Targeting cellular stress in vitro improves osteoblast homeostasis, matrix collagen content and mineralization in two murine models of osteogenesis imperfecta

Extracellular matrix of ameloblastoma-derived negatively regulates osteogenic differentiation

OBJECTIVE

To investigate the effects of key pathogenic genes involved in the development of jaw ameloblastoma (AB) and its associated extracellular matrix (ECM) on osteogenic differentiation in order to provide a theoretical foundation for future research into bone aggressiveness of AB.

METHODS

The essential genes were identified by five AB patients for whole-exome sequencing and the microarray datasets GES38494 and GES132472. Moreover, the expression of key genes and their encoded proteins in AB tissues was explored. In addition, AB-derived the decellularized ECM (ABdECM) tissues were generated by the decellularization technique. Furthermore, the osteogenic development of periodontal ligament stem cells (PDLSCs) was mimicked by simulating the effects of the AB tumor microenvironment (TME).

RESULTS

The AB essential genes including COL1A2, COL4A2, FBN1, and HPSE were discovered. Among them, the expression of HPSE was down-regulated, while that of COL1A2, COL4A2, and FBN1 was noticeably upregulated in AB compared with normal gingival tissues of the jaws. In vitro osteogenic differentiation of PDLSCs was suppressed by the ABdECM.

CONCLUSIONS

Abnormal ECM proteins encoded by COL4A2, COL1A2, FBN1, and HPSE genes can cause disturbance in the ECM environment of AB and promote bone resorption.

Altered Osteoblast Metabolism with Aging Results in Lipid Accumulation and Oxidative Stress Mediated Bone Loss

Cellular aging is associated with dysfunction of numerous tissues affecting multiple organ systems. A striking example of this is related to age-related bone loss, or osteoporosis, increasing fracture incidence. Interestingly, the two compartments of bone, cortical and cancellous or trabecular, rely on different mechanisms for development and maintenance during 'normal' aging. At a cellular level, the aging process disturbs a multitude of intracellular pathways. In particular, alterations in cellular metabolic functions thereby impacting cellular bioenergetics have been implicated in multiple tissues. Therefore, this study aimed to characterize how metabolic processes were altered in bone forming osteoblasts in aged mice compared to young mice. Metabolic flux analyses demonstrated both stromal cells and mature, matrix secreting osteoblasts from aged mice exhibited mitochondrial dysfunction. This was also accompanied by a lack of adaptability or metabolic flexibility to utilize exogenous substrates compared to osteoblasts cultured from young mice. Additionally, lipid droplets accumulated in both early stromal cells and mature osteoblasts from aged mice, which was further depicted as increased lipid content within the bone cortex of aged mice. Global transcriptomic analysis of the bone further supported these metabolic data as enhanced oxidative stress genes were up-regulated in aged mice, while osteoblast-related genes were down-regulated when compared to the young mice. Collectively, these data suggest that aging results in altered osteoblast metabolic handling of both exogenous and endogenous substrates which could contribute to age-related osteoporosis.

Emerging Landscape of Osteogenesis Imperfecta Pathogenesis and Therapeutic Approaches

Osteogenesis imperfecta (OI) is an uncommon genetic disorder characterized by shortness of stature, hearing loss, poor bone mass, recurrent fractures, and skeletal abnormalities. Pathogenic variations have been found in over 20 distinct genes that are involved in the pathophysiology of OI, contributing to the disorder's clinical and genetic variability. Although medications, surgical procedures, and other interventions can partially alleviate certain symptoms, there is still no known cure for OI. In this Review, we provide a comprehensive overview of genetic pathogenesis, existing treatment modalities, and new developments in biotechnologies such as gene editing, stem cell reprogramming, functional differentiation, and transplantation for potential future OI therapy.

Endothelial Cell-Derived Lactate Triggers Bone Mesenchymal Stem Cell Histone Lactylation to Attenuate Osteoporosis

Blood vessels play a role in osteogenesis and osteoporosis; however, the role of vascular metabolism in these processes remains unclear. The present study finds that ovariectomized mice exhibit reduced blood vessel density in the bone and reduced expression of the endothelial glycolytic regulator pyruvate kinase M2 (PKM2). Endothelial cell (EC)-specific deletion of Pkm2 impairs osteogenesis and worsens osteoporosis in mice. This is attributed to the impaired ability of bone mesenchymal stem cells (BMSCs) to differentiate into osteoblasts. Mechanistically, EC-specific deletion of Pkm2 reduces serum lactate levels secreted by ECs, which affect histone lactylation in BMSCs. Using joint CUT&Tag and RNA sequencing analyses, collagen type I alpha 2 chain (COL1A2), cartilage oligomeric matrix protein (COMP), ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), and transcription factor 7 like 2 (TCF7L2) as osteogenic genes regulated by histone H3K18la lactylation are identified. PKM2 overexpression in ECs, lactate addition, and exercise restore the phenotype of endothelial PKM2-deficient mice. Furthermore, serum metabolomics indicate that patients with osteoporosis have relatively low lactate levels. Additionally, histone lactylation and related osteogenic genes of BMSCs are downregulated in patients with osteoporosis. In conclusion, glycolysis in ECs fuels BMSC differentiation into osteoblasts through histone lactylation, and exercise partially ameliorates osteoporosis by increasing serum lactate levels.

En route towards a personalized medicine approach: Innovative therapeutic modalities for connective tissue disorders

Connective tissue disorders can be caused by pathogenic variants (mutations) in genes encoding extracellular matrix (ECM) proteins. Such disorders typically manifest during development or postnatal growth and result in significant morbidity and mortality. The development of curative treatments for connective tissue disorders is hampered in part by the inability of many mature connective tissues to efficiently regenerate. To be most effective, therapeutic strategies designed to preserve or restore tissue function will likely need to be initiated during phases of significant endogenous connective tissue remodeling and organ sculpting postnatally and directly target the underlying ECM protein mutations. With recent advances in whole exome sequencing, in-vitro and in-vivo disease modeling, and the development of mutation-specific molecular therapeutic modalities, it is now feasible to directly correct disease-causing mutations underlying connective tissue disorders and ameliorate their pathogenic consequences. These technological advances may lead to potentially curative personalized medicine approaches for connective tissue disorders that have previously been considered incurable. In this review, we highlight innovative therapeutic modalities including gene replacement, exon skipping, DNA/mRNA editing, and pharmacological approaches that were used to preserve or restore tissue function in the context of connective tissue disorders. Inherent to a successful application of these approaches is the need to deepen the understanding of mechanisms that regulate ECM formation and homeostasis, and to decipher how individual mutations in ECM proteins compromise ECM and connective tissue development and function.

Absence of TRIC-B from type XIV Osteogenesis Imperfecta osteoblasts alters cell adhesion and mitochondrial function - A multi-omics study

Osteogenesis Imperfecta (OI) is a heritable collagen-related bone dysplasia characterized by bone fractures, growth deficiency and skeletal deformity. Type XIV OI is a recessive OI form caused by null mutations in TMEM38B, which encodes the ER membrane intracellular cation channel TRIC-B. Previously, we showed that absence of TMEM38B alters calcium flux in the ER of OI patient osteoblasts and fibroblasts, which further disrupts collagen synthesis and secretion. How the absence of TMEM38B affects osteoblast function is still poorly understood. Here we further investigated the role of TMEM38B in human osteoblast differentiation and mineralization. TMEM38B-null osteoblasts showed altered expression of osteoblast marker genes and decreased mineralization. RNA-Seq analysis revealed that cell-cell adhesion was one of the most downregulated pathways in TMEM38B-null osteoblasts, with further validation by real-time PCR and Western blot. Gap and tight junction proteins were also decreased by TRIC-B absence, both in patient osteoblasts and in calvarial osteoblasts of Tmem38b-null mice. Disrupted cell adhesion decreased mutant cell proliferation and cell cycle progression. An important novel finding was that TMEM38B-null osteoblasts had elongated mitochondria with altered fusion and fission markers, MFN2 and DRP1. In addition, TMEM38B-null osteoblasts exhibited a significant increase in superoxide production in mitochondria, further supporting mitochondrial dysfunction. Together these results emphasize the novel role of TMEM38B/TRIC-B in osteoblast differentiation, affecting cell-cell adhesion processes, gap and tight junction, proliferation, cell cycle, and mitochondrial function.

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

Osteogenesis imperfecta (OI) is a family of rare heritable skeletal disorders associated with dominant mutations in the collagen type I encoding genes and recessive defects in proteins involved in collagen type I synthesis and processing and in osteoblast differentiation and activity. Historically, it was believed that the OI bone phenotype was only caused by abnormal collagen type I fibrils in the extracellular matrix, but more recently it became clear that the altered bone cell homeostasis, due to mutant collagen retention, plays a relevant role in modulating disease severity in most of the OI forms and it is correlated to impaired bone cell differentiation. Despite in vitro evidence, in vivo data are missing. To better understand the physiopathology of OI, we used two zebrafish models: Chihuahua (Chi/+), carrying a dominant p.G736D substitution in the α1 chain of collagen type I, and the recessive p3h1-/-, lacking prolyl 3-hydroxylase (P3h1) enzyme. Both models share the delay of collagen type I folding, resulting in its overmodification and partial intracellular retention. The regeneration of the bony caudal fin of Chi/+ and p3h1-/- was employed to investigate the impact of abnormal collagen synthesis on bone cell differentiation. Reduced regenerative ability was evident in both models, but it was associated to impaired osteoblast differentiation and osteoblastogenesis/adipogenesis switch only in Chi/+. On the contrary, reduced osteoclast number and activity were found in both models during regeneration. The dominant OI model showed a more detrimental effect in the extracellular matrix organization. Interestingly, the chemical chaperone 4-phenylbutyrate (4-PBA), known to reduce cellular stress and increase collagen secretion, improved bone formation only in p3h1-/- by favoring caudal fin growth without affecting bone cell markers expression. Taken together, our in vivo data proved the negative impact of structurally abnormal collagen type I on bone formation but revealed a gene mutation-specific effect on bone cell differentiation and matrix organization in OI. These, together with the distinct ability to respond to the chaperone treatment, underline the need for precision medicine approaches to properly treat the disease.

CaMKII inhibition due to TRIC-B loss-of-function dysregulates SMAD signaling in osteogenesis imperfecta

Ca2+ is a second messenger that regulates a variety of cellular responses in bone, including osteoblast differentiation. Mutations in trimeric intracellular cation channel B (TRIC-B), an endoplasmic reticulum channel specific for K+, a counter ion for Ca2+flux, affect bone and cause a recessive form of osteogenesis imperfecta (OI) with a still puzzling mechanism. Using a conditional Tmem38b knock out mouse, we demonstrated that lack of TRIC-B in osteoblasts strongly impairs skeleton growth and structure, leading to bone fractures. At the cellular level, delayed osteoblast differentiation and decreased collagen synthesis were found consequent to the Ca2+ imbalance and associated with reduced collagen incorporation in the extracellular matrix and poor mineralization. The impaired SMAD signaling detected in mutant mice, and validated in OI patient osteoblasts, explained the osteoblast malfunction. The reduced SMAD phosphorylation and nuclear translocation were mainly caused by alteration in Ca2+ calmodulin kinase II (CaMKII)-mediated signaling and to a less extend by a lower TGF-β reservoir. SMAD signaling, osteoblast differentiation and matrix mineralization were only partially rescued by TGF-β treatment, strengthening the impact of CaMKII-SMAD axes on osteoblast function. Our data established the TRIC-B role in osteoblasts and deepened the contribution of the CaMKII-SMAD signaling in bone.

DNA methyltransferases inhibitor azacitidine improves the skeletal phenotype of mild osteogenesis imperfecta by reversing the impaired osteogenesis and excessive osteoclastogenesis

BACKGROUND

Osteogenesis imperfecta (OI), as a disease of congenital bone dysplasia, is often accompanied by the abnormal alteration of bone absorption and bone formation. DNA methyltransferases (Dnmts) can regulate the gene expression involved in osteogenesis and osteoclastogenesis. Dnmts changes and their effects on bone cells under OI is poorly understood.

METHODS

The Dnmts expression in adipose derived mesenchymal stem cells (ADSCs), bone marrow derived pre-osteoclasts (pre-Ocs) and femurs of Col1a2^oim/+ and Col1a1^+/-365 mice, both modeling mild OI types, were determined. The effects of azacitidine (Aza) administration and Dnmt3a knockdown by ShRNA on the osteogenic differentiation of ADSCs together with osteoclasts (Ocs) production of pre-Ocs were studied in vitro. The synthesis and secretion of collagen fibers of OI derived ADSCs were examined. The therapeutic outcomes of intraperitoneal (i.p.) infused Aza (1 mg/kg/2d) for 30 days were evaluated in OI mice.

RESULTS

Obviously elevated expression of Dnmts, especially Dnmt3a, existed in ADSCs, pre-Ocs, and femurs isolated from OI modeled mice. Much more collagen molecules of mutant ADSCs were secreted into the extracellular medium post Aza addition. Both Aza administration and Dnmt3a knockdown effectively enhanced the bone-forming capacity of affected ADSCs and reduced Ocs formation of OI mice in vitro. Aza treatment apparently improved the femora microstructure and biomechanical properties, increased bone formation and decreased the number of Ocs in mice with OI.

CONCLUSION

Highly expressed Dnmt3a contributed to the impaired osteogenesis and enhanced osteoclastogenesis of collagen defect-related OI. Aza medication effectively improved the femora phenotype of the two types of OI modeled mice partly by Dnmts inhibition and modulating cell stress response. These findings facilitated understanding the role of Dnmts alteration in skeletal pathological development of mild OI and preliminary confirmed the therapeutic potential of Dnmts depressants in mild OI treatment. Still, further researches are needed to explore the specific function of Dnmts in OI bones and clarify the benefits of Aza administration in OI treatment.

Zebrafish Tric-b is required for skeletal development and bone cells differentiation

INTRODUCTION

Trimeric intracellular potassium channels TRIC-A and -B are endoplasmic reticulum (ER) integral membrane proteins, involved in the regulation of calcium release mediated by ryanodine (RyRs) and inositol 1,4,5-trisphosphate (IP₃Rs) receptors, respectively. While TRIC-A is mainly expressed in excitable cells, TRIC-B is ubiquitously distributed at moderate level. TRIC-B deficiency causes a dysregulation of calcium flux from the ER, which impacts on multiple collagen specific chaperones and modifying enzymatic activity, leading to a rare form of osteogenesis imperfecta (OI Type XIV). The relevance of TRIC-B on cell homeostasis and the molecular mechanism behind the disease are still unknown.

RESULTS

In this study, we exploited zebrafish to elucidate the role of TRIC-B in skeletal tissue. We demonstrated, for the first time, that tmem38a and tmem38b genes encoding Tric-a and -b, respectively are expressed at early developmental stages in zebrafish, but only the latter has a maternal expression. Two zebrafish mutants for tmem38b were generated by CRISPR/Cas9, one carrying an out of frame mutation introducing a premature stop codon (tmem38b^-/- ) and one with an in frame deletion that removes the highly conserved KEV domain (tmem38b^{Δ120-7/Δ120-7} ). In both models collagen type I is under-modified and partially intracellularly retained in the endoplasmic reticulum, as described in individuals affected by OI type XIV. Tmem38b^-/- showed a mild skeletal phenotype at the late larval and juvenile stages of development whereas tmem38b^{Δ120-7/Δ120-7} bone outcome was limited to a reduced vertebral length at 21 dpf. A caudal fin regeneration study pointed towards impaired activity of osteoblasts and osteoclasts associated with mineralization impairment.

DISCUSSION

Our data support the requirement of Tric-b during early development and for bone cell differentiation.

Murine Animal Models in Osteogenesis Imperfecta: The Quest for Improving the Quality of Life

Osteogenesis imperfecta is a rare genetic disorder characterized by bone fragility, due to alterations in the type I collagen molecule. It is a very heterogeneous disease, both genetically and phenotypically, with a high variability of clinical phenotypes, ranging from mild to severe forms, the most extreme cases being perinatal lethal. There is no curative treatment for OI, and so great efforts are being made in order to develop effective therapies. In these attempts, the in vivo preclinical studies are of paramount importance; therefore, serious analysis is required to choose the right murine OI model able to emulate as closely as possible the disease of the target OI population. In this review, we summarize the features of OI murine models that have been used for preclinical studies until today, together with recently developed new murine models. The bone parameters that are usually evaluated in order to determine the relevance of new developing therapies are exposed, and finally, current and innovative therapeutic strategies attempts considered in murine OI models, along with their mechanism of action, are reviewed. This review aims to summarize the in vivo studies developed in murine models available in the field of OI to date, in order to help the scientific community choose the most accurate OI murine model when developing new therapeutic strategies capable of improving the quality of life.

Rosemary Extract-Induced Autophagy and Decrease in Accumulation of Collagen Type I in Osteogenesis Imperfecta Skin Fibroblasts

Osteogenesis imperfecta (OI) is a heterogeneous connective tissue disease mainly caused by structural mutations in type I collagen. Mutant collagen accumulates intracellularly, causing cellular stress that has recently been shown to be phenotype-related. Therefore, the aim of the study was to search for potential drugs reducing collagen accumulation and improving OI fibroblast homeostasis. We found that rosemary extract (RE), which is of great interest to researchers due to its high therapeutic potential, at concentrations of 50 and 100 µg/mL significantly reduced the level of accumulated collagen in the fibroblasts of four patients with severe and lethal OI. The decrease in collagen accumulation was associated with RE-induced autophagy as was evidenced by an increase in the LC3-II/LC3-I ratio, a decrease in p62, and co-localization of type I collagen with LC3-II and LAMP2A by confocal microscopy. The unfolded protein response, activated in three of the four tested cells, and the level of pro-apoptotic markers (Bax, CHOP and cleaved caspase 3) were attenuated by RE. In addition, the role of RE-modulated proteasome in the degradation of unfolded procollagen chains was investigated. This study provides new insight into the beneficial effects of RE that may have some implications in OI therapy targeting cellular stress.

Dissecting the phenotypic variability of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a heterogeneous family of collagen type I-related diseases characterized by bone fragility. OI is most commonly caused by single-nucleotide substitutions that replace glycine residues or exon splicing defects in the COL1A1 and COL1A2 genes that encode the α1(I) and α2(I) collagen chains. Mutant collagen is partially retained intracellularly, impairing cell homeostasis. Upon secretion, it assembles in disorganized fibrils, altering mineralization. OI is characterized by a wide range of clinical outcomes, even in the presence of identical sequence variants. Given the heterotrimeric nature of collagen I, its amino acid composition and the peculiarity of its folding, several causes may underlie the phenotypic variability of OI. A deep analysis of entries regarding glycine and splice site collagen substitution of the largest publicly available patient database reveals a higher risk of lethal phenotype for carriers of variants in α1(I) than in α2(I) chain. However, splice site variants are predominantly associated with lethal phenotype when they occur in COL1A2. In addition, lethality is increased when mutations occur in regions of importance for extracellular matrix interactions. Both extracellular and intracellular determinants of OI clinical severity are discussed in light of the findings from in vitro and in vivo OI models. Combined with meticulous tracking of clinical cases via a publicly available database, the available OI animal models have proven to be a unique tool to shed light on new modulators of phenotype determination for this rare heterogeneous disease.

Collagen misfolding mutations: the contribution of the unfolded protein response to the molecular pathology

Mutations in collagen genes cause a broad range of connective tissue pathologies. Structural mutations that impact procollagen assembly or triple helix formation and stability are a common and important mutation class. How misfolded procollagens engage with the cellular proteostasis machinery and whether they can elicit a cytotoxic unfolded protein response (UPR) is a topic of considerable research interest. Such interest is well justified since modulating the UPR could offer a new approach to treat collagenopathies for which there are no current disease mechanism-targeting therapies. This review scrutinizes the evidence underpinning the view that endoplasmic reticulum stress and chronic UPR activation contributes significantly to the pathophysiology of the collagenopathies. While there is strong evidence that the UPR contributes to the pathology for collagen X misfolding mutations, the evidence that misfolding mutations in other collagen types induce a canonical, cytotoxic UPR is incomplete. To gain a more comprehensive understanding about how the UPR amplifies to pathology, and thus what types of manipulations of the UPR might have therapeutic relevance, much more information is needed about how specific misfolding mutation types engage differentially with the UPR and downstream signaling responses. Most importantly, since the capacity of the proteostasis machinery to respond to collagen misfolding is likely to vary between cell types, reflecting their functional roles in collagen and extracellular matrix biosynthesis, detailed studies on the UPR should focus as much as possible on the actual target cells involved in the collagen pathologies.

Compression Fractures and Partial Phenotype Rescue With a Low Phosphorus Diet in the Chihuahua Zebrafish Osteogenesis Imperfecta Model

Osteogenesis imperfecta (OI) is a group of heritable disorders affecting bone and other connective tissues. Dominant OI forms are mainly caused by mutations in collagen type I. Patients suffer from skeletal deformities, fractures of long bones and vertebral compression fractures from early childhood onward. Altered collagen structure and excess mineralisation are the main causes for the bone phenotype. The Chihuahua (Chi/+) zebrafish has become an important model for OI. Given that reduced dietary phosphorus (P) intake reduces the bone mineral content and promotes bone matrix formation in teleosts, including zebrafish, we tested whether a low dietary P (LP) intake mitigates the OI phenotype in the Chi/+ model. To answer this question, we characterised the Chi/+ vertebral column phenotype at a morphological, cellular and subcellular level. We present the first description of vertebral compression fractures in Chi/+ and assess the effects of LP diet on the Chi/+ phenotype (Chi/+_LP). Compared to untreated Chi/+, two months of LP dietary treatment decreases vertebral deformities in the abdominal region and reduces shape variation of caudal vertebral bodies to a condition more similar to wild type (WT). At the histological level, the osteoid layer, covering the bone at the vertebral body endplates in WT zebrafish, is absent in Chi/+, but it is partially restored with the LP diet. Whole mount-stained specimens and histological sections show various stages of vertebral compression fractures in Chi/+ and Chi/+_LP animals. Both Chi/+ and Chi/+_LP show abundant osteoclast activity compared to WT. Finally, the ultrastructure analysis of WT, Chi/+ and Chi/+_LP shows Chi/+ and Chi/+_LP osteoblasts with enlarged endoplasmic reticulum cisternae and a high protein content, consistent with intracellular retention of mutated collagen. Nevertheless, the secreted collagen in Chi/+_LP appears better organised concerning fibre periodicity compared to Chi/+. Our findings suggest that a reduced mineral content of Chi/+ bone could explain the lower frequency of vertebral column deformities and the restored shape of the vertebral bodies in Chi/+_LP animals. This, together with the improved quality of the bone extracellular matrix, suggests that two months of reduced dietary P intake can alleviate the severe bone phenotype in Chi/+ zebrafish.

The Beneficial Effect of Rosmarinic Acid on Benzophenone-3-Induced Alterations in Human Skin Fibroblasts

Benzophenone-3 (BP-3) is one of the most widely used chemical sunscreens. The results of many in vitro and in vivo tests confirm its high percutaneous penetration and systemic absorption, which question the safety of its wide use. The aim of our research was to assess the effect of this compound on components of the skin extracellular matrix, and to investigate whether rosmarinic acid (RA) could reduce BP-3-induced changes in human skin fibroblasts. BP-3 used at concentrations of 0.1-100 µM caused a number of unfavorable changes in the level of type I collagen, decorin, sulfated glycosaminoglycans, hyaluronic acid, elastin, and expression or activity of matrix metalloproteinases (MMP-1, MMP-2), elastase and hyaluronidase. Moreover, the intracellular retention of collagen was accompanied by changes in the expression of proteins modifying and controlling the synthesis and secretion of this protein. Most importantly, RA at a concentration of 100 µM significantly reduced or completely abolished the adverse effects of BP-3. Based on these findings, it can be concluded that this polyphenol may provide effective protection against BP-3-induced disturbances in skin cells, which may have important clinical implications.

Osteogenesis Imperfecta: Current and Prospective Therapies

Osteogenesis Imperfecta (OI) is a group of connective tissue disorders with a broad range of phenotypes characterized primarily by bone fragility. The prevalence of OI ranges from about 1:15,000 to 1:20,000 births. Five types of the disease are commonly distinguished, ranging from a mild (type I) to a lethal one (type II). Types III and IV are severe forms allowing survival after the neonatal period, while type V is characterized by a mild to moderate phenotype with calcification of interosseous membranes. In most cases, there is a reduction in the production of normal type I collagen (col I) or the synthesis of abnormal collagen as a result of mutations in col I genes. Moreover, mutations in genes involved in col I synthesis and processing as well as in osteoblast differentiation have been reported. The currently available treatments try to prevent fractures, control symptoms and increase bone mass. Commonly used medications in OI treatment are bisphosphonates, Denosumab, synthetic parathyroid hormone and growth hormone for children therapy. The main disadvantages of these therapies are their relatively weak effectiveness, lack of effects in some patients or cytotoxic side effects. Experimental approaches, particularly those based on stem cell transplantation and genetic engineering, seem to be promising to improve the therapeutic effects of OI.