Structure of periodontal tissues in health and disease

Efficacy of nanoceria for periodontal tissues alteration in glutamate-induced obese rats-multidisciplinary considerations for personalized dentistry and prevention

BACKGROUND

Nowadays, we face the global epidemic of obesity, that is known to contribute to the development of many diseases, such as the oral cavity pathologies. Dental and oral pathologies are frequently caused by and overlapped with systemic multifactorial diseases such as obesity being its early indicators and risk factors. The aim was to study the influence of nanoceria on periodontal tissues alteration in glutamate (MSG)-induced obese rats.

METHODS

We included 52 Wistar rats of both genders and divided into four groups: newborn rats in group 1 (control) received subcutaneously 8 μl/g saline. Group 2 received 3 to 4 mg/g MSG subcutaneously on the second, fourth, sixth, eighth, and tenth day of life; group 3-intragastric administration of nanocrystalline cerium dioxide at a dose of 1 mg/kg volume of 2.9 ml/kg against the background of glutamate-induced obesity; the fourth group of animals was treated with a solution of sodium citrate intragastric volume of 2.9 ml/kg (solvent of nanocrystalline cerium). We determined the total proteolytic activity, the total antitrypsin activity, the content-free fucose and glycosaminoglycanes (GAG), content of TBA-active of products, the content of oxidation-modified proteins (OMB), and catalase activity in the homogenate of soft periodontal tissues of rats.

RESULTS

Intragastric injection of nanoceria prevents activation of proteolytic processes, reducing the catabolism of glycoproteins and proteoglycans of periodontal tissue in MSG-induced obese rats. Injection of nanoceria prevents activation of proteolytic processes, significantly decreases the total proteolytic activity, and inhibits the activation of free radical oxidation in periodontal tissues of rats compared with MSG-induced obesity model without corrections. Further, it significantly increases the total antitrypsin activity in periodontal tissues by 1.7 times, TBA-reagents by 1.7 times, and content of OMB by 1.4 times compared with glutamate-induced obese animals.

CONCLUSIONS

MSG-induced obesity triggers periodontal tissue alterations in the rat model. Nanoceria contributes to the corrections of pathological changes in periodontal tissues in glutamate-induced obese rats via balancing protein-inhibitory capacity and reducing the depolymerization of fucosylated proteins and proteoglycans and antioxidative activity.

F-spondin negatively regulates dental follicle differentiation through the inhibition of TGF-β activity

OBJECTIVE

F-spondin is an extracellular matrix (ECM) protein that belongs to the thrombospondin type I repeat superfamily and is a negative regulator of bone mass. We have previously shown that f-spondin is specifically expressed in the dental follicle (DF), which gives rise to the periodontal ligament (PDL) during the tooth root formation stage. To investigate the molecular mechanism of PDL formation, we investigated the function of f-spondin in DF differentiation.

DESIGN

The expression patterning of f-spondin in the developing tooth germ was compared with that of periodontal ligament-related genes, including runx2, type I collagen and periostin, by in situ hybridization analysis. To investigate the function of f-spondin during periodontal ligament formation, an f-spondin adenovirus was infected into the bell stage of the developing tooth germ, and the effect on dental differentiation was analyzed.

RESULTS

F-spondin was specifically expressed in the DF of the developing tooth germ; by contrast, type I collagen, runx2 and periostin were expressed in the DF and in the alveolar bone. F-spondin-overexpresssing tooth germ exhibited a reduction in gene expression of periostin and type I collagen in the DF. By contrast, the knockdown of f-spondin in primary DF cells increased the expression of these genes. Treatment with recombinant f-spondin protein functionally inhibited periostin expression induced by transforming growth factor-β (TGF-β).

CONCLUSION

Our data indicated that f-spondin inhibits the differentiation of DF cells into periodontal ligament cells by inhibiting TGF-β. These data suggested that f-spondin negatively regulates PDL differentiation which may play an important role in the immature phenotype of DF.

Xenogeneic Bio-Root Prompts the Constructive Process Characterized by Macrophage Phenotype Polarization in Rodents and Nonhuman Primates

Tissue or organ regeneration using xenogeneic matrices is a promising approach to address the shortage of donor matrices for allotransplantation. Success of such approach has been demonstrated to correlate with macrophage-mediated fibrotic homeostasis and tissue remodeling. The previous studies have demonstrated that treated dentin matrix (TDM) could be a suitable bioactive substrate for allogeneic tooth root regeneration. This study constructed xenogeneic bioengineered tooth root (bio-root) via a combination of porcine TDM (pTDM) with allogeneic dental follicle cells (DFCs). Macrophage phenotypes are used to evaluate the remodeling process of xenogeneic bio-roots in vitro and in vivo. pTDM can facilitate odontoblast differentiation of human derived DFCs. Xenogeneic bio-roots in rat subcutaneous tissue prompt constructive response via M1 macrophage infiltration during early postimplantation stages and increase restorative M2 phenotype at later stages. After implantation of bio-roots into jaws of rhesus monkeys for six months, periodontal ligament-like fibers accompanied by macrophage polarization are observed, which are positive for COL-1, Periostin, βIII-tubulin and display such structures as fibroblasts and blood vessels. The reconstructed bio-root possesses biomechanical properties for the dissipation of masticatory forces. These results support that xenogeneic bio-root could maintain fibrotic homeostasis during remodeling process and highlight the potential application of xenogeneic matrices in regenerative medicine.

Reduced platelet hyper-reactivity and platelet-leukocyte aggregation after periodontal therapy

Background

Platelets from untreated periodontitis patients are hyper-reactive and form more platelet-leukocyte complexes compared to cells from individuals without periodontitis. It is not known whether the improvement of the periodontal condition achievable by therapy has beneficial effects on the platelet function. We aimed to assess the effects of periodontal therapy on platelet reactivity.

Methods

Patients with periodontitis (n = 25) but unaffected by any other medical condition or medication were included and donated blood before and after periodontal therapy. Reactivity to ADP or oral bacteria was assessed by flow cytometric analysis of membrane markers (binding of PAC-1, P-selectin, CD63) and platelet-leukocyte complex formation. Reactivity values were expressed as ratio between the stimulated and unstimulated sample. Plasma levels of soluble (s) P-selectin were determined by enzyme-linked immunosorbent assay (ELISA).

Results

Binding of PAC-1, the expression of P-selectin and CD63 in response to the oral bacterium P. gingivalis were lower at recall (1.4 ± 1.1, 1.5 ± 1.2, and 1.0 ± 0.1) than at baseline (2.7 ± 4.1, P = 0.026, 6.0 ± 12.5, P = 0.045, and 2.7 ± 6.7, P = 0.042, respectively). Formation of platelet-leukocyte complexes in response to P. gingivalis was also reduced at recall compared to baseline (1.2 ± 0.7 vs. 11.4 ± 50.5, P = 0.045). sP-selectin levels were significantly increased post-therapy.

Conclusions

In periodontitis patients, the improvement of the periodontal condition is paralleled by a reduction in platelet hyper-reactivity. We suggest that periodontal therapy, as an intervention for improved oral health, can facilitate the management of thrombotic risk, and on the long term can contribute to the prevention of cardiovascular events in patients at risk.

Trial registration

Current Controlled Trials identifier ISRCTN36043780. Retrospectively registered 25 September 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s12959-016-0125-x) contains supplementary material, which is available to authorized users.

Periodontal tissue engineering: current strategies and the role of platelet rich hemoderivatives

Periodontal tissue engineering procures to regenerate the periodontal tissue assuring the right combination of scaffolds, biochemical cues and cells. The platelet rich hemoderivatives might provide the adequate growth factors and structural proteins for the predictable regeneration of periodontium.

Surgical treatment of cementoblastoma associated with apicoectomy and endodontic therapy: Case report

This case report describes the surgical removal of cementoblastoma associated with apicoectomy and endodontic therapy. The patient, an 18-year-old man, presented pain in the region of the mandibular body on the right side. On clinical exam, bone expansion was observed in the region at the bottom of the vestibular sulcus, pain on palpation, slight extrusion of tooth 46 with presence of pulp vitality. Radiographic exams demonstrated the presence of a radiopaque area and discrete radiolucent halo associated with the root of tooth 46, suggesting the diagnosis of cementoblastoma. Endodontic treatment of tooth 46 was performed and exeresis of the lesion by apicoectomy. Twelve months after the first surgery, recurrence of the lesion was observed, and a new apicoectomy was necessary, this time up to the middle third of the root. Clinical radiographic control 12 mo after the second surgical intervention demonstrated absence of signs and symptoms, radiographic repair, with tooth 46 shown to be fully functional.

Histology of human cementum: Its structure, function, and development

Cementum was first demonstrated by microscopy, about 180 years ago. Since then the biology of cementum has been investigated by the most advanced techniques and equipment at that time in various fields of dental sciences. A great deal of data on cementum histology have been accumulated. These data have been obtained from not only human, but also non-human animals, in particular, rodents such as the mouse and rat. Although many dental histologists have reviewed histology of human cementum, some descriptions are questionable, probably due to incorrect comparison of human and rodent cementum. This review was designed to introduce current histology of human cementum, i.e. its structure, function, and development and to re-examine the most questionable and controversial conclusions made in previous reports.

Nuclear translocation of PKCα isoenzyme is involved in neurogenic commitment of human neural crest-derived periodontal ligament stem cells

Stem cells isolated from human adult tissue niche represent a promising source for neural differentiation. Human Periodontal Ligament Stem Cells (hPDLSCs) originating from the neural crest are particularly suitable for induction of neural commitment. In this study, under xeno-free culture conditions, in undifferentiated hPDLSCs and in hPDLSCs induced to neuronal differentiation by basic Fibroblast Growth Factor, the level of some neural markers have been analyzed. The hPDLSCs spontaneously express Nestin, a neural progenitor marker. In these cells, the neurogenic process induced to rearrange the cytoskeleton, form neurospheres and express higher levels of Nestin and Tyrosine Hydroxylase, indicating neural induction. Protein Kinase C (PKC) is highly expressed in neural tissue and has a key role in neuronal functions. In particular the Ca(2+) and diacylglycerol-dependent activation of PKCα isozyme is involved in the regulation of neuronal differentiation. Another main component of the pathways controlling neuronal differentiation is the Growth Associated Protein-43 (GAP-43), whose activity is strictly regulated by PKC. The aim of this study is to investigate the role of PKCα/GAP-43 nuclear signal transduction pathway during neuronal commitment of hPDLSCs. During hPDLSCs neurogenic commitment the levels of p-PKC and p-GAP-43 increased both in cytoplasmic and nuclear compartment. PKCα nuclear translocation induced GAP-43 movement to the cytoplasm, where it is known to regulate growth cone dynamics and neuronal differentiation. Moreover, the degree of cytosolic Ca(2+) mobilization appeared to be more pronounced in differentiated hPDLSCs than in undifferentiated cells. This study provides evidences of a new PKCα/GAP-43 nuclear signalling pathway that controls neuronal differentiation in hPDLSCs, leading the way to a potential use of these cells in cell-based therapy in neurodegenerative diseases.

Assessment of periodontal mechano-nociceptive function in healthy Chinese individuals

OBJECTIVE

Few clinical techniques are available for the description of mechano-nociceptive function in human periodontal tissues. The objective of this study was to test a new technique for assessment of periodontal mechano-nociceptive function by direct application of controlled forces to the teeth and quantify site, side and gender differences in healthy individuals.

DESIGN

Twenty healthy young adults (ten males and ten females) participated. A handheld pressure algometer was used to assess pressure pain threshold (PPT) on the maxillary and mandibular central incisors, canines and first premolars on the left and the right side from two directions: lateral and vertical. Statistical analysis was performed using analyses of variance (ANOVA) with repeated measures to compare data.

RESULTS

There were significant gender differences of PPT for both lateral (P_lateral=0.007) and vertical (P_vertical=0.001) directions with lower thresholds in females (higher sensitivity) than in males. A significant site effect (P_lateral=0.002, P_vertical<0.001) was observed with less sensitivity at the first premolar compared to the anterior teeth. No significant right-to-left side differences (P=0.082) were found for the PPTs. There were significant PPT differences between maxillary and mandibular teeth (P_lateral=0.020, P_vertical=0.041,) and significant differences between lateral and vertical direction (P<0.001).

CONCLUSION

The novel application of PPTs directly to the teeth indicated an adequate and practical method with potential value for clinical assessment of painful conditions affecting the periodontal ligament.

Filifactor alocis collagenase can modulate apoptosis of normal oral keratinocytes

To successfully colonize host cells, pathogenic bacteria must circumvent the host's structural barrier such as the collagen-rich extracellular matrix (ECM), as a preliminary step to invasion and colonization of the periodontal tissue. Filifactor alocis possesses a putative Peptidase U32 family protein (HMPREF0389_00504) with collagenase activity that may play a significant role in colonization of host tissue during periodontitis by breaking down collagen into peptides and disruption of the host cell. Domain architecture of the HMPREF0389_00504 protein predicted the presence of a characteristic PrtC-like collagenase domain, and a peptidase domain. Our study demonstrated that the recombinant F. alocis peptidase U32 protein (designated PrtFAC) can interact with, and degrade, type I collagen, heat-denatured collagen and gelatin in a calcium-dependent manner. PrtFAC decreased viability and induced apoptosis of normal oral keratinocytes (NOKs) in a time and dose-dependent manner. Transcriptome analysis of NOK cells treated with PrtFAC showed an upregulation of the genes encoding human pro-apoptotic proteins: Apoptotic peptidase activating factor 1 (Apaf1) cytochrome C, as well as caspase 3 and caspase 9, suggesting the involvement of the mitochondrial apoptotic pathway. There was a significant increase in caspase 3/7 activity in NOK cells treated with PrtFAC. Taken together, these findings suggest that F. alocis PrtFAC protein may play a role in the virulence and pathogenesis of F. alocis.

Combination of Bioactive Polymeric Membranes and Stem Cells for Periodontal Regeneration: In Vitro and In Vivo Analyses

Regeneration of periodontal tissues requires a concerted effort to obtain consistent and predictable results in vivo. The aim of the present study was to test a new family of bioactive polymeric membranes in combination with stem cell therapy for periodontal regeneration. In particular, the novel polyester poly(isosorbide succinate-co-L-lactide) (PisPLLA) was compared with poly(L-lactide) (PLLA). Both polymers were combined with collagen (COL), hydroxyapatite (HA) and the growth factor bone morphogenetic protein-7 (BMP7), and their osteoinductive capacity was evaluated via in vitro and in vivo experiments. Membranes composed of PLLA/COL/HA or PisPLLA/COL/HA were able to promote periodontal regeneration and new bone formation in fenestration defects in rat jaws. According to quantitative real-time polymerase chain reaction (qRT-PCR) and Alizarin Red assays, better osteoconductive capacity and increased extracellular mineralization were observed for PLLA/COL/HA, whereas better osteoinductive properties were associated with PisPLLA/COL/HA. We concluded that membranes composed of either PisPLLA/COL/HA or PLLA/COL/HA present promising results in vitro as well as in vivo and that these materials could be potentially applied in periodontal regeneration.

Endogenous hydrogen sulfide is involved in osteogenic differentiation in human periodontal ligament cells

OBJECTIVE

Endogenous hydrogen sulfide (H2S) has recently emerged as an important intracellular gaseous signaling molecule within cellular systems. Endogenous H2S is synthesized from l-cysteine via cystathionine β-synthase and cystathionine γ-lyase and it regulates multiple signaling pathways in mammalian cells. Indeed, aberrant H2S levels have been linked to defects in bone formation in experimental mice. The aim of this study was to examine the potential production mechanism and function of endogenous H2S within primary human periodontal ligament cells (PDLCs).

DESIGN

Primary human PDLCs were obtained from donor molars with volunteer permission. Immunofluorescent labeling determined expression of the H2S synthetase enzymes. These enzymes were inhibited with D,L-propargylglycine or hydroxylamine to examine the effects of H2S signaling upon the osteogenic differentiation of PDLCs. Gene and protein expression levels of osteogenic markers in conjunction with ALP staining and activity and alizarin red S staining of calcium deposition were used to assay the progression of osteogenesis under different treatment conditions. Cultures were exposed to Wnt3a treatment to assess downstream signaling mechanisms.

RESULTS

In this study, we show that H2S is produced by human PDLCs via the cystathionine β-synthase/cystathionine γ-lyase pathway to promote their osteogenic differentiation. These levels must be carefully maintained as excessive or deficient H2S levels temper the observed osteogenic effect by inhibiting Wnt/β-catenin signaling.

CONCLUSIONS

These results demonstrate that optimal concentrations of endogenous H2S must be maintained within PDLCs to promote osteogenic differentiation by activating the Wnt/β-catenin signaling cascade.

Biomimetic strategies for engineering composite tissues

The formation of multiple tissue types and their integration into composite tissue units presents a frontier challenge in regenerative engineering. Tissue-tissue synchrony is crucial in providing structural support for internal organs and enabling daily activities. This review highlights the state-of-the-art in composite tissue scaffold design, and explores how biomimicry can be strategically applied to avoid over-engineering the scaffold. Given the complexity of biological tissues, determining the most relevant parameters for recapitulating native structure-function relationships through strategic biomimicry will reduce the burden for clinical translation. It is anticipated that these exciting efforts in composite tissue engineering will enable integrative and functional repair of common soft tissue injuries and lay the foundation for total joint or limb regeneration.

Potential Role of Long Non-Coding RNA in Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

BACKGROUND

Long non-coding RNAs (lncRNAs) are emerging as important regulators of eukaryotic gene expression and have been shown to regulate various modular components of development and differentiation. However, the roles of lncRNAs in the regulation of osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) remain poorly understood.

METHODS

Expression patterns of lncRNA and messenger RNA (mRNA) during osteogenic differentiation were profiled using microarray analysis. Quantitative reverse transcription polymerase chain reaction was performed to validate the microarray data. Biologic functions of candidates were revealed by: 1) cluster analysis; 2) gene ontology (GO); and 3) pathway analysis. Coding-non-coding gene coexpression (CNC) networks were constructed to investigate potential regulatory roles of lncRNAs and osteogenesis-related mRNAs.

RESULTS

After osteoinduction, 3,557 mRNAs and 2,171 lncRNAs were differentially expressed, of which 994 lncRNAs were upregulated and 1,177 were downregulated (fold change >2.0 or <-2.0; P <0.05). Cluster analysis showed that lncRNAs and mRNAs from the experimental and control groups belonged to different clusters. GO analysis demonstrated that: 1) cellular process; 2) biologic regulation; and 3) regulation of biologic process were the most significant groups related to induction. Pathway analysis indicated that 83 pathways corresponded to differentially expressed mRNAs, including: 1) mitogen-activated protein kinase; 2) vascular endothelial growth factor; and 3) transforming growth factor-β signaling pathways. CNC network analysis indicated that 393 lncRNAs were closely related to osteogenesis-related mRNAs.

CONCLUSIONS

Expression profiles of lncRNAs and mRNAs were significantly altered during osteogenic differentiation of hPDLSCs. This result suggests that lncRNAs may play crucial roles in this process and could regulate mRNA expression.

Small-Scale Fabrication of Biomimetic Structures for Periodontal Regeneration

The periodontium is the supporting tissues for the tooth organ and is vulnerable to destruction, arising from overpopulating pathogenic bacteria and spirochaetes. The presence of microbes together with host responses can destroy large parts of the periodontium sometimes leading tooth loss. Permanent tissue replacements are made possible with tissue engineering techniques. However, existing periodontal biomaterials cannot promote proper tissue architectures, necessary tissue volumes within the periodontal pocket and a "water-tight" barrier, to become clinically acceptable. New kinds of small-scale engineered biomaterials, with increasing biological complexity are needed to guide proper biomimetic regeneration of periodontal tissues. So the ability to make compound structures with small modules, filled with tissue components, is a promising design strategy for simulating the anatomical complexity of the periodotium attachment complexes along the tooth root and the abutment with the tooth collar. Anatomical structures such as, intima, adventitia, and special compartments such as the epithelial cell rests of Malassez or a stellate reticulum niche need to be engineered from the start of regeneration to produce proper periodontium replacement. It is our contention that the positioning of tissue components at the origin is also necessary to promote self-organizing cell-cell connections, cell-matrix connections. This leads to accelerated, synchronized and well-formed tissue architectures and anatomies. This strategy is a highly effective preparation for tackling periodontitis, periodontium tissue resorption, and to ultimately prevent tooth loss. Furthermore, such biomimetic tissue replacements will tackle problems associated with dental implant support and perimimplantitis.

Bifunctional bioceramics stimulating osteogenic differentiation of a gingival fibroblast and inhibiting plaque biofilm formation

A bifunctional Ca–Mg–Si bioceramic induces osteogenic differentiation of gingival fibroblasts and inhibits plaque biofilm formation.

Neutrophil proteolytic activation cascades: a possible mechanistic link between chronic periodontitis and coronary heart disease

Cardiovascular diseases are chronic inflammatory diseases that affect a large segment of society. Coronary heart disease (CHD), the most common cardiovascular disease, progresses over several years and affects millions of people worldwide. Chronic infections may contribute to the systemic inflammation and enhance the risk for CHD. Periodontitis is one of the most common chronic infections that affects up to 50% of the adult population. Under inflammatory conditions the activation of endogenous degradation pathways mediated by immune responses leads to the release of destructive cellular molecules from both resident and immigrant cells. Matrix metalloproteinases (MMPs) and their regulators can activate each other and play an important role in immune response via degrading extracellular matrix components and modulating cytokines and chemokines. The action of MMPs is required for immigrant cell recruitment at the site of inflammation. Stimulated neutrophils represent the major pathogen-fighting immune cells that upregulate expression of several proteinases and oxidative enzymes, which can degrade extracellular matrix components (e.g. MMP-8, MMP-9 and neutrophil elastase). The activity of MMPs is regulated by endogenous inhibitors and/or candidate MMPs (e.g. MMP-7). The balance between MMPs and their inhibitors is thought to mirror the proteolytic burden. Thus, neutrophil-derived biomarkers, including myeloperoxidase, may activate proteolytic destructive cascades that are involved in subsequent immune-pathological events associated with both periodontitis and CHD. Here, we review the existing studies on the contribution of MMPs and their regulators to the infection-related pathology. Also, we discuss the possible proteolytic involvement and role of neutrophil-derived enzymes as an etiological link between chronic periodontitis and CHD.

TlR expression profile of human gingival margin-derived stem progenitor cells

BACKGROUND

Gingival margin-derived stem/progenitor cells (G-MSCs) show remarkable periodontal regenerative potential in vivo. During regeneration, G-MSCs may interact with their inflammatory environment via toll-like-receptors (TLRs). The present study aimed to depict the G-MSCs TLRs expression profile.

MATERIAL AND METHODS

Cells were isolated from free gingival margins, STRO-1-immunomagnetically sorted and seeded to obtain single colony forming units (CFUs). G-MSCs were characterized for CD14, CD34, CD45, CD73, CD90, CD105, CD146 and STRO-1 expression, and for multilineage differentiation potential. Following G-MSCs' incubation in basic or inflammatory medium (IL-1β, IFN-γ, IFN-α, TNF-α) a TLR expression profile was generated.

RESULTS

G-MSCs showed all stem/progenitor cells' characteristics. In basic medium G-MSCs expressed TLRs 1, 2, 3, 4, 5, 6, 7, and 10. The inflammatory medium significantly up-regulated TLRs 1, 2, 4, 5, 7 and 10 and diminished TLR 6 (p≤0.05, Wilcoxon-Signed-Ranks-Test).

CONCLUSIONS

The current study describes for the first time the distinctive TLRs expression profile of G-MSCs under uninflamed and inflamed conditions.

Androgen receptors and experimental bone loss - an in vivo and in vitro study

Testosterone is a sex hormone that exhibits many functions beyond reproduction; one such function is the regulation of bone metabolism. The role played by androgen receptors during testosterone-mediated biological processes associated with bone metabolism is largely unknown. This study aims to use a periodontal disease model in vivo in order to assess the involvement of androgen receptors on microbial-induced inflammation and alveolar bone resorption in experimental bone loss. The impact of hormone deprivation was tested through both orchiectomy and chemical blockage of androgen receptor using flutamide (FLU). Additionally, the direct effect of exogenous testosterone, and the role of the androgen receptor, on osteoclastogenesis were investigated. Thirty male adult rats (n=10/group) were subjected to: 1-orchiectomy (OCX); 2-OCX sham surgery; or 3-OCX sham surgery plus FLU, four weeks before the induction of experimental bone loss. Ten OCX sham-operated rats were not subjected to experimental bone loss and served as healthy controls. The rats were euthanized two weeks later, so as to assess bone resorption and the production of inflammatory cytokines in the gingival tissue and serum. In order to study the in vitro impact of testosterone, osteoclasts were differentiated from RAW264.7 cells and testosterone was added at increasing concentrations. Both OCX and FLU increased bone resorption, but OCX alone was observed to increase osteoclast count. IL-1β production was increased only in the gingival tissue of OCX animals, whereas FLU-treated animals presented a decreased expression of IL-6. Testosterone reduced the osteoclast formation in a dose-dependent manner, and significantly impacted the production of TNF-α; FLU partially reversed these actions. When taken together, our results indicate that testosterone modulates experimental bone loss, and that this action is mediated, at least in part, via the androgen receptor.

Regenerative Medicine for Periodontal and Peri-implant Diseases

The balance between bone resorption and bone formation is vital for maintenance and regeneration of alveolar bone and supporting structures around teeth and dental implants. Tissue regeneration in the oral cavity is regulated by multiple cell types, signaling mechanisms, and matrix interactions. A goal for periodontal tissue engineering/regenerative medicine is to restore oral soft and hard tissues through cell, scaffold, and/or signaling approaches to functional and aesthetic oral tissues. Bony defects in the oral cavity can vary significantly, ranging from smaller intrabony lesions resulting from periodontal or peri-implant diseases to large osseous defects that extend through the jaws as a result of trauma, tumor resection, or congenital defects. The disparity in size and location of these alveolar defects is compounded further by patient-specific and environmental factors that contribute to the challenges in periodontal regeneration, peri-implant tissue regeneration, and alveolar ridge reconstruction. Efforts have been made over the last few decades to produce reliable and predictable methods to stimulate bone regeneration in alveolar bone defects. Tissue engineering/regenerative medicine provide new avenues to enhance tissue regeneration by introducing bioactive models or constructing patient-specific substitutes. This review presents an overview of therapies (e.g., protein, gene, and cell based) and biomaterials (e.g., resorbable, nonresorbable, and 3-dimensionally printed) used for alveolar bone engineering around teeth and implants and for implant site development, with emphasis on most recent findings and future directions.

Proteomic profiling of host-biofilm interactions in an oral infection model resembling the periodontal pocket

Periodontal infections cause inflammatory destruction of the tooth supporting tissues. We recently developed a dynamic, in vitro periodontal organotypic tissue model in a perfusion bioreactor system, in co-culture with an 11-species subgingival biofilm, which may recapitulate early events during the establishment of periodontal infections. This study aimed to characterize the global proteome regulations in this host-biofilm interaction model. Semi-quantitative shotgun proteomics were applied for protein identification and quantification in the co-culture supernatants (human and bacterial) and the biofilm lysates (bacterial). A total of 896 and 3363 proteins were identified as secreted in the supernatant and expressed in the biofilm lysate, respectively. Enriched gene ontology analysis revealed that the regulated secreted human tissue proteins were related to processes of cytoskeletal rearrangement, stress responses, apoptosis, and antigen presentation, all of which are commensurate with deregulated host responses. Most secreted bacterial biofilm proteins derived from their cytoplasmic domain. In the presence of the tissue, the levels of Fusobacterium nucleatum, Actinomyces oris and Campylobacter rectus proteins were significantly regulated. The functions of the up-regulated intracellular (biofilm lysate) proteins were associated with cytokinesis. In conclusion, the proteomic overview of regulated pathways in this host-biofilm interaction model provides insights to the early events of periodontal pathogenesis.

Comparative study of detection of bacteremia after different oral surgical procedures

Introduction:

The purpose of this study is to compare the efficiency of culture methods in detecting microorganisms appearing in the bloodstream after various oral surgical procedures and effect of preoperative antibiotics and antiseptic rinses on bacteremia.

Materials and Methods:

The prevalence of bacteremia at various intervals of time (pre- and post-surgical) was studied in three different groups presenting with indications to surgical intervention. Two of the groups were given presurgical prophylaxis (systemic antibiotic and antiseptic rinse) while, in one group, no prophylactic measure was adopted. Blood samples were withdrawn from the subjects at specific pre- and post-surgical time intervals, and microbiological analysis was done. The findings were compared with a control group involving healthy individuals and a group involved in maxillofacial trauma where the breach of oral mucosal integrity was not surgically planned.

Results:

The presence of bacteremia was not observed in all five groups at baseline while postsurgery (30 min, 60 min, and 90 min) in only three groups (preoperative antibiotic, without prophylaxis, and 1% Povidone iodine rinse). At all postsurgery periods (30 min, 60 min and 90 min), the presence of bacteremia was evident highest in without prophylaxis group followed by 1% Povidone iodine rinse and preoperative antibiotic the least.

Sol–gel processing of novel bioactive Mg-containing silicate scaffolds for alveolar bone regeneration

Periodontal tissue regeneration is an important application area of biomaterials, given the large proportion of the population affected by periodontal diseases like periodontitis. The aim of this study was the synthesis of a novel porous bioceramic scaffold in the SiO2–CaO–MgO system with specific properties targeted for alveolar bone tissue regeneration using a modification of the traditional foam replica technique. Since bioceramic scaffolds are considered brittle, scaffolds were also coated with gelatin in order to increase their mechanical stability. Gelatin was chosen for its biocompatibility, biodegradability, low-cost, and low immunogenicity. However, gelatin degrades very fast in water solutions. For this reason, two different cross-linking agents were evaluated. Genipin, a non-toxic gardenia extract and the chemical compound 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) in combination with N-hydroxysuccinimide (NHS), which is also considered non-toxic. The results of the investigation indicated that all scaffolds presented an open, interconnected porosity and pores' sizes in the range of 300–600 μm, fast apatite-forming ability, biocompatibility, and suitable mechanical stability.

Mechanisms of Bone Resorption in Periodontitis

Alveolar bone loss is a hallmark of periodontitis progression and its prevention is a key clinical challenge in periodontal disease treatment. Bone destruction is mediated by the host immune and inflammatory response to the microbial challenge. However, the mechanisms by which the local immune response against periodontopathic bacteria disturbs the homeostatic balance of bone formation and resorption in favour of bone loss remain to be established. The osteoclast, the principal bone resorptive cell, differentiates from monocyte/macrophage precursors under the regulation of the critical cytokines macrophage colony-stimulating factor, RANK ligand, and osteoprotegerin. TNF-α, IL-1, and PGE₂ also promote osteoclast activity, particularly in states of inflammatory osteolysis such as those found in periodontitis. The pathogenic processes of destructive inflammatory periodontal diseases are instigated by subgingival plaque microflora and factors such as lipopolysaccharides derived from specific pathogens. These are propagated by host inflammatory and immune cell influences, and the activation of T and B cells initiates the adaptive immune response via regulation of the Th1-Th2-Th17 regulatory axis. In summary, Th1-type T lymphocytes, B cell macrophages, and neutrophils promote bone loss through upregulated production of proinflammatory mediators and activation of the RANK-L expression pathways.

Tissue engineered periodontal products

Attainment of periodontal regeneration is a significant clinical goal in the management of advanced periodontal defects arising from periodontitis. Over the past 30 years numerous techniques and materials have been introduced and evaluated clinically and have included guided tissue regeneration, bone grafting materials, growth and other biological factors and gene therapy. With the exception of gene therapy, all have undergone evaluation in humans. All of the products have shown efficacy in promoting periodontal regeneration in animal models but the results in humans remain variable and equivocal concerning attaining complete biological regeneration of damaged periodontal structures. In the early 2000s, the concept of tissue engineering was proposed as a new paradigm for periodontal regeneration based on molecular and cell biology. At this time, tissue engineering was a new and emerging field. Now, 14 years later we revisit the concept of tissue engineering for the periodontium and assess how far we have come, where we are currently situated and what needs to be done in the future to make this concept a reality. In this review, we cover some of the precursor products, which led to our current position in periodontal tissue engineering. The basic concepts of tissue engineering with special emphasis on periodontal tissue engineering products is discussed including the use of mesenchymal stem cells in bioscaffolds and the emerging field of cell sheet technology. Finally, we look into the future to consider what CAD/CAM technology and nanotechnology will have to offer.

Development of the splanchnocranium in Prochilodus argenteus (Teleostei: Characiformes) with a discussion of the basal developmental patterns in the Otophysi

Development of the mandibular, hyoid and gill arches, which constitute the splanchnocranium, are described for Prochilodus argenteus, order Characiformes, one of the basal lineages of the Otophysi. Development was examined from just hatched larvae through juveniles using whole specimens cleared and counterstained for cartilage and bone as well as histological preparations. Observations are compared with the developmental trends reported for Cypriniformes, the basalmost clade of the Otophysi. Shortened developmental sequences for Prochilodus compared to the cypriniform Catostomus were discovered in the ontogeny of the ceratohyals, ceratobranchials 1-5, epibranchials 1-4 and the symplectic portion of the hyosymplectic. Prochilodus also differs from Catostomus in having the basihyal plus the anterior copula appearing at different stages of ontogeny rather than simultaneously. Contrary to previous assumptions, developmental information indicates that hypobranchial 4 as well as likely basibranchial 5 are present in Prochilodus. Various developmental patterns in Prochilodus considered basal for the Otophysi, the predominant component of the Ostariophysi, are likely conserved from patterns prevalent in basal groups in the Actinopterygii.

Cell-to-cell communication--periodontal regeneration

BACKGROUND

Although regenerative treatment options are available, periodontal regeneration is still regarded as insufficient and unpredictable.

AIM

This review article provides scientific background information on the animated 3D film Cell-to-Cell Communication - Periodontal Regeneration.

RESULTS

Periodontal regeneration is understood as a recapitulation of embryonic mechanisms. Therefore, a thorough understanding of cellular and molecular mechanisms regulating normal tooth root development is imperative to improve existing and develop new periodontal regenerative therapies. However, compared to tooth crown and earlier stages of tooth development, much less is known about the development of the tooth root. The formation of root cementum is considered the critical element in periodontal regeneration. Therefore, much research in recent years has focused on the origin and differentiation of cementoblasts. Evidence is accumulating that the Hertwig's epithelial root sheath (HERS) has a pivotal role in root formation and cementogenesis. Traditionally, ectomesenchymal cells in the dental follicle were thought to differentiate into cementoblasts. According to an alternative theory, however, cementoblasts originate from the HERS. What happens when the periodontal attachment system is traumatically compromised? Minor mechanical insults to the periodontium may spontaneously heal, and the tissues can structurally and functionally be restored. But what happens to the periodontium in case of periodontitis, an infectious disease, after periodontal treatment? A non-regenerative treatment of periodontitis normally results in periodontal repair (i.e., the formation of a long junctional epithelium) rather than regeneration. Thus, a regenerative treatment is indicated to restore the original architecture and function of the periodontium. Guided tissue regeneration or enamel matrix proteins are such regenerative therapies, but further improvement is required. As remnants of HERS persist as epithelial cell rests of Malassez in the periodontal ligament, these epithelial cells are regarded as a stem cell niche that can give rise to new cementoblasts. Enamel matrix proteins and members of the transforming growth factor beta (TGF-ß) superfamily have been implicated in cementoblast differentiation.

CONCLUSION

A better knowledge of cell-to-cell communication leading to cementoblast differentiation may be used to develop improved regenerative therapies to reconstitute periodontal tissues that were lost due to periodontitis.

Stimulatory effects of the fast setting and suitable degrading Ca–Si–Mg cement on both cementogenesis and angiogenesis differentiation of human periodontal ligament cells

The purpose of this study is to develop a fast setting and suitable degrading Mg–calcium silicate cement (Mg–CS) and a mechanism using Mg ions to stimulate human periodontal ligament cells (hPDLCs).

Cementum and Periodontal Ligament Regeneration

The unique anatomy and composition of the periodontium make periodontal tissue healing and regeneration a complex process. Periodontal regeneration aims to recapitulate the crucial stages of wound healing associated with periodontal development in order to restore lost tissues to their original form and function and for regeneration to occur, healing events must progress in an ordered and programmed sequence both temporally and spatially, replicating key developmental events. A number of procedures have been employed to promote true and predictable regeneration of the periodontium. Principally, the approaches are based on the use of graft materials to compensate for the bone loss incurred as a result of periodontal disease, use of barrier membranes for guided tissue regeneration and use of bioactive molecules. More recently, the concept of tissue engineering has been integrated into research and applications of regenerative dentistry, including periodontics, to aim to manage damaged and lost oral tissues, through reconstruction and regeneration of the periodontium and alleviate the shortcomings of more conventional therapeutic options. The essential components for generating effective cellular based therapeutic strategies include a population of multi-potential progenitor cells, presence of signalling molecules/inductive morphogenic signals and a conductive extracellular matrix scaffold or appropriate delivery system. Mesenchymal stem cells are considered suitable candidates for cell-based tissue engineering strategies owing to their extensive expansion rate and potential to differentiate into cells of multiple organs and systems. Mesenchymal stem cells derived from multiple tissue sources have been investigated in pre-clinical animal studies and clinical settings for the treatment and regeneration of the periodontium.

Differentiated embryonic chondrocytes 1 expression of periodontal ligament tissue and gingival tissue in the patients with chronic periodontitis

OBJECTIVE

To evaluate the DEC1 expression of periodontal ligament tissue and gingival tissue in the patients with chronic periodontitis.

METHODS

20 non-smoking patients with chronic periodontitis and 20 healthy individuals were enrolled. Periodontal ligament tissue and gingival tissue samples from healthy subjects were collected during teeth extraction for orthodontic reason or the third molar extraction. The parallel samples from patients with chronic periodontitis were obtained during periodontal flap operations or teeth extraction as part of periodontal treatment. The DEC1 expression and the alkaline phosphatase (ALP) activity of both the periodontal ligament tissue and gingival tissue were determined by Western blot, Immunohistochemistry and ALP Detection Kit.

RESULTS

The DEC1 expression of periodontal ligament tissue in the patients with chronic periodontitis decreased significantly along with the decreased ALP activity. On the contrary, the DEC1 expression of gingival tissue in the patients with chronic periodontitis increased significantly. Further study found that the DEC1 expression of gingival tissue increased mainly in the suprabasal layer of gingival epithelial cells but decreased in the gingival connective tissue of the patients with chronic periodontitis.

CONCLUSION

The DEC1 expression decreases in the periodontal ligament tissue which is related to the osteogenic capacity, whereas the DEC1 expression increases in the suprabasal layer of gingival epithelial cells which are involved in immune inflammatory response in the patients with chronic periodontitis. The findings provide a new target to explore the pathology and the therapy of periodontitis.

Establishment and characterization of immortalized gingival epithelial and fibroblastic cell lines for the development of organotypic cultures

In vitro studies using 3D co-cultures of gingival cells can resemble their in vivo counterparts much better than 2D models that typically only utilize monolayer cultures with short-living primary cells. However, the use of 3D gingival models is still limited through lack of appropriate cell lines. We aimed to establish immortalized cell line models of primary human gingival epithelium keratinocytes (HGEK) and gingival fibroblasts (GFB). Immortalized cell lines (HGEK-16 and GFB-16) were induced by E6 and E7 oncoproteins of human papillomavirus. In addition, 3D multilayered organotypic cultures were formed by embedding GFB-16 cells within a collagen (Col) matrix and seeding of HGEK-16 cells on the upper surfaces. Cell growth was analyzed in both immortalized cell lines and their parental primary cells. The expression levels of cell type-specific markers, i.e. cytokeratin (CK) 10, CK13, CK16, CK18, CK19 for HGEK-16 and Col I and Col II for GFB-16, were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Expansion of the primary cultures was impeded at early passages, while the transformed immortalized cell lines could be expanded for more than 30 passages. In 3D cultures, immortalized HGEK formed a multilayer of epithelial cells. qRT-PCR showed that cell-specific marker expression in the 3D cultures was qualitatively and quantitatively closer to that in human gingival tissue than to monolayer cultures. These results indicate that immortalized gingival fibroblastic and epithelial cell lines can successfully form organotypic multilayered cultures and, therefore, may be useful tools for studying gingival tissue in vitro.

Enamel matrix derivative, inflammation and soft tissue wound healing

Over 15 years have now passed since enamel matrix derivative (EMD) emerged as an agent capable of periodontal regeneration. Following thorough investigation, evidenced-based clinical application is now established for a multitude of clinical settings to promote regeneration of periodontal hard tissues. Despite the large number of studies and review articles written on this topic, no single review has compiled the influence of EMD on tissue inflammation, an area of research that merits substantial attention in periodontology. The aim of the present review was to gather all studies that deal with the effects of EMD on tissue inflammation with particular interest in the cellular mechanisms involved in inflammation and soft tissue wound healing/resolution. The effects of EMD on monocytes, macrophages, lymphocytes, neutrophils, fibroblasts and endothelial cells were investigated for changes in cell behavior as well as release of inflammatory markers, including interleukins, prostaglandins, tumor necrosis factor-α, matrix metalloproteinases and members of the OPG-RANKL pathway. In summary, studies listed in this review have reported that EMD is able to significantly decrease interleukin-1b and RANKL expression, increase prostaglandin E2 and OPG expression, increase proliferation and migration of T lymphocytes, induce monocyte differentiation, increase bacterial and tissue debris clearance, as well as increase fibroplasias and angiogenesis by inducing endothelial cell proliferation, migration and capillary-like sprout formation. The outcomes from the present review article indicate that EMD is able to affect substantially the inflammatory and healing responses and lay the groundwork for future investigation in the field.

Dental follicle cells rescue the regenerative capacity of periodontal ligament stem cells in an inflammatory microenvironment

Aims

Periodontal ligament stem cells (PDLSCs) are one of the best candidates for periodontal regeneration. Their function could be impaired in periodontitis microenvironment. Dental follicle cells (DFCs), serving as precursor cells and mesenchymal stem cells, have intimate connection with PDLSCs. However, it is still unknown whether DFCs could provide a favorable microenvironment to improve the proliferation and differentiation capacity of PDLSCs from healthy subjects (HPDLSCs) and patients diagnosed with periodontitis (PPDLSCs).

Methods

HPDLSCs, PPDLSCs and DFCs were harvested and identified using microscopic and flow cytometric analysis. Then, the coculture systems of DFCs/HPDLSCs and DFCs/PPDLSCs were established with 0.4 µm transwell, in which all the detection indexs were obtained from HPDLSCs and PPDLSCs. The expression of stemness-associated genes was detected by real-time PCR, and the proliferation ability was assessed using colony formation and cell cycle assays. The osteogenic differentiation capacity was evaluated by real-time PCR, western blot, ALP activity, Alizarin Red S staining and calcium level analysis, while the adipogenic differentiation capacity was determined by real-time PCR and Oil Red O staining. The cell sheet formation in vitro was observed by HE staining and SEM, and the implantation effect in vivo was evaluated using HE staining and Masson’s trichrome staining.

Results

PPDLSCs had a greater proliferation capability but lower osteogenic and adipogenic potential than HPDLSCs. DFCs enhanced the proliferation and osteogenic/adipogenic differentiation of HPDLSCs and PPDLSCs to different degrees. Moreover, coculture with DFCs increased cell layers and extracellular matrix of HPDLSCs/PPDLSCs cell sheets in vitro and improved periodontal regeneration by HPDLSCs/PPDLSCs in vivo.

Conclusions

Our data suggest that the function of PPDLSCs could be damaged in the periodontitis microenvironment. DFCs appear to enhance the self-renewal and multi-differentiation capacity of both HPDLSCs and PPDLSCs, which indicates that DFCs could provide a beneficial microenvironment for periodontal regeneration using PDLSCs.

Decellularized periodontal ligament cell sheets with recellularization potential

The periodontal ligament is the key tissue facilitating periodontal regeneration. This study aimed to fabricate decellularized human periodontal ligament cell sheets for subsequent periodontal tissue engineering applications. The decellularization protocol involved the transfer of intact human periodontal ligament cell sheets onto melt electrospun polycaprolactone membranes and subsequent bi-directional perfusion with NH4OH/Triton X-100 and DNase solutions. The protocol was shown to remove 92% of DNA content. The structural integrity of the decellularized cell sheets was confirmed by a collagen quantification assay, immunostaining of human collagen type I and fibronectin, and scanning electron microscopy. ELISA was used to demonstrate the presence of residual basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and hepatocyte growth factor (HGF) in the decellularized cell sheet constructs. The decellularized cell sheets were shown to have the ability to support recellularization by allogenic human periodontal ligament cells. This study describes the fabrication of decellularized periodontal ligament cell sheets that retain an intact extracellular matrix and resident growth factors and can support repopulation by allogenic cells. The decellularized hPDL cell sheet concept has the potential to be utilized in future "off-the-shelf" periodontal tissue engineering strategies.

Periodontal disease and atherosclerosis

Atherosclerotic disease (AD) is one of the most important causes of morbidity and mortality in the world. It expresses inflammatory markers such as C-reactive protein (CRP) and can provoke arterial wall thickening, which can be evaluated using Doppler ultrasound. Risk factors associated with AD include diabetes mellitus, systemic arterial hypertension, dyslipidemia and smoking. More recently, periodontal disease (PD) has been identified as a factor related to AD. Periodontal disease has a high prevalence in the global population and the inflammatory process and bacterial activity at the periodontium appear to increase the risk of AD. Encouraging good oral hygiene can reduce expression of inflammatory markers of AD. A review of literature on PD, AD and inflammatory markers and the interrelationships between the two diseases was conducted using data published in articles indexed on the PUBMED, SCIELO and BIREME databases.

Hypoxia promotes CEMP1 expression and induces cementoblastic differentiation of human dental stem cells in an HIF-1-dependent manner

Cementum covering the tooth root provides attachment for the tooth proper to the surrounding alveolar bone via non-mineralized periodontal ligament (PDL). Cementum protein 1 (CEMP1) has been shown to induce a cementoblastic phenotype in cementoblast precursors cells of PDL. Oxygen availability is a critical signal for correct development of many tissues; however, its role in tooth root and periodontium development remains poorly understood. In this study, we demonstrated that reduced oxygen tension increased CEMP1 expression, mineral deposition, and alkaline phosphatase activity in human dental stem cells such as PDL stem cells and periapical follicular stem cells. Since an oxemic state is transduced by the transcription factor, hypoxia-inducible factor-1 (HIF-1), we performed experiments to determine whether this protein was responsible for the observed changes. We noted that when HIF-1 was activated by gene introduction or chemically, CEMP1 expression and mineralization increased. In contrast, when HIF-1α was silenced, CEMP1 expression and mineralization did not increase in vitro. Furthermore, we showed for the first time that mouse tooth root and periodontium development occurs partly under hypoxic conditions, particularly at the apical part and latently at the PDL space in vivo. Desferrioxamine, an HIF-1 stimulator, enhances CEMP1 expression in the mouse PDL space, suggesting that hypoxia affects cementogenesis of PDL cells lining the surface of the developing tooth root in an HIF-1-dependent manner. These results suggest that HIF-1 activators may have the ability to stimulate regeneration of the tooth root and cementum formation.

Advanced biomatrix designs for regenerative therapy of periodontal tissues

Periodontitis is an inflammatory disease that causes loss of the tooth-supporting apparatus, including periodontal ligament, cementum, and alveolar bone. A broad range of treatment options is currently available to restore the structure and function of the periodontal tissues. A regenerative approach, among others, is now considered the most promising paradigm for this purpose, harnessing the unique properties of stem cells. How to make full use of the body's innate regenerative capacity is thus a key issue. While stem cells and bioactive factors are essential components in the regenerative processes, matrices play pivotal roles in recapitulating stem cell functions and potentiating therapeutic actions of bioactive molecules. Moreover, the positions of appropriate bioactive matrices relative to the injury site may stimulate the innate regenerative stem cell populations, removing the need to deliver cells that have been manipulated outside of the body. In this topical review, we update views on advanced designs of biomatrices-including mimicking of the native extracellular matrix, providing mechanical stimulation, activating cell-driven matrices, and delivering bioactive factors in a controllable manner-which are ultimately useful for the regenerative therapy of periodontal tissues.

The effects of synthetic oligopeptide derived from enamel matrix derivative on cell proliferation and osteoblastic differentiation of human mesenchymal stem cells

Enamel matrix derivative (EMD) is widely used in periodontal tissue regeneration therapy. However, because the bioactivity of EMD varies from batch to batch, and the use of a synthetic peptide could avoid use from an animal source, a completely synthetic peptide (SP) containing the active component of EMD would be useful. In this study an oligopeptide synthesized derived from EMD was evaluated for whether it contributes to periodontal tissue regeneration. We investigated the effects of the SP on cell proliferation and osteoblast differentiation of human mesenchymal stem cells (MSCs), which are involved in tissue regeneration. MSCs were treated with SP (0 to 1000 ng/mL), to determine the optimal concentration. We examined the effects of SP on cell proliferation and osteoblastic differentiation indicators such as alkaline phosphatase activity, the production of procollagen type 1 C-peptide and osteocalcin, and on mineralization. Additionally, we investigated the role of extracellular signal-related kinases (ERK) in cell proliferation and osteoblastic differentiation induced by SP. Our results suggest that SP promotes these processes in human MSCs, and that ERK inhibitors suppress these effects. In conclusion, SP promotes cell proliferation and osteoblastic differentiation of human MSCs, probably through the ERK pathway.