Gilad E. Amiel

Functional small-diameter neovessels created using endothelial progenitor cells expanded ex vivo

Arterial conduits are increasingly preferred for surgical bypass because of inherent functional properties conferred by arterial endothelial cells, especially nitric oxide production in response to physiologic stimuli. Here we tested whether endothelial progenitor cells (EPCs) can replace arterial endothelial cells and promote patency in tissue-engineered small-diameter blood vessels (4 mm). We isolated EPCs from peripheral blood of sheep, expanded them ex vivo and then seeded them on decellularized porcine iliac vessels. EPC-seeded grafts remained patent for 130 days as a carotid interposition graft in sheep, whereas non-seeded grafts occluded within 15 days. The EPC-explanted grafts exhibited contractile activity and nitric-oxide–mediated vascular relaxation that were similar to native carotid arteries. These results indicate that EPCs can function similarly to arterial endothelial cells and thereby confer longer vascular-graft survival. Due to their unique properties, EPCs might have other general applications for tissue-engineered structures and in treating vascular diseases.

Current and future modalities for functional renal replacement

Approximately 310,000 Americans suffer from end-stage renal disease, with more than 70,000 new cases reported each year. Advances in immunosuppressive therapy for transplanted patients, in addition to the refined care of patients who are dependent on dialysis, have led to an improved survival for patients with renal failure. Structural, molecular, and pharmacologic developments continue to enhance the efficacy and safety of dialysis in the future. In addition, progressive improvements in the past 2 decades in organ transplantation, a greater insight into the immunobiology of graft rejection, and better surgical and medical management have resulted in improved outcomes. Although renal xenotransplantation is still in its early stages of development, additional research is leading this technology forward. Recent successes in harvesting and expanding renal cells in vitro and the development of biologically active synthetic materials allow for the creation of three-dimensional functioning renal units, which, in the future, may be applied ex vivo or in vivo for partial or full replacement of kidney function.

Renal therapy using tissue-engineered constructs and gene delivery.

Abstract Currently available renal replacement therapies are not optimal for most patients. In addition to the inherent shortage of transplant organs, significant complications are associated with renal transplantation and immunosuppressive therapy. Dialysis neglects the resorptive, homeostatic, metabolic, and endocrinologic functions of the kidney and only partially replaces its filtration properties, resulting in morbidity and mortality. Application of tissue-engineering techniques may improve many aspects of renal function replacement. Identification of the growth factors capable of directing tissue development and of the technique to be used for their delivery would aid in the engineering of human tissue. The combination of tissue-engineering strategies with gene therapy might allow the transfection of diseased tissues with designated cDNA to eliminate inherent or acquired defects. Devices that have been targeted at replacing a single aspect of renal function, in addition to three-dimensional renal units that are capable of excreting urine-like solutes, have been used experimentally. Combination of these strategies may allow the formation of tissue-engineered kidneys in the future.

TISSUE ENGINEERED STENTS CREATED FROM CHONDROCYTES

PURPOSEnTrauma, operations or instrumentation of the urethra or ureter may lead to stricture disease. The use of a natural urethral stent made of autologous tissue would be advantageous due to its biocompatibility. In this study we investigated the feasibility of engineering cartilage stents in vitro and in vivo.nnnMATERIALS AND METHODSnWe fabricated 40 cylinders 10 mm. long with an inner and outer diameter of 5 and 9 mm., respectively, from polyglycolic acid mesh coated with 50:50 polylactic-co-glycolic acid. Chondrocytes isolated from bovine shoulders were seeded onto the tubular polymer scaffolds at a seeding density of 60 x 106 cells per ml. Scanning electron microscopy was performed to determine the even distribution of chondrocytes throughout the polymer scaffolds. We implanted 20 cylinders under the skin of nude mice and 20 were cultured in stirred bio-reactors. Cytological characteristics, collagen content and mechanical durability were evaluated 4 and 10 weeks after cell seeding.nnnRESULTSnGross examination of the engineered stents showed the solid, glistening appearance of cartilaginous tissue. Cytological analyses with hematoxylin and eosin, trichrome, alcian blue and safranin O confirmed cartilage, and the deposition of collagen and glycosaminoglycan in each group. Increased deposition of collagen and glycosaminoglycan was observed in the stents created in vivo. Biomechanical testing demonstrated that the cartilaginous cylinders in each group were readily elastic and withstood high degrees of pressure.nnnCONCLUSIONSnThis study demonstrates the feasibility of creating cartilaginous stents in vitro and in vivo using chondrocyte seeded polymer matrices. This technology may be useful clinically for stricture disease in the genitourinary tract.

MP68-19 BILATERAL SINGLE SESSION PERCUTANEOUS NEPHROLITHOTOMY: IS IT WORTH THE RISK?

access the pelvicalyceal system is through the tip of the papilla. We describe the ‘split papilla’ which provides endoscopic evidence of a correct puncture. The objective was to study the hemoglobin fall and blood transfusion rate between split papilla group versus non split papilla group. METHODS: All punctures were done by using the triangulation technique using fluoroscopy. Tracts were dilated using a balloon dilator. Once the stone was cleared the Amplatz was withdrawn into the tract to visualize the split papilla. Which appeared as triangular flaps with straight lines converging towards the apex. We compared endoscopic time, drop in hemoglobin and transfusion rate in those patients in whom the split papilla(Group A) was demonstrable versus those in whom it was not(Group B). RESULTS: During the study period 123 patients underwent PCNL. 45 patients did not have split papilla, 78 patents had split papilla. All the parameters were matched in both groups. The average fall in hemoglobin in Group A was 1.4 (SD1.06) and in group B was 2.2( SD 0.9), p-value 0.001. None required blood transfusion in both the group. CONCLUSIONS: Blood loss was significantly lesser in patients where a split papilla could be demonstrated. A careful search for this finding can provide the surgeon with a quality control tool to assess the PCNL puncture.

MP75-10 TAILORING ANTIBIOTIC PROPHYLAXIS FOR URETEROSCOPIC PROCEDURES BASED ON LOCAL RESISTANCE PROFILES MAY LEAD TO REDUCED RATES OF INFECTIONS AND UROSEPSIS

INTRODUCTION AND OBJECTIVES: The insertion of double J ureteral catheters is a common practice in modern urology. Unfortunately, different symptoms may occur with indwelling stents, such as dysuria, hematuria, flank and suprapubic pain. The objective of the present study was to evaluate the safety and efficacy of levobupivacaine as an intravesical instillation in the control of pain and urinary symptoms generated by the ureteral stent. METHODS: 77 patients with double J catheter (Percuflex 26/6 TM, Boston Scientific) after endoscopic treatment of an ureteral stone were randomized into 2 groups. Both groups received standard therapy for catheter discomfort management (paracetamol, ketorolac and tamsulosine). At the end of the procedure group 1 received instillation of 30 cc of saline and group 2 received a dose of 150 mg (30 cc) of intravesical levobupivacaine. Surgeon and patient were blinded for type of instillation received. Symptomatology was evaluate at 4 and 24 hours after the procedure and at the moment of catheter removal. The USSQ survey, in its Spanish-validated version, was used for this purpose. Plasma levels of levobupivacaine were measured at 5, 10, 15 and 20 minutes after instillation in both groups. RESULTS: Both groups were comparable in terms of age, location and size of stone treated , duration of procedure, stone free rate and days of catheter permanence. Statistical analysis showed significant reduction in group 2 regarding the intensity of pain at 4 hours postoperatively (p 1⁄4 0.02). In addition, during the catheter carrying period, those patients in whom the levobupivacaine solution was applied had less alteration in work activities (p 1⁄4 0.03), and less discomfort in the sexual sphere (p 1⁄4 0.01) Plasma levels of levobupivacaine in the 40 patients exposed to the drug were undetectable (<0.1 mg / dL). There were no side effects attributable to intravesical levobupivacaine. CONCLUSIONS: To our knowledge this is the first clinical trial using levobupivacaine in bladder instillation, which demonstrate better pain control in the immediate postoperative period. There is a significant effect on daily life parameters that could allow better tolerance to the catheter during the time it should remain installed. Also, the use of this substance does not imply a higher cost and its safe, without side effects.