Bone development and remodeling in metabolic disorders

Are secondary effects of bisphosphonates on the vascular system of bone contributing to increased risk for atypical femoral fractures in osteoporosis?

Osteoporosis (OP) is a bone disease which affects a number of post-menopausal females and puts many at risk for fractures. A large number of patients are taking bisphosphonates (BPs) to treat their OP and a rare complication is the development of atypical femoral fractures (AFF). No real explanations for the mechanisms underlying the basis for development of where AFF develop while on BPs has emerged. The present hypothesis will discuss the possibility that part of the risk for an AFF is a secondary effect of BPs on a subset of vascular cells in a genetically at-risk population, leading to localized deregulation of the endothelial cell (EC)-bone cell-matrix units in nutrient channels/canals of the femur and increased risk for AFF. This concept of targeting ECs is consistent with location of AFF in the femur, the bilateral risk for occurrence of AFF, and the requirement for long term exposure to the drugs.

Developmental principles informing human pluripotent stem cell differentiation to cartilage and bone

Human pluripotent stem cells can differentiate into any cell type given appropriate signals and hence have been used to research early human development of many tissues and diseases. Here, we review the major biological factors that regulate cartilage and bone development through the three main routes of neural crest, lateral plate mesoderm and paraxial mesoderm. We examine how these routes have been used in differentiation protocols that replicate skeletal development using human pluripotent stem cells and how these methods have been refined and improved over time. Finally, we discuss how pluripotent stem cells can be employed to understand human skeletal genetic diseases with a developmental origin and phenotype, and how developmental protocols have been applied to gain a better understanding of these conditions.

The Role of Sphingolipid Metabolism in Bone Remodeling

Emerging studies of bioactive lipids have made many exciting discoveries in recent years. Sphingolipids and their metabolites perform a wide variety of cellular functions beyond energy metabolism. Emerging evidence based on genetically manipulated mouse models and molecular biology allows us to obtain new insights into the role sphingolipid played on skeletal remodeling. This review summarizes studies or understandings of the crosstalk between sphingomyelin, ceramide, and sphingosine-1-phosphate (S1P) of sphingolipids family and the cells, especially osteoblasts and osteoclasts of the bone through which bone is remodeled during life constantly. This review also shows agonists and antagonists of S1P as possible therapeutic options and opportunities on bone diseases.

Calcium fructoborate coating of titanium-hydroxyapatite implants by chemisorption deposition improves implant osseointegration in the femur of New Zealand White rabbit experimental model

BACKGROUND

The identification of biocomposites that improve cell adhesion and reduce bone integration time is a great challenge for implantology and bone reconstruction.

AIM

Our aim was to evaluate a new method of chemisorption deposition (CD) for improving the biointegration of hydroxyapatite-coated titanium (HApTi) implants. CD method was used to prepare a calcium fructoborate (CaFb) coating on a HApTi (HApTiCaFb) implant followed by evaluation of histological features related to bone healing at the interface of a bioceramic material in an animal model.

METHODS

The coating composition was investigated by high-performance thin-layer chromatography/mass spectrometry. The surface morphology of the coating was studied by scanning electron microscopy (SEM), before and after the in vitro study. We implanted two types of bioceramic cylinders, HApTi and HApTiCaFb, in the femur of 10 New Zealand White (NZW) rabbits.

RESULTS

The release of CaFb from HApTiCaFb occurred rapidly within the first three days after phosphate-buffered saline immersion; there was then a linear release for up to 14 days. SEM analysis showed similar morphology and particle size diameter for both implants. Around the porous HApTiCaFb implant, fibrosis and inflammation were not highlighted.

CONCLUSIONS

Easily applied using CD method, CaFb coatings promote HApTi implant osseointegration in the femur of NZW rabbits.

Bisphosphonates Reduce Smoking-Induced Osteoporotic-Like Alterations by Regulating RANKL/OPG in an Osteoblast and Osteoclast Co-Culture Model

Co-culture models have become mandatory for obtaining better insights into bone homeostasis, which relies on the balance between osteoblasts and osteoclasts. Cigarette smoking (CS) has been proven to increase the risk of osteoporosis; however, there is currently no proven treatment for osteoporosis in smokers excluding cessation. Bisphosphonates (BPs) are classical anti-osteoclastic drugs that are commonly used in examining the suitability of bone co-culture systems in vitro as well as to verify the response to osteoporotic stimuli. In the present study, we tested the effects of BPs on cigarette smoke extract (CSE)-affected cells in the co-culture of osteoblasts and osteoclasts. Our results showed that BPs were able to reduce CSE-induced osteoporotic alterations in the co-culture of osteoblasts and osteoclasts such as decreased matrix remodeling, enhanced osteoclast activation, and an up-regulated receptor activator of nuclear factor (NF)-kB-ligand (RANKL)/osteoprotegerin (OPG) ratio. In summary, BPs may be an effective alternative therapy for reversing osteoporotic alterations in smokers, and the potential mechanism is through modulation of the RANKL/OPG ratio.

Desktop-Stereolithography 3D Printing of a Polyporous Extracellular Matrix Bioink for Bone Defect Regeneration

Introduction

Decellularized tendon extracellular matrix (tECM) perfectly provides the natural environment and holds great potential for bone regeneration in Bone tissue engineering (BTE) area. However, its densifying fiber structure leads to reduced cell permeability. Our study aimed to combine tECM with polyethylene glycol diacrylate (PEGDA) to form a biological scaffold with appropriate porosity and strength using stereolithography (SLA) technology for bone defect repair.

Methods

The tECM was produced and evaluated. Mesenchymal stem cell (MSC) was used to evaluate the biocompatibility of PEGDA/tECM bioink in vitro. Mineralization ability of the bioink was also evaluated in vitro. After preparing 3D printed polyporous PEGDA/tECM scaffolds (3D-pPES) via SLA, the calvarial defect generation capacity of 3D-pPES was assessed.

Results

The tECM was obtained and the decellularized effect was confirmed. The tECM increased the swelling ratio and porosity of PEGDA bioink, both cellular proliferation and biomineralization in vitro of the bioink were significantly optimized. The 3D-pPES was fabricated. Compared to the control group, increased cell migration efficiency, up-regulation of osteogenic differentiation RNA level, and better calvarial defect repair in rat of the 3D-pPES group were observed.

Conclusion

This study demonstrates that the 3D-pPES may be a promising strategy for bone defect treatment.

Circular RNA hsa_circ_0001445 in plasma as a novel biomarker for osteoporosis in postmenopausal women

Background: The present study evaluated the potential of hsa_circ_0001445 as a biomarker in plasma for postmenopausal patients with osteoporosis (OPO). Materials & methods: The expression levels of hsa_circ_0001445 in plasma were detected in healthy controls, patients with osteopenia (OPE) and patients with OPO by using quantitative reverse-transcriptase PCR. Results: The expression levels of hsa_circ_0001445 in plasma were much lower in OPO patients compared with OPE patients and healthy controls. Its expression was positively correlated with the T-score and was negatively correlated with β-isomerized C-terminal telopeptides (β-CTx). It could distinguish OPE or/and OPO patients from healthy controls. Moreover, its expression was significantly upregulated in the plasma of OPO patients after anti-osteoporotic treatment. Conclusion: Hsa_circ_0001445 in plasma may be a novel potential diagnostic biomarker for OPO.

Coumarin Ameliorates Impaired Bone Turnover by Inhibiting the Formation of Advanced Glycation End Products in Diabetic Osteoblasts and Osteoclasts

Accumulating evidence demonstrates that the risk of osteoporotic fractures increases in patients with diabetes mellitus. Thus, diabetes-induced bone fragility has recently been recognized as a diabetic complication. As the fracture risk is independent of the reduction in bone mineral density, deterioration in bone quality may be the main cause of bone fragility. Coumarin exists naturally in many plants as phenylpropanoids and is present in tonka beans in significantly high concentrations. This study investigated whether coumarin ameliorated the impaired bone turnover and remodeling under diabetic condition. The in vitro study employed murine macrophage Raw 264.7 cells differentiated to multinucleated osteoclasts with receptor activator of nuclear factor-κΒ ligand (RANKL) in the presence of 33 mM glucose and 1–20 μM coumarin for five days. In addition, osteoblastic MC3T3-E1 cells were exposed to 33 mM glucose for up to 21 days in the presence of 1–20 μM coumarin. High glucose diminished tartrate-resistant acid phosphatase activity and bone resorption in RANKL-differentiated osteoclasts, accompanying a reduction of cathepsin K induction and actin ring formation. In contrast, coumarin reversed the defective osteoclastogenesis in diabetic osteoclasts. Furthermore, high glucose diminished alkaline phosphatase activity and collagen type 1 induction of osteoblasts, which was strongly enhanced by submicromolar levels of coumarin to diabetic cells. Furthermore, coumarin restored the induction of RANK and osteoprotegerin in osteoclasts and osteoblasts under glucotoxic condition, indicating a tight coupling of osteoclastogenesis and osteoblastogenesis. Coumarin ameliorated the impaired bone turnover and remodeling in diabetic osteoblasts and osteoclasts by suppressing the interaction between advanced glycation end product (AGE) and its receptor (RAGE). Therefore, coumarin may restore optimal bone turnover of osteoclasts and osteoblasts by disrupting the hyperglycemia-mediated AGE–RAGE interaction.