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Phenotypic spectrum and molecular basis in a Chinese cohort of osteogenesis imperfecta with mutations in type I collagen

ABSTRACT: Osteogenesis imperfecta (OI) is a rare inherited connective tissue dysplasia characterized with skeletal fragility, recurrent fractures and bone deformity, predominantly caused by mutations in the genes COL1A1 or COL1A2 that encode the chains of type I collagen. In the present study, clinical manifestations and genetic variants were analysed from 188 Chinese OI patients, majority of which are of southern China origin. By targeted sequencing, 64 and 58 OI patients were found carrying mutations in COL1A1 and COL1A2 respectively, including 12 novel COL1A1 and 8 novel COL1A2 variants. We identified a COL1A1 hotspot (c.G2461A; p.G821S) in 8 patients and validated two novel splicing mutations. A diverse mutational and phenotypic spectrum was observed, coupling with heterogeneity observed in the transcriptomic data (n=6) derived from osteoblasts of our cohort. Missense mutations were significantly associated (χ2 p=0.0096) with a cluster of patients with more severe clinical phenotypes. Additionally, the severity of OI was more correlated with the quality of bones, rather than the bone mineral density. Bone density is most responsive to bisphosphonate (BP) treatment during the juvenile stage (10-15 y/o). In contrast, height is not responsive to bisphosphonate treatment. Our findings expand the mutational spectrum of type I collagen genes and the genotype-phenotype correlation in Chinese OI patients. The observation of effective BP treatment in an age-specific manner may help to improve OI patient management.

ORGANISM(S): Homo sapiens

PROVIDER: GSE186141 | GEO | 2022/01/10

REPOSITORIES: GEO

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Project description:Osteogenesis Imperfecta (OI) is a genetic, rare disease characterized by bone fragility, with a wide range in the severity of clinical manifestations. The majority of the cases are due to mutations in COL1A1 or COL1A2 genes which code for the type I collagen molecule. Mesenchymal stem cells (MSCs), as the progenitors of the osteoblasts, the main type I collagen secreting cell type in the bone, have been proposed and tested as an innovative therapy for OI with promising but transient outcomes. In this study, we performed a phase I clinical trial based on reiterative infusions of histocompatible MSCs in two pediatric patients affected by severe and moderate OI. The aim of this study was to assess the safety and effectiveness of this cell therapy in non-immunosuppressed OI patients. The host response to MSCs was also evaluated by collecting the sera from OI patients before, along and after the cell therapy. The results of this clinical trial are twofold: the sequential administration of MSCs is safe and improve the bone parameters and quality of life of OI patients. Moreover, MSCs therapy elicits a pro-osteogenic paracrine response in patients, especially noticeable in that affected by severe OI. These results indicate the feasibility and potential of reiterative MSCs infusion for OI and highlight the paracrine response shown by OI patients as a consequence of MSCs treatment. Study design and patients: The Mesenchymal Stem Cell Therapy for the Treatment of Osteogenesis Imperfecta (TERCELOI) study (www.clinical trials.gov: # NCT02172885, EudraCT number: 2012-002553-38) is an independent multi-center Phase I clinical trial to evaluate the feasibility, safety and potential efficacy of infused sibling HLA-matched MSCs in non-immunosuppressed children with OI. PBMCs isolation and serum collection: Venous blood samples were collected before the cell therapy (basal serum), along the cell therapy (1 week, 1 month and 4 months after each MSCs infusion) and during the follow-up period (1 and 2 years after the fifth and last MSCs infusion). MLR assay: PBMCs isolated from patients were resuspended in PBS+FBS (5%) and stained with carboxyfluoroscein succinate-ester (CFSE) (Molecular Probes, USA). Bone mineral density: Bone mineral density (BMD) at the lumbar spine (LS) from L1 to L4, was measured by dual energy x-ray absorptiometry (DXA) on a whole-body scanner within a pediatric platform (Hologic QDR densitometer). Raw measurements were converted to Z-scores for analysis using reference standards for age and pubertal status. OI-MSCs isolation and characterization and culture: OI-MSCs were derived from discarded and donated bone fragments of OI pediatric patients undergoing corrective surgery. All patients suffered Type III-IV OI, with mutations in either COL1A1 or COL1A2 genes. The donation was approved by the Basque Clinical Research Ethics Committee. Briefly, bone chips were mechanically flushed with PBS and then cut into small pieces to extrude cells without the use of enzymes. The cut bone pieces were let undisturbed during 14 days until OI-MSCs migrated to cell culture plate. OI-MSCs were assessed for the expression of CD105, CD90 and CD73 and the absence of CD14, CD34, CD45, CD19 and HLA-DR. MSCs were also tested for their potential to differentiate to osteoblasts and adipocytes using specific cell culture media. OI-MSCs were cultured under standard growth medium (DMEM low glucose with glutamax (Gibco), penicillin/streptomycin (Gibco) and fetal bovine serum at 10% (Sigma-Aldrich, USA). Osteogenesis induction medium (OIM) was composed of standard medium plus ascorbic acid 0.2 mM, beta-glycerophosphate 10 mM, and dexamethasone 10 nM (all from Sigma-Aldrich). When specified, FBS was replaced by P01 and P02 serum samples at 2.5%. RNAseq and Q-PCR validation: OI-MSCs from 10 OI pediatric patients were seeded in 96-well plates (1 000 cells/well) and the following day cultured in the presence of OIM. Next, total RNA was isolated with the AllPrep kit (QIAGEN, USA). cDNA library (TrueSeq stranded Total cDNA library, Illumina, USA) and sequencing at HiSeq 4000 (PE100nt, 50 million reads/sample).

Project description:Col1a1 is located on mouse distal chromosome 11 (Celera 94607393-94622990bp; 15kb) and encodes type I procollagen that associates stoichiometrically with col1a2 in forming secreted type I mature collagen that self-assembles into a supramolecular fibrillar structure consisting of a protein family. Type I collagens are predominantly enriched in bone, cartilage, skin, tendons, and eye (i.e. in major fibrous tissues) making up the main extracellular matrix (ECM) component for support and scaffolding purposes. Col1a1 is known to be expressed in the embryo (E9.5; Northern dot blot), perioptic mesenchyme (E11), cornea (E11), skeleton (E14.5), brain meninges (E14.5), and cartilage (E14.5) at relatively early stages. Most evidence of type I collagen function is coupled to the latter stages of skeletal development, thus bypassing the major events of axis formation, tissue differentiation, and mesenchlymal-epithial interactions, for example, that are more symbolic of morphogens and growth factors. Members of the integrin cell surface receptor family of molecules mediate cell adhesion to ECM proteins such as collagen (mainly to type IV basement membrane collagen that forms into a polygonal meshwork), fibronectin, and laminin implicated in wound healing and inflammatory responses (e.g. Crohn disease, ulcerative colitis) in connective tissues. There is some evidence for protein-protein interactions between leukocyte-associated integrins and the interstitial matrix in promoting the migration and/or activation of extravasated leukocytes (e.g., T cells and monocytes) within the perivascular compartment, an ECM-rich environment. This region is surmised to be an important location where certain human leukocytes undergo differentiation (e.g. monocytes) and activation (neutrophils, monocytes, lymphocytes) upon extravascular migration. The von Willebrand factor (vWF), type C motif is found in various plasma proteins like complement factors, the integrins, collagen types, and other extracellular proteins. Thus, the majority of vWF-containing proteins are extracellular and a common feature appears to be involvement in multi protein complexes participating in numerous biological events (e.g. cell adhesion, migration, homing, pattern formation, and signal transduction). Three organs (lung, heart and bone) of 5 AGA002 mutant mice (age 2x 10 days and 3x 11 days) were analysed by cDNA microarray technology. As reference five mice, 11 days old were used 50% of the chip hybridisations are dye swap experiments.

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Phenotypic spectrum and molecular basis in a Chinese cohort of osteogenesis imperfecta with mutations in type I collagen

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