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.

Translational and Clinical Applications of Dental Stem Cell-Derived Exosomes

Mesenchymal stem cells (MSCs) are promising seed cells in tissue repair and regeneration due to their featured properties of self-renewal and multipotency. However, a growing body of evidence has demonstrated that MSCs exert biological functions mainly through secreting exosomes. Exosomes, which contain RNA, proteins, lipids, and metabolites, are new players in regulating many fundamental processes and play important roles in regenerative medicine. Exosomes not only mimic the effects of their parent cells but also possess many advantages such as high drug loading capacity, low immunogenicity, excellent biocompatibility, and low side effects. Currently, a total of 6 different dental stem cells (DSCs) including dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHEDs), periodontal ligament stem cells (PDLSCs), dental follicle progenitor cells (DFPCs), stem cells from apical papilla (SCAPs) and gingival mesenchymal stem cells (GMSCs) have been isolated and identified. DSC-derived exosomes (DSC-Exos) are actively involved in intercellular communication, anti-inflammation, osteogenesis, angiogenesis, immunomodulation, nurturing neurons, and promoting tumor cell apoptosis. In this review, we will critically review the emerging role and clinical application potential of DSC-Exos.

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.

Evaluation of human dental stem cell growth characteristics and cellular morphological changes in response to extracellular matrix nanotopography

Objective: Nanotopography and soluble extracellular factors are present in the dental stem cell niche in the pulp. Their effect on dental stem cell survival and differentiation is yet to be established. We aimed to analyze the individual and combined roles of extracellular matrix (ECM) nanotopography and serum (soluble factors) on the growth, differentiation potential, and morphological characteristics of the human dental pulp stem cells (hDPSC). This study aimed to evaluate and compare the hDPSC response to different environmental cues – nanofibers, serum, and conditioned media. Materials and methods: In this study, fabricated PLLA nanofibers were used as the in vitro structural biomimetic of the native nanotopography found in the in vivo ECM/stem cell niche. Serum and conditioned media were used as the in vitro mimic of the soluble factors to which stem cells get exposed in vivo. hDPSC were grown in the presence and absence of biodegradablepoly-L-lactic-acid nanofibers and serum. The growth characteristics of hDPSC were assessed in terms of cell viability and doubling time at the interval of every passage. Cellular morphological changes were studied using inverted microscopy and H&E. As the second part of the study, hDPSC in all culture conditions were exposed to Dental Pulp Conditioned Media (DPCM) for a short duration of 3 days. After transient exposure to DPCM, the growth characteristics and the morphological changes of hDPSC were assessed. In addition, scanning electron microscopy was used for the morphological study of hDPSC on nanofibers, exposed to conditioned media. The differentiated cells were analyzed by qRT-PCR for neurogenic and odontogenic expression of RUNX2, osteopontin, and β-tubulin III genes. Results: hDPSC showed better survival and proliferation in the presence of nanofibers and serum. Absence of nanofibers or serum greatly altered stem cell survival and proliferation and also indicated differentiation. In addition, it was observed that after transient exposure to DPCM, the presence of both PLLA nanofiber and serum favoured higher odontogenic and neurogenic differentiation potential, without characteristic morphological changes of terminal differentiation. Conclusion: hDPSC has the ability to sense nanoscale geometric cues from their microenvironment. Nanotopography and soluble factors of the extracellular matrix both affect hDPSC. Further studies are essential to identify the key pathways that play a vital role in such interactions. The hDPSC demonstrated better survival and proliferation in the presence of nanofibers and serum. Absence of nanofibers or serum greatly altered stem cell survival and proliferation and also showed changes indicative of differentiation. The results were compared and analyzed using GraphPad Prism 5 Software. hDPSC possess the ability to sense nanoscale geometric cues from their microenvironment. Nanotopography and soluble factors of the Extracellular matrix together influence the fate of hDPSC. Further studies are essential to identify the key pathways that play a vital role in such interactions.