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.     

Endoscopic urethroplasty with unseeded small intestinal submucosa collagen matrix grafts: a pilot study

PURPOSE: We evaluated small intestinal submucosa (SIS) as a substitute for skin in endoscopic urethroplasty performed as treatment for inflammatory and iatrogenic strictures of the male bulbar urethra, and in the early treatment of bulbomembranous urethral injuries associated with recent pelvic fractures. Tissue integration and epithelialization of SIS in endoscopic urethroplasty were assessed, as was the long-term maintenance of urethral patency following this treatment. MATERIALS AND METHODS: Nine patients with bulbar urethral strictures defined by urethrography were enrolled in the study. Following optical urethrotomy the SIS grafts were tubularized over a purpose specific graft carrying balloon device and secured into the opened urethra as described for endoscopic urethroplasty. Patients were followed with urethroscopy and urethrography at regular intervals as per protocol or when symptoms arose. Failure was defined as the need for any further intervention. RESULTS: Two patients with short inflammatory strictures maintained urethral patency without any intervention at 1 and 2 years, respectively. Stricture recurrence developed in 6 patients within 3 months of surgery. Of these, 3 have undergone subsequent open urethroplasty, 2 are currently awaiting urethroplasty and 1 is maintaining urethral patency with regular self-dilatation. One patient was lost to followup. CONCLUSIONS: Endoscopic urethroplasty with unseeded SIS grafts was unsuccessful in this study.     

Multiple Oblique Illumination and High-Definition Microscopy for Breast Fine-Needle Aspirates

ABSTRACT We wished to determine whether small-intestinal submucosa (SIS) will epithelialize when used as a ureteral replacement material. An 11-mm segment of native ureter was excised from eight New Zealand White rabbits and replaced with an 11-mm porcine SIS graft, which was circumferentially wrapped around a ureteral stent. The SIS ureteral grafts were harvested at 11 days or 35 days postimplantation and examined grossly and by standard light microscopy techniques. Partial epithelialization with the ingrowth of urothelium, smooth muscle cells, and blood vessels was observed in the grafts harvested at 11 days postimplantation. The SIS ureteral grafts examined at 35 days postimplantation showed additional restructuring of the smooth muscle cell layer and more organized epithelialization in comparison to the SIS graft examined at 11 days. After 35 days of regenerative healing, elements of all three layers of the native ureter were observed within the collagen matrix of the SIS graft. No significant complications were observed, but all subjects (8/8) demonstrated mild intra-abdominal adhesions. Mild collecting system dilatations were observed in 4/4 (100%) of the animals harvested at 35 days and in 0/4 (0%) of the animals harvested at 11 days. We have this demonstrated in this preliminary study that SIS xenografts will epithelialize when used as a ureteral replacement material. The repair mechanism of these ureteral grafts occurred through a regenerative healing process rather than by scar formation. With further studies, this material may prove to be a useful treatment option in patients with ureteral injuries.     

尿道细胞外基质在兔尿道重建中的应用

目的 评价尿道细胞外基质作为一种生物材料重建尿道的效果. 方法 切取新西兰兔的尿道制备尿道细胞外基质.手术切除实验组1～1.5 cm的尿道片段后用细胞外基质修复缺损,采用ELISA法检测术前、术后12、24及48 h血清TNFα的水平,评估术后兔的免疫反应状态.术后10d和3、6、24周取修复段尿道,行组织学观察并做尿道造影、尿道镜及尿流动力学检查. 结果 术后实验组血清TNFα水平较对照组略有升高,但无统计学意义(P>0.05).术后10 d,上皮细胞开始从边缘向细胞外基质移行并出现新生小血管;3周上皮细胞覆盖细胞外基质的整个管腔;6周出现排列不规则的平滑肌纤维;24周平滑肌数量明显增多,成束状排列.尿道造影、尿道镜及尿流动力学检测检查显示,尿道基质管壁光滑,排尿通畅. 结论 尿道细胞外基质是一种安全有效的尿道重建材料.     

Temporal differentiation and maturation of regenerated rat urothelium

OBJECTIVE

To determine if porcine small intestinal submucosa (SIS)‐regenerated urothelium expresses markers of urothelial differentiation, uroplakin and zona occludens‐1 (ZO‐1), and whether their expression correlates with the histological appearance of the urothelium.

MATERIALS AND METHODS

In all, 15 rats underwent partial cystectomy and bladder replacement with SIS. Regenerated bladders were harvested at either 2, 7, 14, 28, or 56 days after SIS grafting. Histological examination with haematoxylin and eosin staining was conducted to assess tissue regeneration. Immunohistochemistry was performed with uroplakin and ZO‐1 antibodies.

RESULTS

By 14 days after SIS grafting, the urothelial layer was completely confluent over the SIS. Expression of uroplakin and ZO‐1, evident at 2 days after SIS grafting, progressed from a cytoplasmic pattern of expression to a mature pattern of cytoplasmic and membrane expression by 56 days after SIS grafting.

CONCLUSION

In vivo tissue regeneration produces histologically and phenotypically mature urothelium within 2 weeks of SIS implantation. Regeneration of functional urothelium is probably essential for the subsequent development of the remaining bladder.     

Urethral replacement using epidermal cell-seeded tubular acellular bladder collagen matrix

OBJECTIVES: To investigate the feasibility of replacing urinary epithelium cells with foreskin epidermal cells to reconstruct engineered anterior urethra with an acellular collagen matrix. MATERIALS AND METHODS: Acellular collagen matrices were generated from allogeneic rabbit bladder submucosa. In nine rabbits, autologous foreskin epidermal cells were isolated, expanded in vitro, and labelled with 5-bromo2'-deoxy-uridine (BrdU) before seeding onto a tubular acellular collagen matrix (1.5x1 cm). In male rabbits, a urethral mucosal defect was created, and urethroplasty performed with a tubular acellular collagen matrix seeded with epidermal cells (nine rabbits) or with a matrix with no cell seeding (nine rabbits; control group). Urethrography was done at 1, 2 and 6 months after grafting. The urethral grafts were harvested and analysed grossly and histologically. RESULTS: In the control group, gross views and urethrography revealed stricture of repaired defects at the different sample times. In the experimental group, a wide urethral calibre was maintained with no sign of strictures. Histology in the control group showed a single layer of epithelium cells with disorganized muscle fibre bundles in the submucosa layer at 1 month after grafting, and a transitional cell layer surrounded by disorganized muscle fibre bundles at 2 and at 6 months. Grafts seeded with epidermal cells formed a single-layer structure by 1 month, and at 2 and 6 months there were several layers of epidermal cells with abundant vessels in the submucosa. There was an evident margin between graft epidermal cells and host epithelium at 6 months. The implanted cells expressed keratin, shown by staining with anti-pancytokeratins. Immunofluorescence for BrdU confirmed the presence of implanted epidermal cells at 1 month after grafting; there were fewer positive cells at the implantation site at 2 months. At 6 months, there were several layers of epidermal cells with no signs of BrdU staining. CONCLUSIONS: Urethral reconstruction was better with an acellular collagen matrix seeded with epidermal cells than with the acellular collagen matrix alone. Foreskin epidermal cells seem adequate in replacing urethral epithelium cells for urethral reconstruction.     

小肠黏膜下脱细胞基质修复前尿道狭窄的疗效分析

目的 探讨小肠黏膜下脱细胞基质(small intestinal submucosa,SIS)修复前尿道狭窄的可行性和有效性.方法 2009年6月至2010年8月采用4层SIS补片修复治疗尿道狭窄患者18例.患者年龄20～69岁,平均38岁;尿道狭窄段3.5～7.0 cm,平均4.6 cm;术前最大尿流率1.5～5.5 ml/s,平均3.8 ml/s.术中按需将SIS(长4.0～7.5 cm,宽 2.0 cm)植入尿道背侧缺损处,5-0可吸收线将SIS间断固定在阴茎海绵体上,SIS两侧与已剪开的狭窄段尿道作连续缝合,两端分别与尿道断端作间断吻合.结果 手术过程顺利,术后恢复好.随访6～18个月,平均10个月,患者未发生感染、排斥反应等并发症.17例排尿通畅,最大尿流率14.0～44.0 ml/s,平均25.4 ml/s.尿道造影显示尿道通畅;术后4、6周尿道镜检查示SIS移植物与周围组织分界清楚;术后14周尿道镜检查SIS已降解,修复段尿道与周围组织间限消失,黏膜光洁完整,管腔无明显狭窄;植入SIS部位活检显示黏膜表层为上皮细胞.1例尿道下裂术后患者术后5个月出现轻度尿道狭窄症状,行尿道扩张治疗.结论 利用SIS修复尿道狭窄具有创伤小、抗感染力强的特点,可作为组织工程尿道修复重建材料修复部分尿道狭窄患者.

Abstract：

Objective To investigate the feasibility of using small intestinal submucosa (SIS) graft for the repair of anterior urethral strictures. Methods From June 2009 to August 2010, 18 men (mean age, 38 yrs) with anterior urethral strictures underwent urethroplasty using a four-layer SIS as an onlay patch graft. SIS was used to augment the urethral caliber at the stricture site. The mean stricture length was 4.6 cm (range 3.5 to 7 cm). The pre-operative mean maximal flow rate was 3.8 ml/s (range 1.5 to 5.5 ml/s). The required SIS grafts (4 to 7.5 cm long and 2 cm wide) were positioned into the urethrotomy defect and were spread-fixed to the corpora cavernosa using 5-0 polyglactin interrupted sutures. Two apices of the graft were sutured to the proximal and distal apices of the urethrotomy with 5-0 polyglactin interrupted stitches. The margins of the opened urethra were sutured to the SIS patch with 5-0 polyglactin running sutures. Results The mean follow-up period was 10 mon. (range 6-18 mon.). No postoperative complication, such as infection or rejection related to the use of heterologous graft material was observed. Seventeen patients voided well postoperatively with the mean peak urine flow of 25.4 ml/s (14-44 ml/s). Cystoscopy revealed that at four weeks and six weeks, the SIS graft was well distinguishable from the normal surrounding tissue; and at 16 weeks, the urothelium was regenerated and the biomaterial was not distinguishable from the normal surrounding tissue. The squamosal epithelium was seen in the histological examination of the grafts. The remaining one patient with failed hypospadias developed a slight urethral narrowing at five months post-operatively and needed sound dilatations. Conclusions SIS matrix appears to be a safe and effective reconstructive material in selected urethral reconstructions.     

Urethral replacement: a comparison between small intestinal submucosa grafts and spontaneous regeneration

OBJECTIVE: To evaluate the use of commercially available single-layer small intestinal submucosa (SIS) for urethral replacement, both as an onlay and as a tube, in a rabbit model. MATERIALS AND METHODS: Thirty-six male rabbits were assigned to four experimental groups. Group 1 had the ventral wall of the penile urethra excised for 15 mm; in group 2 this created defect was patched with a SIS onlay graft; group 3 had complete excision of a 15 mm segment of the penile urethra; and in group 4, this created defect was replaced with a SIS tube graft. In all rabbits the urethra was stented for 2 weeks. A retrograde urethrogram was taken in all rabbits before death at 3, 6 and 12 weeks after surgery. The urethra was then exposed, examined carefully and excised for histopathological examination. RESULTS: In groups 1 and 2 the retrograde urethrograms were normal in 13 rabbits and there was relative narrowing in two rabbits in group 1 and three in group 2. In groups 3 and 4 all rabbits developed urethral fistulae or strictures. Histological examination of the urethra showed epithelial regeneration supported by smooth muscle backing in all rabbits in group 1, while rabbits in group 2 showed no regeneration of smooth muscle. By contrast, rabbits in groups 3 and 4 showed incomplete regeneration and progressive fibrosis. CONCLUSIONS: Single-layer SIS is not a suitable urethral substitute in this animal model. When used as an onlay, healing is inferior to spontaneous urethral regeneration, as SIS impedes smooth muscle cell regeneration. When used as a tube, there is complete scarring and urethral luminal occlusion.     

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.     

Optimal use of negative pressure wound therapy for skin grafts

Skin grafting is a technique used for transplanting human skin (i.e. epidermal and some dermal layers) from a harvest site to a recipient site. However, advancements in bioengineered matrices have also introduced alternatives to skin grafts. The method used to secure the graft, whether skin or biomatrix, is critical in reducing graft failure. During the past several years, negative pressure wound therapy using reticulated open-cell foam (NPWT/ROCF; V.A.C.? Therapy, KCI USA, Inc., San Antonio, TX) has become a well-established method for bolstering grafts to recipient beds and is being used more frequently over biomatrices to help improve graft outcomes. This review will combine expert opinion with scientific evidence for the use of NPWT/ROCF over grafts.     

Small intestinal submucosa (SIS) graft urethroplasty: short-term results

OBJECTIVE: We evaluated the use of small intestinal submucosa (SIS) graft in penile and bulbar urethroplasties. METHODS: From 2003 to 2004, 20 men (mean age, 41 yr) with anterior urethral strictures underwent urethroplasty using SIS (COOK) as an inlay or onlay patch graft. Stricture location was penile in 1 patient, bulbar in 16, and penile-bulbar in 3. Average stricture and graft lengths were 3 and 5.7 cm, respectively. A dorsal inlay graft was performed in 14 cases, ventral onlay graft in 1, and dorsal inlay plus ventral onlay in 5. Clinical outcome was considered successful if no postoperative procedure was needed. RESULTS: Mean follow-up period was 21 mo (range: 13-35 mo). Seventeen cases (85%) were successful and 3 (15%) were failures. No postoperative complications were related to the use of heterologous graft material, such as infection or rejection. Sixteen successes (94%) were bulbar repairs and one a penile-bulbar repair, with stricture and graft average lengths 2.6 and 5.35 cm, respectively. Cystoscopy at 3 mo revealed adequate calibre lumens, but SIS grafted areas were not completely replaced by urothelium. The three failures were penile and penile-bulbar urethral repairs with stricture and graft average lengths of 5.7 and 7.7 cm, respectively. Recurrences showed fibrous tissue involving the grafted area with extension into the penile and bulbar urethra. CONCLUSIONS: In our short-term results, SIS seems to be a versatile material that may have a role in select urethral reconstructions. Longer follow-up and further investigations in select patients are needed before widespread use is advocated.     

生物可降解性尿道内支架修复战伤性尿道狭窄的研究

目的建立战伤性尿道狭窄动物模型,探讨生物可降解性尿道内支架对其进行重建修复的可行性。方法将新西兰雄兔28只分为两组,实验组(n=20):以定位爆炸法建立尿道狭窄模型。一月后行逆行尿道造影、尿道镜检查,并切除狭窄段尿道,行病理组织学观察证实。后置入人工合成生物可降解尿道内支架,置入术后2、4、8、12周分别行逆行尿道造影、尿道镜检查以及尿流动力学检测。并在以上各时间点处死5只动物,取狭窄处尿道组织,观察组织学修复重建情况。对照组(n=8):于实验组爆炸处理后4周和支架置入12周,分别取对照组4只动物与实验组对比观察。结果实验组所有动物爆炸后4周在尿道球部狭窄形成稳定狭窄模型(狭窄段长5～10 mm,尿道腔缩窄50%以上)。尿道内支架置入后2周,组织学观察见黏膜上皮新生迹象,并有炎性细胞浸润;4周时上皮新生明显,炎性细胞消失;8周时出现尿道平滑肌细胞再生,12周时见损伤后尿道组织结构完全修复,与正常尿道组织比较差异无统计学意义(P>0.05)。。同时间点尿道镜检查证实尿道腔隙、黏膜形态结构无异于正常对照组。尿流动力学检测显示两组间差异无统计学意义(P>0.05)。。结论应用成功建立的战伤性尿道狭窄动物模型,证实生物可降解性尿道内支架能作为修复战伤性尿道狭窄的理想材料,具有损伤小,易操作,功能恢复快的特点。     

Evaluation of stretched electrospun silk fibroin matrices seeded with urothelial cells for urethra reconstruction

Background

We investigated the feasibility of urethral reconstruction using stretched electrospun silk fibroin matrices.

Materials and methods

A novel electrospun silk fibroin matrix was prepared. The structure of the material was assessed by scanning electron microscopy and a porosity test. Canine urothelial cells were isolated, expanded, and seeded onto the material for 1 wk to obtain a tissue-engineered graft. The tissue-engineered graft was assessed using hematoxylin and eosin staining and scanning electron microscopy. A dorsal urethral mucosal defect was created in nine female beagle dogs. In the experimental group, tissue-engineered mucosa was used to repair urethra mucosa defects in six dogs. No substitute was used in the three dogs of the control group. Retrograde urethrography was performed at 1, 2, and 6 mo after grafting. The urethral grafts were analyzed grossly and histologically.

Results

Scanning electron microscope and a porosity test revealed that the material had a three-dimensional porous structure. Urothelial cells grew on the material and showed good biocompatibility with the stretched silk fibroin matrices. Canines implanted with tissue-engineered mucosa voided without difficulty. Retrograde urethrography revealed no signs of stricture. Histologic staining showed gradual epithelial cell development and stratified epithelial layers at 1, 2, and 6 mo. The canines in the control group showed difficulty in voiding. Retrograde urethrography showed urethra stricture. Histologic staining showed that no or only one layer of epithelial cells developed. A severe inflammatory reaction was also observed in the control group.

Conclusions

Stretched electrospun silk fibroin matrices have good biocompatibility with urothelial cells, which could prove to be a potential material for use in urethra reconstruction.     

Acellular muscle with Schwann-cell implantation: an alternative biologic nerve conduit

Denatured or acellular muscle grafts are known to support axonal regeneration. With increasing gap length, failure of regeneration is evident, due to the lack of viable Schwann cells in the graft. The authors created a biologic nerve conduit, in a rat sciatic nerve model, by implanting cultured Schwann cells into an acellular gracilis muscle. Autologous nerve grafts and acellular muscle grafts without Schwann cells served as controls. After 6 weeks, regeneration was assessed clinically, histologically, and morphometrically. Polymerase chain reaction (PCR) analysis showed that the implanted Schwann cells remained viable within the graft. Good regeneration was noted in the muscle-Schwann cell group, while regeneration in the muscle grafts without Schwann cells was significantly impaired. The muscle-Schwann cell graft demonstrated systematic and organized regeneration, including the proper orientation of regenerated fibers. The number of axons regenerating through the muscle-Schwann cell grafts was significantly increased, compared with the acellular muscle without Schwann cells. Implantation of Schwann cells into acellular muscle thus provided a biologic conduit with large basal lamina tubes, as a pathway for regenerating axons. The positive effects of Schwann cells, producing neurotrophic and neurotropic factors, supported axonal regeneration.     

Porcine small intestinal submucosa graft for repair of anterior urethral strictures

OBJECTIVES: We evaluated porcine small intestinal submucosa (SIS) used in the treatment of inflammatory, iatrogenic, posttraumatic, and idiopathic strictures of bulbar and penile urethra. Midterm maintenance of urethral patency was assessed. METHODS: Fifty patients aged 45-73 yr with anterior urethral stricture underwent urethroplasty using a porcine SIS collagen-based matrix for urethral reconstruction. Stricture was localized in the bulbar urethra in 10 patients, the bulbopenile area in 31 cases, and in the distal penile urethra in nine patients. All patients received a four-layered SIS patch graft in an onlay fashion. A voiding history, retrograde and antegrade urethrography, and cystoscopy were performed preoperatively and postoperatively. Failure was defined as stricture confirmed on urethrogram. RESULTS: After a mean follow-up of 31.2 mo (range: 24-36 mo), the clinical, radiological, and cosmetic findings were excellent in 40 (80%) patients. Restricture developed in one of 10 bulbar, five of 31 bulbopenile, and four of nine penile strictures. These all occurred in the first 6 mo postoperatively. All patients with recurrences needed further therapy, but there has been no additional recurrence observed to date. No complications such as fistula, wound infection, UTI, or rejection were observed. CONCLUSIONS: Use of inert porcine SIS matrix appears to be beneficial for patients with bulbar and bulbopenile strictures. Midterm results are comparable to skin flaps and mucosal grafts.     

Repair of different sized nerve defects using degenerated muscle grafts with vascular implantation: an experimental study in the rat.

In order to explore the repair of nerve defects of different sizes using degenerated muscle grafts with vascular implantation [DMG(+VI)], 10-, 15-, 20-, and 25-mm sciatic nerve defects in the rat were bridged. After eight months, the muscle grafts were reconstructed to the nerve-like tissues. There was better revascularization in the grafts because of vascular implantation. Regenerated axons could grow through 10-, 15-, 20-, and 25-mm muscle grafts to the distal nerve stump and ultimately to the target-organs. The regenerated axons were well myelinated and nerve conduction was recovered. However, as the graft length increased, the quantity of regenerated axons gradually decreased and the function of the regenerated axons was affected.     

Ureteral segment replacement using a circumferential small-intestinal submucosa xenogenic graft.

We wished to determine whether small-intestinal submucosa (SIS) will epithelialize when used as a ureteral replacement material. An 11-mm segment of native ureter was excised from eight New Zealand White rabbits and replaced with an 11-mm porcine SIS graft, which was circumferentially wrapped around a ureteral stent. The SIS ureteral grafts were harvested at 11 days or 35 days postimplantation and examined grossly and by standard light microscopy techniques. Partial epithelialization with the ingrowth of urothelium, smooth muscle cells, and blood vessels was observed in the grafts harvested at 11 days postimplantation. The SIS ureteral grafts examined at 35 days postimplantation showed additional restructuring of the smooth muscle cell layer and more organized epithelialization in comparison to the SIS graft examined at 11 days. After 35 days of regenerative healing, elements of all three layers of the native ureter were observed within the collagen matrix of the SIS graft. No significant complications were observed, but all subjects (8/8) demonstrated mild intra-abdominal adhesions. Mild collecting system dilatations were observed in 4/4 (100%) of the animals harvested at 35 days and in 0/4 (0%) of the animals harvested at 11 days. We have this demonstrated in this preliminary study that SIS xenografts will epithelialize when used as a ureteral replacement material. The repair mechanism of these ureteral grafts occurred through a regenerative healing process rather than by scar formation. With further studies, this material may prove to be a useful treatment option in patients with ureteral injuries.     

New Regenerative Vascular Grafts for Hemodialysis Access: Evaluation of a Preclinical Animal Model

The purpose of this study was to evaluate a suitable animal model for the in vivo evaluation of patency and vascular tissue regeneration in small intestinal submucosa (SIS) vascular grafts for hemodialysis access. First, a 4-mm U-shaped SIS vascular graft was implanted between the internal carotid artery (CA) and the external jugular vein (JV) in five sheep and six swine. The U-shape grafts remained functional for 53 ± 4 days in sheep and 32 ± 2 days in swine. The sheep model presented exaggerated inflammation, so the swine model was selected for the in vivo study. Based on these initial results, a 4-mm C-shape SIS vascular graft with SIS circumferential reinforcement was developed to mechanically improve the vascular graft and manage complications identified during surgery in both sheep and swine. The C-shape vascular graft was implanted in a swine model (n = 3) between the CA and JV. GORE-TEX® vascular grafts were used as controls in the contralateral side of the neck. C-shape grafts remained patent for 47 ± 4 days, whereas the GORE-TEX® grafts were patent for 30 ± 15 days. The C-shape vascular graft was easier to handle during surgery, and its circumferential reinforcement improved in vivo patency, avoiding kinks in the graft after implantation. Histological results showed neovascularization and some regeneration with the alignment of endothelial cells in the vascular wall of the grafts. The model developed may be helpful in other research involving in vivo studies of vascular grafts for hemodialysis access.     

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.     

Use of single layer small intestinal submucosa for long segment ureteral replacement: a pilot study

PURPOSE: Previous studies have demonstrated successful use of small intestinal submucosa (SIS) as a tube for replacing short segment (11 mm) proximal ureteral defects. However, such small segment ureteral defects could be managed by resection re-anastomosis. We evaluated the use of 1-layer SIS as a tube for the replacement of long segment ureteral defects. MATERIALS AND METHODS: The ureters of 5 female mongrel dogs were accessed through a median laparotomy incision. A 4 cm segment of mid ureter was resected on the right side. The right ureteral segments were replaced by tubularized SIS segments using 6-zero polydioxanone interrupted sutures. Internal pigtail stents were left for 6 weeks. All animals were sacrificed at 12 weeks. Ureteral patency was assessed by excretory urography and magnetic resonance urography 7 and 12 weeks after the initial procedures. Inflammation and regeneration were assessed histologically. RESULTS: At 12 weeks all ureters on the experimental side were completely occluded with significant hydroureteronephrosis and the subsequent deterioration of kidney function. At autopsy there was failure to calibrate any of the experimental ureters with a 3Fr catheter. Although histologically urothelium and muscular cells had proliferated over the graft, they were embedded in an intense fibrotic and inflammatory process. CONCLUSIONS: Technically 1-layer SIS was easily modeled, providing the conditions for watertight anastomosis. The regeneration of urothelium and muscle was induced and supported by the graft. However, functional replacement was not successful. One-layer SIS is not a suitable material for replacing long segment (4 cm) ureteral defects.