Peripheral Lysosomal Positioning in Inflamed Odontoblasts Facilitates Mineralization.

Abstract

Introduction: Odontoblasts, terminally differentiated dentin-producing cells, critically rely on lysosomal functions for intracellular recycling and renewal. Beyond their traditional degradative role, lysosomes actively orchestrate cellular responses to external stimuli through precise and rapid intracellular trafficking and positioning. This study aimed to explore the influence of lysosomal positioning on odontoblast mineralization and the underlying mechanisms implicated in carious inflammation.

Methods: Human dental pulp stem cells (hDPSCs) were induced to differentiate into human odontoblast-like cells (hOBLCs). hOBLCs were treated with various doses of LPS (0.1, 1, 5 μg/mL) to mimic carious inflammation. Lysosomal positioning was examined by immunofluorescence staining of LAMP1 in healthy and carious human teeth, LPS-treated hOBLCs, mouse lower incisors at postnatal day 2.5, and mineralization medium cultured hDPSCs. Lysosomal positioning was manipulated by knockdown or overexpression of SNAPIN or ARL8B. Mineralization was assessed by ARS staining and expression of DSPP and DMP1. Lysosomal exocytosis was examined by detection of lysosomal-plasma membrane fusion, surface exposure of LAMP1 luminal epitopes (1D4B) and extracellularly released lysosomal enzymes.

Results: Peripheral lysosomal positioning was markedly increased in odontoblasts within moderate and extensive carious lesions (P < .001) and in hOBLCs following LPS treatment. Increased peripheral dispersion of lysosomes was similarly observed during odontoblastic differentiation in vivo and in vitro. Moreover, peripheral lysosomal positioning promoted mineralization in inflamed hOBLCs, potentially via mTORC1 signaling pathway and lysosomal exocytosis.

Conclusion: Inflammatory stimuli prompted a relocation of lysosomes in odontoblasts, redistributing them from perinuclear location towards the cell periphery, which in turn facilitated mineralization, potentially via mTORC1 signaling and lysosomal exocytosis.