared with COL1A1, mutations in COL1A2 were less damaging while those on IFITM5 and other recessive genes conferred damaging effects. Progression rates were the fastest in the adolescent adult age-group.

Null and missense mutations of ERI1 cause a recessive phenotypic dichotomy in humans

ERI1 is a 3'-to-5' exoribonuclease involved in RNA metabolic pathways including 5.8S rRNA processing and turnover of histone mRNAs. Its biological and medical significance remain unclear. Here, we uncover a phenotypic dichotomy associated with bi-allelic ERI1 variants by reporting eight affected individuals from seven unrelated families. A severe spondyloepimetaphyseal dysplasia (SEMD) was identified in five affected individuals with missense variants but not in those with bi-allelic null variants, who showed mild intellectual disability and digital anomalies. The ERI1 missense variants cause a loss of the exoribonuclease activity, leading to defective trimming of the 5.8S rRNA 3' end and a decreased degradation of replication-dependent histone mRNAs. Affected-individual-derived induced pluripotent stem cells (iPSCs) showed impaired in vitro chondrogenesis with downregulation of genes regulating skeletal patterning. Our study establishes an entity previously unreported in OMIM and provides a model showing a more severe effect of missense alleles than null alleles within recessive genotypes, suggesting a key role of ERI1-mediated RNA metabolism in human skeletal patterning and chondrogenesis.

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.

Clinical features and molecular characterization of Chinese patients with FKBP10 variants

BACKGROUND

Osteogenesis imperfecta (OI) is a group of rare skeletal dysplasia. Long bone deformity and scoliosis are often associated with progressively deforming types of OI. FKBP65 (encoded by FKBP10, OMIM *607063) plays a crucial role in the processing of type I procollagen. Autosomal recessive variants in FKBP10 result in type XI osteogenesis imperfecta.

METHODS

Patients diagnosed with OI were recruited for a genetic test. RT-PCR and Sanger sequencing were applied to confirm the splicing defect in FKBP10 mRNA with the splice-site variant. The bone structure was characterized by Goldner's trichrome staining. Bioinformatic analyses of bulk RNA sequencing data were performed to examine the effect of the FKBP10 variant on gene expression.

RESULTS

Here we reported three children from a consanguineous family harboured a homozygous splice-site variant (c.918-3C > G) in FKBP10 intron and developed long bone deformity and early onset of scoliosis. We also observed frequent long bone fractures and spinal deformity in another 3 OI patients with different FKBP10 variants. The homozygous splicing variant identified in the fifth intron of FKBP10 (c.918-3C > G) led to abnormal RNA processing and loss of FKBP65 protein and consequently resulted in aberrant collagen alignment and porous bone morphology. Analysis of transcriptomic data indicated that genes involved in protein processing and osteoblast differentiation were significantly affected in the patient-derived osteoblasts.

CONCLUSION

Our study characterized the clinical features of OI patients with FKBP10 variants and revealed the pathogenesis of the c.918-3C > G variant. The molecular analyses helped to gain insight into the deleterious effects of FKBP10 variants on collagen processing and osteoblast differentiation.

Perthes Disease in a Child With Osteogenesis Imperfecta From a Rare Genetic Variant: A Case Report

Background: Although certain genetic components have been reported as contributing factors for Perthes disease, its etiology remains unclear. We present a rare case of Perthes disease in a child with osteogenesis imperfecta (OI) caused by a mutation in the COL1A1 gene (NM_000088):exon25:c.1726C>T, (p.Gln576X).

Case presentations: A 7-year-old boy was initially treated at our medical facility in March 2016 with a history of chronic pain in right hip joint and limping for a year. He was diagnosed as Perthes disease in the right hip joint. He underwent acetabular osteotomy and ipsilateral proximal femoral varus osteotomy for better containment. During the follow-ups, the right hip demonstrated a normal range of motion without pain, and the pelvic X-ray demonstrated Stulberg Type II hip joint with a round femoral head. In the latest admission in 2022, he suffered from a right femoral shaft fracture after petty violence. After reviewing his medical history, he was suspected of having OI. The whole exome sequencing demonstrated a gene mutation in COL1A1 (OMIM 166200) and confirmed the diagnosis of OI. Telescopic nailing was used to treat the femoral shaft fracture. After the nailing of the right femur, the appearance of the lower extremity seemed normal and symmetrical.

Conclusion: This study revealed that there might be an association between OI and Perthes disease. Our case report enriches the phenotypes of osteogenesis imperfecta and provides insight into the pathogenesis of LCPD.

Comprehensive risk assessments and anesthetic management for children with osteogenesis imperfecta: A retrospective review of 252 orthopedic procedures over 5 years

BACKGROUND

Major anesthetic risks arise in orthopedic surgeries for children with osteogenesis imperfecta, a rare genetically inherited condition presenting diverse skeletal issues.

AIM

We aimed to investigate anesthetic risks, including difficult airway, hypo- and hyperthermia, blood loss, and pain, in connection with patient, anesthetic, and surgical factors.

METHODS

Both descriptive and inferential statistics were employed to study the anesthetic risks and their predictors. Data of 252 surgeries for 132 Chinese osteogenesis imperfecta patients aged 18 or below were retrieved from the authors' hospital between 2015 and 2019.

RESULTS

Two thirds of the cohort were Sillence type IV patients, with types I, III, and V accounting for 7.6%, 14.4%, and 11.4%, respectively. Video and direct laryngoscopy were used. No case of difficult airway was identified. Due to a careful management strategy, intraoperative temperature varied on average between -0.38°C and +0.89°C from the initial temperature. Fifty-two and 18 cases of hyper- and hypothermia were encountered, respectively. The use of sevoflurane for maintenance resulted in a mean increase of +0.24°C [95% CI 0.05 ~ 0.42] in the maximum temperature. Massive blood losses (>20% of estimated total blood volume) were observed in 18.3% of the cases. Neither intraoperative temperature changes nor blood loss was found to be related to Sillence classification. Regional anesthesia techniques were applied to 72.6% of the cases. Ultrasound guidance was used per the judgment of anesthesiologists or when in case of difficult landmarks. The incidence of difficult regional anesthesia was low (4 out of 252). For postoperative analgesia, 154 neuraxial blocks (including 77 caudal and 77 lumbar epidural) and 29 peripheral nerve blocks were performed.

CONCLUSION

Anesthesia for children with osteogenesis imperfecta undergoing complex orthopedic procedures was challenging. Proper anesthesia planning was essential for both intraoperative management and postoperative analgesia. Age, surgical duration, and use of sevoflurane for maintenance impacted the intraoperative temperature most, and massive blood loss was not uncommon. The risks for airway or regional anesthesia difficulties were low. Pain scores could be controlled to be ≤3 via multiple techniques.

Patient-reported outcomes in a Chinese cohort of osteogenesis imperfecta unveil psycho-physical stratifications associated with clinical manifestations

Background

Osteogenesis imperfecta (OI) is a rare congenital disorder of the skeletal system, inflicting debilitating physical and psychological distress on patients and caregivers. Over the decades, much effort has been channeled towards understanding molecular mechanisms and developing new treatments. It has recently become more apparent that patient-reported outcome measurements (PROM) during treatment, healing and rehabilitation are helpful in facilitating smoother communication, refining intervention strategies and achieving higher quality of life. To date, systematic analyses of PROM in OI patients remain scarce.

Results

Here, utilizing a PROM Information System, we report a cross-sectional and longitudinal study in a southern Chinese cohort of 90 OI patients, covering both the child and adult age-groups. In the child group where both self and parental surveys were obtained, we identified two clusters of comparable sizes showing different outlooks in physical mobility and emotional experiences. One cluster (Cluster 1) is more negative about themselves than the other (Cluster 2). A concordance of 84.7% between self and parental assessments was recorded, suggesting the stability and validity of PROM-based stratification. Clinical subtyping, deformity, leg length discrepancy, and limited joint mobility were significantly associated with this stratification, with Cluster 1 showing higher percentages of severe phenotypes than Cluster 2. Since OI is a genetic disorder, we performed genetic testing on 72 of the 90 patients, but found no obvious association between genotypes and the PROM stratification. Analyses of longitudinal data suggested that patients tended to stay in the same psychological state, in both clusters. Adult patients also showed a continuous spectrum of self-evaluation that matches their clinical manifestations.

Conclusion

By systematically analyzing patient-reported outcomes, our study demonstrated the link between the sociopsychological wellbeing of OI patients, and their clinical manifestations, which may serve as the basis for evaluating clinical interventions and help achieve better patient-centric medical practices. The lack of genotype-PROM association may be due to the diverse mutational spectrum in OI, which warrants further investigation when a larger sample size is available.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02394-7.