Evaluation of small intestine submucosa and acellular dermis as diaphragmatic prostheses

Diaphragmatic reconstruction with autologous tendon engineered from mesenchymal amniocytes

PURPOSE

This study examined the effects of amniocyte-based engineered tendons on partial diaphragmatic replacement.

METHODS

Ovine mesenchymal amniocytes were labeled with green fluorescent protein (GFP), expanded, and seeded into a collagen hydrogel. Composite grafts (20 to 25 cm2) based on acellular dermis (group I), or acellular small intestinal submucosa (group II) received either a cell-seeded or an acellular hydrogel within their layers. Newborn lambs (n = 20) underwent partial diaphragmatic replacement with either an acellular or a cellular autologous construct from either group. At 3 to 12 months' postoperatively, implants were subjected to multiple analyses.

RESULTS

Diaphragmatic hernia recurrence was significantly higher in animals with acellular grafts (5 of 5) then in animals with cellular ones (1 of 4) in group I (P <.05) but not in group II (3 of 6 and 4 of 5, respectively). Cellular grafts had higher modular (5.27 +/- 1.98 v. 1.27 +/- 0.38 MPa) and ultimate (1.94 +/- 0.70 v. 0.29 +/- 0.05 MPa) tensile strength than acellular implants in group I (P <.05), but not in group II. Quantitative analyses showed no differences in extracellular matrix components between cellular and acellular implants in either group. All cellular implants showed GFP-positive cells.

CONCLUSIONS

Diaphragmatic repair with an autologous tendon engineered from mesenchymal amniocytes leads to improved mechanical and functional outcomes when compared with an equivalent acellular bioprosthetic repair, depending on scaffold composition. The amniotic fluid may be a preferred cell source for engineered diaphragmatic reconstruction.

Fallopian Tube Occlusion with Use of a Small Intestine Submucosa Device: Evaluation in a Rabbit Model

PURPOSE

The present study evaluates the short- and midterm efficacy of a small intestinal submucosa (SIS) device for fallopian tube occlusion in rabbits.

MATERIALS AND METHODS

In a pilot study, several SIS device designs were tested for positional stability (absence of migration). The design selected for further testing consisted of a center of spongy SIS surrounded by an SIS sheet and held together by a 0.006-inch wire helix with two barbs. It was delivered on the tip of a short coaxial 3-F/5-F catheter set. Using this design, bilateral transuterine fallopian tube occlusion was performed in eight New Zealand White rabbits. Follow-up consisted of plain radiography at 2 weeks and hysterosalpingography at 6 weeks (n = 4 animals; eight tubes), 12 weeks (n = 2 animals; four tubes), or 24 weeks (n = 2 animals; four tubes). Thereafter, the animals were killed and the fallopian tubes were harvested for histologic evaluation.

RESULTS

A single device was placed successfully in each fallopian tube. Fifteen of 16 devices (94%) remained in place throughout follow-up. One device migrated into the vagina at 2-week follow-up. Hysterosalpingography of the 15 tubes with occluders in place showed occlusion in seven of seven (100%) at 6 weeks, three of four (75%) at 12 weeks, and two of four (50%) at 24 weeks. Histologic evaluation revealed luminal occlusion by reorganized SIS containing macrophages, fibrocytes, and scant foreign-body giant cells. Only a mild inflammatory reaction was observed around the tube. In the animals with recanalization at 12 and 24 weeks, new channels were found alongside the original still-occluded fallopian tube lumen.

CONCLUSIONS

The original lumen of the fallopian tube was effectively occluded by the SIS occluder, which was remodeled within the fallopian tubes of rabbits. Partial peripheral recanalization was observed over time.

Preformed grafts of porcine small intestine submucosa (SIS) for bridging segmental bone defects

Previous studies suggest that fresh, morselized porcine small intestine submucosa (SIS) may have promise in the treatment of large bone defects. This study evaluated the bone regenerative potential of preformed tubular SIS grafts, designed to provide a scaffold for regeneration of diaphyseal bone. Critical length segmental defects in the femurs of male rats were either left unfilled (n = 11) or filled with morselized cancellous bone (n = 12), or spanned with intramedullary tubes (n = 12) or periosteal sleeves (n = 12) fabricated from SIS. All of the animals were euthanized 12 weeks postoperatively. Healing was assessed with biweekly radiographs, routine histology, and mechanical testing. Copious new bone formed in the defects of all of the animals treated with cancellous bone; 10 of the 12 animals in that group had healed their defects. In contrast, no new bone was formed in the defects left unfilled or treated with SIS; only fibrous tissue was found. In both of the SIS-treated groups, the SIS persisted at twelve weeks. The cellular response to the SIS involved a mild mononuclear infiltrate in the loose or delaminated superficial layers of the tubes and sleeves, with few cells in the deeper layers. The results of this study cast doubt on the ability of SIS to support or stimulate growth of bone across a critical length segmental bone defect. Additional work will be required to determine whether our results reflect the protocols used to prepare and fabricate the SIS grafts used in the study or the inherent inability of SIS to support new bone growth.

The use of small intestine submucosa in the repair of paraesophageal hernias: initial observations of a new technique

BACKGROUND

Recent reports suggest that when laparoscopy is used to repair paraesophageal hernias recurrence rates reach 20% to 40%. Tension-free hernia closure with synthetic mesh reduces recurrence but occasionally results in esophageal injury. We hypothesized that reinforcement of the hiatal closure with small intestine submucosa (SIS) mesh, in some unusually large hernias, might reduce recurrence rates without causing injury to the esophagus.

METHODS

From January 2001 to March 2002 we treated 18 large paraesophageal hernias via a laparoscopic approach. In 9 of the largest hernias (one type II and 8 type III, of which 1 was recurrent) the repair was reinforced with SIS mesh (Surgisis, Cook Surgical) and represent the subjects of this study. Nissen fundoplication with gastropexy was performed in all patients. Clinical follow-up ranged from 3 to 16 months (median 8). Every patient was evaluated with barium esophagram or endoscopy or both 1 to 8 months (median 2) postoperatively.

RESULTS

The presenting symptoms were postprandial pain/fullness (9 of 9), heartburn (4 of 9), anemia (4 of 9), dysphagia (3 of 9), regurgitation (3 of 9), and chest pain (3 of 9). One patient died of a hemorrhagic stroke within 30 days of the operation. Postoperatively, presenting symptoms resolved (83%) or improved (17%) in each of the remaining 8 patients. One patient required endoscopic dilation for mild dysphagia. Seven of 8 patients had a normal barium esophagram without evidence of hernia. One morbidly obese (body mass index = 47) patient had a small (2 cm) sliding hiatal hernia postoperatively. There were no other complications, and specifically no perforations or mesh erosions.

CONCLUSIONS

These observations suggest that the use of SIS in the repair of paraesophageal hernias is safe and may reduce recurrence. Longer follow-up and a randomized study are needed to validate these results.

Surgisis patch tracheoplasty in a rodent model for tracheal stenosis

BACKGROUND

Tracheal stenosis is a challenging surgical problem that can require reconstruction using autologous grafts or artificial stents. In this study, we evaluate the efficacy of Surgisis, a commercially available, biocompatible, acellular matrix, in the repair of a critical-size tracheal defect.

METHODS

A full-thickness defect (2 mm x 6 mm) was created in tracheal rings 4 through 6 in adult rats. A piece of 8-ply Surgisis (Cook; Bloomington, IN) was sutured to the edges of the defect with interrupted 8-0 polypropylene sutures. In control animals, the defect was closed primarily. The trachea was harvested at 4 weeks and prepared for histologic evaluation using conventional techniques. Cross-sectional area and perimeters were calculated using imaging software.

RESULTS

Tracheal defects without patch repair (n = 3) resulted in tracheal stenosis and immediate death. Animals that underwent Surgisis patch repair of tracheal defects (n = 10) tolerated the procedure well and had no audible stridor or evidence of respiratory distress. Eight of ten animals survived 4 weeks. The tracheal lumen was patent with no evidence of contracture or degradation of the Surgisis. Histologically, neovascularization of the Surgisis was noted with moderate inflammation. The surface of the Surgisis patch was covered ith a lining of ciliated epithelial cells.

CONCLUSION

In the rodent model, Surgisis appears to be an efficacious method for the patch repair of partial circumferential tracheal defects. Surgisis appears to be a safe and promising means of facilitating neovascularization and tissue regeneration. The long-term use of Surgisis warrants further investigation.

Decellularized dermal grafting in cleft palate repair

OBJECTIVE

To assess the efficacy of decellularized dermal grafting used as an adjunct to the performance of primary repair of wide cleft palates.

DESIGN

Retrospective review.

SETTING

Tertiary referral center for large managed care organization.

METHODS

Seven consecutive patients with clefts of the hard and soft palates wider than 15 mm as measured at the posterior edge of the hard palate. Palates were repaired in the standard 2-flap approach with intravelar veloplasty. The decellularized dermal graft (AlloDerm) was applied immediately deep to the oral mucosal closure. Patients were followed up with serial postoperative examination. Palates were assessed for dehiscence, fistula, infection, rejection, scarring, and contracture.

RESULTS

There were no fistulas. In 2 patients, the oral mucosa dehisced, exposing the dermal graft. In 2 other cases, nasal mucosal tears were inadvertently created during closure of the nasal layer. In all cases, the decellularized dermal graft mucosalized and, by clinical examination, became incorporated into the wound. There were no cases of local inflammation or infection. The degree of scarring and contracture was indistinguishable from the adjacent scar.

CONCLUSIONS

Decellularized dermal graft is safe and effective for use in primary closure of wide clefts involving the hard and soft palates. Its application to wide clefts otherwise at risk of fistula is justified. Its use in repair of an existing fistula is also promising.

The role of synthetic and biological prostheses in reconstructive pelvic floor surgery

PURPOSE OF REVIEW

Uterovaginal prolapse and urinary incontinence are common problems whose pathogenesis remains unclear. As life expectancy increases, significantly greater numbers of women will present with pelvic floor prolapse and incontinence requiring surgical intervention. Currently, the lifetime risk of undergoing prolapse or continence surgery in the USA is one in 11, and up to 30% of patients will require repeat prolapse and 10% repeat continence surgery. In an attempt to improve surgical outcomes and to preserve vaginal capacity and coital function, a number of synthetic and biological prostheses have been developed. This review aims to look at the controversies that exist as the 'ideal' prosthetic material is developed.

RECENT FINDINGS

The recent literature has reflected the increasing interest in the use of biological prostheses (Allograft/Xenograft) and synthetic absorbable meshes. There has been a focus on the risk factors for erosion seen with the use of synthetic non-absorbable material and a review of techniques for the reduction and management of this complication. The advent of mesh placement in minimally invasive continence surgery (tension-free vaginal tape, intravaginal sling, and Supra Public ARC) is now seeing surgical success to 5 years, but the reporting of complications remains inconsistent.

SUMMARY

The use of prosthetics in pelvic floor and continence surgery is an evolving field. Further randomized controlled trials are required to evaluate the role of both biological and synthetic prostheses in reconstructive surgery, to determine which type of prosthesis is most suitable for specific procedures. Prosthetic reinforcement should not be used to replace good surgical techniques.

Small intestinal submucosa as a tunica albuginea graft material

PURPOSE

We evaluated the morphological, immunological and functional response to small intestinal submucosa grafting of the tunica albuginea to determine its potential as a grafting material for penile surgery.

MATERIALS AND METHODS

Male New Zealand White rabbits underwent a sham procedure (6) or tunical excision and grafting with small intestinal submucosa (6). The erectile response to the intracavernous vasoactive agents sodium nitroprusside plus a papaverine, phentolamine and prostaglandin E1 combination (Sigma Chemical Co., St. Louis, Missouri) was evaluated 45-day postoperatively. The area under the graft was evaluated for stromal collagen and smooth muscle content by Masson's trichrome stain. Protein expression of smooth muscle specific alpha-actin and the inflammatory markers inducible nitric oxide synthase (NOS) and transforming growth factor-beta1 (TGF-beta1) was evaluated by immunohistochemical methods. Total RNA was extracted from the corpora cavernosum underlying the small intestinal submucosa graft and reverse transcriptase-polymerase chain reaction (RT-PCR) was done using an Access system (Promega, Madison, Wisconsin) with gene specific primers for inducible NOS, TGF-beta1 and vascular endothelial growth factor (VEGF).

RESULTS

Grafting of the tunica albuginea with small intestinal submucosa had no significant effect on the magnitude or duration of the erectile response to intracavernous vasoactive agents. Histological examination demonstrated no inflammatory changes in the tunica albuginea or corporeal tissue underlying the area of the small intestinal submucosa graft and there was no appreciable alteration in smooth muscle or collagen content. The 2 groups showed intense positive immunostaining to alpha-actin. Weak expression of TGF-beta1 predominantly associated with smooth muscle fibers was identified in the 2 groups of rabbits by immunostaining and RT-PCR. No significant inducible NOS was detected by immunostaining or RT-PCR in either group. Strong VEGF expression was observed in grafted rabbits. The most noticeable (3-fold) increase in expression was detected in splice variant 165.

CONCLUSIONS

Small intestinal submucosa grafting of the tunica albuginea preserves the duration and magnitude of the erectile response to vasoactive agents. This type of tunical grafting does not stimulate a significant inflammatory response, or cause corporeal fibrosis or loss of cavernous smooth muscle content. Stimulating VEGF may facilitate wound healing and the maintenance of normal erectile function.

Small intestinal submucosa as a bioscaffold for biliary tract regeneration

BACKGROUND

Porcine small intestinal submucosa (SIS) biograft is used as a bioscaffold for regeneration of a variety of tissues. To date, SIS has not been used as a biliary tract graft. The purpose of this study was to evaluate the feasibility of using SIS as a scaffold for bile duct tissue regeneration in a canine model.

METHODS

Fifteen, 25- to 35-kg mongrel dogs underwent midline laparotomy and exposure of the common bile duct. Nine dogs had a longitudinal choledochotomy and a 2- x 1-cm elliptical patch of 4-ply SIS placed using 6-0 polypropylene suture. Six dogs had the anterior two thirds of the bile duct resected and a 2- to 3-cm tubularized 4-ply SIS interposition graft placed. Dogs were killed at intervals ranging from 2 weeks to 5 months. Before killing, liver function tests (alkaline phosphatase [U/L] and total bilirubin [mg/dL]) were evaluated, cholangiograms were performed, and the bile duct was examined histologically.

RESULTS

Fourteen out of 15 dogs survived and were healthy at the time of killing. The one failure was a result of a bile leak in a patched animal. The SIS showed signs of incorporation with infiltration of native fibroblasts, blood vessels, and biliary mucosa within 2 weeks. Within 3 months the SIS graft was replaced with native collagen covered with a biliary epithelium. No changes occurred at 5-month follow-up. One animal with an interposition graft developed a stricture at the proximal anastomosis within 2 months. In the remaining dogs, liver enzymes were normal, and the caliber of the common bile duct remained normal.

CONCLUSIONS

SIS can be used for regeneration of bile duct tissue in a canine model. In 13 of 15 dogs SIS resulted in regeneration of canine common bile duct when used as a patch or as an interposition graft. The potential for the use of SIS as a patch for biliary stricturoplasty, or as an interposition graft for repair of complex biliary injuries is encouraging.

A pilot study to evaluate the effectiveness of small intestinal submucosa used to repair spinal ligaments in the goat

BACKGROUND CONTEXT

Destabilization of the lumbar spine results from sacrifice of the anterior longitudinal ligament and disc when removed for graft or cage placement. In a similar fashion, transection of the interspinous ligament during surgical approaches to the posterior spine may result in segmental instability. Such instability can cause abnormal motion or implant migration resulting in a higher incidence of pseudarthrosis. Small intestinal submucosa (SIS) is a naturally occurring extracellular collagen-based matrix, which is derived from porcine small intestine. SIS contains cytokines and growth factors and has been shown to act as a resorbable scaffold in vivo that promotes host soft tissue regeneration with little scar tissue formation. SIS can be manufactured in laminated sheets of various sizes and thicknesses for different indications. Successful applications of SIS in animals have included dural substitution, rotator cuff repair, vessel repair, abdominal and bladder wall repair, and others. However, SIS has not been investigated to determine its ability to facilitate regeneration of spinal ligaments.

PURPOSE

The purpose of this pilot study was to evaluate the efficacy of SIS as a barrier to prevent interbody device migration, and to act as a scaffold for regeneration of the anterior longitudinal ligament (ALL) and posterior interspinous ligament (PISL) in a goat model.

STUDY DESIGN/SETTING

The thoracolumbar spine of the goat was exposed surgically. After resection and removal of the ALL or PISL at alternating levels, either SIS was placed or no treatment was administered. New ligament formation and SIS resorption were monitored over a 12-week period.

OUTCOME MEASURES

Plain film radiographs and histomorphometry were used to assess the progress of healing over a 12-week time period.

METHODS

Four skeletally mature nubian-alpine crossbred goats were used in this study. Under general anesthesia, each T10 to L5 motion segment was exposed surgically. Both anterolateral and posterior approaches were performed simultaneously at each level. Anteriorly, alternating levels received either 1) anterior discectomy, sacrifice of ALL and placement of SIS (SIS group); 2) anterior discectomy, sacrifice of ALL and no SIS (surgical control group) or 3) no surgical intervention (nonoperative group). A solid interbody spacer was placed into the disc space after discectomy to deter spontaneous anterior interbody fusion. Posteriorly, alternating levels were treated with either 1) sacrifice of the PISL with placement of SIS (SIS group); 2) sacrifice of PISL and no SIS (surgical control group) or 3) no surgical intervention (nonoperative group). The SIS was secured to the adjacent superior and inferior spinous processes to create a tension-band effect. Animals were radiographed immediately postoperatively to confirm placement of interbody spacers and anchors and to serve as a baseline for monitoring interbody spacer positioning. After surgery, all animals were allowed unrestricted motion for 12 weeks. At the end of the 12-week period, animals were radiographed and euthanized. The lumbar spine was harvested en bloc and processed for decalcified histologic evaluation. The dorsal and ventral aspects of each motion segment were analyzed for signs of inflammation and scar tissue formation, residual SIS and regenerated ALL or PISL.

RESULTS

All animals tolerated the surgical procedure well, and there were no intraoperative or anesthesia-related complications. Twelve-week radiographs showed some evidence of ventral migration of the interbody spacers in several animals. Fifty percent (two of four) of spacers in surgical control group levels had migrated more than 10 mm (resulting in complete migration out of the disc space), whereas no spacers migrated completely out of levels with SIS placed. Gross analysis at necropsy indicated iatrogenic scar formation at operated levels, the degree of which was not different from surgical control group to SIS levels. Histologic evaluation of areas where the ALL had been removed indicated formation of organized fibrilar collagenous tissue that spanned the disc space at some levels where the SIS was placed. In some cases, the newly formed tissue was approximately the thickness of the ALL at the nonoperative group levels. The newly formed collagenous tissue was accompanied by sparse focal areas of inflammation, with small fragments of residual SIS at some levels. At surgical control group levels, there was a varying degree of connective tissue that ranged from moderately organized to randomly oriented with no significant signs of inflammation. Similarly, histologic analysis of some levels where SIS was placed posteriorly showed formation of organized collagenous tissues where the PISL had been removed.

CONCLUSIONS

In this model, the SIS patch was sufficient to prevent acute ventral migration of interbody spacers from the disc space. The extent of long-term healing and new tissue formation in the SIS group indicates that it may be efficacious as a reparative intervention for transected ligaments in the spine. Most SIS specimens showed formation of organized collagenous tissue, indicating a long-term potential for ligament formation. However, in this model, 12 weeks of postoperative healing is insufficient to assess the full potential of SIS as a spinal ligament repair. Further research that follows the healing process to a longer time point postoperatively may be necessary to fully understand the potential of SIS as a resorbable scaffold for tissue replacement.

Naturally occurring scaffolds for soft tissue repair and regeneration

Cell growth supports (i.e., scaffolds) that provide a conducive environment for normal cellular growth, differentiation, and angiogenesis are important components of tissue engineered grafts because rapid integration with the host is essential for long-term graft viability. While many of these scaffold materials are synthetic biodegradable polymers, others are naturally derived from mammalian tissue sources. Naturally occurring scaffold materials include small intestinal submucosa, acellular dermis, amniotic membrane tissue, cadaveric fascia, and the bladder acellular matrix graft. Upon implantation, these materials elicit a host-tissue response that initiates angiogenesis, encourages tissue deposition and culminates in restoration of structure and function specific to the grafted site. The sources, the methods of procurement and processing, and the effects of these naturally occurring materials on angiogenesis and tissue deposition are reviewed.

Technique of combined pubovaginal sling and cystocele repair using a single piece of cadaveric dermal graft

OBJECTIVES

To investigate the feasibility of using a single piece of cadaveric dermal allograft for the repair of stress urinary incontinence (SUI) with concurrent cystocele.

METHODS

Nineteen patients with combined SUI and symptomatic grade III cystoceles were treated. Eleven of 19 patients had undergone prior repairs for SUI. All patients underwent a combined pubovaginal sling procedure and cystocele repair using a single piece of cadaveric dermal allograft (3 x 7 cm). The single strip of dermal graft was placed in a longitudinal direction along the anterior vagina. The distal segment of the allograft supported the urethra, and the proximal portion supported the central cystocele defect and was sutured to the pubocervical fascia. The mean follow-up was 28 +/- 4 months and patients were monitored by physical examination, videourodynamic studies, and completion of the bladder bothersome visual analog scale.

RESULTS

Of the 19 patients, 1 developed an acute infection and failure of the graft after presenting with fever, discharge, dysuria, and incontinence. The autolysed graft was removed, and she subsequently underwent successful autologous fascial repair. Of the remaining 18 patients, 17 were cured of their SUI, including 10 who had had prior repairs, and 16 had no recurrence of cystocele and 2 had asymptomatic grade I and II cystoceles. One patient developed de novo detrusor instability that was successfully treated with anticholinergic medication. No cases of urethral obstruction occurred.

CONCLUSIONS

Although the follow-up was short, the use of a single piece of cadaveric dermal graft slings for concomitant pubovaginal sling and cystocele repair is feasible and simple to perform. At more than 2 years of follow-up, documented by videourodynamic studies, neither urethral obstruction nor symptomatic cystocele recurrence was found.

Resorbable bioscaffold for esophageal repair in a dog model

PURPOSE

Porcine-derived, xenogeneic extracellular matrix (ECM) derived from either the small intestinal submucosa (SIS) or urinary bladder submucosa (UBS) was used as a tissue scaffold for esophageal repair in a dog model.

METHODS

Patch defects measuring approximately 5 cm in length and encompassing 40% to 50% of the circumference of the esophagus or complete circumferential segmental defects measuring 5 cm in length were created by surgical resection in healthy adult female dogs. The defects were repaired with ECM scaffolds derived from either SIS or UBS. The animals were kept alive for periods ranging from 4 days to 15 months.

RESULTS

The xenogeneic scaffolds used for repair of the patch defects were resorbed completely within 30 to 60 days and showed replacement by skeletal muscle, which was oriented appropriately and contiguous with adjacent normal esophageal skeletal muscle, organized collagenous connective tissue, and a complete and intact squamous epithelium. No signs of clinical esophageal dysfunction were seen in any of the animals with the patch defect repair. The xenogeneic scaffolds configured into tubes for repair of the segmental defects all showed stricture within 45 days of surgery.

CONCLUSION

These ECMs show promise as a treatment option for esophageal repair, but stricture remains problematic for complete tube grafts.