Cell Homing for Pulp Tissue Engineering with Endogenous Dentin Matrix Proteins

Introduction: Compelling evidence pinpoints that pulp tissue engineering after the transplantation of stem cells is possible. Although intriguing, severe problems regarding clinical feasibility remain. Cell homing has been proposed as a viable alternative in which dentin derived growth factors in a conducive scaffold may attract resident cells to form pulplike tissue. In this study, an ectopic animal model for in situ dental pulp tissue engineering was developed to evaluate whether pulplike tissue formation in empty root canals after the attraction of stem cells was possible and whether this could be enhanced by dentin-derived growth factors. Methods: Three types of fibrin (custom-made fibrin, fibrin sealant, and plasma rich in growth factors [PRGF]) as well as a self-assembling peptide were evaluated in vivo in a modified tooth root model using human teeth. Root canal dentin was conditioned with EDTA, tooth roots were filled with growth factor laden scaffolds, and dental pulp stem cells in collagen were placed at the root tip. Constructs were implanted into immunocompromised mice for 4 weeks and subsequently analyzed histologically. Differential interference contrast and second harmonic generation imaging were performed for selected sections. Results: For custom-made fibrin and fibrin sealant with dentin matrix proteins, migration into the roots and the formation of a pulplike tissue were observed, whereas the peptide based scaffold appeared less suitable. PRGF supported tissue formation regardless of the addition of dentin matrix proteins. In the test groups with dentin matrix proteins and EDTA conditioning, differentiated odontoblastlike cells extended cellular processes into the dentinal tubules, which coincided with the deposition of the newly formed collagenous dentin matrix. Conclusions: This new cell homing model provides evidence that fibrin derivatives make applicable scaffolds and that dentin-derived proteins induce chemotaxis and pulplike tissue formation.