The combined use of cell sheet fragments of periodontal ligament stem cells and platelet-rich fibrin granules for avulsed tooth reimplantation

The aim of this study was to construct a cell transplant method consisting of cell sheet fragments of periodontal ligament stem cells (PDLSCs) and platelet-rich fibrin (PRF) granules to enhance periodontal healing in avulsed tooth reimplantation. To test this concept in vitro, human PDLSCs were isolated and characterized by colony forming unit assay, cell surface marker characterizations, and their osteogenic/adipogenic differentiation potential. The biological effects of autologous PRF as a growth factor-enriched endogenous scaffold on human PDLSCs were then investigated and quantified for statistical analyses, including cell viability and proliferation, alkaline phosphatase (ALP) activity, and the gene expression of bone sialoprotein (BSP), osteocalcin (OCN), collagen I (Col-I), and cementum protein 23 (CP23). It was found that the PRF induced a significant and continuous stimulation of proliferation in human PDLSCs throughout the 7-day incubation period. Furthermore, the PRF suppressed the osteoblastic differentiation of PDLSCs by decreasing ALP activity and the gene expression of BSP and OCN while up-regulating the mRNA expression levels of Col-I and CP23 during the testing period. To assess the potential application of the PDLSCs/PRF construct in tooth reimplantation, 36 incisors were extracted from 6 dogs. The incisors then underwent 2 h of dry storage and were randomly divided into four groups receiving different strategies of reimplantation, where the avulsed teeth were reimplanted with the use of the autologous PDLSCs/PRF construct (cell sheet fragments in combination with PRF granules), with the use of autologous PDLSCs or PRF alone, or without adjuvant use of PRF or PDLSCs. Eight weeks post-reimplantation, the PDLSCs/PRF group achieved a more effective periodontal healing, characterized by the regeneration of PDL-like tissues and a reduction of ankylosis and inflammation, compared with the other testing groups. These overall results suggest that the PDLSCs/PRF construct may be a useful tool for alveolar surgery that has the potential to improve the clinical outcomes in future avulsed tooth reimplantations.