Neural Regeneration/Remodeling in Engineered Coronal Pulp Tissue in the Rat Molar

This study aimed to examine the process of reinnervation during coronal pulp tissue regeneration in a rat model in which rat bone marrow mesenchymal stem cells were implanted in pulpotomized molars.

The maxillary first molars of Wistar rats were pulpotomized, and preformed biodegradable porous poly L-lactic acid scaffolds and hydrogel carrying rat bone marrow mesenchymal stem cells were implanted in the pulp chamber. After 3, 7, and 14 days, the implanted teeth were processed for histologic analysis; immunoperoxidase staining for protein gene product 9.5 (a general neuronal marker), calcitonin gene-related peptide (CGRP), or substance P (SP); and real-time polymerase chain reaction for nerve growth factor (NGF) and growth-associated protein 43 (GAP-43) messenger RNA (mRNA) expression.

Histologic analysis of the implanted region revealed sparse cellular distribution at 3 days, pulplike tissue with a thin dentin bridge-like structure at 7 days, and dentin bridge-like mineralized tissue formation and resorption of most scaffolds at 14 days. Protein gene product 9.5 and CGRP-immunoreactive nerve fibers showed the lowest density at 3 days and significantly increased until 14 days when the CGRP-immunoreactive fibers reached normal levels. SP-immunoreactive nerve fibers showed the highest density at 7 days and decreased to normal levels at 14 days. NGF mRNA increased with time, whereas GAP-43 mRNA levels peaked at 3 days and subsequently dropped until 14 days.

Regeneration/remodeling of SP-immunoreactive and CGRP-immunoreactive nerve fibers with increased mRNA expression of NGF and GAP-43 occurred in a rat model of coronal pulp tissue engineering with bone marrow mesenchymal stem cells.