Pro-angiogenic impact of dental stem cells in vitro and in vivo

Molars to Medicine: A Focused Review on the Pre-Clinical Investigation and Treatment of Secondary Degeneration following Spinal Cord Injury Using Dental Stem Cells

Spinal cord injury (SCI) can result in the permanent loss of mobility, sensation, and autonomic function. Secondary degeneration after SCI both initiates and propagates a hostile microenvironment that is resistant to natural repair mechanisms. Consequently, exogenous stem cells have been investigated as a potential therapy for repairing and recovering damaged cells after SCI and other CNS disorders. This focused review highlights the contributions of mesenchymal (MSCs) and dental stem cells (DSCs) in attenuating various secondary injury sequelae through paracrine and cell-to-cell communication mechanisms following SCI and other types of neurotrauma. These mechanistic events include vascular dysfunction, oxidative stress, excitotoxicity, apoptosis and cell loss, neuroinflammation, and structural deficits. The review of studies that directly compare MSC and DSC capabilities also reveals the superior capabilities of DSC in reducing the effects of secondary injury and promoting a favorable microenvironment conducive to repair and regeneration. This review concludes with a discussion of the current limitations and proposes improvements in the future assessment of stem cell therapy through the reporting of the effects of DSC viability and DSC efficacy in attenuating secondary damage after SCI.

Angiogenic potential in periodontal stem cells from upper and lower jaw: A pilot study

BACKGROUND

Teeth and supporting oral tissues are attractive and accessible sources of stem cells. Periodontal ligament stem cells (PDLSC) are readily isolated from extracted third molars, and exhibit the ability to self-renew and differentiate into multiple mesodermal cell fates. Clinical experience suggests that the exact location of periodontal defects affects the oral bone remodeling and wound healing. Compared to the mandible, the maxilla heals quicker and more efficiently. Angiogenesis is key in tissue regeneration including dental tissues, yet few studies focus on the angiogenic potential of PDLSC, none of which considered the differences between upper and lower jaw PDLSC (u-PDLSC and l-PDLSC, respectively).

METHODS

Here we studied the angiogenic potential of u-PDLSC and l-PDLSC and compared the results to well-established mesenchymal stem cells (MSC). Cells were characterized in terms of surface markers, proliferation, and vascular endothelial growth factor (VEGF) secretion, and angiogenic assays were performed. Newly formed capillaries were stained with CD31, and their expression of platelet endothelial cell adhesion molecule (PECAM-1), angiopoietin 2 (ANGPT2), and vascular endothelial growth factor receptor 1 and 2 (VEGFR-1, VEGFR-2) were measured.

RESULTS

Periodontal stem cells from the upper jaw showed a higher proliferation capacity, secreted more VEGF, and formed capillary networks faster and denser than l-PDLSC. Gene expression of angiogenesis-related genes was significantly higher in u-PDLSC than in l-PDLSC or MSC, given that culture conditions were suitable.

CONCLUSION

The oral cavity is a valuable source of stem cells, particularly PDLSC, which are promising for oral tissue engineering due to their robust growth, lifelong accessibility, low immunogenicity, and strong differentiation potential. Notably, u-PDLSC exhibit higher VEGF secretion and accelerate capillary formation compared to l-PDLSC or MSC. This study suggests a potential molecular mechanism in capillary formation, emphasizing the significance of precise location isolation of PDLSC.

Spatiotemporal expression profiles of c-Mpl mRNA in the tooth germ: Comparative expression dynamics of vascularization-related genes

BACKGROUND

Vascularization is an essential event for both embryonic organ development and tissue repair in adults. During mouse tooth development, endothelial cells migrate into dental papilla during the cap stage, and form blood vessels through angiogenesis. Megakaryocytes and/or platelets, as other hematopoietic cells, express angiogenic molecules and can promote angiogenesis in adult tissues. However, it remains unknown which cells are responsible for attracting and leading blood vessels through the dental papilla during tooth development.

METHODS

Here we analyzed the spatiotemporal expression of c-Mpl mRNA in developing molar teeth of fetal mice. Expression patterns were then compared with those of several markers of hematopoietic cells as well as of angiogenic elements including CD41, erythropoietin receptor, CD34, angiopoietin-1 (Ang-1), Tie-2, and vascular endothelial growth factor receptor2 (VEGFR2) through in situ hybridization or immunohistochemistry.

RESULTS

Cells expressing c-Mpl mRNA was found in several parts of the developing tooth germ, including the peridental mesenchyme, dental papilla, enamel organ, and dental lamina. This expression occurred in a spatiotemporally controlled fashion. CD41-expressing cells were not detected during tooth development. The spatiotemporal expression pattern of c-Mpl mRNA in the dental papilla was similar to that of Ang-1, which preceded invasion of endothelial cells. Eventually, at the early bell stage, the c-Mpl mRNA signal was detected in morphologically differentiating odontoblasts that accumulated in the periphery of the dental papilla along the inner enamel epithelium layer of the future cusp region.

CONCLUSION

During tooth development, several kinds of cells express c-Mpl mRNA in a spatiotemporally controlled fashion, including differentiating odontoblasts. We hypothesize that c-Mpl-expressing cells appearing in the forming dental papilla at the cap stage are odontoblast progenitor cells that migrate to the site of odontoblast differentiation. There they attract vascular endothelial cells into the forming dental papilla and lead cells toward the inner enamel epithelium layer through production of angiogenic molecules (e.g., Ang-1) during migration to the site of differentiation. C-Mpl may regulate apoptosis and/or proliferation of expressing cells in order to execute normal development of the tooth.

Signaling pathways of liver regeneration: Biological mechanisms and implications

The liver possesses a unique regenerative ability to restore its original mass, in this regard, partial hepatectomy (PHx) and partial liver transplantation (PLTx) can be executed smoothly and safely, which has important implications for the treatment of liver disease. Liver regeneration (LR) can be the very complicated procedure that involves multiple cytokines and transcription factors that interact with each other to activate different signaling pathways. Activation of these pathways can drive the LR process, which can be divided into three stages, namely, the initiation, progression, and termination stages. Therefore, it is important to investigate the pathways involved in LR to elucidate the mechanism of LR. This study reviews the latest research on the key signaling pathways in the different stages of LR.

A review of the evidence to support electrical stimulation-induced vascularization in engineered tissue

Tissue engineering presents a promising solution for regenerative medicine and the success depends on the supply of oxygen/nutrients to the cells by rapid vascularization. More and more technologies are being developed to facilitate vascularization of engineered tissues. In this review, we indicated that a regulatory system which influences all angiogenesis associated cells to achieve their desired functional state is ideal for the construction of vascularized engineered tissues in vitro. We presented the evidence that electrical stimulation (ES) enhances the synergistic promotion of co-cultured angiogenesis associated cells and its potential regulatory mechanisms, highlighted the potential advantages of a combination of mesenchymal stem cells (MSCs), endothelial cells (ECs) and ES to achieve tissue vascularization, with particular emphasis on the different biological pathways of ES-regulated ECs. Finally, we proposed the future direction of using ES to reconstruct engineered tissue blood vessels, pointed out the potential advantages and disadvantages of ES application on tissue vascularization.

Angiogenic Potential of Various Oral Cavity-Derived Mesenchymal Stem Cells and Cell-Derived Secretome: A Systematic Review and Meta-Analysis

Recent evidence suggests the immense potential of human mesenchymal stem cell (hMSC) secretome conditioned medium-mediated augmentation of angiogenesis. However, angiogenesis potential varies from source and origin. The hMSCs derived from the oral cavity share an exceptional quality due to their origin from a hypoxic environment. Our systematic review aimed to compare the mesenchymal stem cells (MSCs) derived from various oral cavity sources and cell-derived secretomes, and evaluate their angiogenic potential. A literature search was conducted using PubMed and Scopus from January 2000 to September 2020. Source-wise outcomes were systematically analyzed using in vitro, in vivo, and in ovo studies, emphasizing endothelial cell migration, tube formation, and blood vessel formation. Ninety-four studies were included in the systematic review, out of which 4 studies were subsequently included in the meta-analysis. Prominent growth factors and other bioactive components implicated in improving angiogenesis were included in the respective studies. The findings suggest that oral tissues are a rich source of hMSCs. The meta-analysis revealed a positive correlation between dental pulp-derived MSCs (DPMSCs) and stem cells derived from apical papilla (SCAP) compared to human umbilical cord-derived endothelial cell lines as a control. It shows a statistically significant positive correlation between the co-culture of human umbilical vein endothelial cells (HUVECs) and DPMSCs with tubule length formation and total branching points. Our meta-analysis revealed that oral-derived MSCs (dental pulp stem cells and SCAP) carry a better angiogenic potential in vitro than endothelial cell lines alone. The reviewed literature illustrates that oral cavity-derived MSCs (OC-MSCs) increased angiogenesis. The present literature reveals a dearth of investigations involving sources other than dental pulp. Even though OC-MSCs have revealed more significant potential than other MSCs, more comprehensive, target-oriented interinstitutional prospective studies are warranted to determine whether oral cavity-derived stem cells are the most excellent sources of significant angiogenic potential.

Exosomes derived from stem cells from apical papilla promote angiogenesis via miR-126 under hypoxia

OBJECTIVES

To explore the effect of exosomal miR-126 derived from stem cells from the apical papilla (SCAPs) under hypoxia on human umbilical vein endothelial cell (HUVEC) angiogenesis.

METHODS

miR-126 mimics plasmids were used to upregulate miR-126 in SCAPs. Internalization of PKH26-labeled exosomes was examined by fluorescent microscopy. CCK-8 assay, Transwell assay, scratch assay, tube formation assay, and Matrigel plug assay were performed to detect the effects of exosomes on the angiogenic ability of HUVECs. The luciferase reporter assay and rescue assay were performed to examine the relationship between miR-126 and sprouty-related, EVH1 domain-containing protein 1 (SPRED1). The involvement of SPRED1 and the extracellular signal-regulated kinase (ERK) signaling pathway was evaluated by western blotting.

RESULTS

miR-126 expression was upregulated in SCAPs and in SCAP-derived exosomes under hypoxia. miR-126 expression was increased in HUVECs when cocultured with SCAP-derived exosomes. Induced overexpression of miR-126 in hypoxic SCAPs and secreted exosomes resulted in enhanced angiogenesis both in vitro and in vivo. Western blot analysis revealed that miR-126-mediated SPRED1 downregulation induced activation of ERK signaling.

CONCLUSIONS

Under hypoxic conditions, exosomes derived from SCAPs can promote HUVEC angiogenesis through expression of miR-126, which subsequently suppresses SPRED1 and activates the ERK signaling pathway.

Potential of dental pulp stem cells and their products in promoting peripheral nerve regeneration and their future applications

Peripheral nerve injury (PNI) seriously affects people's quality of life. Stem cell therapy is considered a promising new option for the clinical treatment of PNI. Dental stem cells, particularly dental pulp stem cells (DPSCs), are adult pluripotent stem cells derived from the neuroectoderm. DPSCs have significant potential in the field of neural tissue engineering due to their numerous advantages, such as easy isolation, multidifferentiation potential, low immunogenicity, and low transplant rejection rate. DPSCs are extensively used in tissue engineering and regenerative medicine, including for the treatment of sciatic nerve injury, facial nerve injury, spinal cord injury, and other neurodegenerative diseases. This article reviews research related to DPSCs and their advantages in treating PNI, aiming to summarize the therapeutic potential of DPSCs for PNI and the underlying mechanisms and providing valuable guidance and a foundation for future research.

Direct contact with endothelial cells drives dental pulp stem cells toward smooth muscle cells differentiation via TGF-β1 secretion

AIM

Prevascularization is vital to accelerate functional blood circulation establishment in transplanted engineered tissue constructs. Mesenchymal stem cells (MSCs) or mural cells could promote the survival of implanted endothelial cells (ECs) and enhance the stabilization of newly formed blood vessels. However, the dynamic cell-cell interactions between MSCs, mural cells and ECs in the angiogenic processes remain unclear. This study aimed to explore the interactions of human umbilical vein ECs (HUVECs) and dental pulp stem cells (DPSCs) in an in vitro cell coculture model.

METHODOLOGY

Human umbilical vascular ECs and DPSCs were directly cocultured or indirectly cocultured with transwell inserts in endothelial basal media-2 (EBM-2) supplemented with 5% FBS for 6 days. Expression of SMC-specific markers in DPSCs monoculture and HUVEC+DPSC cocultures was assessed by western blot and immunofluorescence. Activin A and transforming growth factor-beta 1 (TGF-β1) in conditioned media (CM) of HUVECs monoculture (E-CM), DPSCs monoculture (D-CM) and HUVEC+DPSC cocultures (E+D-CM) were analysed by enzyme-linked immunosorbent assay. TGF-β RI kinase inhibitor VI, SB431542, was used to block TGF-β1/ALK5 signalling in DPSCs.

RESULTS

The expression of SMC-specific markers, α-SMA, SM22α and Calponin, were markedly increased in HUVEC+DPSC direct cocultures compared to that in DPSCs monoculture, while no differences were demonstrated between HUVEC+DPSC indirect cocultures and DPSCs monoculture. E+D-CM significantly upregulated the expression of SMC-specific markers in DPSCs compared to E-CM and D-CM. Activin A and TGF-β1 were considerably higher in E+D-CM than that in D-CM, with upregulated Smad2 phosphorylation in HUVEC+DPSC cocultures. Treatment with activin A did not change the expression of SMC-specific markers in DPSCs, while treatment with TGF-β1 significantly enhanced these markers' expression in DPSCs. In addition, blocking TGF-β1/ALK5 signalling inhibited the expression of α-SMA, SM22α and Calponin in DPSCs.

CONCLUSIONS

TGF-β1 was responsible for DPSC differentiation into SMCs in HUVEC+DPSC cocultures, and TGF-β1/ALK5 signalling pathway played a vital role in this process.

Current concepts of microRNA-mediated regulatory mechanisms in human pulp tissue-derived stem cells: a snapshot in the regenerative dentistry

One of the most studied class of non-coding RNAs is microRNAs (miRNAs) which regulate more than 60% of human genes. A network of miRNA gene interactions participates in stem cell self-renewal, proliferation, migration, apoptosis, immunomodulation, and differentiation. Human pulp tissue-derived stem cells (PSCs) are an attractive source of dental mesenchymal stem cells (MSCs) which comprise human dental pulp stem cells (hDPSCs) obtained from the dental pulp of permanent teeth and stem cells isolated from exfoliated deciduous teeth (SHEDs) that would be a therapeutic opportunity in stomatognathic system reconstruction and repair of other damaged tissues. The regenerative capacity of hDPSCs and SHEDs is mediated by osteogenic, odontogenic, myogenic, neurogenic, angiogenic differentiation, and immunomodulatory function. Multi-lineage differentiation of PSCs can be induced or inhibited by the interaction of miRNAs with their target genes. Manipulating the expression of functional miRNAs in PSCs by mimicking miRNAs or inhibiting miRNAs emerged as a therapeutic tool in the clinical translation. However, the effectiveness and safety of miRNA-based therapeutics, besides higher stability, biocompatibility, less off-target effects, and immunologic reactions, have received particular attention. This review aimed to comprehensively overview the molecular mechanisms underlying miRNA-modified PSCs as a futuristic therapeutic option in regenerative dentistry.

Photo-crosslinked GelMA loaded with dental pulp stem cells and VEGF to repair critical-sized soft tissue defects in rats

BACKGROUND

Tissue engineering of skin and mucosa is essential for the esthetic and functional reconstruction of individuals disfigured by trauma, resection surgery, or severe burns while overcoming the limited amount of autograft and donor site morbidity.

PURPOSE

We aimed to determine whether a combination of Gelatin-methacryloyl (GelMA) hydrogel scaffold alone or loaded with either dental pulp stem cells (DPSCs) and/or vascular endothelial growth factor (VEGF) could improve skin wound healing in rats.

MATERIALS AND METHODS

Four 10 mm full-thickness skin defects were created on the dorsum of 15 Sprague-Dawley rats. The wounds were treated with GelMA alone, GelMA+DPSCs, or GelMA+DPSCs+VEGF. Unprotected wounds were used as controls. Animals were euthanized at 1-, 2-, and 4 weeks post-surgery, and the healing wounds were harvested for clinical, histological, and RT-PCR analysis.

RESULTS

No signs of clinical inflammation were observed among all groups. Few and sparse mononuclear inflammatory cells were observed in GelMA+DPSCs and GelMA+DPSCs+VEGF groups at 2 weeks, with complete epithelialization of the wounds. At 4 weeks, the epidermis in GelMA+DPSCs and GelMA+DPSCs+VEGF groups was indistinguishable from the empty defect and GelMA groups. The decrease in cellularity and increase in density of collagen fibers were observed over time in both GelMA+DPSCs and GelMA+DPSCs+VEGF groups but were more evident in the GelMA+DPSCs+VEGF group. The GelMA+DPSCs+VEGF group showed a higher expression of the KER 10 gene at all time points compared with the other groups. Expression of Col1 A1 and TGFβ-1 were not statistically different over time neither among the groups.

CONCLUSION

GelMA scaffolds loaded with DPSCs, and VEGF accelerated the re-epithelialization of skin wounds.

Exosome-Based Cell Homing and Angiogenic Differentiation for Dental Pulp Regeneration

Exosomes have attracted attention due to their ability to promote intercellular communication leading to enhanced cell recruitment, lineage-specific differentiation, and tissue regeneration. The object of this study was to determine the effect of exosomes on cell homing and angiogenic differentiation for pulp regeneration. Exosomes (DPSC-Exos) were isolated from rabbit dental pulp stem cells cultured under a growth (Exo-G) or angiogenic differentiation (Exo-A) condition. The characterization of exosomes was confirmed by nanoparticle tracking analysis and an antibody array. DPSC-Exos significantly promoted cell proliferation and migration when treated with 5 × 10⁸/mL exosomes. In gene expression analysis, DPSC-Exos enhanced the expression of angiogenic markers including vascular endothelial growth factor A (VEGFA), Fms-related tyrosine kinase 1 (FLT1), and platelet and endothelial cell adhesion molecule 1 (PECAM1). Moreover, we identified key exosomal microRNAs in Exo-A for cell homing and angiogenesis. In conclusion, the exosome-based cell homing and angiogenic differentiation strategy has significant therapeutic potential for pulp regeneration.

Poly-ε-caprolactone/poly(rotaxane) seeded with human dental pulp stem cells or osteoblasts promotes angiogenesis: a chorioallantoic membrane assay

Biomaterials used for tissue regeneration should ideally provide a favorable environment for cell proliferation and differentiation. Angiogenesis is crucial for supplying oxygen and nutrients necessary for cellular survival at implantation sites. The aim of this study was to evaluate the overall angiogenesis response of a poly ε-caprolactone/poly (rotaxane) blend (poly-blend) carried by human dental pulp stem cells (hDPSCs) or osteoblasts (OB) seeded in the chorioallantoic membranes (CAM) of fertilized chicken eggs on embryonic day 7. They were classified into the following intervention groups: (a) poly(polymeric blend disks free of cells); (b) hDPSC seeded onto CAM; (c) poly/hDPSC (where hDPSCs were seeded onto poly-blend); (d) poly/OB (where osteoblasts were seeded onto poly); (e) OB (where hDPSCs differentiated into osteoblasts were seeded onto CAM); and (f) a negative control when a sterilized silicone ring free of cells or polymer was inserted into CAM. On embryonic day 14, the quantitative and qualitative characteristics of the blood vessels in the CAMs were analyzed macroscopically and microscopically. Macroscopic examination showed that the Poly/hDPSC samples exhibited an increased medium vessel density. Additionally, microscopic observations showed that the Poly/hDPSC group and poly alone resulted in a large lumen area of vascularization. Thus, poly ε-caprolactone/poly (rotaxane) did not impair angiogenesis. Furthermore, poly-blend carried by stem cells of dental pulp origin shows a better vasculogenic potential, which is essential for regenerative therapies.

Characterization of a Stemness-Optimized Purification Method for Human Dental-Pulp Stem Cells: An Approach to Standardization

Human dental pulp stem cells (hDPSCs) are promising for oral/craniofacial regeneration, but their purification and characterization is not yet standardized. hDPSCs from three donors were purified by magnetic activated cell sorting (MACS)-assisted STRO-1-positive cell enrichment (+), colony derivation (c), or a combination of both (c/+). Immunophenotype, clonogenicity, stemness marker expression, senescence, and proliferation were analyzed. Multilineage differentiation was assessed by qPCR, immunohistochemistry, and extracellular matrix mineralization. To confirm the credibility of the results, repeated measures analysis and post hoc p-value adjustment were applied. All hDPSC fractions expressed STRO-1 and were similar for several surface markers, while their clonogenicity and expression of CD10/44/105/146, and 166 varied with the purification method. (+) cells proliferated significantly faster than (c/+), while (c) showed the highest increase in metabolic activity. Colony formation was most efficient in (+) cells, which also exhibited the lowest cellular senescence. All hDPSCs produced mineralized extracellular matrix. Regarding osteogenic induction, (c/+) revealed a significant increase in mRNA expression of COL5A1 and COL6A1, while osteogenic marker genes were detected at varying levels. (c/+) were the only population missing BDNF gene transcription increase during neurogenic induction. All hDPSCs were able to differentiate into chondrocytes. In summary, the three hDPSCs populations showed differences in phenotype, stemness, proliferation, and differentiation capacity. The data suggest that STRO-1-positive cell enrichment is the optimal choice for hDPSCs purification to maintain hDPSCs stemness. Furthermore, an (immuno) phenotypic characterization is the minimum requirement for quality control in hDPSCs studies.

Replacement in angiogenesis research: Studying mechanisms of blood vessel development by animal-free in vitro, in vivo and in silico approaches

Angiogenesis, the development of new blood vessels from pre-existing ones, is an essential process determining numerous physiological and pathological conditions. Accordingly, there is a high demand for research approaches allowing the investigation of angiogenic mechanisms and the assessment of pro- and anti-angiogenic therapeutics. The present review provides a selective overview and critical discussion of such approaches, which, in line with the 3R principle, all share the common feature that they are not based on animal experiments. They include in vitro assays to study the viability, proliferation, migration, tube formation and sprouting activity of endothelial cells in two- and three-dimensional environments, the degradation of extracellular matrix compounds as well as the impact of hemodynamic forces on blood vessel formation. These assays can be complemented by in vivo analyses of microvascular network formation in the chorioallantoic membrane assay and early stages of zebrafish larvae. In addition, the combination of experimental data and physical laws enables the mathematical modeling of tissue-specific vascularization, blood flow patterns, interstitial fluid flow as well as oxygen, nutrient and drug distribution. All these animal-free approaches markedly contribute to an improved understanding of fundamental biological mechanisms underlying angiogenesis. Hence, they do not only represent essential tools in basic science but also in early stages of drug development. Moreover, their advancement bears the great potential to analyze angiogenesis in all its complexity and, thus, to make animal experiments superfluous in the future.

Stem Cells-Loaded 3D-Printed Scaffolds for the Reconstruction of Alveolar Cleft

The advances in the field of tissue engineering and regenerative medicine have opened new vistas for the repair of alveolar clefts. However, the currently available biomaterials used for the repair of alveolar clefts have poor mechanical properties and biocompatibility, which hinders the treatment outcomes. Here, we aimed to develop 3D printed biomimetic scaffolds that fuses β-tricalcium phosphate (β-TCP) and bone marrow mesenchymal stem cells (BMSCs) for improving the repair of alveolar clefts. The methacrylate gelatin (GelMA) was mixed with β-TCP for the preparation of GelMA/β-TCP hybrid scaffolds via 3D printing platform and chemically cross-linking with UV light. The physicochemical properties of the hydrogel scaffolds were characterized. Moreover, the survival state, proliferation ability, morphological characteristics, and osteogenic induction of BMSCs were examined. The prepared hybrid scaffolds showed good biocompatibility and mechanical properties. BMSCs attached well to the scaffolds and proliferated, survived, differentiated, and stimulated osteogenesis for the reconstruction of alveolar clefts. We expect that use of the prepared hybrid hydrogel scaffold can improve the outcomes of alveolar cleft repair in clinic and expand the application of hybrid hydrogel in tissue engineering repair.

Autologous treatment for ALS with implication for broad neuroprotection

Background

Amyotrophic lateral sclerosis (ALS) is characterized by a progressive loss of motor neurons (MNs), leading to paralysis, respiratory failure and death within 2–5 years of diagnosis. The exact mechanisms of sporadic ALS, which comprises 90% of all cases, remain unknown. In familial ALS, mutations in superoxide dismutase (SOD1) cause 10% of cases.

Methods

ALS patient-derived human-induced pluripotent stem cells (ALS hiPSCs, harboring the SOD1^AV4 mutation), were differentiated to MNs (ALS-MNs). The neuroprotective effects of conditioned medium (CM) of hESCs (H9), wt hiPSCs (WTC-11) and the ALS iPSCs, on MN apoptosis and viability, formation and maintenance of neurites, mitochondrial activity and expression of inflammatory genes, were examined. For in vivo studies, 200 μl of CM from the ALS iPSCs (CS07 and CS053) was injected subcutaneously into the ALS model mice (transgenic for the human SOD1^G93A mutation). Animal agility and strength, muscle innervation and mass, neurological score, onset of paralysis and lifespan of the ALS mice were assayed. After observing significant disease-modifying effects, the CM was characterized biochemically by fractionation, comparative proteomics, and epigenetic screens for the dependence on pluripotency. CM of fibroblasts that were differentiated from the wt hiPSCs lacked any neuroprotective activity and was used as a negative control throughout the studies.

Results

The secretome of PSCs including the ALS patient iPSCs was neuroprotective in the H₂O₂ model. In the model with pathogenic SOD1 mutation, ALS iPSC-CM attenuated all examined hallmarks of ALS pathology, rescued human ALS-MNs from denervation and death, restored mitochondrial health, and reduced the expression of inflammatory genes. The ALS iPSC-CM also improved neuro-muscular health and function, and delayed paralysis and morbidity in ALS mice. Compared side by side, cyclosporine (CsA), a mitochondrial membrane blocker that prevents the leakage of mitochondrial DNA, failed to avert the death of ALS-MNs, although CsA and ALS iPSC-CM equally stabilized MN mitochondria and attenuated inflammatory genes. Biochemical characterization, comparative proteomics, and epigenetic screen all suggested that it was the interactome of several key proteins from different fractions of PSC-CM that delivered the multifaceted neuroprotection.

Conclusions

This work introduces and mechanistically characterizes a new biologic for treating ALS and other complex neurodegenerative diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40035-022-00290-5.

Therapeutic Potential of Dental Pulp Stem Cells According to Different Transplant Types

Stem cells are unspecialised cells capable of perpetual self-renewal, proliferation and differentiation into more specialised daughter cells. They are present in many tissues and organs, including the stomatognathic system. Recently, the great interest of scientists in obtaining stem cells from human teeth is due to their easy availability and a non-invasive procedure of collecting the material. Three key components are required for tissue regeneration: stem cells, appropriate scaffold material and growth factors. Depending on the source of the new tissue or organ, there are several types of transplants. In this review, the following division into four transplant types is applied due to genetic differences between the donor and the recipient: xenotransplantation, allotransplantation, autotransplantation and isotransplantation (however, due to the lack of research, type was not included). In vivo studies have shown that Dental Pulp Stem Cells (DPSCs)can form a dentin-pulp complex, nerves, adipose, bone, cartilage, skin, blood vessels and myocardium, which gives hope for their use in various biomedical areas, such as immunotherapy and regenerative therapy. This review presents the current in vivo research and advances to provide new biological insights and therapeutic possibilities of using DPSCs.

Dental Pulp Stem Cells Derived From Adult Human Third Molar Tooth: A Brief Review

The fields of regenerative medicine and stem cell-based tissue engineering have the potential of treating numerous tissue and organ defects. The use of adult stem cells is of particular interest when it comes to dynamic applications in translational medicine. Recently, dental pulp stem cells (DPSCs) have been traced in third molars of adult humans. DPSCs have been isolated and characterized by several groups. DPSCs have promising characteristics including self-renewal capacity, rapid proliferation, colony formation, multi-lineage differentiation, and pluripotent gene expression profile. Nevertheless, genotypic, and phenotypic heterogeneities have been reported for DPSCs subpopulations which may influence their therapeutic potentials. The underlying causes of DPSCs’ heterogeneity remain poorly understood; however, their heterogeneity emerges as a consequence of an interplay between intrinsic and extrinsic cellular factors. The main objective of the manuscript is to review the current literature related to the human DPSCs derived from the third molar, with a focus on their physiological properties, isolation procedures, culture conditions, self-renewal, proliferation, lineage differentiation capacities and their prospective advances use in pre-clinical and clinical applications.

Novel Molecule Nell-1 Promotes the Angiogenic Differentiation of Dental Pulp Stem Cells

Introduction

This work aimed to reveal the crucial role of Nell-1 in the angiogenic differentiation of human dental pulp stem cells (DPSCs) alone or co-cultured with human umbilical vein endothelial cell (HUVECs) in vitro and whether this molecule is involved in the pulp exposure model in vivo.

Methods

Immunofluorescence was conducted to ascertain the location of Nell-1 on DPSCs, HUVECs, and normal rat dental tissues. RT-PCR, Western blot, and ELISA were performed to observe the expression levels of angiogenic markers and determine the angiogenic differentiation of Nell-1 on DPSCs alone or co-cultured with HUVECs, as well as in vitro tube formation assay. Blood vessel number for all groups was observed and compared using immunohistochemistry by establishing a rat pulp exposure model.

Results

Nell-1 is highly expressed in the nucleus of DPSCs and HUVECs and is co-expressed with angiogenic markers in normal rat pulp tissues. Hence, Nell-1 can promote the angiogenic marker expression in DPSCs alone and co-cultured with other cells and can enhance angiogenesis in vitro as well as in the pulp exposure model.

Conclusion

Nell-1 may play a positive role in the angiogenic differentiation of DPSCs.

Maxillofacial-Derived Mesenchymal Stem Cells: Characteristics and Progress in Tissue Regeneration

Maxillofacial-derived mesenchymal stem cells (MFSCs) are a particular collective type of mesenchymal stem cells (MSCs) that originate from the hard and soft tissue of the maxillofacial region. Recently, many types of MFSCs have been isolated and characterized. MFSCs have the common characteristics of being extremely accessible and amazingly multipotent and thus have become a promising stem cell resource in tissue regeneration. However, different MFSCs can give rise to different cell lineages, have different advantages in clinical use, and regulate the immune and inflammation microenvironment through paracrine mechanisms in different ways. Hence, in this review, we will concentrate on the updated new findings of all types of MFSCs in tissue regeneration and also introduce the recently discovered types of MFSCs. Important issues about proliferation and differentiation in vitro and in vivo, up-to-date clinical application, and paracrine effect of MFSCs in tissue regeneration will also be discussed. Our review may provide a better guide for the clinical use of MFSCs and further direction of research in MFSC regeneration medicine.

Sinking Our Teeth in Getting Dental Stem Cells to Clinics for Bone Regeneration

Dental stem cells have been isolated from the medical waste of various dental tissues. They have been characterized by numerous markers, which are evaluated herein and differentiated into multiple cell types. They can also be used to generate cell lines and iPSCs for long-term in vitro research. Methods for utilizing these stem cells including cellular systems such as organoids or cell sheets, cell-free systems such as exosomes, and scaffold-based approaches with and without drug release concepts are reported in this review and presented with new pictures for clarification. These in vitro applications can be deployed in disease modeling and subsequent pharmaceutical research and also pave the way for tissue regeneration. The main focus herein is on the potential of dental stem cells for hard tissue regeneration, especially bone, by evaluating their potential for osteogenesis and angiogenesis, and the regulation of these two processes by growth factors and environmental stimulators. Current in vitro and in vivo publications show numerous benefits of using dental stem cells for research purposes and hard tissue regeneration. However, only a few clinical trials currently exist. The goal of this review is to pinpoint this imbalance and encourage scientists to pick up this research and proceed one step further to translation.

Methylglyoxal-Dependent Glycative Stress Is Prevented by the Natural Antioxidant Oleuropein in Human Dental Pulp Stem Cells through Nrf2/Glo1 Pathway

Methylglyoxal (MG) is a potent precursor of glycative stress (abnormal accumulation of advanced glycation end products, AGEs), a relevant condition underpinning the etiology of several diseases, including those of the oral cave. At present, synthetic agents able to trap MG are known; however, they have never been approved for clinical use because of their severe side effects. Hence, the search of bioactive natural scavengers remains a sector of strong research interest. Here, we investigated whether and how oleuropein (OP), the major bioactive component of olive leaf, was able to prevent MG-dependent glycative stress in human dental pulp stem cells (DPSCs). The cells were exposed to OP at 50 µM for 24 h prior to the administration of MG at 300 µM for additional 24 h. We found that OP prevented MG-induced glycative stress and DPSCs impairment by restoring the activity of Glyoxalase 1 (Glo1), the major detoxifying enzyme of MG, in a mechanism involving the redox-sensitive transcription factor Nrf2. Our results suggest that OP holds great promise for the development of preventive strategies for MG-derived AGEs-associated oral diseases and open new paths in research concerning additional studies on the protective potential of this secoiridoid.

Regenerative Potential of DPSCs and Revascularization: Direct, Paracrine or Autocrine Effect?

A new source of mesenchymal stem cells has recently been discovered, the so-called dental pulp derived stem cells (DPSCs) which therefore could represent potentially tools for regenerative medicine. DPSC originate from the neural crest and are physiologically involved in dentin homeostasis; moreover, they contribute to bone remodeling and differentiation into several tissues including cartilage, bone, adipose and nervous tissues. DPSCs have also been shown to influence the angiogenesis process, for example through the release of secretory factors or by differentiating into vascular and/or perivascular cells. Angiogenesis, that has a pivotal role in tissue regeneration and repair, is defined as the formation of new vessels from preexisting vessels and is mediated by mutual and reciprocal interactions between endothelial cells and perivascular cells. It is also known that co-cultures of perivascular and endothelial cells (ECs) can form a vascular network in vitro and also in vivo. Since DPSCs seem to have characteristics similar to pericytes, understanding the possible mechanism of interaction between DPSCs and ECs during neo-angiogenesis is dramatically important for the development of advanced clinical application in the field of regeneration.

Safety and Homing of Human Dental Pulp Stromal Cells in Head and Neck Cancer

BACKGROUND

Head and neck cancer (HNC) is one of the most common cancers, associated with a huge mortality and morbidity. In order to improve patient outcomes, more efficient and targeted therapies are essential. Bone marrow-derived mesenchymal stromal cells (BM-MSCs) express tumour homing capacity, which could be exploited to target anti-cancer drug delivery to the tumour region and reduce adverse side-effects. Nevertheless, dental pulp stromal cells (DPSCs), an MSC-like population present in teeth, could offer important clinical benefits because of their easy isolation and superior proliferation compared to BM-MSCs. Therefore, we aimed to elucidate the tumour homing and safe usage of DPSCs to treat HNC.

METHODS

The in vivo survival as well as the effect of intratumourally administered DPSCs on tumour aggressiveness was tested in a HNC xenograft mouse model by using bioluminescence imaging (BLI), (immuno)histology and qRT-PCR. Furthermore, the in vitro and in vivo tumour homing capacity of DPSCs towards a HNC cell line were evaluated by a transwell migration assay and BLI, respectively.

RESULTS

Intratumourally injected DPSCs survived for at least two weeks in the tumour micro-environment and had no significant influence on tumour morphology, growth, angiogenesis and epithelial-to-mesenchymal transition. In addition, DPSCs migrated towards tumour cells in vitro, which could not be confirmed after their in vivo intravenous, intraperitoneal or peritumoural injection under the tested experimental conditions.

CONCLUSIONS

Our research suggests that intratumourally delivered DPSCs might be used as safe factories for the continuous delivery of anti-cancer drugs in HNC. Nevertheless, further optimization as well as efficacy studies are necessary to understand and improve in vivo tumour homing and determine the optimal experimental set-up of stem cell-based cancer therapies, including dosing and timing.

Influence of 2-hydroxyethyl methacrylate (HEMA) exposure on angiogenic differentiation of dental pulp stem cells (DPSCs)

OBJECTIVE

The angiogenic differentiation of dental pulp stem cells (DPSCs) is important for tissue homeostasis and wound healing. In this study the influence of 2-hydroxyethyl methacrylate (HEMA) on angiogenic differentiation was investigated.

METHODS

To evaluate HEMA effects on angiogenic differentiation, DPSCs were cultivated in angiogenic differentiation medium (ADM) in the presence or absence of non-toxic HEMA concentrations (0.1 mM and 0.5 mM). Subsequently, angiogenic differentiation was analyzed on the molecular level by qRT-PCR and protein profiler analyzes of angiogenic markers and flow cytometry of PECAM1. The influence of HEMA on angiogenic phenotypes was analyzed by cell migration and sprouting assays.

RESULTS

Treatment with 0.5 mM HEMA during differentiation can lead to a slight reduction of angiogenic markers on mRNA level. HEMA also seems to slightly reduce the quantity of angiogenic cytokines (not significant). However, these HEMA concentrations have no detectable influence on cell migration, the abundance of PECAM1 and the formation of capillaries. Higher concentrations caused primary cytotoxic effects in angiogenic differentiation experiments conducted for longer periods than 72 h.

SIGNIFICANCE

Non-cytotoxic HEMA concentrations seem to have a minor impact on the expression of angiogenic markers, essentially on the mRNA level, without affecting the angiogenic differentiation process itself on a detectable level.

Angiogenesis in Regenerative Dentistry: Are We Far Enough for Therapy?

Angiogenesis is a broad spread term of high interest in regenerative medicine and tissue engineering including the dental field. In the last two decades, researchers worldwide struggled to find the best ways to accelerate healing, stimulate soft, and hard tissue remodeling. Stem cells, growth factors, pathways, signals, receptors, genetics are just a few words that describe this area in medicine. Dental implants, bone and soft tissue regeneration using autologous grafts, or xenografts, allografts, their integration and acceptance rely on their material properties. However, the host response, through its vascularization, plays a significant role. The present paper aims to analyze and organize the latest information about the available dental stem cells, the types of growth factors with pro-angiogenic effect and the possible therapeutic effect of enhanced angiogenesis in regenerative dentistry.

Dental pulp stem cells stimulate neuronal differentiation of PC12 cells

Dental pulp stem cells (DPSCs) secrete neurotrophic factors which may play an important therapeutic role in neural development, maintenance and repair. To test this hypothesis, DPSCs-conditioned medium (DPSCs-CM) was collected from 72 hours serum-free DPSCs cultures. The impact of DPSCs-derived factors on PC12 survival, growth, migration and differentiation was investigated. PC12 cells were treated with nerve growth factor (NGF), DPSCs-CM or co-cultured with DPSCs using Transwell inserts for 8 days. The number of surviving cells with neurite outgrowths and the length of neurites were measured by image analysis. Immunocytochemical staining was used to evaluate the expression of neuronal markers NeuN, microtubule associated protein 2 (MAP-2) and cytoskeletal marker βIII-tubulin. Gene expression levels of axonal growth-associated protein 43 and synaptic protein Synapsin-I, NeuN, MAP-2 and βIII-tubulin were analysed by quantitative polymerase chain reaction (qRT-PCR). DPSCs-CM was analysed for the neurotrophic factors (NGF, brain-derived neurotrophic factor [BDNF], neurotrophin-3, and glial cell-derived neurotrophic factor [GDNF]) by specific ELISAs. Specific neutralizing antibodies against the detected neurotrophic factors were used to study their exact role on PC12 neuronal survival and neurite outgrowth extension. DPSCs-CM significantly promoted cell survival and induced the neurite outgrowth confirmed by NeuN, MAP-2 and βIII-tubulin immunostaining. Furthermore, DPSCs-CM was significantly more effective in stimulating PC12 neurite outgrowths than live DPSCs/PC12 co-cultures over the time studied. The morphology of induced PC12 cells in DPSCs-CM was similar to NGF positive controls; however, DPSCs-CM stimulation of cell survival was significantly higher than what was seen in NGF-treated cultures. The number of surviving PC12 cells treated with DPSCs-CM was markedly reduced by the addition of anti-GDNF, whilst PC12 neurite outgrowth was significantly attenuated by anti-NGF, anti-GDNF and anti-BDNF antibodies. These findings demonstrated that DPSCs were able to promote PC12 survival and differentiation. DPSCs-derived NGF, BDNF and GDNF were involved in the stimulatory action on neurite outgrowth, whereas GDNF also had a significant role in promoting PC12 survival. DPSCs-derived factors may be harnessed as a cell-free therapy for peripheral nerve repair. All experiments were conducted on dead animals that were not sacrificed for the purpose of the study. All the methods were carried out in accordance with Birmingham University guidelines and regulations and the ethical approval is not needed.

Epigenetic Regulation of Dental Pulp Stem Cell Fate

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs, affects gene expression without modifying the primary DNA sequence and modulates cell fate. Mesenchymal stem cells derived from dental pulp, also called dental pulp stem cells (DPSCs), exhibit multipotent differentiation capacity and can promote various biological processes, including odontogenesis, osteogenesis, angiogenesis, myogenesis, and chondrogenesis. Over the past decades, increased attention has been attracted by the use of DPSCs in the field of regenerative medicine. According to a series of studies, epigenetic regulation is essential for DPSCs to differentiate into specialized cells. In this review, we summarize the mechanisms involved in the epigenetic regulation of the fate of DPSCs.

Dentin-Pulp Tissue Regeneration Approaches in Dentistry: An Overview and Current Trends

Conventional treatment approaches in irreversible pulpitis and apical periodontitis include the disinfection of the pulp space followed by filling with various materials, which is commonly known as the root canal treatment. Disadvantages including the loss of tooth vitality and defense mechanism against carious lesions, susceptibility to fractures, discoloration and microleakage led to the development of regenerative therapies for the dentin pulp-complex. The goal of dentin-pulp tissue regeneration is to reestablish the physiological pulp function such as pulp sensibility, pulp repair capability by mineralization and pulp immunity. Recent dentin-pulp tissue regeneration approaches can be divided into cell homing and cell transplantation. Cell based approaches include a suitable scaffold for the delivery of potent stem cells with or without bioactive molecules into the root canal system while cell homing is based on the recruitment of host endogenous stem cells from the resident tissue including periapical region or dental pulp. This review discusses the recent treatment modalities in dentin-pulp tissue regeneration through tissue engineering and current challenges and trends in this field of research.

Therapeutic Functions of Stem Cells from Oral Cavity: An Update

Adult stem cells have been developed as therapeutics for tissue regeneration and immune regulation due to their self-renewing, differentiating, and paracrine functions. Recently, a variety of adult stem cells from the oral cavity have been discovered, and these dental stem cells mostly exhibit the characteristics of mesenchymal stem cells (MSCs). Dental MSCs can be applied for the replacement of dental and oral tissues against various tissue-damaging conditions including dental caries, periodontitis, and oral cancers, as well as for systemic regulation of excessive inflammation in immune disorders, such as autoimmune diseases and hypersensitivity. Therefore, in this review, we summarized and updated the types of dental stem cells and their functions to exert therapeutic efficacy against diseases.

Chorioallantoic Membrane Assay as Model for Angiogenesis in Tissue Engineering: Focus on Stem Cells

Tissue engineering aims to structurally and functionally regenerate damaged tissues, which requires the formation of new blood vessels that supply oxygen and nutrients by the process of angiogenesis. Stem cells are a promising tool in regenerative medicine due to their combined differentiation and paracrine angiogenic capacities. The study of their proangiogenic properties and associated potential for tissue regeneration requires complex in vivo models comprising all steps of the angiogenic process. The highly vascularized extraembryonic chorioallantoic membrane (CAM) of fertilized chicken eggs offers a simple, easy accessible, and cheap angiogenic screening tool compared to other animal models. Although the CAM assay was initially primarily performed for evaluation of tumor growth and metastasis, stem cell studies using this model are increasing. In this review, a detailed summary of angiogenic observations of different mesenchymal, cardiac, and endothelial stem cell types and derivatives in the CAM model is presented. Moreover, we focus on the variation in experimental setup, including the benefits and limitations of in ovo and ex ovo protocols, diverse biological and synthetic scaffolds, imaging techniques, and outcome measures of neovascularization. Finally, advantages and disadvantages of the CAM assay as a model for angiogenesis in tissue engineering in comparison with alternative in vivo animal models are described. Impact statement The chorioallantoic membrane (CAM) assay is an easy and cheap screening tool for the angiogenic properties of stem cells and their associated potential in the tissue engineering field. This review offers an overview of all published angiogenic studies of stem cells using this model, with emphasis on the variation in used experimental timeline, culture protocol (in ovo vs. ex ovo), stem cell type (derivatives), scaffolds, and outcome measures of vascularization. The purpose of this overview is to aid tissue engineering researchers to determine the ideal CAM experimental setup based on their specific study goals.

Dental pulp stem cells from human teeth with deep caries displayed an enhanced angiogenesis potential in vitro

Background/purpose

Dental pulp stem cells can be isolated from human teeth with deep caries (cDPSCs), but their biological characteristics are still unclear. The aim of this study was to investigate the angiogenic potential of cDPSCs and compare them to dental pulp stem cells from human normal teeth (nDPSCs).

Materials and methods

Cells were isolated from human pulp tissue of normal and infected teeth with deep caries. Basic mesenchymal stem cell (MSC) characterization was conducted. Colony forming units and proliferation ability were evaluated in nDPSCs and cDPSCs. Expression of VEGF in both tissues and cells was examined by immunohistochemical staining. After stimulating nDPSCs and cDPSCs with an angiogenic medium, angiogenic markers were evaluated by qRT-PCR and western blotting. Finally, tube formation assays were used to evaluate the in vitro angiogenesis potential of both cell populations.

Results

Both nDPSCs and cDPSCs possessed typical MSC characteristics. cDPSCs had enhanced colony formation and proliferation capacities than nDPSCs did. The expression of VEGF was higher in pulp tissue from teeth with deep caries and cDPSCs than in normal tissue and nDPSCs. When both cell types were grown in vitro under angiogenic conditions, cDPSCs expressed a higher level of angiogenic markers and showed a stronger angiogenesis potential than nDPSCs did.

Conclusion

cDPSCs maintained MSC traits and presented a higher angiogenesis potential than nDPSCs.

The proangiogenic effects of extracellular vesicles secreted by dental pulp stem cells derived from periodontally compromised teeth

Background

Although dental pulp stem cells (DPSCs) isolated from periodontally compromised teeth (P-DPSCs) have been demonstrated to retain pluripotency and regenerative potential, their use as therapeutics remains largely unexplored. In this study, we investigated the proangiogenic effects of extracellular vesicles (EVs) secreted by P-DPSCs using in vitro and in vivo testing models.

Methods

Patient-matched DPSCs derived from periodontally healthy teeth (H-DPSCs) were used as the control for P-DPSCs. Conditioned media (CMs) derived from H-DPSCs and P-DPSCs (H-CM and P-CM), CMs derived from both cell types pretreated with the EV secretion blocker GW4869 (H-GW and P-GW), and EVs secreted by H-DPSCs and P-DPSCs (H-EVs and P-EVs) were prepared to test their proangiogenic effects on endothelial cells (ECs). Cell proliferation, migration, and tube formation were assessed using the Cell Counting Kit-8 (CCK-8), transwell/scratch wound healing, and Matrigel assays, respectively. Specifically, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and western blot analysis were used to examine the expression levels of angiogenesis-related genes/proteins in ECs in response to EV-based incubation. Finally, a full-thickness skin defect model was applied to test the effects of EVs on wound healing and new vessel formation.

Results

Both H-CM and P-CM promoted EC angiogenesis, but the proangiogenic effects were compromised when ECs were incubated in H-GW and P-GW, wherein the EV secretion was blocked by pretreatment with GW4869. In EV-based incubations, although both H-EVs and P-EVs were found to enhance the angiogenesis-related activities of ECs, P-EVs exerted a more robust potential to stimulate EC proliferation, migration, and tube formation. In addition, P-EVs led to higher expression levels of angiogenesis-related genes/proteins in ECs than H-EVs. Similarly, both P-EVs and H-EVs were found to accelerate wound healing and promote vascularization across skin defects in mice, but wounds treated with P-EVs resulted in a quicker healing outcome and enhanced new vessel formation.

Conclusions

The findings of the present study provide additional evidence that P-DPSCs derived from periodontally diseased teeth represent a potential source of cells for research and therapeutic use. Particularly, the proangiogenic effects of P-EVs suggest that P-DPSCs may be used to promote new vessel formation in cellular therapy and regenerative medicine.

Dental Stem Cell-Derived Secretome/Conditioned Medium: The Future for Regenerative Therapeutic Applications

Regenerative medicine literature has proposed mesenchymal stem/progenitor cell- (MSC-) mediated therapeutic approaches for their great potential in managing various diseases and tissue defects. Dental MSCs represent promising alternatives to nondental MSCs, owing to their ease of harvesting with minimally invasive procedures. Their mechanism of action has been attributed to their cell-to-cell contacts as well as to the paracrine effect of their secreted factors, namely, secretome. In this context, dental MSC-derived secretome/conditioned medium could represent a unique cell-free regenerative and therapeutic approach, with fascinating advantages over parent cells. This article reviews the application of different populations of dental MSC secretome/conditioned medium in in vitro and in vivo animal models, highlights their significant implementation in treating different tissue' diseases, and clarifies the significant bioactive molecules involved in their regenerative potential. The analysis of these recent studies clearly indicate that dental MSCs' secretome/conditioned medium could be effective in treating neural injuries, for dental tissue regeneration, in repairing bone defects, and in managing cardiovascular diseases, diabetes mellitus, hepatic regeneration, and skin injuries, through regulating anti-inflammatory, antiapoptotic, angiogenic, osteogenic, and neurogenic mediators.

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.

Evaluation of growth, stemness, and angiogenic properties of dental pulp stem cells cultured in cGMP xeno-/serum-free medium

This study was aimed to investigate the effects of cGMP xeno-/serum-free medium (XSF, Irvine Scientific) on the properties of human dental pulp stem cells (DPSCs). DPSCs, from passage 2, were cultured in XSF or fetal bovine serum (FBS)-supplemented medium, and sub-cultured up to passage 8. Cumulative population doublings (PDs) and the number of colony-forming-units (CFUs) were determined. qRT-PCR, ELISA, and in vitro assays were used to assess angiogenic capacity. Flow cytometry was used to measure CD73, CD90, and CD105 expression. Differentiation into osteo-, adipo-, and chondrogenic cell lineages was performed. DPSCs showed more elongated morphology, a reduced rate of proliferation at later passages, and lower CFU counts in XSF compared with FBS. Expression of angiogenic factors at the gene and protein levels varied in the two media and with passage number, but cells grown in XSF had more in vitro angiogenic activity. The majority of early and late passage DPSCs cultured in XSF expressed CD73 and CD90. In contrast, the percentage of CD105 positive DPSCs in XSF medium was significantly lower with increased passage whereas the majority of cells cultured in FBS were CD105 positive. Switching XSF-cultured DPSCs to medium supplemented with human serum restored the expression of CD105. The tri-lineage differentiation of DPSCs cultured under XSF and FBS conditions was similar. We showed that despite reduced CD105 expression levels, DPSCs expanded in XSF medium maintained a functional MSC phenotype. Furthermore, restoration of CD105 expression is likely to occur upon in vivo transplantation, when cells are exposed to human serum.

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.

MiR-141-3p regulates proliferation and senescence of stem cells from apical papilla by targeting YAP

Biological phenotypes of mesenchymal stem cells (MSCs) are regulated by a series of biochemical elements, including microRNAs, hormones and growth factors. Our previous study illustrated a significant role of miR-141-3p during the osteogenic differentiation of stem cells from apical papilla (SCAPs). Nevertheless, the functions of miR-141-3p in regulating the proliferative ability and senescence of SCAPs have not been determined. This study identified that overexpression of miR-141-3p inhibited the proliferative ability of SCAPs. Meanwhile, the senescence of SCAPs was ahead of time. Conversely, transfection of miR-141-3p inhibitor promoted the proliferative ability of SCAPs and delayed their senescence. Yes-associated protein (YAP) was predicted as the downstream target gene of miR-141-3p by online softwares (miRDB, miRTarBase, miRWalk, and TargetScan), and was further verified by dual-luciferase reporter gene assay. Additionally, knockdown of YAP inhibited the proliferation and accelerated the senescence of SCAPs. Collectively, these findings proposed a novel direction that miR-141-3p impeded proliferative ability and promoted senescence of SCAPs through post-transcriptionally downregulating YAP.

Comparative characterization of mesenchymal stem cells from human dental pulp and adipose tissue for bone regeneration potential

Bone tissue engineering is an area of regenerative medicine that attempts to repair bone defects. Seed cells such as dental pulp stem cells (DPSCs) and adipose tissue-derived stem cells (ADSCs) are two of the most well-characterized cells for bone regeneration because their use involves few ethical constraints and they have the ability to differentiate into multiple cell types, secreting growth factors and depositing mineral. However, bone regeneration ability of these cells remains unclear. This study aimed to compare the bone formation capacity of DPSCs and ADSCs in vitro and in vivo. Studies revealed that DPSCs had enhanced colony-forming ability, higher proliferative ability, stronger migration ability and higher expression of angiogenesis-related genes. They also secreted more vascular endothelial growth factor compared to ADSCs. In contrast, ADSCs grew more slowly compared to DPSCs but exhibited greater osteogenic differentiation potential, higher expression of osteoblast marker genes, and greater mineral deposition. Furthermore, after DPSCs and ADSCs were implanted into a mandibular defect of a rat for 6 weeks, ADSCs showed visible bone tissue as early as week 1 and promoted faster and greater bone regeneration compared to the DPSC group. These results suggest that ADSCs might be more useful than DPSCs for bone regeneration.

In situ prevascularization designed by laser-assisted bioprinting: effect on bone regeneration

Vascularization plays a crucial role in bone formation and regeneration process. Development of a functional vasculature to improve survival and integration of tissue-engineered bone substitutes remains a major challenge. Biofabrication technologies, such as bioprinting, have been introduced as promising alternatives to overcome issues related to lack of prevascularization and poor organization of vascular networks within the bone substitutes. In this context, this study aimed at organizing endothelial cells in situ, in a mouse calvaria bone defect, to generate a prevascularization with a defined architecture, and promote in vivo bone regeneration. Laser-assisted bioprinting (LAB) was used to pattern Red Fluorescent Protein-labeled endothelial cells into a mouse calvaria bone defect of critical size, filled with collagen containing mesenchymal stem cells and vascular endothelial growth factor. LAB technology allowed safe and controlled in vivo printing of different cell patterns. In situ printing of endothelial cells gave rise to organized microvascular networks into bone defects. At two months, vascularization rate (vr) and bone regeneration rate (br) showed statistically significant differences between the 'random seeding' condition and both 'disc' pattern (vr = +203.6%; br = +294.1%) and 'crossed circle' pattern (vr = +355%; br = +602.1%). These results indicate that in vivo LAB is a valuable tool to introduce in situ prevascularization with a defined configuration and promote bone regeneration.

Angiogenic properties of dental pulp stem cells conditioned medium on endothelial cells in vitro and in rodent orthotopic dental pulp regeneration

Objectives

To evaluate the effect of SHED-CM on the proliferation, differentiation, migration ability, cell death, gene expression and production of VEGF of HUVEC in vitro and in a rodent orthotopic dental pulp regeneration.

Methods

Three culture media [M199, DMEM/Ham's F12 and DMEM/Ham's F12 conditioned by SHEDs] were used as experimental groups. SHED-CM was prepared maintaining confluent cells in culture without serum for 3 days. The proliferation and cell death marker of HUVECs were assessed using flow cytometry. The capacity of formation of vascular-like structures was analyzed in cells grown over Matrigel^® in hypoxic condition. HUVECs migration was followed using the scratch test. VEGF-A expression in HUVECs was assessed using real time RT-qPCR; and VEGF synthesis with ELISA test. SHED-CM was also applied in rodent ortotopic model of dental pulp regeneration in rats. The formed tissue was submitted to histological and immunohistochemical analyses.

Results

SHED-CM promoted significantly lower expression of 7AAD in HUVECs; whereas the expression of the Ki67 was similar in all groups. The vascular-like structures were observed in all groups. Migration of SHED-CM group was faster than DMEM/Ham's F12. SHED-CM induced similar expression of VEGF-A than M199, and higher than DMEM/Ham's F12. SHED-CM induced significantly higher VEGF synthesis than other media. SHED-CM induced formation of a vascularized connective tissue inside the root canal.

Conclusion

The study showed that SHEDs release angiogenic and cytoprotective factors, which are of great importance for tissue engineering.

Clinical significance

SHED-CM could be an option to the use of stem cells in tissue engineering.

Stem Cells from the Apical Papilla: A Promising Source for Stem Cell-Based Therapy

Stem cells are biological cells that can self-renew and can differentiate into multiple cell lineages. Stem cell-based therapy is emerging as a promising alternative therapeutic option for various disorders. Mesenchymal stem cells (MSCs) are multipotent adult stem cells that are isolated from various tissues and can be used as an alternative to embryonic stem cells. Stem cells from the apical papilla (SCAPs) are a novel population of MSCs residing in the apical papilla of immature permanent teeth. SCAPs present the characteristics of expression of MSCs markers, self-renewal, proliferation, migration, differentiation, and immunosuppression, which support the application of SCAPs in stem cell-based therapy, including the immunotherapy and the regeneration of dental tissues, bone, neural, and vascular tissues. In view of these properties and therapeutic potential, SCAPs can be considered as promising candidates for stem cell-based therapy. Thus the aim of our review was to summarize the current knowledge of SCAPs considering isolation, characterization, and multilineage differentiation. The prospects for their use in stem cell-based therapy were also discussed.

Early angiogenesis detected by PET imaging with 64Cu-NODAGA-RGD is predictive of bone critical defect repair

Therapies using stem cells may be applicable to all fields of regenerative medicine, including craniomaxillofacial surgery. Dental pulp stem cells (DPSCs) have demonstrated in vitro and in vivo osteogenic and proangiogenic properties. The aim of the study was to evaluate whether early angiogenesis investigated by nuclear imaging can predict bone formation within a mouse critical bone defect. Two symmetrical calvarial critical-sized defects were created. Defects were left empty or filled with i) DPSC-containing dense collagen scaffold, ii) 5% hypoxia-primed DPSC-containing dense collagen scaffold, iii) acellular dense collagen scaffold, or iv) left empty. Early angiogenesis assessed by PET using ⁶⁴Cu-NODAGA-RGD as a tracer was found to be correlated with bone formation determined by micro-CT within the defects from day 30, and to be correlated to the late calcium apposition observed at day 90 using ¹⁸F-Na PET. These results suggest that nuclear imaging of angiogenesis, a technique applicable in clinical practice, is a promising approach for early prediction of bone grafting outcome, thus potentially allowing to anticipate alternative regenerative strategies. STATEMENT OF SIGNIFICANCE: Bone defects are a major concern in medicine. As life expectancy increases, the number of bone lesions grows, and occurring complications lead to a delay or even lack of consolidation. Therefore, to be able to predict healing or the absence of scarring at early times would be very interesting. This would not "waste time" for the patient. We report here that early nuclear imaging of angiogenesis, using ⁶⁴Cu-NODAGA-RGD as a tracer, associated with nuclear imaging of mineralization, using ¹⁸F-Na as a tracer, is correlated to late bone healing objectivized by classical histology and microtomography. This nuclear imaging represents a promising approach for early prediction of bone grafting outcome in clinical practice, thus potentially allowing to anticipate alternative regenerative strategies.

Impaired angiogenic differentiation of dental pulp stem cells during exposure to the resinous monomer triethylene glycol dimethacrylate

OBJECTIVE

Dental pulp stem cells (DPSCs) can differentiate into tissue specific lineages to support dental pulp regeneration after injuries. Triethylene glycol dimethacrylate (TEGDMA) is a widely used co-monomer in restorative dentistry with adverse effects on cellular metabolism. Aim of this study was to analyze the impact of TEGDMA on the angiogenic differentiation potential of DPSCs.

METHODS

DPSCs were characterized by flow cytometry. Short-term (max. 72h) cytotoxicity of TEGDMA was assessed by MTT assay. To evaluate TEGDMA effects on angiogenic differentiation, DPSCs were cultivated in angiogenic differentiation medium (ADM) in the presence or absence of short-term non-toxic TEGDMA concentrations (0.1mM and 0.25mM). Subsequently, angiogenic differentiation was analyzed by qRT-PCR analysis of mRNA markers and in vitro spheroid sprouting assays.

RESULTS

DPSCs treated with 0.25mM TEGDMA revealed downregulation of angiogenesis-related marker genes PECAM1 (max. 3.8-fold), VEGF-A (max. 2.4-fold) and FLT1 (max. 2.9-fold) compared to respective untreated control. In addition, a reduction of the sprouting potential of DPSCs cultured in the presence of 0.25mM TEGDMA was detectable. Larger spheroidal structures were detectable in the untreated control in comparison to cells treated with 0.25mM TEGDMA. In contrast, TEGDMA at 0.1mM was not affecting angiogenic potential in the investigated time period (up to 28 days).

SIGNIFICANCE

The results of the present study show that TEGDMA concentration dependently impair the angiogenic differentiation potential of DPSCs and may affect wound healing and the formation of granulation tissue.