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Received Jul 22, 2017; Accepted Mar 6, 2018
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1. Introduction
The involvement of mesenchymal stem cells (MSCs) in the regeneration of damaged or aged tissues is well supported by current research. Furthermore, cell manufacturing procedures for obtaining high quality, bioactive MSCs from human bone marrow has been approved by the US Food and Drug Administration [1], while recent developments in regenerative medicine have suggested that there is a paracrine/endocrine mechanism involved with MSC-mediated repair of damaged tissues. Initially, as Pittenger and colleagues pointed out, MSCs were used primarily for their cytokine and growth factor production rather than for their cell replacement and differentiation ability [2]. Later on, it was recognized that the most effective contribution to the regenerative process comes from exosomes released from MSCs. These exosomes have a complex composition that mirrors not only their parental cells but also their ability to migrate towards specific tissue [3]. This property is common for MSCs regardless of their tissue origin.
Dental pulp mesenchymal stem/stromal cells (DP-MSCs) are of particular interest because of their neurotropic character, which makes DP-MSCs and their exosomes particularly attractive as a new therapeutic tool for the alleviation of symptoms of neurodegenerative diseases and many other difficultly treatable maladies. Dental tissue-derived stem cells besides DP-MSCs include multiple types such as stem cells from exfoliated deciduous teeth (SHED), stem cells from apical papilla (SCAP), periodontal ligament stem cells (PDLSCs), and dental follicle progenitor cells (DFPCs) [4]. All of them can be isolated from a single tooth and behave as mesenchymal stem/stromal cells. MSCs derived from different dental tissues possess multiple differentiation capabilities. In vitro comparisons of the properties of different types of human dental MSCs, such as their multipotentiality and other phenotypic characteristics, have been performed and comprehensively reviewed [5]. From the regenerative medicine point of view, the most valuable cells are the deciduous tooth cells, which, being young, are nearest to embryonic character and distinguishable from stem cells isolated from adult teeth. However, despite their differences, all of these dental tissue-derived stem cells are not distinguishable morphologically and do not differ in a...