Effects of biodegradable self‐reinforced polyglycolic acid, poly‐dl‐lactic acid and stainless‐steel spiral stents on uroepithelium after Nd:YAG laser irradiation of the canine prostate

Abstract

Objective To evaluate the safety and tissue effects on canine uroepithelium and prostate of biodegradable self‐reinforced polyglycolic acid (SR‐PGA) and self‐reinforced poly‐dl‐lactic acid (SR‐PLA) spiral stents compared to stainless‐steel (SS) spiral stents. Material and methods Twenty‐five dogs (median body weight 12 kg) underwent a one‐stage midline laparotomy and cystotomy. A side‐firing Nd:YAG laser fibre was placed in the prostatic urethra antegradely and laser power applied at a setting of 20 W for 10 s in each side lobe, followed by dilatation to 4 mm diameter and insertion of a spiral stent. Dogs were randomized to receive an SR‐PGA, SR‐PLA or SS stent and no catheter was placed post‐operatively. The dogs were killed after a follow‐up of 1, 3 or 6 months and the bladder, prostate and urethra removed. Routine histological sections were prepared from the bladder, prostate, the proximal urethra immediately below the prostate and the distal urethra. Results Histological examination showed a mild to moderate foreign‐body reaction and an acute inflammatory reaction after 1 month in the SR‐PGA and the SR‐PLA groups. The tissue effect was minimal in the SR‐PGA group after 6 and 12 months. The SS stent group had more fibrosis, chronic inflammation and oedema at all follow‐up assessments. There were erosions of the epithelium with subepithelial oedema in the animals with the SS stent. No dysplasia was detected and some remnants of the suture material were evident in the area of the cystotomy closure. There was one stricture at the apex of prostate in the SR‐PGA group at 3 months in one re‐operated dog. Conclusion The histopathological changes in tissues caused by SR‐PGA and SR‐PLA stents were generally minor and decreased during the follow‐up. The biocompatibility of SR‐PGA and SR‐PLA stents was good when combined with Nd:YAG laser treatment of the prostate.

Biodegradable urethral stents

“…In an animal study Kemppainen et al [31] reported fewer encrustations on SR‐PLLA stents than on stainless steel stents in the anterior urethra of the rabbit. Likewise Petas et al [35,40] found some encrustation on gold‐plated steel wire (Prostakath®), but none on SR‐PGA or SR‐PLA 96/4 stents after incubation for 2 weeks in artificial urine. Recently a SR‐PLGA80/20 stent was shown to be markedly more resistant to encrustation than metallic urethral stents [41].…”

Preliminary biocompatibility experiment of polymer films for laser‐assisted tissue welding

“…Zieren et al using a PGA mesh in combination with fibrin glue, found no infections after 90 days in a rat abdominal repair [40]. Petas et al compared stents made of PLA, PGA, and stainless-steel implanted in canine prostatic urethra after 10 seconds irradiation of the prostate side lobes with a 20 W CW Nd:YAG laser [41]. Examination of specimens after 1, 3, and 6 months showed a mild acute inflammation and foreign body reaction with the PLA and PGA stents that decreased over time.…”

Drug-Eluting Bioresorbable Stents for Various Applications

“…In clinical studies, researchers have used biodegradable stents to treat benign prostatic hyperplasia. The results obtained yield more positive outcomes compared with those using suprapublic catheters (39)(40)(41)(42)(43). Selfreinforced poly(l-lactic acid) (PLLA) bioresorbable spiral stents are also undergoing evaluation for use in the anterior and posterior urethra and in the upper urinary tract for preventing urinary retention and for repairing local urethral trauma or defects (44,45).…”