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

Intrathecal administration of mesenchymal stem cells in patients with adrenomyeloneuropathy

Background and objectives

X-linked adrenomyeloneuropathy (AMN) is an inherited neurodegenerative disorder associated with mutations in the ABCD1 gene and the accumulation of very long-chain fatty acids (VLFCAs) in plasma and tissues. Currently, there is no effective treatment for AMN. We have aimed to evaluate the therapeutic effects of mesenchymal stem cell (MSC) transplantation in patients with AMN.

Methods

This is a small cohort open-label study with patients with AMN diagnosed and treated at the University Hospital in Olsztyn, Poland. All patients met clinical, biochemical, MRI, and neuropsychological criteria for AMN. MSCs derived from Wharton jelly, 20 × 106 cells, were administered intrathecally three times every 2 months, and patients were followed up for an additional 3 months. The primary outcome measures included a blinded assessment of lower limb muscle strength with the Medical Research Council Manual Muscle Testing scale at baseline and on every month visits until the end of the study. Additional outcomes included measurements of the timed 25-feet walk (T25FW) and VLFCA serum ratio.

Results

Three male patients with AMN with an age range of 26-37 years participated in this study. All patients experienced increased muscle strength in the lower limbs at the end of the study versus baseline. The power grade increased by 25-43% at the baseline. In addition, all patients showed an improvement trend in walking speed measured with the T25FW test. Treatment with MSCs in patients with AMN appeared to be safe and well tolerated.

Discussion

The results of this study demonstrated that intrathecal administration of WJ-MSC improves motor symptoms in patients with AMN. The current findings lend support to the safety and feasibility of MSC therapy as a potentially viable treatment option for patients with AMN.

Volumetry of ovine incisors dental pulp for further regenerative therapy

Mesenchymal stem cells (MSCs) are used for regenerative therapy. Dental pulp MSCs make extracted wisdom teeth a useful resource in humans. Preclinical validation of regenerative therapies requires large animal models such as the sheep. Since stem cells can be retrieved from the dental pulp of ovine incisors, the best age to extract a maximal volume of dental pulp needs to be defined. The objective of this ex vivo study was to quantify incisors dental pulp volume, in sheep of various age. Three jaws were dedicated to histology (one per age group); the others were imaged with a computed tomography scanner [3 years-old (n = 9), 4 (n = 3) and 6 (n = 5)]. The incisors dental pulp volume was measured after 3D reconstruction. Multiple linear regression showed that dental pulp volume of ovine incisors decreases with age (β-estimate = -3.3; p < 0.0001) and teeth position from the more central to the more lateral (β-estimate = -4.9; p = 0.0009). Weight was not a relevant variable in the regression model. The dental pulp volume ranged from 36.7 to 19.6 mm3 in 3-year-old sheep, from 23.6 to 11.3 in 4-year-old sheep, and from 19.4 to 11.5 in 6-year-old sheep. The pulp volume of the most central teeth (first intermediate) was significantly higher than the most lateral teeth (corner). Haematoxylin-Eosin-Safran of the whole incisors, and of isolated dental pulps demonstrated a similar morphology to that in humans. The first intermediate incisor of 3-year-old sheep should be selected preferentially in preclinical research to retrieve the highest volume of dental pulp.

Comparison of Biological Properties and Clinical Application of Mesenchymal Stem Cells from the Mesoderm and Ectoderm

Since the discovery of mesenchymal stem cells (MSCs) in the 1970s, they have been widely used in the treatment of a variety of diseases because of their wide sources, strong differentiation potential, rapid expansion in vitro, low immunogenicity, and so on. At present, most of the related research is on mesoderm-derived MSCs (M-MSCs) such as bone marrow MSCs and adipose-derived MSCs. As a type of MSC, ectoderm-derived MSCs (E-MSCs) have a stronger potential for self-renewal, multidirectional differentiation, and immunomodulation and have more advantages than M-MSCs in some specific conditions. This paper analyzes the relevant research development of E-MSCs compared with that of M-MSCs; summarizes the extraction, discrimination and culture, biological characteristics, and clinical application of E-MSCs; and discusses the application prospects of E-MSCs. This summary provides a theoretical basis for the better application of MSCs from both ectoderm and mesoderm in the future.

Stem cell sources from human biological waste material: a role for the umbilical cord and dental pulp stem cells for regenerative medicine

Stem cell research with biological waste material is an area that holds promise to revolutionize treatment modalities and clinical practice. The interest in surgical remnants is increasing with time as research on human embryonic stem cells remains controversial due to legal and ethical issues. Perhaps, these restrictions are the motivation for the use of alternative mesenchymal stem cell (MSC) sources in the regenerative field. Stem cells (SCs) of Umbilical Cord (UC) and Dental Pulp (DP) have almost similar biological characteristics to other MSCs and can differentiate into a number of cell lineages with enormous potential future prospects. A concise critical observation of UC-MSCs and DP-MSCs is presented here reviewing articles from the last two decades along with other stem cell sources from different biological waste materials.

Development of secretome-based strategies to improve cell culture protocols in tissue engineering

Advances in skin tissue engineering have promoted the development of artificial skin substitutes to treat large burns and other major skin loss conditions. However, one of the main drawbacks to bioengineered skin is the need to obtain a large amount of viable epithelial cells in short periods of time, making the skin biofabrication process challenging and slow. Enhancing skin epithelial cell cultures by using mesenchymal stem cells secretome can favor the scalability of manufacturing processes for bioengineered skin. The effects of three different types of secretome derived from human mesenchymal stem cells, e.g. hADSC-s (adipose cells), hDPSC-s (dental pulp) and hWJSC-s (umbilical cord), were evaluated on cultured skin epithelial cells during 24, 48, 72 and 120 h to determine the potential of this product to enhance cell proliferation and improve biofabrication strategies for tissue engineering. Then, secretomes were applied in vivo in preliminary analyses carried out on Wistar rats. Results showed that the use of secretomes derived from mesenchymal stem cells enhanced currently available cell culture protocols. Secretome was associated with increased viability, proliferation and migration of human skin epithelial cells, with hDPSC-s and hWJSC-s yielding greater inductive effects than hADSC-s. Animals treated with hWJSC-s and especially, hDPSC-s tended to show enhanced wound healing in vivo with no detectable side effects. Mesenchymal stem cells derived secretomes could be considered as a promising approach to cell-free therapy able to improve skin wound healing and regeneration.

Comparison of the Angiogenic Ability between SHED and DPSC in a Mice Model with Critical Limb Ischemic

BACKGROUND

Regenerative medicine by using stem cells from dental pulp is promising for treating patients with critical limb ischemic (CLI). Here, we investigated the difference in the angiogenetic ability of stem cells from human exfoliated deciduous teeth (SHED) and human dental pulp stem cells (DPSC).

METHODS

SHED and DPSC were harvested from dental pulp and analyzed in flow- cytometry for detecting the expression of surface markers. Levels of angiogenetic marker were examined by RT-PCR and Western-blot. Eighteen immunodeficient mice of critical limb ischemic model were divided into three groups: SHED, DPSC and saline, which was administered with SHED, DPSC or saline intramuscularly. Histological examination was performed to detect the regenerative results.

RESULTS

A highly expression of CD146 was detected in SHED. Moreover, cells with negative expression of both CD146 and CD31 in SHED were more in comparison with those in DPSC. Expression of angiogenesis factors including CXCL12, CXCR4, Hif-1a, CD31, VEGF and bFGF were significant higher in SHED than DPSC by the RT-PCR and Western-Blot results. SHED induced more CD31 expression and less fibrous tissue formation in the critical limb ischemic model as compare with DPSC and saline.

CONCLUSION

Both SHED and DPSC possessed the ability of repairing CLI. With expressing more proangiogenesis factors, SHED may have the advantage of repairing CLI.

Laser-Assisted Fabrication of Injectable Nanofibrous Cell Carriers

The use of injectable biomaterials for cell delivery is a rapidly expanding field which may revolutionize the medical treatments by making them less invasive. However, creating desirable cell carriers poses significant challenges to the clinical implementation of cell-based therapeutics. At the same time, no method has been developed to produce injectable microscaffolds (MSs) from electrospun materials. Here the fabrication of injectable electrospun nanofibers is reported on, which retain their fibrous structure to mimic the extracellular matrix. The laser-assisted micro-scaffold fabrication has produced tens of thousands of MSs in a short time. An efficient attachment of cells to the surface and their proliferation is observed, creating cell-populated MSs. The cytocompatibility assays proved their biocompatibility, safety, and potential as cell carriers. Ex vivo results with the use of bone and cartilage tissues proved that NaOH hydrolyzed and chitosan functionalized MSs are compatible with living tissues and readily populated with cells. Injectability studies of MSs showed a high injectability rate, while at the same time, the force needed to eject the load is no higher than 25 N. In the future, the produced MSs may be studied more in-depth as cell carriers in minimally invasive cell therapies and 3D bioprinting applications.

The Potential Use of Mesenchymal Stem Cells and Their Derived Exosomes for Orthopedic Diseases Treatment

Musculoskeletal disorders (MSDs) are conditions that can affect muscles, bones, and joints. These disorders are very painful and severely limit patients' mobility and are more common in the elderly. MSCs are multipotent stem cells isolated from embryonic (such as the umbilical cord) and mature sources (such as adipose tissue and bone marrow). These cells can differentiate into various cells such as osteoblasts, adipocytes, chondrocytes, NP-like cells, Etc. Due to MSC characteristics such as immunomodulatory properties, ability to migrate to the site of injury, recruitment of cells involved in repair, production of growth factors, and large amount production of extracellular vesicles, these cells have been used in many regenerative-related medicine studies. Also, MSCs produce different types of EVs, such as exosomes, to the extracellular environment. Exosomes reflect MSCs' characteristics and do not have cell therapy-associated problems because they are cell-free. These vesicles carry proteins, nucleic acids, and lipids to the host cell and change their function. This review focuses on MSCs and MSCs exosomes' role in repairing dense connective tissues such as tendons, cartilage, invertebrate disc, bone fracture, and osteoporosis treatment.

Three-Dimensional Printable Conductive Semi-Interpenetrating Polymer Network Hydrogel for Neural Tissue Applications

Intrinsically conducting polymers (ICPs) are widely used to fabricate biomaterials; their application in neural tissue engineering, however, is severely limited because of their hydrophobicity and insufficient mechanical properties. For these reasons, soft conductive polymer hydrogels (CPHs) are recently developed, resulting in a water-based system with tissue-like mechanical, biological, and electrical properties. The strategy of incorporating ICPs as a conductive component into CPHs is recently explored by synthesizing the hydrogel around ICP chains, thus forming a semi-interpenetrating polymer network (semi-IPN). In this work, a novel conductive semi-IPN hydrogel is designed and synthesized. The hybrid hydrogel is based on a poly(N-isopropylacrylamide-co-N-isopropylmethacrylamide) hydrogel where polythiophene is introduced as an ICP to provide the system with good electrical properties. The fabrication of the hybrid hydrogel in an aqueous medium is made possible by modifying and synthesizing the monomers of polythiophene to ensure water solubility. The morphological, chemical, thermal, electrical, electrochemical, and mechanical properties of semi-IPNs were fully investigated. Additionally, the biological response of neural progenitor cells and mesenchymal stem cells in contact with the conductive semi-IPN was evaluated in terms of neural differentiation and proliferation. Lastly, the potential of the hydrogel solution as a 3D printing ink was evaluated through the 3D laser printing method. The presented results revealed that the proposed 3D printable conductive semi-IPN system is a good candidate as a scaffold for neural tissue applications.

Comparative evaluation of proliferative potential and replicative senescence associated changes in mesenchymal stem cells derived from dental pulp and umbilical cord

Mesenchymal stem cells (MSC) have been widely studied for tissue regeneration and cell-based therapy. MSC can be isolated from different body tissues while several biological waste sources like dental pulp, umbilical cord, cord derived blood, amniotic fluid or urine have also emerged as potential sources of MSCs. Specifically, isolation of MSCs from such non-conventional sources show promising outcomes due to the non-invasiveness of the extraction process and high proliferation capacity of the isolated MSC. However, these stem cells also exhibit the limitation of replicative senescence in long-term culture condition. Inter-cellular reactive oxygen species is an important contributor for inducing cellular senescence under long-term culture conditions. For translational application, it becomes imperative to compare the stem cells isolated from these sources for their senescence and proliferative properties. In this study, MSC were extracted from two different sources of biological waste materials-dental pulp and umbilical cord, and compared for their proliferation capacity and replicative senescence at different passage numbers (i.e. P2 and P6). Intracellular ROS production was significantly (p < 0.001) less in dental pulp stem cells culture in comparison to umbilical cord-derived stem cells at P6. The β-gal expression also showed significantly (p < 0.001) low expression in DPSC culture compared to that of UCSC at P6. The study indicates the source of stem cells influences the proliferation capacity as well as replicative senescence of MSCs. This study will thus pave the path of future research in selecting appropriate stem cell source for regenerative medicine application.

Mesenchymal stem cells: amazing remedies for bone and cartilage defects

Skeletal disorders are among the leading debilitating factors affecting millions of people worldwide. The use of stem cells for tissue repair has raised many promises in various medical fields, including skeletal disorders. Mesenchymal stem cells (MSCs) are multipotent stromal cells with mesodermal and neural crest origin. These cells are one of the most attractive candidates in regenerative medicine, and their use could be helpful in repairing and regeneration of skeletal disorders through several mechanisms including homing, angiogenesis, differentiation, and response to inflammatory condition. The most widely studied sources of MSCs are bone marrow (BM), adipose tissue, muscle, umbilical cord (UC), umbilical cord blood (UCB), placenta (PL), Wharton's jelly (WJ), and amniotic fluid. These cells are capable of differentiating into osteoblasts, chondrocytes, adipocytes, and myocytes in vitro. MSCs obtained from various sources have diverse capabilities of secreting many different cytokines, growth factors, and chemokines. It is believed that the salutary effects of MSCs from different sources are not alike in terms of repairing or reformation of injured skeletal tissues. Accordingly, differential identification of MSCs' secretome enables us to make optimal choices in skeletal disorders considering various sources. This review discusses and compares the therapeutic abilities of MSCs from different sources for bone and cartilage diseases.

Differentiation of cardiomyocyte-like cells from human amniotic fluid mesenchymal stem cells by combined induction with human platelet lysate and 5-azacytidine

Human amniotic fluid mesenchymal stem cells (hAF-MSCs) have been shown to be effective in the treatment of many diseases. Platelet lysate (PL) contains multiple growth and differentiation factors; therefore, it can be used as a differentiation inducer. In this study, we attempted to evaluate the efficiency of human platelet lysate (hPL) on cell viability and the effects on cardiomyogenic differentiation of hAF-MSCs. When treating the cells with hPL, the result showed an increase in cell viability. Expressions of cardiomyogenic specific genes, including GATA4, cTnT, Cx43 and Nkx2.5, were higher in the combined treatment groups of 5-azacytidine (5-aza) and hPL than the expressions of cardiomyogenic specific genes in the control group and in the 5-aza treatment group. In terms of the results of immunofluorescence and immunoenzymatic staining, the highest expressions of cardiomyogenic specific proteins were revealed in combined treatment groups. It can be summarized that hPL may be an effective supporting cardiomyogenic supplementary factor for cardiomyogenic differentiation in hAF-MSCs.

The Expression Profile of Dental Pulp-Derived Stromal Cells Supports Their Limited Capacity to Differentiate into Adipogenic Cells

Mesenchymal stromal cells (MSCs) can self-renew, differentiate into specialised cells and have different embryonic origins-ectodermal for dental pulp-derived MSCs (DPSCs) and mesodermal for adipose tissue-derived MSCs (ADSCs). Data on DPSCs adipogenic differentiation potential and timing vary, and the lack of molecular and genetic information prompted us to gain a better understanding of DPSCs adipogenic differentiation potential and gene expression profile. While DPSCs differentiated readily along osteogenic and chondrogenic pathways, after 21 days in two different types of adipogenic induction media, DPSCs cultures did not contain lipid vacuoles and had low expression levels of the adipogenic genes proliferator-activated receptor gamma (PPARG), lipoprotein lipase (LPL) and CCAAT/enhancer-binding protein alpha (CEBPA). To better understand this limitation in adipogenesis, transcriptome analysis in undifferentiated DPSCs was carried out, with the ADSC transcriptome used as a positive control. In total, 14,871 transcripts were common to DPSCs and ADSCs, some were unique (DPSCs: 471, ADSCs: 1032), and 510 were differentially expressed genes. Detailed analyses of overrepresented transcripts showed that DPSCs express genes that inhibit adipogenic differentiation, revealing the possible mechanism for their limited adipogenesis.

Angiogenic Effects of Human Dental Pulp and Bone Marrow-Derived Mesenchymal Stromal Cells and their Extracellular Vesicles

Blood vessel formation or angiogenesis is a key process for successful tooth regeneration. Bone marrow-derived mesenchymal stromal cells (BM-MSCs) possess paracrine proangiogenic properties, which are, at least partially, induced by their extracellular vesicles (EVs). However, the isolation of BM-MSCs is associated with several drawbacks, which could be overcome by MSC-like cells of the teeth, called dental pulp stromal cells (DPSCs). This study aims to compare the angiogenic content and functions of DPSC and BM-MSC EVs and conditioned medium (CM). The angiogenic protein profile of DPSC- and BM-MSC-derived EVs, CM and EV-depleted CM was screened by an antibody array and confirmed by ELISA. Functional angiogenic effects were tested in transwell migration and chicken chorioallantoic membrane assays. All secretion fractions contained several pro- and anti-angiogenic proteins and induced in vitro endothelial cell motility. This chemotactic potential was higher for (EV-depleted) CM, compared to EVs with a stronger effect for BM-MSCs. Finally, BM-MSC CM, but not DPSC CM, nor EVs, increased in ovo angiogenesis. In conclusion, we showed that DPSCs are less potent in relation to endothelial cell chemotaxis and in ovo neovascularization, compared to BM-MSCs, which emphasizes the importance of choice of cell type and secretion fraction for stem cell-based regenerative therapies in inducing angiogenesis.

Mesenchymal Stem/ Stromal Cells metabolomic and bioactive factors profiles: A comparative analysis on the umbilical cord and dental pulp derived Stem/ Stromal Cells secretome

Mesenchymal Stem/ Stromal Cells assume a supporting role to the intrinsic mechanisms of tissue regeneration, a feature mostly assigned to the contents of their secretome. A comparative study on the metabolomic and bioactive molecules/factors content of the secretome of Mesenchymal Stem/ Stromal Cells derived from two expanding sources: the umbilical cord stroma and the dental pulp is presented and discussed. The metabolic profile (Nuclear Magnetic Resonance Spectroscopy) evidenced some differences in the metabolite dynamics through the conditioning period, particularly on the glucose metabolism. Despite, overall similar profiles are suggested. More prominent differences are highlighted for the bioactive factors (Multiplexing Laser Bear Analysis), in which Follistatin, Growth Regulates Protein, Hepatocyte Growth Factor, Interleukin-8 and Monocyte Chemotactic Protein-1 dominate in Umbilical Cord Mesenchymal Stem/ Stromal Cells secretion, while in Dental Pulp Stem/ Stromal Cells the Vascular Endothelial Growth Factor-A and Follistatin are more evident. The distinct secretory cocktail did not result in significantly different effects on endothelial cell populations dynamics including proliferation, migration, tube formation capacity and in vivo angiogenesis, or in chemotaxis for both Mesenchymal Stem/ Stromal Cells populations.

Electrical Stimulation through Conductive Substrate to Enhance Osteo-Differentiation of Human Dental Pulp-Derived Stem Cells

Human dental pulp-derived stem cells (hDPSCs) are promising cellular sources for bone healing. The acceleration of their differentiation should be beneficial to their clinical application. Therefore, a conductive polypyrrole (PPy)-made electrical stimulation (ES) device was fabricated to provide direct-current electric field (DCEF) treatment, and its effect on osteo-differentiation of hDPSCs was investigated in this study. To determine the optimal treating time, electrical field of 0.33 V/cm was applied to hDPSCs once for 4 h on different days after the osteo-induction. The alizarin red S staining results suggested that ES accelerated the mineralization rates of hDPSCs. The quantification analysis results revealed a nearly threefold enhancement in calcium deposition by ES at day 0, 2, and 4, whereas the promotion effect in later stages was in vain. To determine the ES-mediated signaling pathway, the expression of genes in the bone morphogenetic protein (BMP) family and related receptors were quantified using qPCR. In the early stages of osteo-differentiation, the mRNA levels of BMP2, BMP3, BMP4, and BMP5 were increased significantly in the ES groups, indicating that these genes were involved in the specific signaling routes induced by ES. We are the first using DCEF to improve the osteo-differentiation of hDPSCs, and our results promise the therapeutic applications of hDPSCs on cell-based bone tissue engineering.

Preconditioning of Human Dental Pulp Stem Cells with Leukocyte- and Platelet-Rich Fibrin-Derived Factors Does Not Enhance Their Neuroregenerative Effect

Pathologies of the central nervous system are characterized by loss of brain tissue and neuronal function which cannot be adequately restored by endogenous repair processes. This stresses the need for novel treatment options such as cell-based therapies that are able to restore damaged tissue or stimulate repair. This study investigated the neuroregenerative potential of the conditioned medium of human dental pulp stem cells (CM-hDPSCs) on neural stem cell (NSC) proliferation and migration as well as on neurite outgrowth of primary cortical neurons (pCNs). Additionally, the effect of leukocyte- and platelet-rich fibrin (L-PRF) priming on the neuroregenerative potential of the hDPSC secretome on NSCs and pCNs was evaluated. L-PRF contains factors that enhance stem cell-induced regeneration, but its effect on hDPSC-mediated neuroregeneration is unknown. This study demonstrated that CM-hDPSCs enhanced neuritogenesis. Moreover, CM-hDPSCs had a chemoattractant effect on NSCs. Although priming hDPSCs with L-PRF increased brain-derived neurotrophic factor secretion, no additional effects on the paracrine-mediated repair mechanisms were observed. These data support the neuroregenerative potential of hDPSCs, and although priming had no additional effect, the potential of L-PRF-primed hDPSCs on distinct regenerative mechanisms remains to be clarified.

Autologous plasma rich in growth factors technology for isolation and ex vivo expansion of human dental pulp stem cells for clinical translation

AIM

This study investigated the use of the autologous technology of plasma rich in growth factors (PRGF) as a human-based substitute to fetal bovine serum (FBS) in the culture of human dental pulp stem cells.

MATERIALS & METHODS

Stem cell characterization was performed. Analysis of isolation, proliferation, migration, trilineage differentiation, senescence and cryopreservation were compared between FBS and PRGF.

RESULTS

Human dental pulp stem cell cultures isolated and maintained with PRGF showed a significantly higher number of cells per explant than FBS cultures. Cell proliferation, migration, osteogenic mineralization and adipogenic differentiation were found to be significantly higher in PRGF than FBS.

CONCLUSION

The autologous PRGF technology could be a suitable and safer substitute for FBS as a culture medium supplement for clinical translation of cell therapy.

Safety of intrathecal injection of Wharton's jelly-derived mesenchymal stem cells in amyotrophic lateral sclerosis therapy

Animal experiments have confirmed that mesenchymal stem cells can inhibit motor neuron apoptosis and inflammatory factor expression and increase neurotrophic factor expression. Therefore, mesenchymal stem cells have been shown to exhibit prospects in the treatment of amyotrophic lateral sclerosis. However, the safety of their clinical application needs to be validated. To investigate the safety of intrathecal injection of Wharton's jelly-derived mesenchymal stem cells in amyotrophic lateral sclerosis therapy, 43 patients (16 females and 27 males, mean age of 57.3 years) received an average dose of 0.42 × 10⁶ cells/kg through intrathecal administration at the cervical, thoracic or lumbar region depending on the clinical symptoms. There was a 2 month interval between two injections. The adverse events occurring during a 6-month treatment period were evaluated. No adverse events occurred. Headache occurred in one case only after first injection of stem cells. This suggests that intrathecal injection of Wharton's Jelly-derived mesenchymal stem cells is well tolerated in patients with amyotrophic lateral sclerosis. This study was approved by the Bioethical Committee of School of Medicine, University of Warmia and Mazury in Olsztyn, Poland (approval No. 36/2014 and approval No. 8/2016). This study was registered with the ClinicalTrials.gov (identifier: NCT02881476) on August 29, 2016.

Low-dose radiations derived from cone-beam CT induce transient DNA damage and persistent inflammatory reactions in stem cells from deciduous teeth

OBJECTIVES

Cone-beam CT (CBCT), a radiographic tool for diagnosis, treatment, and follow-up in dental practice, was introduced also in pediatric radiology, especially orthodontics. Such patients subjected to repetitive X-rays examinations may receive substantial levels of radiation doses. Ionizing radiation (IR), a recognized carcinogenic factor causing DNA double-strand breaks (DSBs) could be harmful to undifferentiated cells such as dental pulp stem cells (DPSCs) since inaccurately repaired or unrepaired DSBs may lead to malignant transformation. The H2AX and MRE11 proteins generated following DSBs formation and pro-inflammatory cytokines (CKs) secreted after irradiation are relevant candidates to monitor the cellular responses induced by CBCT.

METHODS

DPSCs were extracted from human exfoliated deciduous teeth and their phenotype was assessed by immunocytochemistry and flow-cytometry. Cells were exposed to IR doses: 5.4-107.7 mGy, corresponding to 0.5-8 consecutive skull exposures, respectively. H2AX and MRE11 were detected in whole cells, while IL-1α, IL-6, IL-8, TNFα in supernatants, using enzyme-linked immunosorbent assay (ELISA) at different time points after exposure.

RESULTS

The phosphorylation level of H2AX in DPSCs increased considerably at 0.5 h after exposure (p < 0.001 for 3, 5, 8 skull exposures and p < 0.05 for 1 skull exposure, respectively). MRE11 response could only be detected for the highest IR dose (p < 0.001) in the same interval. CKs secretion increased upon CBCT exposure according to doses and time.

CONCLUSIONS

The DPSCs exposure to CBCT induces transient DNA damage and persistent inflammatory reaction in DPSCs drawing the attention on the potential risks of IR exposures and on the importance of dose monitoring in pediatric population.

Mesenchymal Stem Cell-Based Therapy for Cardiovascular Disease: Progress and Challenges

Administration of mesenchymal stem cells (MSCs) to diseased hearts improves cardiac function and reduces scar size. These effects occur via the stimulation of endogenous repair mechanisms, including regulation of immune responses, tissue perfusion, inhibition of fibrosis, and proliferation of resident cardiac cells, although rare events of transdifferentiation into cardiomyocytes and vascular components are also described in animal models. While these improvements demonstrate the potential of stem cell therapy, the goal of full cardiac recovery has yet to be realized in either preclinical or clinical studies. To reach this goal, novel cell-based therapeutic approaches are needed. Ongoing studies include cell combinations, incorporation of MSCs into biomaterials, or pre-conditioning or genetic manipulation of MSCs to boost their release of paracrine factors, such as exosomes, growth factors, microRNAs, etc. All of these approaches can augment therapeutic efficacy. Further study of the optimal route of administration, the correct dose, the best cell population(s), and timing for treatment are parameters that still need to be addressed in order to achieve the goal of complete cardiac regeneration. Despite significant progress, many challenges remain.

Progress in the use of dental pulp stem cells in regenerative medicine

The field of tissue engineering is emerging as a multidisciplinary area with promising potential for regenerating new tissues and organs. This approach requires the involvement of three essential components: stem cells, scaffolds and growth factors. To date, dental pulp stem cells have received special attention because they represent a readily accessible source of stem cells. Their high plasticity and multipotential capacity to differentiate into a large array of tissues can be explained by its neural crest origin, which supports applications beyond the scope of oral tissues. Many isolation, culture and cryopreservation protocols have been proposed that are known to affect cell phenotype, proliferation rate and differentiation capacity. The clinical applications of therapies based on dental pulp stem cells demand the development of new biomaterials suitable for regenerative purposes that can act as scaffolds to handle, carry and implant stem cells into patients. Currently, the development of xeno-free culture media is emerging as a means of standardization to improve safe and reproducibility. The present review aims to describe the current knowledge of dental pulp stem cells, considering in depth the key aspects related to the characterization, establishment, maintenance and cryopreservation of primary cultures and their involvement in the multilineage differentiation potential. The main clinical applications for these stem cells and their combination with several biomaterials is also covered.

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.

Paracrine Maturation and Migration of SH-SY5Y Cells by Dental Pulp Stem Cells

Neurological disorders are characterized by neurodegeneration and/or loss of neuronal function, which cannot be adequately repaired by the host. Therefore, there is need for novel treatment options such as cell-based therapies that aim to salvage or reconstitute the lost tissue or that stimulate host repair. The present study aimed to evaluate the paracrine effects of human dental pulp stem cells (hDPSCs) on the migration and neural maturation of human SH-SY5Y neuroblastoma cells. The hDPSC secretome had a significant chemoattractive effect on SH-SY5Y cells as shown by a transwell assay. To evaluate neural maturation, SH-SY5Y cells were first induced toward neuronal cells, after which they were exposed to the hDPSC secretome. In addition, SH-SY5Y cells subjected to the hDPSC secretome showed increased neuritogenesis compared with nonexposed cells. Maturated cells were shown to increase immune reactivity for neuronal markers compared with controls. Ultrastructurally, retinoic acid (RA) signaling and subsequent exposure to the hDPSC secretome induced a gradual rise in metabolic activity and neuronal features such as multivesicular bodies and cytoskeletal elements associated with cellular communication. In addition, electrophysiological recordings of differentiating cells demonstrated a transition toward a neuronal electrophysiological profile based on the maximum tetrodotoxin (TTX)–sensitive, Na+ current. Moreover, conditioned medium (CM)–hDPSC–maturated SH-SY5Y cells developed distinct features including, Cd2+-sensitive currents, which suggests that CM-hDPSC–maturated SH-SY5Y acquired voltage-gated Ca2+ channels. The results reported in this study demonstrate the potential of hDPSCs to support differentiation and recruitment of cells with neuronal precursor characteristics in a paracrine manner. Moreover, this in vitro experimental design showed that the widely used SH-SY5Y cell line can improve and simplify the preclinical in vitro research on the molecular mechanisms of stem cell–mediated neuronal regeneration.

In vitro characterization of human dental pulp stem cells isolated by three different methods

OBJECTIVES

In this study, we characterized human dental pulp cells (HDPCs) obtained by different culture methods to establish the most suitable methodology for dental tissue engineering and regenerative endodontic applications.

MATERIALS AND METHODS

HDPCs were isolated by the outgrowth method (HDPCs-OG), the enzymatic digestion method (collagenase/dispase/trypsin, HDPCs-ED), or the combination of both methods (HDPCs-Combined). The expression of mesenchymal stem cell markers (CD105, CD90, and CD73) was investigated. In vitro differentiation capacities of HDPCs into adipogenic, osteogenic, and chondrogenic lineages were compared. Differentiation markers were analyzed by quantitative reverse-transcription polymerase chain reaction (RT-PCR) and western blotting.

RESULTS

Our data indicated that whole HDPCs-ED, HPDCs-OG, and HDPCs-Combined could be differentiated into adipogenic, chrondrogenic, and osteogenic cell types. However, we found that the methods for isolating and culturing HDPCs influence the differentiation capacities of cells. HDPCs-OG and HDPCs-ED were preferably differentiated into adipogenic and osteogenic cells, respectively. Differentiation markers shown by RT-PCR and western blotting analysis were mostly upregulated in the treated groups compared with the control groups.

CONCLUSIONS

Our findings confirmed that cell populations formed by two different culture methods and the combined culture method exhibited different properties. The results of this study could provide an insight into regenerative endodontic treatment using HDPCs.

Label-Free Imaging of Umbilical Cord Tissue Morphology and Explant-Derived Cells

In situ detection of MSCs remains difficult and warrants additional methods to aid with their characterization in vivo. Two-photon confocal laser scanning microscopy (TPM) and second harmonic generation (SHG) could fill this gap. Both techniques enable the detection of cells and extracellular structures, based on intrinsic properties of the specific tissue and intracellular molecules under optical irradiation. TPM imaging and SHG imaging have been used for label-free monitoring of stem cells differentiation, assessment of their behavior in biocompatible scaffolds, and even cell tracking in vivo. In this study, we show that TPM and SHG can accurately depict the umbilical cord architecture and visualize individual cells both in situ and during culture initiation, without the use of exogenously applied labels. In combination with nuclear DNA staining, we observed a variance in fluorescent intensity in the vessel walls. In addition, antibody staining showed differences in Oct4, αSMA, vimentin, and ALDH1A1 expression in situ, indicating functional differences among the umbilical cord cell populations. In future research, marker-free imaging can be of great added value to the current antigen-based staining methods for describing tissue structures and for the identification of progenitor cells in their tissue of origin.

In Vitro and In Vivo Differentiation of Progenitor Stem Cells Obtained After Mechanical Digestion of Human Dental Pulp

Human population is facing a revolutionary change in the demographic structure with an increasing number of elderly people requiring an unmet need to ensure a smooth aging process and dental care is certainly an important aspect that has to be considered. To date, dentistry has been conservative and the need of transferring the scientific models of regenerative dentistry into clinical practice is becoming a necessity. The aim of this study was to characterize the differentiation commitment (in vitro) and the clinical grafting ability (in vivo) of a population of progenitor stem cells obtained after mechanical digestion of dental pulp with an innovative system recently developed. This approach was successfully used in previous studies to obtain a clinical-grade ready to use dental pulp fragments that could be grafted in autologous tissues to obtain bone. We are thus showing that micro grafts resulting from mechanical digestion contain stem cells with a mesenchymal phenotype, able to differentiate toward different cell types and to generate new bone in patients. We are providing data for the establishment of standardized and routinely oral surgery approaches, having outlined the cellular properties of human stem cells obtained from the dental pulp. This method can represent a valid tool for both regenerative medicine and tissue engineering purposes not only applicable to the cranio-maxillofacial region but, likely, to different bone pathologies for a fastening and healing recovering of patients. J. Cell. Physiol. 232: 548-555, 2017. © 2016 Wiley Periodicals, Inc.

Current View on Osteogenic Differentiation Potential of Mesenchymal Stromal Cells Derived from Placental Tissues

Mesenchymal stromal cells (MSC) isolated from human term placental tissues possess unique characteristics, including their peculiar immunomodulatory properties and their multilineage differentiation potential. The osteogenic differentiation capacity of placental MSC has been widely disputed, and continues to be an issue of debate. This review will briefly discuss the different MSC populations which can be obtained from different regions of human term placenta, along with their unique properties, focusing specifically on their osteogenic differentiation potential. We will present the strategies used to enhance osteogenic differentiation potential in vitro, such as through the selection of subpopulations more prone to differentiate, the modification of the components of osteo-inductive medium, and even mechanical stimulation. Accordingly, the applications of three-dimensional environments in vitro and in vivo, such as non-synthetic, polymer-based, and ceramic scaffolds, will also be discussed, along with results obtained from pre-clinical studies of placental MSC for the regeneration of bone defects and treatment of bone-related diseases.

Genetic Comparison of Stemness of Human Umbilical Cord and Dental Pulp

This study focuses on gene expression patterns and functions in human umbilical cord (UC) and dental pulp (DP) containing mesenchymal stem cells (MSCs). DP tissues were collected from 25 permanent premolars. UC tissue samples were obtained from three newborns. Comparative gene profiles were obtained using cDNA microarray analysis and the expression of tooth development-associated and MSC-related genes was assessed by the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Genes related to cell proliferation, angiogenesis, and immune responses were expressed at higher levels in UC, whereas genes related to growth factor and receptor activity and signal transduction were more highly expressed in DP. Although UC and DP tissues exhibited similar expression of surface markers for MSCs, UC showed higher expression of CD29, CD34, CD44, CD73, CD105, CD146, and CD166. qRT-PCR analysis showed that CD146, CD166, and MYC were expressed 18.3, 8.24, and 1.63 times more highly in UC, whereas the expression of CD34 was 2.15 times higher in DP. Immunohistochemical staining revealed significant differences in the expression of genes (DSPP, DMP1, and CALB1) related to odontogenesis and angiogenesis in DP. DP and UC tissue showed similar gene expression, with the usual MSC markers, while they clearly diverged in their differentiation capacity.

Morphological features of cell death and tissue remolding of fat grafts

BACKGROUND

Fat tissue graft has been commonly used for soft tissue augmentation. However, the mechanisms underlying the maintenance of graft volume and weight are still unclear. As morphological features provide direct evidences for cell death and survival, we aimed to investigate the fate of grafted adipocytes and the dynamic changes in the remodeling of adipose tissues by transmission electron microscopy technique.

METHODS

The unilateral inguinal fat pad of C57BL/6J mice was autografted to the dorsa of the mice. Perilipin expression and morphological changes were investigated by immunohistochemistry staining and transmission electron microscopy, respectively, in grafted tissues collected at posttransplantation days 0, 1, 3, 5, 7, 14, and 30.

RESULTS

Transmission electron microscopy analysis revealed that most adipocytes in grafts showed traits of cell death on postgrafting day 3. Multilocular adipocytes with naive nuclei were observed as early as day 5 and a larger number of multilocular adipocytes were found on day 14. Perilipin immunostaining revealed that only some adipocytes located in the margin of grafts survived through the ischemic injury. New adipocytes were visualized at the periphery of the grafts, although the scope of viable adipocyte zonal areas increased from day 5 to day 30.

CONCLUSIONS

The results provide ultrastructural evidences associated with the remodeling dynamics of adipose tissue grafts. It is suggested that maximized volume of graft should be obtained through promoting regeneration other than improving survival of grafted adipose tissues.

Assessment of an efficient xeno-free culture system of human periodontal ligament stem cells

The possibility of transplanting adult stem cells into damaged organs has opened new prospects for the treatment of several human pathologies. The purpose of this study was to develop a culture system for the expansion and production of human Periodontal Ligament Stem Cells (hPDLSCs) using a new xeno-free media formulation and ensuring the maintenance of the stem cells features comprising the multiple passage expansion, mesengenic lineage differentiation, cellular phenotype, and genomic stability, essential elements for conforming to translation to cell therapy. Somatic stem cells were isolated from the human periodontium using a minimally invasive periodontal access flap surgery in healthy donors. Expanded hPDLSCs in a xeno-free culture showed the morphological features of stem cells, expressed the markers associated with pluripotency, and a normal karyotype. Under appropriate culture conditions, hPDLSCs presented adipogenic and osteogenic potential; indeed, a very high accumulation of lipid droplets was evident in the cytoplasm of adipogenic-induced cells, and indisputable evidence of osteogenic differentiation, investigated by transmission electron microscopy, and analyzed for gene expression analysis has been shown. Based on these data, the novel xeno-free culture method might provide the basis for Good Manufacturing Procedure culture of autologous stem cells, readily accessible from human periodontium, and can be a resource to facilitate their use in human clinical studies for potential therapeutic regeneration.

Osteogenic Potential of Dental Mesenchymal Stem Cells in Preclinical Studies: A Systematic Review Using Modified ARRIVE and CONSORT Guidelines

Background and Objective. Dental stem cell-based tissue engineered constructs are emerging as a promising alternative to autologous bone transfer for treating bone defects. The purpose of this review is to systematically assess the preclinical in vivo and in vitro studies which have evaluated the efficacy of dental stem cells on bone regeneration. Methods. A literature search was conducted in Ovid Medline, Embase, PubMed, and Web of Science up to October 2014. Implantation of dental stem cells in animal models for evaluating bone regeneration and/or in vitro studies demonstrating osteogenic potential of dental stem cells were included. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were used to ensure the quality of the search. Modified ARRIVE (Animal research: reporting in invivo experiments) and CONSORT (Consolidated reporting of trials) were used to critically analyze the selected studies. Results. From 1914 citations, 207 full-text articles were screened and 137 studies were included in this review. Because of the heterogeneity observed in the studies selected, meta-analysis was not possible. Conclusion. Both in vivo and in vitro studies indicate the potential use of dental stem cells in bone regeneration. However well-designed randomized animal trials are needed before moving into clinical trials.

Effect of allogeneic umbilical cord mesenchymal stem cell transplantation in a rat model of hepatic cirrhosis

OBJECTIVE

To determine the effects of human umbilical cord mesenchymal stem cell (UCMSC) transplantation, alone or in combination with tanshinone IIA (Tan IIA) on hepatic cirrhosis in rats.

METHODS

A rat model of cirrhosis was established. Rats were divided into control, UCMSC, and UCSMC plus Tan IIA groups. Rats in the UCMSC group were injected via the tail vein with 0.2 mL Dil-labeled UCMSC suspension. Intraperitoneal Tan IIA injections (20 mg/kg) were started on the day of UCMSC transplantation in the UCMSC plus Tan IIA group, and continued for 7 consecutive days thereafter. Rats were sacrificed 1 day, 3 days, 1 month, and 3 months after transplantation and the numbers of Dil-labeled UCMSCs colonizing the liver were determined. Albumin (ALB) and alanine aminotransferase (ALT) levels were measured in venous blood, and mRNA and protein expression levels of human ALB and cytokeratin (CK)-18 in liver tissues were determined by reverse transcription-polymerase chain reaction and western blotting, respectively.

RESULTS

Serum ALT levels were significantly lower and serum ALB levels significantly higher in rats in the UCMSC group compared with the control group (P < 0.05). Hepatic CK-18 and ALB mRNA and protein expression levels increased after transplantation, and were significantly higher in the UCMSC plus Tan IIA group compared with the UCMSC group (P < 0.05).

CONCLUSION

Human UCMSCs transplanted into rats with liver cirrhosis can grow and differentiate into hepatocyte-like cells resulting in improved liver function in vivo. Tan IIA further influenced transplantation outcomes.

Neurogenic maturation of human dental pulp stem cells following neurosphere generation induces morphological and electrophysiological characteristics of functional neurons

Cell-based therapies are emerging as an alternative treatment option to promote functional recovery in patients suffering from neurological disorders, which are the major cause of death and permanent disability. The present study aimed to differentiate human dental pulp stem cells (hDPSCs) toward functionally active neuronal cells in vitro. hDPSCs were subjected to a two-step protocol. First, neuronal induction was acquired through the formation of neurospheres, followed by neuronal maturation, based on cAMP and neurotrophin-3 (NT-3) signaling. At the ultrastructural level, it was shown that the intra-spheral microenvironment promoted intercellular communication. hDPSCs grew out of the neurospheres in vitro and established a neurogenic differentiated hDPSC culture (d-hDPSCs) upon cAMP and NT-3 signaling. d-hDPSCs were characterized by the increased expression of neuronal markers such as neuronal nuclei, microtubule-associated protein 2, neural cell adhesion molecule, growth-associated protein 43, synapsin I, and synaptophysin compared with nondifferentiated hDPSCs. Enzyme-linked immunosorbent assay demonstrated that the secretion of brain-derived neurotrophic factor, vascular endothelial growth factor, and nerve growth factor differed between d-hDPSCs and hDPSCs. d-hDPSCs acquired neuronal features, including multiple intercommunicating cytoplasmic extensions and increased vesicular transport, as shown by the electron microscopic observation. Patch clamp analysis demonstrated the functional activity of d-hDPSCs by the presence of tetrodotoxin- and tetraethyl ammonium-sensitive voltage-gated sodium and potassium channels, respectively. A subset of d-hDPSCs was able to fire a single action potential. The results reported in this study demonstrate that hDPSCs are capable of neuronal commitment following neurosphere formation, characterized by distinct morphological and electrophysiological properties of functional neuronal cells.

Human Wharton's Jelly-Derived Stem Cells Display Immunomodulatory Properties and Transiently Improve Rat Experimental Autoimmune Encephalomyelitis

Umbilical cord matrix or Wharton's jelly-derived stromal cells (WJ-MSCs) are an easily accessible source of mesenchymal-like stem cells. Recent studies describe a hypoimmunogenic phenotype, multipotent differentiation potential, and trophic support function for WJ-MSCs, with variable clinical benefit in degenerative disease models such as stroke, myocardial infarction, and Parkinson's disease. It remains unclear whether WJ-MSCs have therapeutic value for multiple sclerosis (MS), where autoimmune-mediated demyelination and neurodegeneration need to be halted. In this study, we investigated whether WJ-MSCs possess the required properties to effectively and durably reverse these pathological hallmarks and whether they survive in an inflammatory environment after transplantation. WJ-MSCs displayed a lowly immunogenic phenotype and showed intrinsic expression of neurotrophic factors and a variety of anti-inflammatory molecules. Furthermore, they dose-dependently suppressed proliferation of activated T cells using contact-dependent and paracrine mechanisms. Indoleamine 2,3-dioxygenase 1 was identified as one of the main effector molecules responsible for the observed T-cell suppression. The immune-modulatory phenotype of WJ-MSCs was further enhanced after proinflammatory cytokine treatment in vitro (licensing). In addition to their effect on adaptive immunity, WJ-MSCs interfered with dendritic cell differentiation and maturation, thus directly affecting antigen presentation and therefore T-cell priming. Systemically infused WJ-MSCs potently but transiently ameliorated experimental autoimmune encephalomyelitis (EAE), an animal model for MS, when injected at onset or during chronic disease. This protective effect was paralleled with a reduction in autoantigen-induced T-cell proliferation, confirming their immunomodulatory activity in vivo. Surprisingly, in vitro licensed WJ-MSCs did not ameliorate EAE, indicative of a fast rejection as a result of enhanced immunogenicity. Collectively, we show that WJ-MSCs have trophic support properties and effectively modulate immune cell functioning both in vitro and in the EAE model, suggesting WJ-MSC may hold promise for MS therapy. Future research is needed to optimize survival of stem cells and enhance clinical durability.

Bobby Sox homology regulates odontoblast differentiation of human dental pulp stem cells/progenitors

BACKGROUND

Transcription factors have been implicated in regulating the differentiation of odontoblasts from dental pulp stem cells/progenitors (DPSCs/progenitors), but their regulatory network is not completely understood.

RESULT

New transcription factors that control the odontoblast differentiation of human DPSCs/progenitors were analyzed using a microarray. The result revealed bobby sox homolog (BBX) to be expressed most strongly during odontoblast differentiation. Validation using RT-PCR also revealed the strong expression of BBX during the odontoblast differentiation of DPSCs/progenitors. BBX expression was also detected in adult molar odontoblasts and other tissues, including the heart, kidney, testis, and bone marrow. To understand the role of BBX in odontoblast differentiation, BBX variant 1 and 2 cDNA were cloned and overexpressed in DPSCs/progenitors. The results showed that the overexpression of BBX cDNA in DPSCs/progenitors induced substantial mineralization and expression of the odontoblast marker genes, such as ALP, OPN, BSP, DMP1, and DSPP. The knockdown of BBX using shRNA, however, did not affect mineralization, but the expression of ALP and DSPP was decreased substantially. Meanwhile overexpression or knockdown of BBX did not modulate proliferation of DPSCs/progenitors.

CONCLUSION

Our results suggest that BBX plays an important role during the odontoblast differentiation of human DPSCs/progenitors.

Proteomic analysis of mesenchymal stem cells from normal and deep carious dental pulp

Dental pulp stem cells (DPSCs), precursor cells of odontoblasts, are ideal seed cells for tooth tissue engineering and regeneration. Our previous study has demonstrated that stem cells exist in dental pulp with deep caries and are called carious dental pulp stem cells (CDPSCs). The results indicated that CDPSCs had a higher proliferative and stronger osteogenic differentiation potential than DPSCs. However, the molecular mechanisms responsible for the biological differences between DPSCs and CDPSCs are poorly understood. The aim of this study was to define the molecular features of DPSCs and CDPSCs by comparing the proteomic profiles using two-dimensional fluorescence difference gel electrophoresis (2-D DIGE) in combination with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Our results revealed that there were 18 protein spots differentially expressed between DPSCs and CDPSCs in a narrow pH range of 4 to 7. These differently expressed proteins are mostly involved in the regulation of cell proliferation, differentiation, cell cytoskeleton and motility. In addition, our results suggested that CDPSCs had a higher expression of antioxidative proteins that might protect CDPSCs from oxidative stress. This study explores some potential proteins responsible for the biological differences between DPSCs and CDPSCs and expands our understanding on the molecular mechanisms of mineralization of DPSCs in the formation of the dentin-pulp complex.

Human dental pulp stem cells can differentiate into Schwann cells and promote and guide neurite outgrowth in an aligned tissue-engineered collagen construct in vitro

In the present study, we evaluated the differentiation potential of human dental pulp stem cells (hDPSCs) toward Schwann cells, together with their functional capacity with regard to myelination and support of neurite outgrowth in vitro. Successful Schwann cell differentiation was confirmed at the morphological and ultrastructural level by transmission electron microscopy. Furthermore, compared to undifferentiated hDPSCs, immunocytochemistry and ELISA tests revealed increased glial marker expression and neurotrophic factor secretion of differentiated hDPSCs (d-hDPSCs), which promoted survival and neurite outgrowth in 2-dimensional dorsal root ganglia cultures. In addition, neurites were myelinated by d-hDPSCs in a 3-dimensional collagen type I hydrogel neural tissue construct. This engineered construct contained aligned columns of d-hDPSCs that supported and guided neurite outgrowth. Taken together, these findings provide the first evidence that hDPSCs are able to undergo Schwann cell differentiation and support neural outgrowth in vitro, proposing them to be good candidates for cell-based therapies as treatment for peripheral nerve injury.—Martens, W., Sanen, K., Georgiou, M., Struys, T., Bronckaers, A., Ameloot, M., Phillips, J., Lambrichts, I. Human dental pulp stem cells can differentiate into Schwann cells and promote and guide neurite outgrowth in an aligned tissue-engineered collagen construct in vitro.

Sensitive in vivo cell detection using size-optimized superparamagnetic nanoparticles

Magnetic nanoparticle (MNP) enabled cell visualization with magnetic resonance imaging (MRI) is currently an intensively studied area of research. In the present study, we have synthesized polyethylene glycolated (PEG) MNPs and validated their suitability as MR cell labeling agents in in vitro and in vivo experiments. The labeling of therapeutic potent mesenchymal stem cells (MSCs) with small core and large core MNPs was evaluated. Both MNPs were, in combination with a transfection agent, stably internalized into the MSCs and didn't show an effect on cell metabolism. The labeled cells showed high contrast in MRI phantom studies. For quantification purposes, the MRI contrast generating properties of cells labeled with small core MNPs were compared with large core MNPs and with the commercial contrast agent Endorem. MSCs labeled with the large core MNPs showed the highest contrast generating properties in in vitro phantom studies and in in vivo intracranial stereotactic injection experiments, confirming the size-relaxivity relationship in biological systems. Finally, the distribution of MSCs pre-labeled with large core PEGylated MNPs was visualized non-invasively with MRI in a glioma model.

Magnetic Resonance Imaging of Human Dental Pulp Stem Cells in Vitro and in Vivo

Recent advances in stem cell research have shown the promising nature of mesenchymal stem cells as plausible candidates for cell-based regenerative medicine. Many studies reported the use of human dental pulp stem cells (hDPSCs), which possess self-renewal capacity, high proliferation potential, and the ability to undergo multilineage differentiation. Together with this therapeutic approach, development of effective, noninvasive and nontoxic imaging techniques for visualizing and tracking the cells in vivo is crucial for the evaluation and improvement of stem cell therapy. Magnetic resonance imaging (MRI) is one of the most powerful diagnostic imaging techniques currently available for in vivo diagnosis and has been proposed as the most attractive modality for monitoring stem cell migration. The aim of this study was to investigate the labeling efficiency of hDPSCs using superparamagnetic iron oxide (SPIO) particles in order to allow visualization using in vitro and in vivo MRI without influencing cellular metabolism. MRI and transmission electron microscopy (TEM) showed optimal uptake with low SPIO concentrations of 15 μg/ml in combination with 0.75 μg/ml poly-l-lysine (PLL) resulting in more than 13 pg iron/cell and an in vitro detection limit of 50 labeled cells/μl. Very low SPIO concentrations in the culture medium resulted in extremely high labeling efficiency not reported before. For these conditions, tetrazolium salt assays showed no adverse effects on cell viability. Furthermore, in vivo MRI was performed to detect labeled hDPSCs transplanted into the brain of Rag 2-γ C immune-deficient mice. Transplanted cells did not show any signs of tumorgenecity or teratoma formation during the studied time course. We have reported on a labeling and imaging strategy to visualize human dental pulp stem cells in vivo using MRI. These data provide a solid base to allow cell tracking in future regenerative studies in the brain longitudinally.

Angiogenic properties of human dental pulp stem cells

Angiogenesis, the formation of capillaries from pre-existing blood vessels, is a key process in tissue engineering. If blood supply cannot be established rapidly, there is insufficient oxygen and nutrient transport and necrosis of the implanted tissue will occur. Recent studies indicate that the human dental pulp contains precursor cells, named dental pulp stem cells (hDPSC) that show self-renewal and multilineage differentiation capacity. Since these cells can be easily isolated, cultured and cryopreserved, they represent an attractive stem cell source for tissue engineering. Until now, only little is known about the angiogenic abilities and mechanisms of the hDPSC. In this study, the angiogenic profile of both cell lysates and conditioned medium of hDPSC was determined by means of an antibody array. Numerous pro-and anti-angiogenic factors such as vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1), plasminogen activator inhibitor-1 (PAI-1) and endostatin were found both at the mRNA and protein level. hDPSC had no influence on the proliferation of the human microvascular endothelial cells (HMEC-1), but were able to significantly induce HMEC-1 migration in vitro. Addition of the PI3K-inhibitor LY294002 and the MEK-inhibitor U0126 to the HMEC-1 inhibited this effect, suggesting that both Akt and ERK pathways are involved in hDPSC-mediated HMEC-1 migration. Antibodies against VEGF also abolished the chemotactic actions of hDPSC. Furthermore, in the chicken chorioallantoic membrane (CAM) assay, hDPSC were able to significantly induce blood vessel formation. In conclusion, hDPSC have the ability to induce angiogenesis, meaning that this stem cell population has a great clinical potential, not only for tissue engineering but also for the treatment of chronic wounds, stroke and myocardial infarctions.

Dental stem cells and their promising role in neural regeneration: an update

INTRODUCTION

Stem cell-based therapies are considered to be a promising treatment method for several clinical conditions such as Alzheimer's disease, Parkinson's disease, spinal cord injury, and many others. However, the ideal stem cell type for stem cell-based therapy remains to be elucidated.

DISCUSSION

Stem cells are present in a variety of tissues in the embryonic and adult human body. Both embryonic and adult stem cells have their advantages and disadvantages concerning the isolation method, ethical issues, or differentiation potential. The most described adult stem cell population is the mesenchymal stem cells due to their multi-lineage (trans)differentiation potential, high proliferative capacity, and promising therapeutic values. Recently, five different cell populations with mesenchymal stem cell characteristics were identified in dental tissues: dental pulp stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, dental follicle precursor cells, and stem cells from apical papilla.

CONCLUSION

Each dental stem cell population possesses specific characteristics and advantages which will be summarized in this review. Furthermore, the neural characteristics of dental pulp stem cells and their potential role in (peripheral) neural regeneration will be discussed.

Effect of isolation methodology on stem cell properties and multilineage differentiation potential of human dental pulp stem cells

Dental pulp stem cells (DPSCs) are an attractive alternative mesenchymal stem cell (MSC) source because of their isolation simplicity compared with the more invasive methods associated with harvesting other MSC sources. However, the isolation method to be favored for obtaining DPSC cultures remains under discussion. This study compares the stem cell properties and multilineage differentiation potential of DPSCs obtained by the two most widely adapted isolation procedures. DPSCs were isolated either by enzymatic digestion of the pulp tissue (DPSC-EZ) or by the explant method (DPSC-OG), while keeping the culture media constant throughout all experiments and in both isolation methods. Assessment of the stem cell properties of DPSC-EZ and DPSC-OG showed no significant differences between the two groups with regard to proliferation rate and colony formation. Phenotype analysis indicated that DPSC-EZ and DPSC-OG were positive for CD29, CD44, CD90, CD105, CD117 and CD146 expression without any significant differences. The multilineage differentiation potential of both stem cell types was confirmed by using standard immuno(histo/cyto)chemical staining together with an in-depth ultrastructural analysis by means of transmission electron microscopy. Our results indicate that both DPSC-EZ and DPSC-OG could be successfully differentiated into adipogenic, chrondrogenic and osteogenic cell types, although the adipogenic differentiation of both stem cell populations was incomplete. The data suggest that both the enzymatic digestion and outgrowth method can be applied to obtain a suitable autologous DPSC resource for tissue replacement therapies of both bone and cartilage.

Mesenchymal stem or stromal cells from amnion and umbilical cord tissue and their potential for clinical applications

Mesenchymal stem or stromal cells (MSC) have proven to offer great promise for cell-based therapies and tissue engineering applications, as these cells are capable of extensive self-renewal and display a multilineage differentiation potential. Furthermore, MSC were shown to exhibit immunomodulatory properties and display supportive functions through parakrine effects. Besides bone marrow (BM), still today the most common source of MSC, these cells were found to be present in a variety of postnatal and extraembryonic tissues and organs as well as in a large variety of fetal tissues. Over the last decade, the human umbilical cord and human amnion have been found to be a rich and valuable source of MSC that is bio-equivalent to BM-MSC. Since these tissues are discarded after birth, the cells are easily accessible without ethical concerns.

Comparison of different methods for the isolation of mesenchymal stem cells from human umbilical cord Wharton's jelly

Several techniques have been devised for the dissociation of tissues for primary culture. These techniques can affect the quantity and quality of the isolated cells. The aim of our study was to develop the most appropriate method for the isolation of human umbilical cord-derived mesenchymal (hUCM) cells. In the present study, we compared four methods for the isolation of hUCM cells: three enzymatic methods; collagenase/hyaluronidase/trypsin (CHT), collagenase/trypsin (CT) and trypsin (Trp), and an explant culture (Exp) method. The trypan blue dye exclusion test, the water-soluble tetrazolium salt-1 (WST-1) assay, flow cytometry, alkaline phosphatase activity and histochemical staining were used to evaluate the results of the different methods. The hUCM cells were successfully isolated by all methods but the isolation method used profoundly altered the cell number and proliferation capacity of the isolated cells. The cells were successfully differentiated into adipogenic and osteogenic lineages and alkaline phosphatase activity was detected in the hUCM cell colonies of all groups. Flow cytometry analysis revealed that CD44, CD73, CD90 and CD105 were expressed in all groups, while CD34 and CD45 were not expressed. The expression of C-kit in the enzymatic groups was higher than in the explant group, while the expression of Oct-4 was higher in the CT group compared to the other groups. We concluded that the collagenase/trypsin method of cell isolation yields a higher cell density than the others. These cells expressed a higher rate of pluripotent cell markers such as C-kit and Oct-4, while the explant method of cell isolation resulted in a higher cell proliferation rate and activity compared to the other methods.