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

Therapeutic Functions of Stem Cells from Oral Cavity: An Update

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

Extracellular Vesicles-Loaded Fibrin Gel Supports Rapid Neovascularization for Dental Pulp Regeneration

Rapid vascularization is required for the regeneration of dental pulp due to the spatially restricted tooth environment. Extracellular vesicles (EVs) released from mesenchymal stromal cells show potent proangiogenic effects. Since EVs suffer from rapid clearance and low accumulation in target tissues, an injectable delivery system capable of maintaining a therapeutic dose of EVs over a longer period would be desirable. We fabricated an EV-fibrin gel composite as an in situ forming delivery system. EVs were isolated from dental pulp stem cells (DPSCs). Their effects on cell proliferation and migration were monitored in monolayers and hydrogels. Thereafter, endothelial cells and DPSCs were co-cultured in EV-fibrin gels and angiogenesis as well as collagen deposition were analyzed by two-photon laser microscopy. Our results showed that EVs enhanced cell growth and migration in 2D and 3D cultures. EV-fibrin gels facilitated vascular-like structure formation in less than seven days by increasing the release of VEGF. The EV-fibrin gel promoted the deposition of collagen I, III, and IV, and readily induced apoptosis during the initial stage of angiogenesis. In conclusion, we confirmed that EVs from DPSCs can promote angiogenesis in an injectable hydrogel in vitro, offering a novel and minimally invasive strategy for regenerative endodontic therapy.

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

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

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

Background/purpose

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

Materials and methods

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

Results

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

Conclusion

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

Evolving applications of the egg: chorioallantoic membrane assay and ex vivo organotypic culture of materials for bone tissue engineering

The chick chorioallantoic membrane model has been around for over a century, applied in angiogenic, oncology, dental and xenograft research. Despite its often perceived archaic, redolent history, the chorioallantoic membrane assay offers new and exciting opportunities for material and growth factor evaluation in bone tissue engineering. Currently, superior/improved experimental methodology for the chorioallantoic membrane assay are difficult to identify, given an absence of scientific consensus in defining experimental approaches, including timing of inoculation with materials and the analysis of results. In addition, critically, regulatory and welfare issues impact upon experimental designs. Given such disparate points, this review details recent research using the ex vivo chorioallantoic membrane assay and the ex vivo organotypic culture to advance the field of bone tissue engineering, and highlights potential areas of improvement for their application based on recent developments within our group and the tissue engineering field.