Vezikovajinal Fistül Onarımı İçin Pro-Anjiogenik/Antibakteriyel Doku İnterpozisyon Flep Eşleniğinin Tasarımı ve Geliştirilmesi

Abstract

A vesicovaginal fistula (VVF) is an anbormal opening between the bladder and vagina that causes continous leakage of urine and urinary incontinence. Definitive treatment of VVF is surgery and the type of surgical intervention is chosen depending on factors such as the size and location of the fistula, and the surgeon's experience. In order to achieve successful surgical repair of VVF, a well-vascularized tissue interposition flap is usually placed between the bladder and the vagina. Tissue interposition flaps increase the chances of success of treatment by acting as a barrier between the bladder and the vagina and increasing tissue formation and vascularization. Autologous tissue interposition flaps are widely preferred in the surgical treatment of VVF. However, the use of autologous flaps is not always possible due to the general health status of the patient, the characteristics of the fistula, and the surgical technique. In cases where the use of autologous tissues is not possible, the use of synthetic interposition flaps has been suggested and tried in several studies. None of these flaps were designed specifically for the treatment of VVF and have not ever gained widespread clinical acceptance. In the first part of this thesis, the clinical success rates of tissue interposition flaps used in VVF repair were evaluated, and a treatment-specific, pro-angiogenic, and antibacterial tissue interposition flap in fiber form was designed considering clinical needs. In the second part of the thesis, the designed flaps were produced by electro-spinning method and examined in vitro and in vivo. For this purpose, bilayered fibers (Fib/PCL) were produced by an electro-spinning method using silk fibroin (Fib) and polycaprolactone (PCL) polymers. 17-β-estradiol (E2), which has pro-angiogenic properties, was added to the first layer of Fib/PCL fibers, and AgNO3, which has an antibacterial effect, was added to the second layer to reduce it to silver nanoparticles (AgNPs). The angiogenic and antibacterial effects of fibers containing E2 and AgNPs (E2Fib/PCL-Ag) were investigated. Fibers with smooth and homogeneous morphology varying between 0,28-0,55 µm in diameter did not show any toxic effects in the L929 cell line. When the release of E2 from fibers are examined; initial burst effect was observed in the first 7 days and then a continuous release profile was observed after the 14th day. AgNPs release from the fibers showed a similar release profile. The angiogenic effect of E2 containing fibers was investigated by chorioallantoic membrane (CAM) assay. It was observed that these fibers increased the normalized vascular densities between 10 and 36% compared to the control group. These results proved that E2 released from the fiber structure showed an angiogenic effect. It has been determined that fibers containing AgNPs have antibacterial effects against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Lactobacillus acidophilus ATCC 4356 and Candida albicans ATCC 90028 strains that are commonly found in the bladder and vaginal flora. Fibers containing E2 and AgNP were implanted separately in the abdomen and paravaginal regions of rats and the early tissue response was comparatively examined. For this purpose, tissue sections taken from these regions were evaluated and scored in terms of polymorphonuclear leukocytes (PMN), mononuclear cells (MN), connective tissue organization and vascularization. It was observed that E2 containing bilayered fibers were observed to increase vascularization and connective tissue formation as compared to the control. On the other hand, when the fibers were evaluated in terms of infection, AgNP containing fibers showed less foreign body reaction-induced infection than the other groups. When the tissue samples taken from the paravaginal and abdomen regions were examined in terms of PMN, MN, connective tissue organization, and the number of giant cells, it was observed that there was no significant difference between the regions. As a result, it is thought that bilayer fibers developed as tissue interposition flap equivalents have the potential for clinical use and their translation to the clinic may be possible with prospective studies.