Dental pulp stem cells derived conditioned medium promotes angiogenesis in hindlimb ischemia

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.

Increasing angiogenic efficacy of conditioned medium using light stimulation of human adipose-derived stem cells

Conditioned medium (CM) contains various therapeutic molecules produced by cells. However, the low concentration of therapeutic molecules in CM is a major challenge for successful tissue regeneration. Here, we aim to develop a CM enriched in angiogenic paracrine factors for the treatment of ischemic diseases. Combining spheroidal culture and light irradiation significantly upregulates the angiogenic factor expression in human adipose-derived stem cells (hADSCs). Spheroids of light-irradiated hADSCs (SR group) show significantly enhanced expression of angiogenic paracrine factors compared with spheroids without light stimulation. Enhanced viability, migration, and angiogenesis are observed in cells treated with CM derived from the SR group. Furthermore, we performed in vivo experiments using a mouse hindlimb ischemia model; the results demonstrate that CM derived from densely cultured spheroids of light-irradiated hADSCs induced increased angiogenesis in vivo. In conclusion, our proposed approach of using light to stimulate stem cells may overcome the major drawbacks of CM-based therapies.

Combining spheroidal culture of human adipose-derived stem cells with light irradiation enhances angiogenic growth factor secretion in conditioned media, which can improve angiogenesis in a mouse hindlimb ischemia model.

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.

Effect of erythropoietin on angiogenic potential of dental pulp cells

Erythropoietin (EPO) is a 34-kDa glycoprotein that possesses the potential for angiogenesis, as well as anti-inflammatory and anti-apoptotic properties. The present study aimed to examine the effect of EPO on the angiogenesis of dental pulp cells (DPCs) and to explore the underlying mechanisms of these effects. It was demonstrated that EPO not only promoted DPCs proliferation but also induced angiogenesis of DPCs in a paracrine fashion. EPO enhanced the angiogenic capacity by stimulating DPCs to secrete a series of angiogenic cytokines. ELISA confirmed that high concentrations of EPO increased the production of MMP-3 and angiopoietin-1 but decreased the secretion of IL-6. Furthermore, EPO activated the ERK1/2 and p38 signaling pathways in DPCs, while inhibition of these pathways diminished the angiogenesis capacity of DPCs. The present study suggested that EPO may have an important role in the repair and regeneration of dental pulp.

An injectable, self-assembled multicellular microsphere with the incorporation of fibroblast-derived extracellular matrix for therapeutic angiogenesis

Decellularized human lung fibroblast-derived matrix (hFDM) has demonstrated its excellent proangiogenic capability. In this study, we propose a self-assembled, injectable multicellular microspheres containing human umbilical vein endothelial cells (HUVECs) and mesenchymal stem cell (MSCs), collagen hydrogel (Col), and hFDM toward therapeutic angiogenesis. Those multicellular microspheres are spontaneously formed by the mixtures of cell and hydrogel after being dropped on the parafilm for several hours. The size of microspheres can be manipulated via adjusting the initial volume of droplets and the culture period. The cells in the microspheres are highly viable. Multicellular microspheres show good capability of cell migration on 2D culture plate and also exhibit active cell sprouting in 3D environment (Col) forming capillary-like structures. We also find that multiple angiogenic-related factors are significantly upregulated with the multicellular microspheres prepared via Col and hFDM (Col/hFDM) than those prepared using Col alone or single cells (harvested from cocultured HUVECs/MSCs in monolayer). For therapeutic efficacy evaluation, three different groups of single cells, Col and Col/hFDM microspheres are injected to a hindlimb ischemic model, respectively, along with PBS injection as a control group. It is notable that Col/hFDM microspheres significantly improve the blood reperfusion and greatly attenuate the fibrosis level of the ischemic regions. In addition, Col/hFDM microspheres show higher cell engraftment level than that of the other groups. The incorporation of transplanted cells with host vasculature is detectable only with the treatment of Col/hFDM. Current results suggest that hFDM plays an important role in the multicellular microspheres for angiogenic cellular functions in vitro as well as in vivo. Taken together, our injectable multicellular microspheres (Col/hFDM) offer a very promising platform for cell delivery and tissue regenerative applications.

Comparison of osteogenic differentiation capacity in mesenchymal stem cells derived from human amniotic membrane (AM), umbilical cord (UC), chorionic membrane (CM), and decidua (DC)

BACKGROUND

Mesenchymal stem cells (MSCs) have been extensively explored as a promising therapeutic agent in the field of bone tissue engineering due to their osteogenic differentiation ability. In this study, the osteogenic differential ability and the effect of fibronectin and laminin on the osteogenic differentiation in four types of MSCs derived from placental tissue are compared to determine the ideal source for bone reconstruction tissue engineering.

RESULTS

The present study examines the osteogenic differentiation levels of four types of MSCs using alizarin red staining and quantifies the calcium levels and alkaline phosphatase (ALP) activity. In addition, this study examines the osteoblast differentiation protein markers osterix, collagen I, osteopontin, and osteocalcin using a Western blot assay. qPCR and EdU labeling assays were employed to identify the kinetics of osteogenic differentiation. Calcium deposit levels, ALP activity, and osteopontin and osteocalcin concentrations were determined to confirm the role of Extracellular matrix (ECM) components role on the osteogenic differentiation of MSCs. The data demonstrated that MSCs isolated from different layers of placenta had different potentials to differentiate into osteogenic cells. Importantly, AM-MSCs and UC-MSCs differentiated into the osteoblast stage more efficiently and quickly than CM-MSCs and DC-MSCs, which was associated with a decrease in their proliferation ability. Among the different types of MSCs, AM-MSCs and UC-MSCs had a higher osteogenic differentiation potential induced by fibronectin due to enhanced phosphorylation during the Akt and ERK pathways.

CONCLUSIONS

Taken together, these results indicate that AM-MSCs and UC-MSCs possess a higher osteogenic potential, and fibronectin can robustly enhance the osteogenic potential of the Akt and ERK pathways.

Mechanisms underlying dental-derived stem cell-mediated neurorestoration in neurodegenerative disorders

BACKGROUND

Neurodegenerative disorders have a complex pathology and are characterized by a progressive loss of neuronal architecture in the brain or spinal cord. Neuroprotective agents have demonstrated promising results at the preclinical stage, but this has not been confirmed at the clinical stage. Thus far, no neuroprotective drug that can prevent neuronal degeneration in patients with neurodegenerative disorders is available.

MAIN BODY

Recent studies have focused on neurorestorative measures, such as cell-based therapy, rather than neuroprotective treatment. The utility of cell-based approaches for the treatment of neurodegenerative disorders has been explored extensively, and the results have been somewhat promising with regard to reversing the outcome. Because of their neural crest origin, ease of harvest, accessibility, ethical suitability, and potential to differentiate into the neurogenic lineage, dental-derived stem cells (DSCs) have become an attractive source for cell-based neurorestoration therapies. In the present review, we summarize the possible use of DSC-based neurorestoration therapy as an alternative treatment for neurodegenerative disorders, with a particular emphasis on the mechanism underlying recovery in neurodegenerative disorders.

CONCLUSION

Transplantation research in neurodegenerative diseases should aim to understand the mechanism providing benefits both at the molecular and functional level. Due to their ease of accessibility, plasticity, and ethical suitability, DSCs hold promise to overcome the existing challenges in the field of neurodegeneration through multiple mechanisms, such as cell replacement, bystander effect, vasculogenesis, synaptogenesis, immunomodulation, and by inhibiting apoptosis.

Exosomes with Highly Angiogenic Potential for Possible Use in Pulp Regeneration

INTRODUCTION

Angiogenesis is critical for pulp regeneration. Exosomes, a key component of paracrine secretion, have emerged as important players in the modulation of angiogenesis. The role of dental pulp cell-derived exosomes (DPC-Exos) in angiogenesis has rarely been reported. The proangiogenic properties of DPC-Exos in human umbilical vein endothelial cells (HUVECs) are investigated in the current study.

METHODS

Exosomes were isolated from dental pulp cell (DPC) culture supernatants by ultracentrifugation and were characterized by transmission electron microscopy, Western blotting, and nanoparticle tracking analysis. Their roles in HUVEC proliferation, proangiogenic factor expression, and tube formation were examined in vitro.

RESULTS

We isolated and characterized exosomes from DPCs and showed that DPC-Exos promoted HUVEC proliferation, proangiogenic factor expression, and tube formation. Furthermore, we found that p38 mitogen-activated protein kinase (MAPK) signaling inhibition enhances DPC-Exos-induced tube formation.

CONCLUSIONS

Taken together, these results suggest that DPC-Exos have vital roles in angiogenesis, and p38 MAPK signaling inhibition enhances tubular morphogenesis.

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.

Extracellular Vesicles in Neurodegenerative Diseases: A Double-Edged Sword

Extracellular vesicles (EVs), a heterogenous group of membrane-bound particles, are virtually secreted by all cells and play important roles in cell-cell communication. Loaded with proteins, mRNAs, non-coding RNAs and membrane lipids from their donor cells, these vesicles participate in normal physiological and pathogenic processes. In addition, these sub-cellular vesicles are implicated in the progression of neurodegenerative disorders. Accumulating evidence suggests that intercellular communication via EVs is responsible for the propagation of key pathogenic proteins involved in the pathogenesis of amyotrophic lateral sclerosis, Parkinson's diseases, Alzheimer's diseases and other neurodegenerative disorders. For therapeutic perspective, EVs present advantage over other synthetic drug delivery systems or cell therapy; ability to cross biological barriers including blood brain barrier (BBB), ability to modulate inflammation and immune responses, stability and longer biodistribution with lack of tumorigenicity. In this review, we summarized the current state of EV research in central nervous system in terms of their values in diagnosis, disease pathology and therapeutic applications.

Enhancing Therapeutic Efficacy and Reducing Cell Dosage in Stem Cell Transplantation Therapy for Ischemic Limb Diseases by Modifying the Cell Injection Site

In conventional stem cell transplantation therapies for ischemic limb diseases, stem cells are generally transplanted into the ischemic region (IR), and most of the transplanted cells undergo hypoxia-mediated cell death. Due to massive cell death, the therapeutic efficacy is reduced and a high dose of stem cells is necessitated for the therapies. In this study, we investigated whether the therapeutic efficacy can be improved and the cell dosage can be reduced in the therapy for limb ischemia simply by modifying the stem cell injection site to a site where cell engraftment is improved and blood vessel sprouting is efficiently stimulated. Human mesenchymal stem cells (hMSCs) cultured under hypoxic condition, which simulates cells transplanted to IR, underwent extensive cell death in vitro. Importantly, cell death was significantly attenuated when hMSCs adhered first under normoxic condition for 24 h and then were exposed to hypoxic condition, which simulates cells transplanted to the border zone (BZ) in the upper thigh and migrated to IR. hMSCs, at doses of 2 × 10(5) or 2 × 10(6) cells, were injected into the IR or BZ of 5-week-old female athymic mice after ischemic hindlimb induction. Compared with human mesenchymal stem cell (hMSC) transplantation to the IR of mouse ischemic limbs, transplantation to the BZ significantly enhanced cell engraftment and paracrine factor secretion, which effectively stimulated vessel sprouting, enhanced blood perfusion in IR, and enabled the cell dosage reduction. Therefore, modification of the stem cell transplantation site would improve the current stem cell therapies for ischemic limb diseases in terms of cell dosage reduction and therapeutic efficacy enhancement.