Stimulates Osteoblast Proliferation Research Articles

Dehydroepiandrosterone and Bone Health: Mechanisms and Insights.

Dehydroepiandrosterone (DHEA), a steroid hormone produced by the adrenal glands, plays a key role in various physiological processes, including bone health. Its age-related decline is linked to reduced bone density, though the mechanisms by which DHEA affects bone metabolism remain complex. This review summarises the diverse effects of DHEA on bone metabolism and density, highlighting its therapeutic potential; Methods: A literature search on the effects of DHEA on bone-related parameters was conducted from PubMed and Scopus using a specific search string, and after removing duplicates and irrelevant articles, 36 relevant full-text studies were included; Results: DHEA promotes osteoblast differentiation and proliferation, regulates the RANKL/OPG ratio, and inhibits osteoclastogenesis and bone resorption. Its osteogenic effects are mediated through multiple signalling pathways. In ovariectomised rat models, DHEA enhances trabecular bone volume, stimulates osteoblast proliferation, and increases oestradiol production and aromatase activity. In elderly individuals with low androgen levels, DHEA supplementation increases sulphated DHEA and oestradiol levels and improves bone mineral density, particularly in the ultra-distal radius of women and the femoral neck of men. However, the clinical use of DHEA remains debated due to inconsistent study results. Its effects on bone health may vary based on factors such as age, gender, and health conditions, emphasising the need for further research to clarify its mechanisms and optimise its use; Conclusions: In conclusion, while DHEA shows potential as a modulator of bone health, comprehensive clinical trials are required to assess its efficacy and safety, particularly in at-risk populations.

7858 Increasing Severity of Growth Hormone Deficiency is Associated with Lower Vertebral Strength

Abstract Disclosure: R. Boutin: None. M. Haines: None. R. Shahid: None. C. Mark: None. C. Gill: None. M. Bredella: None. K.K. Miller: Other; Self; Pfizer, Inc. L.E. Dichtel: Consulting Fee; Self; Lumos Pharma. Grant Recipient; Self; Lumos Pharma, Perspectum Ltd. Research Investigator; Self; Recordati, Novo Nordisk. Stock Owner; Self; Marea Therapeutics. Other; Self; Third Rock Ventures. Objective: Growth hormone (GH) stimulates osteoblast differentiation, while insulin-like growth factor-1 (IGF-1) stimulates osteoblast proliferation and bone formation. Retrospective studies have demonstrated a 2-to-3-fold increased fracture risk in adults with GH deficiency (GHD) due to organic hypothalamic or pituitary disease, particularly at vertebral sites. Adults with overweight/obesity produce relatively less GH than lean individuals, and serum IGF-1 levels are associated positively with BMD in adults with obesity. Yet, no published studies have examined the relationship between degree of GHD across these groups and vertebral strength, an understudied measure of bone quality in part because HR-pQCT cannot image this skeletal site. We hypothesized that there would be an inverse association between degree of GHD and vertebral strength, independent of age and BMI. Methods: Cross-sectional study of 134 estrogen-replete (with regular menses or taking estrogen) women: 16 with GHD secondary to hypopituitarism (HP, severe GHD), 91 with obesity (OB) without a hypothalamic/pituitary disorder (relative GHD), and 37 lean controls (LC) without a hypothalamic/pituitary disorder (normal GH production). Peak-stimulated GH was assessed by GHRH-arginine testing. CT imaging at the L4 vertebra was performed to determine vertebral cross-sectional area and total integrated volumetric bone mineral density (Int.vBMD), from which estimates of vertebral strength were calculated. Results: Mean age [44±9 (mean±SD) (HP) vs. 35±7 (OB) vs. 30±7 (LC) y, p<0.005] and BMI [30±6 (HP) vs. 34±6 (OB) vs. 22±2 (LC) kg/m2, p<0.004] differed between all groups. As expected, peak-stimulated GH was highest in LC (28.3 ± 9.5 ng/mL) followed by OB (12.4 ± 8.9 ng/mL) and HP (2.4 ± 1.7 ng/mL), p<0.0001. IGF-1 Z-scores were higher in LC (0.0 ± 0.6) and OB (0.0 ± 0.7) vs. HP (-1.4 ± 0.7), p<0.0001. Int.vBMD and vertebral strength were higher in LC and OB vs. HP [Int.vBMD (g/cm3) LC 0.21±0.04 and OB 0.21±0.04 vs. HP 0.16±0.03, and vertebral strength (N) LC 4540±850 and 4743±91 vs. HP 3542±651, both p<0.0001], which remained significant when adjusted for age and BMI (p≤0.01). Peak-stimulated GH and IGF-1 Z-scores were positively associated with vertebral strength (GH R=0.33, p=0.003 and IGF-1 Z-score R=0.41, p<0.0001) and Int.vBMD (GH R=0.46, p<0.0001 and IGF-1 Z-score R=0.40, p<0.0001), which remained significant when adjusted for age and BMI. Among the subset of patients without organic pituitary disease (LC and OB only), IGF-1 Z-scores remained positively associated with vertebral strength (R=0.24, p<0.03) and Int.vBMD (R=0.22, p<0.05). Conclusions: These findings suggest that severe GHD is associated with impaired vertebral volumetric bone density and strength. Moreover, the relative GHD of obesity may contribute to lower vertebral bone density and strength in otherwise healthy adults with overweight/obesity. Presentation: 6/3/2024

IRTKS promotes osteogenic differentiation by inhibiting PTEN phosphorylation

Insulin stimulates osteoblast proliferation and differentiation as an anabolic agent in bone. Insulin Receptor Tyrosine Kinase Substrate (IRTKS) is involved in insulin signaling as an adapter for insulin receptors (IR). Here, we showed that IRTKS levels were significantly decreased in bone marrow mesenchymal stem cells (BMSCs) derived from the bone marrow of patients with osteoporosis. Based on relevant experiments, we observed that IRTKS promoted the proliferation, migration, and osteoblast differentiation of BMSCs and MC3T3-E1 cells. In addition, we identified a Phosphatase and Tensin homolog deleted on chromosome 10 (PTEN) as a potential active substrate of IRTKS. We demonstrated a direct interaction between IRTKS and PTEN using co-immunoprecipitation. Subsequently, we confirmed that the SH3 domain of IRTKS directly binds to the C-terminal tail of PTEN. Further experimental results demonstrated that PTEN attenuated the promoting effects of IRTKS on the proliferation, migration, and osteoblast differentiation of BMSCs and MC3T3-E1 cells. In conclusion, this study suggests that IRTKS contributes to osteogenic differentiation by inhibiting PTEN phosphorylation and provides a potential therapeutic target for osteoporosis patients.

Anti-osteoporotic effects of Yi Mai Jian on bone metabolism of ovariectomized rats.

Yi Mai Jian herbal formula (YMJ) is formulated with Eucommiae Folium, Astragali Radix, Ligustri Lucidi Fructus, and Elaeagnus Fructus to improve bone function in traditional Chinese medicine. The anti-osteoporotic effects of YMJ in bone metabolism were evaluated in ovariectomized (OVX) rats. The skeletal structure of the femur and vertebrae was analyzed after treating OVX rats with YMJ for 114days. The results showed that YMJ significantly increased the bone mineral density (BMD) and trabecular number (Tb. N) of the femur and 5th lumbar vertebrae and reduced trabecular separation (Tb. Sp). Moreover, trabecular bone volume/total tissue volume (BV/TV), bone stiffness, and maximum femur load were significantly increased. The serum concentrations of NTX1 and PYD were significantly decreased. According to these results, YMJ could ameliorate osteoporosis in ovariectomized rats. Eucommiae Folium and Elaeagnus Fructus inhibited osteoclast differentiation, Ligustri Lucidi Fructus inhibited calcium reabsorption, Astragali Radix stimulated osteoblast proliferation, and Astragali Radix and Eucommiae Folium stimulated mineralization. Therefore, the combination of the four herbs into one formula, YMJ, could alleviate bone remodeling caused by low estrogen levels. We suggest that YMJ could be a healthy food candidate for preventing post-menopausal osteoporosis.

The Association of Nanostructured Carbonated Hydroxyapatite with Denatured Albumin and Platelet-Rich Fibrin: Impacts on Growth Factors Release and Osteoblast Behavior.

Platelet-rich Fibrin (PRF), a second-generation blood concentrate, offers a versatile structure for bone regeneration due to its composition of fibrin, growth factors, and cytokines, with adaptations like denatured albumin-enriched with liquid PRF (Alb-PRF), showing potential for enhanced stability and growth factor dynamics. Researchers have also explored the combination of PRF with other biomaterials, aiming to create a three-dimensional framework for enhanced cell recruitment, proliferation, and differentiation in bone repair studies. This study aimed to evaluate a combination of Alb-PRF with nanostructured carbonated hydroxyapatite microspheres (Alb-ncHA-PRF), and how this association affects the release capacity of growth factors and immunomodulatory molecules, and its impact on the behavior of MG63 human osteoblast-like cells. Alb-PRF membranes were prepared and associated with nanocarboapatite (ncHA) microspheres during polymerization. MG63 cells were exposed to eluates of both membranes to assess cell viability, proliferation, mineralization, and alkaline phosphatase (ALP) activity. The ultrastructural analysis has shown that the spheres were shattered, and fragments were incorporated into both the fibrin mesh and the albumin gel of Alb-PRF. Alb-ncHA-PRF presented a reduced release of growth factors and cytokines when compared to Alb-PRF (p < 0.05). Alb-ncHA-PRF was able to stimulate osteoblast proliferation and ALP activity at lower levels than those observed by Alb-PRF and was unable to positively affect in vitro mineralization by MG63 cells. These findings indicate that the addition of ncHA spheres reduces the biological activity of Alb-PRF, impairing its initial effects on osteoblast behavior.

The role of lactoferrin in bone remodeling: evaluation of its potential in targeted delivery and treatment of metabolic bone diseases and orthopedic conditions.

Lactoferrin (Lf) is a multifunctional protein that is synthesized endogenously and has various biological roles including immunological regulation, antibacterial, antiviral, and anticancer properties. Recently, research has uncovered Lf's critical functions in bone remodeling, where it regulates the function of osteoblasts, chondrocytes, osteoclasts, and mesenchymal stem cells. The signaling pathways involved in Lf's signaling in osteoblasts include (low density lipoprotein receptor-related protein - 1 (LRP-1), transforming growth factor β (TGF-β), and insulin-like growth factor - 1 (IGF-1), which activate downstream pathways such as ERK, PI3K/Akt, and NF-κB. These pathways collectively stimulate osteoblast proliferation, differentiation, and mineralization while inhibiting osteoclast differentiation and activity. Additionally, Lf's inhibitory effect on nuclear factor kappa B (NF-κB) suppresses the formation and activity of osteoclasts directly. Lf also promotes chondroprogenitor proliferation and differentiation to chondrocytes by activating the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) and phosphoinositide 3-kinase/protein kinase B(PI3K/Akt)signaling pathways while inhibiting the expression of matrix-degrading enzymes through the suppression of the NF-κB pathway. Lf's ability to stimulate osteoblast and chondrocyte activity and inhibit osteoclast function accelerates fracture repair, as demonstrated by its effectiveness in animal models of critical-sized long bone defects. Moreover, studies have indicated that Lf can rescue dysregulated bone remodeling in osteoporotic conditions by stimulating bone formation and suppressing bone resorption. These beneficial effects of Lf on bone health have led to its exploration in nutraceutical and pharmaceutical applications. However, due to the large size of Lf, small bioactive peptides are preferred for pharmaceutical applications. These peptides have been shown to promote bone fracture repair and reverse osteoporosis in animal studies, indicating their potential as therapeutic agents for bone-related diseases. Nonetheless, the active concentration of Lf in serum may not be sufficient at the site requiring bone regeneration, necessitating the development of various delivery strategies to enhance Lf's bioavailability and target its active concentration to the site requiring bone regeneration. This review provides a critical discussion of the issues mentioned above, providing insight into the roles of Lf in bone remodeling and the potential use of Lf as a therapeutic target for bone disorders.

Resveratrol-Induced Suppression of C-type Natriuretic Peptide Associates With Increased Vertebral Bone Density in Postmenopausal Women.

C-type natriuretic peptide (CNP) is a paracrine growth factor essential in driving endochondral bone growth in mammals including humans. Despite evidence from animal experiments and tissues that CNP signaling stimulates osteoblast proliferation and osteoclast activity, whether CNP participates in bone remodeling in the mature skeleton is unknown. Using stored plasma samples from a previous randomized controlled clinical trial (RESHAW) of resveratrol supplementation in postmenopausal women exhibiting mild osteopenia, we have studied changes in plasma aminoterminal proCNP (NTproCNP) and concurrent change in bone turnover markers of formation (osteocalcin [OC] and alkaline phosphatase [ALP]) and resorption (C-terminal telopeptide type 1 collagen [CTX]) with bone mineral density (BMD) over a 2-year period of study in 125 subjects. In year one, subjects received placebo or resveratrol, switching to resveratrol or placebo, respectively, in year two. Across all time points, there were no significant associations of NTproCNP with CTX, ALP, or OC. During year one, plasma NTproCNP declined significantly in both groups. In the crossover comparison, analysis of change within individuals showed that, compared with placebo, NTproCNP declined after resveratrol (p=0.011) and ALP increased (p=0.008), whereas CTX and OC were unchanged. Inverse association of NTproCNP (r=-0.31; p=0.025) and positive association of OC (r=0.32, p=0.022) with BMD at the lumbar spine were identified after resveratrol but not found after placebo. Decline in NTproCNP was independently associated with resveratrol treatment. This is the first evidence that CNP is modulated during a period of increasing BMD in postmenopausal women. Further study of NTproCNP and associations with drivers of bone formation or resorption can be expected to clarify CNP's role during other interventions directed to bone health in adults. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Atorvastatin reduces zoledronic acid-induced osteonecrosis of the jaws of rats.

The aim of this study was to evaluate the effect of Atorvastatin on Bisphosphonate-induced osteonecrosis of the jaws of rats. Wistar rats were divided into 4 groups: Saline, Zoledronic Acid, Atorvastatin before or after teeth extraction. BRONJ was induced by Zoledronic Acid (0.1 mg/kg). On day 42, animals were submitted to dental extraction. Atorvastatin was administered at 27 mg/kg for 3 weeks before or after oral procedure. Animals were euthanized on day 77. Maxillae were removed for macro and microscopic analyses. Immunohistochemistry for Dickopff (DKK) -1, Wnt 10b, β-catenin and caspase-3 was performed. Gingival TNF-α and IL-1β was evaluated and blood samples were collected for biochemical dosage. Atorvastatin improved mucosal healing, increased viable osteocytes (by 43 % and 47 % on pre- and post- Atorvastatin groups, respectively), while reduced Caspase-3 immunoexpression. ATV reduced bone sequestration and modulated inflammation, marked by reduction of gingival IL-1 and TNF. Atorvastatin improved the amount and quality of collagen, increased mineral content and reduced tissue solubility. When administrated prior to teeth extraction, Atorvastatin increased the number and activity of osteoblasts, through activation of the Wnt pathway. In summary, the anti-inflammatory and bone anabolic effects of Atorvastatin, maintained bone vitality, metabolism and structure, acting as an interesting pharmacological tool to modulate the disease or to assist BRONJ therapy. • Atorvastatin prevents bisphosphonate-induced osteocyte death. • Atorvastatin modulates inflammation and improves bone quality. • Atorvastatin reduces inflammation due to bisphosphonate-induced osteonecrosis. • Atorvastatin stimulates osteoblast proliferation via Wnt pathway. • Atorvastatin can be a useful tool to assist BRONJ therapy.

TBX3 regulates the transcription of VEGFA to promote osteoblasts proliferation and microvascular regeneration.

ObjectiveOsteochondral decellularization can promote local vascular regeneration, but the exact mechanism is unknown. The aim of this study is to study osteogenic microvascular regeneration in single cells.MethodsThe scRNA-seq dataset of human periosteal-derived cells (hPDCs) were analyzed by pySCENIC. To examine the role of TBX3 in osteogenesis and vascularization, cell transfection, qRT-PCR, western blot, and CCK-8 cell proliferation assays were performed.ResultsTCF7L2, TBX3, FLI1, NFKB2, and EZH2 were found to be transcription factors (TFs) most closely associated with corresponding cells. The regulatory network of these TFs was then visualized. Our study knocked down the expression of TBX3 in human osteoblast cell lines. In the TBX3 knockdown group, we observed decreased expression of VEGFA, VEGFB, and VEGFC. Moreover, Western blot analysis showed that downregulating TBX3 resulted in a reduction of VEGFA expression. And TBX3 stimulated osteoblast proliferation in CCK-8 assays.ConclusionTBX3 regulates VEGFA expression and promotes osteoblast proliferation in skeletal microvasculature formation. The findings provide a theoretical basis for investigating the role of TBX3 in promoting local vascular regeneration.

Reproductive health and stress fracture risk: a wearables solution

Introduction: Insulin-like growth factor 1 (IGF-I) is a mitogenic and metabolic growth factor that can act both systemically and locally, being produced predominantly in the liver but also by other tissues including the brain, kidneys, muscle, and bone1,2. IGF-I is well-established as an important mediator of bone formation, remodelling, and repair and can be easily measured in serum. IGF-I stimulates osteoblast proliferation, bone matrix protein synthesis, alkaline phosphatase activity and differentiation. Loss of IGF-I results in decreased long bone size, reduced growth plates, and delayed formation of secondary ossification centers in mice. Conversely, transgenic mice with osteoblast-targeted overexpression of IGF-I demonstrate an accelerated bone formation rate with increased bone mineral density (BMD) and trabecular and cortical bone volume. The essential nature of IGF-I in bone development is recapitulated in humans. Individuals with disruptions in the IGF-I gene causing reduced serum IGF-I concentrations have a severe reduction in peak BMD compared to normal age-matched individuals. Methods: This presentation will provide an overview of the relationship between the IGF-I system and bone health and remodelling, with a particular emphasis toward military relevance and utility of measuring IGF-I during military training2,3. Because the IGF-I system is involved in bone formation, remodelling, and repair, female recruits sustaining stress fractures during military training would be of special interest with regard to differential circulating concentrations of IGF-I system components compared to their uninjured female counterparts. Moreover, serum measurements of the IGF-I system could possibly provide further insight into stress fracture injury risk. Conclusions: Preliminary data3 suggest that circulating IGF-I system components are differentially expressed in females sustaining stress fractures during military BT. Additionally, data suggest that the bioavailable IGF-I response to strenuous exercise may differ in female recruits susceptible to stress fracture injury when compared to non-injured recruits. This suggests the possibility that increased susceptibility to stress fracture injury may be attributed to differences in the IGF-I system response to physical training (i.e., increased susceptibility to stress fracture may be due to a blunted bioavailable IGF-I response to training or increased basal levels of certain IGFBPs). However, the underlying mechanism for the differences in IGF-I system component concentrations between recruits sustaining stress fractures and uninjured counterparts is still unclear and warrants further investigation. References 1Nindl BC, Pierce JR. Insulin-like growth factors I as a biomarker of health, fitness, and training status. Med Sci Sports Exerc 2010; 42(1):39-49. https://doi.org/10.1249/mss.0b013e3181b07c4d 2Nindl BC, McClung JP, Miller JK, et al. Bioavailable IGF-I is associated with fat-free mass gains after physical training in women. Med Sci Sports Exerc 2011; 43(5):793-799. https://doi.org/10.1249/MSS.0b013e31820065.ea 3Strohbach CA, Scofield DE, Nindl BC, et al. Female recruits sustaining stress fractures during military basic training demonstrate differential concentrations of circulating IGF-I system components: a preliminary study. Growth Horm IGF Res 2012; 22(5):151-157. https://doi.org/10.1016/j.ghir.2012.04.007

Effects of heat treatment and simulated digestion on the properties and osteogenic activity of bovine lactoferrin

Lactoferrin (LF) is known to stimulate osteoblast proliferation and differentiation, potential to be applied in products improving skeletal health. However, LF is sensitive to thermal processing, and oral administration leads to hydrolysis in gastrointestinal tract, probably influencing the osteogenic activity. To determine the impacts of heat treatment, we explored the changes in secondary structure and surface hydrophobicity underlying aggregation along with surface charge alteration of bovine LF under four conditions commonly used in dairy production and found 72 °C/15 s, bringing the least structural alteration, was optimal to retain effect of LF promoting osteogenesis, while LF was completely deprived of the effect treated at 85 °C/10 min and 95 °C/10 min. In vitro adult and infant digestion models were established to identify the degradation of LF, and, despite impaired effect on osteoblast growth, LF hydrolysates from intestinal digestion stage presented stronger effect of boosting osteoblast differentiation independent of p38 and vitamin D receptor.

Megakaryocyte-bone cell interactions: lessons from mouse models of experimental myelofibrosis and related disorders.

Over the years, numerous studies demonstrated reciprocal communications between processes of bone marrow hematopoiesis and bone remodeling. Megakaryocytes, rare bone marrow cells responsible for platelet production, were demonstrated to be involved in bone homeostasis. Myelofibrosis, characterized by an increase in pleomorphic megakaryocytes in the bone marrow, commonly leads to the development of osteosclerosis. In vivo, an increase in megakaryocyte number was shown to result in osteosclerosis in GATA-1low, Nf-e2-/-, TPOhigh, Mplf/f;PF4cre, Lnk-/-, Mpig6b-/-, Mpig6bfl/fl;Gp1ba-Cr+/KI, and Pt-vWD mouse models. In vitro, megakaryocytes stimulate osteoblast proliferation and have variable effects on osteoclast proliferation and activity through soluble factors and direct cell-cell communications. Intriguingly, new studies revealed that the ability of megakaryocytes to communicate with bone cells is affected by the age and sex of animals. This mini-review summarizes changes seen in bone architecture and bone cell function in mouse models with an elevated number of megakaryocytes and the effects megakaryocytes have on osteoblasts and osteoclasts in vitro, and discusses potential molecular players that can mediate these effects.

HORMONE-ASSOCIATED METABOLIC DISORDERS OF THE ORAL CAVITY ORGANS IN WOMEN OF REPRODUCTIVE AGE

There is emerging evidence of a possible relationship between the oral cavity and reproductive organs. Recent studies suggest these functional relations. The aim of this review was to synthesize the available evidence on this relationship. Clinical observation established that sex hormones enhance gingival inflammation in periodontal healthy women during pregnancy and that periodontal condition is associated with variation of sex hormones in blood. Estrogen regulates DNA synthesis in human gingival epithelial cells and periodontal ligament, estrogen reduces down regulation of cytokines. Estrogen and progesterone affect the periodontium via appropriate receptors (estrogen receptor and progesterone receptor). They are localized in human periodontium, demonstrating that periodontal tissues are the target tissues for these hormones. Testosterone receptors are found in the periodontal tissues. It inhibits prostaglandin secretion and reduces interleukin production. At the same time testosterone stimulates osteoblast proliferation and differentiation, also enhances matrix synthesis by fibroblast, osteoblasts, and periodontal ligament. The role of testosterone in the formation of teeth is demonstrated in the paper. In females and males, in saliva there are sex steroid hormones. The study examined the entry mode of hormones into saliva. The results suggest that lipid soluble unconjugated steroids (estriol, testosterone, progesterone) enter saliva via intracellular route; the conjugated steroids (lipid insoluble (dehydroepiandrosterone, conjugated estrogens)) enter via the ‘tight junctions’ (infiltrations through the tight junctions between the acinar cells). Recent evidence indicates that organs of the oral cavity (salivary glands, periodontal tissues, oral epithelial cells mucus) produce ghrelin-hormone which affects organs of the reproductive system directly or indirectly via hypothalamic-pituitary-gonadal axis. In all these organs, there is an appropriate receptor. In conclusion, the organs of oral cavity and organs of reproductive system are functionally linked by sex steroid hormones and ghrelin, besides that periodont can influence ovaries by neuro-reflectory link.

Tanshinone IIA Regulates Osteoblast Differentiation and Promotes Fracture Healing via Mammalian Target of Rapamycin Complex 1 Signaling Pathway

This study assessed the effect and potential molecular mechanism of tanshinone IIA on fracture healing. Mice model with fracture were established. Digital radiographic photographic system was used to detect callus formation after treatment with tanshinone II A (Tan IIA) and alkaline phosphatase (ALP) staining analyzed ALP activity. Osteoblast proliferation was also measured. Western blot and Quantitative real-time PCR (qRT-PCR) measured osteogenic markers expression. Compared with control group, Tan IIA treatment could increase callus formation, stimulate osteoblast proliferation, osteogenic proteins and genes expression, and activate mTORC1 signaling pathway. However, Tan IIA’s effects were significantly inhibited after rapamycin treatment. Tan IIA regulates osteoblast differentiation by mTORC1 signaling and promotes intramembranous ossification in the process of callus formation, which accelerates bone healing.

Commentaries on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat?

Commentaries on Viewpoint: Fragile bones of elite cyclists: to treat or not to treat?

Involvement of PI3K/Akt/β-catenin signaling in schisandrin B-mitigated bone deterioration in an experimental rat model of estrogen deficiency.

Schisandrin B (SchB) has been reported to perform a wide range of biological functions, including antioxidant activity, anti-inflammatory activity and stimulation of osteoblast proliferation. However, the function and mechanism of SchB in ovariectomy (OVX)-induced osteoporosis are still unknown. The present study was designed to investigate the anti-osteoporotic activity of SchB in an experimental rat model of estrogen deficiency, which is usually used to mimic human postmenopausal osteoporosis (PMO). OVX rats were orally treated with low (10 mg/kg) or high (50 mg/kg) doses of SchB for 8 weeks. Bone metabolism-related markers were measured by ELISA. The levels of protein expression were determined by western blotting analysis. Hematoxylin and eosin (H&E) and safranin O staining were performed to analyze trabecular bone and cartilage degeneration. Tartrate-resistant acid phosphatase (TRAP) staining was used to evaluate osteoclast differentiation. SchB administration markedly increased serum Ca levels and bone Ca content and decreased urinary calcium excretion in OVX-operated rats. In addition, high-dosage SchB treatment blocked osteoclastogenesis and improved trabecular bone and cartilage degeneration in the tibia of OVX-operated rats. Furthermore, high-dosage SchB treatment dramatically elevated the protein expression of phospho-PI3K, phospho-Akt and β-catenin in OVX-operated rats. SchB exerted anti-osteoporotic activity in OVX-operated rats by accelerating the phosphorylation of PI3K and Akt, subsequently upregulating the expression of β-catenin.

Influencing Effect of Heat Therapy on Osteoblasts Growth and Differentiation Following Treatment with Bone Antiresorptive Drugs- An in vitro Study

Objectives: To find out the effect of mild heat shock on osteoblast proliferation and mineralisation following treatment with bisphosphonates. Materials and Methods: Cell culture of MC3T3 cells was performed in alpha minimum essential medium supplemented with 10% Foetal Calf Serum (FCS), 2 mmol L-glutamine and 100U/ml each of penicillin/streptomycin and were incubated at 37°C in humidified 5% CO2. The selected bisphosphonate drugs were administered, following which heat therapy was given by placing the flasks in a temperature-regulated water bath. The proliferation of osteoblast progenitors was measured using the methylene blue staining technique. Results: The results showed that mild heat-shock for 2 min at 42°C can stimulate proliferation of osteoblast progenitors, as well as bone nodule formation. In addition, mild heat-shock can reverse the action of bisphosphonate by stimulation of osteoblast proliferation and mineralisation. Conclusion: Mild heat-shock enhances cell differentiation and osteoblasts mineralisation following bisphosphonate treatment. Key words: Bisphosphonates, Heat-shock, Osteoblast, Osteoclast.

Osseointegration effects of local release of strontium ranelate from implant surfaces in rats

BackgroundNumerous studies have reported the beneficial effects of strontium on bone growth, particularly by stimulating osteoblast proliferation and differentiation. Thus, strontium release around implants has been suggested as one possible strategy to enhance implant osseointegration.AimThis study aimed to evaluate whether the local release of strontium ranelate (Sr-ranelate) from implants coated with mesoporous titania could improve bone formation around implants in an animal model.Materials and methodsMesoporous titania (MT) thin coatings were formed utilizing the evaporation induced self-assembly (EISA) method using Pluronic (P123) with or without the addition of poly propylene glycol (PPG) to create materials with two different pore sizes. The MT was deposited on disks and mini-screws, both made of cp Ti grade IV. Scanning electron microscopy (SEM) was performed to characterize the MT using a Leo Ultra55 FEG instrument (Zeiss, Oberkochen, Germany). The MT was loaded with Sr-ranelate using soaking and the drug uptake and release kinetics to and from the surfaces were evaluated using quartz crystal microbalance with dissipation monitoring (QCM-D) utilizing a Q-sense E4 instrument. For the in vivo experiment, 24 adult rats were analyzed at two time points of implant healing (2 and 6 weeks). Titanium implants shaped as mini screws were coated with MT films and divided into two groups; supplied with Sr-ranelate (test group) and without Sr-ranelate (control group). Four implants (both test and control) were inserted in the tibia of each rat. The in vivo study was evaluated using histomorphometric analyses of the implant/bone interphase using optical microscopy.ResultsSEM images showed the successful formation of evenly distributed MT films covering the entire surface with pore sizes of 6 and 7.2 nm, respectively. The QCM-D analysis revealed an absorption of 3300 ng/cm2 of Sr-ranelate on the 7.2 nm MT, which was about 3 times more than the observed amount on the 6 nm MT (1200 ng/cm2). Both groups showed sustained release of Sr-ranelate from MT coated disks. The histomorphometric analysis revealed no significant differences in bone implant contact (BIC) and bone area (BA) between the implants with Sr-ranelate and implants in the control groups after 2 and 6 weeks of healing (BIC with a p-value of 0.43 after 2 weeks and 0.172 after 6 weeks; BA with a p-value of 0.503 after 2 weeks, and 0.088 after 6 weeks). The mean BIC and BA values within the same group showed significant increase among all groups between 2 and 6 weeks.ConclusionThis study could not confirm any positive effects of Sr-ranelate on implant osseointegration.

Ceramics based on calcium phosphates substituted with magnesium ions for bone regeneration

AbstractIn this study, chemical precipitation methods were used to obtain ceramic materials doped with magnesium ions in order to improve the regeneration properties of materials used for tissue engineering. Two different ratios of magnesium oxide were used to dope the ceramic powder, more precisely 5% and 10%. The synthesized materials were characterized to determine the calcination temperature of the precursor powder by means of thermal analysis; to determine the mineralogical composition, X‐ray diffraction was employed and the scanning electron microscopy was used to determine the microstructure. To make use of these ceramics as biomaterials, viability and proliferation cell tests have been performed. Since synthetic materials have several limitations with regard to medical applications, the materials based on HAp substituted with Mg ions are a promising solution for the regeneration of bone defects because they have a similar bone structure. The presence of Mg in the material proves to be beneficial because this element plays an important role in bone cell regeneration, and more specifically, in stimulating osteoblast proliferation. The materials synthesized in this work present a suitable morphology for uses in bone regeneration because they offer to cells a friendly environment for growth and anchoring.

Aging negatively impacts the ability of megakaryocytes to stimulate osteoblast proliferation and bone mass.

Osteoblast number and activity decreases with aging, contributing to the age-associated decline of bone mass, but the mechanisms underlying changes in osteoblast activity are not well understood. Here, we show that the age-associated bone loss critically depends on impairment of the ability of megakaryocytes (MKs) to support osteoblast proliferation. Co-culture of osteoblast precursors with young MKs is known to increase osteoblast proliferation and bone formation. However, co-culture of osteoblast precursors with aged MKs resulted in significantly fewer osteoblasts compared to co-culture with young MKs, and this was associated with the downregulation of transforming growth factor beta. In addition, the ability of MKs to increase bone mass was attenuated during aging as transplantation of GATA1low/low hematopoietic donor cells (which have elevated MKs/MK precursors) from young mice resulted in an increase in bone mass of recipient mice compared to transplantation of young wild-type donor cells, whereas transplantation of GATA1low/low donor cells from old mice failed to enhance bone mass in recipient mice compared to transplantation of old wild-type donor cells. These findings suggest that the preservation or restoration of the MK-mediated induction of osteoblast proliferation during aging may hold the potential to prevent age-associated bone loss and resulting fractures.