Secretome Cues Modulate the Neurogenic Potential of Bone Marrow and Dental Stem Cells

Angiogenic and neurogenic potential of dental-derived stem cells for functional pulp regeneration: A narrative review

BACKGROUND

Dental pulp tissue engineering is expected to become an ideal treatment for irreversible pulpitis and apical periodontitis. However, angiogenesis and neurogenesis for functional pulp regeneration have not yet met the standard for large-scale clinical application, and need further research.

OBJECTIVE

This review focused on the potential mechanisms of angiogenesis and neurogenesis in pulp regeneration, including stem cell types, upstream and downstream regulatory molecules and cascade signalling pathways, thereby providing a theoretical basis and inspiring new ideas to improve the effectiveness of dental pulp tissue engineering.

METHODS

An electronic literature search was carried out using the keywords of 'pulp regeneration', 'stem cell transplantation', 'dental pulp stem cells', 'angiogenesis' and 'neurogenesis'. The resulting literature was screened and reviewed.

RESULTS

Stem cells used in dental pulp tissue engineering can be classified as dental-derived and non-dental-derived stem cells, amongst which dental pulp stem cells (DPSC) have achieved promising results in animal experiments and clinical trials. Multiple molecules and signalling pathways are involved in the process of DPSC-mediated angiogenic and neurogenetic regeneration. In order to promote angiogenesis and neurogenesis in pulp regeneration, feasible measures include the addition of growth factors, the modulation of transcription factors and signalling pathways, the use of extracellular vesicles and the modification of bioscaffold materials.

CONCLUSION

Dental pulp tissue engineering has had breakthroughs in preclinical and clinical studies in vivo. Overcoming difficulties in pulpal angiogenesis and neurogenesis, and achieving functional pulp regeneration will lead to a significant impact in endodontics.

Harnessing the Antioxidative Potential of Dental Pulp Stem Cell-Conditioned Medium in Photopolymerized GelMA Hydrogels

Gelatin methacryloyl (GelMA) stands out for its biocompatibility, tunability, and functionality, being often selected as a scaffolding material. However, the biological modulations induced by its photocrosslinking process on mesenchymal stem cells as well as stress mitigation measures remain insufficiently explored. By using GelMA of Good Manufacturing Practice (GMP) grade, this study aimed (a) to achieve a comprehensive understanding of the biological effects of photocrosslinking process with a specific focus on oxidative stress and (b) to develop a strategy to mitigate the adverse effects by employing conditioned medium (CM) by dental pulp stem cells (DPSCs). Following photocrosslinking, pathways related to oxidative phosphorylation and DNA repair were enriched in the presence of DPSC-CM carrying various antioxidants such as peroxiredoxin (PRDX) 1-6 and superoxide dismutase type 1 (SOD1), while the control samples exhibited enrichment in inflammatory signaling pathways. Incorporating DPSC-CM into the hydrogel notably reduced the degree of cellular oxidation caused by photocrosslinking and stress responses, resulting in improved cell viability, growth, motility, and osteogenic differentiation, as well as fewer apoptotic and senescent cells compared to those without DPSC-CM. The deteriorated biocompatibility of freshly crosslinked GelMA hydrogel was confirmed by the disrupted vasculature of chorioallantoic membranes in chicken embryos after implantation, which was prevented by DPSC-CM. In conclusion, this study demonstrates the robust antioxidative effects of DPSC-CM, mitigating the negative effect of GelMA photocrosslinking processes.

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.

Isolation and characterization of rabbit limbal niche cells

Limbal niche cells (LNCs) are one of the most important supporting cells for corneal epithelial stem cells (CES), however, research on LNCs has been mostly limited to humans and rats previously. To expand the research work into the rabbit animal model, one of the most often used animals in stem cell study, this study was carried out for the in vitro isolation and identification of rabbit LNCs. Rabbit LNCs were isolated by collagenase A digestion method and single cells were obtained, the cells were then seeded on 5% Matrigel-coated plastic surface and cultured in modified embryonic stem cell medium (MESCM). Three biological replicates of the isolating and characterization were recorded from New Zealand White rabbits aged from 2.5 months to 5 months. LNC markers (VIM/CD90/CD105/SCF/PDGFRβ) were analyzed using tyramide signal amplification (TSA) staining, immunohistochemical staining (IHC), western blotting (WB), and real-time reverse transcription polymerase chain reaction (qPCR). TSA staining suggested that VIM was highly expressed in rabbit limbus stroma, which was confirmed by WB, and P63α was expressed in the basal limbus epithelium. Pan-CK and CK12 were highly expressed in the central corneal epithelium but lightly expressed in the limbal epithelium. The WB result indicated that PDGFRβ and VIM expressions in rabbit-LNCs P4 were higher than in P1 and P7. In addition, rabbit corneal epithelium highly expressed Paired Box 6 (PAX6) and Epidermal growth factor-like domain 6(EGFL6). For the three repeat experiments, the cell expansion activity of rabbit-LNC was highest at P4. Rabbit-LNCs were passaged from P0 to P7, and the number of cell doublings (NCD) of P4 for the three repeat experiments was 2.816, 2.737, and 2.849. qPCR showed that high mRNA expression levels of VIM, CD90, CD105, SCF, and PDGFRβ in rabbit-LNCs P4. In conclusion, rabbit-LNCs could be successfully isolated by the collagenase A digestion method as used in human tissue. There were similar characteristics between rabbit and human LNCs (VIM+/CD90+/CD105+/SCF+/PAX6+/PDGFRβ+).

Thiol reductive stress activates the hypoxia response pathway

Owing to their capability to disrupt the oxidative protein folding environment in the endoplasmic reticulum (ER), thiol antioxidants, such as dithiothreitol (DTT), are used as ER-specific stressors. We recently showed that thiol antioxidants modulate the methionine-homocysteine cycle by upregulating an S-adenosylmethionine-dependent methyltransferase, rips-1, in Caenorhabditis elegans. However, the changes in cellular physiology induced by thiol stress that modulate the methionine-homocysteine cycle remain uncharacterized. Here, using forward genetic screens in C. elegans, we discover that thiol stress enhances rips-1 expression via the hypoxia response pathway. We demonstrate that thiol stress activates the hypoxia response pathway. The activation of the hypoxia response pathway by thiol stress is conserved in human cells. The hypoxia response pathway enhances thiol toxicity via rips-1 expression and confers protection against thiol toxicity via rips-1-independent mechanisms. Finally, we show that DTT might activate the hypoxia response pathway by producing hydrogen sulfide. Our studies reveal an intriguing interaction between thiol-mediated reductive stress and the hypoxia response pathway and challenge the current model that thiol antioxidant DTT disrupts only the ER milieu in the cell.

Therapeutic Potential of Oral-Derived Mesenchymal Stem Cells in Retinal Repair

The retina has restricted regeneration ability to recover injured cell layer because of reduced production of neurotrophic factors and increased inhibitory molecules against axon regrowth. A diseased retina could be regenerated by repopulating the damaged tissue with functional cell sources like mesenchymal stem cells (MSCs). The cells are able to release neurotrophic factors (NFs) to boost axonal regeneration and cell maintenance. In the current study, we comprehensively explore the potential of various types of stem cells (SCs) from oral cavity as promising therapeutic options in retinal regeneration. The oral MSCs derived from cranial neural crest cells (CNCCs) which explains their broad neural differentiation potential and secret rich NFs. They are comprised of dental pulp SCs (DPSCs), SCs from exfoliated deciduous teeth (SHED), SCs from apical papilla (SCAP), periodontal ligament-derived SCs (PDLSCs), gingival MSCs (GMSCs), and dental follicle SCs (DFSCs). The Oral MSCs are becoming a promising source of cells for cell-free or cell-based therapeutic approach to recover degenerated retinal. These cells have various mechanisms of action in retinal regeneration including cell replacement and the paracrine effect. It was demonstrated that they have more neuroprotective and neurotrophic effects on retinal cells than immediate replacement of injured cells in retina. This could be the reason that their therapeutic effects would be weakened over time. It can be concluded that neuronal and retinal regeneration through these cells is most likely due to their NFs that dramatically suppress oxidative stress, inflammation, and apoptosis. Although, oral MSCs are attractive therapeutic options for retinal injuries, more preclinical and clinical investigations are required.

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.

Nanomaterials Modulating the Fate of Dental-Derived Mesenchymal Stem Cells Involved in Oral Tissue Reconstruction: A Systematic Review

The critical challenges in repairing oral soft and hard tissue defects are infection control and the recovery of functions. Compared to conventional tissue regeneration methods, nano-bioactive materials have become the optimal materials with excellent physicochemical properties and biocompatibility. Dental-derived mesenchymal stem cells (DMSCs) are a particular type of mesenchymal stromal cells (MSCs) with great potential in tissue regeneration and differentiation. This paper presents a review of the application of various nano-bioactive materials for the induction of differentiation of DMSCs in oral and maxillofacial restorations in recent years, outlining the characteristics of DMSCs, detailing the biological regulatory effects of various nano-materials on stem cells and summarizing the material-induced differentiation of DMSCs into multiple types of tissue-induced regeneration strategies. Nanomaterials are different and complementary to each other. These studies are helpful for the development of new nanoscientific research technology and the clinical transformation of tissue reconstruction technology and provide a theoretical basis for the application of nanomaterial-modified dental implants. We extensively searched for papers related to tissue engineering bioactive constructs based on MSCs and nanomaterials in the databases of PubMed, Medline, and Google Scholar, using keywords such as "mesenchymal stem cells", "nanotechnology", "biomaterials", "dentistry" and "tissue regeneration". From 2013 to 2023, we selected approximately 150 articles that align with our philosophy.

Application of Dental Pulp Stem Cells for Bone and Neural Tissue Regeneration in Oral and Maxillofacial Region

In the oral and maxillofacial region, the treatment of severe bone defects, caused by fractures, cancers, congenital abnormalities, etc., remains a great challenge. In addition, neurological disorders are frequently accompanied by these bone defects or the treatments for them. Therefore, novel bone regenerative techniques and methods to repair nerve injury are eagerly sought. Among them, strategies using dental pulp stem cells (DPSCs) are promising options. Human DPSCs can be collected easily from extracted teeth and are now considered a type of mesenchymal stem cell with higher clonogenic and proliferative potential. DPSCs have been getting attention as a cell source for bone and nerve regeneration. In this article, we reviewed the latest studies on osteogenic or neural differentiation of DPSCs as well as bone or neural regeneration methods using DPSCs and discussed the potential of DPSCs for bone and nerve tissue regeneration.

The potential roles of dental pulp stem cells in peripheral nerve regeneration

Peripheral nerve diseases are significantly correlated with severe fractures or trauma and surgeries, leading to poor life quality and impairment of physical and mental health. Human dental pulp stem cells (DPSCs) are neural crest stem cells with a strong multi-directional differentiation potential and proliferation capacity that provide a novel cell source for nerve regeneration. DPSCs are easily extracted from dental pulp tissue of human permanent or deciduous teeth. DPSCs can express neurotrophic and immunomodulatory factors and, subsequently, induce blood vessel formation and nerve regeneration. Therefore, DPSCs yield valuable therapeutic potential in the management of peripheral neuropathies. With the purpose of summarizing the advances in DPSCs and their potential applications in peripheral neuropathies, this article reviews the biological characteristics of DPSCs in association with the mechanisms of peripheral nerve regeneration.

Mesenchymal Stem Cell-Derived Extracellular Vesicles: The Novel Therapeutic Option for Regenerative Dentistry

Dental mesenchymal stem cells (MSCs) are characterized by unlimited self-renewal ability and high multidirectional differentiation potential. Since dental MSCs can be easily isolated and exhibit a high capability to differentiate into odontogenic cells, they are considered as attractive therapeutic agents in regenerative dentistry. Recently, MSC-derived extracellular vesicles (MSC-EVs) have attracted widespread attention as carriers for cell-free therapy due to their potential functions. Many studies have shown that MSC-EVs can mediate microenvironment at tissue damage site, and coordinate the regeneration process. Additionally, MSC-EVs can mediate intercellular communication, thus affecting the phenotypes and functions of recipient cells. In this review, we mainly summarized the types of MSCs that could be potentially applied in regenerative dentistry, the possible molecular cargos of MSC-EVs, and the major effects of MSC-EVs on the therapeutic induction of osteogenic differentiation.

Towards a New Concept of Regenerative Endodontics Based on Mesenchymal Stem Cell-Derived Secretomes Products

The teeth, made up of hard and soft tissues, represent complex functioning structures of the oral cavity, which are frequently affected by processes that cause structural damage that can lead to their loss. Currently, replacement therapy such as endodontics or implants, restore structural defects but do not perform any biological function, such as restoring blood and nerve supplies. In the search for alternatives to regenerate the dental pulp, two alternative regenerative endodontic procedures (REP) have been proposed: (I) cell-free REP (based in revascularization and homing induction to remaining dental pulp stem cells (DPSC) and even stem cells from apical papilla (SCAP) and (II) cell-based REP (with exogenous cell transplantation). Regarding the last topic, we show several limitations with these procedures and therefore, we propose a novel regenerative approach in order to revitalize the pulp and thus restore homeostatic functions to the dentin-pulp complex. Due to their multifactorial biological effects, the use of mesenchymal stem cells (MSC)-derived secretome from non-dental sources could be considered as inducers of DPSC and SCAP to completely regenerate the dental pulp. In partial pulp damage, appropriate stimulate DPSC by MSC-derived secretome could contribute to formation and also to restore the vasculature and nerves of the dental pulp.

Application Prospect and Preliminary Exploration of GelMA in Corneal Stroma Regeneration

Corneal regeneration has become a prominent study area in recent decades. Because the corneal stroma contributes about 90% of the corneal thickness in the corneal structure, corneal stromal regeneration is critical for the treatment of cornea disease. Numerous materials, including deacetylated chitosan, hydrophilic gel, collagen, gelatin methacrylate (GelMA), serine protein, glycerol sebacate, and decellularized extracellular matrix, have been explored for keratocytes regeneration. GelMA is one of the most prominent materials, which is becoming more and more popular because of its outstanding three-dimensional scaffold structure, strong mechanics, good optical transmittance, and biocompatibility. This review discussed recent research on corneal stroma regeneration materials and related GelMA.

Therapeutic potential of dental pulp stem cells and their derivatives: Insights from basic research toward clinical applications

For more than 20 years, researchers have isolated and identified postnatal dental pulp stem cells (DPSCs) from different teeth, including natal teeth, exfoliated deciduous teeth, healthy teeth, and diseased teeth. Their mesenchymal stem cell (MSC)-like immunophenotypic characteristics, high proliferation rate, potential for multidirectional differentiation and biological features were demonstrated to be superior to those of bone marrow MSCs. In addition, several main application forms of DPSCs and their derivatives have been investigated, including stem cell injections, modified stem cells, stem cell sheets and stem cell spheroids. In vitro and in vivo administration of DPSCs and their derivatives exhibited beneficial effects in various disease models of different tissues and organs. Therefore, DPSCs and their derivatives are regarded as excellent candidates for stem cell-based tissue regeneration. In this review, we aim to provide an overview of the potential application of DPSCs and their derivatives in the field of regenerative medicine. We describe the similarities and differences of DPSCs isolated from donors of different ages and health conditions. The methodologies for therapeutic administration of DPSCs and their derivatives are introduced, including single injections and the transplantation of the cells with a support, as cell sheets, or as cell spheroids. We also summarize the underlying mechanisms of the regenerative potential of DPSCs.

A Wnt/β-catenin signaling pathway is involved in early dopaminergic differentiation of trabecular meshwork-derived mesenchymal stem cells

Permanent degeneration and loss of dopaminergic (DA) neurons in substantia nigra is the main cause of Parkinson's disease. Considering the therapeutic application of stem cells in neurodegeneration, we sought to examine the neurogenic differentiation potential of the newly introduced neural crest originated mesenchymal stem cells (MSCs), namely, trabecular meshwork-derived mesenchymal stem cells (TM-MSCs) compared to two other sources of MSCs, adipose tissue-derived stem cells (ADSCs) and bone marrow-derived mesenchymal stem cells (BM-MSCs). The three types of cells were therefore cultured in the presence and absence of a neural induction medium followed by the analysis of their differentiation potentials. Our results showed that TM-MSCs exhibited enhanced neural morphologies as well as higher expressions of MAP2 as the general neuron marker and Nurr-1 as an early DA marker compared to the adipose tissue-derived mesenchymal stem cells (AD-MSCs) and bone marrow-derived stem cells (BMSCs). Also, analysis of Nurr-1 immunostaining showed more intense Nurr-1 stained nuclei in the neurally induced TM-MSCs compared to those in the AD-MSCs, BMSCs, and noninduced control TM-MSCs. To examine if Wnt/beta-catenin pathway drives TM-MSCs towards a DA fate, we treated them with the Wnt agonist (CHIR, 3 μM) and the Wnt antagonist (IWP-2, 3 μM). Our results showed that the expressions of Nurr-1 and MAP2, as well as the Wnt/beta-catenin target genes, c-Myc and Cyclin D1, were significantly increased in the CHIR-treated TM-MSCs, but significantly reduced in those treated with IWP-2. Altogether, we declare first a higher neural potency of TM-MSCs compared to the more commonly used MSCs, BMSCs and ADSCs, and second that Wnt/beta-catenin activation directs the neurally induced TM-MSCs towards a DA fate.

Dental stem cell-conditioned medium for tissue regeneration: Optimization of production and storage

BACKGROUND

Mesenchymal stem cells (MSC) effects on tissue regeneration are mainly mediated by their secreted substances (secretome), inducing their paracrine activity. This Conditioned medium (CM), including soluble factors (proteins, nucleic acids, lipids) and extracellular vesicles is emerging as a potential alternative to cell therapy. However, the manufacturing of CM suffers from variable procedures and protocols leading to varying results between studies. Besides, there is no well-defined optimized procedure targeting specific applications in regenerative medicine.

AIM

To focus on conditioned medium produced from dental MSC (DMSC-CM), we reviewed the current parameters and manufacturing protocols, in order to propose a standardization and optimization of these manufacturing procedures.

METHODS

We have selected all publications investigating the effects of dental MSC secretome in in vitro and in vivo models of tissue regeneration, in accordance with the PRISMA guidelines.

RESULTS

A total of 351 results were identified. And based on the inclusion criteria described above, 118 unique articles were included in the systematic review. DMSC-CM production was considered at three stages: before CM recovery (cell sources for CM), during CM production (culture conditions) and after production (CM treatment).

CONCLUSION

No clear consensus could be recovered as evidence-based methods, but we were able to describe the most commonly used protocols: donors under 30 years of age, dental pulp stem cells and exfoliated deciduous tooth stem cells with cell passage between 1 and 5, at a confluence of 70% to 80%. CM were often collected during 48 h, and stored at -80 °C. It is important to point out that the preconditioning environment had a significant impact on DMSC-CM content and efficiency.

Regenerative therapy for the Cornea

The cornea is the outmost layer of the eye, unique in its transparency and strength. The cornea not only transmits the light essential for vision, also refracts light, giving focus to images. Each of the three layers of the cornea has properties essential for the function of vision. Although the epithelium can often recover from injury quickly by cell division, loss of limbal stem cells can cause severe corneal surface abnormalities leading to corneal blindness. Disruption of the stromal extracellular matrix and loss of cells determining this structure, the keratocytes, leads to corneal opacity. Corneal endothelium is the inner part of the cornea without self-renewal capacity. It is very important to maintain corneal dehydration and transparency. Permanent damage to the corneal stroma or endothelium can be effectively treated by corneal transplantation; however, there are drawbacks to this procedure, including a shortage of donors, the need for continuing treatment to prevent rejection, and limits to the survival of the graft, averaging 10-20 years. There exists a need for new strategies to promote regeneration of the stromal structure and restore vision. This review highlights critical contributions in regenerative medicine with the aim of corneal reconstruction after injury or disease. These approaches include corneal stromal stem cells, corneal limbal stem cells, embryonic stem cells, and other adult stem cells, as well as induced pluripotent stem cells. Stem cell-derived trophic factors in the forms of secretomes or exosomes for corneal regeneration are also discussed. Corneal sensory nerve regeneration promoting corneal transparency is discussed. This article provides description of the up-to-date options for corneal regeneration and presents exciting possible avenues for future studies toward clinical applications for corneal regeneration.

Extrapolating neurogenesis of mesenchymal stem/stromal cells on electroactive and electroconductive scaffolds to dental and oral-derived stem cells

The high neurogenic potential of dental and oral-derived stem cells due to their embryonic neural crest origin, coupled with their ready accessibility and easy isolation from clinical waste, make these ideal cell sources for neuroregeneration therapy. Nevertheless, these cells also have high propensity to differentiate into the osteo-odontogenic lineage. One strategy to enhance neurogenesis of these cells may be to recapitulate the natural physiological electrical microenvironment of neural tissues via electroactive or electroconductive tissue engineering scaffolds. Nevertheless, to date, there had been hardly any such studies on these cells. Most relevant scientific information comes from neurogenesis of other mesenchymal stem/stromal cell lineages (particularly bone marrow and adipose tissue) cultured on electroactive and electroconductive scaffolds, which will therefore be the focus of this review. Although there are larger number of similar studies on neural cell lines (i.e. PC12), neural stem/progenitor cells, and pluripotent stem cells, the scientific data from such studies are much less relevant and less translatable to dental and oral-derived stem cells, which are of the mesenchymal lineage. Much extrapolation work is needed to validate that electroactive and electroconductive scaffolds can indeed promote neurogenesis of dental and oral-derived stem cells, which would thus facilitate clinical applications in neuroregeneration therapy.

Dental stem cell-derived extracellular vesicles as promising therapeutic agents in the treatment of diseases

Dental stem cells (DSCs), an important source of mesenchymal stem cells (MSCs), can be easily obtained by minimally invasive procedures and have been used for the treatment of various diseases. Classic paradigm attributed the mechanism of their therapeutic action to direct cell differentiation after targeted migration, while contemporary insights into indirect paracrine effect opened new avenues for the mystery of their actual low engraftment and differentiation ability in vivo. As critical paracrine effectors, DSC-derived extracellular vesicles (DSC-EVs) are being increasingly linked to the positive effects of DSCs by an evolving body of in vivo studies. Carrying bioactive contents and presenting therapeutic potential in certain diseases, DSC-EVs have been introduced as promising treatments. Here, we systematically review the latest in vivo evidence that supports the therapeutic effects of DSC-EVs with mechanistic studies. In addition, current challenges and future directions for the clinical translation of DSC-EVs are also highlighted to call for more attentions to the (I) distinguishing features of DSC-EVs compared with other types of MSC-EVs, (II) heterogeneity among different subtypes of DSC-derived EVs, (III) action modes of DSC-EVs, (IV) standardization for eligible DSC-EVs and (V) safety guarantee for the clinical application of DSC-EVs. The present review would provide valuable insights into the emerging opportunities of DSC-EVs in future clinical applications.

Dental Mesenchymal Stem Cell Secretome: An Intriguing Approach for Neuroprotection and Neuroregeneration

Mesenchymal stem cells (MSCs) are known for their beneficial effects and regenerative potential. In particular, dental-derived MSCs have the advantage of easier accessibility and a non-invasive isolation method. Moreover, thanks to their neural crest origin, dental MSCs seem to have a more prominent neuroregenerative potential. Indeed, in basal conditions they also express neuronal markers. However, it is now well known that the beneficial actions of MSCs depend, at least in part, on their secretome, referring to all the bioactive molecules released in the conditioned medium (CM) or in extracellular vesicles (EVs). In this review we focus on the applications of the secretome derived from dental MSCs for neuroregeneration and neuroprotection. The secretomes of different dental MSCs have been tested for their effects for neuroregenerative purposes, and the secretomes of dental pulp stem cells and stem cells from human exfoliated deciduous teeth are the most studied. Both the CM and EVs obtained from dental MSCs showed that they are able to promote neurite outgrowth and neuroprotective effects. Interestingly, dental-derived MSC secretome showed stronger neuroregenerative and neuroprotective effects compared to that obtained from other MSC sources. For these reasons, the secretome obtained from dental MSCs may represent a promising approach for neuroprotective treatments.

Identification and characterization of pulmonary mesenchymal stem cells derived from rat fetal lung tissue

Pulmonary mesenchymal stem cells (PMSCs) have great potential in lung tissue repair and regeneration, which have been isolated from some mammalian species, including mice, bovine and pig. However, the isolation, characteristics and differentiation potential of rat PMSCs have not been reported. In this study, we successfully isolated PMSCs from Sprague-Dawley rat fetal lung tissue in vitro for the first time and attempted to evaluate its multilineage differentiation potentials. The cultured PMSCs showed typical spindle-shaped morphology and high proliferative potential, and could be passaged for at least 13 passages and maintained high hereditary stability with more than 93.6 % of cells were diploid (2n = 42) by G-banding analysis. Furthermore, the PMSCs could express mesenchymal markers Sca-1, CD29, CD44, CD73 and CD90, but not hematopoietic markers CD34 and CD45. Besides, the expression of cell markers of AT2 (SFTPC), AT1 (PDPN) and macrophage (CD11b) were also negative. Cell cycle examination revealed majority of the PMSCs were in G0/G1 phase, which are similar with previously reported pig PMSCs. In addition, the PMSCs were multipotent and could differentiated into osteocytes, adipocytes, hepatocytes and neurons in vitro. Together, the present study demonstrated the stemness and multi-differentiation potentials of rat PMSCs, which conferred a potential regenerative cell resource for cell regenerative therapy of lung injury.

Application of dental stem cells in three-dimensional tissue regeneration

Dental stem cells can differentiate into different types of cells. Dental pulp stem cells, stem cells from human exfoliated deciduous teeth, periodontal ligament stem cells, stem cells from apical papilla, and dental follicle progenitor cells are five different types of dental stem cells that have been identified during different stages of tooth development. The availability of dental stem cells from discarded or removed teeth makes them promising candidates for tissue engineering. In recent years, three-dimensional (3D) tissue scaffolds have been used to reconstruct and restore different anatomical defects. With rapid advances in 3D tissue engineering, dental stem cells have been used in the regeneration of 3D engineered tissue. This review presents an overview of different types of dental stem cells used in 3D tissue regeneration, which are currently the most common type of stem cells used to treat human tissue conditions.

Induced Neural Cells from Human Dental Pulp Ameliorate Functional Recovery in a Murine Model of Cerebral Infarction

Human mesenchymal stem cells are a promising cell source for the treatment of stroke. Their primary mechanism of action occurs via neuroprotective effects by trophic factors, anti-inflammatory effects, and immunomodulation. However, the regeneration of damaged neuronal networks by cell transplantation remains challenging. We hypothesized that cells induced to neural lineages would fit the niche, replace the lesion, and be more effective in improving symptoms compared with stem cells themselves. We investigated the characteristics of induced neural cells from human dental pulp tissue and compared the transplantation effects between these induced neural cells and uninduced dental pulp stem cells. Induced neural cells or dental pulp stem cells were intracerebrally transplanted 5 days after cerebral infarction induced by permanent middle cerebral artery occlusion in immunodeficient mice. Effects on functional recovery were also assessed through behavior testing. We used immunohistochemistry and neuron tracing to analyze the differentiation, axonal extension, and connectivity of transplanted cells to the host's neural circuit. Transplantation of induced neural cells from human dental pulp ameliorated functional recovery after cerebral infarction compared with dental pulp stem cells. The induced neural cells comprised both neurons and glia and expressed functional voltage, and they were more related to neurogenesis in terms of transcriptomics. Induced neural cells had a higher viability than did dental pulp stem cells in hypoxic culture. We showed that induced neural cells from dental pulp tissue offer a novel therapeutic approach for recovery after cerebral infarction.

Cell-Based Therapies for Trabecular Meshwork Regeneration to Treat Glaucoma

Glaucoma is clinically characterized by elevated intraocular pressure (IOP) that leads to retinal ganglion cell (RGC) and optic nerve damage, and eventually blindness if left untreated. Even in normal pressure glaucoma patients, a reduction of IOP is currently the only effective way to prevent blindness, by either increasing aqueous humor outflow or decreasing aqueous humor production. The trabecular meshwork (TM) and the adjacent Schlemm’s canal inner wall play a key role in regulating IOP by providing resistance when aqueous humor drains through the tissue. TM dysfunction seen in glaucoma, through reduced cellularity, abnormal extracellular matrix accumulation, and increased stiffness, contributes to elevated IOP, but current therapies do not target the TM tissue. Stem cell transplantation for regeneration and re-functionalization of damaged TM has shown promise in providing a more direct and effective therapy for glaucoma. In this review, we describe the use of different types of stem cells for TM regeneration in glaucoma models, the mechanisms of regeneration, and the potential for glaucoma treatment using autologous stem cell transplantation.

Neural Basis of Dental Pulp Stem Cells and its Potential Application in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. Though significant insights into the molecular-biochemical-cellular-behavioral basis of PD have been understood, there is no appreciable treatment available till date. Current therapies provide symptomatic relief without any influence on the progression of the disease. Stem cell therapy has been vigorously explored to treat PD. In this comprehensive review, we analyze various stem cell candidates for treating PD and discuss the possible mechanisms. We advocate the advantage of using neural crest originated dental pulp stem cells (DPSC) due to their predisposition towards neural differentiation and their potential to regenerate neurons far better than commonly used bone marrow derived mesenchymal stem cells (BM-MSCs). Eventually, we highlight the current challenges in the field and the strategies which may be used for overcoming the impediments.

Dental Pulp-Derived Mesenchymal Stem Cells for Modeling Genetic Disorders

A subpopulation of mesenchymal stem cells, developmentally derived from multipotent neural crest cells that form multiple facial tissues, resides within the dental pulp of human teeth. These stem cells show high proliferative capacity in vitro and are multipotent, including adipogenic, myogenic, osteogenic, chondrogenic, and neurogenic potential. Teeth containing viable cells are harvested via minimally invasive procedures, based on various clinical diagnoses, but then usually discarded as medical waste, indicating the relatively low ethical considerations to reuse these cells for medical applications. Previous studies have demonstrated that stem cells derived from healthy subjects are an excellent source for cell-based medicine, tissue regeneration, and bioengineering. Furthermore, stem cells donated by patients affected by genetic disorders can serve as in vitro models of disease-specific genetic variants, indicating additional applications of these stem cells with high plasticity. This review discusses the benefits, limitations, and perspectives of patient-derived dental pulp stem cells as alternatives that may complement other excellent, yet incomplete stem cell models, such as induced pluripotent stem cells, together with our recent data.

Biological Behavioral Alterations of the Post-neural Differentiated Dental Pulp Stem Cells Through an in situ Microenvironment

Transplantation of undifferentiated dental pulp stem cells (DPSCs) may suffer from tumorigenesis. Neuronal differentiated DPSCs (d-DPSCs) have emerged as an ideal source to treat central nervous system (CNS) disorders. Moreover, different components of culture medium functioned on the characteristics of d-DPSCs in vitro. In this study, d-DPSCs were cultured in three types of medium: Neurobasal^®®-A medium supplemented with 2% B27 (the 2% B27 NM group), Neurobasal^® -A medium supplemented with 2% B27 and 5% FBS (the 2% B27 + 5% FBS NM group), and α-MEM containing 10% FBS (the 10% FBS α-MEM group). We found that d-DPSCs in the 2% B27 + 5% FBS NM group had lower proliferation and reduced expression of transient receptor potential canonical 1 (TRPC1) and CD146, whereas up-regulated Nestin and microtubule-associated protein-2 (MAP-2). Notably, d-DPSCs in the 10% FBS α-MEM group possessed high proliferative capacity, decreased expression of neuron-like markers and partially restored stemness. It was demonstrated that d-DPSCs cultured in the 2% B27 + 5% FBS NM could maintain their neuron-like characteristics. Besides, d-DPSCs cultivated in the 10% FBS α-MEM could partially recover their stem cells properties, indicating that neural differentiation of DPSCs was reversible and could open novel avenues for exploring the pluripotency of DPSCs.

Neural Regenerative Potential of Stem Cells Derived from the Tooth Apical Papilla

The regenerative effects of stem cells derived from dental tissues have been previously investigated. This study assessed the potential of human tooth stem cells from apical papilla (SCAP) on nerve regeneration. The SCAP collected from nine individuals were characterized and polarized by exposure to interferon-γ (IFN-γ). IFN-γ increased kynurenine and interleukin-6 (IL-6) production by SCAP, without affecting the cell viability. IFN-γ-primed SCAP exhibited a decrease of brain-derived neurotrophic factor (BDNF) mRNA levels, followed by an upregulation of glial cell-derived neurotrophic factor mRNA. Ex vivo, the co-culture of SCAP with neurons isolated from the rat dorsal root ganglion induced neurite outgrowth, accompanied by increased BDNF secretion, irrespective of IFN-γ priming. In vivo, the local application of SCAP reduced the mechanical and thermal hypersensitivity in Wistar rats that had been submitted to sciatic chronic constriction injury. The SCAP also reduced the pain scores, according to the evaluation of the Grimace scale, partially restoring the myelin damage and BDNF immunopositivity secondary to nerve lesion. Altogether, our results provide novel evidence about the regenerative effects of human SCAP, indicating their potential to handle nerve injury-related complications.

Two-step induction of trabecular meshwork cells from induced pluripotent stem cells for glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. Reducing intraocular pressure is currently the only effective treatment. Elevated intraocular pressure is associated with increased resistance of the outflow pathway, mainly the trabecular meshwork (TM). Despite great progress in the field, the development of novel and effective treatment for glaucoma is still challenging. In this study, we reported that human induced pluripotent stem cells (iPSCs) can be cultured as colonies and monolayer cells expressing OCT4, alkaline phosphatase, SSEA4 and SSEA1. After induction to neural crest cells (NCCs) positive to NGFR and HNK1, the iPSCs can differentiate into TM cells. The induced iPSC-TM cells expressed TM cell marker CHI3L1, were responsive to dexamethasone treatment with increased expression of myocilin, ANGPTL7, and formed CLANs, comparable to primary TM cells. To the best of our knowledge, this is the first study that induces iPSCs to TM cells through a middle neural crest stage, which ensures a stable NCC pool and ensures the high output of the same TM cells. This system can be used to develop personalized treatments using patient-derived iPSCs, explore high throughput screening of new drugs focusing on TM response for controlling intraocular pressure, and investigate stem cell-based therapy for TM regeneration.

Therapeutic Potential of Dental Pulp Stem Cells and Leukocyte- and Platelet-Rich Fibrin for Osteoarthritis

Osteoarthritis (OA) is a degenerative and inflammatory joint disorder with cartilage loss. Dental pulp stem cells (DPSCs) can undergo chondrogenic differentiation and secrete growth factors associated with tissue repair and immunomodulation. Leukocyte- and platelet-rich fibrin (L-PRF) emerges in regenerative medicine because of its growth factor content and fibrin matrix. This study evaluates the therapeutic application of DPSCs and L-PRF in OA via immunomodulation and cartilage regeneration. Chondrogenic differentiation of DPSCs, with or without L-PRF exudate (ex) and conditioned medium (CM), and of bone marrow-mesenchymal stem cells was compared. These cells showed differential chondrogenesis. L-PRF was unable to increase cartilage-associated components. Immature murine articular chondrocytes (iMACs) were cultured with L-PRF ex, L-PRF CM, or DPSC CM. L-PRF CM had pro-survival and proliferative effects on unstimulated and cytokine-stimulated iMACs. L-PRF CM stimulated the release of IL-6 and PGE2, and increased MMP-13, TIMP-1 and IL-6 mRNA levels in cytokine-stimulated iMACs. DPSC CM increased the survival and proliferation of unstimulated iMACs. In cytokine-stimulated iMACs, DPSC CM increased TIMP-1 gene expression, whereas it inhibited nitrite release in 3D culture. We showed promising effects of DPSCs in an in vitro OA model, as they undergo chondrogenesis in vitro, stimulate the survival of chondrocytes and have immunomodulatory effects.

Intravitreal Injection of Human Retinal Progenitor Cells for Treatment of Retinal Degeneration

Background

Retinal degeneration causes irreversible blindness. Human retinal progenitor cells (hRPCs) have the potential to treat retinal diseases. The vitreous cavity is a relatively immune-privileged site that is suitable for stem cell transplantation in the treatment of retinal diseases. This study aimed to evaluate the therapeutic efficacy and safety of intravitreal injection of hRPCs in retinal degeneration therapy.

Material/Methods

hRPCs were primary-cultured and injected into the vitreous cavity of RCS rats. To determine whether hRPCs formed teratomas in immune-deficient mice, hRPCs at different passages were transplanted into BALB/c-nu mice. The visual function was detected by electroretinography recording. Changes in the outer nuclear layer (ONL) were analyzed by histological testing and cell counting. The protective mechanism was further assessed by cytokine antibody array.

Results

Intravitreal transplantation of hRPCs maintained retinal function and preserved retinal morphology. Importantly, grafted cells in the vitreous cavity were well tolerated, with no adverse effects. Teratoma was not formed in BALB/c-nu mice after hRPCs transplantation. The number of hRPCs-injected eyes and thickness of ONL in the hRPCs-treated group were higher than those in the untreated group and HBSS injection group. The cytokine antibody array revealed that hRPCs expressed GDF-15, PDGF-AA, EGF, and NT-4.

Conclusions

Our findings show that intravitreal injection of hRPCs is effective and safe in protecting photoreceptor cells in RCS rats, but were no longer effective at 12 weeks after transplantation. Moreover, hRPCs released multiple neurotrophic factors that may be involved in treating retinal disease.

Intermittent Administration of Parathyroid Hormone Enhances Odonto/Osteogenic Differentiation of Stem Cells from the Apical Papilla via JNK and P38 MAPK Pathways

Objective

Parathyroid hormone (PTH) is considered to be essential during the tooth development. Stem cells from the apical papilla (SCAPs) are responsible for dentine formation. However, the interaction between PTH and SCAPs remains unclear. This study was aimed at investigating the effects of PTH on odonto/osteogenic differentiation capacity of SCAPs and elucidating the underlying molecular mechanisms. Materials and Methods. Here, SCAPs were isolated and identified in vitro. Effects of PTH on the proliferation of SCAPs were determined by Cell Counting Kit-8 (CCK-8), flow cytometry (FCM), and EdU. Alkaline phosphatase (ALP) activity, alizarin red staining, Western blot, and RT-PCR were carried out to detect the odonto/osteogenic differentiation of PTH-treated SCAPs as well as the participation of the MAPK signaling pathway.

Results

An ALP activity assay determined that 10^-8 mol/L PTH was the optimal concentration for the induction of SCAPs with no significant influence on the proliferation of SCAPs as indicated by CCK-8, FCM, and EdU. The expression of odonto/osteogenic markers was significantly upregulated in mRNA levels and protein levels. Moreover, intermittent treatment of PTH also increased phosphorylation of JNK and P38, and the differentiation was suppressed following the inhibition of JNK and P38 MAPK pathways.

Conclusion

PTH can regulate the odonto/osteogenic differentiation of SCAPs via JNK and P38 MAPK pathways.

An update on human periapical cyst-mesenchymal stem cells and their potential applications in regenerative medicine

The broad clinical applications of Mesenchymal Stem Cells (MSCs) in the regenerative medicine field is attributed to their ability to self-renew and differentiate into multiple cellular lineages. Nowadays, MSCs can be derived from a variety of adult and fetal tissues including bone marrow, adipose tissue, umbilical cord and placenta. The difficulties associated with the isolation of MSCs from certain tissues such as bone marrow promoted the search for alternative tissues which are easily accessible. Oral derived MSCs include dental pulp stem cells (DPSCs), dental follicle progenitor cells (DFPC), and periodontal ligament stem cells (PDLSC). Being abundant and easily accessible, oral derived MSCs represent an interesting alternative MSC type to be employed in regenerative medicine. Human periapical cyst-mesenchymal stem cells (hPCy-MSCs) correspond to a newly discovered and characterized MSC subtype. Interestingly, hPCy-MSCs are collected from periapical cysts, which are a biological waste, without any influence on the other healthy tissues in oral cavity. hPCy-MSCs exhibit cell surface marker profile similar to that of other oral derived MSCs, show high proliferative potency, and possess the potential to differentiate into different cell types such as osteoblasts, adipocytes and neurons-like cells. hPCy-MSCs, therefore, represent a novel promising MSCs type to be applied in regenerative medicine domain. In this review, we will compare the different types of dental derived MSCs, we will highlight the isolation technique, the characteristics, and the therapeutic potential of hPCy-MSCs.

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.

Stem Cells from Human Trabecular Meshwork Hold the Potential to Develop into Ocular and Non-Ocular Lineages After Long-Term Storage

Stem cells from the eye hold a great potential for vision restoration and can also be used for regeneration in other tissues. In this study, we characterized the stem cell properties of Trabecular meshwork stem cells (TMSCs) after long-term cryopreservation (∼8 years). TMSCs derived from four donors were examined for their viability and proliferation, as well as stem cell marker expression. Spheroid formation, colony formation, and multipotency were investigated. We observed that TMSCs were fully viable with variable proliferation ability. They expressed the stem cell markers CD90, CD166, CD105, CD73, OCT4, SSEA4, Notch1, KLF4, ABCG2, Nestin, and HNK1 detected by flow cytometry, quantitative polymerase chain reaction, or immunofluorescent staining. They could form spheroids and colonies after thawing. All TMSCs were able to differentiate into osteocytes, neural cells, and trabecular meshwork (TM) cells, but not adipocytes. Differentiated TM cells responded to dexamethasone treatment with increased expression of myocilin and angiopoietin-like 7 (ANGPTL7). In a nutshell, our study demonstrated that TMSCs retain their stem cell properties after long-term cryopreservation and hence can be an effective cell therapy source for various clinical applications.

Assessment of Post-thaw Quality of Dental Mesenchymal Stromal Cells After Long-Term Cryopreservation by Uncontrolled Freezing

Cryopreservation abilities of dental tissue-derived mesenchymal stromal cells (DMSCs) including dental pulp stem cells (DPSCs) and dental follicle stem cells (DFSC) play an important role in the applications of these cells in clinical settings. In this context, we checked whether storage at - 80 °C in 10% DMSO for a longer period has any adverse effect on the functionality and genetic stability. We carried our studies on DPSC and DFSC samples that were revived after a maximum of 5 years of cryopreservation. We observed that even after long-term uncontrolled freezing at - 80 °C, these cells survived and proliferated efficiently. The assessment was made based on their post-thaw morphology, immunophenotypes, differentiation potential, growth kinetics, and genetic features. These cells retained the expression of stemness markers, differentiation ability and maintained their normal karyotype. Our results indicated no significant morphological or immunophenotypic differences between the cryopreserved DMSCs and the fresh DMSCs. Our study implies that mesenchymal stromal cells derived from the dental tissue origin are very robust and do not require any sophisticated preservation protocols. Thus, these can be an ideal source for research, stem cell banking, as well as successful clinical applications in tissue engineering and cell-based therapeutics. Graphical Abstract Schematic diagram showing the cryopreservation of DMSCs by uncontrolled freezing at -80 c has no adverse effects on their functionality and genetic stability.

Insights into the Effects of the Dental Stem Cell Secretome on Nerve Regeneration: Towards Cell-Free Treatment

Cell-free treatment is emerging as an alternative to cell delivery to promote endogenous regeneration using cell-derived factors. The purpose of this article was to systematically review studies of the effects of the dental stem cell secretome on nerve regeneration. PubMed and Scopus databases were used where searched and related studies were selected. The primary search identified 36 articles with the utilized keywords; however, only 13 articles met the defined inclusion criteria. Eight out of thirteen articles included in vivo and in vitro studies. We classified the dental stem cell-derived secretome with its nerve regeneration potential. All studies demonstrated that dental stem cell-derived factors promote neurotrophic effects that can mechanistically stimulate nerve regeneration in neurodegenerative diseases and nerve injury. This data collection will enable researchers to gather information to create a precise formulation for future prescribed treatments.

Fidelity of long-term cryopreserved adipose-derived stem cells for differentiation into cells of ocular and other lineages

Adipose-Derived Stem Cells (ADSCs) have an important contribution in regenerative medicine ranging from testing stem cell therapy for disease treatment in pre-clinical models to clinical trials. For immediate use of stem cells for therapy, there is a requirement of the high dose of stem cells at different time points which can be met by cryopreservation. In this study, we evaluated the characteristics of long-term cryopreserved ADSCs and their regenerative potential after an average of twelve-year cryopreservation. Revived ADSCs were examined for cell viability and proliferation by trypan blue, Calcein/Hoechst and MTT assay. Expression of stem cell markers was examined by flow cytometry, immunostaining and qPCR. Colony forming efficiency and spheroid formation ability were also assessed. Multilineage differentiation potential was evaluated by induction into osteocytes, adipocytes, neural cells, corneal keratocytes and trabecular meshwork (TM) cells. Post-thaw, ADSCs maintained expression of stem cell markers CD90, CD73, CD105, CD166, NOTCH1, STRO-1, ABCG2, OCT4, KLF4. ADSCs retained colony and spheroid forming potential. These cells were able to differentiate into osteocytes, confirmed by Alizarin Red S staining and elevated expression of osteocalcin and osteopontin; into adipocytes by Oil Red O staining and elevated expression of PPARγ2. ADSCs could differentiate into neural cells, stained positive to β-III tubulin, neurofilament, GFAP as well as elevated expression of nestin and neurofilament mRNAs. ADSCs could also give rise to corneal keratocytes expressing keratocan, keratan sulfate, ALDH and collagen V, and to TM cells expressing CHI3L1 and AQP1. Differentiated TM cells responded to dexamethasone treatment with increased Myocilin expression, which could be used as in vitro glaucoma model for further studies. Conditioned medium from ADSCs was found to impart a regenerative effect on primary TM cells. In conclusion, ADSCs maintained their stemness and multipotency after long-term cryopreservation with variability between different donors. This study can have great repercussions in regenerative medicine and pave the way for future clinical trials using cryopreserved ADSCs.

Stemness and Regenerative Potential of Corneal Stromal Stem Cells and Their Secretome After Long-Term Storage: Implications for Ocular Regeneration

Purpose

To assess the stemness and regenerative potential of cryopreserved corneal stromal stem cells (cryo-CSSCs) after long-term storage. We also used the secretome from these cells to observe the effect on wound-healing capacity of corneal fibroblasts and on the expression of fibrotic markers during wound healing.

Methods

CSSCs were obtained from three donors and stored in liquid nitrogen for approximately 10 years. Post thaw, cryo-CSSCs were characterized for stemness using phenotypic and genotypic markers along with colony-forming efficiency and three-dimensional spheroid formation. Multilineage differentiation was observed by differentiation into osteocytes, adipocytes, neural cells, and keratocytes. Secretome was harvested by culturing cryo-CSSCs in log phase. Wound-healing capacity was observed by live-cell time-lapse microscopy. Statistical analysis was done using 1-way ANOVA and Tukey posttest.

Results

CSSCs displayed good viability post thaw and showed >90% expression of stem cell markers CD90, CD73, CD105, STRO1, and CD166. cryo-CSSCs also expressed stem cell genes OCT4, KLF4, and ABCG2, and could also form colonies and three-dimensional spheroids. Multipotency assessment showed that all three cryo-CSSCs could differentiate into osteocytes, adipocytes, neural cells, as shown by β-III tubulin and neurofilament antibody staining and corneal keratocytes as observed by staining for Kera C, J19, and collagen V antibodies. The secretome derived from these three populations could promote the wound healing of corneal fibroblasts and reduce the expression of fibrotic markers SPARC and fibronectin.

Conclusions

CSSCs maintained their stemness and multipotency after long-term storage, and secretome derived from these cells can be of paramount importance for corneal regeneration and prevention of fibrosis.

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.

Recycle the dental fairy's package: overview of dental pulp stem cells

Adult stem cells are excellent cell resource for cell therapy and regenerative medicine. Dental pulp stem cells (DPSCs) have been discovered and well known in various application. Here, we reviewed the history of dental pulp stem cell study and the detail experimental method including isolation, culture, cryopreservation, and the differentiation strategy to different cell lineage. Moreover, we discussed the future potential application of the combination of tissue engineering and of DPSC differentiation. This review will help the new learner to quickly get into the DPSC filed.

Secretome proteins regulate comparative osteogenic and adipogenic potential in bone marrow and dental stem cells

INTRODUCTION

Dental stem cells (DMSC) have been studied extensively since their early discovery. However, the data regarding osteogenic potential of DMSC with other cell types is sparse and the secretome proteins underlying these differences have not been explored. In this study, we have compared the osteogenic and adipogenic potential of DMSC with Bone Marrow Stem cells (BMSC) and reported the contribution of secretome proteins in controlling their differentiation.

METHODS

Osteogenic potential of these stem cells was compared by mineralization assay, alkaline phosphatase (ALP) assay, immunofluorescence of dentine sialo phosphoprotein (DSPP) & qPCR for osteogenic genes. Adipogenic potential was compared by Oil Red O staining and qPCR for PPAR-γ, leptin & adipsin. Proteomic analysis of secretome was performed by employing WATERS nano Lc-MS/MS system.

RESULTS

We observed a higher osteogenic potential in DMSC, especially dental pulp stem cells (DPSC) as compared to BMSC population but adipogenic potential was found to be better in BMSC as compared to DMSC. Deeper investigations into secretome of these cells by Lc-MS/MS revealed the presence of proteins pertaining to osteogenic and adipogenic lineage. Presence of some important proteins regulating osteogenic (DSPP, BMP7, DDR2, USP9X) and adipogenic differentiation (NCOA2, PEG10, LPA) in secretome of BMSC and DMSC reflected the role of paracrine factors during differentiation.

CONCLUSION

Our study provides first evidence regarding regulation of osteogenic/adipogenic potential by secretome proteins in DMSC and BMSC. DMSC especially DPSC and its secretome show an inherent tendency for higher osteogenic differentiation and lower adipogenic differentiation, these may be potential candidates for effective future therapy in osteoporosis where disturbance of osteocyte/adipocyte homeostasis is reported.

Potential Roles of Dental Pulp Stem Cells in Neural Regeneration and Repair

This review summarizes current advances in dental pulp stem cells (DPSCs) and their potential applications in the nervous diseases. Injured adult mammalian nervous system has a limited regenerative capacity due to an insufficient pool of precursor cells in both central and peripheral nervous systems. Nerve growth is also constrained by inhibitory factors (associated with central myelin) and barrier tissues (glial scarring). Stem cells, possessing the capacity of self-renewal and multicellular differentiation, promise new therapeutic strategies for overcoming these impediments to neural regeneration. Dental pulp stem cells (DPSCs) derive from a cranial neural crest lineage, retain a remarkable potential for neuronal differentiation, and additionally express multiple factors that are suitable for neuronal and axonal regeneration. DPSCs can also express immunomodulatory factors that stimulate formation of blood vessels and enhance regeneration and repair of injured nerve. These unique properties together with their ready accessibility make DPSCs an attractive cell source for tissue engineering in injured and diseased nervous systems. In this review, we interrogate the neuronal differentiation potential as well as the neuroprotective, neurotrophic, angiogenic, and immunomodulatory properties of DPSCs and its application in the injured nervous system. Taken together, DPSCs are an ideal stem cell resource for therapeutic approaches to neural repair and regeneration in nerve diseases.

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.

Adult human periodontal ligament-derived stem cells delay retinal degeneration and maintain retinal function in RCS rats

Background

Retinal degeneration (RD) is a leading cause of irreversible blindness, affecting millions of people worldwide. Stem cell transplantation has been considered a promising therapy for retinal degenerative diseases. This study aimed to investigate the therapeutic potential of human periodontal ligament-derived stem cells (hPDLSCs) for intervention in the progress of this degeneration in the Royal College Surgeons (RCS) rat.

Methods

hPDLSCs were injected into the subretinal space of 3-week-old RCS rats. Control animals received a phosphate-buffered saline injection or were untreated. Retinal function was assessed by electroretinography recording. Eyes were collected afterward for histology and molecular studies.

Results

Retinal function maintenance was observed at 2 weeks and persisted for up to 8 weeks following hPDLSC transplantation. Retinal structure preservation was demonstrated in hPDLSC-transplanted eyes at 4 and 8 weeks following transplantation, as reflected in the preservation of outer nuclear layer thickness and gene expression of Rho, Crx, and Opsin. The percentage of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive apoptotic photoreceptors was significantly lower in the hPDLSC-injected retinas than in those of the control groups. hPDLSCs were also found to express multiple neurotrophic factors, including vascular endothelial growth factor, bioactive basic fibroblast growth factor, brain-derived neurotrophic factor, neurotrophin-3, insulin-like growth factor 1, nerve growth factor, and glial cell line-derived neurotrophic factor.

Conclusions

Our findings suggest that hPDLSC transplantation is effective in delaying photoreceptor loss and provides significant preservation of retinal function in RCS rats. This study supports further exploration of hPDLSCs for treating RD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0731-y) contains supplementary material, which is available to authorized users.

Molecular spectrum of secretome regulates the relative hepatogenic potential of mesenchymal stem cells from bone marrow and dental tissue

Liver regeneration is a spontaneous process that occurs after liver injury, but acute liver failure is a complex and fatal disease which is difficult to treat. Cell-based therapies are promising alternative therapeutic approach for liver failure and different cell sources have been tested in this regard. We investigated the comparative hepatogenic potential of human bone marrow stem cells (BMSC) with stem cells derived from human dental pulp (DPSC), apical papilla (SCAP) and follicle (DFSC) during this study. Hepatogenic potential of stem cells was assessed by functional assays at both genetic and protein level. We observed higher expression of most of the hepatic markers post differentiation in DPSCs compared to other cell types. LC-MS/MS analysis of stem cell secretome revealed the presence of different proteins related to hepatogenic lineage like growth arrest specific protein 6, oncostatin M, hepatocyte growth factor receptor etc. Interactome and Reactome pathway analysis revealed the interaction of DPSC/SCAP secretome proteins and these proteins were found to be associated with various pathways involved in lipid transport and metabolism. To the best of our knowledge, this is the first study regarding detailed investigation of hepatogenic potential of BMSCs v/s DMSCs (DPSC, SCAP & DFSC) along-with secretome characterization.