In-vivo Regenerative Potential of Human Apical Papilla Cells

Objectives: Regenerative medicine and tissue engineering are critically intertwined with advances in stem cell biology. Apical papilla is considered the remnant structure of the dental papilla responsible for the dentin-pulp complex formation. This undifferentiated tissue represents a source of adult stem cells that may be involved in regenerative endodontic procedures. The purpose of this study was to evaluate the regenerative potential of human apical papilla cells (APCs) when combined with an autologous scaffold, platelet-rich plasma (PRP), in the presence of different biomaterials (ProRoot MTA and Biodentine).
Methods: APCs were collected from human third molars with incomplete rhizogenesis. PRP was prepared from donor blood samples. APCs/PRP suspension was injected on monorradicular roots prepared with a diameter of 1.1mm and 6mm length. To mimic clinic application, MTA and Biodentine were compacted separately in one of the root ends. Root segments were subcutaneously implanted on the back of nude athymic rats (RNU) for four months. After this period, animals were euthanized, samples were collected and histological sections prepared.
Results: APCs were successfully isolated, expanded and identified in vitro. Histological evaluation shows that APCs are capable of generating dental pulp-like tissue, containing blood vessels, nerves, odontoblasts and dentin-like tissue in all groups. Mineralized tissue, referred as tertiary dentin, was formed in apposition to inner dentinal walls of the empty root. This newly formed tissue presented an irregular and amorphous structure, but in some cases regular dentin with parallel dentin tubules was observed. In biomaterials presence, a mineralized tissue bridge formation was observed. No bacterial contamination or severe inflammation reaction was observed.
Conclusions: This study provides evidence that dental pulp-like tissue and dentin-like tissue can be generated de novo using APCs combined with PRP and Pro Root MTA/Biodentine.