Oral stem cells, decoding and mapping the resident cells populations.

The teeth and their supporting tissues provide an easily accessible source of oral stem cells. These different stem cell populations have been extensively studied for their properties, such as high plasticity and clonogenicity, expressing stem cell markers and potency for multilineage differentiation in vitro. Such cells with stem cell properties have been derived and characterised from the dental pulp tissue, the apical papilla region of roots in development, as well as the supporting tissue of periodontal ligament that anchors the tooth within the alveolar socket and the soft gingival tissue. Studying the dental pulp stem cell populations in a continuously growing mouse incisor model, as a traceable in vivo model, enables the researchers to study the properties, origin and behaviour of mesenchymal stem cells. On the other side, the oral mucosa with its remarkable scarless wound healing phenotype, offers a model to study a well-coordinated system of healing because of coordinated actions between epithelial, mesenchymal and immune cells populations. Although described as homogeneous cell populations following their in vitro expansion, the increasing application of approaches that allow tracing of individual cells over time, along with single-cell RNA-sequencing, reveal that different oral stem cells are indeed diverse populations and there is a highly organised map of cell populations according to their location in resident tissues, elucidating diverse stem cell niches within the oral tissues. This review covers the current knowledge of diverse oral stem cells, focusing on the new approaches in studying these cells. These approaches "decode" and "map" the resident cells populations of diverse oral tissues and contribute to a better understanding of the "stem cells niche architecture and interactions. Considering the high accessibility and simplicity in obtaining these diverse stem cells, the new findings offer potential in development of translational tissue engineering approaches and innovative therapeutic solutions.