Participação de pericitos e progenitores neurais na odontogênese e envelhecimento dentário e reparo pulpar após capeamento com MTA associado à fotobiomodulação: análise em modelo transgênico in vivo Nestin-GFP/NG2-Dsred

Abstract

Pericytes and neural cells are known to collaborate in the regeneration of pulp tissue. Cell-based therapies that can stimulate these components may hold therapeutic relevance in vital dental pulp conditions. The objective of this study was to map neural progenitors and pericytes during odontogenesis and dental aging, and to compare the actions of these cells in adult teeth following pulp capping with Mineral Trioxide Aggregate (MTA) and MTA in conjunction with photobiomodulation (PBMT) after 7 and 21 days. Transgenic double-positive NestinGFP/NG2DsRed C57BL/6 mice were utilized for tracking these cells, with Nestin serving as a marker for undifferentiated neural progenitors and the NG2 protein as a marker for pericytes. Two subpopulations of pericytes were also investigated: those that were Nestin+NG2+ and those that were Nestin-NG2+. Teeth from neonatal animals at 1 and 14 days, which did not survive to adulthood, as well as from adult animals aged 2 and 12 months, were analyzed to understand the role of the marked cells during odontogenesis and aging. Subsequently, adult animals (2 months) underwent experimental injury to the dental pulp of their first upper molars. The cavities were treated with either MTA or MTA combined with PBMT (5 J/cm², 7s, 20 mW, 0.71 W/cm²) daily at time points of 0, 24, 48, and 72 hours. The cavities were then sealed with photoactivated flow resin, and the animals were euthanized at 7 and 21 days. Cellular tracking was performed using confocal microscopy, where the green (GFP), red (DSRed), and blue (DAPI) channels and their compositions were utilized to quantify cellular fluorescence in the tissue. Tissue architecture was assessed through routine histology to evaluate signs of pulp vitality, presence of blood vessels, and inflammatory markers, while the presence of dentin or osteodentin, nodules, and diffuse calcifications was observed using Masson's trichrome staining. Genes related to the cells of interest (Nestin, NG2, GFAP), tissue repair (CXCL12, CD105), and odontogenesis (RUNX-2 and DSPP) were quantified via RT-qPCR. We demonstrated that pericytes appear to serve as progenitor cells for odontoblasts during odontogenesis, and that the NG2 protein is re-expressed in teeth that have undergone some form of harmful stimulus throughout their lifespan. Teeth constitute sources of neural progenitor cells, even in animals aged 12 months. Following pulp capping with MTA, PBMT as an adjunct treatment promoted repair that resembled original pulp tissue more closely, with fewer inflammatory signs and qualitatively reduced pulp calcifications. After 21 days, the population of cells positive for the undifferentiated markers Nestin and GFAP was greater than that in the control group. The combination of MTA and PBMT resulted in significant dentin formation with notable expression of DSPP and RUNX-2 compared to the group treated exclusively with MTA. The MTA/PBMT combination appears promising for the conservative treatment of dental pulp.