In vitro analysis of mesenchymal stem cells derived from human teeth and bone marrow. Odontology. 2013;101:121-132. [PMID: 22772774 DOI: 10.1007/s10266-012-0075-0]

Dental pulp stem cells and the management of neurological diseases: An update

Medical research in regenerative medicine has brought promising perspectives for the use of stem cells in clinical trials. Stem cells are undifferentiated cells capable of multilineage differentiation and available in numerous sources in the human body. Dental pulp constitutes an attractive source of these cells since collecting mesenchymal stem cells from this site is a noninvasive practice that can be performed after a common surgical extraction of supernumerary or wisdom teeth. Thus, tissue sacrifice is very low and several cytotypes can be obtained owing to these cells' multipotency, in addition to the fact that they can be cryopreserved and stored for long periods. Mesenchymal stem cells have high proliferation rates, making them favorable for clinical application. These multipotent cells, present in biological waste, constitute an appropriate resource in the treatment of many neurological diseases.

[Effect of hypoxia on the biological characteristics of human dental follicle cells]

OBJECTIVE

This study aimed to investigate the effects of hypoxia on the characteristics of human dental follicle cells (hDFCs).

METHODS

The tissue explant collagenase method was used to isolate hDFCs from young permanent teeth. The immunofluorescence technique was used to detect cell surface markers, and the multi-differentiation potential was detected by multilineage differentiation induction assay. Then, the hypoxic microenvironment was physically mimicked, and the cells were divided into the normoxia group (20%O₂) and the hypoxia group (2%O₂). The effects of hypoxia on cell migration and proliferation were examined by Transwell chamber test and CCK-8 assay, respectively. The gene and protein expression levels of stemness-related markers at both oxygen concentrations were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot, respectively. After osteogenic induction of both groups, qRT-PCR was performed to evaluate the osteogenesis-related gene, and alizarin red staining was used to assess the formation of mineralized nodules.

RESULTS

With the multi-differentiation capacity of osteogenic cells, adipogenic cells, and nerves, hDFCs demonstrate strong stem cell characteristics and possess the criteria of mesenchymal stem cells, which can meet the requirements of seed cells in dental tissue engineering. Hypoxia was conducive to the maintenance of hDFC stemness. Hypoxia promoted the migration and proliferation of hDFCs. The hDFCs were induced to osteogenic differentiation under hypoxic conditions, thereby enhancing osteogenesis.

CONCLUSIONS

Hypoxic microenvironment plays an important role in maintaining the stemness and promoting the proliferation, migration, and differentiation of hDFCs. Thus, this microenvironment could also serve several important functions in future clinical applications.

Stem cells applications in bone and tooth repair and regeneration: New insights, tools, and hopes

The exploration of stem and progenitor cells holds promise for advancing our understanding of the biology of tissue repair and regeneration mechanisms after injury. This will also help in the future use of stem cell therapy for the development of regenerative medicine approaches for the treatment of different tissue-species defects or disorders such as bone, cartilages, and tooth defects or disorders. Bone is a specialized connective tissue, with mineralized extracellular components that provide bones with both strength and rigidity, and thus enable bones to function in body mechanical supports and necessary locomotion process. New insights have been added to the use of different types of stem cells in bone and tooth defects over the last few years. In this concise review, we briefly describe bone structure as well as summarize recent research progress and accumulated information regarding the osteogenic differentiation of stem cells, as well as stem cell contributions to bone repair/regeneration, bone defects or disorders, and both restoration and regeneration of bones and cartilages. We also discuss advances in the osteogenic differentiation and bone regeneration of dental and periodontal stem cells as well as in stem cell contributions to dentine regeneration and tooth engineering.

Taking the endochondral route to craniomaxillofacial bone regeneration: A logical approach?

The current golden standard for treatment of craniomaxillofacial critical size bone defects, autologous bone grafting, is associated with several disadvantages which have prompted an increased demand for alternatives. New solutions are emerging in the form of bone tissue engineering. This involves harvesting of multipotent mesenchymal stromal cells (MSCs), after which they can be differentiated towards the osteogenic lineage mimicking intramembranous bone formation. However, translating this approach from laboratory to clinic has met with limited success. Consequently, attention has shifted towards investigation of the alternative endochondral route of bone regeneration. At a first glance, this approach may not appear logical for maxillofacial bone regeneration as most bones in the face originate from intramembranous mechanisms. Therefore, the goal of this review is to discuss the sense and non-sense of exploring endochondral bone regeneration as a novel reconstructive option for craniomaxillofacial bone defects. The embryological origin of craniomaxillofacial bone structures and their repair mechanisms are introduced. Also, the potential of MSC-like cells, the neural crest-derived stem cells from craniomaxillofacial sources, are discussed with a focus on regeneration of bone defects. Further, the current status of endochondral bone regeneration from MSCs is highlighted. Together, these aspects contribute in answering whether endochondral bone regeneration can be a logical approach to restore craniomaxillofacial bone defects.

Heterogeneous Human Periodontal Ligament-Committed Progenitor and Stem Cell Populations Exhibit a Unique Cementogenic Property Under In Vitro and In Vivo Conditions

An undesirable complication that arises during dental treatments is external apical-root resorption, which causes root-cementum and root-dentin loss. To induce de novo cementogenesis, stem cell therapy is required. Cementum-forming cells (cementoblasts) are known to be differentiated from periodontal-lineage mesenchymal stem cells (MSCs), which are derived from the dental follicle (DF) in developing tissues and the periodontal ligament (PDL) in adult tissues, but the periodontal-lineage MSC type that is optimal for inducing de novo cementogenesis remains unidentified, as does the method to isolate these cells from harvested tissues. Thus, we investigated the cementogenic potential of DF- and PDL-derived MSCs that were isolated by using two widely used cell-isolation methods: enzymatic digestion and outgrowth (OG) methods. DF- and PDL-derived cells isolated by using both methods proliferated actively, and all four isolated cell types showed MSC gene/protein expression phenotype and ability to differentiate into adipogenic and chondrogenic lineages. Furthermore, cementogenic-potential analysis revealed that all cell types produced alizarin red S-positive mineralized materials in in vitro cultures. However, PDL-OG cells presented unique cementogenic features, such as nodular formation of mineralized deposits displaying a cellular intrinsic fiber cementum-like structure, as well as a higher expression of cementoblast-specific genes than in the other cell types. Moreover, in in vivo transplantation experiments, PDL-OG cells formed cellular cementum-like hard tissue containing embedded osteocalcin-positive cells, whereas the other cells formed acellular cementum-like materials. Given that the root-cementum defect is likely regenerated through cellular cementum deposition, PDL-OG cell-based therapies might potentially facilitate the de novo cellular cementogenesis required for regenerating the root defect.

Practical methods for handling human periodontal ligament stem cells in serum-free and serum-containing culture conditions under hypoxia: implications for regenerative medicine

Stem cell-based therapies depend on the reliable expansion of patient-derived mesenchymal stem cells (MSCs) in vitro. The supplementation of cell culture media with serum is associated with several risks; accordingly, serum-free media are commercially available for cell culture. Furthermore, hypoxia is known to accelerate the expansion of MSCs. The present study aimed to characterize the properties of periodontal ligament-derived MSCs (PDLSCs) cultivated in serum-free and serum-containing media, under hypoxic and normoxic conditions. Cell growth, gene and protein expression, cytodifferentiation potential, genomic stability, cytotoxic response, and in vivo hard tissue generation of PDLSCs were examined. Our findings indicated that cultivation in serum-free medium does not affect the MSC phenotype or chromosomal stability of PDLSCs. PDLSCs expanded in serum-free medium exhibited more active growth than in fetal bovine serum-containing medium. We found that hypoxia does not alter the cell growth of PDLSCs under serum-free conditions, but inhibits their osteogenic and adipogenic cytodifferentiation while enabling maintenance of their multidifferentiation potential regardless of the presence of serum. PDLSCs expanded in serum-free medium were found to retain common MSC characteristics, including the capacity for hard tissue formation in vivo. However, PDLSCs cultured in serum-free culture conditions were more susceptible to damage following exposure to extrinsic cytotoxic stimuli than those cultured in medium supplemented with serum, suggesting that serum-free culture conditions do not exert protective effects against cytotoxicity on PDLSC cultures. The present work provides a comparative evaluation of cell culture in serum-free and serum-containing media, under hypoxic and normoxic conditions, for applications in regenerative medicine.

Original article. Human dental pulp stem cells as a potential feeder layer for human embryonic stem cell culture

Background: Human embryonic stem (hES) cells are pluripotent, and can differentiate into three germ layers. Traditionally, cultures of hES cells are maintained in a system containing mouse embryonic fibroblasts as a feeder layer for support of undifferentiated growth. However, contamination by animal cells limits the use of hES cells.

Objective: We evaluated the use of human dental pulp stem cells (hDPSCs) as a feeder layer for hES cell culture. It should be possible to obtain a new source of human mesenchymal stem cells for feeder cells to maintain undifferentiated growth of hES cells.

Methods: hDPSCs from removed impacted wisdom teeth (third molars) were extracted, cultured, and characterized for mesenchymal stem cell properties. Furthermore, hDPSCs were used as a feeder layer for culturing Chula2 and Chula5 hES cell lines. Finally, hES cell lines grown on hDPSCs feeders were examined embryonic stem cell properties.

Results: We found that hDPSCs, which have mesenchymal properties, can support undifferentiated growth of hES cell lines. After prolonged culture (passage 17), these hES cell lines still maintain ES cell properties including typical morphology seen in hES cells, the expression of pluripotency markers (Oct4, Sox2, Nanog, Rex1, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81), embryoid body formation and retention of a normal karyotype.

Conclusion: hDPSCs, derived from the pulp tissue of impacted third molars, are a potential source of human feeder cells for the culture of undifferentiated hES cells.

Comparison of periodontal ligament and gingiva-derived mesenchymal stem cells for regenerative therapies

OBJECTIVES

Tissue-engineering therapies using undifferentiated mesenchymal cells (MSCs) from intra-oral origin have been tested in experimental animals. This experimental study compared the characteristics of undifferentiated mesenchymal stem cells from either periodontal ligament or gingival origin, aiming to establish the basis for the future use of these cells on regenerative therapies.

MATERIALS AND METHODS

Gingiva-derived mesenchymal stem cells (GMSCs) were obtained from de-epithelialized gingival biopsies, enzymatically digested and expanded in conditions of exponential growth. Their growth characteristics, phenotype, and differentiation ability were compared with those of periodontal ligament-derived mesenchymal stem cells (PDLMSCs).

RESULTS

Both periodontal ligament- and gingiva-derived cells displayed a MSC-like phenotype and were able to differentiate into osteoblasts, chondroblasts, and adipocytes. These cells were genetically stable following in vitro expansion and did not generate tumors when implanted in immunocompromised mice. Furthermore, under suboptimal growth conditions, GMSCs proliferated with higher rates than PDLMSCs.

CONCLUSIONS

Stem cells derived from gingival biopsies represent bona fide MSCs and have demonstrated genetic stability and lack of tumorigenicity.

CLINICAL RELEVANCE

Gingiva-derived MSCs may represent an accessible source of messenchymal stem cells to be used in future periodontal regenerative therapies.

In vitro comparative analysis of human dental stem cells from a single donor and its neuronal differentiation potential evaluated by electrophysiology

AIMS

The aim of this study was to find out a mesenchymal stem cells (MSCs) source from human dental tissues of the same donor (follicle, papilla and pulp), which exhibits higher neurogenic differentiation potential in vitro.

MAIN METHODS

MSCs were isolated from dental tissues (follicle, papilla and pulp) by digestion method. All MSCs were analyzed for pluripotent makers by western blot, cell surface markers by flow cytometry, adipo- and osteocytes markers by RT-qPCR. The neuronal differentiated MSCs were characterized for neuronal specific markers by RT-qPCR and immunofluorescence. Functional neuronal properties were analyzed by electrophysiology and synaptic markers expression.

KEY FINDINGS

All MSCs expressed pluripotent markers (Oct4, Sox2 and Nanog) and were found positive for mesenymal markers (CD44, CD90, CD105) while negative for hematopoietic markers (CD34 and CD45). Furthermore, MSCs were successfully differentiated into adipocytes, osteocytes and trans-differentiated into neuronal cells. Among them, dental pulp derived MSCs exhibits higher neurogenic differentiation potential, in term of expression of neuronal specific markers at both gene and protein level, and having higher Na(+) and K(+) current with the expression of synaptic markers.

SIGNIFICANCE

The three types of dental MSCs from a single donor broadly possessed similar cellular properties and can differentiate into neuronal cells; however, pulp derived MSCs showed higher neurogenic potential than the follicle and papilla, suggesting their use in future stem cells therapy for the treatment of neurodegenerative disorders.

An Overview of Protocols for the Neural Induction of Dental and Oral Stem Cells In Vitro

To date, various adult stem cells have been identified within the oral cavity, including dental pulp stem cells, dental follicle stem cells, stem cells from apical papilla, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, and mesenchymal stem cells from the gingiva. All of these possess neurogenic potential due to their common developmental origin from the embryonic neural crest. Besides the relative ease of isolation of these adult stem cells from readily available biological waste routinely produced during dental treatment, these cells also possess the advantage of immune compatibility in autologous transplantation. In recent years, much interest has been focused on the derivation of neural lineages from these adult stem cells for therapeutic applications in the brain, spinal cord, and peripheral nerve regeneration. In addition, there are also promising nontherapeutic applications of stem cell-derived neurons in pharmacological and toxicological screening of neuroactive drugs, and for in vitro modeling of neurodevelopmental and neurodegenerative diseases. Hence, this review will critically examine the diverse array of in vitro neural induction protocols that have been devised for dental and oral-derived stem cells. These protocols are defined not only by the culture milieu comprising the basal medium plus growth factors, small molecules, and other culture supplements but also by the substrata/surface coatings utilized, the presence of multiple culture stages, the total culture duration, the initial seeding density, and whether the spheroid/neurosphere formation is being utilized to recapitulate the three-dimensional neural differentiation microenvironment that is naturally present physiologically in vivo.

Regenerative Applications Using Tooth Derived Stem Cells in Other Than Tooth Regeneration: A Literature Review

Tooth derived stem cells or dental stem cells are categorized according to the location from which they are isolated and represent a promising source of cells for regenerative medicine. Originally, as one kind of mesenchymal stem cells, they are considered an alternative of bone marrow stromal cells. They share many commonalties but maintain differences. Considering their original function in development and the homeostasis of tooth structures, many applications of these cells in dentistry have aimed at tooth structure regeneration; however, the application in other than tooth structures has been attempted extensively. The availability from discarded or removed teeth can be an innate benefit as a source of autologous cells. Their origin from the neural crest results in exploitation of neurological and numerous other applications. This review briefly highlights current and future perspectives of the regenerative applications of tooth derived stem cells in areas beyond tooth regeneration.

Chromosomal Abnormalities in Embryonic and Somatic Stem Cells

The potential use of stem cells (SCs) for tissue engineering, regenerative medicine, disease modeling, toxicological studies, drug delivery, and as in vitro model for the study of basic developmental processes implies large-scale in vitro culture. Here, after a brief description of the main techniques used for karyotype analysis, we will give a detailed overview of the chromosome abnormalities described in pluripotent (embryonic and induced pluripotent SCs) and somatic SCs, and the possible causes of their origin during culture.

Mesenchymal stem cells-based therapy as a potential treatment in neurodegenerative disorders: is the escape from senescence an answer?

Aging is the most prominent risk factor contributing to the development of neurodegenerative disorders. In the United States, over 35 million of elderly people suffer from age-related diseases. Aging impairs the self-repair ability of neuronal cells, which undergo progressive deterioration. Once initiated, this process hampers the already limited regenerative power of the central nervous system, making the search for new therapeutic strategies particularly difficult in elderly affected patients. So far, mesenchymal stem cells have proven to be a viable option to ameliorate certain aspects of neurodegeneration, as they possess high proliferative rate and differentiate in vitro into multiple lineages. However, accumulating data have demonstrated that during long-term culture, mesenchymal stem cells undergo spontaneous transformation. Transformed mesenchymal stem cells show typical features of senescence, including the progressive shortening of telomers, which results in cell loss and, as a consequence, hampered regenerative potential. These evidences, in line with those observed in mesenchymal stem cells isolated from old donors, suggest that senescence may represent a limit to mesenchymal stem cells exploitation in therapy, prompting scholars to either find alternative sources of pluripotent cells or to arrest the age-related transformation. In the present review, we summarize findings from recent literature, and critically discuss some of the major hurdles encountered in the search of appropriate sources of mesenchymal stem cells, as well as benefits arising from their use in neurodegenerative diseases. Finally, we provide some insights that may aid in the development of strategies to arrest or, at least, delay the aging of mesenchymal stem cells to improve their therapeutic potential.

Isolation, expansion and differentiation of cellular progenitors obtained from dental pulp of agouti (Dasyprocta prymnolopha Wagler, 1831)

Abstract: The study aimed to isolate, expand, differentiate and characterize progenitor cells existent in the dental pulp of agouti. The material was washed with PBS solution and dissociated mechanically with the aid of a scalpel blade on plates containing culture medium D-MEM/F-12, and incubated at 5% CO2-37⁰C. The growth curve, CFU assay, osteogenic/adipogenic differentiation and characterization were obtained from the isolation. The cells began to be released from the explant tissue around the 7th day of culture. By day 22 of culture, cells reached 80% confluence. At the UFC test, 81 colonies were counted with 12 days of cultivation. The growth curves before and after freezing showed a regular growth with intense proliferation and clonogenic potential. The cell differentiation showed formation of osteoblasts and fat in culture, starting at 15 days of culture in a specific medium. Flow cytometry (FACs) was as follows: CD34 (positive), CD14 (negative), CD45 (negative), CD73 (positive), CD79 (negative), CD90 (positive), CD105 (positive), demonstrating high specificity and commitment of isolated cells with mesenchymal stem cells strains. These results suggest the existence of a cell population of stem cells with mesenchymal features from the isolated tissue in the explants of agouti dental pulp, a potential model for study of stem cell strains obtained from the pulp tissue.

Tooth-derived stem cells: Update and perspectives

Tissue engineering is an emerging field of science that focuses on creating suitable conditions for the regeneration of tissues. The basic components for tissue engineering involve an interactive triad of scaffolds, signaling molecules, and cells. In this context, stem cells (SCs) present the characteristics of self-renewal and differentiation capacity, which make them promising candidates for tissue engineering. Although they present some common markers, such as cluster of differentiation (CD)105, CD146 and STRO-1, SCs derived from various tissues have different patterns in relation to proliferation, clonogenicity, and differentiation abilities in vitro and in vivo. Tooth-derived tissues have been proposed as an accessible source to obtain SCs with limited morbidity, and various tooth-derived SCs (TDSCs) have been isolated and characterized, such as dental pulp SCs, SCs from human exfoliated deciduous teeth, periodontal ligament SCs, dental follicle progenitor cells, SCs from apical papilla, and periodontal ligament of deciduous teeth SCs. However, heterogeneity among these populations has been observed, and the best method to select the most appropriate TDSCs for regeneration approaches has not yet been established. The objective of this review is to outline the current knowledge concerning the various types of TDSCs, and discuss the perspectives for their use in regenerative approaches.

Stem cell treatment of degenerative eye disease

Stem cell therapies are being explored extensively as treatments for degenerative eye disease, either for replacing lost neurons, restoring neural circuits or, based on more recent evidence, as paracrine-mediated therapies in which stem cell-derived trophic factors protect compromised endogenous retinal neurons from death and induce the growth of new connections. Retinal progenitor phenotypes induced from embryonic stem cells/induced pluripotent stem cells (ESCs/iPSCs) and endogenous retinal stem cells may replace lost photoreceptors and retinal pigment epithelial (RPE) cells and restore vision in the diseased eye, whereas treatment of injured retinal ganglion cells (RGCs) has so far been reliant on mesenchymal stem cells (MSC). Here, we review the properties of non-retinal-derived adult stem cells, in particular neural stem cells (NSCs), MSC derived from bone marrow (BMSC), adipose tissues (ADSC) and dental pulp (DPSC), together with ESC/iPSC and discuss and compare their potential advantages as therapies designed to provide trophic support, repair and replacement of retinal neurons, RPE and glia in degenerative retinal diseases. We conclude that ESCs/iPSCs have the potential to replace lost retinal cells, whereas MSC may be a useful source of paracrine factors that protect RGC and stimulate regeneration of their axons in the optic nerve in degenerate eye disease. NSC may have potential as both a source of replacement cells and also as mediators of paracrine treatment.

The difference on the osteogenic differentiation between periodontal ligament stem cells and bone marrow mesenchymal stem cells under inflammatory microenviroments

Periodontitis is a major cause of tooth loss in adults and periodontal ligament stem cells (PDLSCs) is the most favorable candidate for the reconstruction of tissues destroyed by periodontal diseases. However, pathological alterations caused by inflammatory insults might impact the regenerative capacities of these cells. Bone-marrow-derived human mesenchymal stem cells (hBMSCs) would accelerate alveolar bone regeneration by transplantation, compared to PDLSCs. Therefore, a better understanding of the osteogenic differentiation between PDLSCs and BMSCs in inflammatory microenviroments is therefore warranted. In this study, human PDLSCs were investigated for their stem cell characteristics via analysis of cell surface marker expression, colony forming unit efficiency, osteogenic differentiation and adipogenic differentiation, and compared to BMSCs. To determine the impact of both inflammation and the NF-κβ signal pathway on osteogenic differentiation, cells were challenged with TNF-α under osteogenic induction conditions and investigated for mineralization, alkaline phosphatase (ALP) activity, cell proliferation and relative genes expression. Results showed that PDLSCs exhibit weaker mineralization and ALP activity compared to BMSCs. TNF-α inhibited genes expression of osteogenic differentiation in PDLSCs, while, it stimulates gene expressions (BSP and Runx2) in BMSCs. Enhanced NF-κβ activity in PDLSCs decreases expression of Runx2 but it does not impede the osteogenic differentiation of BMSCs. Taken together, these results may suggest that the BMSCs owned the stronger immunomodulation in local microenvironment via anti-inflammatory functions, compared to PDLSCs.

Proteomics approaches for the studies of bone metabolism

Bone is an active tissue, in which bone formation by osteoblast is followed by bone resorption by osteoclasts, in a repeating cycle. Proteomics approaches may allow the detection of changes in cell signal transduction, and the regulatory mechanism of cell differentiation. LC-MS/MS-based quantitative methods can be used with labeling strategies, such as SILAC, iTRAQ, TMT and enzymatic labeling. When used in combination with specific protein enrichment strategies, quantitative proteomics methods can identify various signaling molecules and modulators, and their interacting proteins in bone metabolism, to elucidate biological functions for the newly identified proteins in the cellular context. In this article, we will briefly review recent major advances in the application of proteomics for bone biology, especially from the aspect of cellular signaling. [BMB Reports 2014; 47(3): 141-148]

Differential expression of basal microRNAs' patterns in human dental pulp stem cells

MicroRNAs (miRNAs) are small non-coding RNAs that regulate translation of mRNA into protein and play a crucial role for almost all biological activities. However, the identification of miRNAs from mesenchymal stem cells (MSCs), especially from dental pulp, is poorly understood. In this study, dental pulp stem cells (DPSCs) were characterized in terms of their proliferation and differentiation capacity. Furthermore, 104 known mature miRNAs were profiled by using real-time PCR. Notably, we observed 19 up-regulated miRNAs and 29 significantly down-regulated miRNAs in DPSCs in comparison with bone marrow MSCs (BM-MSCs). The 19 up-regulated miRNAs were subjected to ingenuity analysis, which were composed into 25 functional networks. We have chosen top 2 functional networks, which comprised 10 miRNA (hsa-miR-516a-3p, hsa-miR-125b-1-3p, hsa-miR-221-5p, hsa-miR-7, hsa-miR-584-5p, hsa-miR-190a, hsa-miR-106a-5p, hsa-mir-376a-5p, hsa-mir-377-5p and hsa-let-7f-2-3p). Prediction of target mRNAs and associated biological pathways regulated by each of this miRNA was carried out. We paid special attention to hsa-miR-516a-3p and hsa-miR-7-5p as these miRNAs were highly expressed upon validation with qRT-PCR analysis. We further proceeded with loss-of-function analysis with these miRNAs and we observed that hsa-miR-516a-3p knockdown induced a significant increase in the expression of WNT5A. Likewise, the knockdown of hsa-miR-7-5p increased the expression of EGFR. Nevertheless, further validation revealed the role of WNT5A as an indirect target of hsa-miR-516a-3p. These results provide new insights into the dynamic role of miRNA expression in DPSCs. In conclusion, using miRNA signatures in human as a prediction tool will enable us to elucidate the biological processes occurring in DPSCs.

Morphology and morphometry of feline bone marrow-derived mesenchymal stem cells in culture

Mesenchymal stem cells (MSC) are increasingly being proposed as a therapeutic option for treatment of a variety of different diseases in human and veterinary medicine. Stem cells have been isolated from feline bone marrow, however, very few data exist about the morphology of these cells and no data were found about the morphometry of feline bone marrow-derived MSCs (BM-MSCs). The objectives of this study were the isolation, growth evaluation, differentiation potential and characterization of feline BM-MSCs by their morphological and morphometric characteristics. in vitro differentiation assays were conducted to confirm the multipotency of feline MSC, as assessed by their ability to differentiate into three cell lineages (osteoblasts, chondrocytes, and adipocytes). To evaluate morphological and morphometric characteristics the cells are maintained in culture. Cells were observed with light microscope, with association of dyes, and they were measured at 24, 48, 72 and 120h of culture (P1 and P3). The non-parametric ANOVA test for independent samples was performed and the means were compared by Tukey's test. On average, the number of mononuclear cells obtained was 12.29 (±6.05x10(6)) cells/mL of bone marrow. Morphologically, BM-MSCs were long and fusiforms, and squamous with abundant cytoplasm. In the morphometric study of the cells, it was observed a significant increase in average length of cells during the first passage. The cell lengths were 106.97±38.16µm and 177.91±71.61µm, respectively, at first and third passages (24 h). The cell widths were 30.79±16.75 µm and 40.18±20.46µm, respectively, at first and third passages (24 h).The nucleus length of the feline BM-MSCs at P1 increased from 16.28µm (24h) to 21.29µm (120h). However, at P3, the nucleus length was 26.35µm (24h) and 25.22µm (120h). This information could be important for future application and use of feline BM-MSCs.

Influence of the mechanical environment on the engineering of mineralised tissues using human dental pulp stem cells and silk fibroin scaffolds

Teeth constitute a promising source of stem cells that can be used for tissue engineering and regenerative medicine purposes. Bone loss in the craniofacial complex due to pathological conditions and severe injuries could be treated with new materials combined with human dental pulp stem cells (hDPSCs) that have the same embryonic origin as craniofacial bones. Optimising combinations of scaffolds, cells, growth factors and culture conditions still remains a great challenge. In the present study, we evaluate the mineralisation potential of hDPSCs seeded on porous silk fibroin scaffolds in a mechanically dynamic environment provided by spinner flask bioreactors. Cell-seeded scaffolds were cultured in either standard or osteogenic media in both static and dynamic conditions for 47 days. Histological analysis and micro-computed tomography of the samples showed low levels of mineralisation when samples were cultured in static conditions (0.16±0.1 BV/TV%), while their culture in a dynamic environment with osteogenic medium and weekly µCT scans (4.9±1.6 BV/TV%) significantly increased the formation of homogeneously mineralised structures, which was also confirmed by the elevated calcium levels (4.5±1.0 vs. 8.8±1.7 mg/mL). Molecular analysis of the samples showed that the expression of tooth correlated genes such as Dentin Sialophosphoprotein and Nestin were downregulated by a factor of 6.7 and 7.4, respectively, in hDPSCs when cultured in presence of osteogenic medium. This finding indicates that hDPSCs are able to adopt a non-dental identity by changing the culture conditions only. Also an increased expression of Osteocalcin (1.4x) and Collagen type I (1.7x) was found after culture under mechanically dynamic conditions in control medium. In conclusion, the combination of hDPSCs and silk scaffolds cultured under mechanical loading in spinner flask bioreactors could offer a novel and promising approach for bone tissue engineering where appropriate and rapid bone regeneration in mechanically loaded tissues is required.

Co-culture with periodontal ligament stem cells enhances osteogenic gene expression in de-differentiated fat cells

In recent decades, de-differentiated fat cells (DFAT cells) have emerged in regenerative medicine because of their trans-differentiation capability and the fact that their characteristics are similar to bone marrow mesenchymal stem cells. Even so, there is no evidence to support the osteogenic induction using DFAT cells in periodontal regeneration and also the co-culture system. Consequently, this study sought to evaluate the DFAT cells co-culture with periodontal ligament stem cells (PDLSCs) in vitro in terms of gene expression by comparing runt-related transcription factor 2 (RUNX2) and Peroxisome proliferator-activated receptor gamma 2 (PPARγ2) genes. We isolated DFAT cells from mature adipocytes and compared proliferation with PDLSCs. After co-culture with PDLSCs, we analyzed transcriptional activity implying by DNA methylation in all adipogenic gene promoters using combined bisulfite restriction analysis. We compared gene expression in RUNX2 gene with the PPARγ2 gene using quantitative RT-PCR. After being sub-cultured, DFAT cells demonstrated morphology similar to fibroblast-like cells. At the same time, PDLSCs established all stem cell characteristics. Interestingly, the co-culture system attenuated proliferation while enhancing osteogenic gene expression in RUNX2 gene. Using the co-culture system, DFAT cells could trans-differentiate into osteogenic lineage enhancing, but conversely, their adipogenic characteristic diminished. Therefore, DFAT cells and the co-culture system might be a novel cell-based therapy for promoting osteogenic differentiation in periodontal regeneration.

Mesenchymal stem/progenitor cell isolation from tooth extraction sockets

Bone marrow-derived mesenchymal stem/progenitor cells (BMSCs) are commonly used in regeneration therapy. The current primary source of BMSCs is the iliac crest; however, the procedure is associated with various burdens on the patient, including the risk of pain and infection. Hence, the possibility to collect BMSCs from other, more accessible, sources would be an attractive approach. It is well known that stem cells migrate from surrounding tissues and play important roles in wound healing. We thus hypothesized that stem/progenitor cells could be isolated from granulation tissue in the dental socket, and we subsequently collected granulation tissue from dog dental socket 3 d after tooth extraction. After enzyme digestion of the collected tissue, the cells forming colonies constituted the dental socket-derived stem/progenitor cells (dDSCs). Next, dDSCs were compared with dog BMSCs (dBMSCs) for phenotype characterization. A flow cytometric analysis showed that dDSCs were positive for CD44, CD90, and CD271 but negative for CD34 and CD45, similar to dBMSCs. dDSCs also exhibited osteogenic, adipogenic, and chondrogenic differentiation ability, similar to dBMSCs, with a higher capacity for colony formation, proliferation, and motility than dBMSCs. In addition, an in vivo ectopic bone formation assay showed that dDSCs and dBMSCs both induced hard tissue formation, although only dDSCs formed a fibrous tissue-like structure connected to the newly formed bone. Finally, we tested the ability of dDSCs to regenerate periodontal tissue in a one-wall defect model. The defects in the dDSC-transplanted group (β-TCP/PGA/dDSCs) were regenerated with cementum-like and periodontal ligament-like tissues and alveolar bone, whereas only bony tissue was observed in the control group (β-TCP/PGA). In conclusion, we identified and characterized a population of stem/progenitor cells in granulation tissue obtained from the dental socket that exhibited several characteristics similar to those of BMSCs. Dental sockets could therefore be a novel source for isolating stem/progenitor cells from bone.

3D porous chitosan scaffolds suit survival and neural differentiation of dental pulp stem cells

A key aspect of cell replacement therapy in brain injury treatment is construction of a suitable biomaterial scaffold that can effectively carry and transport the therapeutic cells to the target area. In the present study, we created small 3D porous chitosan scaffolds through freeze-drying, and showed that these can support and enhance the differentiation of dental pulp stem cells (DPSCs) to nerve cells in vitro. The DPSCs were collected from the dental pulp of adult human third molars. At a swelling rate of ~84.33 ± 10.92 %, the scaffold displayed high porosity and interconnectivity of pores, as revealed by SEM. Cell counting kit-8 assay established the biocompatibility of the chitosan scaffold, supporting the growth and survival of DPSCs. The successful neural differentiation of DPSCs was assayed by RT-PCR, western blotting, and immunofluorescence. We found that the scaffold-attached DPSCs showed high expression of Nestin that decreased sharply following induction of differentiation. Exposure to the differentiation media also increased the expression of neural molecular markers Microtubule-associated protein 2, glial fibrillary acidic protein, and 2',3'-cyclic nucleotide phosphodiesterase. This study demonstrates that the granular 3D chitosan scaffolds are non-cytotoxic, biocompatible, and provide a conducive and favorable micro-environment for attachment, survival, and neural differentiation of DPSCs. These scaffolds have enormous potential to facilitate future advances in treatment of brain injury.

Periodontal ligament stem cells regulate B lymphocyte function via programmed cell death protein 1

Periodontal ligament stem cells (PDLSCs) have provided novel cell sources for tooth and periodontal tissue regeneration. Allogeneic PDLSCs can reconstruct periodontal ligament tissue that has been damaged by periodontal diseases and regulate T-cell immunity. However, the effect of PDLSCs on B cells remains unknown. Here, we treated periodontitis in a miniature pig model using allogeneic PDLSCs and showed a reduction in humoral immunity in the animals. When cocultured with normal B cells, human PDLSCs (hPDLSCs) had similar effects as bone marrow mesenchymal stem cells in suppressing B cell proliferation, differentiation, and migration, while intriguingly, hPDLSCs increased B cell viability by secreting interleukin-6. Mechanistically, hPDLSCs suppressed B cell activation through cell-to-cell contact mostly mediated by programmed cell death protein 1 and programmed cell death 1 ligand 1. Our data revealed a previously unrecognized function of PDLSCs in regulating humoral immune responses, which may represent a novel therapeutic strategy for immune-related disorders.

Age-dependent impaired neurogenic differentiation capacity of dental stem cell is associated with Wnt/β-catenin signaling

Two kinds of dental stem cells (DSCs), dental pulp stem cells (DPSCs) and stem cells from human-exfoliated deciduous teeth (SHED), have been identified as novel populations of mesenchymal stem cells that can be induced to differentiate into osteoblasts, chondrocytes, adipocytes, and neuron-like cells in vitro. As we know, both of them originate from the neural crest, but have distinct characteristics and functions in vitro and in vivo. The regeneration potential of DSCs declines with advanced age; however, the mechanism of the impaired potential in DSCs has not been fully explored. In this study, we investigated whether declined neurogenic differentiation capacity is associated with an altered expression of Wnt signaling-related proteins in vitro. We compared stem cells isolated from human dental pulp in two age groups: the exfoliated deciduous teeth (5-12 years), and the third permanent teeth (45-50 years). We found that the expression levels of neuron markers, such as βIII-tubulin, microtubule-associated protein 2(MAP2), tyrosine hydroxylase (TH), and Nestin were lower in the DPSCs group compared with that in the SHED group; however, in supplementation with human recombinant Wnt1 in the medium, the DPSCs were prone to neural differentiation and expressed higher levels of neurogenic markers. In summary, our study demonstrated that Wnt/β-catenin signaling may play a vital role in the age-dependent neural differentiation of DSCs. Therefore, DSCs may provide an ideal source of stem cells that can further extend their therapeutic application in nerve injury and neurodegenerative diseases.

Multilineage potential and proteomic profiling of human dental stem cells derived from a single donor

Dental tissues provide an alternative autologous source of mesenchymal stem cells (MSCs) for regenerative medicine. In this study, we isolated human dental MSCs of follicle, pulp and papilla tissue from a single donor tooth after impacted third molar extraction by excluding the individual differences. We then compared the morphology, proliferation rate, expression of MSC-specific and pluripotency markers, and in vitro differentiation ability into osteoblasts, adipocytes, chondrocytes and functional hepatocyte-like cells (HLCs). Finally, we analyzed the protein expression profiles of undifferentiated dental MSCs using 2DE coupled with MALDI-TOF-MS. Three types of dental MSCs largely shared similar morphology, proliferation potential, expression of surface markers and pluripotent transcription factors, and differentiation ability into osteoblasts, adipocytes, and chondrocytes. Upon hepatogenic induction, all MSCs were transdifferentiated into functional HLCs, and acquired hepatocyte functions by showing their ability for glycogen storage and urea production. Based on the proteome profiling results, we identified nineteen proteins either found commonly or differentially expressed among the three types of dental MSCs. In conclusion, three kinds of dental MSCs from a single donor tooth possessed largely similar cellular properties and multilineage potential. Further, these dental MSCs had similar proteomic profiles, suggesting their interchangeable applications for basic research and call therapy.

Human dental mesenchymal stem cells and neural regeneration

Nerve tissue presents inherent difficulties for its effective regeneration. Stem cell transplantation is considered an auspicious treatment for neuronal injuries. Recently, human dental mesenchymal stem cells (DMSCs) have received extensive attention in the field of regenerative medicine due to their accessibility and multipotency. Since their origin is within the neural crest, they can be differentiated into neural crest-derived cells including neuron and glia cells both in vitro and in vivo. DMSCs are also able to secrete a wide variety of neurotrophins and chemokines, which promote neuronal cells to survival and differentiation. Experimental evidence has shown that human DMSCs engraftment recovered neuronal tissue damage in animal models of central nervous system injuries. Human DMSCs can be a new hope for treatment of nervous system diseases and deficits such as spinal cord injury, stroke and Parkinson's disease.

Isolation and characterization of epithelial and myogenic cells by "fishing" for the morphologically distinct cell types in rat primary periodontal ligament cultures

The periodontal ligament (PDL) contains various cell populations and plays a central role in the maintenance, repair, and regeneration of the periodontium, i.e., tooth-supporting structures. Because primary cells isolated from PDL tissue are heterogeneous, the establishment of an effective isolation method for cells of interest is desired. In the present study, two morphologically distinct cell types were identified in confluent primary cultures derived from rat PDL. To isolate these cell populations, a small piece of filter paper soaked with trypsin-EDTA was placed directly onto the target cell population, enabling the cells to detach from the culture dish. The filter papers were then transferred into fresh culture dishes to establish outgrowth cultures; these two steps constitute the "cell fishing" method. The "fished" cell types were propagated and subcultured for further analyses. In morphological evaluation, immunocytochemical analyses, and reverse transcription-polymerase chain reaction, the isolated cells exhibited a polygonal appearance or a mono- or multinucleated appearance, with a high cytoplasm-to-nucleus ratio, leading to their being characterized as epithelial or myogenic cell populations, respectively. Surprisingly, a notable proportion of the multinuclear cells in the primary and subsequent isolated cultures demonstrated dramatic, spontaneous contractions, a feature typical of skeletal muscle cells. Finally, the isolated cell populations maintained a normal karyotype with a diploid chromosomal number. These results demonstrated that physiological epithelial and skeletal muscle cells can be obtained from primary PDL cultures without artificial induction using growth factors or chemicals, and can be propagated as individual lineage-committed cell populations; the populations consisted of differentiated and progenitor cells that maintained chromosomal stability. This simple, classical culture procedure provides new insights into the biological properties of PDL cells, which are potentially important for the differentiation of tissue or somatic stem cells and for the development of future cell-based therapies for dental and muscular diseases.