Effects of vascular endothelial growth factor on osteoblasts and osteoclasts

The role of lipid metabolism in osteoporosis: Clinical implication and cellular mechanism

In recent years, researchers have become focused on the relationship between lipids and bone metabolism balance. Moreover, many diseases related to lipid metabolism disorders, such as nonalcoholic fatty liver disease, atherosclerosis, obesity, and menopause, are associated with osteoporotic phenotypes. It has been clinically observed in humans that these lipid metabolism disorders promote changes in osteoporosis-related indicators bone mineral density and bone mass. Furthermore, similar osteoporotic phenotype changes were observed in high-fat and high-cholesterol-induced animal models. Abnormal lipid metabolism (such as increased oxidized lipids and elevated plasma cholesterol) affects bone microenvironment homeostasis via cross-organ communication, promoting differentiation of mesenchymal stem cells to adipocytes, and inhibiting commitment towards osteoblasts. Moreover, disturbances in lipid metabolism affect the bone metabolism balance by promoting the secretion of cytokines such as receptor activator of nuclear factor-kappa B ligand by osteoblasts and stimulating the differentiation of osteoclasts. Conclusively, this review addresses the possible link between lipid metabolism disorders and osteoporosis and elucidates the potential modulatory mechanisms and signaling pathways by which lipid metabolism affects bone metabolism balance. We also summarize the possible approaches and prospects of intervening lipid metabolism for osteoporosis treatment.

Biological alterations associated with the orthodontic treatment with conventional appliances and aligners: A systematic review of clinical and preclinical evidence

Background&objectives

Mechanical forces applied during an orthodontic tooth movement (OTM) propel several biochemical and molecular responses in the periodontal ligament and alveolar bone. Here, we compile the existing clinical and preclinical evidence on these biological changes, aiming to provide a comprehensive discussion on the influence of the mechanical parameters of the OTM in the biological profile of the periodontium.

Material and methods

This systematic integrative review was conducted according to PICOS strategy and PRISMA guidelines. A bibliographic search was performed in three electronic databases (PubMed, Scopus, and Web of Science) to find research articles published until 2023 and written in English. This search resulted in a total of 2279 publications, which were independently assessed by two evaluators using appropriate tools.

Results

Forty-six studies were selected for this review. These revealed that compression, and stretching of the periodontal ligament fibers and cells are observed in the initial phase of the OTM. Specifically, on the tension side, high levels of IL-1β, OPG, and TIMPs are identified. On the compression side, an increase of RANKL, RANK, and MMPs levels predominate.

Conclusion

This paper describes the release profile of common biomarkers according to the orthodontic protocol, suggesting the most appropriate parameters to keep the teeth and their supporting structures healthy. Overall, this manuscript provides a better understanding of the OTM-associated biological phenomena, also highlighting the importance of early evaluation of oral health, and thus it contributes as a fundamental basis for the development of more effective and safe orthodontic treatments with conventional appliances and aligners.

Osteoporosis in polycystic ovary syndrome (PCOS) and involved mechanisms

Polycystic Ovary Syndrome (PCOS) and osteoporosis, though seemingly unrelated, exhibit intricate connections influenced by genetic and epigenetic factors. PCOS, characterized by elevated androgen levels, insulin resistance, and increased body weight, has historically been considered protective against bone fragility disorders. However, emerging research suggests that chronic inflammation, prevalent in PCOS, can adversely affect bone health. Studies have demonstrated variable bone mineral density loss in PCOS, often associated with leptin resistance and hyperinsulinemia. Key genes such as INS, IGF1, CTNNB1, AKT1, and STAT3 play pivotal roles in the complex interplay between PCOS and osteoporosis, influencing insulin signaling, oxidative stress, and inflammatory pathways. Oxidative stress, a prominent element in PCOS, can lead to osteoporosis through hormonal imbalances, chronic inflammation, insulin resistance, and lifestyle factors. The insulin signaling pathway also significantly impacts both conditions by contributing to hormonal imbalances and bone health alterations. This intricate network of genetic and epigenetic factors underscores the need for a deeper understanding of their interrelationships. Thus, this review elucidates the multifaceted genetic, epigenetic, and inflammatory connections between PCOS and osteoporosis, highlighting their implications for bone health management in individuals with PCOS.

Megakaryocyte Secreted Factors Regulate Bone Marrow Niche Cells During Skeletal Homeostasis, Aging, and Disease

The bone marrow microenvironment contains a diverse array of cell types under extensive regulatory control and provides for a novel and complex mechanism for bone regulation. Megakaryocytes (MKs) are one such cell type that potentially acts as a master regulator of the bone marrow microenvironment due to its effects on hematopoiesis, osteoblastogenesis, and osteoclastogenesis. While several of these processes are induced/inhibited through MK secreted factors, others are primarily regulated by direct cell-cell contact. Notably, the regulatory effects that MKs exert on these different cell populations has been found to change with aging and disease states. Overall, MKs are a critical component of the bone marrow that should be considered when examining regulation of the skeletal microenvironment. An increased understanding of the role of MKs in these physiological processes may provide insight into novel therapies that can be used to target specific pathways important in hematopoietic and skeletal disorders.

HIF-1α regulates osteoclast activation and mediates osteogenesis during mandibular bone repair via CT-1

OBJECTIVES

Hypoxia is one of the characteristics of microenvironmental changes after orthognathic surgery for fractures. HIF-1α is a main regulator of the hypoxic response and plays a crucial role in bone formation, remodelling, and homeostasis. Osteoclasts participate in bone absorption and affect osteogenesis, and osteoclasts differentiate in a path from the oxygen-rich bone marrow to oxygen-deficient bone lesions. Thus, we aimed to study the key functions of HIF-1α in osteoclasts during mandibular healing after osteotomy.

MATERIALS AND METHODS

The function of HIF-1α in osteoclasts during fracture healing in osteoclast-specific HIF-1α-conditional-knockout mice was investigated in mandibular osteotomy. Primary osteoclasts were used to explore the expression of HIF-1α and cardiotrophin-1 (CT-1) at both the mRNA and protein levels. The ability of BMSCs co-cultured with conditioned media from osteoclast-specific HIF-1α-knockout primary osteoclasts was detected using osteoclast-mediated osteogenesis experiments.

RESULTS

Hypoxia-inducible factor-1α increased osteoclastogenesis and bone resorption, and a delay in bone healing was found in osteoclast-specific HIF-1α-conditional-knockout mice compared with normal mice. HIF-1α-knockout primary osteoclasts inhibited bone resorption and CT-1 expression, and HIF-1α enhanced the osteoclast-mediated stimulation of BMSC differentiation by secreting CT-1.

CONCLUSIONS

Hypoxia-inducible factor-1α can play a key role in the physiology and pathogenesis of bone resorption by promoting osteoclastogenesis during fracture and influencing osteogenesis through CT-1 during bone healing.

A Unique Triculture Model to Study Osteoblasts, Osteoclasts, and Endothelial Cells

IMPACT STATEMENT

In this article, we first developed a new medium to culture together primary human osteoblastic, osteoclastic, and endothelial cells (ECs) chosen to represent the three major bone cell tissues. Indeed, no study has been conducted on primary human cells and on the phenotype/activity retention of these three primary human cell types. Thus, we established an original triculture model with osteoblastic, osteoclastic, and ECs, where not only both cell phenotype and cell activity were maintained but also cell culture homeostasis. These promising results will permit further investigations to create in vitro conditions to mimic the bone microenvironment and analyze cell interactions in ex vivo studies.

The interrelationship of bone and cardiovascular remodeling biomarkers and clinical peculiarities of coronary artery disease in postmenopausal women

Objectives

To investigate the interrelationship between bone and cardiovascular remodeling biomarkers and some clinical, laboratory and instrumental parameters of coronary artery disease in postmenopausal women.

Material and methods

The double open cross-sectional monocentric clinical study in parallel groups involved 115 women in the postmenopausal period with coronary artery disease (CAD): stable exertional angina of functional class (FC) II–III (mean age 67.07 ±0.92 years). Depending on the bone mineral density (BMD) state, all patients were divided into 3 groups: group 1 (n = 24) – patients with normal BMD (T-criterion more than 1 SD); group 2 (n = 34) – patients with osteopenia (T-criterion from –1 SD to –2.5 SD); group 3 (n = 44) – patients with osteoporosis (T-criterion less than –2.5 SD). The selected control group consisted of 12 relatively healthy women of the corresponding age. All patients underwent cardiovascular and bone remodeling biomarkers’ assessment, lipid profile tests, daily monitoring of ECG by Holter, two-dimensional echocardiography and pulsed-wave Doppler. Intima-media complex (IMC) measurement, ultrasound densitometry, and the FRAX algorithm were performed.

Results

In women with coronary artery disease and postmenopausal osteoporosis (PMO), there was a significant increase in the level of bone osteoprotegerin (OPG), osteocalcin and vascular remodeling biomarkers (VEGF-A, homocysteine) in parallel with the progression of BMD disorders. The existence of a correlative dependence between osteoprotegerin level and the 10-year risk of fracture of the radial bone (r = 0.46; p < 0.05) was discovered. A probable interrelationship between the OPG, osteocalcin, VEGF-A and homocysteine level and decrease of the T-criterion was observed. An interrelationship between the bone and cardiovascular remodeling biomarkers and atherogenic dyslipidemia, diastolic dysfunction of the left ventricle, dilatation of the left atrium, thickening of the intima-media complex, arrhythmic complications and vegetative imbalance development was proved (p < 0.05), which confirms their clinical and pathogenic role in patients with CAD and PMO.

Conclusions

The results obtained prove the existing interrelationship of bone and cardiovascular remodeling biomarkers with the state of bone mineral density and clinical peculiarities of coronary artery disease in postmenopausal women.

BMSC-derived exosomes carrying microRNA-122-5p promote proliferation of osteoblasts in osteonecrosis of the femoral head

Mesenchymal stem cells (MSCs) with multipotential differentiation capacity can differentiate into bone cells under specific conditions and can be used to treat osteonecrosis (ON) of the femoral head (ONFH) through cell transplantation. The current study aims to explore the role of bone marrow (BM) MSCs (BMSCs)-derived exosomes carrying microRNA-122-5p (miR-122-5p) in ONFH rabbit models.First, rabbit models with ONFH were established. ONFH-related miRNAs were screened using the Gene Expression Omnibus (GEO) database. A gain-of-function study was performed to investigate the effect of miR-122-5p on osteoblasts and BMSCs and effects of exosomes carrying miR-122-5p on ONFH. Co-culture experiments for osteoblasts and BMSCs were performed to examine the role of exosomal miR-122-5p in osteoblast proliferation and osteogenesis. The target relationship between miR-122-5p and Sprouty2 (SPRY2) was tested.MiR-122, significantly decreased in ONFH in the GSE89587 expression profile, was screened. MiR-122-5p negatively regulated SPRY2 and elevated the activity of receptor tyrosine kinase (RTK), thereby promoting the proliferation and differentiation of osteoblasts. In vivo experiments indicated that bone mineral density (BMD), trabecular bone volume (TBV), and mean trabecular plate thickness (MTPT) of femoral head were increased after over-expressing miR-122-5p in exosomes. Significant healing of necrotic femoral head was also observed.Exosomes carrying over-expressed miR-122-5p attenuated ONFH development by down-regulating SPRY2 via the RTK/Ras/mitogen-activated protein kinase (MAPK) signaling pathway. Findings in the present study may provide miR-122-5p as a novel biomarker for ONFH treatment.

Efficacy and safety of recombinant human parathyroid hormone (1-34) are similar to those of alendronate in the treatment of postmenopausal osteoporosis

The study evaluates efficacy and safety of recombinant human parathyroid hormone (1-34) [rhPTH (1-34)] and alendronate (ALN) in the treatment of postmenopausal osteoporosis.Totally 65 postmenopausal women with osteoporosis were divided into 2 groups. PTH group received daily subcutaneous injection of rhPTH (1-34), and ALN group were treated orally with ALN per week. Bone mineral density (BMD) of lumbar spine (1-4), femoral neck, and total hip, serum levels of calcium, phosphorus, total cholesterol, triglyceride, alkaline phosphatase (ALP), N-terminal propeptide of type I collagen (PINP), and C-telopeptide of type I collagen (CTX) were tested before treatment and at week 24 and 48 after treatment. Serum levels of vascular endothelial growth factor (VEGF) and platelet-derived growth factor-BB (PDGF-BB) were measured before treatment and at week 48 after treatment.The rhPTH (1-34) increased BMD of lumbar spine (1-4), but decreased BMD of femoral neck and total hip at week 48 after treatment. By contrast, ALN enhanced BMD of lumbar spine (1-4) and femoral neck, but reduced BMD of total hip at week 48 after treatment. In PTH group, serum levels of PINP, ALP, and β-CTX were significantly elevated above baseline at week 24 and 48 after treatment. Treatment with ALN decreased levels of PINP, ALP, and β-CTX compared with baseline at week 24 and 48 after treatment. rhPTH (1-34) and ALN significantly decreased levels of PDGF-BB, but not levels of VEGF. rhPTH (1-34) increased levels of calcium, phosphorus and triglyceride, but decreased levels of total cholesterol. ALN increased levels of calcium and triglyceride, but reduced levels of phosphorus and total cholesterol. rhPTH (1-34) and ALN were safe in the treatment of postmenopausal osteoporosis.The study demonstrates that efficacy of rhPTH (1-34) on BMD of lumbar spine (1-4) is similar to that of alendronate in the treatment of postmenopausal osteoporosis. The effect of rhPTH (1-34) on BMD of femoral neck or total hip is weaker than that of ALN. In addition, rhPTH (1-34) increases BMD of lumbar spine (1-4) maybe by raising serum levels of VEGF, but reduces BMD of femoral neck and total hip maybe by decreasing serum levels of PDGF-BB.

Inhibition of VEGF gene expression in osteoblast cells by different NSAIDs

OBJECTIVE

To determine the effect of different nonsteroidal anti-inflammatory drugs (NSAIDs) on vascular endothelial growth factor (VEGF) gene expression in two osteoblast cell populations.

DESIGN

Osteoblasts obtained by primary culture (HOp) and human osteosarcoma cell line MG63 (MG-63), which were treated with 10 μM doses of acetaminophen, indomethacin, ketoprofen, diclofenac, ibuprofen, ketorolac, naproxen or piroxicam. At 24 h of treatment, their gene expression of VEGF was evaluated by real-time polymerase chain reaction (RT-PCR) and compared with the expression in untreated cells (control group).

RESULTS

The treatment with the different NSAIDs significantly reduced VEGF expression regardless of the cell line and NSAID studied.

CONCLUSION

The results of this study suggest that these drugs may have undesirable effects on the osteoblast and its bone-forming capacity, given the effect of this growth factor on these cells. Further studies are warranted to determine their repercussions on bone tissue and to elucidate the cell signaling mechanism/s involved.

Monocarboxylate transporter 1 (MCT1), a tool to stratify acute myeloid leukemia (AML) patients and a vehicle to kill cancer cells

Dysregulation of glucose/lactate dynamics plays a role in cancer progression, and MCTs are key elements in metabolic remodeling. VEGF is a relevant growth factor in the maintenance of bone marrow microenvironment and it is also important in hematological diseases.

Our aim was to investigate the role of VEGF in the metabolic adaptation of Acute myeloid leukemia (AML) cells by evaluating the metabolic profiles and cell features according to the AML lineage and testing lactate as a metabolic coin.

Our in vitro results showed that AML promyelocytic (HL60) and monocytic (THP1) (but not erythroid- HEL) lineages are well adapted to VEGF and lactate rich environment. Their metabolic adaptation relies on high rates of glycolysis to generate intermediates for PPP to support cell proliferation, and on the consumption of glycolysis-generated lactate to supply biomass and energy production. VEGF orchestrates this metabolic network by regulating MCT1 expression. Bromopyruvic acid (BPA) was proven to be an effective cytotoxic in AML, possibly transported by MCT1.

Our study reinforces that targeting metabolism can be a good strategy to fight cancer. MCT1 expression at the time of diagnosis can assist on the identification of AML patients that will benefit from BPA therapy. Additionally, MCT1 can be used in targeted delivery of conventional cytotoxic drugs.

Histochemical and morphological aspects of fresh frozen bone: a preliminary study

Bone graft are used in dentistry for the reconstruction of severely atrophic jaws. Fresh frozen bone has no osteogenic property but it has osteoconductive and osteoinductive properties because its matrix contains growth factors such as vascular endothelial growth factor. The purpose of the present study was to evaluate morphological and protein expression characteristics of fresh frozen bone before graft and after six months of graft in patients who needed maxillary reconstruction. After 6 month of graft we observed the presence of viable bone as evidenced by full osteocyte lacunae and by the presence of RANKR, osteocalcin positive cells and vascular endothelial growth factor. In conclusion, our findings show that the fresh frozen bone after six month of graft is for the most part viable bone, encouraging its use as an alternative to autogenous bone for reconstructing maxillary bone defects prior to implant.