Photobiomodulation therapy facilitates transplantation of dental pulp stem cells for spinal cord injury

Abstract

Background Dental pulp stem cells (DPSCs) have been demonstrated as a therapeutic strategy for spinal cord injury (SCI). However, post-traumatic response following SCI leads to activation of oxidative stress and mitochondrial function, which affects the survival rate of grafted cells. Photobiomodulation therapy is noninvasive option promoting regeneration and repair in SCI. This study aimed to probe whether PBMT would regulate the survival and differentiation of transplanted DPSCs in the model of SCI. Methods Firstly, the protective effects of PBMT were investigated in vitro using DPSCs induced by H₂O₂. The anti-apoptotic effect was characterized using TUNEL staining, flow cytometry, western blot and transmission electron microscope (TEM). Then, a retroviral system was applied to establish DPSCs co-expressing luciferin and green fluorescent protein (GFP) (named as Luc-GFP-DPSCs) to trace transplanted cells in vivo. The survival status of engrafted DPSCs was assessed through bioluminescence imaging (BLI) after the cell transplantation. Behavioral tests and histological staining were carried out to observe the injury recovery and immunofluorescent staining was used to clarify the differentiation of transplanted DPSCs in mice model of SCI. Results The results revealed the protective effects of PBMT on H₂O₂-induced DPSCs cell death in vitro. PBMT could relieve apoptosis and oxidative stress of DPSCs. Meanwhile, the study revealed that PBMT treatment significantly promoted survival and neural differentiation of grafted DPSCs in vivo. PBMT assisting DPSCs transplantation could achieve better results in functional recovery than cellular transplantation alone. Conclusions PBMT facilitates the potential repair and regeneration of transplanted DPSCs in SCI.