Cell differentiation and matrix organization are differentially affected during bone formation in osteogenesis imperfecta zebrafish models with different genetic defects impacting collagen type I structure

Dimethyloxalylglycine regulates osteogenesis of dental pulp stem cells through PI3K/AKT signaling pathways

BACKGROUND

Dental pulp mesenchymal stem cells (DPSCs) are typically cultivated in vitro under normoxic conditions, which may adversely affect their biological functions during research and treatment. Dimethyloxalylglycine (DMOG) is a small-molecule drug that has demonstrated impressive therapeutic outcomes in conditions such as osteoporosis.

OBJECTIVE

However, the influence of DMOG on the osteogenesis associated with DPSCs remains inadequately understood. We propose that DMOG may significantly impact the biological functions related to osteogenesis in DPSCs when exposed to normoxic conditions.

MATERIALS AND METHODS

DPSCs were obtained through tissue block enzyme digestion. Tube formation experiment was conducted, quantitative polymerase chain reaction (qPCR) was employed to assess the angiogenic activity of DPSCs. Additionally, alkaline phosphatase (ALP) activity tests, alizarin red staining (ARS), qPCR and western blotting (WB) assays were utilized to evaluate the osteogenic activity of DPSCs. The proposed mechanism was confirmed through repeated experiments.

RESULTS

DMOG significantly influences the osteogenic functions of DPSCs under normoxic conditions. Our findings further confirm that DMOG stimulates the phosphatidylinositol 3-kinase (PI3K)/Protein kinase B (AKT) signaling pathway in DPSCs via phosphorylation. Inhibition of this pathway can partially impede the biological effects of DPSCs related to osteogenesis and angiogenesis.

CONCLUSION

We have addressed the gap in understanding the effect of DMOG on the osteogenesis of DPSCs. Unlike previous studies that examined the regulation of osteogenesis in stem cells by DMOG, our findings suggest that a lower dose of DMOG is sufficient to enhance the osteogenesis of DPSCs. This could represent a promising strategy for cellular therapy in bone regeneration.

Prevotella copri-mediated caffeine metabolism involves ferroptosis of osteoblasts in osteoarthritis

There is a positive causality between coffee consumption and osteoarthritis (OA); however, whether gut microbiota is involved needs to be discussed. Here, we observed that in caffeine consumers, fecal Prevotella copri abundance was positively correlated with subchondral bone mass, serum caffeine concentration was negatively correlated with bone mass, and fecal P. copri was negatively correlated with serum caffeine. In the OA model, caffeine intake aggravated articular cartilage destruction, bone mass loss, and intestinal barrier damage; on the contrary, paraxanthine intake reversed the above lesions. Importantly, after the intestinal P. copri supplement, caffeine-induced lesions in OA mice were effectively alleviated. Mechanically, P. copri has the potential to metabolize caffeine into paraxanthine, and this effect could alleviate the ferroptosis of osteoblast in the OA model. This study screened out that P. copri, an endogenous bacteria, has the ability to metabolize caffeine and revealed its effects on OA progression.IMPORTANCEThere is positive causality between coffee consumption and osteoarthritis (OA). Caffeine exposure is responsible for the reduction of bone mass and restrained osteoblast function. Prevotella copri abundance is exhausted in gut and positively correlated with subchondral bone mass in coffee consumption patients with OA. Supplement of intestinal P. copri alleviates caffeine-induced subchondral bone loss. P. copri has the potential to metabolize caffeine into paraxanthine, and this effect alleviates ferroptosis of osteoblast. Our study illustrated that intestinal P. copri possibly serves as a novel promising treatment for coffee consumers with OA.

Exosomal non-coding RNAs in the regulation of bone metabolism homeostasis: Molecular mechanism and therapeutic potential

Bone metabolism is a dynamic balance between bone formation and absorption regulated by osteoblasts/osteoclasts. Bone metabolic disorders can lead to metabolic bone disease. Osteoporosis (OP), osteoarthritis (OA) and femoral head necrosis (ONFH) are common metabolic bone diseases. At present, the treatment of metabolic bone disease is still mainly to relieve pain and improve joint function. However, surgical treatment does not apply to the vast majority of high-risk groups, including postmenopausal women, patients with diabetes, cirrhosis, etc. Exosomes (Exos) are nanoscale membrane vesicles that are released by almost all cells. Exos are rich in a variety of bioactive substances, such as non-coding RNAs, nucleic acids, proteins and lipids. In view of the structure of Exos, it can protect the biologically active molecules can be smoothly delivered to the target cells and involved in the regulation of cell function. In this review, we focus on the regulation mechanism and function of bone homeostasis mediated by exosomal ncRNAs (Exos-ncRNAs), including macrophage polarization, autophagy, angiogenesis, signal transduction and competing endogenous RNA (ceRNA). We summarized the therapeutic strategies and potential drugs of Exos-ncRNAs in metabolic bone disease. Moreover, we discussed the shortcomings and potential research directions of Exos as carrier to deliver ncRNAs to play a role.

Bone cell differentiation and mineralization in wild-type and osteogenesis imperfecta zebrafish are compromised by per- and poly-fluoroalkyl substances (PFAS)

Perfluorinated compounds (PFAS) are well recognized toxic pollutants for humans, but if their effect is equally harmful for healthy and fragile people is unknown. Addressing this question represents a need for ensuring global health and wellbeing to all individuals in a world facing the progressive increase of aging and aging related diseases. This study aimed to evaluate the impact of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) exposure on development and skeletal phenotype using the osteogenesis imperfecta (OI) zebrafish model Chihuahua (Chi/+), carrying a dominant glycine substitution in the α1 chain of collagen I and their wild-type (WT) littermates. To this purpose Chi/+ and WT zebrafish expressing the green fluorescent protein under the early osteoblast marker osterix were exposed from 1 to 6 days post fertilization to 0.36, 1.5 and 3.0 mg/L PFOS, 0.005 and 0.5 mg/L PFOA and 0.01, 0.48 and 16.0 mg/L PFHxA, and their development and skeletal phenotype investigated. Morphometric measurements, confocal microscopy evaluation of operculum area delimited by the fluorescent preosteoblasts and mineral deposition analysis following alizarin red staining were employed. PFOS and the highest concentration of PFHxA significantly impaired standard length in both genotypes. Osteoblast differentiation was significantly compromised by PFOS and by PFOA only in Chi/+. Limited to WT exposed to PFOA a reduced mineralization was also observed. No effect was detected after PFHxA exposure. Apoptosis was only activated by PFOA, specifically in Chi/+ mutant operculum osteoblasts. Interestingly, an altered lipid distribution in both WT and mutant fish was revealed after exposure to both pollutants. In conclusion, our data demonstrate that PFAS impair operculum development mainly compromising cell differentiation in mutant fish whereas alter lipid hepatic distribution in both genotypes with a more severe effect on Chi/+ preosteoblast survival. These results represent a first warning sign of the negative impact of PFAS exposure in presence of genetically determined skeletal fragility.

Crispant analysis in zebrafish as a tool for rapid functional screening of disease-causing genes for bone fragility

Heritable fragile bone disorders (FBDs), ranging from multifactorial to rare monogenic conditions, are characterized by an elevated fracture risk. Validating causative genes and understanding their mechanisms remain challenging. We assessed a semi-high throughput zebrafish screening platform for rapid in vivo functional testing of candidate FBD genes. Six genes linked to severe recessive osteogenesis imperfecta (OI) and four associated with bone mineral density (BMD) from genome-wide association studies were analyzed. Using CRISPR/Cas9-based crispant screening in F0 mosaic founder zebrafish, Next-generation sequencing confirmed high indel efficiency (mean 88%), mimicking stable knock-out models. Skeletal phenotyping at 7, 14, and 90 days post-fertilization (dpf) using microscopy, Alizarin Red S staining, and microCT was performed. Larval crispants showed variable osteoblast and mineralization phenotypes, while adult crispants displayed consistent skeletal defects, including malformed neural and haemal arches, vertebral fractures and fusions, and altered bone volume and density. In addition, aldh7a1 and mbtps2 crispants experienced increased mortality due to severe skeletal deformities. RT-qPCR revealed differential expression of osteogenic markers bglap and col1a1a, highlighting their biomarker potential. Our results establish zebrafish crispant screening as a robust tool for FBD gene validation, combining skeletal and molecular analyses across developmental stages to uncover novel insights into gene functions in bone biology.

A novel chemical chaperone ameliorates osteoblast homeostasis and extracellular matrix in osteogenesis imperfecta

AIMS

Osteogenesis imperfecta (OI) is a collagen I-related heritable family of skeletal diseases associated to extreme bone fragility and deformity. Its classical forms are caused by dominant mutations in COL1A1 and COL1A2, which encode for the protein α chains, and are characterized by impairment in collagen I structure, folding, and secretion. Mutant collagen I assembles in an altered extracellular matrix affecting mineralization and bone properties and partially accumulating inside the cells, leading to impaired trafficking and cellular stress. Recently, the chemical chaperone 4-phenylbutyrate (4-PBA) has been proposed as an innovative drug for OI based on its ability to restore intracellular homeostasis, stimulate secretion, and ameliorate collagen-producing cell functions, positively affecting bone properties. However, the limited half-life of the molecule represents a serious hurdle for its use.

MATERIALS AND METHODS

To efficiently target cellular stress as OI treatment, two new compounds were designed by molecular modelling based on the 4-PBA structure to increase its stability and its ability to implement protein secretion. The short butyryl fatty acid chain of 4-PBA was substituted with a nitro functional group or with a glycine, respectively. The latter, N-benzyl glycine (N-BG), showed the best docking score, less toxicity, and higher stability than 4-PBA.

KEY FINDINGS

N-BG improved extracellular matrix quality and mineral content together with ameliorating OI cells' homeostasis by increasing ER-associated degradation pathway, reducing apoptosis, and stimulating protein secretion, thus facilitating intracellular clearance from accumulated misfolded proteins.

SIGNIFICANCE

In conclusion, N-BG represents a novel potential available compound to target altered homeostasis in OI with the aim to ameliorate the disease phenotype.

Modeling Musculoskeletal Disorders in Zebrafish: Advancements in Muscle and Bone Research

Zebrafish (Danio rerio) have emerged as a valuable model organism for investigating musculoskeletal development and the pathophysiology of associated diseases. Key genes and biological processes in zebrafish that closely mirror those in humans, rapid development, and transparent embryos make zebrafish ideal for the in vivo studies of bone and muscle formation, as well as the molecular mechanisms underlying musculoskeletal disorders. This review focuses on the utility of zebrafish in modeling various musculoskeletal conditions, with an emphasis on bone diseases such as osteoporosis and osteogenesis imperfecta, as well as muscle disorders like Duchenne muscular dystrophy. These models have provided significant insights into the molecular pathways involved in these diseases, helping to identify the key genetic and biochemical factors that contribute to their progression. These findings have also advanced our understanding of disease mechanisms and facilitated the development of potential therapeutic strategies for musculoskeletal disorders.

Zebrafish Models for Skeletal and Extraskeletal Osteogenesis Imperfecta Features: Unveiling Pathophysiology and Paving the Way for Drug Discovery

In the last decades, the easy genetic manipulation, the external fertilization, the high percentage of homology with human genes and the reduced husbandry costs compared to rodents, made zebrafish a valid model for studying human diseases and for developing new therapeutical strategies. Since zebrafish shares with mammals the same bone cells and ossification types, it became widely used to dissect mechanisms and possible new therapeutic approaches in the field of common and rare bone diseases, such as osteoporosis and osteogenesis imperfecta (OI), respectively. OI is a heritable skeletal disorder caused by defects in gene encoding collagen I or proteins/enzymes necessary for collagen I synthesis and secretion. Nevertheless, OI patients can be also characterized by extraskeletal manifestations such as dentinogenesis imperfecta, muscle weakness, cardiac valve and pulmonary abnormalities and skin laxity. In this review, we provide an overview of the available zebrafish models for both dominant and recessive forms of OI. An updated description of all the main similarities and differences between zebrafish and mammal skeleton, muscle, heart and skin, will be also discussed. Finally, a list of high- and low-throughput techniques available to exploit both larvae and adult OI zebrafish models as unique tools for the discovery of new therapeutic approaches will be presented.

Correlation of serum DKK1 level with skeletal phenotype in children with osteogenesis imperfecta

PURPOSE

We aim to detect serum DKK1 level of pediatric patients with OI and to analyze its relationship with the genotype and phenotype of OI patients.

METHODS

A cohort of pediatric OI patients and age-matched healthy children were enrolled. Serum levels of DKK1 and bone turnover biomarkers were measured by enzyme-linked immunosorbent assay. Bone mineral density (BMD) was measured by Dual-energy X-ray absorptiometry. Pathogenic mutations of OI were detected by next-generation sequencing and confirmed by Sanger sequencing.

RESULTS

A total of 62 OI children with mean age of 9.50 (4.86, 12.00) years and 29 healthy children were included in this study. The serum DKK1 concentration in OI children was significantly higher than that in healthy children [5.20 (4.54, 6.32) and 4.08 (3.59, 4.92) ng/mL, P < 0.001]. The serum DKK1 concentration in OI children was negatively correlated with height (r = - 0.282), height Z score (r = - 0.292), ALP concentration (r = - 0.304), lumbar BMD (r = - 0.276), BMD Z score of the lumbar spine and femoral neck (r = - 0.32; r = - 0.27) (all P < 0.05). No significant difference in serum DKK1 concentration was found between OI patients with and without vertebral compression fractures. In patients with spinal deformity (22/62), serum DKK1 concentration was positively correlated with SDI (r = 0.480, P < 0.05). No significant correlation was observed between serum DKK1 concentration and the annual incidence of peripheral fractures, genotype and types of collagen changes in OI children.

CONCLUSION

The serum DKK1 level was not only significantly elevated in OI children, but also closely correlated to their skeletal phenotype, suggesting that DKK1 may become a new biomarker and a potential therapeutic target of OI.

New Perspectives of Therapies in Osteogenesis Imperfecta-A Literature Review

(1) Background: Osteogenesis imperfecta (OI) is a rare skeletal dysplasia characterized as a heterogeneous disorder group with well-defined phenotypic and genetic features that share uncommon bone fragility. The current treatment options, medical and orthopedic, are limited and not efficient enough to improve the low bone density, bone fragility, growth, and mobility of the affected individuals, creating the need for alternative therapeutic agents. (2) Methods: We searched the medical database to find papers regarding treatments for OI other than conventional ones. We included 45 publications. (3) Results: In reviewing the literature, eight new potential therapies for OI were identified, proving promising results in cells and animal models or in human practice, but further research is still needed. Bone marrow transplantation is a promising therapy in mice, adults, and children, decreasing the fracture rate with a beneficial effect on structural bone proprieties. Anti-RANKL antibodies generated controversial results related to the therapy schedule, from no change in the fracture rate to improvement in the bone mineral density resorption markers and bone formation, but with adverse effects related to hypercalcemia. Sclerostin inhibitors in murine models demonstrated an increase in the bone formation rate and trabecular cortical bone mass, and a few human studies showed an increase in biomarkers and BMD and the downregulation of resorption markers. Recombinant human parathormone and TGF-β generated good results in human studies by increasing BMD, depending on the type of OI. Gene therapy, 4-phenylbutiric acid, and inhibition of eIF2α phosphatase enzymes have only been studied in cell cultures and animal models, with promising results. (4) Conclusions: This paper focuses on eight potential therapies for OI, but there is not yet enough data for a new, generally accepted treatment. Most of them showed promising results, but further research is needed, especially in the pediatric field.

Bone Material Properties in Bone Diseases Affecting Children

PURPOSE OF REVIEW

Metabolic and genetic bone disorders affect not only bone mass but often also the bone material, including degree of mineralization, matrix organization, and lacunar porosity. The quality of juvenile bone is moreover highly influenced by skeletal growth. This review aims to provide a compact summary of the present knowledge on the complex interplay between bone modeling and remodeling during skeletal growth and to alert the reader to the complexity of bone tissue characteristics in children with bone disorders.

RECENT FINDINGS

We describe cellular events together with the characteristics of the different tissues and organic matrix organization (cartilage, woven and lamellar bone) occurring during linear growth. Subsequently, we present typical alterations thereof in disorders leading to over-mineralized bone matrix compared to those associated with low or normal mineral content based on bone biopsy studies. Growth spurts or growth retardation might amplify or mask disease-related alterations in bone material, which makes the interpretation of bone tissue findings in children complex and challenging.