RECONSTRUCTIVE SURGERY Is there a Difference in Platelet-Rich Plasma Application Method and Frequency to Protect Against Urethral Stricture? Arif Aydin1, Mehmet Giray Sonmez1, Pembe Oltulu2, Rahim Kocabaş3, Leyla Öztürk Sonmez4,5, Hakan Hakkı Taşkapu1, Mehmet Balasar1 Purpose: To determine the efficacy of instillation frequency and submucosal injection of platelet-rich plasma (PRP) after urethral trauma to prevent urethral inflammation and spongiofibrosis. Materials and Methods: Sixty-five rats were used in the study; 50 rats were randomized into 5 groups with 10 rats in each group and 15 rats were allocated for PRP preparation. The urethras of all rats were traumatized with a pediatric urethrotome knife at 6 and 12 o’clock positions, except in the sham group. Group 1 was the sham group and had only urethral catheterization daily for 15 days, Group 2 was given 0.9% saline (physiologic saline [(UI+PS]) once a day after urethral injury (UI+ PS), Group 3 was injected with PRP submucosally after urethral injury, Group 4 was given PRP once a day as intraurethral instillation using a 22 Ga catheter sheath with urethral injury, and Group 5 was given PRP twice a day as intraurethral instillation using a 22 Ga catheter sheath with urethral injury. Each administration of PRP was administered as 300 million platelets/150 microliters. On day 15, the penises of the rats were degloved to perform penectomy. Histopathologic evaluation was made for spongiofibrosis, inflam- mation, and congestion in vascular structures. Results: When the sham group, UI+PS, UI+PRPx1, UI+PRPx2 and UI+PRPs groups are compared in total, there were significant differences identified for parameters other than edema. When the UI+PS, UI+PRPx1, UI+PRPx2 and UI+PRPs groups are compared, the UI+PS group was observed to have significantly more inflammation (mu- cosal inf. 2.42 ± 0.53) and spongiofibrosis (2.42 ± 0.53). All the PRP groups were identified to have significantly less mucosal inflammation (UI+PRPs 1 ± 0, UI + PRPx1; 1.4 ± 0.51, PRPx2; 1.33 ± 0.5) and spongiofibrosis (UI+PRPs; 1.57 ± 0.53, PRPx1; 1.2 ± 0.42, PRPx2; 1.55 ± 0.52). The group with the lowest spongiofibrosis was the PRPx1 group. Conclusion: This study showed that PRP significantly reduced mucosal inflammation and spongiofibrosis, inde- pendent of the administration route, when applied to the urethra after urethral trauma. Keywords: urethral stricture; PRP; urethral fibrosis; urethral inflammation; urethral healing INTRODUCTION Urethral stricture forms due to narrowing of the lu-men in any region of the urethra linked to fibro- sis development due to trauma, infection, or idiopathic causes.(1) Prevalence appears to be 0.9% in males, and it is a disease with very high treatment costs.(2) Currently, the most common cause of the urethral stricture etiolo- gy is iatrogenic interventions as a result of increasing endoscopic interventions, with the most common devel- opment after TUR-P.(3,4) Urethra stricture is a disease affecting all age groups and the quality of life of the patient, with minimally invasive treatments and high re- currence rates.(1,2,5) However, congenital urethral stric- tures are exceedingly rare in infants.(6) Whatever the eti- ology of stricture, excessive inflammation in the injury region and increased accumulation of type 3 collagen 1NEÜ Meram Medicine Faculty Department of Urology, Konya, Turkey. 2NEÜ Meram Medicine Faculty Department of Pathology, Konya, Turkey. 3NEÜ Meram Medicine Faculty Konüdam Exp. Medicine&App. Res. Center, Konya, Turkey. 4Selcuk University, Department of Physiology, Konya, Turkey. 5Beyhekim State Hospital, Department of Emergency Medicine, Konya, Turkey. *Correspondence: Department of Urology, NEÜ Meram Medicine Faculty, Konya, Turkey. Tel.: +903322237441. Mobile: +905055566988. E-mail: aydinarif@gmail.com. Received April 2020 & Accepted October 2020 as a result of this inflammation are considered to cause fibrosis.(7) To date, many agents have been studied to prevent formation of fibrosis, increase success rates of surgical treatments or reduce recurrence; however, none have entered routine use.(8) Platelet-rich plasma (PRP) is a preparation of autol- ogous plasma enriched with platelet concentrations above that normally found in whole blood.(9) PRP in- creases the speed of wound healing due to containing many growth factors. The synthesis of type 3 collagen causing fibrosis reduces with the effect of these factors. (10-12) Due to this effect of PRP, it is considered that it will have a significant effect on urethral healing. How- ever, there is no information about whether this effect will be enhanced by the easily applied method of instil- lation, or by submucosal injection of PRP. This study investigated the effects on urethral healing, inflamma- Urology Journal/Vol 18 No. 6/ November-December 2021/ pp. 663-669. [DOI: 10.22037/uj.v16i7.6100] tion, and fibrosis of PRP administered as intraurethral instillation and as submucosal injection in an experi- mentally-induced urethra injury model in rats and com- pared the administration methods. The aim of this study is to develop new treatment mo- dalities for urethral stricture that may form after urethral injury by evaluating the effect of PRP and the efficacy of the PRP administration form. MATERIALS AND METHODS This study was completed in N.E. University Konüdam Experimental Medicine Application and Research Center after receiving permission from the local animal ethics committee. Rats and Anesthesia A total of 65 Wistar male albino rats weighing 250-300 g were used in the study. The animals were kept in sep- arate cages at room temperature (22 °C) with 50% hu- midity during preoperative and postoperative periods. On the day of the experiment, rats were administered anesthesia with ketamine (50 mg/kg) under sterile con- ditions. Rats other than Wistar Albino species, female rats, those below 250 g and younger than 3 months were not included in the study. Table 1. Pathologic parameters and ratios between groups. (μ: Chi-Square test) Pathologic Group-1 Group-2 Group-3 Urethral injury Group-4 Group-5 Total P Value Parameters Sham n(%) Urethral injury + +submucozal PRP injection Urethral injury + Urethral Injury + n(%) All Groupsμ Saline Daily (UI+ PRPs) n(%) PRP X1 (UI+PRPx1) PRP X2 (UI+PRPx2) (UI+PS) n(%) n(%) n(%) Mucosal Inflammation < 0,001 0 2 (22.2%) 0 0 0 0 2 (5%) 1 7 (77.8%) 0 7(100%) 6(60%) 6 (66.7%) 26(62%) 2 0 4 (57.1%) 0 4(40%) 3 (33.3%) 11(26%) 3 0 3 (42.9%) 0 0 0 3 (7%) Spongiofibrosis < 0.001 0 3 (33.3%) 0 0 0 0 3(7.1%) 1 3 (33.3%) 0 3 (42.9%) 8(80%) 4(44.4%) 18(42.9%) 2 3 (33.3%) 4 (57.1%) 4 (57.1%) 2(20%) 5(55.6%) 18(42.9%) 3 0 3 (42.9%) 0 0 0 3(7.1%) Edema 0.627 0 5(55.6%) 3 (42.9%) 2 (28.6%) 3(30%) 2 (22.2%) 15 (35.7%) 1 4(44.4%) 3 (42.9%) 5 (71.4%) 6(60%) 7 (77.8%) 25 (59.5%) 2 0 1 (14.3%) 0 1(10%) 0 2 (4.8%) Serosal Inflammation 0.003 0 6 (66.7%) 3 (42.9%) 0 0 0 9 (21.4%) 1 3 (33.3%) 4 (57.1%) 4 (57.1%) 3(30%) 2(22.2%) 16 (38.1%) 2 0 0 2 (28.6%) 4(40%) 4(44.4%) 10 (23.8%) 3 0 0 1 (14.3%) 3(30%) 3(33.3%) 7 (16.7%) Figure1: The Study protocol A- traumatization of rat’s urethra with pediatric uretrotome, B- Administration of the PRP into the urethra with using a 24 Ga catheter C- Administration of the Submucozal injection of the PRP to the urethra D-Dissection of the rat penis until its proximal part PRP treatment in urethral injury-Aydin et al. Reconstructive Surgery 664 Vol 18 No 6 November-December 2021 665 Preparation of platelet-rich plasma (PRP) Platelet-rich plasma (PRP) was prepared daily from the blood taken from a male (Wistar albino) rat. To take the sample for PRP, blood was taken from the heart under anesthesia and then the animal was euthanized (with the cervical dislocation method). Blood samples were taken in tubes containing sodium citrate (blood/sodium citrate 3.8% = 9:1) and gently mixed. Then the first centrifu- gation procedure (440 xg, 10ı, 20 ℃) was completed. The supernatant was obtained, transferred to a new tube and the second centrifugation was completed (800 xg, 12ı, 20 ℃). After the second centrifugation, nearly 2 ml of the upper section was removed with a pipette. The remaining PRP was gently mixed and platelet count measurement was performed (~2x106/mm3). The measured PRP was used in applications. All procedures were completed under sterile conditions.(13) PRP was prepared fresh before administration and the procedure. The PRP preparation process including taking blood took nearly 60 minutes. Internal urethrotomy model and PRP application In the study, a pediatric internal urethrotomy scalpel was used to induce a urethral injury model and a lon- gitudinal 0.5 cm incision was made in the 12 o’clock direction from 0.5 cm proximal around the urethra to encompass muscles and corpus spongiosum. Then intraurethral instillation was performed with a 22 Ga catheter sheath in the groups. Submucosal PRP injec- tion was performed with a PPD injector (Figure 1). Study Groups At the beginning of the study, 15 rats were separated for preparation of PRP and PRP was prepared daily. Later, 50 rats were randomized into 5 groups, with 10 rats in each group. Group 1 was the sham group and only underwent daily urethral catheterization, Group 2 was given instillation of intraurethral 0.9% saline once a day using a 22 Ga catheter sheath after urethral injury (urethral injury + physiologic saline [(UI+PS]) Group 3 was given submucosal injection of PRP after urethral injury (UI+PRPs). Submucosal PRP was in- jected at 150 microliters (300 million platelets/admin- istration). Group 4 was given instillation of intraurethral PRP once a day using a 22 Ga catheter sheath after urethral injury (UI+PRPx1). PRP was administered into the ure- thra of rats as an instillation and one application of 300 million platelets/150 microliters was given for 15-days duration. Group 5 was given instillation of intraurethral PRP twice a day using a 22 Ga catheter sheath after urethral injury (UI+PRPx2). PRP was administered into the ure- thra of rats as an instillation and two applications of 300 million platelets/150 microliters were given for 15-days duration. Final Evaluation On day 15, the penises of the rats were degloved to perform penectomy. Rat penises were placed in 10% formaldehyde and sent to the pathology department for histopathologic analysis. At the end of the study, 1 rat in the sham group (n = 9), 3 rats in the UI+PS group (n = 7), 3 rats in the UI+PRPs group (n = 7), and 1 rat in the UI+PRPx2 group (n = 9) died due to anesthesia and environmental factors, so the study was completed with the remaining 42 rats. Histopathologic Analysis Histopathologic analysis was performed under light mi- croscope by a single independent pathologist blinded to the study groups. Until the day of macroscopic exami- nation, the urethral tissues were fixed in 10% formalin in a separate dish for each rat. During the macroscopic examination, the tissue samples were cut into squares at 3-mm intervals and embedded in paraffin blocks. Slices of 4-micron thickness were cut from the paraffin blocks and stained with hematoxylin and eosin (HE) and with Masson trichrome for histochemical examination. The preparates were examined under light microscope at x100 and x200 magnification. For the histopathologic examination of the tissues, spongiofibrosis, inflamma- tion, and congestion in vascular structures were evalu- ated. Spongiofibrosis was examined with Masson Tri- Table 2. Histopathological scores of groups and total P values (α Kruskal-Wallis test) Pathologic Parameters Group-1 Group-2 Group-3 Group-4 Group-5 P Value Sham Urethral injury + Urethral injury + Urethral injury + Urethral Injury + All Groupsα (Mean Value ±SD) SF Daily (UI+SF) submucozal PRP PRP X1 PRP X2 (Mean Value ±SD) injection (UI+ PRPs) (UI+PRPx1) (UI+PRPx2) (Mean Value ±SD) (Mean Value ±SD) (Mean Value ±SD) Mucosal Inflammation 0.77 ± 0.44 2.42 ± 0.53 1± 0 1.4 ±0.51 1.33±0.50 < 0.001 Spongiofibrosis 1 ± 0.86 2.42 ± 0.53 1.57 ± 0.53 1.2 ±0.42 1.55±0.52 0.004 Edema 0.44 ± 0.52 0.71 ± 0.75 0.71 ± 0.48 0.8 ±0.63 0.77±0.44 0.664 Serosal Inflammation 0.33 ± 0.50 0.57 ± 0.53 1.57 ± 0.78 2 ± 0.81 2.11±0.78 < 0.001 Pathologic Parameters Sham Sham Vs Sham Vs UI+ Sham Vs UI+PS UI+PRPx1 PRPx2 (p Value)* Vs UI+PRPs (p Value)* (p Value)* (p Value)* Mucosal Inflammation < 0.001 0.012 0.024 0.207 Spongiofibrosis 0.001 0.524 0.12 0.149 Edema 0.414 0.204 0.165 0.312 Serosal Inflammation 0.375 < 0.001 < 0.001 0.002 Table 3. P values between sham group and experiment groups (*Independent t test) PRP treatment in urethral injury-Aydin et al. chrome staining for histochemical examination. Spongiofibrosis was evaluated as 0 = none; 1 + ≤ 10% tissues with fibrosis; 2 + = 10%-49% tissues with fibro- sis; and 3 + ≥ 50% tissues with fibrosis. Inflammation was evaluated as: 0 = none; 1+ = 5-10 lymphocytes/x200 magnification; 2+ = 11-50 lympho- cytes/x200 magnification; and 3 + = > 50 lymphocytes/ x200 magnification. Congestion in vascular structures was calculated by counting the number of vessels with congestion in the tissue at each x100 magnification and dividing this by the number of total x100 magnification areas in the tis- sue: 0: none, 1 + = 1-3, 2 + > 3-6, and 3 + = > 6-10. Hy- peremia and edema were evaluated according to their presence in biopsy samples (Figure 2). While inflammatory cells in subepithelial tissue were assessed for identification of mucosal inflammation, identification of serosal inflammation assessed inflam- matory cells in the tunica adventitia. The results of this assessment identified that rats receiving PRP treatment had fewer inflammatory cells observed in the submu- cosal area compared to the serosal area. All procedures performed in studies involving animals were in accordance with the ethical standards of the in- stitution at which the studies were conducted. Approval for the study was granted by the local ethics committee. The study was performed in the Experimental Animals Laboratory of N.E. Unv. Medical Faculty. (No: 2017- 011) Statistical Analysis Statistical analysis was performed with SPSS, v.23.0 statistical software (SPSS, Inc. Chicago, IL, USA). Chi square tests were used to understand if distributions of categoric variables were different across groups. Cat- egoric variables are described by frequencies and per- centages. Continuous variables are presented as mean and standard deviations. The Independent samples t-test and Kruskal Wallis test were used for the comparison of continuous variables among groups. A p value < 0.05 was considered statistically significant. RESULTS During intraurethral administration, no side effects were observed in rats. During the study, 8 rats died due to anesthesia and environmental factors, while 42 rats survived. Penectomies were performed on the 15th day and rats were sacrificed. Forty-two rats were included in the assessment. Rats included in the assessment were evaluated histopathologically for mucosal inflamma- tion, urethral spongiofibrosis, edema, serosal inflam- mation, and congestion. All sections were monitored for mucosal hemorrhage but this was not scored. Histopathologic assessment was evaluated and com- pared based on percentages and scoring. When all groups are compared with each other, the low- Pathologic Parameters UI+PS UI+PS UI+PS UI+PRPx1 UI+PRPx1 UI+PRPx2 Vs Vs Vs Vs Vs Vs UI+PRPx1 UI+PRPx2 UI+PRPs UI+PRPx2 UI+PRPs UI+PRPs (p Value)* (p Value)* (p Value)* (p Value)* (p Value)* (p Value)* Mucosal Inflammation 0.001 0.001 < 0.001 0.779 0.061 0.102 Spongiofibrosis < 0.001 0.006 0.011 0.121 0.130 0.953 Edema 0.803 0.836 1.0 0.931 0.768 0.789 Serosal Inflammation 0.001 0.001 0.017 0.766 0.297 0.193 Table 4. P values between experiment groups (*Independent t test) Figure 2. H&E,X100;Subepithelial, mucosal fibrosis and inflammation, A) 0.9% saline group, B) PRPx1 group, C) PRPx2 group, D) PRPs group; The urethral wall layer is shown with black arrow and line. H-E, X400; inflammation in the serosal section above the wall layer (black line and arrow) E) 0.9% saline group ( red arrow), F) PRPx1 group ( red arrow), G) PRPx2 group(red arrow) H) PRPs Group (Red arrow) PRP treatment in urethral injury-Aydin et al. Reconstructive Surgery 666 Vol 18 No 6 November-December 2021 667 est values for mucosal inflammation, spongiofibrosis, edema, and serosal inflammation were measured in the sham group, while the highest values for mucosal inflammation, spongiofibrosis, and edema were meas- ured in the UI+PS (0.9% saline) group. For serosal inflammation, the highest value was measured in the UI+PRPx2 group. When all groups are compared, there were significant differences found for mucosal inflam- mation, spongiofibrosis, and serosal inflammation. No significant difference was identified for edema. The analyses of percentages and scoring for the groups are shown in Table 1. The sham group was identified to have the lowest score values for all histopathologic parameters. Data for com- parisons between the sham group and other groups are shown in Table 2. The urethral injury+ 0.9% saline (UI+PS) group was observed to have the highest values in terms of mucosal inflammation, spongiofibrosis, and edema. When the UI+PS group is compared with the PRP groups, mucosal inflammation and spongiofibrosis were observed to be significantly greater in the UI+PS group. The highest significant difference for spongi- ofibrosis was identified in the UI+PRPx1 group. There were no significant differences between the UI+PS group and the PRP groups in terms of edema. When the UI+PS group is compared with the PRP groups in terms of serosal inflammation, it was signif- icantly less in the UI+PS group compared to all PRP groups. When the PRP groups (UI+PRPx1, UI+PRPx2, UI+PRPs) are compared with each other, there were no significant differences observed in terms of mucosal inflammation, spongiofibrosis, edema, and serosal in- flammation. However, mucosal inflammation and se- rosal inflammation were observed to be lower in the UI+PRPs group, while spongiofibrosis was less in the UI+PRPx1 group (Table 3). Urethral congestion was observed to be similar in all groups and no differences were identified. DISCUSSION Urethra stricture is a disease with high cost disrupting quality of life and with frequent recurrence. There are many factors in the etiology led by trauma, urethra in- fections, cardiac surgeries, endoscopic interventions or Foley catheter insertion. With the increase in endo- scopic treatment especially in recent years, there is an increase in the incidence of iatrogenic urethra stricture. (14) After urethra stricture has formed once, it has high recurrence rates and may be treated with repeated mini- mal invasive procedures, self-dilatation and/or complex surgeries like urethroplasty.(15-17) As a result, it is very important to find a medical treatment modality that will prevent the formation of urethra stricture and/or length- en recurrence duration. There is still no medical treat- ment available in spite of the increase in the prevalence of urethra stricture in recent years, the effect on patient quality of life, and high cost, with experimental appli- cations not going beyond preventive agents. When the literature is examined, many agents have been trialed for the prevention of urethra stricture and different ad- ministration methods have been used. Administration methods vary according to the effect mechanism of the agent; however, to date, there is no study about the ad- ministration method and administration frequency for a certain agent. In our study, different from the literature, the efficacy of PRP administration was compared in terms of administration route and dose for the first time. As expected, intraurethral PRP treatment was shown to be protective against urethral stricture, with the patho- logic assessment results of the PRP groups determined to be superior to the sham and saline groups. Though no significant difference was identified for pathologic assessment of the PRP subgroups of UI+PRPx1, UI+PRPx2 and UI+PRPs, interestingly the UI+PRPx1 group had the lowest spongiofibrosis scores. The lowest scores for serosal and mucosal inflammation were identified in the UI+PRPs group. Based on these results, we believe that more than one administration of PRP is not superior. The low incidence of spongiofi- brosis especially leads to the consideration that intrau- rethral and single-dose administration of PRP may be more effective to prevent urethral stricture. Urethra stricture was identified to have a high recur- rence risk due to abnormal fibrosis increase.(7) Studies observed fibrotic areas causing urethral stricture have 32% increases in type 3 collagen concentrations.(18) To prevent this abnormal increase in fibrosis, a variety of experimental and clinical studies were performed about the administration of medications or materials with an- tifibrotic effects.(19-21) The first studies on the prevention of urethra stricture clinically administered steroid treat- ments like triamcinolone, but were not very successful. (20,22) In rat models, periurethral botox-A injection, mi- tomycin-c, and dexpanthenol instillation were adminis- tered and the 3 agents were shown to reduce fibrosis and inflammation.(19,23,24) In fact, mitomycin-c was clinically injected in the submucosa in anterior urethra stenosis and shown to reduce fibrosis.(25) The increasing costs of urethral stricture continue to be a focus of interest. In clinical studies, caprotil gel, halofuginone, hyaluronic acid, and carboxymethyl cellulose were identified to re- duce the recurrence of stenosis and postoperative pain when administered as instillations. (21,26,27) As seen in the literature, clinical and animal studies were performed with many agents and different methods, and different administration methods were used and all were shown to be effective in different studies. However, there is no study showing which administration method is more effective in a single study. Additionally, none of these treatments have entered routine use to prevent urethral stricture. Platelet-rich plasma (PRP) contains high amounts of growth factors. The most important of these growth fac- tors is platelet-derived growth factor (PDGF), which is a factor repairing connective tissue and initiating wound healing. PDGF is the first factor initiating processes including mitogenesis, angiogenesis and macrophage activation. Many growth factors contained in PRP in- crease the speed of regenerative processes and reduce inflammatory factors, reducing fibrosis development. Studies with autologous PRP showed that PRP increas- es the rate of wound healing, closes wounds more eas- ily in open diabetic wounds and reduces inflammation. Due to these effects, autologous PRP is routinely used in many clinics like plastic surgery and orthopedics.(10- 12,17,22-24) Autologous PRP contains many growth factors like endothelial growth factor, insulin-like growth fac- tor, transforming growth factor and fibroblast growth factor expressed by mesenchymal stem cells. These growth factors prevent excessive accumulation of type PRP treatment in urethral injury-Aydin et al. PRP treatment in urethral injury-Aydin et al. 3 collagen in tissues reducing fibrosis development. Linked to the effect of these growth factors, PRP was shown to be effective for the prevention of fibrosis fol- lowing urethral injury.(28,29) Tavukçu et al. administered PRP into the urethras of rats with induced experimental urethra injury and determined that it reduced type 3 col- lagen synthesis in urethra stenosis and protected against fibrosis.(28) However, no study was performed with PRP or any other agent using different administration meth- ods and numbers of administrations like urethral instil- lation and submucosal injection to identify the optimal treatment protocol. This study compared the protective effect of PRP with intraurethral and submucosal administration for urethral stricture developing after iatrogenic induced urethra trauma. In conclusion, PRP was seen to signif- icantly reduce urethral spongiofibrosis independent of the method of administration. In the three PRP groups, PRPs, PRPx1, and PRPx2, spongiofibrosis was identified to be low, with spong- iofibrosis score lowest in the PRPx1 group and highest in the PRPs group. Additionally, the PRP group with instillation 1 time per day had lower score values for urethral fibrosis than the PRP group with instillation 2 times per day; however, there was no statistical differ- ence identified. This situation shows that the increase in the number of PRP administrations was not effective for protection from stenosis, and that a single dose was sufficient. There are a range of studies about wound healing relat- ed to PRP. Massara et al.(10) showed PRP has increasing effect on healing in ischemic and diabetic foot wounds. Nikopulos et al.(11) performed a study showing the effi- cacy of PRP use for pubourethral ligament restoration in stress urinary incontinence. Guinot et al.(12) used a platelet-rich fibrin membrane for closure after urethro- plasty for distal hypospadias and there are publications about reduced fistula development. Arnalich et al.(30) used solid PRP as OSD in the eye and showed it was an effective and safe preparate for corneal ulcers and per- forations in eye surgery. Mohammadi et al.(31) showed effective wound healing in rats. As seen in these studies, PRP was even used in the eye and positively affected wound healing and reduced fi- brosis due to containing many growth factors without identified side effects. In our study, it was identified to be more effective on fibrosis when administered as ure- thral instillation. In this study, the efficacy of PRP administered as in- traurethral instillation 1 and 2 times per day and as sub- mucosal injection 1 time per day was compared in rats with urethral injury. When compared with intraurethral 0.9% saline instillation after urethra injury, all PRP groups were identified to have significant degrees of re- duction in mucosal inflammation and urethral fibrosis. PRP is a current topic, coming to the fore as a cheap and easily applicable method without autologous side effect profile. In our study, the administration method in rats with experimental urethra injury induced was compared with the UI+PS group. In our study, all administration methods for PRP were identified to be effective, aid in healing urethral tissue and reduce inflammation param- eters. When the administration route is compared, ad- ministration as urethral instillation 1 time per day was most effective on spongiofibrosis and reduced it most. As a result, it is considered that this method may be chosen for clinical administration due to ease of admin- istration to patients. In summary, PRP affects synthesis of type 3 collagen especially and increases normal wound healing due to containing many growth factors. It is a simple, cheap, and effective preparate with no side effects that can be obtained by autologous means routinely used in other disciplines in medical practice. It may be used as rou- tine instillation to protect against iatrogenic urethra stricture and/or to prevent recurrence after treatment. PRP administered through intraurethral instillation and submucosal route is a promising preparate that may pre- vent the development of fibrosis and inflammation as a result of urethral injury and increase the speed of nor- mal urethral healing. However, administration of PRP as instillation 1 time per day was observed to be more effective than submucosal administration and adminis- tration as instillation 2 times per day in our study. Ad- ministration of PRP as 1 daily intraurethral instillation to protect against urethral stricture may be chosen due to easy application. However, there is a need for clinical and experimental studies about the long-term outcomes to better evaluate the effect of PRP. The most important limitation of the study is the short follow-up period for an animal experiment. This fol- low-up duration was not sufficiently long to determine fibrosis that may develop in the long term and possible side effects. CONFLICT OF INTEREST None of the authors have any potential conflict of in- terest. REFERENCES 1. McCammon KA, Zuckerman JM, Jordan GH. Surgery of the penis and urethra. In: Wein AJ, Kavoussi LR, Partin AW,Peters CA,eds. Campbell-Walsh Urology 11th ed. Philadelphia:Elsevier;2016;40:907–45.e4. 2. Das SK, Jana D, Ghosh B, et al. 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