STRO-1 selected rat dental pulp stem cells transfected with adenoviral-mediated human bone morphogenetic protein 2 gene show enhanced odontogenic differentiation

Dental pulp stem cells harbor great potential for tissue-engineering purposes. However, previous studies have shown variable results, and some have reported only limited osteogenic and odontogenic potential.Because bone morphogenetic proteins (BMPs) are well-established agents to induce bone and dentin formation,in this study STRO-1-selected rat dental pulp-derived stem cells were transfected with the adenoviral mediated human BMP-2 gene. Subsequently, the cells were evaluated for their odontogenic differentiation ability in medium not containing dexamethasone or other stimuli. Cultures were investigated using light microscopy and scanning electron microscopy (SEM) and evaluated for cell proliferation, alkaline phosphatase(ALP) activity, and calcium content. Real-time polymerase chain reaction (PCR) was performed for gene expression of Alp, osteocalcin, collagen type I, bone sialoprotein, dentin sialophosphoprotein, and dentin matrix acidic phosphoprotein 1. Finally, an oligo-microarray was used to profile the expression of odontogenesis-related genes. Results of ALP activity, calcium content, and real-time PCR showed that only BMP2-transfected cells had the ability to differentiate into the odontoblast phenotype and to produce a calcified extracellular matrix. SEM and oligo-microarray confirmed these results. In contrast, the non-transfected cells represented a less differentiated cell phenotype. Based on our results, we concluded that the adenovirus can transfect STRO-1 selected cells with high efficacy. After BMP2 gene transfection, these cells had the ability to differentiate into odontoblast phenotype, even without the addition of odontogenic supplements to the medium.     

Differentiation ability of rat postnatal dental pulp cells in vitro

The current rapid progression in stem cell research has enhanced our knowledge of dental tissue regeneration. In this study, rat dental pulp cells were isolated and their differentiation ability was evaluated. First, dental pulp cells were obtained from maxillary incisors of male Wistar rats. Immunochemistry by stem cell marker STRO-1 proved the existence of stem cells or progenitors in the isolated cell population. The dissociated cells were then cultured both on smooth surfaces and on three-dimensional (3-D) scaffold materials in medium supplemented with beta-glycerophosphate, dexamethasone, and L-ascorbic acid. Cultures were analyzed by light and scanning electron microscopy and, on proliferation, alkaline phosphatase activity and calcium content were determined and the polymerase chain reaction was performed for dentin sialophosphoprotein, osteocalcin, and collagen type I. These cells showed the ability to differentiate into odontoblast-like cells and produced calcified nodules, which had components similar to dentin. In addition, we found that the "odontogenic" properties of the isolated cells were supported by three-dimensional calcium phosphate and titanium scaffolds equally well.     

Differential inducibility of human and porcine dental pulp-derived cells into odontoblasts

A robust method for generating odontoblasts from cultured dental pulp cells has not been established. In this study, efficient methods for deriving odontoblasts from cultured human and porcine dental pulp-derived cells were investigated with special attention to species differences. Cultured human cells showed relatively low alkaline phosphatase (ALP) activity in the presence of dexamethasone (Dex) and beta-glycerophosphate (beta-Gly). In contrast, the addition of 1,25-dihydroxyvitaminD(3) (VitD3) significantly increased the ALP activity. In porcine cells, beta-Gly alone or a combination of Dex and beta-Gly significantly increased ALP activity; however, addition of VitD3 reduced this activity. RT-PCR and Western blotting analysis revealed that the combination of three induction reagents on human cells significantly upregulates the expression of osteocalcin mRNA, and dentin sialoprotein. We propose that the combination of Dex, beta-Gly, and VitD3 is critical for differentiation of human dental pulp-derived cells into odontoblasts. In addition, the inducibility of dental pulp-derived cells presented remarkable species differences.     

Engineering Bone Formation from Human Dental Pulp- and Periodontal Ligament-Derived Cells

A robust method for inducing bone formation from cultured dental mesenchymal cells has not been established. In this study, a method for generating bone tissue in vivo from cultured human dental pulp- and periodontal ligament-derived cells (DPCs and PDLCs, respectively) was designed using exogenous bone morphogenetic protein 2 (BMP2). DPCs and PDLCs showed enhanced alkaline phosphatase (ALP) activity and calcified nodule formation in medium containing dexamethasone, β-glycerophosphate, and ascorbic acid (osteogenic medium). However, the addition of recombinant human bone morphogenetic protein 2 (rhBMP2) to osteogenic medium remarkably increased ALP activity and in vitro calcification above the increases observed with osteogenic medium alone. rhBMP2 also significantly upregulated the expression of osteocalcin, osteopontin, and dentin matrix protein 1 mRNA in both cell types cultured in osteogenic medium. Finally, we detected prominent bone-like tissue formation in vivo when cells had been exposed to rhBMP2 in osteogenic medium. In contrast, treatments with osteogenic medium or rhBMP2 alone could not induce abundant mineralized tissue formation. We propose here that treatment with rhBMP2 in osteogenic medium can make dental mesenchymal tissues a highly useful source of cells for bone tissue engineering. In addition, both DPCs and PDLCs showed similar and remarkable osteo-inducibility.     

Non-viral bone morphogenetic protein 2 transfection of rat dental pulp stem cells using calcium phosphate nanoparticles as carriers

Calcium phosphate nanoparticles have shown potential as non-viral vectors for gene delivery. The aim of this study was to induce bone morphogenetic protein (Bmp)2 transfection in rat dental pulp stem cells using calcium phosphate nanoparticles as a gene vector and then to evaluate the efficiency and bioactivity of the transfection. We also intended to investigate the behavior of transfected cells when seeded on 3-dimensional titanium fiber mesh scaffolds. Nanoparticles of calcium phosphate encapsulating plasmid deoxyribonucleic acid (DNA) (plasmid enhanced green fluorescent protein-BMP2) were prepared. Then, STRO-1-selected rat dental pulp stem cells were transfected using these nanoparticles. Transfection and bioactivity of the secreted BMP2 were examined. Thereafter, the transfected cells were cultured on a fibrous titanium mesh. The cultures were investigated using scanning electron microscipy and evaluated for cell proliferation, alkaline phosphatase activity and calcium content. Finally, real-time polymerase chain reaction was performed for odontogenesis-related gene expression. The results showed that the size of the DNA-loaded particles was approximately 100 nm in diameter. Nanoparticles could protect the DNA encapsulated inside from external DNase and release the loaded DNA in a low-acid environment (pH 3.0). In vitro, nanoparticle transfection was shown to be effective and to accelerate or promote the odontogenic differentiation of rat dental pulp stem cells when cultured in the 3-dimensional scaffolds. Based on our results, plasmid DNA-loaded calcium phosphate nanoparticles appear to be an effective non-viral vector for gene delivery and functioned well for odontogenic differentiation through Bmp2 transfection.     

改良酶消化法分离培养人乳牙牙髓干细胞

背景：乳牙牙髓干细胞具有极强的增殖活力,可以在短期内获得组织工程需要的细胞量。 目的：比较传统酶消化法和改良酶消化法获取人乳牙牙髓干细胞的成功率及生物学特性。 方法：取无龋滞留乳切牙12 颗,随机数字表法均分为两组,分别应用传统酶消化法和改良酶消化法分离获取乳牙牙髓细胞,在不同代次细胞中检测细胞扩增天数、收获量、生长曲线、倍增时间、克隆形成率、细胞表面特异标记物STRO-1、CD146、CD34 和CD45 的表达。细胞成骨、成脂诱导分化能力及通过检测碱性磷酸酶和牙本质涎蛋白表达水平,判定细胞牙向分化潜能。 结果与结论：两组细胞生长曲线,扩增天数、细胞收获量及细胞倍增时间相比,差异有显著性意义(P <0.05);牙向分化实验结果显示,改良酶消化法碱性磷酸酶和牙本质涎蛋白较传统酶消化法和对照组而言呈强阳性表达。然而,两组在克隆形成率、细胞表面特异标记物及多项诱导分化等方面差异无显著性意义(P > 0.05)。说明改良酶消化法与传统酶消法相比,可在较短时间内完成同源乳牙牙髓干细胞体外扩增培养,可为牙齿再生治疗提供高质量种子细胞,是乳牙牙髓干细胞体外培养的可靠方法。     

Differential Inducibility of Human and Porcine Dental Pulp-Derived Cells into Odontoblasts

A robust method for generating odontoblasts from cultured dental pulp cells has not been established. In this study, efficient methods for deriving odontoblasts from cultured human and porcine dental pulp-derived cells were investigated with special attention to species differences. Cultured human cells showed relatively low alkaline phosphatase (ALP) activity in the presence of dexamethasone (Dex) and β-glycerophosphate (β-Gly). In contrast, the addition of 1,25-dihydroxyvitaminD₃ (VitD3) significantly increased the ALP activity. In porcine cells, β-Gly alone or a combination of Dex and β-Gly significantly increased ALP activity; however, addition of VitD3 reduced this activity. RT-PCR and Western blotting analysis revealed that the combination of three induction reagents on human cells significantly upregulates the expression of osteocalcin mRNA, and dentin sialoprotein. We propose that the combination of Dex, β-Gly, and VitD3 is critical for differentiation of human dental pulp-derived cells into odontoblasts. In addition, the inducibility of dental pulp-derived cells presented remarkable species differences.     

Isolation and characterization of postnatal stem cells from human dental tissues

It was reported that postnatal stem cells are present in adult tissues such as bone marrow, liver, muscle, dental pulp, and periodontal ligament. We isolated postnatal stem cells from human dental tissues such as dental pulp (DPSC), periodontal ligament (PDLSC), periapical follicle (PAFSC), and the surrounding mandibular bone marrow (MBMSC) to ascertain their properties. Immunocytochemistry proved the existence of stem cells in these cell populations using STRO-1 as a stem cell marker. These cells also expressed the mesenchymal stem cell (MSC) markers CD29 and CD44. The isolated cells showed self-renewal capabilities and colony-forming efficiency. Almost all of the dental stem cells showed optimal growth when they were cultured in alpha modification of Eagle's medium (alpha-MEM) supplemented with 10% fetal calf serum (FCS) and 100 microM ascorbic acid. Only the PAFSC showed increased proliferation in 20% FCS and 50 microM ascorbic acid. All of the dental stem cells were capable of differentiating into adipocytes and mineral nodule forming cells. MBMSC, in particular, showed much better mineralization compared to the others. These results indicate that MSCs exist in various tissues of the teeth and can differentiate into osteoblasts, adipocytes, and other kinds of cells with varying efficiency.     

Differentiation of Human Dental Pulp Stem Cells into Dopaminergic Neuron-like Cells in Vitro

We investigated the potential of human dental pulp stem cells (hDPSCs) to differentiate into dopaminergic neurons in vitro as an autologous stem cell source for Parkinson’s disease treatment. The hDPSCs were expanded in knockout-embryonic stem cell (KO-ES) medium containing leukemia inhibitory factor (LIF) on gelatin-coated plates for 3–4 days. Then, the medium was replaced with KO-ES medium without LIF to allow the formation of the neurosphere for 4 days. The neurosphere was transferred into ITS medium, containing ITS (human insulin-transferrin-sodium) and fibronectin, to select for Nestin-positive cells for 6–8 days. The cells were then cultured in N-2 medium containing basic fibroblast growth factor (FGF), FGF-8b, sonic hedgehog-N, and ascorbic acid on poly-l-ornithine/fibronectin-coated plates to expand the Nestin-positive cells for up to 2 weeks. Finally, the cells were transferred into N-2/ascorbic acid medium to allow for their differentiation into dopaminergic neurons for 10–15 days. The differentiation stages were confirmed by morphological, immunocytochemical, flow cytometric, real-time PCR, and ELISA analyses. The expressions of mesenchymal stem cell markers were observed at the early stages. The expressions of early neuronal markers were maintained throughout the differentiation stages. The mature neural markers showed increased expression from stage 3 onwards. The percentage of cells positive for tyrosine hydroxylase was 14.49%, and the amount was 0.526 ± 0.033 ng/mL at the last stage. hDPSCs can differentiate into dopaminergic neural cells under experimental cell differentiation conditions, showing potential as an autologous cell source for the treatment of Parkinson’s disease.     

Characterization of dental pulp stem cells from impacted third molars cultured in low serum-containing medium

We isolated and expanded stem cells from dental pulp from extracted third molars using an innovative culture method consisting of low serum-containing medium supplemented with epidermal growth factor and platelet-derived growth factor BB. We evaluated the differentiation potential of these cells when they were growing either adherently or as micromass/spheroid cultures in various media. Undifferentiated and differentiated cells were analyzed by flow cytometry, immunocytochemistry and immunoblotting. The flow cytometry results showed that the dental pulp stem cells (DPSCs) were positive for mesenchymal stromal cell markers, but negative for hematopoietic markers. Immunocytochemical and/or immunoblotting analyses revealed the expression of numerous stem cell markers, including nanog, Sox2, nestin, Musashi-1 and nucleostemin, whereas they were negative for markers associated with differentiated neural, vascular and hepatic cells. Surprisingly, the cells were only slightly positive for α-smooth muscle actin, and a heterogeneous expression of CD146 was observed. When cultured in osteogenic media, they expressed osteonectin, osteopontin and procollagen I, and in micromass cultures, they produced collagen I. DPSCs cultured in TGF-β1/3-supplemented media produced extracellular matrix typical of cartilaginous tissue. The addition of vascular endothelial growth factor to serum-free media resulted in the expression of endothelial markers. Interestingly, when cultured in neurogenic media, DPSCs exhibited de novo or upregulated markers of undifferentiated and differentiated neural cells. Collectively, our data show that DPSCs are self-renewing and able to express markers of bone, cartilage, vascular and neural tissues, suggesting their multipotential capacity. Their easy accessibility makes these cells a suitable source of somatic stem cells for tissue engineering.     

Ultrastructural and immunocytochemical analysis of multilineage differentiated human dental pulp- and umbilical cord-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are one of the most promising stem cell types due to their availability and relatively simple requirements for in vitro expansion and genetic manipulation. Besides the well-characterized MSCs derived from bone marrow, there is growing evidence suggesting that dental pulp and the umbilical cord matrix both contain a substantial amount of cells having properties similar to those of MSCs. In order to assess the potential of dental pulp-derived MSCs (DPSC) and umbilical cord-derived MSCs (UCSC) in future clinical applications, it is essential to gain more insight into their differentiation capacity and to evaluate the tissues formed by these cells. In the present study, the morphological and ultrastructural characteristics of DPSC and UCSC induced towards osteogenic, adipogenic, and chondrogenic lineages were investigated. Cultured DPSC and UCSC showed a similar expression pattern of antigens characteristic of MSCs including CD105, CD29, CD44, CD146, and STRO-1. Under appropriate culture conditions, both DPSC and UCSC showed chondrogenic and osteogenic potential. Adipogenesis could be only partially induced in DPSC resulting in the de novo expression of fatty acid binding protein (FABP), whereas UCSC expressed FABP combined with a very high accumulation of lipid droplets in the cytoplasm. Our results demonstrate, at the biochemical and ultrastructural level, that DPSC display at least bilineage potential, whereas UCSC, which are developmentally more primitive cells, show trilineage potential. We emphasize that transmission electron microscopical analysis is useful to elucidate detailed structural information and provides indisputable evidence of differentiation. These findings highlight their potential therapeutic value for cell-based tissue engineering.     

地塞米松诱导牙周膜干细胞的定向成骨分化及凋亡

背景：牙周膜干细胞是一类起源于牙组织的成体干细胞,具有良好的成骨分化能力,有望在骨组织工程中得到应用。 目的：观察成骨诱导液对牙周膜干细胞成骨分化能力及细胞早期凋亡的影响。 方法：从原代牙周膜组织中分离得到牙周膜干细胞,以1×10⁴/cm²浓度铺板后开始诱导。利用1,10,100 nmol/L地塞米松、β-磷酸甘油钠、维生素C为成骨诱导剂,以碱性磷酸酶活性检测、茜素红矿化结节染色、荧光定量PCR等方法对细胞成骨情况进行鉴定,采用AnnexinV/PI双染法检测细胞凋亡情况。 结果与结论：地塞米松可有效诱导牙周膜干细胞成骨分化,可显著提高碱性磷酸酶活性,促进茜素红矿化结节形成,提高成骨相关基因骨粘连蛋白及Ⅰ型胶原表达。根据碱性磷酸酶活性和矿化结节实验结果,地塞米松的成骨诱导具有浓度梯度效应,其中100 nmol/L 地塞米松具有最佳成骨诱导能力。细胞凋亡结果提示,地塞米松诱导的成骨分化具有一定促凋亡作用,可诱导牙周膜细胞的早期凋亡。     

Human dental pulp cell culture and cell transplantation with an alginate scaffold

Many studies on tissue stem cells have been conducted in the field of regenerative medicine, and some studies have indicated that cultured dental pulp mesenchymal cells secrete dentin matrix. In the present study we used alginate as a scaffold to transplant subcultured human dental pulp cells subcutaneously into the backs of nude mice. We found that when beta-glycerophosphate was added to the culture medium, dentin sialophosphoprotein mRNA coding dentin sialoprotein (DSP) was expressed. An increase in alkaline phosphatase, which is an early marker for odontoblast differentiation, was also demonstrated. At 6 weeks after implantation the subcutaneous formation of radio-opaque calcified bodies was observed in situ. Immunohistochemical and fine structure studies identified expression of type I collagen, type III collagen, and DSP in the mineralizing transplants. Isolated odontoblast-like cells initiated dentin-like hard tissue formation and scattered autolyzing apoptotic cells were also observed in the transplants. The study showed that subcultured dental pulp cells actively differentiate into odontoblast-like cells and induce calcification in an alginate scaffold.     

Chondrocytic differentiation of human adipose-derived adult stem cells in elastin-like polypeptide

Human adipose derived adult stem (hADAS) cells have the ability to differentiate into a chondrogenic phenotype in three-dimensional culture and media containing dexamethasone and TGF-beta. The current study examined the potential of a genetically engineered elastin-like polypeptide (ELP) to promote the chondrocytic differentiation of hADAS cells without exogenous chondrogenic supplements. hADAS cells were cultured in ELP hydrogels in either chondrogenic or standard medium at 5% O2 for up to 2 weeks. By day 14, constructs cultured in either medium exhibited significant increases in sulfated glycosaminoglycan (up to 100%) and collagen contents (up to 420%). Immunolabeling confirmed that the matrix formed consisted mainly of type II and not type I collagen. The composition of the constructs cultured in either medium did not differ significantly. To assess the effect of oxygen tension on the differentiation of the above constructs, samples were cultured in standard medium at either 5% or 20% O2 for 7 days and their gene expression profile was evaluated using real time RT-PCR. In both cases, the hADAS-ELP constructs upregulated SOX9 and type II collagen gene expression, while type I collagen was downregulated. However, constructs cultured in 20% O2 highly upregulated type X collagen, which was not detected in the 5% O2 cultures. The study suggests that ELP can promote chondrogenesis for hADAS cells in the absence of exogenous TGF-beta1 and dexamethasone, especially under low oxygen tension conditions.     

Hard tissue formation in a porous HA/TCP ceramic scaffold loaded with stromal cells derived from dental pulp and bone marrow

The aim of this study was to compare the ability of hard tissue regeneration of four types of stem cells or precursors under both in vitro and in vivo situations. Primary cultures of rat bone marrow, rat dental pulp, human bone marrow, and human dental pulp cells were seeded onto a porous ceramic scaffold material, and then either cultured in an osteogenic medium or subcutaneously implanted into nude mice. For cell culture, samples were collected at weeks 0, 1, 3, and 5. Results were analyzed by measuring cell proliferation rate and alkaline phosphatase activity, scanning electron microscopy, and real-time PCR. Samples from the implantation study were retrieved after 5 and 10 weeks and evaluated by histology and real-time PCR. The results indicated that in vitro abundant cell growth and mineralization of extracellular matrix was observed for all types of cells. However, in vivo matured bone formation was found only in the samples seeded with rat bone marrow stromal cells. Real-time PCR suggested that the expression of Runx2 and the expression osteocalcin were important for the differentiation of bone marrow stromal cells, while dentin sialophosphoprotein contributed to the odontogenic differentiation. In conclusion, the limited hard tissue regeneration ability of dental pulp stromal cells questions their practical application for complete tooth regeneration. Repeated cell passaging may explain the reduction of the osteogenic ability of both bone- and dentinal-derived stem cells. Therefore, it is essential to develop new cell culture methods to harvest the desired cell numbers while not obliterating the osteogenic potential.     

兔骨髓间充质干细胞分化成骨及VEGF表达

目的　研究兔骨髓间充质干细胞 (MSC)诱导培养分化为成骨细胞的功能表面及血管内皮生长因子 (VEGF)的表达。方法　分离、培养新生兔骨髓间充质干细胞 ,体外扩增 ,用含地塞米松、β 甘油磷酸钠和维生素C的条件培养液诱导MSC向成骨细胞分化 ,观察诱导细胞碱性磷酸酶染色、钙化结节形成以及VEGF的表达。结果　MSC增殖能力活跃 ,成骨诱导后 ,细胞碱性磷酸酶呈强阳性染色 ,形成矿化结节 ,且VEGF表达增强。结论　兔MSC可迅速扩增 ,经诱导分化成骨后VEGF表达增强 ,是研究骨组织工程的理想种子细胞     

维甲酸诱导小型猪牙周膜干细胞的体外成骨

背景：近期研究发现维甲酸对胚胎干细胞及多种成体干细胞具有成骨方向诱导的作用。 目的：观察维甲酸对小型猪牙周膜干细胞体外成骨作用的影响。 方法：采用组织块法获得小型猪牙周膜细胞,有限稀释法纯化小型猪牙周膜干细胞,免疫荧光法检测STRO-1、免疫细胞化学法检测波形蛋白、角蛋白鉴定小型猪牙周膜干细胞。CCK8法测定小型猪牙周膜干细胞增殖曲线,检测小型猪PDLSC克隆形成率。使用维甲酸对第3代小型猪牙周膜干细胞进行成骨诱导,茜素红染色检测矿化结节,免疫细胞化学方法检测成骨相关基因骨桥蛋白、骨钙素、Ⅰ型胶原、Ⅲ型胶原的表达。 结果与结论：有限稀释法分离纯化小型猪牙周膜干细胞STRO-1,波形蛋白阳性表达,角蛋白阴性表达,克隆形成率为2.8%,维甲酸诱导14 d后,碱性磷酸酶染色阳性,诱导21 d后茜素红染色阳性,免疫细胞化学法检测骨桥蛋白、骨钙素、Ⅰ型胶原阳性表达,Ⅲ型胶原阴性表达。结果表明小型猪牙周膜干细胞能够被维甲酸诱导向成骨样细胞分化。     

Student Award for Outstanding Research Winner in the Ph.D. Category for the 9th World Biomaterials Congress, Chengdu, China, June 1-5, 2012: The interplay of bone-like extracellular matrix and TNF-α signaling on in vitro osteogenic differentiation of mesenchymal stem cells

As an initial step in the development of a bone tissue engineering strategy to rationally control inflammation, we investigated the interplay of bone-like extracellular matrix (ECM) and varying doses of the inflammatory cytokine tumor necrosis factor alpha (TNF-α) on osteogenically differentiating mesenchymal stem cells (MSCs) cultured in vitro on 3D poly(ε-caprolactone) (PCL) microfiber scaffolds containing pregenerated bone-like ECM. To generate the ECM, PCL scaffolds were seeded with MSCs and cultured in medium containing the typically required osteogenic supplement dexamethasone. However, since dexamethasone antagonizes TNF-α, the interplay of ECM and TNF-α was investigated by culturing na?ve MSCs on the decellularized scaffolds in the absence of dexamethasone. MSCs cultured on ECM-coated scaffolds continued to deposit mineralized matrix, a late stage marker of osteogenic differentiation. Mineralized matrix deposition was not adversely affected by exposure to TNF-α for 4-8 days, but was significantly reduced after continuous exposure to TNF-α over 16 days, which simulates the in vivo response, where brief TNF-α signaling stimulates bone regeneration, while prolonged exposure has damaging effects. This underscores the exciting potential of PCL/ECM constructs as a more clinically realistic in vitro culture model to facilitate the design of new bone tissue engineering strategies that rationally control inflammation to promote regeneration.