Drug-eluting bioabsorbable stents - an in vitro study.

The aim of this study was to investigate the drug elution properties of novel drug-eluting bioabsorbable stents in vitro with four different drugs: dexamethasone, indomethacin, simvastatin and ciprofloxacin. Braided stents of poly-lactic acid (96l/4d) fibers were coated with a solution containing the appropriate bioabsorbable polymer and drug, with acetone as the solvent. Two different drug concentrations for both non-sterile and gamma sterilized stents were used for dexamethasone and indomethacin. For ciprofloxacin and simvastatin, only one drug dose was used. The stents were placed in sodium-phosphate-buffered saline in a shaking incubator (pH 7.4, +37 degrees C) and the eluted drug was measured periodically using an ultraviolet spectrometer. The drugs were hydrophobic to different degrees, as demonstrated by their various speeds of elution. In general, the higher the drug load in the stent, the faster the drug elution and the more hydrophilic the elution profile. In the cases of dexamethasone, indomethacin and ciprofloxacin, the sterilization decreased the drug elution rate slightly and the elution started earlier. However, in the case of ciprofloxacin, the gamma sterilization increased the drug elution rate slightly. Sustained elution was achieved for all four drugs. It was also evident that both the concentration and the hydrophility of the drug had a great influence on the drug elution profile. Gamma sterilization modified the drug elution profiles of dexamethasone, indomethacin and simvastatin, but had little effect on the drug elution profile of ciprofloxacin compared to three other drugs.

Expression of Ki-67, cyclin D1 and apoptosis markers correlated with survival in prostate cancer patients treated by radical prostatectomy.

OBJECTIVE: The study was designed to analyse the prognostic value of proliferation markers Ki-67 and cyclin D1 and apoptosis in prostate cancer (PC) patients treated by radical prostatectomy. PATIENTS AND METHODS: Two hundred and eleven patients treated by radical prostatectomy for localised prostate cancer were clinically followed up for a mean of 7.3 years. The primary histopathological specimens were re-analysed to ensure uniform histoplthological grading and pT classification. A tissue microarray construction (TMA) was used in immunohistochemisty to assess the expression of Ki-67, cyclin D1 and the apoptosis marker Tag. The results were analysed with light microscopy and the findings were compared to standard histology, pT and clinical follow-up data. RESULTS: The co-expression of Ki-67 and cyclin Dl (p=0.05) was common. High fraction of Ki-67 positive cells and a high fraction of apoptotic cells were often present in same tumours (p=0.05). High apoptotic rate was related to positive surgical margin status (p=0.047). Low expression of Ki-67 was related to a low Gleason score (p<0.001), an absence of either capsule penetration (p = 0.029) or perineural invasion (p=0.004). High expression of cyclin Dl was related to perineural growth (p=0.039). Prostate specific antigen (PSA) recurrence-free survival (RFS) was predicted by Gleason grade (p<0.001) and capsule invasion (p=0.006). High expression of Ki-67 (p=0.03), as well as high apoptotic rate (p=0.04) were related to a high risk of cancer death. In multivariate analysis the seminal vesicle invasion was the only independent predictor of cancer death (p = 0.01). CONCLUSION: The expression of Ki-67, cyclin D1 and a high apoptotic rate are related to a malignant phenotype in prostate cancer, but their prognostic value is inferior to standard histological prognostic factors.

Reduced alpha- and beta-catenin expression predicts shortened survival in local prostate cancer.

UNLABELLED: The aim of this study was to determine the prognostic value of alpha- and beta-catenin expressions in local prostate cancer (PC). MATERIALS AND METHODS: One hundred and eighty-one PC patients treated with radical prostatectomy were followed-up for a mean of 7.3 years. The alpha- and beta-catenin expression were analysed by immunohistochemistry TMT (tissue microarray technique) and light microscopy. RESULTS: Strong a-catenin expression was related to low Gleason grade (p < 0.001), cancer-free seminal vesicles (p = 0.04) and low preoperative PSA (p = 0.02). Strong beta-catenin expression was related to low Gleason grade (p < 0.001) and cancer-free seminal vesicle status (p = 0.03). Absence of nuclear beta-catenin expression was related to local disease (pT1-T2) (p = 0.05). alpha-catenin (p = 0.06), beta-catenin (p = 0.05), Gleason grade (p = 0.03) and capsular invasion (p = 0.01) were related to PSA recurrence in patients who reached PSA zero postoperatively. PSA recurrence-free survival (RFS) was significantly related to Gleason grade (p < 0.001), capsule invasion (p = 0.01), perineural growth (p = 0.05) and preoperative PSA (p = 0.05). In Cox's analysis, independent predictors of PSA RFS were Gleason grade (p < 0.001) and capsular invasion (p = 0.006). Low expressions of alpha- (p = 0.06) and beta-catenin (p = 0.05) were related to shortened PSA RFS. Survival was related to low alpha- (p = 0.011) and beta-catenin (p = 0.016) expressions. Independent predictors of shortened survival were seminal vesicle invasion (p = 0.016) and low alpha-catenin expression (p = 0.049). CONCLUSION: Reduced alpha- or beta-catenin expressions are related to malignant phenotype in local prostate cancer and predict PSA failure as well as shortened survival.

Viscoelastic memory and self-expansion of self-reinforced bioabsorbable stents.

The possibility to decide the speed and rate of expansion of stents is of great clinical importance by reason of the varying requirements for different indications to use stents. Self-reinforced bioabsorbable stents can be made self-expanding owing to the viscoelastic memory of the material. Stents are stable at room temperature and expansion occurs at body temperature. The level at which the expansion stops depends on the material, crystallinity, initial diameter of spira and annealing temperature. The expansion rate can be estimated by logarithmic equation, if material, draw ratio and diameter of stent wire are constant. This is, however, possible only if processing parameters are constant. Based on the present results annealing temperature and expansion time were seen to be directly proportional to the expansion rate of the stent.

A bioabsorbable self-expandable, self-reinforced poly-L-lactic acid urethral stent for recurrent urethral strictures: long-term results.

BACKGROUND AND PURPOSE: Biodegradable urethral stents have been used clinically for some years mainly in order to prevent postoperative urinary retention after minimally invasive thermotreatment of benign prostatic hyperplasia. We previously reported a 15-month-follow-up pilot study of a bioabsorbable self-expandable, self-reinforced poly-L-lactic acid (SR-PLLA) urethral stent in combination with optical urethrotomy in the treatment of recurrent urethral strictures. The present aim was to evaluate the long-term results of this new treatment modality. PATIENTS AND METHODS: A series of 22 patients with severe urethral strictures (mean number of earlier urethrotomies 2.5) were involved. An SR-PLLA spiral stent with a bioabsorption time of 10 to 12 months was inserted into the urethra at the stricture site immediately after optical urethrotomy. Uroflowmetry, measurement of postvoiding residual urine, urine culture, and urethroscopy were performed preoperatively and at 1 and 3 months and then every 3 months up to 12 months, with subsequent follow-up visits every 6 months. The mean follow-up was 46 months. RESULTS: The treatment was successful in 8 of the 22 patients (36%). Six recurrences were found within the stented area and 15 outside. Patients with failure have since been treated with several urethrotomies and repeat self-dilatations or free skin urethroplasties. CONCLUSIONS: The results of the use of a bioabsorbable SR-PLLA urethral stent for the treatment of recurrent strictures were encouraging. Without this additional therapy, the recurrence rate of strictures might have been much higher. The main problem was sudden collapse of the stent, possibly induced by outer compression. A new generation of bioabsorbable stents is already under development.

Expansion and bioabsorption of the self-reinforced lactic and glycolic acid copolymer prostatic spiral stent.

PURPOSE: Self-reinforced bioabsorbable stents can be made self-expanding due to the viscoelastic memory of the oriented bioabsorbable materials. A new self-expandable self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80:20 stent was developed to prevent postoperative urinary retention after procedures that induced prostatic edema. In in vitro experiments the expansion rate has been up to 100% during the first few hours at body temperature. We investigated the expansion rate and biodegradation of the self-reinforced lactic and glycolic acid copolymer prostatic spiral stent in vivo in the prostatic urethra. MATERIALS AND METHODS: A total of 39 men, 52 to 84 years old, with lower urinary tract symptoms due to benign prostatic enlargement underwent interstitial laser coagulation of the prostate. A self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was inserted into the prostatic urethra at the end of the operation. The stent lumen diameter was 4.5 mm. The location and diameter of the lumen and degradation of the stent were studied with transrectal ultrasound at 1, 2, 4 and 6 months postoperatively. At 6 months patients underwent cystoscopy. RESULTS: All except 1 patient voided on postoperative day 1. Mean lumen diameter was 7.4 mm. (range 6.2 to 8.2) at 1 month and 7.2 mm (range 6.2 to 7.5) at 2 months. At 4 months the stent was degraded into small pieces. No pieces of stent were found in the prostatic urethra on ultrasound or cystoscopy at 6 months. However, a portion of the spiral stent was found at the bottom of the bladder in 2 patients. CONCLUSIONS: The speed and expansion rate of the self-reinforced copolymer of lactic/glycolic acid, lactic/glycolic molar ratio 80/20 stent was sufficient to lock the stent in place and ensure voiding in cases of edema induced bladder outlet obstruction. Strength retention greater than 2 months was long enough to avoid later impairments of voiding.

A double-blind, randomized, placebo-controlled pilot study to investigate the effects of finasteride combined with a biodegradable self-reinforced poly L-lactic acid spiral stent in patients with urinary retention caused by bladder outlet obstruction from benign prostatic hyperplasia.

OBJECTIVE: To assess whether patients in acute urinary retention from benign prostatic enlargement can be treated with a combined therapy comprising finasteride and a bioabsorbable self-reinforced poly L-lactic acid (SR-PLLA) urethral stent. PATIENTS AND METHODS: Fifty-five patients in acute urinary retention were treated as outpatients; they had a suprapubic catheter inserted and the SR-PLLA stent placed cystoscopically. After 2 weeks the patients were randomized to receive either finasteride 5 mg daily or placebo. They were assessed at baseline and at 6, 12 and 18 months for maximum urinary flow rate, prostate volume and serum prostate-specific antigen (PSA). RESULTS: Nineteen patients completed the study while 36 discontinued. There was a statistically significant increase in the mean maximum flow rate, and a statistically significant decrease in the prostatic volume and serum PSA in the finasteride group. The same number of patients discontinued in both groups; the major reason for discontinuation was insufficient therapeutic response. CONCLUSIONS: The major problems were discontinuation of treatment because the response to therapy was insufficient, and uncontrolled breakdown of the spiral stent. To solve these problems, new configurations of bioabsorbable stents are needed.

A randomised study to evaluate the efficacy of a biodegradable stent in the prevention of postoperative urinary retention after interstitial laser coagulation of the prostate.

OBJECTIVE: Interstitial laser coagulation (ILC) of the prostate induces necrosis, oedema and increased risk for postoperative urinary retention. The present randomized study was carried out to investigate the feasibility and efficacy of a biodegradable self-reinforced polyglycolic acid (SR-PGA) stent in preventing postoperative urinary retention and the need for prolonged catheterization after ILC treatment. MATERIAL AND METHODS: 35 males with benign prostatic enlargement (BPE) entered the study: 21 in the ILC + stent group and 14 in the ILC group without a stent. A suprapubic catheter was inserted for all patients and ILC was performed. The SR-PGA stent was inserted immediately after laser therapy in the stent group and kept open until the next morning when it was closed and the patient started trying to void. The suprapubic catheter was removed after voiding had started and the urinary bladder emptied adequately. RESULTS: In the ILC + stent group voiding started on the first postoperative day in 17 patients and on the second day in 2 patients. Voiding was delayed in 2 cases: in 1 case due to inadequate length of the stent and in the other as a result of the stent placement being too proximal. There was 1 case of urinary retention due to early degradation of the stent. In the ILC-only group voiding started on average 6.1 days postoperatively. At 1 month follow-up, the mean peak urinary flow rate had increased significantly in the ILC + stent group (p < 0.05) but not in the ILC-only group (p = 0.26). Improvements in symptom scores were significant in both groups (p < 0.005) but in terms of the mean peak urinary flow rates at 6 months follow-up the improvement was significant only in the stent group (p < 0.05). CONCLUSIONS: The use of a SR-PGA stent enabled early voiding and is safe and effective in the treatment of postoperative urinary retention after ILC. The 3-4 week degradation time of the SR-PGA stent was too short for some patients. There is still a need for further development work to improve the stents and larger controlled studies to show the true value of biodegradable stents in the treatment of BPE.

A pilot study of a bioabsorbable self-reinforced poly L-lactic acid urethral stent combined with finasteride in the treatment of acute urinary retention from benign prostatic enlargement.

OBJECTIVE: To assess whether patients with acute urinary retention from benign prostatic enlargement can be treated with a combined therapy comprising a bioabsorbable self-reinforced poly L-lactic acid (SR-PLLA) urethral stent and finasteride. PATIENTS AND METHODS: Eleven men in acute urinary retention were treated as outpatients; they had a suprapubic catheter inserted and the SR-PLLA stent placed cystoscopically. The patients were allowed to attempt to void spontaneously after 2 days. RESULTS: All patients started to void spontaneously within 2 weeks. There was a steady improvement in urinary flow rates up to 9 months, followed by a slight impairment after the bioabsorption of the stent. During the mean (range) follow-up of 24 (23-26) months only three patients required surgical treatment. CONCLUSION: The bioabsorbable SR-PLLA stent combined with finasteride therapy provides a promising new alternative in the treatment of acute urinary retention, especially in patients unfit for surgical therapy. Larger, placebo-controlled studies are needed to establish the efficacy of this combined therapy.

Tissue biocompatibility of a new caprolactone-coated self-reinforced self-expandable poly-L-lactic acid bioabsorbable urethral stent.

BACKGROUND AND PURPOSE: The bioabsorption time as well as other properties of bioabsorbable polymers can be affected by the choice of the basic molecule, by the degree of its polymerization, and by the coating material used in the device. The aim of our present study was to evaluate the biocompatibility of a new caprolactone copolymer-coated, self-reinforced poly-L-lactic acid (SR-PLLA) urethral stent by means of a rabbit muscle implantation test. This new material has previously been tested for cytotoxicity using the thymidine incorporation method (DNA synthesis inhibition test), no toxicity being evidenced. MATERIALS AND METHODS: Fifteen male rabbits were used as experimental animals. Rods made from pure lactic acid, pure caprolactone copolymer, and caprolactone-coated lactic acid were placed on both sides of the dorsal muscles, eight implants per rabbit. Rods made from latex and silicone were used as positive and negative controls, respectively. The animals were sacrificed after 1 week, 1 month, or 6 months. Tissue reactions around the implants were analyzed and scored semiquantitatively. RESULTS: Acute tissue reactions attributable to operative trauma were seen in all specimens at 1 week. After 6 months, chronic inflammatory changes and foreign-body reactions were seen only in the positive controls. CONCLUSION: The new caprolactone copolymer material is highly biocompatible.

Biocompatibility testing of a new bioabsorbable X-ray positive SR-PLA 96/4 urethral stent.

PURPOSE: Recently a first X-ray-positive bioabsorbable urethral stent was developed by our group. The stent is made from self-reinforced poly-L,D-lactic acid (SR-PLA 96/4) blended with barium sulfate. The aim of this study was to evaluate the biocompatibility properties of the new stent materials. MATERIALS AND METHODS: Rods made from pure SR-PLA 96/4 and SR-PLA 96/4 blended with barium sulfate were inserted into the dorsal muscles of a rabbit. Rods made from latex and silicone were used as positive and negative controls. To evaluate the long-term effect of BASO4 after the bioabsorption of the polymer, fast degrading SR-PGA (self-reinforced polyglycolic acid) and SR-PLA + BASO4 rods were used as controls. Urethral stents made from SR-PLA 96/4 and X-ray-positive SR-PLA 96/4 stents were inserted cystoscopically into the rabbit urethra. Metal stents were used as controls. The animals were sacrificed after 1 week, 1 month or 6 months. RESULTS: In the muscle implantation samples acute tissue reactions due to operative trauma were seen in all specimens at 1 week. After 6 months chronic inflammatory changes and foreign body reaction were seen only in the positive controls. The stent worked well in the rabbit urethra, its biocompatibility was good and there was less encrustation than in the metal stents. CONCLUSIONS: This first X-ray-positive bioabsorbable urethral stent showed no toxic tissue effects.

Cytotoxicity testing of a new caprolactone-coated self-expanding bioabsorbable self-reinforced poly-L-lactic acid urethral stent.

Forty to 75% of strictures recur within 2 years of urethrotomy and the essential problem remains how to prevent the edges of the cut stricture from adhering to each other and the scar from shrinking. To solve this problem different kinds of urethral stents have been used. Recently a new bioabsorbable self-expanding urethral stent was developed by our group. The core consists of self-reinforced (SR) poly-L-lactic acid (PLLA) and the coating is made of an amorphous copolymer of caprolactone and D,L-lactic acid [P(epsilon-CL/ D,L-LA)]. The aim of our present study was to test the cytotoxicity of the new material used to coat the SR-PLLA urethral stent utilizing the thymidine incorporation method (DNA synthesis inhibition test). The new materials showed no acute toxicity and can be regarded as biocompatible in medical devices.

A bioabsorbable self-expandable, self-reinforced poly-l-lactic acid urethral stent for recurrent urethral strictures: a preliminary report.

PURPOSE: We studied whether a new bioabsorbable self-expandable, self-retaining and self-reinforced poly-l-lactic acid double spiral stent is able to prevent the edges of a cut recurrent urethral stricture from adhering together and the scar from shrinking, thus obviating stricture recurrence. MATERIALS AND METHODS: A bioabsorbable spiral stent was inserted into the stricture site in the urethra immediately after optical urethrotomy in 22 patients with recurrent urethral stricture. Uroflowmetry, measurement of residual urine volume, urine culture and urethroscopy were performed before and 1, 3, 6 and 12 months after optical urethrotomy. RESULTS: All 22 patients voided freely on day 1 or 2 after urethrotomy. The stent slipped partially proximal to the stricture and had to be changed in only 1 patient. The stent was totally epithelialized in all but 1 patient at 6 months and had degraded in all at 12 months. The improvement in flow rate was maintained during followup except in 10 patients with stricture recurrence, which was outside the stent area usually close to the external sphincter in 7 and in the stent area in 3. All recurrences were treated with repeat optical urethrotomy and a new stent was inserted. Urinary infections developed in 2 patients and were successfully treated with oral antibiotics. CONCLUSIONS: The self-expandable self-reinforced poly-l-lactic acid double spiral stent is a promising new method in the treatment of recurrent urethral strictures. There is no need to remove the device and no foreign material remains in the urethra. However, longer followup and controlled studies are needed to evaluate all benefits and side effects of this new treatment modality.

Outcome and clinical signs of arthroscopically graded patellar chondromalacia with or without lateral release.

In a follow-up study of 67 patients with an arthroscopically diagnosed patellar chondromalacia, we compared the results of plain conservative treatment with those after an open lateral retinacular release. The mean follow-up was 35 months. In Grade I chondromalacia the lateral release did not affect the result, which was in all cases good or excellent. In Grade II to IV chondromalacia the lateral release appeared beneficial, although the difference did not reach statistical significance. We also examined the validity of three clinical signs in arthroscopically verified patellar chondromalacia. Patellar inhibition and tracking tests were clearly more sensitive than the lateral apprehension test, which often gave a false negative result. If the patellar inhibition test is positive and a Grade II to IV chondromalacia of the patella is found at arthroscopy, lateral release should be considered among other procedures, like patellar shaving or patellar resurfacing.