Conditioned medium from the inflammatory microenvironment of human dental pulp stem cells regulated functional pulp regeneration

Objective This study explored the effects of inflammatory microenvironment on stem cells from the apical papilla (SCAP) for cell homing strategy-based pulp regeneration. Methods Dental pulp stem cells (DPSCs) were treated with lipopolysaccharide (LPS) for 48 h, creating a conditioned medium (LPS-CM). The influence of LPS-CM on SCAP proliferation, migration, odontogenic and neurogenic differentiation, pro-angiogenetic effects, cell apoptosis and senescence were assessed. Following construction of the ectopic pulp regeneration model, treated dentin matrix (TDM) specimens were harvested after a 2-month implantation period and subjected to histological examination to assess changes in the regenerated tissues. Results We found that a moderate inflammatory microenvironment (LPS-5 CM) significantly enhanced SCAP proliferation, migration, odontogenic differentiation, and the formation of neuron-like cells. In contrast, a high-inflammatory microenvironment (LPS-10 CM) exerted inhibitory effects on these processes and concurrently induced cellular apoptosis and senescence. All LPS-CM groups promoted angiogenesis in vitro. Critically, only the LPS-5 CM group successfully facilitated the regeneration of well-vascularized pulp-like tissue in vivo. Conclusions Inflammatory microenvironment performed a dual role in pulp regeneration. A moderate inflammatory stimulus enhances the regenerative functions of SCAP, while excessive inflammation is detrimental. This underscores the importance of inflammatory signals for successful cell homing-based pulp regeneration. Graphical abstract