Growth effect of endothelial cell by reactive oxygen species generated from photodynamic action

Abstract

The principal function of vascular endothelial cells is to secrete substances such as nitric oxide (NO) that prevent clotting. After vascular graft implantation, the absence of endothelial cells on the luminal surface of graft induces thrombogenesis. Therefore, the acceleration of re-endothelialization on graft surface is considered to be an effective strategy to improve the patency of vascular grafts. Photodynamic therapy (PDT) is the interaction of light with photosensitive agents to induce an energy transfer and a local chemical effect. Subsequent irradiation of treated tissues with an appropriate visible light source induces the production of reactive oxygen species (ROS). It is well known that high concentrations of ROS cause endothelial cell apoptosis and death. Low levels of ROS, on the other hand, play an important role in functioning as signaling molecules to mediate endothelial cell proliferation and migration. In this study, we investigated that extracellular ROS generated from photodynamic therapy stimulate endothelial cell proliferation.First we made photosensitizer (PS)-incorporated Polyurethane (PU) film by the solvent casting method and hematoporphyrin (HP) was used as a PS. Human umbilical vein endothelial cells (HUVECs) were seeded on the HP-incorporated PU films and incubated for 24h. Then the cells cultured on the PU film were irradiated with a green light emitting diode (LED) source. After incubation for different durations, we analyzed the production rate of ROS by intracellular ROS and extracellular ROS assay after PDT and tested cell growth by MTT viability assay to evaluate the growth promotion effects of ROS on cell proliferation.In conclusion, we demonstrate that a LED treatment with hematoporphyrin of small concentrations can be used to stimulate cell proliferation and increase the S-phase cell population and does not negatively affect the function of proliferated cells. Our results showed that a moderate production of extracellular ROS induced by mild phototreatments was sufficient to accelerate proliferation of endothelial cell and also promote endothelialization.