Dose- and time-dependent effects of recombinant human bone morphogenetic protein-2 on the osteogenic and adipogenic potentials of alveolar bone-derived stromal cells

Park J‐C, Kim J.C, Kim B‐K, Cho K‐S, Im G‐I, Kim B‐S, Kim C‐S. Dose‐ and time‐dependent effects of recombinant human bone morphogenetic protein‐2 on the osteogenic and adipogenic potentials of alveolar bone‐derived stromal cells. J Periodont Res 2012; 47: 645–654. © 2012 John Wiley & Sons A/S Background and Objective: Recombinant human bone morphogenetic protein‐2 (rhBMP‐2) is a well‐known growth factor that can induce robust bone formation, and recent studies have shown that rhBMP‐2‐induced osteogenesis is closely related to adipogenesis. The aim of the present study was to determine the dose‐ and time‐dependent effects of rhBMP‐2 on the osteogenic and adipogenic differentiation of human alveolar bone‐derived stromal cells (hABCs) in vivo and in vitro. Material and Methods: hABCs were isolated and cultured, and then transplanted using a carrier treated either with or without rhBMP‐2 (100 μg/mL) into an ectopic subcutaneous mouse model. Comprehensive histologic and histometric analyses were performed after an 8‐wk healing period. To further understand the dose‐dependent (0, 10, 50, 200, 500 and 1000 ng/mL) and time‐dependent (0, 3, 5, 7 and 14 d) effects of rhBMP‐2 on osteogenic and adipogenic differentiation, in vitro osteogenic and adipogenic differentiation of hABCs were evaluated, and the expression of related mRNAs, including those for alkaline phosphatase, osteocalcin, bone sialoprotein, peroxisome‐proliferator‐activated receptor gamma‐2 and lipoprotein lipase, were assessed using quantitative RT‐PCR. Results: rhBMP‐2 significantly promoted the osteogenic and adipogenic differentiation of hABCs in vivo, and gradually increased both the osteogenic and adipogenic potential in a dose‐ and time‐dependent manner with minimal deviation in vitro. The expression of osteogenesis‐ and adipogenesis‐associated mRNAs were concomitantly up‐regulated by rhBMP‐2. Conclusion: The findings of the present study showed that rhBMP‐2 significantly enhanced the adipogenic as well as the osteogenic potential of hABCs in dose‐ and time‐dependent manner. The control of adipogenic differentiation of hABCs should be considered when regenerating the alveolar bone using rhBMP‐2.     

Effect of leptin on differentiation of human dental stem cells

Oral Diseases (2011) 17 , 662–669 Objectives: Mesenchymal stem cells (MSCs) were identified in adult human periodontal ligament and dental pulp that are considered as potential stem cell sources for future clinical applications in dentistry. Leptin is known as an important regulator of mesenchymal differentiation. The objective of this study was to elucidate the role of leptin on proliferation and differentiation of dental MSCs. Materials and methods: Enhancement of cemento/odontoblastic differentiation of dental stem cells by leptin was confirmed by alizarin red S staining and alkaline phosphatase activity staining. In contrast, leptin reduced adipogenesis in both dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) confirmed by oil red O staining and RT‐PCR. The expression of adipogenic markers, lipoprotein lipase and proliferator‐activated receptor γ2 (PPARγ2), were suppressed in PDLSCs incubated on media supplemented with leptin for 2 weeks. Results: Leptin had a relatively stronger osteogenesis promoting effect and adipogenesis suppressing effect in PDLSCs than in DPSCs. Conclusions: Collectively, leptin had a relatively stronger promoting effect on cemento/odontoblastic differentiation and a suppressing effect on adipogenesis in PDLSCs than in DPSCs. This study has provided evidence that leptin acts as an important modulator of dental MSCs differentiation.     

In vivo monitoring of the bone healing process around different titanium alloy implant surfaces placed into fresh extraction sockets

Objectives

Increasing surface roughness and coating with tricalcium phosphate of titanium and titanium alloy implants has been proposed to provide better rates of osseointegration. However, how these changes in surface topography and chemistry influence the osseointegration process of immediate implants placed in fresh extraction sockets is unclear. This study investigated the influence of three clinically employed implant surfaces on the early bone healing events in vivo.

Methods

Machined smooth implants were milled from grade 5 Ti6Al4V titanium. Surfaces were moderately roughened by grit blasting, which were then coated with tricalcium phosphate. Implants were placed into freshly extracted incisor sockets of mandibles of normal Wistar rats and left for 1, 3 and 9 weeks. Healing bone tissue around the implants was examined by histochemistry and immunocytochemistry to localise PCNA proliferative cells, and osteoblast differentiation markers osteopontin and osteocalcin. Positive synthesising cells were counted using image analysis.

Results

Histology indicated no differences in the amount or pattern of bone formation within the healing tissue surrounding the different implant surfaces. Bone healing occurred predominantly on exposed bone surfaces (distance osteogenesis) and not on the implant surface (contact osteogenesis). No differences were observed in the number or timing of PCNA, osteopontin and osteocalcin positive cells within the bone healing tissue around each of the implant analysed.

Conclusion

For immediately placed implants, the surface modifications investigated appeared to have little influence on the activity of bone forming cells surrounding the implant, probably due to the high level of distance osteogenesis seen within this scenario.

Clinical significance

For immediate placement of implants into fresh extraction sockets, titanium implants with roughened surfaces and coating with tricalcium phosphate have negligible influence in accelerating the early bone healing events of osseointegration.     

EGCG通过ERK1/2信号通路对BMMSCs成脂分化能力的影响

目的 研究表没食子儿茶素没食子酸酯（EGCG）对骨髓间充质干细胞（BMMSCs）增殖及成脂分化的影响并探讨其中潜在的分子机制及信号通路。 方法 采用MTT分析EGCG对BMMSCs增殖的影响。通过油红O染色分析EGCG对细胞成脂分化能力的影响。应用实时荧光定量RT-PCR分析PPARγ、C/EBPα及C/EBPβ等基因的表达变化。同时,运用Western blot验证ERK1/2信号通路是否参与EGCG抑制BMMSCs成脂分化进程。 结果 低浓度EGCG（1~10 mmol/L）对BMMSCs细胞生长无明显作用,但高浓度EGCG（20~40 mmol/L）显著抑制细胞的增殖反应。通过抑制PPARγ、C/EBPα及C/EBPβ等关键转录因子的表达,EGCG明显抑制BMMSCs的成脂分化能力。ERK1/2通路在EGCG抑制BMMSCs成脂分化进程中扮演重要角色。 结论 EGCG通过ERK1/2通路抑制BMMSCs的成脂分化能力。     

Effect of Porphyromonas gingivalis Lipopolysaccharide on Bone Marrow Mesenchymal Stem Cell Osteogenesis on a Titanium Nanosurface

Background: Titanium (Ti) dental implants have been widely used for prosthetic reconstruction of dentition. Unfortunately, peri‐implantitis can result in failure of dental implant osseointegration. Lipopolysaccharide (LPS) acts as a chronic inflammatory stimulus and maintains peri‐implant inflammation, worsening the prognosis for implant osseointegration. The purpose of this study is to determine the effects of 10 M NaOH‐modified Ti surface with nanonetwork structure on the proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMMSCs) in the context of Porphyromonas gingivalis LPS exposure. Methods: Titanium disks treated with 10 M NaOH solution and control were incubated with BMMSCs and exposed to P. gingivalis LPS (0, 0.1, or 1 μg/mL). The effects of the modified nanonetwork structure on osteogenic differentiation of rat BMMSCs were evaluated in the context of different concentrations of P. gingivalis LPS exposure. Results: Rat BMMSCs on the 10 M NaOH‐modified Ti surface with nanonetwork structure had higher levels of osteogenesis‐related gene expression and significantly greater cell proliferation, alkaline phosphatase activity, and extracellular matrix deposition and mineralization than cells on the untreated Ti surfaces, in all the groups with different doses of P. gingivalis LPS exposure. Conclusion: The 10 M NaOH‐modified Ti surface with nanonetwork structure has better endotoxin tolerance under P. gingivalis LPS exposure than the non‐modified surface.     

Fluid Shear Stress Stimulates Osteogenic Differentiation of Human Periodontal Ligament Cells via the Extracellular Signal‐Regulated Kinase 1/2 and p38 Mitogen‐Activated Protein Kinase Signaling Pathways

Background: Fluid shear stress (FSS) is a major type of mechanical stress that is loaded on human periodontal ligament cells (hPDLCs) during mastication and orthodontic tooth movement. This study aims to clarify the effect of FSS on the osteogenic differentiation of hPDLCs and to further verify the involvement of mitogen‐activated protein kinase (MAPK) signaling in this process. Methods: After isolation and characterization, hPDLCs were subjected to 2‐hour FSS at 12 dynes/cm², and cell viability, osteogenic gene mRNA expression, alkaline phosphatase (ALP) activity, secretion of Type I collagen (COL‐I), and calcium deposition were assayed. The levels of phosphorylated p38 and phosphorylated extracellular signal‐regulated kinase 1/2 (ERK1/2) in response to FSS were detected by Western blot, and the involvement of ERK1/2 and p38 MAPK signaling pathways in hPDLC osteogenesis under FSS was investigated using the specific MAPK inhibitors U0126 (2Z,3Z)‐2,3‐bis[amino(2‐aminophenylthio)methylene]succinonitrile,ethanol) and SB203580 (4‐[4‐(4‐fluorophenyl)‐2‐(4‐[methylsulfinyl]phenyl)‐1H‐imidazol‐5‐yl]pyridine). Results: The application of FSS on hPDLCs induced an early morphologic change and rearrangement of filamentous actin. ALP activity, messenger RNA (mRNA) levels of osteogenic genes, COL‐I, and osteoid nodules were significantly increased by FSS. Moreover, ERK1/2 and p38 were activated in different ways after FSS exposure. U0126 and SB203580 completely blocked the FSS‐induced increases in ALP activity and osteogenic gene mRNA expression and osteoid nodules formation. Conclusions: FSS is an effective approach for stimulating osteogenic differentiation of hPDLCs. The ERK1/2 and p38 MAPK signaling pathways are involved in this cellular process.     

人牙周膜干细胞的多向分化潜能实验

目的:体外培养分离人牙周膜干细胞(hPDLSC),做成骨诱导和成脂诱导实验。方法:取新鲜拔除正畸牙的牙周膜为材料制成组织块,加入培养液以组织块法分离培养,免疫磁珠法筛选人牙周膜干细胞,加入成骨诱导液诱导牙周膜干细胞成骨,加入成脂诱导液诱导牙周膜干细胞向脂肪细胞转化。结果:成功筛选出人牙周膜干细胞,成骨及成脂诱导成功。结论:免疫磁珠法是筛选人牙周膜干细胞的有效方法,牙周膜干细胞可以向成骨细胞和脂肪细胞分化。     

Effect of microgrooves and fibronectin conjugation on the osteoblast marker gene expression and differentiation

PURPOSE

To determine the effect of fibronectin (FN)-conjugated, microgrooved titanium (Ti) on osteoblast differentiation and gene expression in human bone marrow-derived mesenchymal stem cells (MSCs).

MATERIALS AND METHODS

Photolithography was used to fabricate the microgrooved Ti, and amine functionalization (silanization) was used to immobilize fibronectin on the titanium surfaces. Osteoblast differentiation and osteoblast marker gene expression were analyzed by means of alkaline phosphatase activity assay, extracellular calcium deposition assay, and quantitative real-time PCR.

RESULTS

The conjugation of fibronectin on Ti significantly increased osteoblast differentiation in MSCs compared with non-conjugated Ti substrates. On the extracellular calcium deposition assays of MSCs at 21 days, an approximately two-fold increase in calcium concentration was observed on the etched 60-µm-wide/10-µm-deep microgrooved surface with fibronectin (E60/10FN) compared with the same surface without fibronectin (E60/10), and a more than four-fold increase in calcium concentration was observed on E60/10FN compared with the non-etched control (NE0) and etched control (E0) surfaces. Through a series of analyses to determine the expression of osteoblast marker genes, a significant increase in all the marker genes except type I collagen α1 mRNA was seen with E60/10FN more than with any of the other groups, as compared with NE0.

CONCLUSION

The FN-conjugated, microgrooved Ti substrate can provide an effective surface to promote osteoblast differentiation and osteoblast marker gene expression in MSCs.     

Oxidative nanopatterning of titanium surfaces promotes production and extracellular accumulation of osteopontin

The bone-biomaterial interface has been characterized by layers of afibrillar extracellular matrix (ECM) enriched in non collagenous proteins, including osteopontin (OPN), a multifunctional protein that in bone controls cell adhesion and ECM mineralization. Physical and chemical aspects of biomaterial surfaces have been demonstrated to affect cell-ECM-substrate interactions. The present paper described the ability of oxidative nanopatterning of titanium (Ti) surfaces to control extracellular OPN deposition in vitro. Ti discs were chemically treated by a mixture of H2SO4/H2O2 for either 30 min [Nano(30') Ti] or 4 h [Nano(4h) Ti]. Non-etched Ti discs were used as control. Primary osteogenic cells derived from newborn rat calvarial bone were plated on control and etched Ti and grown under osteogenic conditions up to 7 days. High resolution scanning electron microscopy revealed that treated Ti discs exhibited a nanoporous surface and that areas of larger nanopits were noticed only for Nano(4h) Ti. Large extracellular OPN accumulation were detectable only for Nano(4h) Ti, which was associated with OPN-positive cells with typical aspects of migrating cells. At day 3, quantitative results in terms of areas of OPN labeling were as follows: Nano(4h) Ti > Nano(30') Ti > Control Ti. In conclusion, chemically nanostructured Ti surfaces may support the enhancement of endogenous extracellular OPN deposition by osteogenic cells in vitro depending on the etching time, a finding that should be taken into consideration in strategies to biofunctionalize implant surfaces with molecules with cell adhesion capacity.     

不同周龄大鼠骨髓基质干细胞成骨与成脂分化平衡的研究

目的研究不同周龄大鼠骨髓基质干细胞成骨与成脂肪能力。方法不同周龄(幼年组:2周,成年组:3个月,老年组:18个月)大鼠骨髓基质干细胞原代培养,成骨诱导分化,矿化结节染色,计算矿化率。成脂肪诱导分化,显微镜下观察脂肪滴及检测油红-O染色阳性细胞率。结果全骨髓细胞贴壁的方法得到大鼠骨髓基质干细胞,幼年组成骨分化的矿化率最高,老年组最低。成脂肪诱导油红-O染色阳性率老年组最高,幼年组最低。结论随着年龄的增长骨髓基质干细胞成骨能力减弱,成脂肪能力增强。     

The role of sirtuin 1 in osteoblastic differentiation in human periodontal ligament cells

Lee Y‐M, Shin S‐I, Shin K‐S, Lee Y‐R, Park B‐H, Kim E‐C. The role of sirtuin 1 in osteoblastic differentiation in human periodontal ligament cells. J Periodont Res 2011; 46: 712–721. © 2011 John Wiley & Sons A/S Background and Objective: Activation of sirtuin 1 (SIRT1) promotes the differentiation of keratinocytes and mesenchymal stem cells, but inhibits the differentiation of muscle and fat cells. However, the involvement of SIRT1 in the differentiation of human periodontal ligament cells into osteoblast‐like cells remains unclear. To identify the role of SIRT1 in human periodontal ligament cells, we measured SIRT1 mRNA and SIRT1 protein levels during the osteoblastic differentiation of human periodontal ligament cells. Additionally, we investigated the effects of overexpressing and underexpressing SIRT1 on the differentiation of human periodontal ligament cells, and the signaling mechanisms involved. Material and Methods: Expression of SIRT1 and osteoblastic differentiation markers was assessed by RT‐PCR, real‐time PCR, Alizarin red staining and western blotting. Results: Marked upregulation of SIRT1 mRNA and SIRT1 protein was observed in cells grown for 3 d in osteogenic induction medium (OM). Activation of SIRT1 using resveratrol and isonicotinamide stimulated osteoblastic differentiation in a dose‐dependent manner, as assessed by the expression of mRNAs encoding alkaline phosphatase, osteopontin, osteocalcin, osterix and Runx2, and induced calcium deposition. In contrast, inhibition of SIRT1 using sirtinol, nicotinamide and gene silencing by RNA interference suppressed mineralization and the expression of osteoblast marker mRNAs. Further mechanistic studies revealed that resveratrol treatment increased the phosphorylation of Akt, adenosine monophosphate kinase (AMPK), Smad 1/5/8 and c‐Jun N‐terminal kinase, but reduced OM‐induced activation of nuclear factor‐κB. Conversely, application of sirtinol suppressed the phosphorylation of Akt, AMPK, Smad 1/5/8, p38, ERK and c‐Jun N‐terminal kinase, and enhanced nuclear factor‐κB activity, in OM‐stimulated cells. Conclusion: These data suggest that SIRT1 is a potent regulator of differentiation of human periodontal ligament cells and may have clinical implications for periodontal bone regeneration.     

Ⅰ型骨质疏松症大鼠骨髓基质细胞体外培养及分化研究

目的　研究在构建的Ⅰ型骨质疏松症大鼠动物模型中,骨髓基质细胞( BMSCs)的生物学特性及其成骨和 成脂分化能力。方法　16只6月龄雌性SD大鼠随机分为实验组和对照组,实验组行双侧卵巢切除建立Ⅰ型骨质 疏松动物模型,对照组切除卵巢周围少量脂肪组织。术后3个月处死动物,非连续密度梯度离心分离骨质疏松大 鼠的BMSCs,传代后分别在成骨及成脂培养基中诱导培养14 d,观察细胞形态,通过组织特染对BMSCs的成骨、成脂 表型进行鉴定,计数阳性染色细胞百分比。结果　构建的Ⅰ型骨质疏松大鼠模型大鼠体重及整体股骨骨矿物质密 度(BMD)与对照组比较差异有显著性(P<0.01 );诱导培养后两组大鼠BMSCs碱性磷酸酶(ALP )、Von Kossa′s染色 和油红O染色实验阳性,且两组细胞阳性染色率无明显差别(P>0.05)。结论　本实验成功建立了大鼠骨质疏松 症模型,骨质疏松症大鼠BMSCs保持分化能力。     

Genome‐wide DNA‐methylation profiles in human bone marrow mesenchymal stem cells on titanium surfaces

The characteristics of titanium (Ti) have been shown to influence dental implant fixation. Treatment of surfaces using the sandblasted, large‐grit, acid‐etched (SLA) method is widely used to provide effective osseointegration. However, the DNA methylation‐associated mechanism by which SLA surface treatment affects osseointegration of human bone marrow mesenchymal stem cells (hBMSCs) remains elusive. Genome‐wide methylation profiling of hBMSCs on SLA‐treated and machined smooth Ti was performed using Illumina Infinium Methylation EPIC BeadChip at day 7 of osteogenic induction. In total, 2,846 CpG sites were differentially methylated in the SLA group compared with the machined group. Of these sites, 1,651 (covering 1,066 genes) were significantly hypermethylated and 1,195 (covering 775 genes) were significantly hypomethylated. Thirty significant enrichment pathways were observed, with Wnt signaling being the most significant. mRNA expression was identified by microarray and combined with DNA‐methylation profiles. Thirty‐seven genes displayed negative association between mRNA expression and DNA‐methylation level, with the osteogenesis‐related genes insulin‐like growth factor 2 (IGF2) and carboxypeptidase X, M14 Family Member 2 (CPXM2) showing significant up‐regulation and down‐regulation, respectively. In summary, our results demonstrate differences between SLA‐treated and machined surfaces in their effects on genome‐wide DNA methylation and enrichment of osteogenic pathways in hBMSCs. We provide novel insights into genes and pathways affected by SLA treatment in hBMSCs at the molecular level.