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International Journal of Molecular... Sep 2023Osteopetrosis is a rare inherited disease caused by osteoclast failure, resulting in increasing bone density in humans. Patients with osteopetrosis possess several...
Osteopetrosis is a rare inherited disease caused by osteoclast failure, resulting in increasing bone density in humans. Patients with osteopetrosis possess several dental and cranial complications. Since carbonic anhydrase II (CA-II) deficiency is a major cause of osteopetrosis, CA-II activators might be an attractive potential treatment option for osteopetrosis patients. We conducted comprehensive label-free quantitative proteomics analysis on Fluconazole-treated Dental Pulp Mesenchymal Stem/Stromal Cells from CA-II-Deficient Osteopetrosis Patients. We identified 251 distinct differentially expressed proteins between healthy subjects, as well as untreated and azole-treated derived cells from osteopetrosis patients. Twenty-six (26) of these proteins were closely associated with osteogenesis and osteopetrosis disease. Among them are ATP1A2, CPOX, Ap2 alpha, RAP1B and some members of the RAB protein family. Others include AnnexinA1, 5, PYGL, OSTF1 and PGAM4, all interacting with OSTM1 in the catalytic reactions of HCO3 and the Cl- channel via CAII regulation. In addition, the pro-inflammatory/osteoclast regulatory proteins RACK1, MTSE, STING1, S100A13, ECE1 and TRIM10 are involved. We have identified proteins involved in osteogenic and immune metabolic pathways, including ERK 1/2, phosphatase and ATPase, which opens the door for some CA activators to be used as an alternative drug therapy for osteopetrosis patients. These findings propose that fluconazole might be a potential treatment agent for CAII- deficient OP patients. Altogether, our findings provide a basis for further work to elucidate the clinical utility of azole, a CA activator, as a therapeutic for OP.
Topics: Humans; Fluconazole; Osteogenesis; Dental Pulp; Osteopetrosis; Azoles; Metabolic Networks and Pathways; Mesenchymal Stem Cells; rap GTP-Binding Proteins
PubMed: 37762144
DOI: 10.3390/ijms241813841 -
JBMR Plus May 2024Mutations in cause osteopetrosis in humans and rats. The germline and osteoclast conditional deletions of gene in mice lead to defective osteoclast bone resorption and...
Mutations in cause osteopetrosis in humans and rats. The germline and osteoclast conditional deletions of gene in mice lead to defective osteoclast bone resorption and increased trabecular bone mass without overt abnormalities in other organs. As an adaptor protein, pleckstrin homology and RUN domain containing M1 (PLEKHM1) interacts with the key lysosome regulator small GTPase RAB7 via its C-terminal RUBICON homologous (RH) domain. In this study, we have conducted a structural-functional study of the PLEKHM1 RH domain and RAB7 interaction in osteoclasts in vitro. The single mutations of the key residues in the Plekhm1 RH predicted from the crystal structure of the RUBICON RH domain and RAB7 interface failed to disrupt the Plekhm1-Rab7 binding, lysosome trafficking, and bone resorption. The compound alanine mutations at Y949-R954 and L1011-I1018 regions decreased Plekhm1 protein stability and Rab7-binding, respectively, thereby attenuated lysosome trafficking and bone resorption in osteoclasts. In contrast, the compound alanine mutations at R1060-Q1068 region were dispensable for Rab7-binding and Plekhm1 function in osteoclasts. These results indicate that the regions spanning Y949-R954 and L1011-I1018 of Plekhm1 RH domain are functionally important for Plekhm1 in osteoclasts and offer the therapeutic targets for blocking bone resorption in treatment of osteoporosis and other metabolic bone diseases.
PubMed: 38586475
DOI: 10.1093/jbmrpl/ziae034 -
The Journal of Physiology Dec 2023ClC-6 and ClC-7 are closely related, intracellular Cl /H antiporters belonging to the CLC family of channels and transporters. They localize to acidic late endosomes and...
ClC-6 and ClC-7 are closely related, intracellular Cl /H antiporters belonging to the CLC family of channels and transporters. They localize to acidic late endosomes and lysosomes and probably function in ionic homeostasis of these contiguous compartments. ClC-7 transport function requires association with the accessory protein Ostm1, whereas ClC-6 transport does not. To elucidate their roles in endo-lysosomes, we measured Cl - and pH-dependences of over-expressed wild-type ClC-6 and ClC-7, as well as disease-associated mutants, using high-resolution recording protocols. Lowering extracellular Cl (corresponding to luminal Cl in endo-lysosomes) reduced ClC-6 currents, whereas it increased transport activity of ClC-7/Ostm1. Low extracellular Cl activated ClC-7/Ostm 1 under acidic extracellular conditions, as well as under conditions of low intracellular chloride. Activation is conserved in ClC-7 , a variant displaying disrupted PI(3,5)P inhibition. Detailed biophysical analysis of disease-associated ClC-6 and ClC-7 gain-of-function (GoF) variants, ClC-6 and ClC-7 , and the ClC-7 and ClC-6 correlates, identified additional functional nuances distinguishing ClC-6 and ClC-7. ClC-7 recapitulated GoF produced by ClC-6 . ClC-6 displayed transport activation qualitatively similar to ClC-7 , although current density did not differ from that of wild-type ClC-6. Finally, rClC-7 , homologous to hClC-7 , an osteopetrosis variant with fast gating kinetics, appeared indifferent to extracellular Cl , identifying altered Cl sensitivity as a plausible mechanism underlying disease. Collectively, the present studies underscore the distinct roles of ClC-6 and ClC-7 within the context of their respective localization to late endosomes and lysosomes. In particular, we suggest the atypical inhibition of ClC-7 by luminal Cl serves to limit excessive intraluminal Cl accumulation. KEY POINTS: ClC-6 and ClC-7 are late endosomal and lysosomal 2 Cl /1 H exchangers, respectively. When targeted to the plasma membrane, both activate slowly at positive voltages. ClC-6 activity is decreased in low extracellular (i.e. luminal) chloride, whereas ClC-7 is activated by low luminal chloride, even at acidic pH. The functional gain-of-function phenotypes of the ClC-6 and ClC-7 disease mutations ClC-6 and ClC-7 are maintained when introduced in their respective homologues, ClC-7 and ClC-6 , with all mutations retaining chloride dependence of the respective wild type (WT). An osteopetrosis mutation of ClC-7 displaying fast gating kinetics (R762Q) was less sensitive to extracellular chloride compared to WT. The opposing substrate dependences of ClC-6 and ClC-7 Cl / H exchangers point to non-overlapping physiological functions, leading us to propose that inhibition of ClC-7 by luminal chloride and protons serves to prevent osmotic stress imposed by hyper-accumulation of chloride.
Topics: Humans; Chloride Channels; Chlorides; Homeostasis; Lysosomes; Osteopetrosis; Protons
PubMed: 37937509
DOI: 10.1113/JP285431 -
Journal of Clinical and Translational... Aug 2023We report a patient with refractory ascites because of portal hypertension caused by hemochromatosis secondary to osteopetrosis. To our knowledge, this is the first...
We report a patient with refractory ascites because of portal hypertension caused by hemochromatosis secondary to osteopetrosis. To our knowledge, this is the first well-documented case of this association. A 46-year-old male patient who was repeatedly infused with red blood cells for anemia secondary to osteopetrosis suffered from refractory ascites. The serum-ascites albumin gradient was 29.9 g/L. Abdominal computed tomography (CT) showed a large amount of ascites, hepatomegaly, and splenomegaly. Bone marrow biopsy showed a small bone marrow cavity with no hematopoietic tissue. A peripheral blood smear showed tear drop red blood cells and metarubricytes. Serum ferritin was 8,855.0 ng/mL. Therefore, we considered that the ascites resulted from portal hypertension caused by hemochromatosis secondary to osteopetrosis. We simultaneously performed the transjungular intrahepatic portal-systemic shunt (TIPS) and obtained a transjungular liver biopsy. The portal pressure gradient before TIPS was 28 mmHg, and iron staining was strongly positive on liver biopsy, which confirmed our diagnosis. After TIPS, both abdominal distention and ascites gradually resolved, and no recurrence as observed after the 12-month postoperative follow-up was observed. This case indicated that regular monitoring of iron load is important for patients with osteopetrosis. TIPS is safe and effective for portal hypertension complications due to osteopetrosis.
PubMed: 37408812
DOI: 10.14218/JCTH.2022.00418 -
Scientific Reports Nov 2023Osteoclasts uniquely resorb calcified bone matrices. To exert their function, mature osteoclasts maintain the cellular polarity and directional vesicle trafficking to...
Osteoclasts uniquely resorb calcified bone matrices. To exert their function, mature osteoclasts maintain the cellular polarity and directional vesicle trafficking to and from the resorbing bone surface. However, the regulatory mechanisms and pathophysiological relevance of these processes remain largely unexplored. Bone histomorphometric analyses in Ccr5-deficient mice showed abnormalities in the morphology and functional phenotype of their osteoclasts, compared to wild type mice. We observed disorganized clustering of nuclei, as well as centrosomes that organize the microtubule network, which was concomitant with impaired cathepsin K secretion in cultured Ccr5-deficient osteoclasts. Intriguingly, forced expression of constitutively active Rho or Rac restored these cytoskeletal phenotypes with recovery of cathepsin K secretion. Furthermore, a gene-disease enrichment analysis identified that PLEKHM1, a responsible gene for osteopetrosis, which regulates lysosomal trafficking in osteoclasts, was regulated by CCR5. These experimental results highlighted that CCR5-mediated signaling served as an intracellular organizer for centrosome clustering in osteoclasts, which was involved in the pathophysiology of bone metabolism.
Topics: Animals; Mice; Bone and Bones; Bone Matrix; Bone Resorption; Cathepsin K; Centrosome; Osteoclasts; Receptors, CCR5
PubMed: 38012303
DOI: 10.1038/s41598-023-48140-2 -
Surgical Neurology International 2023Osteopetrosis is a rare disease characterized by systemic osteosclerosis and hematopoietic disturbances. Childhood-onset cases are often accompanied by hydrocephalus and...
BACKGROUND
Osteopetrosis is a rare disease characterized by systemic osteosclerosis and hematopoietic disturbances. Childhood-onset cases are often accompanied by hydrocephalus and craniosynostosis; however, there have been no established treatments. We performed cranial distraction in a child with osteopetrosis who presented with craniosynostosis and intracranial hypertension.
CASE DESCRIPTION
The patient was a 4-year-1-month-old boy. His pregnancy and birth were normal, but at 4 months of age, he was diagnosed with osteopetrosis based on generalized osteosclerosis and family history. A computed tomography scan of the head revealed early sagittal suture fusion and ventricular enlargement. A ventriculoperitoneal shunt was placed for intracranial hypertension; however, slit ventricle syndrome ensued and pansynostosis developed. To improve uncontrolled high intracranial pressure, cranial distraction was performed for intracranial volume expansion. No perioperative hemorrhagic or infectious complications were observed. After the start of distraction, the intracranial pressure gradually decreased, and clinical findings such as disturbance of consciousness and bradycardia disappeared. Bone regeneration in the defect site was good, and the extension device was removed 6 months after the operation.
CONCLUSION
For osteopetrosis with poorly controlled intracranial hypertension, cranial distraction was considered to be an effective treatment.
PubMed: 37941624
DOI: 10.25259/SNI_623_2023 -
Zhonghua Er Ke Za Zhi = Chinese Journal... Nov 2023To investigate the clinical presentation and genetic characteristics of malignant infantile osteopetrosis. This was a retrospective case study. Thirty-seven children...
To investigate the clinical presentation and genetic characteristics of malignant infantile osteopetrosis. This was a retrospective case study. Thirty-seven children with malignant infantile osteopetrosis admitted into Beijing Children's Hospital from January 2013 to September 2022 were enrolled in this study. According to the gene mutations, the patients were divided into the CLCN7 group and the TCIRG1 group. Clinical characteristics, laboratory tests, and prognosis were compared between two groups. Wilcoxon test or Fisher exact test were used in inter-group comparison. The survival rate was estimated with the Kaplan-Meier method and the Log-Rank test was used to compare the difference in survival between groups. Among the 37 cases, there were 22 males and 15 females. The age of diagnosis was 0.5 (0.2, 1.0) year. There were 13 patients (35%) and 24 patients (65%) with mutations in CLCN7 and TCIRGI gene respectively. Patients in the CLCN7 group had an older age of diagnosis than those in the TCIRGI group (1.2 (0.4, 3.6) 0.4 (0.2, 0.6) years, =-2.60, =0.008). The levels of serum phosphorus (1.7 (1.3, 1.8) 1.1 (0.8, 1.6) mmol/L, =-2.59, =0.010), creatine kinase isoenzyme (CK-MB) (457 (143, 610) 56 (37, 82) U/L, =-3.38, =0.001) and the level of neutrophils (14.0 (9.9, 18.1) 9.2 (6.7, 11.1) ×10/L, =-2.07, =0.039) at diagnosis were higher in the CLCN7 group than that in the TCIRG1 group. However, the level of D-dimer in the CLCN7 group was lower than that in the TCIRGI group (2.7 (1.0, 3.1) 6.3 (2.5, 9.7) μg/L, =2.83, =0.005). After hematopoietic stem cell transplantation, there was no significant difference in 5-year overall survival rate between the two groups (92.3%±7.4% 83.3%±7.6%, ²=0.56, =0.456). TCIRGI gene mutations are more common in children with osteopetrosis. Children with TCIRGI gene mutations have younger age, lower levels of phosphorus, CK-MB, and neutrophils and higher level of D-dimer at the onset. After hematopoietic stem cell transplantation, patients with CLCN7 or TCIRGI gene mutations have similar prognosis.
Topics: Child; Male; Female; Humans; Osteopetrosis; Retrospective Studies; Prognosis; Genes, Recessive; Phosphorus; Chloride Channels; Vacuolar Proton-Translocating ATPases
PubMed: 37899344
DOI: 10.3760/cma.j.cn112140-20230822-00124 -
Paediatrics and International Child... Apr 2024Osteopetrosis encompasses rare inherited metabolic bone disorders with defect in the osteoclast activity. Severe forms of presentation such as malignant infantile...
Osteopetrosis encompasses rare inherited metabolic bone disorders with defect in the osteoclast activity. Severe forms of presentation such as malignant infantile osteopetrosis are seen in infants and milder forms in older children. The clinical presentation includes failure to thrive, severe pallor, optic atrophy and hepatosplenomegaly. The disorder is characterised by dense bone on radiography, hence the name marble bone disease. A 10-month-old boy who presented with developmental delay, failure to thrive, nystagmus (which the mother described as wandering eye movements), splenomegaly of 16 cm and hepatomegaly of 8 cm. Investigations demonstrated severe anaemia (5.7 g/dL) and thrombocytopenia (34 x 109/L). Radiological signs which help in the diagnosis include diffuse sclerosis, bone within bone appearance, sandwich vertebrae and Erlenmeyer flask deformity. Plain radiography is an easily available and cost effective tool which can aid in the diagnosis of osteopetrosis.
PubMed: 38577960
DOI: 10.1080/20469047.2024.2335423 -
JBMR Plus May 2024The purpose of this study was to identify new independent significant SNPs associated with osteoporosis using data from the Taiwan Biobank (TWBB).
PURPOSE
The purpose of this study was to identify new independent significant SNPs associated with osteoporosis using data from the Taiwan Biobank (TWBB).
MATERIAL AND METHODS
The dataset was divided into discovery (60%) and replication (40%) subsets. Following data quality control, genome-wide association study (GWAS) analysis was performed, adjusting for sex, age, and the top 5 principal components, employing the Scalable and Accurate Implementation of the Generalized mixed model approach. This was followed by a meta-analysis of TWBB1 and TWBB2. The Functional Mapping and Annotation (FUMA) platform was used to identify osteoporosis-associated loci. Manhattan and quantile-quantile plots were generated using the FUMA platform to visualize the results. Independent significant SNPs were selected based on genome-wide significance ( < 5 × 10) and independence from each other (r < 0.6) within a 1 Mb window. Positional, eQTL(expression quantitative trait locus), and Chromatin interaction mapping were used to map SNPs to genes.
RESULTS
A total of 29 084 individuals (3154 osteoporosis cases and 25 930 controls) were used for GWAS analysis (TWBB1 data), and 18 918 individuals (1917 cases and 17 001 controls) were utilized for replication studies (TWBB2 data). We identified a new independent significant SNP for osteoporosis in TWBB1, with the lead SNP rs76140829 (minor allele frequency = 0.055, -value = 1.15 × 10). Replication of the association was performed in TWBB2, yielding a -value of 6.56 × 10. The meta-analysis of TWBB1 and TWBB2 data demonstrated a highly significant association for SNP rs76140829 (-value = 7.52 × 10). In the positional mapping of rs76140829, 6 genes (, , , , , ) were identified through chromatin interaction mapping in mesenchymal stem cells.
CONCLUSIONS
Our GWAS analysis using the Taiwan Biobank dataset unveils rs76140829 in the gene as a key risk variant associated with osteoporosis. This finding expands our understanding of the genetic basis of osteoporosis and highlights the potential regulatory role of this SNP in mesenchymal stem cells.
PubMed: 38655459
DOI: 10.1093/jbmrpl/ziae028 -
Orphanet Journal of Rare Diseases Sep 2023Skeletal dysplasias are a diverse group of rare disorders in the chondro-osseous tissue that can have a significant impact on patient's functionality. The worldwide...
BACKGROUND
Skeletal dysplasias are a diverse group of rare disorders in the chondro-osseous tissue that can have a significant impact on patient's functionality. The worldwide prevalence of skeletal dysplasias at birth is approximately 1:5000 births. To date, disease burden and trends of skeletal dysplasias in the Sri Lankan population have not been described in any epidemiological study. Our aim was to evaluate the burden and the current trends in hospital admissions for skeletal dysplasias in the Sri Lankan population. A retrospective evaluation of hospital admissions for skeletal dysplasia during 2017-2020 was performed using population-based data from the eIMMR database which covers government hospitals in the entire country. The trends in hospital admissions for skeletal dysplasias by calendar year, age, and types of skeletal dysplasia were described using appropriate summary statistics.
RESULTS
Respective crude admission rates of skeletal dysplasias in the years 2017, 2018, 2019 and 2020 were 5.2, 8.1, 8.0, and 6.5 per million population. A female predominance (1.4:1) was noted during the studied period. Of all reported cases the majority (n = 268; 44.2%) were children less than 4 years. Each year, 0-4 years age group represented 40-47% of the total hospital admissions. More than half of the cases were reported from Colombo (28.1%) and Kandy (25.4%) districts combined. 60% of cases were diagnosed as osteogenesis imperfecta (OI). Rising trends were observed in the hospital admissions for osteogenesis imperfecta, achondroplasia and osteopetrosis, while other skeletal dysplasia types collectively showed a relatively stable trend.
CONCLUSION
This preliminary study revealed a female predominance of skeletal dysplasias and a relatively high admission rate of osteogenesis imperfecta in the Sri Lankan population. A distinct trend was not visible in the studied years probably due to the impact on hospital services due to COVID- Pandemic. Future research on the healthcare burden on families affected by skeletal dysplasia is required to better understand the overall cost of care and identify therapies that reduce admission rates. This study highlights the value of analysing population-based data on rare diseases to improve healthcare in low-resource countries.
Topics: Infant, Newborn; Child; Female; Humans; Male; Osteogenesis Imperfecta; Sri Lanka; Retrospective Studies; COVID-19; Osteochondrodysplasias; Hospitals
PubMed: 37684696
DOI: 10.1186/s13023-023-02884-2