Glomerular epithelial protein-1 promotes reparative dentin formation in vivo

Glomerular epithelial protein-1 (Glepp1/PTPRO), a member of the R3 subtype family of receptor-type protein tyrosine phosphatases that, regulates cellular processes, like proliferation, differentiation, and apoptosis, involved in odontogenesis, with its overexpression causing thicker dentin. However, its in vivo impact during reparative dentin formation remains unexplored. This study evaluated an alternative therapeutic approach of enhancing natural dentin repair by overexpressing Glepp1 in an animal model. A pulp access cavity was prepared on the upper right first molar of eight-week-old male mice, followed by local delivery of Glepp1 adeno-associated virus (AAV) or phosphate-buffered saline (PBS). Hematoxylin and eosin (H&E) staining and immunohistochemistry were used to assess histological and cellular physiological changes after three and five days of treatment. Micro-CT and H&E analyses 42 days after AAV-mediated delivery revealed significantly enhanced dentin bridge formation and increased mineralized tissue deposition in the Glepp1 AAV-delivered group. Glepp1 AAV-delivered samples showed increased immunolocalization of reparative dentin-related markers, including Nestin, runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and osteopontin (OPN) at days 3 and 5, suggesting enhanced mineralization and extracellular matrix formation. Furthermore, decreased tumor necrosis factor α (TNFα) and increased transforming growth factor β - 1 (TGF-β1) localization with enhanced cluster of differentiation 31 (CD31) immunostaining indicated inflammatory response modulation and improved vascularization. These findings highlight local Glepp1 overexpression using the AAV system as a viable strategy for dentin-pulp regeneration via modulation of cellular and molecular mechanisms.