Laparoscopic replacement of urinary tract segments using biodegradable materials in a large-animal model.

OBJECTIVE: We elected to evaluate laparoscopic segmental bladder and ureteral replacement with free biodegradable graft materials in a large-animal model. MATERIALS AND METHODS: In 18 Yucatan minipigs, a 1.5- to 2.8-cm segment of the upper ureter was excised. In 15 study animals, the ureter was laparoscopically replaced: by a stinted (6F double-J stent) tube graft made of acellular matrix (AMX) prepared from minipig ureters (MUMX) in 6 animals, acellular matrix prepared from domestic pig ureters (DUMX) in 3, and small-intestinal submucosa (SIS) in 6. In 3 control animals, the ureteral gap was bridged only by an indwelling stent. The stent was removed at 6 weeks, and retrograde ureteropyelography was performed preoperatively and at 8 and 12 weeks postoperatively, when animals were sacrificed. In 18 Yucatan minipigs, 3 x 3-cm bladder dome segments were laparoscopically replaced: by acellular matrix prepared from minipig small bowel (MBMX) in 6 animals, and SIS in 6 animals. The bladder was closed primarily in 6 control animals. Bladder capacity was assessed preoperatively and at 6 and at 12 weeks, when the animals were sacrificed. RESULTS: The average operating time for ureteral replacement was 187 (range 105-360) minutes. At 12 weeks, all animals had complete obstruction at the level of the replacement, with fibrosis +/- bone formation at the level of the stricture. For the bladder replacement groups, the average operating time was 147 (range 85-200) minutes. At 12 weeks, the bladder capacity was 60% of the preoperative capacity in the control group, 118% in the MBMX group, and 142% in the SIS group. Histologic examination showed regeneration of urothelium and some muscle with both MBMX and SIS. CONCLUSIONS: We were able to develop a reliable laparoscopic technique for both segmental ureteral and partial bladder replacement in a porcine model. With AMX and SIS replacement, regeneration of urothelium occurred in both ureter and bladder. However, functional replacement was successful only in the bladder.     

Growth of bone marrow stromal cells on small intestinal submucosa: an alternative cell source for tissue engineered bladder

OBJECTIVE: To assess the potential use of bone marrow stromal cell (BMSC)-seeded biodegradable scaffold for bladder regeneration in a canine model, by characterizing BMSCs and comparing them to bladder smooth muscle cells (SMCs) by immunohistochemistry, growth capability, and contractility. MATERIALS AND METHODS: Bone marrow was taken by direct needle aspiration from the femurs of five beagle dogs for the in vitro study. Mononuclear cells were isolated by Ficoll-Paque density gradient centrifugation and cultivated in medium 199 with 10% fetal bovine serum. BMSCs were characterized by cell proliferation, in vitro contractility, immunohistochemical analysis, and the growth pattern on small intestinal submucosa (SIS) scaffolds compared to bladder SMC cultures from the same dogs. Another six dogs had a hemicystectomy and bladder augmentation with BMSC-seeded (two), bladder cells including urothelial cells plus SMC-seeded SIS (two) and unseeded SIS scaffolds (two). The six dogs were followed for 10 weeks after augmentation. RESULTS: In vitro BMSCs had a significant contractile response to calcium-ionophore, with a mean (sem) 36 (2)%, relative contraction (P < 0.01), which was similar to bladder SMCs but markedly different from fibroblasts. BMSCs also expressed alpha-smooth muscle actin by immunohistochemical staining and Western blotting, but did not express desmin or myosin. In vivo, both BMSC-seeded and bladder cell-seeded SIS grafts had solid smooth-muscle bundle formation throughout the graft. CONCLUSIONS: BMSCs had a similar cell proliferation, histological appearance and contractile phenotype as primary cultured bladder SMCs. SIS supported three-dimensional growth of BMSCs in vitro, and BMSC-seeded SIS scaffold promoted bladder regeneration in a canine model. BMSCs may serve as an alternative cell source in urological tissue engineering.     

Laparoscopic augmentation cystoplasty: a comparison between native ileum and small intestinal submucosa in the porcine model

OBJECTIVES: To determine the feasibility of laparoscopic augmentation cystoplasty (LAC) in the porcine model and to compare LAC using standard bowel vs a small intestinal submucosa (SIS) allograft. MATERIALS AND METHODS: Fourteen female pigs underwent LAC; six had standard ileal AC and eight AC with SIS. All the pigs had limited cystometrogram studies before surgery to determine bladder capacity. At 6 weeks after surgery the pigs were anaesthetized, the bladder capacities were re-assessed and then the pigs were killed; the bladders were harvested and examined histologically. RESULTS: In all, 12 of 14 pigs completed the 6-week survival period; two pigs from the SIS group died from urinary ascites secondary to anastomotic leaks at the cystoplasty site. There were no complications in the ileal augmentation group. The operative duration was similar in both groups. The bladder capacities increased significantly in both groups, although more reliably in the native ileum group. In two pigs in the SIS group there was no increase in bladder capacity. CONCLUSIONS: LAC is feasible in the porcine model and results in a significant increase in bladder capacity. AC using SIS does not appear to increase bladder capacity as reliably as native ileum, and has a higher complication rate.     

小肠黏膜下层修复尿道的实验研究

目的探讨小肠黏膜下层(small intestinal submucosa,SIS)在尿道修复重建中的应用价值.方法 24只日本雄性大耳白兔,随机分为A、B、C及D组(n=6).A、B组切除前尿道2.0 cm,A组,用管状SIS修复尿道缺损;B组将其断端与周围组织直接缝合作为对照.C、D组仅切除2.0 cm尿道前壁,保留一半尿道壁为底板,C组用片状SIS修复尿道缺损;D组将其残端与周围组织直接缝合作为对照.均于修复后6、12周行组织学观察;12周行尿道膀胱造影及尿动力学检查.结果术后6周,A、C组修复的尿道有单层上皮细胞覆盖,基层组织中可见SIS的微小碎片包裹,出现不规则紊乱的平滑肌细胞生长,A组较C组的炎性反应重,有白细胞及淋巴细胞浸润,C组出现新生血管.术后12周,C组的上皮组织及基层下组织与D组无明显差别,平滑肌排列规则,血管数目进一步增多,炎性反应消失,未见SIS组织;A组中仍可见少数SIS的微小碎片;B组1只、D组2只尿道自行修复,余可见尿道闭塞,大量结缔组织生长,炎性细胞浸润,无正常上皮结构.术后12周尿道膀胱造影,A、C组可见尿道完整、光滑,无尿液外渗、尿道憩室等形成;尿动力学检查示A、C组的膀胱容量、最大尿道压分别与术前比较,差异无统计学意义(P＞0.05),而B、D组不能置入测压管检测.结论 SIS可作为兔尿道修复重建的良好支架材料,片状SIS修复优于管状SIS修复.     

Small intestinal submucosa as a small-caliber venous graft: a novel model for hepatocyte transplantation on synthetic biodegradable polymer scaffolds with direct access to the portal venous system

BACKGROUND/PURPOSE: Hepatotrophic factors in the portal blood are critically important for the survival of heterotopically transplanted hepatocytes. Currently, no model exists for the implantation of hepatocytes on biodegradable polymer scaffolds with direct access to the portal blood. This study investigates the use of small intestinal submucosa (SIS) as a small-caliber venous conduit that may be used for the implantation of tissue-engineered liver. METHODS: SIS was prepared from segments of rat jejunum and implanted as a venous conduit between the portal vein and inferior vena cava in 26 heparinized Lewis rats. Venograms were performed periodically, and the grafts were harvested at various time-points and examined by scanning electron microscopy (SEM) and histology. Von Willebrand Factor (vWF) staining was performed to assess endothelialization. RESULTS: Five rats died of technical complications. Seventeen of 21 rats (81%) maintained patent grafts at the time of death up to 8 weeks. Venograms demonstrated patent grafts at 3 and 8 weeks. SEM results showed a smooth luminal surface with endothelial-like cells by 3 weeks. Histology demonstrated a confluent luminal endothelial monolayer, absence of thrombus, and neovascularization in the SIS graft. VWF staining results were positive, confirming the growth of endothelial cells on the luminal surface. In preliminary studies, implantation of hepatocytes seeded on biodegradable polymer tubes into the SIS graft demonstrated clusters of viable cells after 2 days. CONCLUSIONS: Rat SIS can be prepared readily, maintains high patency as a small-caliber venous graft, and may be a useful model for the transplantation of tissue-engineered liver with access to the portal circulation.     

Challenges in a larger bladder replacement with cell-seeded and unseeded small intestinal submucosa grafts in a subtotal cystectomy model

OBJECTIVE: To evaluate small intestinal submucosa (SIS), unseeded or seeded, as a possible augmentation material in a canine model of subtotal cystectomy. MATERIALS AND METHODS: In all, 22 male dogs had a 90% partial cystectomy and were then divided into three groups. At 1 month after the initial cystectomy, dogs in group 1 (unseeded, six) and group 2 (seeded, six) received a bladder augmentation with a corresponding SIS graft. The dogs in group 3 (ten) received no further surgery and were considered the surgical control group. All dogs were evaluated before and after surgery with blood chemistry, urine culture, intravenous urography, cystograms and cystometrograms. After surgery (at 1, 5 and 9 months), the bladders were examined using routine histology and immunohistochemistry. RESULTS: All 22 dogs survived the subtotal cystectomy, and 18 survived their intended survival period. One dog, in group 2 (seeded), was killed at 1 month after augmentation due to bladder perforation caused by a large piece of incompletely absorbed SIS. Three other dogs (group 1, two; and group 2, one) were killed within 2 months after augmentation due to bladder obstruction by stones. Group 1 and group 2 SIS grafts had moderate to heavy adhesion, graft shrinkage, and some had bone and calcification at the graft site. Histologically, there was limited bladder regeneration in both groups. Interestingly, dogs in group 3 at 1 month after cystectomy (when group 1 and 2 received their augmentations) had severely shrunken bladders and histologically had severe inflammation, fibroblast infiltration and muscle hypertrophy. These results verify the subtotal cystectomy model. CONCLUSIONS: The use of seeded or unseeded SIS in a subtotal cystectomy model does not induce the same quality and quantity of bladder regeneration that is seen in the 40% non-inflammatory cystectomy model. This study provides important insights into the process of regeneration in a severely damaged bladder. The results led us to re-evaluate the critical elements required for a complete bladder replacement using tissue-engineering techniques.     

Scaffold seeded with cells is essential in urothelium regeneration and tissue remodeling in vivo after bladder augmentation using in vitro engineered graft

OBJECTIVE: Tissue-engineering methods using synthetic biodegradable scaffolds seeded with cells have potential to induce regeneration to a functional bladder wall. The aim of the study was to induce in vivo urothelial growth on implanted scaffolds previously seeded with stromal cells as compared with matrices implanted without cells for rat cystoplasty augmentation. MATERIALS AND METHODS: 3T3 mouse fibroblasts were multiplied up to total of 10(8) cells. Cells were grown on Dulbecco's modified essential medium supplemented with 10% of fetal bovine serum and antibiotics in CO(2) chambers. Cells were seeded on biodegradable polyglycolic acid (PGA) scaffolds in eight rats: four bladders were augmented with cell-seeded grafts and the other four with acellular scaffolds. Rats were sacrificed after 4 months in preparation for hematoxylin and eosin staining. RESULTS: One death in the acellular cystoplasty group was observed after 3 weeks. No epithelial layer was observed in the central part of the acellular graft. The cell-seeded grafts showed good visible multilayered epithelium with at least five layers of epithelial cells in the central part. The epithelium resembled rat native urothelium. The cell-seeded grafts showed a high degree of implanted 3T3 cells infiltration with good degradation of PGA fibers. CONCLUSIONS: Our data indicated that urothelial proliferation on PGA grafts was intensified using a "feeder layer" of fibroblasts.     

Small-intestinal submucosa for bladder augmentation: a review of preclinical studies

The need to find an alternative to the use of bowel for urinary reconstruction has renewed research interests involving bladder regeneration. Historically, alloplastic and biodegradable materials have demonstrated bladder regeneration; however, high complication rates and unreliable regenerative results have prevented any of these materials from being used clinically. Small-intestinal submucosa (SIS) is an acellular, nonimmunogenic, biodegradable, xenogeneic, collagen-based material that is derived from the submucosa layer of porcine small intestine. SIS has demonstrated regenerative capacities in multiple organ systems, including the aorta, vena cava, ligaments, tendons, abdominal wall, and skin. SIS has also demonstrated long-term reliable regenerative results in the rat and canine bladder-augmentation models. This article reviews the preclinical studies involving the use of SIS for bladder augmentation.     

Novel synthetic selectively degradable vascular prostheses: a preliminary implantation study

BACKGROUND: Vascular grafts perform less well than autologous arterial or vein grafts. The purpose of this study was to evaluate the short-term performance of selectively biodegradable filament-wound vascular prostheses, comprising elastomeric poly(ether urethane) (Lycra) scaffolds and flexible, hydrophilic biodegradable coatings. MATERIALS AND METHODS: Two types of selectively biodegradable vascular grafts were manufactured, comprising a filament-wound Lycra scaffold, subsequently coated with a biodegradable poly(ethylene glycol)/poly(lactic acid) (PELA) block copolymer. The two types of grafts differed in both the overall porosity of the scaffold and the hydrophilicity of the biodegradable constituent. A 60-mm-long and 6-mm-diameter filament-wound and polytetrafluoroethylene (ePTFE) grafts were implanted as interposition prostheses, randomly, at the right- and left-side carotid arteries. RESULTS: Implantation studies proved the grafts to be patent and pulsatile for periods of up to 3 months. Increasing the scaffold porosity and enhancing the hydrophilicity of the biodegradable component improved both the transmural tissue ingrowth process and the vascularization of the prosthesis wall. Also, a well-adhered peripheral tissue and a thin, uniform intima and endothelial lining were obtained. All ePTFE graft controls, although patent, were rather stiff and nonpulsatile. A thick pseudointima, poorly attached to the prosthesis inner surface, was observed. The compliance of the wet grafts was significantly higher than in the dry state, stemming mainly from the water-plasticizing effect on the biodegradable component. The grafts explanted after a period of 6 weeks exhibited compliance only slightly lower than that of the wet grafts. After 12 weeks, however, the hoop compliance was 20% lower than that prior to implantation. At 100 mm Hg, for example, the original compliance of the wet graft was 2.5%/100 mm Hg decreasing to 2.0%/100 mm Hg after a 3-month implantation. The compliance reduction with implantation is attributed to the ingrowth of the perigraft tissue as revealed by the histological study. A compliance of 2.0%/100 mm Hg is slightly better than that of a standard PTFE graft with an original compliance of 1.6%/100 mm Hg. Yet it is still an order of magnitude smaller than that of a canine carotid artery. CONCLUSIONS: The improved mechanical properties and enhanced healing of the highly porous filament-wound Lycra scaffold graft coated with hydrophilic biodegradable PELA has the potential of being a highly effective small caliber prosthetic graft.     

Morphologic evaluation of regenerated small bowel by small intestinal submucosa

Background/Purpose

Previous studies have shown small intestinal submucosa (SIS) can be used as biodegradable scaffolds in tissue engineering small intestine. The purpose of this study is to evaluate the regeneration of neointestine and its morphology using SIS.

Methods

A 2-cm tubular SIS graft from Sprague Dawley rat donors was interposed in the middle of a 6-cm ileal Thiry-Vella loop of Lewis rats, which was used to construct an ileostomy. The grafts were harvested at each of the time points ranging from 2 weeks to half a year after implantation, and native small intestine and grafts were investigated for morphology using histology and immunohistochemistry.

Results

At the early postoperative period, SIS grafts were colonized by numerous inflammatory cells. A mucosal epithelial layer began to line the luminal surface of the graft by 4 weeks, and by 12 weeks, the luminal surface was covered completely by a layer of neomucosa. Neomucosa with typical small bowel morphology was characterized by a columnar epithelial cell layer with goblet cells, Paneth cells, absorptive enterocytes, and enteroendocrine cells. Significant differences between neomucosa by 12 weeks and 24 weeks in the measurements of mucosal thickness, villus height, and crypt depth were found. The outer walls of SIS grafts were composed of distinct bundles of well-formed smooth muscle-like cells with some fibrovascular tissue.

Conclusions

This initial study suggests that tissue engineering neointestine using SIS can develop structural features of the normal intestine. Small intestinal submucosa might be a viable material in the creation of neointestine for patients suffering short bowel syndrome.     

Bladder regeneration in a canine model using hyaluronic acid-poly(lactic-co-glycolic-acid) nanoparticle modified porcine small intestinal submucosa

What's known on the subject? and What does the study add? Urinary bladder tissue can be produced by several regenerative techniques although consistent regeneration remains elusive and no single protocol is superior to the others. Small intestinal submucosa has been used as substrate for regeneration in several models and allows for full‐thickness bladder regeneration. Nanotechnology has been applied to impart specific physical and biological properties onto biological substrates. Nanoparticles composed of PLGA can be modified by the addition of hyaluronic acid and can be added to SIS. This modified SIS demonstrates a potential improvement in biological activity as suggested by more consistent smooth muscle regeneration in a canine model of bladder regeneration. This study demonstrates both the feasibilty and potential of synthetically‐modified natural biomaterials.

OBJECTIVE

? To determine if hyaluronic acid (HA) can be incorporated into porcine small intestinal submucosa (SIS) through poly (lactide‐co‐glycolide‐acid) (PLGA) nanoparticles to improve the consistency of the naturally derived biomaterial and promote bladder tissue regeneration.

METHODS

? Beagle dogs were subjected to 40% partial cystectomy followed by bladder augmentation with commercial SIS or HA‐PLGA‐modified SIS. ? Urodynamic testing was performed before and after augmentation to assess bladder volume. ? A scoring system was created to evaluate gross and histological presentations of regenerative bladders.

RESULTS

? All dogs showed full‐thickness bladder regeneration. ? Histological assessment showed improved smooth muscle regeneration in the HA‐PLGA‐modified SIS group. ? For both groups of dogs, urodynamics and graft measurements showed an approximate 40% reduction in bladder capacity and graft size from pre‐augmentation to post‐regeneration measurements. ? Application of the scoring system and statistical analysis failed to show a significant difference between the groups.

CONCLUSIONS

? SIS can be modified through the addition of HA‐PLGA nanoparticles. The modified grafts showed evidence of improved smooth muscle regeneration on histological assessment, although this difference was not evident on a novel grading scale. ? The volume loss and graft shrinkage experienced are consistent with previous models of SIS bladder regeneration at the 10‐week time point. ? Additional research into the delivery of HA and the long‐term benefits of HA on bladder regeneration is needed to determine the full benefit of HA‐PLGA‐modified SIS. In addition, a more objective biochemical characterization will be needed to evaluate the quality of regeneration.     

Bladder wall replacement by tissue engineering and autologous keratinocytes in minipigs

OBJECTIVE: To develop a tissue-engineered bladder wall replacement with autologous cells and a biodegradable scaffold, as whenever there is a lack of native urological tissue the bladder is reconstructed with different bowel segments, which has inevitable complications. MATERIAL AND METHODS: Skin biopsies were taken from six minipigs, and primary fibroblast and keratinocyte cell cultures established. A partial resection of the urinary bladder was reconstructed by a cell-seeded scaffold covered with completely differentiated epithelium and supported by a mucosa-free pedicled ileum graft. Each pig was assessed urodynamically and by cystography before operation and every month until explantation; the pigs were killed at 1, 2 and 3 months after augmentation. Control groups (of six pigs each) with bladder augmentation with complete or denuded ileum were used. The bladders were assessed histologically and by distensibility measurements RESULTS: The differentiated keratinocyte epithelium was still present on the reconstructed bladder wall after 3 months. The overall shrinkage rate was 6.5%. The engineered bladder wall had lower distensibility than the native one. The inflammatory reaction present initially had disappeared after 3 months. CONCLUSIONS: The implanted, tissue-engineered substitution of the bladder wall is not only a bridging graft, but also a complete reconstruction. With this model, extended bladder wall substitution seems feasible and should be investigated in further studies.     

不同组织来源的生物补片修补腹壁肌部分层次缺损的研究

目的探讨不同组织来源的生物补片体内组织重塑的差异,并提供信息供临床选择生物补片时参考。 方法选取健康SD大鼠,随机分组,每组10处缺损,建腹壁肌部分层次缺损模型并以基底膜（basement membrane,BM）/小肠黏膜下层（small intestine submucosa,SIS）复合细胞外基质补片、SIS补片、真皮补片和心包补片修补,设立未修补组为空白对照。术后2、4、8、16周评价修复区血清肿发生、皱缩率、植入降解比例,取修复区组织做组织学切片分析补片内组织长入、新生血管化、周围组织包裹情况。 结果实验期内,BM/SIS复合细胞外基质补片未发生血清肿,基本维持植入面积,术后4周再生高度有序的新生胶原替代缺损区域,术后8周补片降解。术后2周,SIS补片的血清肿发生率为65%,修复区早期大量炎性细胞浸润,再生胶原组织有序性较差,术后8周补片降解,术后16周皱缩率为－52.0%±9.8%。50%的真皮补片细胞浸润补片中央,完全降解。其余真皮补片出现纤维囊包裹,细胞仅浸润交界区,修复区显著扩张,实验期内无降解。心包补片仅少量细胞浸润交界区,无组织长入,术后16周皱缩率为－29.5%±14.0%,出现致密纤维囊包裹,实验期内无降解。 结论与SIS补片、心包补片和真皮补片相比,BM/SIS复合细胞外基质补片具备优异的组织修补和再生疗效。     

Experimental assessment of small intestinal submucosa as a small bowel graft in a rat model

Background/Purpose:

Small intestinal submucosa (SIS) is an extracellular matrix used in tissue engineering. The purpose of this study is to evaluate the feasibility of using SIS as a scafford for small bowel regeneration in a rat model.

Methods:

A 2-cm length tubular SIS graft from donor Sprague Dawley rats was interposed with bilateral anastomosis in the median tract of an isolated ileal loop of Lewis rats used to construct an ileostomy. The grafts were harvested and analyzed at each of the time-points ranging from 2 weeks to 24 weeks after operation using histology and immunohistochemistry.

Results:

Macroscopic examination found no adhesion in the surrounding area of neointestine by 24 weeks, and no stenosis was visible. The shrinkage of neointestine was indicated from 20% to 40%. Histologic and immunohistochemical evaluation showed that SIS grafts were colonized by numerous inflammation cells by 2 weeks. Neovascularization was evident, but the luminal surface was not epithelized. By 4 weeks, transitional mucosal epithelial layer began to line the luminal surface of the graft, and nearly 70% luminal surface of the graft had been covered by mucosal epithelium at 8 weeks. By 12 weeks, the luminal surface was covered completely by a mucosal layer with distinct bundles of smooth muscle cells in the neointestine. At 24 weeks, the neointestine wall showed 3 layers of mucosa, smooth muscle, and serosa.

Conclusions:

The preliminary study suggested that SIS allow rapid regeneration of mucosa and smooth muscle and might be a viable material for the creation of neointestine.     

Arterial wall regeneration in small-caliber vascular grafts in rats. Neoendothelial healing and prostacyclin production

Clinically available synthetic graft materials frequently fail when used as a small-caliber arterial substitute. Therefore, we developed a new type of graft material, prepared from a mixture of polyurethane and poly-L-lactic acid, to be used as a scaffold for the regeneration of the arterial wall. In this study microporous, compliant, biodegradable polyurethane/poly-L-lactic acid grafts (n = 16) and polytetrafluoroethylene grafts (n = 16) were implanted in the rat abdominal aorta and evaluated 3, 6, and 12 weeks after implantation. First, we evaluated the extent of neoendothelial healing (n = 8) by means of light microscopy and scanning electron microscopy. Next, we studied the ability of the neoendothelial cells to produce prostacyclin (n = 8) by means of bioassay for prostacyclin and radioimmunoassay for its stable hydrolysis product, 6-oxo-prostaglandin F1 alpha. There were no significant differences between the two graft types in the amount of prostacyclin production per unit graft area covered with neoendothelium, and this amount was the same as for normal endothelium. However, the polytetrafluoroethylene grafts showed incomplete neoendothelial healing, even after 12 weeks of implantation, in contrast to the polyurethane/poly-L-lactic acid grafts. The better healing characteristics of the polyurethane/poly-L-lactic acid grafts ensured the fast development of a complete neoarterial wall, possessing strength, compliance, and thromboresistance equivalent to normal arterial wall tissue. These results demonstrate that arterial wall tissue regeneration in polyurethane/poly-L-lactic acid grafts may open new perspectives in the field of arterial reconstructive surgery.     

Single-layer small intestinal submucosa or tunica vaginalis flap for correcting penile chordee

OBJECTIVE: To evaluate the use of single-layer small intestinal submucosa (SIS) and tunica vaginalis flap (TVF) for covering defects in the ventral surface of the tunica albuginea to correct severe penile chordee. MATERIALS AND METHODS: In all, 24 New Zealand white rabbits had a rectangular area excised from the ventral surface of tunica albuginea. In 12 rabbits TVF was used to cover the defect and in the remaining animals single-layer SIS was used. Animals were killed in groups of four at 2-, 6- and 12-week intervals after surgery. Before death in the 12-week group, an artificial erection was induced and cavernosography performed. Transverse sections of the penis at the graft site were stained with haematoxylin and eosin and Masson's trichrome, and examined microscopically. RESULTS: None of the animals developed haematoma or bleeding. The mean operative duration for TVF and SIS grafts were 56 and 29 min, respectively (P < 0.001). At the time of autopsy, there was no contracture in any of the rabbits. Of the 8 rabbits assessed, all had a straight rigid erection and cavernosography showed evidence of an intact corporal veno-occlusive mechanism. Histologically at 6 and 12 weeks, the mesothelial layers of the TVF and the SIS graft were completely replaced by well-collagenized tissue similar to that of normal tunica albuginea, with no inflammatory infiltrate. CONCLUSIONS: Both the TVF and single-layer SIS graft are viable comparable options for corporal body grafting. The 'off-the-shelf' availability, significantly quicker operation and absence of donor site morbidity make single-layer SIS better than TVF for correcting chordee.     

The artificial conduit for urinary diversion in rats: a preliminary study

OBJECTIVES: Small intestinal submucosa forms a scaffold for tubular construction. The aim of this study was to build the artificial conduit using small intestinal submucosa (SIS) and 3T3 fibroblasts for urinary diversion in rats. MATERIALS AND METHODS: 3T3 fibroblasts were multiplied to a total of 10(9). Two groups consisted of three Wistar rats each. The left ureters were separated from the bladder and anastomosed to the proximal end of the tubular scaffold. No splitting of the ureteral junction or drainage was done. The distal end of the scaffold was implanted into a previously performed channel in the abdominal wall. Cell-seeded grafts were used in the first group and acellular SIS scaffolds in the second group. Rats were sacrificed after 2 and 4 weeks. X-ray pyelography was performed. Hematoxylin and eosin staining was prepared from conduit cross sections. RESULTS: All animals survived the observation. An inflammatory reaction was observed within the peritoneal cavity in both groups. It was difficult to dissect the adhesions in the cell-seeded group. The ureteral-conduit anastomoses were tight in five cases, except there was leakage and pseudocyst formation after 14 days in one cell-seeded graft. No ureterohydronephrosis was observed in two acellular conduits after 14 or 30 days, and in one case of a cell-seeded graft. A neovascularisation process was observed in the acellular conduit after a month. Multilayered epithelium covered the conduit lumen near the anastomosis at the distal end of acellular conduit, a small islet-forming epithelial layer was observed after a month. CONCLUSIONS: 3T3 fibroblasts cannot serve as a "feeder layer" for ureteral augmentation. It seems that there is no need to split the ureteral-conduit junction. An SIS scaffold was used for tubular construction for urinary diversion in an animal model.     

Strength of Tissue Attachment to Composite and ePTFE Grafts After Ventral Hernia Repair

Objectives:

We sought to measure the strength of tissue attachment to mesh after laparoscopic ventral hernia repair in a porcine model.

Methods:

Twelve swine had two 10-cm × 16-cm sheets of ePTFE and polypropylene/ePTFE composite mesh fixated to the abdominal wall laparoscopically. Animals were euthanized at 2, 4, 6, and 12 weeks. The strength of tissue ingrowth was measured using a lap-shear method. Data are reported as mean force in pounds.

Results:

Average surface area of adhesions to percentage of surface area was not statistically significant between the composite and ePTFE materials. For the composite material, there was a 98.7% posterior probability that the force required at 2 weeks was less than that required at 12 weeks. There was no difference in graft-abdominal wall interface strength between week 2 and week 12 for ePTFE material. Both prosthetics achieved the majority of their strength from tissue ingrowth by 2 weeks, but the composite prosthesis continued to gain strength while the strength of the ePTFE plateaued. Composite mesh demonstrated a statistically significant increase in strength between the lap-shear force, whereas no statistically significant difference occurred in the ePTFE graft. For the composite material, there was complete cellular infiltration through the entire thickness of polypropylene (approximately 500 μm) to the ePTFE layer at 2 weeks. At 2 weeks for ePTFE, the cells did not penetrate into the graft on the visceral side. On the abdominal wall side, the grooves filled with tissue, but no cellular penetration into the ePTFE occurred. No histological difference existed in cellularity.

Conclusion:

This study demonstrates that the strength of tissue ingrowth is significantly higher (P<0.05) for the composite grafts relative to the ePTFE grafts at each time point. Approximately 74% of tissue ingrowth and strength occurs by 2 weeks postoperatively for the composite pros-thesis. The ePTFE graft tissue strength peaked and plateaued by 2 weeks. This may have clinical implications for human ventral hernia repair by partly addressing the issue of graft fixation to the abdominal wall during laparoscopic ventral hernia repair.     

Comparison of small-intestinal submucosa and expanded polytetrafluoroethylene as a vascular conduit in the presence of gram-positive contamination

OBJECTIVE: As a vascular conduit, expanded polytetrafluoroethylene (ePTFE) is susceptible to graft infection with Gram-positive organisms. Biomaterials, such as porcine small-intestinal submucosa (SIS), have been successfully used clinically as tissue substitutes outside the vascular arena. SUMMARY BACKGROUND DATA: In the present study, we compared a small-diameter conduit of SIS to ePTFE in the presence of Gram-positive contamination to evaluate infection resistance, incorporation and remodeling, morphometry, graft patency, and neointimal hyperplasia (NH) development. METHODS: Adult male mongrel pigs were randomized to receive either SIS or ePTFE (3-cm length, 6-mm diameter) and further randomized to 1 of 3 groups: Control (no graft inoculation), Staphylococcus aureus, or mucin-producing S epidermidis (each graft inoculation with 10 colonies/mL). Pressure measurements were obtained proximal and distal to the graft to create the iliac/aorta pressure ratio. Morphometric analysis of the neointima and histopathologic examinations was performed. Other outcomes included weekly WBC counts, graft incorporation, and quantitative culture of explanted grafts. RESULTS: Eighteen animals were randomized. All grafts were patent throughout the 6-week study period. Infected SIS grafts had less NH and little change in their iliac/aorta indices compared with infected ePTFE grafts. Quantitative cultures at euthanasia demonstrated no growth in either SIS group compared with 1.7 x 10(4) colonies for ePTFE S aureus and 6 x 10(2) for ePTFE S epi (each P < 0.001). All SIS grafts were incorporated. Histology demonstrated remodeling into host artery with smooth muscle and capillary ingrowth in all SIS groups. Scanning electron micrography illustrated smooth and complete endothelialization of all SIS grafts. CONCLUSIONS: Compared with ePTFE, SIS induces host tissue remodeling, exhibits a decreased neointimal response to infection, and is resistant to bacterial colonization. SIS may provide a superior alternative to ePTFE as a vascular conduit for peripheral vascular surgery.