Adult stem cell therapy: Dream or reality?

Comparative cell viability of dentin-bonding adhesive systems on human dental pulp stem cells: time-dependent analysis

BACKGROUND

Restorative materials are in prolonged contact with living tissues such as oral mucosa, dentin, pulp, periodontal, and periapical tissues. Therefore, the potentially harmful effects of these materials and their components on oral tissues should be evaluated before clinical use. This study aimed to compare the cell viability of different adhesive systems (ASs) on human dental pulp stem cells (hDPSCs).

METHODS

Three ASs that combining methacryloyloxydecyl dihydrogen phosphate (MDP) monomer with new hydrophilic amide monomers [Clearfil Universal Bond Quick(CUBQ), Kuraray Noritake], self-reinforcing 3D monomer [Bond Force II(BFII), Tokuyama)], and dual-cure property [Futurabond DC(FBDC), VOCO] were used. Three (n = 3) samples were prepared for each group. Dental pulp stem cells were isolated from ten patients' extracted third molar teeth. Samples were incubated in Dulbecco's modified Eagle's medium (DMEM) for 24 h (h), 72 h, and 7 days (d) to obtain extracts. For the control group, cells were cultured without DBA samples. Cell viability of ASs extracts was measured using a cell proliferation detection kit (WST-1, Roche). Statistical analysis was performed using two-way ANOVA and post-hoc (Duncan) tests (p < 0.05).

RESULTS

At 24 and 72 h statistically significant differences were determined between control and BFII, control and FBDC groups (p < 0.05), while no differences between control and CUBQ groups (p > 0.05). On the 7th d, statistically significant differences were found between the control and experimental groups (p < 0.05), while no differences between experimental groups (p > 0.05). A statistically significant difference was detected for the BFII group over the three-time interval (p < 0.05). The lowest cell viability was observed for the FBDC group at 24 h, and the difference was statistically significant when compared with 72 h and 7th d (p < 0.05).

CONCLUSION

All ASs showed different cell viability values at various exposure times. It should be taken into consideration that pH values, as well as the contents of ASs, have a significant effect on the cell viability.

Evaluation of the Consistency and Composition of Commercially Available Bone Marrow Aspirate Concentrate Systems

Background:

Bone marrow aspirate (BMA) concentrate (BMAC) has gained popularity as a treatment modality for various orthopaedic conditions; however, there are still inconsistencies in its reported therapeutic efficacy. This may be because of the many different commercial BMAC preparation systems used clinically, which generate dissimilar concentrate products.

Purpose:

To compare 3 commercially available BMAC preparation systems: Harvest SmartPrep 3, Biomet BioCUE, and Arthrex Angel. We evaluated the consistency of each of these systems and compared the composition of their concentrate products.

Study Design:

Controlled laboratory study.

Methods:

A total of 10 patients donated whole blood and BMA, which were combined and processed with the 3 different BMAC preparation systems. Samples were taken before and after processing for the measurement of white blood cells (WBC), platelets (PLT), CD34+ cells, and colony-forming unit–fibroblast (CFU-F). To evaluate consistency, the variances of cell yield and concentration increase from baseline for each cell type were compared between systems. To compare concentrate product composition, differences between the systems’ mean cell yield and concentration increase from baseline for each cell type were evaluated.

Results:

The Harvest system (variance, 0.25) concentrated WBC more consistently than the Arthrex system (variance, 3.25) (P = .024), but no other differences in consistency were noted between the 3 systems. The Harvest system recovered the greatest percentage of CFU-F (82.4% ± 18.2%), CD34+ cells (81.1% ± 28.5%), and WBC (77.3% ± 8.6%), whereas the Biomet system recovered the greatest percentage of PLTs (92.9% ± 27.3%). The Arthrex system concentrated PLT to the greatest degree (11.10 ± 2.05 times baseline), while the Biomet system concentrated WBC to the greatest degree (5.99 ± 1.04 times baseline).

Conclusion:

The consistency of the 3 systems was similar for all but 1 of the evaluated cell types. However, the composition of the concentrate products differed across systems. This may grant each system unique advantages without having to sacrifice reproducibility.

Clinical Relevance:

Understanding the consistency of different BMAC preparation systems and their product makeup may aid in determining optimal therapeutic doses of different cell types.

Safety and Biodistribution of Human Bone Marrow-Derived Mesenchymal Stromal Cells Injected Intrathecally in Non-Obese Diabetic Severe Combined Immunodeficiency Mice: Preclinical Study

Background

Mesenchymal stromal cells (MSCs) have potent immunomodulatory and neuroprotective properties, and have been tested in neurodegenerative diseases resulting in meaningful clinical improvements. Regulatory guidelines specify the need to perform preclinical studies prior any clinical trial, including biodistribution assays and tumourigenesis exclusion. We conducted a preclinical study of human bone marrow MSCs (hBM-MSCs) injected by intrathecal route in Non-Obese Diabetic Severe Combined Immunodeficiency mice, to explore cellular biodistribution and toxicity as a privileged administration method for cell therapy in Friedreich's Ataxia.

Methods

For this purpose, 3 × 10⁵ cells were injected by intrathecal route in 12 animals (experimental group) and the same volume of culture media in 6 animals (control group). Blood samples were collected at 24 h (n = 9) or 4 months (n = 9) to assess toxicity, and nine organs were harvested for histology and safety studies. Genomic DNA was isolated from all tissues, and mouse GAPDH and human β2M and β-actin genes were amplified by qPCR to analyze hBM-MSCs biodistribution.

Results

There were no deaths nor acute or chronic toxicity. Hematology, biochemistry and body weight were in the range of normal values in all groups. At 24 h hBM-MSCs were detected in 4/6 spinal cords and 1/6 hearts, and at 4 months in 3/6 hearts and 1/6 brains of transplanted mice. No tumours were found.

Conclusion

This study demonstrated that intrathecal injection of hBM-MSCs is safe, non toxic and do not produce tumors. These results provide further evidence that hBM-MSCs might be used in a clinical trial in patients with FRDA.

Peroxiredoxin 6 Inhibits Osteogenic Differentiation and Bone Formation Through Human Dental Pulp Stem Cells and Induces Delayed Bone Development

Aims: Peroxiredoxins (PRDXs) are thiol-specific antioxidant enzymes that regulate redox balance that are critical for maintaining the cellular potential for self-renewal and stemness. Stem cell-based regenerative medicine is a promising approach in tissue reconstruction. However, to obtain functional cells for use in clinical applications, stem cell technology still requires improvements. Results: In this study, we found that PRDX6 levels were decreased during osteogenic differentiation in human dental pulp stem cells (hDPSCs). hDPSCs stably expressing Myc-PRDX6 (hDPSC/myc-PRDX6) inhibited cell growth in hDPSCs during osteogenic differentiation and impaired osteogenic phenotypes such as alkaline phosphatase (ALP) activity, mineralized nodule formation, and osteogenic marker genes [ALP and osteocalcin (OCN)]. hDPSC cell lines stably expressing mutant glutathione peroxidase (PRDX6(C47S)) and independent phospholipase A2 (PRDX6(S32A)) were also generated. Each mutant form of PRDX6 abolished the impaired osteogenic phenotypes, the transforming growth factor-β-mediated Smad2 and p38 pathways, and RUNX2 expression. Furthermore, in vivo experiments revealed that hDPSC/myc-PRDX6 suppressed hDPSC-based bone regeneration in calvarial defect mice, and newborn PRDX6 transgenic mice exhibited delayed bone development and reduced RUNX2 expression. Innovation and Conclusion: These findings illuminate the effects of PRDX6 during osteogenic differentiation of hDPSCs, and also suggest that regulating PRDX6 may improve the clinical utility of stem cell-based regenerative medicine for the treatment of bone diseases. Antioxid. Redox Signal. 30, 1969-1982.

Comparative analysis of lncRNA and mRNA expression profiles between periodontal ligament stem cells and gingival mesenchymal stem cells

Oral tissue-derived mesenchymal stem cells, such as periodontal ligament stem cells (PDLSCs) and gingival mesenchymal stem cells (GMSCs), possess different biological characteristics, but the molecular mechanism remains unclear, which restricts their application in tissue engineering. Long noncoding RNAs (lncRNAs) are known to be significant regulators of gene expression, but our knowledge about their roles in the regulation of stem cell biological properties is still limited. This study compared the lncRNA and mRNA expression profiles between PDLSCs and GMSCs through microarray analysis, and applied bioinformatics methods to analyze and predict the function and connection of differentially expressed genes, aiming to screen potential key regulators of diverse biological characteristics in PDLSCs and GMSCs. Microarray analysis showed that 2162 lncRNAs and 1347 mRNAs were significantly differentially expressed between PDLSCs and GMSCs. Gene ontology (GO) analysis and pathway analysis indicated that these differentially expressed genes were involved in diverse biological processes and signaling pathways. The gene signal network and pathway relation network predicted some potentially important regulators. The coding-noncoding gene coexpression network (CNC network) revealed many potential lncRNA-mRNA connection pairs that participated in the regulation of biological behaviors. These results stressed the roles of lncRNAs in controlling stem cell biological behaviors and provided guides for molecular mechanistic study of different biological characteristics in PDLSCs and GMSCs.

Healing capacity of bone marrow mesenchymal stem cells versus platelet-rich fibrin in tibial bone defects of albino rats: an in vivo study

Background: Various techniques for tissue engineering have been introduced to aid the regeneration of defective or lost bone tissue. The aim of this study was to compare the in vivo bone-forming potential of bone marrow mesenchymal stem cells (BM-MSCs) and platelet-rich fibrin (PRF) on induced bone defects in rats' tibiae. Methods: In total, one defect of 3-mm diameter was created in each tibia of 36 Wistar male rats. There were two groups: group A, left tibia bone defects that received PRF; and group B, right tibia bone defects of the same animal that received BM-MSCs loaded on a chitosan scaffold. Subsequently, Scanning electron microscope/energy-dispersive X-ray (SEM/EDX) analyses was performed at 3 and 10 days, and 3 weeks post‑implantation and following euthanasia; (n=12). Results: The EDX analysis performed for each group and time point revealed a significant increase in the mean calcium and phosphorous weight percentage in the BM-MSC-treated group relative to the PRF-treated group at all-time intervals (P < 0.05). Moreover, the mean calcium and phosphorus weight percentage increased as time progressed since the surgical intervention in the PRF-treated and BM-MSCs groups (P < 0.05). Conclusions: In the present study, both BM-MSCs and PRF were capable of healing osseous defects induced in a rat tibial model. Yet, BM-MSCs promoted more adequate healing, with higher mean calcium and phosphorous weight percentages than PRF at all-time points, and showed greater integration into the surrounding tissues than PRF.

Preclinical Studies of the Biosafety and Efficacy of Human Bone Marrow Mesenchymal Stem Cells Pre-Seeded into β-TCP Scaffolds after Transplantation

Background: Cell-Based Therapies (CBT) constitute a valid procedure for increasing the quantity and quality of bone in areas with an inadequate bone volume. However, safety and efficacy should be investigated prior to clinical application. The objective of this study was to evaluate the biodistribution, safety and osteogenic capacity of bone marrow-derived human mesenchymal stem cells (hBMMSCs) pre-seeded into β-tricalcium phosphate (TCP) and implanted into NOD/SCID mice at subcutaneous and intramuscular sites. Methods: hBMMSCs were isolated, characterized and then cultured in vitro on a porous β-TCP scaffold. Cell viability and attachment were analyzed and then hBMMSCs seeded constructs were surgically placed at subcutaneous and intramuscular dorsal sites into NOD/SCID mice. Acute and subchronic toxicity, cell biodistribution and efficacy were investigated. Results: There were no deaths or adverse events in treated mice during the 48-hour observation period, and no toxic response was observed in mice. In the 12-week subchronic toxicity study, no mortalities, abnormal behavioral symptoms or clinical signs were observed in the saline control mice or the hBMMSCs/β-TCP groups. Finally, our results showed the bone-forming capacity of hBMMSCs/β-TCP since immunohistochemical expression of human osteocalcin was detected from week 7. Conclusions: These results show that transplantation of hBMMSCs/β-TCP in NOD/SCID mice are safe and effective, and might be applied to human bone diseases in future clinical trials.

Proteomic Analysis of Human Adipose Derived Stem Cells during Small Molecule Chemical Stimulated Pre-neuronal Differentiation

Background

Adipose derived stem cells (ADSCs) are acquired from abdominal liposuction yielding a thousand fold more stem cells per millilitre than those from bone marrow. A large research void exists as to whether ADSCs are capable of transdermal differentiation toward neuronal phenotypes. Previous studies have investigated the use of chemical cocktails with varying inconclusive results.

Methods

Human ADSCs were treated with a chemical stimulant, beta-mercaptoethanol, to direct them toward a neuronal-like lineage within 24 hours. Quantitative proteomics using iTRAQ was then performed to ascertain protein abundance differences between ADSCs, beta-mercaptoethanol treated ADSCs and a glioblastoma cell line.

Results

The soluble proteome of ADSCs differentiated for 12 hours and 24 hours was significantly different from basal ADSCs and control cells, expressing a number of remodeling, neuroprotective and neuroproliferative proteins. However toward the later time point presented stress and shock related proteins were observed to be up regulated with a large down regulation of structural proteins. Cytokine profiles support a large cellular remodeling shift as well indicating cellular distress.

Conclusion

The earlier time point indicates an initiation of differentiation. At the latter time point there is a vast loss of cell population during treatment. At 24 hours drastically decreased cytokine profiles and overexpression of stress proteins reveal that exposure to beta-mercaptoethanol beyond 24 hours may not be suitable for clinical application as our results indicate that the cells are in trauma whilst producing neuronal-like morphologies. The shorter treatment time is promising, indicating a reducing agent has fast acting potential to initiate neuronal differentiation of ADSCs.

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.

Synaptic plasticity and sensory-motor improvement following fibrin sealant dorsal root reimplantation and mononuclear cell therapy

Root lesions may affect both dorsal and ventral roots. However, due to the possibility of generating further inflammation and neuropathic pain, surgical procedures do not prioritize the repair of the afferent component. The loss of such sensorial input directly disturbs the spinal circuits thus affecting the functionality of the injuried limb. The present study evaluated the motor and sensory improvement following dorsal root reimplantation with fibrin sealant (FS) plus bone marrow mononuclear cells (MC) after dorsal rhizotomy. MC were used to enhance the repair process. We also analyzed changes in the glial response and synaptic circuits within the spinal cord. Female Lewis rats (6–8 weeks old) were divided in three groups: rhizotomy (RZ group), rhizotomy repaired with FS (RZ+FS group) and rhizotomy repaired with FS and MC (RZ+FS+MC group). The behavioral tests electronic von-Frey and Walking track test were carried out. For immunohistochemistry we used markers to detect different synapse profiles as well as glial reaction. The behavioral results showed a significant decrease in sensory and motor function after lesion. The reimplantation decreased glial reaction and improved synaptic plasticity of afferent inputs. Cell therapy further enhanced the rewiring process. In addition, both reimplanted groups presented twice as much motor control compared to the non-treated group. In conclusion, the reimplantation with FS and MC is efficient and may be considered an approach to improve sensory-motor recovery following dorsal rhizotomy.

Imperative role of dental pulp stem cells in regenerative therapies: a systematic review

Stem cells are primitive cells that can differentiate and regenerate organs in different parts of the body such as heart, bones, muscles and nervous system. This has been a field of great clinical interest with immense possibilities of using the stem cells in regeneration of human organ those are damaged due to disease, developmental defects and accident. The knowledge of stem cell technology is increasing quickly in all medical specialties and in dental field too. Stem cells of dental origin appears to hold the key to various cell-based therapies in regenerative medicine, but most avenues are in experimental stages and many procedures are undergoing standardization and validation. Long-term preservation of SHED cells or DPSC is becoming a popular consideration, similar to the banking of umbilical cord blood. Dental pulp stem cells (DPSCs) are the adult multipotent cells that reside in the cell rich zone of the dental pulp. The multipotent nature of these DPSCs may be utilized in both dental and medical applications. A systematic review of the literature was performed using various internet based search engines (PubMed, Medline Plus, Cochrane, Medknow, Ebsco, Science Direct, Hinari, WebMD, IndMed, Embase) using keywords like “dental pulp stem cells”, “regeneration”, “medical applications”, “tissue engineering”. DPSCs appears to be a promising innovation for the re-growth of tissues however, long term clinical studies need to be carried out that could establish some authentic guidelines in this perspective.

Hydrogen sulphide increases hepatic differentiation of human tooth pulp stem cells compared with human bone marrow stem cells

AIM

To determine the differences in stem cell properties, in hepatic differentiation and in the effects of hydrogen sulphide (H2 S) on hepatic differentiation between human bone marrow stem cells (hBMC) and stem cells from human exfoliated primary tooth pulp (SHED).

METHODOLOGY

CD117(+) cells were magnetically separated and subjected to hepatic differentiation. CD117(+) cell lineages were characterized for transcription factors indicative of stem cells by qRT-PCR. For the last 9 days of the differentiation, the test cells were exposed to 0.1 ng mL(-1) H2 S. Immunocytochemistry and flow cytometry of albumin, alpha-fetoprotein and carbamoyl phosphate synthetase were carried out after differentiation. Urea concentration and glycogen synthesis were also determined.

RESULTS

Genes expressed in SHED were also expressed in BMC. No difference in expression level of hepatic markers was shown by immunofluorescence. SHED showed more positive cells than hBMC (P < 0.01). H2 S increased the number of positive cells in both cultures (P < 0.01). Urea concentration and glycogen synthesis increased significantly after H2 S exposure (P < 0.001 and P < 0.05, respectively). Real-time PCR data were analysed by RT(2) profiler RT-PCR Array Data Analysis version 3.5 (Qiagen), and ELISA data were analysed by Bonferroni's multiple comparison using Windows spss version 16 (SPSS Inc, Chicago, IL, USA). Bonferroni's multiple comparison test was also carried out after angle transformation for the percentage data of flow cytometer using Windows spss(®) version 16 (SPSS Inc). Statistical significance was accepted at P < 0.05.

CONCLUSIONS

Stem cells from human exfoliated primary tooth pulp and BMC have similar properties. The level of hepatic differentiation in SHED compared with BMC was the same or higher. H2 S increased the level of hepatic differentiation.

Effects of bone marrow-derived mesenchymal stem cells and platelet-rich plasma on bone regeneration for osseointegration of dental implants: preliminary study in canine three-wall intrabony defects

Tissue engineering has been applied to overcome the obstacles encountered with bone regeneration for the placement of dental implants. The purpose of this study was to determine the bone formation ability of human bone marrow-derived mesenchymal stem cells (BMMSCs) and platelet-rich plasma (PRP) when applied separately or together to the intrabony defect around dental implants with a porous hydroxyapatite (HA) scaffold. Standardized three-wall intrabony defects (4 × 4 × 4 mm) were created at the mesial of each dental implant site in four mongrel dogs. Defects were then grafted with the following materials: HA + BMMSCs (HS group), HA + PRP (HP group), HA + BMMSCs + PRP (HSP group), and HA scaffold alone (HA group). The level of bone formation (bone density) and osseointegration (bone-to-implant contact [BIC]) in bone defects around the implants were evaluated by histological and histometric analysis at 6 and 12 weeks after the placement of implants. HA, HS, HP, and HSP groups generally showed an increase in bone density and BIC between 6 and 12 weeks, except BIC in the HS group. Although no statistically significant differences were found among HA, HS, HP, and HSP groups (p > 0.05), the highest level of bone density and BIC were observed in the HSP group after the 12-week healing period. Furthermore, the level of bone maturation was higher in the HSP group than in the other groups as determined histologically. The findings of this preliminary study suggest that BMMSCs and PRP combined with HA scaffold may provide additional therapeutic effects on bone regeneration and improve osseointegration in bone defects around dental implants.

Acute and chronic MRI changes in the spine and spinal cord after surgical stem cell grafting in patients with definite amyotrophic lateral sclerosis: post-infusion injuries are unrelated with clinical impairment

OBJECTIVE

To report MRI spinal changes after surgical infusion of bone marrow stem cells (BMSc) in ALS patients and assess their correlation with clinical events and functional performance.

METHODS

BMSc were surgically injected in the thoracic spinal cord of 11 ALS patients (6/5 male/female; median age 46years). We performed first-week and third, sixth, ninth and twelfth post-surgical months spinal MRIs. The spinal changes in the postsurgical week and follow-up MRIs, as well as clinical events, functional scales and respiratory and electromyography data, were longitudinally monitored. Correlations between the imaging and clinical data were evaluated with the Spearman's test.

RESULTS

Transient extradural fluid collections (100%), transient spinal cord T2 hyperintensity (81.8%), and chronic spinal cord deformities (63.6%) were the dominating MRI changes. Spinal cord hemorrhages (27.3%) and cystic myelomalacia (1/11 patients) were important although unusual findings. During the follow-up, minor adverse events of mild to moderate intensity eventually improved. Initial and follow-up imaging scores showed a strongly positive correlation (r 0.879, P<0.001). The initial and delayed clinical scores did not correlate. There was no significant correlation between any of the imaging scores and clinical data.

CONCLUSIONS

Infusion of BMSc produces a variety of spinal changes apparently unrelated with clinical events and disease worsening.

Neurotrophic bone marrow cellular nests prevent spinal motoneuron degeneration in amyotrophic lateral sclerosis patients: a pilot safety study

The objective of this article is to assess the safety of intraspinal infusion of autologous bone marrow mononuclear cells (BMNCs) and, ultimately, to look for histopathological signs of cellular neurotrophism in amyotrophic lateral sclerosis (ALS) patients. We conducted an open single arm phase I trial. After 6 months observation, autologous BMNCs were infused into the posterior spinal cord funiculus. Safety was the primary endpoint and was defined as the absence of serious transplant-related adverse events. In addition, forced vital capacity (FVC), ALS-functional rating scale (ALS-FRS), Medical Research Council scale for assessment of muscle power (MRC), and Norris scales were assessed 6 and 3 months prior to the transplant and quarterly afterward for 1 year. Pathological studies were performed in case of death. Eleven patients were included. We did not observe any severe transplant-related adverse event, but there were 43 nonsevere events. Twenty-two (51%) resolved in ≤2 weeks and only four were still present at the end of follow-up. All were common terminology criteria for adverse events grade ≤2. No acceleration in the rate of decline of FVC, ALS-FRS, Norris, or MRC scales was observed. Four patients died on days 359, 378, 808, and 1,058 post-transplant for reasons unrelated to the procedure. Spinal cord pathological analysis showed a greater number of motoneurons in the treated segments compared with the untreated segments (4.2 ± 0.8 motoneurons per section [mns per sect] and 0.9 ± 0.3 mns per sect, respectively). In the treated segments, motoneurons were surrounded by CD90+ cells and did not show degenerative ubiquitin deposits. This clinical trial confirms not only the safety of intraspinal infusion of autologous BMNC in ALS patients but also provides evidence strongly suggesting their neurotrophic activity.

Mesenchymal dental stem cells in regenerative dentistry

In the last decade, tissue engineering is a field that has been suffering an enormous expansion in the regenerative medicine and dentistry. The use of cells as mesenchymal dental stem cells of easy access for dentist and oral surgeon, immunosuppressive properties, high proliferation and capacity to differentiate into odontoblasts, cementoblasts, osteoblasts and other cells implicated in the teeth, suppose a good perspective of future in the clinical dentistry. However, is necessary advance in the known of growth factors and signalling molecules implicated in tooth development and regeneration of different structures of teeth. Furthermore, these cells need a fabulous scaffold that facility their integration, differentiation, matrix synthesis and promote multiple specific interactions between cells. In this review, we give a brief description of tooth development and anatomy, definition and classification of stem cells, with special attention of mesenchymal stem cells, commonly used in the cellular therapy for their trasdifferentiation ability, non ethical problems and acceptable results in preliminary clinical trials. In terms of tissue engineering, we provide an overview of different types of mesenchymal stem cells that have been isolated from teeth, including dental pulp stem cells (DPSCs), stem cells from human exfoliated deciduous teeth (SHEDs), periodontal ligament stem cells (PDLSCs), dental follicle progenitor stem cells (DFPCs), and stem cells from apical papilla (SCAPs), growth factors implicated in regeneration teeth and types of scaffolds for dental tissue regeneration.

Key words:Dental stem cells, regenerative dentistry, mesenchymal stem cells, tissue engineering, stem cells.

Hydrogen sulfide increases hepatic differentiation in tooth-pulp stem cells

The toxicity of hydrogen sulfide (H(2)S), an oral malodorous compound, is well reported. We have recently established an experimental model of hepatic differentiation from human tooth-pulp stem cells (HTPC) using serum-free medium. The objective of the present study is to determine the effect of H(2)S on hepatic differentiation. The CD117 positive cell fraction was obtained from deciduous HTPC using magnetic cell sorting. After 3-4 passages, cells were grown in Dulbecco's modified Eagle's medium supplemented with insulin-transferrin-selenium-x (ITS-x), embryotrophic factor (ETF) and hepatocyte growth factor (HGF) for hepatic commitment (five days). For hepatic differentiation the cells were cultured in Iscove's modified Dulbecco's medium supplemented with ITS-x, ETF, oncostatin, HGF and dexamethasone for 15 days in air containing 5% CO(2), with or without H(2)S at 0.05 ng ml(-1). Cells were assayed for the expression of hepatic markers α-fetoprotein, albumin or carbamoyl phosphate synthetase, and urea concentrations and glycogen synthesis were also determined. The panel of hepatic markers was expressed more in the test groups exposed to H(2)S than in the control groups. Urea and glycogen production were also increased, especially glycogen which was approximately five times greater compared to the control (p < 0.01). We concluded that H(2)S at physiological concentrations increased the ability of HTPC to undergo hepatogenic differentiation.

Mesenchymal stem cells derived from dental tissues

Regeneration of tissues occurs naturally due to the existence of stem cells with the capacity to self-regenerate and differentiate; however, regenerative capacity decreases with age, and in many cases, regeneration is not sufficient to repair the damage produced by degenerative, ischaemic, inflammatory, or tumour-based diseases. In the last decade, advances have been made in the understanding of stem cells, the genes that control the alternative fates of quiescence and differentiation, and the niches that provide specific signals that modulate cell fate decisions. Embryonic stem-cell research is shedding light on the secrets of development. Adult stem cells (AS cells) are available from several sources. Bone marrow and connective tissue have been used in preliminary clinical trials for regenerative therapy. Recently, several types of AS cells have been isolated from teeth, including dental pulp stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, dental follicle progenitor stem cells and stem cells from apical papilla. Preliminary data suggest that these cells have the capacity to differentiate into osteoblasts, adipocytes, chondrocytes and neural cells. If confirmed, these data would support the use of these cells, which are easily obtained from extracted teeth, in dental therapies, including in regenerative endodontics, providing a new therapeutic modality.

Microporation is a valuable transfection method for gene expression in human adipose tissue-derived stem cells

Stem cells are a promising resource for gene therapy. Adipose tissue-derived stem cells (ADSCs) offer advantages because of their abundance and ease of isolation. However, it is difficult to transduce genes into ADSCs by common transfection methods, especially nonviral methods. We report here the use of a new electroporation method, termed "microporation," to transduce plasmids into human ADSCs (hADSCs). We determined optimal conditions that led to efficient transfection of >76.1% of the microporated hADSCs with only minimal cell damage or cytotoxicity. We demonstrated the expression of both enhanced green fluorescent protein (EGFP) and luciferase from different promoters in microporated hADSCs. More important, the microporated hADSCs retained their multipotency and reporter gene expression was maintained for >2 weeks in vitro and in vivo. We further showed that a Tet-ON-inducible gene expression system could be microporated into hADSCs and that this system was functional following transplantation of the microporated cells into nude mice. Taken together, our data demonstrate that microporation allows a highly efficient transfection of hADSCs, without impairing their stem cell properties.

A novel cell-based therapy for contusion spinal cord injury using GDNF-delivering NIH3T3 cells with dual reporter genes monitored by molecular imaging

This aim of our study was to evaluate a novel cell-based therapy for contusion spinal cord injury (SCI) using embryonic-derived NIH3T3 cells, which endogenously express glial cell line-derived neurotrophic factor (GDNF).

METHODS

Proliferation and differentiation of transplanted NIH3T3 cells and their anti-apoptotic effects were examined after their engraftment into the spinal cords of Long-Evans rats subjected to acute SCI at the T10 vertebral level by a New York University impactor device. NIH3T3 cells were initially engineered to contain dual reporter genes, namely thymidine kinase (T) and enhanced green fluorescence protein (G), for in vivo cell tracking by both nuclear and fluorescence imaging modalities.

RESULTS

Planar and fluorescence imaging demonstrated that transplanted NIH3T3-TG cells at the L1 vertebral level migrated 2 cm distal to the injury site as early as 2 h, and the signals persisted for 48 h after SCI. The expression of GDNF by NIH3T3-TG cells was then confirmed by immunohistochemical analysis both in vitro and in vivo. GDNF-secreting NIH3T3-TG transplant provided anti-apoptotic effects in the injured cord over the period of 3 wk. Finally, NIH3T3-TG cells cultured under neuronal differentiation medium exhibited both morphologic and genetic resemblance to neuronal cells.

CONCLUSION

GDNF-secreting NIH3T3-TG cells in combination with molecular imaging could be a platform for developing therapeutic tools for acute SCI.