Ultrasound-Mediated Transdermal Drug Transport Of PGE1, Heparin And VEGF And Their Effects On Flap Survival In The Rats

Background:It has been reported that the Prostaglandin El (PGE1), heparin and vascular endothelial growth factor (VEGF) can increase flap survival in many experimental and clinical studies, and the main pharmacological effects of them are peripheral vasodilation, suppression of oxygen radical formation and platelet aggregation, anti-inflammatory properties, anti-thrombin and angiogenesis. Because of these effects, intra-arterial and intravenous administration or intradermal injection have been widely used in clinical or experimental studies. However, the side effects such as angitis, pain, bleeding or angiogenesis in tumor patients limit the utilization of these drugs, and moreover concentration of the drugs in ischemic area following local application by injections is very low. Because of these limitations, topical application has been attempted in the hope that it will be more effective and also will be safer and simpler. Ultrasound-Mediated Transdermal Drug Transport (UMTDT) may be one of ideal method for topical administrations of these drugs.Objective:In this study, we investigate the possibility and the methods for UMTDT of PGE1, heparin and VEGF, and the effects of them by UMTDT on the flap survival.Materials and Methods:1. In this study, a calorimeter method was employed to determine the ultrasound intensity or the power of this machine designed by our groups; the measurement of temperature in ultrasound probe, ultrasound medium and rat skin, and the macroscopic and microscopic changes of the local rat skins after the low-frequency ultrasound (20K) treatment with a intensity 7W/cm2 for 2 min and 1.5 W/cm2 for 5 min (pulse mode 5min on and 5min off) were carried out.2. The concentration of PGEl and the activated partial thromboplastin time (APTT) in serum of epigastric and caudal vena were measured by PGEl ELISA kit and APTT test kit after UMTDT of PGEl and heparin in the time of Oh, 5min, 0.5h, lh, 2h, 4h, 6h, 8h, 12h, 18h were performed; The flow of blood in flap skin was determined with the laser Doppler in the time of Oh, 0.5h, lh, 2h, 4h following tropical application of PGEl and heparin by sonophoresis.3. The random flap survival rates were measured using photo-analysis system following UMTDT of PGEl and heparin, and the MDA and MPO of tissues in three parts of the flaps were determined according to the kits. Morphological analysis was carried out in other tissue samples.4. The concentrations of VEGF in three parts of the random flap and in the distal part of the flap following UMTDT of VEGF were determined by VEGF ELISA kit. The random flap survival rates were also measured using photo-analysis system following UMTDT of VEGF, and the MDA and MPO in tissue of three parts of the flaps were determined according to the kits. Morphological analysisand immunohistochemical expression of VEGF were evaluated using light microscopy.Results:1. The low-frequency ulteasound was safe and had not obvious harm to the rat skin macroscopically and macroscopically after the low-frequency ultrasound (20K.) treatment with a intensity 7W/cm2 for 2 min and 1.5 W/cm2 for 5 min (pulse mode 5s on and 5s off) was performed, and the increase of temperature in ultrasound probe was 8.2 °C after treatment.2. Compared to the control group, the significant increases of PGEl and APTT in the serum were seen at the times of 0.5h, lh, 2h, 4h, 6h, 8h and 12h after UMTDT of PGEl and heparin. The blood flow in centre of the island flap increased significantly at the times of 0.5h, lh, 2h, and 4h, and the enhancement of APTT in serum of caudal vena was not significant in the course of the study, when compared to that in the time of Oh.3. Flap survival rate in the groups of PGEl applicated in the middle part of the flap and heparin in the distal part of the flap, or combination them, enhanced significantly, when compared with the control group (p<0.05). The contents of MDA and MPO in the distal part of the flap increased significantly compared with that in the middle or proximate parts (p<0.05). The formation of more new and very small capillaries owing to angiogenesis in fascia layer after UMTDT of heparin was obvious and different from that in control group or PGEl group.