CPNE7 Maintains Functional Activity of Odontoblasts and Promote Dentin Regeneration

Objectives:
Regeneration of dentin has been actively tried with various biomolecules, yet, the regenerated hard tissues are more like bone than dentin in many cases, lacking the tubule structure. Our previous study demonstrated that CPNE7, identified in preameloblast-conditioned medium, induces odontoblast differentiation, and promoted tertiary dentin formation. In this study, we investigated the role of CPNE7 in stimulating physiologic dentin formation and gauged its weight as a component of dentin matrix proteins. Moreover, we synthesized and evaluated a novel functional peptide KH001.

Methods: Artificial tooth defects in varying depths were generated in beagle premolars. The dentin exposures were capped with GI cement after treating rhCpne7, while for pulp exposure model, GIC filling followed treating rhCPNE7 and MTA. Tertiary dentin formation was histologically evaluated 3 or 6 weeks after the experiment. Further, the effects of non-collagenous dentin matrix proteins (NCDMPs) with or without neutralizing CPNE7 was assessed in cavity models. In vitro, ex vivo, and in vivo evaluations of KH001 were performed as well.


Results: We observed tertiary dentin formation in both the dentin and pulp exposure models. The regenerated dentin showed the characteristics of physiologic dentin, regardless of the cavity depths. Dentinal tubule structure was clearly observed beneath the remaining dentin. In the case of NCDMPs treatment, tubular dentin was regenerated as previously reported. However, the number of dentinal tubules decreased remarkably when CPNE7 was neutralized. KH001 demonstrated similar functions.


Conclusions:
CPNE7 seems to induce both the odontoblast differentiation and reactivation. The extent of the external stimuli determines whether CPNE7 induces pulp stem cells to differentiate into new odontoblasts, or simply reactivates the underlying odontoblasts at resting phase. In both cases, physiologic dentin retaining dentinal tubules were regenerated in vivo. Its derivative oligopeptide KH001 also demonstrated odontoblast differentiation in vitro, dentin-pulp like complex formation ex vivo, and tubular dentin regeneration in vivo.