Dentin matrix proteins (DMPs) enhance differentiation of BMMSCs via ERK and P38 MAPK pathways

LPS-induced inflammation potentiates dental pulp stem cell odontogenic differentiation through C5aR and p38

AIM

Inflammation is a complex host response to harmful infection or injury, and it seems to play a crucial role in tissue regeneration both positively and negatively. We have previously demonstrated that the activation of the complement C5a pathway affects dentin-pulp regeneration. However, limited information is available to understand the role of the complement C5a system related to inflammation-mediated dentinogenesis. The aim of this study was to determine the role of complement C5a receptor (C5aR) in regulating lipopolysaccharide (LPS)-induced odontogenic differentiation of dental pulp stem cells (DPSCs).

MATERIAL AND METHODS

Human DPSCs were subjected to LPS-stimulated odontogenic differentiation in dentinogenic media treated with the C5aR agonist and antagonist. A putative downstream pathway of the C5aR was examined using a p38 mitogen-activated protein kinase (p38) inhibitor (SB203580).

RESULTS

Our data demonstrated that inflammation induced by the LPS treatment potentiated DPSC odontogenic differentiation and that this is C5aR dependent. C5aR signaling controlled the LPS-stimulated dentinogenesis by regulating the expression of odontogenic lineage markers like dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP-1). Moreover, the LPS treatment increased the total p38, and the active form of p38 expression, and treatment with SB203580 abolished the LPS-induced DSPP and DMP-1 increase.

CONCLUSIONS

These data suggest a significant role of C5aR and its putative downstream molecule p38 in the LPS-induced odontogenic DPSCs differentiation. This study highlights the regulatory pathway of complement C5aR/p38 and a possible therapeutic approach for improving the efficiency of dentin regeneration during inflammation.

Micropatterning biomineralization with immobilized mother of pearl proteins

In response to the drawbacks of autograft donor-site morbidity and bone morphogenetic protein type 2 (BMP2) carcinogenesis and ectopic bone formation, there has been an increased research focus towards developing alternatives capable of achieving spatial control over bone formation. Here we show for the first time both osteogenic differentiation and mineralization (from solution or mediated by cells) occurring within predetermined microscopic patterns. Our results revealed that both PEGylated BMP2 and nacre proteins induced stem cell osteodifferentiation in microscopic patterns when these proteins were covalently bonded in patterns onto polyethylene glycol diacrylate (PEGDA) hydrogel substrates; however, only nacre proteins induced mineralization localized to the micropatterns. These findings have broad implications on the design and development of orthopedic biomaterials and drug delivery.

Dentin-Derived Inorganic Minerals Promote the Osteogenesis of Bone Marrow-Derived Mesenchymal Stem Cells: Potential Applications for Bone Regeneration

Background

Oral and maxillofacial bone loss is highly prevalent among populations, and nowadays, increased attention has been focused on dentin derivatives serving as desirable graft materials for bone regeneration. In this study, dentin-derived inorganic mineral (DIM) was fabricated with a high-temperature calcination technique and the effects of DIM on the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMMSCs) and the bone formation were elucidated.

Methods

The effects of DIM on BMMSC proliferation and apoptosis capacity were evaluated by CCK-8, flow cytometry, and EdU assays. Alkaline phosphatase (ALP) activity detection, ALP staining, alizarin red staining, and osteogenic marker expression analysis were performed to investigate the influence of DIM on the osteogenic differentiation of BMMSCs, as well as the relevant signal mechanisms. The model of critical-sized defects in the calvarium of rats was constructed for exploring the in vivo efficiency of DIM on bone regeneration.

Results

Cell viability assays indicated that DIM had no cytotoxicity. BMMSCs cultured with DIM presented a higher level of osteogenic differentiation ability than those in the control group. The activation in ERK and p38 signals was detected in DIM-treated BMMSCs, and both pathways and osteogenic process were suppressed while using ERK inhibitor U0126 and p38 inhibitor SB203580, respectively. Furthermore, the animal experiments revealed that DIM could dramatically enhance new bone formation compared to the control group.

Conclusion

DIM could promote BMMSC osteogenic differentiation via triggering the ERK and p38 MAPK signaling pathways and might be a novel predictable material for facilitating bone formation.

Magnesium-enriched microenvironment promotes odontogenic differentiation in human dental pulp stem cells by activating ERK/BMP2/Smads signaling

Background

Magnesium (Mg²⁺)-enriched microenvironment promotes odontogenic differentiation in human dental pulp stem cells (DPSCs), but the regulatory mechanisms remain undefined. The aim of this work was to assess magnesium’s function in the above process and to explore the associated signaling pathway.

Methods

DPSCs underwent culture in odontogenic medium with the addition of 0, 1, 5, or 10 mM MgCl₂. Intracellular Mg²⁺ levels in DPSCs were evaluated flow cytometrically using Mag-Fluo-4-AM. Mg²⁺-entry was inhibited by TRPM7 inhibitor 2-aminoethoxydiphenyl borate (2-APB). RNA-Sequencing was carried out for assessing transcriptome alterations in DPSCs during odontogenic differentiation associated with high extracellular Mg²⁺. KEGG pathway analysis was performed to determine pathways related to the retrieved differentially expressed genes (DEGs). Immunoblot was performed for assessing magnesium’s role and exploring ERK/BMP2/Smads signaling.

Results

Mg²⁺-enriched microenvironment promoted odontogenic differentiation in DPSCs via intracellular Mg²⁺ increase. Consistently, the positive effect of high extracellular Mg²⁺ on odontogenic differentiation in DPSCs was blocked by 2-APB, which reduced Mg²⁺ entry. RNA-sequencing identified 734 DEGs related to odontogenic differentiation in DPSCs in the presence of high extracellular Mg²⁺. These DEGs participated in many cascades such as MAPK and TGF-β pathways. Consistently, ERK and BMP2/Smads pathways were activated in DPSCs treated with high extracellular Mg²⁺. In agreement, ERK signaling inhibition by U0126 blunted the effect of high extracellular Mg²⁺ on mineralization and odontogenic differentiation in DPSCs. Interestingly, BMP2, BMPR1, and phosphorylated Smad1/5/9 were significantly decreased by U0126, indicating that BMP2/Smads acted as downstream of ERK.

Conclusions

Mg²⁺-enriched microenvironment promotes odontogenic differentiation in DPSCs by activating ERK/BMP2/Smads signaling via intracellular Mg²⁺ increase. This study revealed that Mg²⁺-enriched microenvironment could be used as a new strategy for dental pulp regeneration.

Protein S100-A7 Derived from Digested Dentin Is a Critical Molecule for Dentin Pulp Regeneration

Dentin consists of inorganic hard tissue and organic dentin matrix components (DMCs). Various kinds of bioactive molecules are included in DMCs and some of them can be released after digestion by endogenous matrix metalloproteinases (MMPs) in the caries region. Digested DMCs induced by MMP20 have been reported to promote pulpal wound healing processes, but the released critical molecules responsible for this phenomenon are unclear. Here, we identified protein S100-A7 as a critical molecule for pulpal healing in digested DMCs by comprehensive proteomic approaches and following pulp capping experiments in rat molars. In addition, immunohistochemical results indicated the specific distribution of S100-A7 and receptor for advanced glycation end-products (RAGE) as receptor for S100-A7 in the early stage of the pulpal healing process, and following accumulation of CD146-positive stem cells in wounded pulp. Our findings indicate that protein S100-A7 released from dentin by MMP20 might play a key role in dentin pulp regeneration.

Long noncoding RNA TUG1 inhibits osteogenesis of bone marrow mesenchymal stem cells via Smad5 after irradiation

Irradiation can greatly inhibit osteogenesis of bone marrow mesenchymal stem cells (BM-MSCs). However, the mechanism remains unclear.

Methods: We analyzed the expression profile of long noncoding RNAs (lncRNAs) in BM-MSCs using microarray data. LncRNA TUG1 (Taurine Upregulated Gene 1) was selected and tested in radiated BM-MSCs and non-radiated BM-MSCs. Functional analyses (in vitro) were performed to confirm the role of TUG1 in the osteogenic inhibition induced by irradiation. A RIP (RNA immunoprecipitation) assay was performed to detect the interaction of TUG1 and Smad5. Smad5 and the phosphorylated Smad5 (p-Smad5) were tested by western blot. The nuclear translocation of p-Smad5 were tested by immunofluorescence analysis. Furthermore, a series of Smad5 deletions was constructed to identify the TUG1 binding site of Smad5.

Results: We found that numerous lncRNAs, including TUG1, exhibit significant expression differences after irradiation. After irradiation TUG1 was significantly increased in BM-MSCs and inhibited osteogenesis. Furthermore, TUG1 directly bound to Smad5, an osteogenic enhancer. Although the phosphorylation level of Smad5 was increased following irradiation, osteogenesis of BM-MSCs was decreased. Mechanistically, TUG1 interacting with the 50-90 aa region of Smad5 and blocks the nuclear translocation of p-Smad5, abolishing osteogenic signalling after irradiation.

Conclusion: These results indicate that TUG1 is a negative regulator of Smad5 signalling and suppresses osteogenesis of BM-MSCs after irradiation.

LncRNA H19 promotes the committed differentiation of stem cells from apical papilla via miR-141/SPAG9 pathway

Long noncoding RNAs (lncRNAs) exert significant roles at transcriptional and post-transcriptional levels. Stem cells from apical papilla (SCAPs) differentiate into dentin/bone-like tissues under certain conditions. So far, whether lncRNA-H19 can affect the proliferative behaviors and osteo/odontogenesis of SCAPs, as well as its specific mechanism remain to be elucidated. Here, SCAPs were isolated and transfected with the lentiviruses or packaging vectors. Our results showed that lncRNA-H19 had no significant effect on the proliferative behaviors of SCAPs, as presented by CCK-8 assay, EdU assay and flow cytometry (FCM). Furthermore, alkaline phosphatase (ALP) activity, alizarin red staining, Western blot assay (WB), quantitative real-time polymerase chain reaction (qRT-PCR) and in vivo bone formation assay were conducted to verify the biological influences of H19 on SCAPs. Overexpression of H19 led to the enhanced osteo/odontogenesis of SCAPs, whereas knockdown of H19 inhibited these effects. Mechanistically, H19 competitively bound to miR-141 and prevented SPAG9 from miRNA-mediated degradation, thus significantly elevating phosphorylated levels of p38 and JNK and facilitating the committed differentiation of SCAPs. Taken together, the osteo/odontogenesis of SCAPs was upregulated by overexpression of H19 via miR-141/SPAG9 pathway.

MagT1 regulated the odontogenic differentiation of BMMSCs induced byTGC-CM via ERK signaling pathway

Background

Bone marrow mesenchymal stem cells (BMMSCs) are suitable cell sources for dental pulp regeneration, but the mechanism of BMMSCs differentiation into odontogenic lineage remains unknown. The aim of the present study was to reveal the role of magnesium transporter protein 1 (MagT1) and MAPK pathways in the odontogenic differentiation of BMMSCs.

Methods

The RNA sequencing (RNA-seq) was performed to explore the altered transcriptome of BMMSCs undergoing odontogenic differentiation induced by tooth germ cell-condition medium (TGC-CM). Pathway analysis was conducted to explore enriched pathways of the differential expression signature. Automated western blot, real-time PCR, shRNA lentivirus, and flow cytometry were used to detect the function of MagTl and MAPK pathway in odontogenic differentiation of BMMSCs.

Results

RNA-seq identified 622 differentially expressed genes associated with odontogenic differentiation of BMMSCs induced by TGC-CM, some of which were responsible for MAPK pathway. Consistently, we verified that TGC-CM induced odontogenic differentiation of BMMSCs through activating ERK/MAPK pathway, and the inactivation of ERK/MAPK pathway inhibited the odontogenic differentiation induced by TGC-CM. We also found MagT1 protein was significantly increased during odontogenic differentiation of BMMSCs induced by TGC-CMM, in accordance, MagT1 knockdown significantly decreased the extent of mineralized nodules and the protein levels of alkaline phosphatase (ALP), dentin matrix protein 1 (DMP-1), and dentin sialophosphoprotein (DSP). Flow cytometry showed that intracellular Mg²⁺ was significantly reduced in MagT1-knockdown BMMSCs, indicating the suppression of MagT1 inhibited odontogenic differentiation of BMMSCs by decreasing intracellular Mg²⁺. Finally, we performed RNA-seq to explore the altered transcriptome of MagT1-knockdown BMMSCs undergoing odontogenic differentiation and identified 281 differentially expressed genes, some of which were involved in MAPK pathway. Consistently, automated western blot analysis found the ERK/MAPK pathway was inhibited in MagT1-knockdown BMMSCs during odontogenic differentiation, indicating that suppression of MagT1 inhibited odontogenic differentiation of BMMSCs via ERK/MAPK pathway.

Conclusions

This study identified the significant alteration of transcriptome in BMMSCs undergoing odontogenic differentiation induced by TGC-CM. We clarified the pivotal role of MagT1 and ERK/MAPK pathway in odontogenic differentiation of BMMSCs, and suppression of MagT1 inhibited the odontogenic differentiation of BMMSCs by decreasing the intracellular Mg²⁺ and inactivating ERK/MAPK pathway.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1148-6) contains supplementary material, which is available to authorized users.

Spatiotemporal Control Strategies for Bone Formation through Tissue Engineering and Regenerative Medicine Approaches

Global increases in life expectancy drive increasing demands for bone regeneration. The gold standard for surgical bone repair is autografting, which enjoys excellent clinical outcomes; however, it possesses significant drawbacks including donor site morbidity and limited availability. Although collagen sponges delivered with bone morphogenetic protein, type 2 (BMP2) are a common alternative or supplement, they do not efficiently retain BMP2, necessitating extremely high doses to elicit bone formation. Hence, reports of BMP2 complications are rising, including cancer promotion and ectopic bone formation, the latter inducing complications such as breathing difficulties and neurologic impairments. Thus, efforts to exert spatial control over bone formation are increasing. Several tissue engineering approaches have demonstrated the potential for targeted and controlled bone formation. These approaches include biomaterial scaffolds derived from synthetic sources, e.g., calcium phosphates or polymers; natural sources, e.g., bone or seashell; and immobilized biofactors, e.g., BMP2. Although BMP2 is the only protein clinically approved for use in a surgical device, there are several proteins, small molecules, and growth factors that show promise in tissue engineering applications. This review profiles the tissue engineering advances in achieving control over the location and onset of bone formation (spatiotemporal control) toward avoiding the complications associated with BMP2.

Effect of Dentin Matrix Components on the Mineralization of Human Mesenchymal Stromal Cells

IMPACT STATEMENT

This research has been conducted with the aim to contribute to the development of treatment modalities for the reconstruction of lost/damaged mineralized tissues. Currently, determining the most appropriate stromal cell population and signaling cues stands at the core of developing effective treatments. We provide new insights into the effect of innate inductive cues found in human dentin matrix components, on the osteogenic differentiation of various human stromal cell types. The effects of dentin extracellular matrix components on umbilical cord mesenchymal stromal cells have not been investigated before. The findings of this study could underpin translational research based on the development of techniques for mineralized tissue engineering and will be of great interest for the readership of Tissue Engineering Part A.

The role of Rho-GEF Trio in regulating tooth root development through the p38 MAPK pathway

Trio, the Rho guanine nucleotide exchange factor (Rho-GEF), plays diverse roles in cell migration, cell axon guidance and cytoskeleton reorganization. Conserved during evolution, Trio encodes two guanine nucleotide exchange factor domains (GEFs) and activates small GTPases. The Rho-family small GTPases RhoA and Rac1, which are target molecules of Trio, have been described to engage in craniofacial development and tooth formation. However, the exact role of Trio in tooth development remains elusive. In this study, we generated Wnt1-cre;Trio^fl/fl mice to address the potential function of Trio in tooth development. Wnt1-cre;Trio^fl/fl mice showed short root deformity as well as decreased expression of odontogenic makers such as RUNX2, OSX, OCN, and OPN. In vitro, Trio was silenced in human stem cells of dental papilla (SCAPs). Compared with the control group, the proliferation and migration ability in the experimental group was disrupted. After knocking down Trio in SCAPs, the cells showed phenotypes of poor odontogenic differentiation and weak mineralized nodules. To study the underlying mechanism, we investigated the p38 MAPK pathway and found that loss of Trio blocked the cascade transduction of p38 MAPK signaling. In conclusion, we identified Trio as a novel coordinator in regulating root development and clarified its relevant molecular events.

Elucidation on Predominant Pathways Involved in the Differentiation and Mineralization of Odontoblast-Like Cells by Selective Blockade of Mitogen-Activated Protein Kinases

Aim

To analyze the effect of three mitogen-activated protein kinase (MAPK) inhibitors, namely, SB202190 (p38 inhibitor), SP600125 (JNK inhibitor), and PD98059 (ERK inhibitor) in Dex-stimulated MDPC-23 cell differentiation and mineralization.

Methods

Experiment was divided into five groups, control (cells without Dex and inhibitors treatment), Dex (cells with Dex treatment but without inhibitors), Dex + SB202190, Dex + SP600125, and Dex + PD98059. Cell differentiation was assessed by alkaline phosphatase (ALP) activity assay and real time RT-PCR. Cell mineralization was investigated by alizarin red staining.

Results

Exposure to SB202190 (20 μM) significantly decreased the mineral deposition in Dex-treated cells as demonstrated by alizarin red staining. Treatment of SP600125 (20 μM) attenuated the mineralization as well, albeit at a lower degree as compared to SB202190 (20 μM). Similarly, SB202190 (20 μM) completely abrogated the ALP activity stimulated by Dex at six days in culture, while no changes were observed with regard to ALP activity in SP600125 (20 μM) and PD98059 (20 μM) treated cells. The upregulation of bone sialoprotein (BSP), ALP, and osteopontin (OPN) in Dex challenged cells was completely inhibited by SB202190.

Conclusion

Blockade of p38-MAPK signaling pathway resulted in significant inhibition of ALP activity, mineralization, and downregulation of osteogenic markers. The data implicated that p38 signaling pathway plays a critical role in the regulation of MDPC-23 cells differentiation and mineralization.

Different methods of dentin processing for application in bone tissue engineering: A systematic review

Dentin has become an interesting potential biomaterial for tissue engineering of oral hard tissues. It can be used as a scaffold or as a source of growth factors in bone tissue engineering. Different forms of dentin have been studied for their potential use as bone substitutes. Here, we systematically review different methods of dentin preparation and the efficacy of processed dentin in bone tissue engineering. An electronic search was carried out in PubMed and Scopus databases for articles published from 2000 to 2016. Studies on dentin preparation for application in bone tissue engineering were selected. The initial search yielded a total of 1045 articles, of which 37 were finally selected. Review of studies showed that demineralization was the most commonly used dentin preparation process for use in tissue engineering. Dentin extract, dentin particles (tooth ash), freeze-dried dentin, and denatured dentin are others method of dentin preparation. Based on our literature review, we can conclude that preparation procedure and the size and shape of dentin particles play an important role in its osteoinductive and osteoconductive properties. Standardization of these methods is important to draw a conclusion in this regard. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2616-2627, 2016.

Regulation of the osteogenic and adipogenic differentiation of bone marrow-derived stromal cells by extracellular uridine triphosphate: The role of P2Y2 receptor and ERK1/2 signaling

An imbalance in the osteogenesis and adipogenesis of bone marrow-derived stromal cells (BMSCs) is a crucial pathological factor in the development of osteoporosis. Growing evidence suggests that extracellular nucleotide signaling involving the P2 receptors plays a significant role in bone metabolism. The aim of the present study was to investigate the effects of uridine triphosphate (UTP) on the osteogenic and adipogenic differentiation of BMSCs, and to elucidate the underlying mechanisms. The differentiation of the BMSCs was determined by measuring the mRNA and protein expression levels of osteogenic- and adipogenic-related markers, alkaline phosphatase (ALP) staining, alizarin red staining and Oil Red O staining. The effects of UTP on BMSC differentiation were assayed using selective P2Y receptor antagonists, small interfering RNA (siRNA) and an intracellular signaling inhibitor. The incubation of the BMSCs with UTP resulted in a dose-dependent decrease in osteogenesis and an increase in adipogenesis, without affecting cell proliferation. Significantly, siRNA targeting the P2Y2 receptor prevented the effects of UTP, whereas the P2Y6 receptor antagonist (MRS2578) and siRNA targeting the P2Y4 receptor had little effect. The activation of P2Y receptors by UTP transduced to the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. This transduction was prevented by the mitogen-activated protein kinase inhibitor (U0126) and siRNA targeting the P2Y2 receptor. U0126 prevented the effects of UTP on osteogenic- and adipogenic-related gene expression after 24 h of culture, as opposed to 3 to 7 days of culture. Thus, our data suggest that UTP suppresses the osteogenic and enhances the adipogenic differentiation of BMSCs by activating the P2Y2 receptor. The ERK1/2 signaling pathway mediates the early stages of this process.

Role of P2 × 7 receptor in the differentiation of bone marrow stromal cells into osteoblasts and adipocytes

Imbalance in osteogenesis and adipogenesis of bone marrow stromal cells is a crucial pathological process of osteoporosis. P2 × 7-deficient mice were previously shown to exhibit an osteopenic phenotype and abnormal fat distribution, leading us to hypothesize that P2 × 7R activation was involved in the differentiation of BMSCs. Consequently, we investigated the effect of P2 × 7R activation on osteogenic and adipogenic differentiation of BMSCs in vitro, and established an ovariectomized (OVX) osteoporosis model to test P2 × 7R activation on adipocytes formation, trabecular and cortical bone parameters in vivo. Our results showed that activation of P2 × 7R by BzATP resulted in increase in the gene expression of osteoblastic markers, the activity of alkaline phosphatase and bone mineralization, and decrease in the gene expression of adipogenic markers and the number of adipocytes generated by BMSCs. MicroCT analysis showed that BzATP treatment ameliorated the micro-architecture of trabecular bones in OVX mice, while cortical bone parameters were unaffected. H&E staining analysis showed that was increase in the volume of trabecular bone and number of trabecular bone, and decrease in bone marrow adipocytes in BzATP-treated OVX mice compared with OVX mice. Also, activation of P2 × 7R transduced to ERK1/2 and JNK signaling pathways. This transduction was prevented by BBG, U0126, and SP600125. U0126 and SP600125 prevented BzATP-induced up-regulation of osteogenic-related genes expression and down-regulation of adipogenic-related genes expression. These data suggest that BzATP activates the differentiation of BMSCs into osteoblasts but not adipocytes by stimulating ERK1/2 and JNK signaling pathways in a P2 × 7R-dependent way.

Activation of ERK pathway is required for 15-HETE-induced angiogenesis in human umbilical vascular endothelial cells

Angiogenesis plays a critical role in the progression of cardiovascular disease, retinal ischemia, or tumorigenesis. The imbalance of endothelial cell proliferation and apoptosis disturbs the establishment of the vasculogenesis, which is affected by several arachidonic acid metabolites. 15-Hydroxyeicosatetraenoic acid (15-HETE) is one of the metabolites. However, the underlying mechanisms of angiogenesis induced by 15-HETE in human umbilical vascular endothelial cells (HUVECs) are still poorly understood. Since extracellular signal-regulated kinase (ERK) is a critical regulator of cell proliferation, there may be a crosstalk between 15-HETE-regulating angiogenic process and ERK-proliferative effect in HUVECs. To test this hypothesis, we study the effect of 15-HETE on cell proliferation, angiogenesis, and apoptosis using cell viability measurement, cell cycle analysis, western blot, scratch-wound, tube formation assay, and nuclear morphology determination. We found that 15-HETE promoted HUVEC angiogenesis, which were mediated by ERK. Moreover, 15-HETE-induced proliferation and cell cycle transition from the G(0)/G(1) phase to the G(2)/M + S phase. All these effects were reversed after blocking ERK with PD98059 (an ERK inhibitor). In addition, HUVEC apoptosis was relieved by 15-HETE through the ERK pathway. Thus, ERK is necessary for the effects of 15-HETE in the regulation of HUVEC angiogenesis, which may be a novel potential target for the treatment of angiogenesis-related diseases.

Surface Chemical Gradient Affects the Differentiation of Human Adipose-Derived Stem Cells via ERK1/2 Signaling Pathway

To understand the role of surface chemistry on cell behavior and the associated molecular mechanisms, we developed and utilized a surface chemical gradient of amine functional groups by carefully adjusting the gas composition of 1,7-octadiene (OD) and allylamine (AA) of the plasma phase above a moving substrate. The chemical gradient surface used in the present work shows an increasing N/C ratio and wettability from the OD side toward the AA side with no change in surface topography. Under standard culture conditions (with serum), human adipose-derived stem cells (hASCs) adhesion and spreading area increased toward the AA side of the gradient. However, there were no differences in cell behavior in the absence of serum. These results, supported by the trends in proteins adsorption on the gradient surface, demonstrated that surface chemistry affects the response of hASCs through cell-adhesive serum proteins, rather than interacting directly with the cells. The expression of p-ERK and the osteogenic differentiation increased toward the AA side of the gradient, while adipogenic differentiation decreased in the same direction; however, when the activation of ERK1/2 was blocked by PD98059, the levels of osteogenic or adipogenic differentiation on different regions of the chemical gradient were the same. This indicates that ERK1/2 may be an important downstream signaling pathway of surface chemistry directed stem cell fate.

A comparison of the in vitro mineralisation and dentinogenic potential of mesenchymal stem cells derived from adipose tissue, bone marrow and dental pulp

Stem-cell-based therapies provide a biological basis for the regeneration of mineralised tissues. Stem cells isolated from adipose tissue (ADSCs), bone marrow (BMSCs) and dental pulp (DPSCs) have the capacity to form mineralised tissue. However, studies comparing the capacity of ADSCs with BMSCs and DPSCs for mineralised tissue engineering are lacking, and their ability to regenerate dental tissues has not been fully explored. Characterisation of the cells using fluorescence-activated cell sorting and semi-quantitative reverse transcription PCR for MSC markers indicated that they were immunophenotypically similar. Alizarin red (AR) staining and micro-computed tomography (µCT) analyses demonstrated that the osteogenic potential of DPSCs was significantly greater than that of BMSCs and ADSCs. Scanning electron microscopy and AR staining showed that the pattern of mineralisation in DPSC cultures differed from ADSCs and BMSCs, with DPSC cultures lacking defined mineralised nodules and instead forming a diffuse layer of low-density mineral. Dentine matrix components (DMCs) were used to promote dentinogenic differentiation. Their addition to cultures resulted in increased amounts of mineral deposited in all three cultures and significantly increased the density of mineral deposited in BMSC cultures, as determined by µCT analysis. Addition of DMCs also increased the relative gene expression levels of the dentinogenic markers dentine sialophosphoprotein and dentine matrix protein 1 in ADSC and BMSC cultures. In conclusion, DPSCs show the greatest potential to produce a comparatively high volume of mineralised matrix; however, both dentinogenesis and mineral volume was enhanced in ADSC and BMSC cultures by DMCs, suggesting that these cells show promise for regenerative dental therapies.