ERS-PERK Pathway is Involved in the Repair of the Pulpo-Dentinal Complex Under an Inflammatory Microenvironment

Protein kinase R-like endoplasmic reticulum kinase (PERK) mediates the endoplasmic reticulum stress (ERS) response. However, it remains unclear whether PERK regulates the odontogenic differentiation of human dental pulp stem cells (hDPSCs) and contributes to the repair and regeneration of the pulpo-dentinal complex (PDC) during inflammation. This study aimed to investigate the regulation of ERS-PERK in the differentiation and apoptosis of hDPSCs and its contribution to the repair and regeneration of PDC injury in the inflammatory microenvironment.

In vivo dentin defect (DD group) and pulp perforation (PP group) were established to evaluate the expression and healing-promoting properties of PERK in dental pulp at different injury stages. Using LPS with concentration gradients to simulate the inflammatory microenvironment, the activation of ERS-PERK pathway-related genes was investigated using quantitative real-time polymerase chain reaction (RT-qPCR). hDPSCs' apoptosis and odontogenic potential under inflammatory stimulation were also assessed using Calcein-AM/7AAD Live/Dead cell double staining, RT-qPCR, alkaline phosphatase (ALP) staining, and Alizarin Red S (ARS) staining. The potential role of PERK in odontogenesis and apoptosis of hDPSCs under inflammatory stimulation was explored.

With the extension of dental defects in vivo, PERK expression was gradually upregulated in the DD group, whereas, in the PP group, it increased in the early stage of inflammation and then decreased. Under LPS stimulation, the expression of inflammatory factors increased with the activation of the PERK pathway, while the ALP activity of hDPSCs and mineralized nodules decreased. PERK knockdown attenuated mRNA levels of ERS-related genes and apoptosis-related genes, whereas the expression of odontogenic-related factors increased. The ALP activity and the number of mineralized nodules increased. PERK may regulate odontogenesis through the mitochondria-associated endoplasmic reticulum (ER) membrane.

Our results demonstrated PERK pathway activation, which enhances the expression of inflammatory factors and suppresses the odontogenic ability of hDPSCs in inflammatory microenvironments.