Local Injection of Pulp Cells Enhances Wound Healing during the Initial Proliferative Phase through the Stimulation of Host Angiogenesis

Abstract

IntroductionThe aim of this study was to examine the effect of pulp cell injection on host angiogenesis during wound healing. MethodsPulp cells were isolated from extracted premolars by the outgrowth method. Fluorescently labeled pulp cells or phosphate-buffered saline were locally injected into a mouse wound healing model. Wound healing was evaluated using photographs, histology, and real-time reverse-transcription polymerase chain reaction. Injected cells were traced. Angiogenesis was measured by performing immunohistochemical staining of CD31, a marker of vascular endothelial cells. The level of secreted vascular endothelial growth factor in the pulp cell conditioned medium (CM) was compared with the CM of fibroblasts and keratinocytes. The paracrine effect of pulp CM on angiogenesis was evaluated by tubular network formation using endothelial cells. ResultsThe local injection of pulp cells enhanced wound closure during the initial stage when compared to the injection of phosphate-buffered saline. The amount of extracellular matrix production and the expression of CD31+ cells were also increased in response to pulp cell injection when compared with the injection of phosphate-buffered saline. The fluorescently labeled pulp cells were engrafted into the hair follicles of the adjacent normal dermis but not into the wound site per se. A significantly higher level of vascular endothelial growth factor was secreted into the CM of pulp cells when compared with dermal fibroblast and keratinocytes. Tubular network formation of endothelial cells and the proliferation of dermal fibroblasts were significantly enhanced by the application of pulp cell CM when compared with control media. ConclusionsOur results show that local injection of pulp cells is effective in enhancing wound healing during the initial proliferative phase, especially through paracrine mechanisms regulating host angiogenesis and proliferation.