## 5 Clinical Studies  
Gene electrotransfer can achieve long-lasting gene expression and may be used in different tissue types in various species. Reconstructive surgery widely uses skin flaps to repair large and deep skin injuries. The significant difficulty in this type of treatment is the formation of ischemia and subsequent necrosis of the transplanted tissue. To prevent this, exogenous vascular endothelial growth factor (VEGF) can be delivered to insufficiently ischemic areas. An increase in VEGF level causes the upregulation of endothelial nitric oxide synthase, increasing NO concentration, which signals smooth muscles to relax, leading to vasodilation, increasing blood flow, and better perfusion. Regrettably, the delivery of VEGF presents some difficulty. However, the research has shown that EP is suitable for delivering plasmid DNA encoding VEGF to ischemic skin and rat skin flap. Compared to injection alone, electroporation resulted in a 6.6-fold increase in VEGF protein on day 2 after treatment in the distal area of skin flaps [73]. Using such gene therapy presents better results while applying EP, either in skin flap healing and survival or ischemic wound treatment. A major challenge for medicine is the treatment of diabetic skin wounds. It is patients with diabetes who particularly experience nonhealing skin lesions and injuries. LL-37 peptide promotes wound healing and inhibits bacterial growth. Unfortunately, there are difficulties in delivering it into the tissues. However, the delivery of plasmid-encoding hCAP-18/LL-37 by EP has turned out to be effective and resulted in the increased expression of LL-37 in the epithelium. The electroporation of phCAP-18/LL-37 restored delayed wound healing in diabetic mice. Wound closure occurred in 61 \(\pm\) 8% of animals treated with LL-37 delivered through EP, whereas in the control group, the wound was closed in 43 \(\pm\) 9% of individuals [74]. These results clearly indicate that the application of treatment with EP was more successful (Figure 4). Gene therapy is a promising strategy for treating heart disease. Unfortunately, most current strategies in gene delivery to the heart are ineffective. Nevertheless, EP is a method that significantly increases the potential for the gene transfer and induction of gene expression at a clinically relevant level in this organ [75]. In addition, while there have been doubts about whether using electrical pulses near the heart is dangerous, studies have shown that EP can be a safe and, at the same time, effective method for delivering genes to a working heart [76]. Other research shows that gene delivery to the cardiac muscle tissue by plasmid injections only results in lower gene expression than the electroporated tissue [77]. A fair number of gene delivery methods into the lungs have been developed; however, most have severe limitations. EP exceeds the major problem since it shows a low inflammatory response in lung tissue. In the study, purified plasmid DNA was introduced into the lungs and subjected to EP in mice bodies. The expression of the injected gene was  
Figure 4: Schematic visualization of the role that EP plays in wound healing, allowing plasmid DNA to enter the cell via GET and therefore inducing an increase in either LL37 or VEGF level [75]. The Figure was partly generated using Servier Medical Art, provided by Servier, licensed under a Creative Commons Attribution 3.0 unported license. detected as early as day one after the procedure, mainly in alveolar epithelial cells type I and II. In contrast, no clinically significant expression was detected with DNA injection without EP [78]. Another electroporated gene, hepatocyte growth factor (HGF), is able to affect alveolar type II epithelial cells and may improve the recovery process of the lung tissue. The study of bleomycin-induced lung fibrosis consisted of plasmid encoding HGF injection and EP in rats.