Beta2-adrenergic receptor agonists reduce proliferation but not protein synthesis of periodontal fibroblasts stimulated with platelet-derived growth factor-BB

ObjectiveCatecholamines released from β-adrenergic neurons upon stress can interfere with periodontal regeneration. The cellular mechanisms, however, are unclear. Here, we assessed the effect of catecholamines on proliferation of periodontal fibroblasts.MethodsFibroblasts from the gingiva and the periodontal ligament were exposed to agonists of the β-adrenergic receptors; isoproterenol (ISO, non-selective β-adrenergic agonist), salbutamol (SAL, selective β₂-adrenergic receptor agonist) and BRL 37344 (BRL selective β₃-receptor agonist). Proliferation was stimulated with platelet-derived growth factor-BB (PDGF-BB). Pharmacological inhibitors and gene expression analysis further revealed β-adrenergic signalling.ResultsGingiva and periodontal ligament fibroblast express the β₂-adrenergic receptor. ISO and SAL but not BRL decreased proliferation of fibroblasts in the presence of PDGF-BB. The inhibitory effect of β-adrenergic signalling on proliferation but not protein synthesis in response to PDGF-BB was reduced by propranolol, a non-selective β-adrenergic antagonist.ConclusionsThese results suggest that β₂-receptor agonists can reduce the mitogenic response of periodontal fibroblasts. These data add to the compelling concept that blocking of β₂-receptor signalling can support tissue maintenance and regeneration.     

Autonomic receptors in the developing submandibular glands of neonatal rats

The functional maturation of the gland during the neonatal period involves specific temporal sequences in the appearance of autonomic membrane receptors and associated changes in the secretory response to receptor stimulation. The density and affinity of cholinergic muscarinic and of α- and β-adrenergic receptors were determined in the glands of 1-, 7-, 14- and 21-day-old rats, using the radioligands [³H]-quinuclidinyl benzylate, [³H]-prazosin and [³H]-dihydroalprenolol for the measurement of muscarinic cholinergic, α₁-adrenergic and β-adrenergic receptors, respectively. The density of binding sites followed similar developmental courses, whether expressed as $\text{pmol}\text{g}$ tissue or $\text{pmol}\text{g}$ protein. The densities ($\text{pmol}\text{g}$ protein) of β-adrenergic and muscarinic receptors were low in 1-day-old animals, but increased rapidly; adult levels were reached by 2 and 3 weeks of age, respectively. α₁-Adrenergic receptor binding was barely detectable at birth, increased slightly during the first week, dramatically by 14 days and approached adult levels by 21 days. The number of receptors per gland for these 3 autonomic receptor-binding sites increased 50 – 100-fold during the first 3 weeks of postnatal development. The affinities (K_D) for each of the three ligands did not differ significantly with age. Surprisingly, the α₂-adrenergic receptor density ($\text{[}{}^3\text{H]-p-}\text{aminoclonidine}$ binding) was high in 1-day-old animals and increased significantly during the first 2 weeks of life. The binding declined after 3 weeks and was nearly undetectable by 6 weeks. Frozen submandibular glands had markedly lower α₂-adrenergic binding compared to fresh glands. These findings suggest that each of the autonomic receptors in rat submandibular glands follows its own specific developmental pattern, and that the appearance of individual receptor types may correlate with the ability of the developing gland to respond to specific stimulants. A K⁺-release response can be elicited by epinephrine at 2 weeks of age, when α₁ receptor binding sites appear, while both the receptor binding sites and the response to muscarinic agonists are present at birth. As β-adrenergic receptor-binding sites may develop simultaneously with isoproterenol-stimulated adenylate-cyclase activity, it seems that receptor density is important in this response. The functional significance of the high density of α₂-adrenergic receptors in the submandibular gland of neonatal animals is not clear.     

Oxytocin Facilitates Dentinogenesis of Rat Dental Pulp Cells

IntroductionOxytocin (OT) is a neurohypophysial hormone that plays a role in lactation and parturition and exerts diverse biological actions via the OT receptor. Recently, several studies have reported that OT stimulates bone formation by osteoblasts in osteoporosis. We focused on OT and hypothesized that OT can stimulate the differentiation of odontoblasts as well as osteoblasts. The aim of this study was to verify whether OT is an essential factor in dentinogenesis; we examined the effects of OT on dentinogenesis using a long-term culture system of rat dental pulp cells.MethodsUsing a culture system of rat dental pulp cells with Otr knocked out by CRISPR-Cas9 genome editing, we examined the effects of OT on odontoblastlike cell differentiation as reflected by dentin formation.ResultsWe confirmed that OT stimulated mineralized nodule formation and the expression of both dentin sialoprotein and bone Gla protein messenger RNAs (mRNAs) in the culture system. Interestingly, the cultured cells treated with OT also exhibited an increase of both Wnt10a and Lef-1 mRNA. The Otr knockout cells showed inhibition of nodule formation and mRNA expression, and these phenomena remained despite OT treatment. These results indicate the following: OT regulates odontoblastlike cell differentiation via the OT receptor, it stimulates dentin formation, and the Wnt canonical pathway is closely related to these effects.ConclusionsThe present results suggest that OT can promote odontoblastlike cell differentiation, resulting in increased dentin formation, and that OT could be an important factor for dentinogenesis.     

Angiotensin II induces interleukin-6 synthesis in osteoblasts through ERK1/2 pathway via AT1 receptor

Background

Interleukin-6 (IL-6) is a potent stimulator of osteoclastic bone resorption. Osteoblast secretion of IL-6 plays an important role in the regulation of bone metabolism. Angiotensin II (Ang II) has been shown to regulate the expression of potent inflammatory factors, including MCP-1 and IL-6, by stimulating endothelia cells, vascular smooth muscle cells (VSMC) and monocytes. However, of the mechanism by which Ang II regulates IL-6 expression in osteoblasts is unknown.

Aims

The present study was designed to investigate the effect of Ang II on IL-6 expression in osteoblasts isolated from mice. The receptor(s) required and the potential role of extracellular signal-regulated kinase 1/2 (ERK1/2) activation in Ang II-induced IL-6 synthesis was also examined in these cells.

Methods

The osteoblasts were isolated from the calvaria of mice and cultured in α-MEM medium. IL-6 mRNA expression and protein synthesis was determined by qPCR and ELISA analyses. ERK1/2 kinase activation was determined by western blot.

Results

The results indicate that Ang II induced IL-6 mRNA expression and protein synthesis in cultured osteoblasts. However, these effects were abolished by pre-treatment with Ang II type 1 (AT1) receptor antagonist, losartan, and the ERK1/2 inhibitor, U0126, inhibited Ang II-mediated IL-6 expression and the phosphorylation of ERK1/2.

Conclusion

Ang II induces the synthesis of IL-6 in osteoblasts through activation of the ERK1/2 pathway via the AT1 receptor.     

Regulation of bone cell metabolism

Bone formation and resorption are normal physiologic processes. In pathologic states such as in periodontal disease or osteoporosis a shift in the balance of these two processes occurs, resulting in a net loss of mineralized tissue. Osteoclasts have historically been considered to be the primary bone resorbing cells, but current research has lead to the hypothesis that osteoblastic cells play an integral role in bone resorption as well. It appears that osteoblasts respond to bone resorbing agents via a series of intracellular responses after interactions with specific surface receptors. Two basic pathways involving different "second messengers" have been identified. The first pathway involves cyclic 3',5' adenosine monophosphate (cAMP) production and the second involves membrane phospholipids, diacylglycerol and calcium. A cytosolic enzyme, protein kinase C (PKC), has been shown to affect both cAMP as well as calcium fluxes and may act to regulate both these pathways. It is the purpose of this paper to discuss current studies and hypotheses concerning the nature of mechanisms involved in regulation of bone metabolism with emphasis on second messenger systems. Information of this nature is critical to the development of rationale regarding diagnosis, treatment and management of systemic and local pathoses of bone.     

Regulation of osteoclast function via Rho-Pkn3-c-Src pathways

BackgroundWnt signaling pathways are largely divided into the β-catenin-dependent canonical pathway and β-catenin-independent non-canonical pathways. The roles of Wnt signaling in bone metabolism have been extensively investigated.We previously attempted to clarify the roles of Wnt-non-canonical signaling in bone resorption and demonstrated that Wnt5a-receptor tyrosine kinase-like orphan receptor 2 (Ror2) signaling promoted osteoclast differentiation by enhancing RANK expression in osteoclast precursor cells. However, the roles of Wnt5a-Ror2 signaling in osteoclast function remain unclear.HighlightTrabecular bone mass was significantly greater in osteoclast-specific Ror2-deficient (Ror2^ΔOCL/ΔOCL) mice than in control mice due to the decreased bone-resorbing activity of osteoclasts. Wnt5a-Ror2 signaling activated Rho in osteoclasts via dishevelled-associated activator of morphogenesis 2 (Daam2). The expression of protein kinase N3 (Pkn3), a Rho effector, increased during osteoclast differentiation. Trabecular bone mass was significantly greater in Pkn3-deficient mice than in wild-type mice due to the decreased bone-resorbing activity of osteoclasts. Pkn3 bound to c-Src and Pyk2 in a Wnt5a-Ror2 signaling-dependent manner, thereby enhancing the kinase activity of c-Src in osteoclasts. The binding of Pkn3 to c-Src was essential for the bone-resorbing activity of osteoclasts.ConclusionWnt5a-Ror2 signaling promotes the bone-resorbing activity of osteoclasts by activating the Daam2-Rho-Pkn3-c-Src pathways. Pkn3 inhibitors, therefore, have potential as therapeutic agents for osteoporosis and bone destruction in inflammatory diseases.     

Recombinant bone morphogenetic protein-2 induces up-regulation of vascular endothelial growth factor and interleukin 6 in human pre-osteoblasts: role of reactive oxygen species

ObjectiveBone morphogenetic proteins (BMPs) and vascular endothelial growth factor (VEGF) have been reported in many studies to play a major role in the communication between endothelial cells and osteoblasts. The inflammatory reaction and relative hypoxia at the site of bone injury are the first stages of the fracture repair. rhBMP-2 has been used extensively in spinal fusion and reconstruction of maxillofacial bone defects with main complication is the formation of seroma. The aim of this study was to test whether rhBMP-2 regulates the expression of the angiogenic and inflammatory mediators in pre-osteoblasts via generating reactive oxygen species (ROS).MethodsrhBMP-2 effect on angiogenesis and inflammatory genes was assessed using normal human osteoblasts (NHOst). Angiogenesis genes were measured using angiogenic PCR array. VEGF and IL6 production were analysed using ELISA kit and real-time PCR. ROS production was assessed using dihydroethidine and dichlorofluorescein staining and lipid peroxidation. HIF-1α immunoreactivity was performed using immunofluorescence staining.ResultsThere was an increase in the pro-angiogenic and -inflammatory genes as well as VEGF and IL6 protein expression in NHOst by rhBMP-2. This increase in VEGF and IL6 was blocked by the ROS scavenger N-acetyl cysteine (NAC).ConclusionThe regulatory effect of rhBMP-2 on angiogenesis and inflammation is mediated through a ROS-dependent mechanism, which involves upregulation of crucial angiogenic and inflammatory mediators such as VEGF and IL6. These findings highlight the need for future studies to identify new therapeutic targets downstream from rhBMP-2 to potentiate its beneficial effect or limit its complications such as seroma formation.     

Roles of Collagen Molecules in Growth and Differentiation of Human Osteoblasts

Collagen is the most abundant organic component of bone. It constitutes a superfamily of extracellular matrix proteins whose primary function is structural. The major collagenous component of bone is type I collagen, but types III, V, and X collagens are also found in bone tissue. Recently it was reported that collagen is essential for the growth and differentiation of various kinds of cell including osteoblasts. In order to investigate the function of the respective collagen components in the growth and differentiation of osteoblasts, we employed human osteoblast-like MG-63 cells and normal human osteoblasts, as well as human bone marrow stem cells; cultured them in the presence or absence of ascorbic acid 2-phosphate (Asc 2-P) and/or vitamin D₃ (VD₃); and examined the relationship between specific collagen types and the growth and differentiation of the cells. The stimulation of cell proliferation by the addition of Asc 2-P or epidermal growth factor is closely associated with an increase in the synthesis of type III collagen. The stimulation of osteoblast differentiation by the addition of VD₃ resulted in growth retardation of the cells. The inhibition of type I or III collagen synthesis by adding the respective siRNAs attenuated the effects of these agents. Employing type I or III collagen as a substratum also regulated the growth and/or differentiation of human osteoblasts.This review reveals that type I and III collagens function as regulatory molecules for the differentiation and proliferation of human osteoblastic cells, and discusses the possibility that collagen metabolism is a possible new target for the treatment of osteoporosis.     

Blockade of sympathetic β-receptors inhibits Porphyromonas gingivalis-induced alveolar bone loss in an experimental rat periodontitis model

Introduction

Periodontal disease is characterised by alveolar bone loss. Some studies have suggested the involvement of sympathetic nervous system in the deterioration of periodontal disease. Noradrenaline, released from sympathetic nerve terminals due to various stimuli, binds to specific adrenergic receptors on immune cells. Recently, we reported that restraint stress augmented the alveolar bone loss induced by Porphyromonas gingivalis infection. In this study, we investigated the effects of the β-blocker (propranolol) on alveolar bone loss induced by P. gingivalis infection to examine the involvement of sympathetic nerves in periodontal breakdown.

Methods

Sprague-Dawley rats were treated as follows: saline injection (Group A), propranolol injection (Group B), saline injection and oral challenge with P. gingivalis (Group C), and propranolol injection and oral challenge with P. gingivalis (Group D). Horizontal alveolar bone loss was evaluated by measuring the distance between the cemento-enamel junction and the alveolar bone crest. Specimens from periodontal tissue were evaluated by staining with hematoxylin-eosin and tartrate-resistant acid phosphatase.

Results

Blockade of β-receptors in periodontal tissue by propranolol inhibited osteoclast differentiation and prevented alveolar bone loss induced by P. gingivalis infection. Histological study revealed that the number of osteoclasts detected was proportional to the level of bone loss.

Conclusions

These results indicate that the sympathetic nervous system is involved in the development of periodontitis and suggest that sympathetic signal modulation with β-blockers enables the control of alveolar bone mass metabolism.     

1α,25-Dihydroxyvitamin D3 inhibits osteoblastic differentiation of mouse periodontal fibroblasts

ObjectivePeriodontal ligament (PDL) is a non-mineralized tissue connecting cementum and alveolar bone. Recent studies have suggested that periodontal fibroblasts can differentiate into mineralized tissue-forming cells such as osteoblasts and cementoblasts. We elucidated the immunolocalization of vitamin D receptor (VDR) and the effects of vitamin D₃ (VD₃) on mouse periodontal fibroblasts to clarify the role of VDR and VD₃ in the differentiation of periodontal fibroblasts.DesignImmunohistochemical analysis using anti-VDR antibody was performed in paraffin sections of mouse mandibles at E13, E14, E17, P10, and P35. The roles of VD₃ in osteoblastic differentiation and mineralization were estimated by alkaline phosphatase (ALP) and alizarin red (AR) staining. In addition, the mRNA expression of osteoblast markers and mineralization inhibitors was examined by real-time PCR.ResultsAt the bud, cap and early bell stages, immunoreactivity for VDR was scarcely seen in the cells of dental follicles. Labelling was detected in the nuclei of cemetoblasts, periodontal fibroblasts and osteoblasts during root formation. VD₃ inhibited ALP activity and AR-positive mineralized nodule formation of periodontal fibroblasts in osteogenic culture medium. Real-time PCR revealed that VD₃ down-regulated the levels of osteoblast markers. In contrast, VD₃ significantly up-regulated the level of periodontal ligament associated protein (PLAP)-1, a negative regulator of osteoblastic differentiation.ConclusionThese results suggest that VD₃ negatively regulates the osteoblastic differentiation of mouse periodontal fibroblasts and prevents the periodontal ligament from mineralization via increase of PLAP-1.     

Td92, an outer membrane protein of Treponema denticola,induces osteoclastogenesis via prostaglandin E2‐mediated RANKL/osteoprotegerin regulation

Kim M, Jun H‐K, Choi B‐K, Cha J‐H, Yoo Y‐J. Td92, an outer membrane protein of Treponema denticola, induces osteoclastogenesis via prostaglandin E₂‐mediated RANKL/osteoprotegerin regulation. J Periodont Res 2010; 45: 772–779. © 2010 John Wiley & Sons A/S Background and Objective: Periodontitis is a chronic inflammatory disease of the periodontium that causes significant alveolar bone loss. Osteoclasts are bone‐resorbing multinucleated cells. Osteoblasts regulate osteoclast differentiation by expression of RANKL and osteoprotegerin (OPG). Td92 is a surface‐exposed outer membrane protein of Treponema denticola, a periodontopathogen. Although it has been demonstrated that Td92 acts as a stimulator of various proinflammatory mediators, the role of Td92 in alveolar bone resorption remains unclear. Therefore, in this study, we investigated the role of Td92 in bone resorption. Material and Methods: Mouse bone marrow cells were co‐cultured with calvariae‐derived osteoblasts in the presence or absence of Td92. Osteoclast formation was assessed by TRAP staining. Expressions of RANKL, osteoprotegerin (OPG) and prostaglandin E₂ (PGE₂) in osteoblasts were estimated by ELISA. Results: Td92 induced osteoclast formation in the co‐cultures. In the osteoblasts, RANKL and PGE₂ expressions were up‐regulated, whereas OPG expression was down‐regulated by Td92. The addition of OPG inhibited Td92‐induced osteoclast formation. The prostaglandin synthesis inhibitors NS398 and indomethacin were also shown to inhibit Td92‐induced osteoclast formation. The effects of Td92 on the expressions of RANKL, OPG and PGE₂ in osteoblasts were blocked by NS398 or indomethacin. Conclusion: These results suggest that Td92 promotes osteoclast formation through the regulation of RANKL and OPG production via a PGE₂‐dependent mechanism.     

能量代谢在成骨和破骨细胞中的研究

骨稳态的维持对于骨骼健康极为重要,如果骨形成与骨吸收的平衡被打破,容易造成骨量丢失、骨质疏松等多种骨骼疾病。近期越来越多的研究表明,能量代谢失调,例如葡萄糖代谢异常、氨基酸代谢受阻以及脂代谢缺陷等等,都会对骨稳态的平衡造成破坏,从而引起或是加剧导致骨量减少和骨质疏松性骨折等疾病。本文将对能量代谢在成骨细胞以及破骨细胞中的研究进展进行总结分析,深入了解能量代谢,特别是葡萄糖代谢在骨稳态维持中对成骨、破骨细胞分化和功能的关键调控作用,为了解、治疗骨质疏松等骨相关疾病提供指导。     

What is the function of osteocalcin?

BackgroundOsteocalcin is the most abundant non-collagenous protein in bone and is specifically expressed in osteoblasts. Previous studies using osteocalcin-deficient (Ocn^–/–) mice demonstrated that osteocalcin inhibits bone formation, and serum uncarboxylated osteocalcin functions as a hormone that improves glucose metabolism, induces testosterone synthesis in the testes, and maintains muscle mass. Furthermore, the relationship between serum osteocalcin and glucose metabolism or cardiovascular risk in humans has been reported. However, new Ocn^–/– mice exhibited different phenotypes.HighlightBone volume, formation, and resorption were normal in the new Ocn^–/– mice. The orientation of collagen fibers was parallel to the bone longitudinal direction and the size of apatite crystals was normal, but the c-axis of apatite crystals was random and bone strength was reduced in new Ocn^–/– mice. Glucose metabolism, testosterone synthesis, and muscle mass were normal in new Ocn^–/– mice. Exercise improved glucose metabolism and increased bone formation, leading to an increase in the serum osteocalcin level, which is a marker for bone formation.ConclusionContrary to previous findings, new Ocn^–/– mice revealed that osteocalcin has no function in the regulation of bone quantity, but instead, functions to direct the parallel alignment of the c-axis of apatite crystals with collagen fibrils. Moreover, it has no physiological function as a hormone that regulates glucose metabolism, testosterone synthesis, or muscle mass. These controversial phenotypes require further investigation. The relationship of serum osteocalcin with glucose metabolism or cardiovascular risk suggests the importance of exercise for their improvement.     

Integrin mediated attachment of periodontal ligament to titanium surfaces

ObjectiveReducing the force between the implant and the bone by recapitulating a similar matrix has the potential to reduce implant failure. To begin to pursue the goal of creating a periodontal ligament interface between a dental implant and bone, the mechanism of cellular attachment to dental implant surfaces must be characterized.MethodsIn this study we examined the role of integrin receptors in the attachment of periodontal ligament fibroblasts to titanium surfaces utilized on dental implants; those surfaces included smooth polished titanium, acid pickled titanium, ground titanium, sandblasted and acid etched titanium, non-oxidized titanium that has been sandblasted and acid etched, hydroxyapatite coated titanium, titanium plasma sprayed or uncoated titanium. For these studies integrin mediated fibroblast attachment was blocked by the integrin blocking peptide GRGDSP or anti-integrin β1 antibody or a combination of the two. Quantitation of periodontal ligament fibroblast attachment was completed by counting cells on the various implant surfaces after culturing in vitro for 24 h with and without the integrin receptor blockers.ResultsAntibody and peptide treatment significantly reduced the number of fibroblasts cells attached to the various implant surfaces but this effect varied significantly depending on the surface. Moreover, increased levels of peptide further decreased fibroblasts attachment in a dose dependent manner.SignificanceBlocking studies suggest first, that integrin receptors function in periodontal ligament attachment to titanium surfaces and second, that different integrin subunits are important in attachment to a particular surface.     

Lactoferrin inhibits infection-related osteoclastogenesis without interrupting compressive force-related osteoclastogenesis

BackgroundControl of periodontal tissue inflammation during orthodontic treatment is very important in achieving a favourable therapeutic goal. We previously demonstrated that orally applied bovine lactoferrin (bLF) inhibited LPS-induced bone resorption but not orthodontic force-induced tooth movement in vivo. This study is designed to examine the underlying mechanism of it.MethodsWe examined the inhibitory effects of bLF on the expression of RANKL, OPG, TNF-α and COX-2 in osteoblasts loaded with compressive stress (CS) in comparison with LPS stimulated osteoblasts. Formation of osteoclasts was evaluated by co-culture system.ResultsBoth CS- and LPS-applications upregulated COX-2 and RANKL but downregulated OPG. TNF-α was upregulated in LPS-stimulated osteoblasts but downregulated in CS-loaded osteoblasts. NS398 (a specific inhibitor of COX-2) significantly inhibited CS-induced RANKL-upregulation but not LPS-induced RANKL upregulation, indicating a critical role of COX-2/PGE₂ pathway in CS-induced osteoclastogenesis. bLF significantly downregulated LPS-induced upregulation of RANKL and eliminated OPG suppression but not affected in CS-induced changes. Moreover, bLF significantly decreased LPS-induced osteoclast formation, whereas bLF had no effect on PGE₂-induced osteoclast formation.ConclusionsbLF can effectively suppress harmful bone destruction associated with periodontitis without inhibiting bone remodelling by CS-loading. Therefore, oral administration of bLF may be highly beneficial for control of periodontitis in orthodontic patients.     

Molecular mechanisms for bone resorption by gingipains: Degradation of osteoprotegerin by lysine-specific gingipain is a key factor for enhanced osteoclastogenesis

BackgroundPeriodontitis is a chronic inflammatory disease accompanied by alveolar bone loss. Porphyromonas gingivalis, which plays a key role in the etiology of periodontitis, produces cysteine proteases called gingipains to promote proteolysis. Gingipains are classified into two groups based on their cleavage site specificity, specifically arginine-specific gingipains (Rgps) and lysine-specific gingipains (Kgps).HighlightWe found that osteoclast differentiation induced by active vitamin D₃, Toll-like receptor ligands including lipopolysaccharide, and inflammatory cytokines such as tumor necrosis factor-α and interleukin-1β was enhanced by a secreted Kgp in co-cultures of mouse osteoblasts and bone marrow cells, whereas RgpB had no effect on osteoclast differentiation under the same experimental conditions. The effect of Kgp on osteoclast differentiation was completely blocked by an inhibitor of Kgp. Further, osteoprotegerin (OPG), a protein that regulates osteoclast differentiation, was degraded by Kgp. Kgp-mediated osteoclast differentiation was not observed in co-cultures of OPG-deficient osteoblasts and bone marrow cells.ConclusionOur data suggests that degradation of OPG by Kgp is a crucial event in the progression of osteolysis in periodontitis.     

The role of Vitamin D as an adjunct for bone regeneration: A systematic review of literature

Background and objectivesIn spite of bone’s healing capacity, critical-size bone defect regeneration and peri-implant osseointegration are challenging. Tissue engineering provides better outcomes, but requires expensive adjuncts like stem cells, growth factors and bone morphogenic proteins. Vitamin D (Vit.D) regulates calcium and phosphorus metabolism, and helps maintain bone health. Vit.D supplements in deficient patients, accentuates bone healing and regeneration. Therefore the aim of this systematic review was to evaluate the role of adjunctive Vit.D on bone defect regeneration.MethodsComprehensive database search of indexed literature, published between January 1990 and June 2022, was carried out. English language articles fulfilling inclusion criteria (clinical/in vivo studies evaluating bone regeneration including osseointegration and in vitro studies assessing osteogenic differentiation, with adjunct Vit.D) were identified and screened.ResultsDatabase search identified 384 titles. After sequential title, abstract and full-text screening, 23 studies (in vitro – 9/in vivo – 14) were selected for review. Vit.D as an adjunct with stem cells and osteoblasts resulted in enhanced osteogenic differentiation and upregulation of genes coding for bone matrix proteins and alkaline phosphatase. When used in vivo, Vit.D resulted in early and increased new bone formation and mineralization within osseous defects, and better bone implant contact and osseointegration, around implants. Adjunct Vit.D in animals with induced systemic illnesses resulted in bone defect regeneration and osseointegration comparable to healthy animals. While systemic and local administration of Vit.D resulted in enhanced bone defect healing, outcomes were superior with systemic route.ConclusionsBased on this review, adjunct Vit.D enhances bone defect regeneration and osseointegration. In vitro application of Vit.D to stem cells and osteoblasts enhances osteogenic differentiation. Vit.D is a potentially non-invasive and inexpensive adjunct for clinical bone regeneration and osseointegration. Long term clinical trials are recommended to establish protocols relating to type, dosage, frequency, duration and route of administration.     

Roles of non-canonical Wnt signaling pathways in bone resorption

Background

Wnt is a cytokine involved in the development and homeostasis of various organs. In 2001, low-density lipoprotein receptor-related protein 5 (LRP5) was identified as the gene responsible for osteoporosis pseudoglioma syndrome and regulation of bone mass. Since LRP5 belongs to the low-density lipoprotein receptor family, this finding garnered the attention of researchers in the bone, mineral, and Wnt research fields. The role of Wnt in bone formation and resorption has since been extensively studied. Wnt/β-catenin signals are known to play a role in bone resorption. The activation of these signals in osteoblast lineage cells such as osteoblasts and osteocytes induces the expression of osteoprotegerin and then inhibits osteoclast formation.

Circulating adrenaline released by sympathoadrenal activation elicits acute vasodilatation in the rat masseter muscle

The present study was designed to examine the effects of circulating catecholamines released by sympathoadrenal system on the haemodynamics of the masseter muscle in deeply urethane-anaesthetized, artificially ventilated, cervically vagotomized and sympathectomized rats. Intravenous administration of adrenaline induced a biphasic change of blood flow in the masseter muscle (MBF). The change of blood flow showed an initial marked increase and successive slight decrease in a dose-dependent manner (0.01-1 μg/kg). The administration of noradrenaline had no significant effect on the MBF. The increase in the MBF evoked by exogenously applied adrenaline was markedly reduced by the intravenous administration of propranolol (100 μg/kg), whereas pretreatment with either hexamethonium (10 mg/kg), atropine (100 μg/kg), or phentolamine (1 mg/kg) failed to affect the MBF increase. Electrical stimulation of splanchnic nerve (SPLN) preganglionic neurones projecting to the adrenal medulla elicited frequency-dependent (1-20 Hz) increases in the MBF. The intravenous administration of the β₂-adrenergic receptor selective antagonist, ICI 118551 (0.5 mg/kg), almost abolished the MBF increase induced by SPLN stimulation, but pretreatment with the β₁-adrenergic receptor selective antagonist, atenolol (1 mg/kg), had no effect on this response. The results of the present study indicate that circulating adrenaline elicits acute vasodilatation through a β-adrenergic mechanism in the rat masseter muscle. Vascular β₂-adrenergic receptors in the masseter muscle may be activated preferentially by adrenaline released from the adrenal medulla, suggesting that the sympathoadrenal system is involved in the marked MBF increase during sympathoexcitation.