Small intestinal submucosa: a rapidly resorbed bioscaffold for augmentation cystoplasty in a dog model

In-vivo autologous bladder muscular wall regeneration: application of tissue-engineered pericardium in a model of bladder as a bioreactor

PURPOSE

Tissue-engineered pericardium (TEP) is a collagen-rich matrix that has previously been shown to promote in vivo and in vitro tissue regeneration. We evaluated the potential of TEP as a source for the in-vivo creation of bladder muscular wall grafts. We used bladder wall as a bioreactor to create a natural environment for cellular growth and differentiation.

MATERIALS AND METHODS

Sixteen rabbits were divided into four groups. A control group underwent classical bladder autoaugmentation. Other groups underwent insertion of TEP between bladder mucosa and muscular layer: group 2 with insertion of TEP, group 3 with TEP over autologous bladder muscular wall fragments, and group 4 with autologous bladder smooth muscle cells (SMCs) seeded on TEP. After 4 and 8 weeks, grafts were biopsied for histopathological evaluations.

RESULTS

Frames from groups 3 and 4 demonstrated more organized muscular wall generation with a significantly higher number of CD34 + endothelial progenitor cells and CD31 + microvessels, and maintenance of α-smooth muscle actin expression through immunohistochemistry. Group 4 showed significant enhancement of SMC penetration to TEP. Although the fragment-seeded group required a simpler procedure, the cell-seeded group showed superior organization of the muscular layer on histopathology. We found a semi-organized muscular layer and new vessels in the margins of TEP in group 3, while there was a homogeneous pattern of SMCs and new vessels in both the margins and center of TEP in group 4.

CONCLUSIONS

This preliminary work has important functional and clinical implications, as it indicates that use of the autologous SMC seeding method may enhance the properties of TEP in terms of bladder wall regeneration.

Randomized comparison of OASIS wound matrix versus moist wound dressing in the treatment of difficult-to-heal wounds of mixed arterial/venous etiology

OBJECTIVE

In this study, a biological extracellular matrix was compared with a moist wound dressing to determine its effectiveness in the treatment of mixed arterial/venous and venous ulcers.

METHODS

Patients were evaluated for complete wound healing, time to dressing change, and formation of granulation tissue.

RESULTS

Extracellular matrix-treated ulcers achieved complete healing on average in 5.4 weeks as compared with 8.3 weeks for the control group treated with moist wound dressing (P = .02). At the primary time point evaluated (8 weeks), complete wound closure was achieved in 80% of extracellular matrix-treated ulcers compared with 65% of ulcers in the control group (P < .05). Statistically significant differences favoring the extracellular-matrix treatment group were also reported for time to dressing change (P < .05), and for percentage of granulation tissue formed (P < .05).

CONCLUSION

Overall, the biological extracellular matrix was more beneficial than moist wound dressings for the treatment of patients with mixed arterial/venous or venous ulcers.

The effect of source animal age upon extracellular matrix scaffold properties

Biologic scaffold materials composed of mammalian extracellular matrix (ECM) are commonly used for the repair and reconstruction of injured tissues. An important, but unexplored variable of biologic scaffolds is the age of the animal from which the ECM is prepared. The objective of the present study was to compare the structural, mechanical, and compositional properties of small intestinal submucosa (SIS)-ECM harvested from pigs that differed only in age. Degradation product bioactivity of these ECM materials was also examined. Results showed that there are distinct differences in each of these variables among the various age source ECM scaffolds. The strength and growth factors content of ECM from 3-week-old animals is less than that of ECM harvested from 12, 26 or >52-week-old animals. The elastic modulus of SIS-ECM for 3 week and >52-week-old source was less than that of the 12 and 26 week source. Degradation products from all age source ECMs were chemotactic for perivascular stem cells, with the 12 week source the most potent, while the oldest source caused the greatest increase in proliferation. In summary, distinct differences exist in the mechanical, structural, and biologic properties of SIS-ECM harvested from different aged animals.

Enhanced angiogenesis of modified porcine small intestinal submucosa with hyaluronic acid-poly(lactide-co-glycolide) nanoparticles: from fabrication to preclinical validation

Hyaluronic acid-poly(de-co-glycolide) nanoparticles (HA-PLGA NPs) were synthesized to stabilize the porous structure of porcine small intestinal submucosa (SIS), to improve surface biocompatibility and to enhance performance in tissue regeneration. HA-PLGA NPs were characterized for size, zeta potential, surface morphology, and HA loading. Human microvascular endothelial cells responded to HA-PLGA NPs and HA-PLGA modified SIS (HA-PLGA-SIS) with elevated cell proliferation. HA-PLGA-SIS significantly enhanced neo-vascularization in an in ovo chorioallantoic membrane angiogenesis model. The angiogenic capability of the newly fabricated HA-PLGA-SIS was tested in a canine bladder augmentation model. Urinary bladder augmentation was performed in beagle dogs following hemi-cystectomy using HA-PLGA-SIS. The regenerated bladder was harvested at 10 weeks post augmentation and vascularization was evaluated using CD31 immunohistochemical staining. Bladder regenerated with HA-PLGA-SIS had significantly higher vascular ingrowth compared to unmodified SIS. This study shows that HA-PLGA NPs may represent a new approach for modifying naturally derived SIS biomaterials in regenerative medicine.

Evaluation of gel spun silk-based biomaterials in a murine model of bladder augmentation

Currently, gastrointestinal segments are considered the gold standard for bladder reconstructive procedures. However, significant complications including chronic urinary tract infection, metabolic abnormalities, urinary stone formation, bowel dysfunction, and secondary malignancies are associated with this approach. Biomaterials derived from silk fibroin may represent a superior alternative due their robust mechanical properties, biodegradable features, and processing plasticity. In the present study, we evaluated the efficacy of a gel spun silk-based matrix for bladder augmentation in a murine model. Over the course of 70 d implantation period, H&E and Masson's trichrome (MTS) analysis revealed that silk matrices were capable of supporting both urothelial and smooth muscle regeneration at the defect site. Prominent uroplakin and contractile protein expression (α-actin, calponin, and SM22α) was evident by immunohistochemical analysis demonstrating maturation of the reconstituted bladder wall compartments. Gel spun silk matrices also elicited a minimal acute inflammatory reaction following 70 d of bladder integration, in contrast to parallel assessments of small intestinal submucosa (SIS) and poly-glycolic acid (PGA) matrices which routinely promoted evidence of fibrosis and chronic inflammatory responses. Voided stain on paper analysis revealed that silk augmented animals displayed similar voiding patterns in comparison to non surgical controls by 42 d of implantation. In addition, cystometric evaluations of augmented bladders at 70 d post-op demonstrated that silk scaffolds supported significant increases in bladder capacity and voided volume while maintaining similar degrees of compliance relative to the control group. These results provide evidence for the utility of gel spun silk-based matrices for functional bladder tissue engineering applications.

Nonthermal Irreversible Electroporation for Tissue Decellularization

Tissue scaffolding is a key component for tissue engineering, and the extracellular matrix (ECM) is nature’s ideal scaffold material. A conceptually different method is reported here for producing tissue scaffolds by decellularization of living tissues using nonthermal irreversible electroporation (NTIRE) pulsed electrical fields to cause nanoscale irreversible damage to the cell membrane in the targeted tissue while sparing the ECM and utilizing the body’s host response for decellularization. This study demonstrates that the method preserves the native tissue ECM and produces a scaffold that is functional and facilitates recellularization. A two-dimensional transient finite element solution of the Laplace and heat conduction equations was used to ensure that the electrical parameters used would not cause any thermal damage to the tissue scaffold. By performing NTIRE in vivo on the carotid artery, it is shown that in 3 days post NTIRE the immune system decellularizes the irreversible electroporated tissue and leaves behind a functional scaffold. In 7 days, there is evidence of endothelial regrowth, indicating that the artery scaffold maintained its function throughout the procedure and normal recellularization is taking place.

Clinical application of an acellular biologic scaffold for surgical repair of a large, traumatic quadriceps femoris muscle defect

Many battlefield injuries involve penetrating soft tissue trauma often accompanied by skeletal muscle defects, known as volumetric muscle loss. This article presents the first known case of a surgical technique involving an innovative tissue engineering approach for the repair of a large volumetric muscle loss. A 19-year-old Marine presented with large volumentric muscle loss of the right thigh as a result of an explosion. The patient reported muscle weakness with right knee extension, secondary to volumentric muscle loss, primarily involving the vastus medialis muscle. This persisted 3 years postinjury, despite extensive physical therapy. With all existing management options exhausted, restoration of a portion of the lost vastus medialis muscle was attempted by surgical implantation of a multi-layered scaffold composed of extracellular matrix derived from porcine intestinal submucossa. The patient had no complications, was discharged home on postoperative day 5, and resumed physical therapy after 4 weeks. Four months postoperatively, the patient demonstrated marked gains in isokinetic performance. Computer tomography indicated new tissue at the implant site. This approach offers a treatment option to a heretofore untreatable injury and will allow us to improve future surgical treatments for volumetric muscle loss.

Addition of nimesulide to small intestinal submucosa biomaterial inhibits postsurgical adhesiogenesis in rats

Adhesion formation is a common complication in abdominal surgery with incidence as high as 93% and small bowel obstruction a common complication. Because the extracellular matrix material, small intestinal submucosa (SIS), is commonly used in various surgical procedures, methods to inhibit adhesiogenesis are of great interest. This study was undertaken to determine if incorporation of nimesulide (NM), a selective cyclooxygenase (COX)-2 inhibitor, could reduce the extent and tenacity of intraabdominal adhesion formation associated with SIS implantation. Female Sprague-Dawley rats underwent a cecal abrasion surgical procedure to induce adhesiogenesis. Rats were either left untreated or treated by direct application over the injured cecum with polypropylene mesh (PPM); SIS; SIS containing a low dose of NM; or SIS containing a high dose of NM. Rats were euthanized 21 days later, and adhesion extent and tenacity were evaluated using standard scales (0 = minimal adhesiogenesis; 4 = severe adhesiogenesis). Addition of NM to SIS resulted in a significant (p < 0.05) reduction in adhesion extent and in a similar reduction in adhesion tenacity for SIS containing a low dose of NM. Adhesions typically extended from the abraded cecal surface to the body wall and were characterized histologically by fibrous tissue adherent to the cecal wall. In conclusion, addition of the nonsteroidal anti-inflammatory, COX-2 selective drug, NM, to SIS attenuates adhesion extent and tenacity when compared with surgical placement of SIS or PPM alone.

Assessment of the efficacy of the rectovaginal button fistula plug for the treatment of ileal pouch-vaginal and rectovaginal fistulas

BACKGROUND

The treatment of rectovaginal and ileal pouch-vaginal fistulas remains a challenging problem for the colorectal surgeon. The aim of this study was to assess the short-term efficacy of the new Surgisis Biodesign rectovaginal button fistula plug in patients with such fistulas.

METHODS

Between May 2008 and September 2008, patients with confirmed rectovaginal and ileal pouch-vaginal fistulas with backgrounds of inflammatory bowel disease were treated with the button fistula plug. The fistulas were assessed by magnetic resonance imaging and/or examination under anesthesia before the procedure.

RESULTS

Twelve patients with a median age of 36 (range, 29-42) years underwent a total of 20 plug insertions. Five patients had confirmed rectovaginal fistulas and seven patients had ileal pouch-vaginal fistulas. At a median follow-up of 15 (interquartile range, 10-21) weeks, 7 of 12 patients (58%) had been treated successfully. Seven of the 20 plugs that were inserted (35%) were successful. This equates to the successful treatment of three of five (60%) of the rectovaginal fistulas, and four of seven (57%) of the ileal pouch-vaginal fistulas. Of the six patients who initially failed, a repeat procedure was performed of which one was successful. Two patients underwent a third repeat procedure, which was again unsuccessful in both cases. The success rate of these eight repeat plug insertions was therefore 12.5%. All plug failures were the result of dislodgement of the plug. There was no morbidity in our series.

CONCLUSIONS

The new button fistula plug successfully treated 7 of 12 (58%) rectovaginal and ileal pouch-vaginal fistulas.

Myogenic differentiation of human bone marrow mesenchymal stem cells on a 3D nano fibrous scaffold for bladder tissue engineering

Current strategies for engineering bladder tissues include a bladder biopsy for in vitro cell expansion for use in reconstructive procedures. However, this approach cannot be used in patients with bladder cancer who need a complete bladder replacement. Bone marrow mesenchymal stem cells (BMSC) might be an alternative cell source to better meet this need. We investigated the effects of soluble growth factors, bladder extracellular matrix (ECM), and 3D dynamic culture on cell proliferation and differentiation of human BMSC into smooth muscle cells (SMC). Myogenic growth factors (PDGF-BB and TGF-beta1) alone, or combined either with bladder ECM or dynamic cultures, induced BMSC to express smooth muscle-specific genes and proteins. Either ECM or the dynamic culture alone promoted cell proliferation but did not induce myogenic differentiation of BMSC. A highly porous poly-l-lactic acid (PLLA) scaffold provided a 3D structure for maximizing the cell-matrix penetration, maintained myogenic differentiation of the induced BMSC, and promoted tissue remolding with rich capillary formation in vivo. Our results demonstrate that myogenic-differentiated BMSC seeded on a nano fibrous PLLA scaffold can be potentially used for cell-based tissue engineering for bladder cancer patients requiring cystoplasty.

Regeneration of Uterine Horn Using Porcine Small Intestinal Submucosa Grafts in Rabbits

Tubal factor infertility may be reversed using porcine small-intestinal submucosa (SIS). The method uses as a model the New Zealand White rabbit uerine horn. In surgery, SIS grafts were prepared from porcine jejunum; the uterine horn segment was resected and a graft was placed; then the contralateral adnexa was resected. Fecundability was tested with natural mating. Three out of six rabbits became pregnant. Gross and microscopic examination confirmed regeneration of all tissue layers. Thus, this study determined that SIS facilitates successful regeneration of uterine horn morphology in a manner similar to that observed in other tissues and species.

Histologic analysis of acellular dermal matrix in the treatment of anal fistula in an animal model

BACKGROUND

Human acellular dermal matrix (ADM) has been used successfully for the treatment of severe burns, ureter support, and abdominal wall reconstruction. This study was designed to evaluate the mechanism of ADM in the closure of anal fistula in an experimental porcine model.

STUDY DESIGN

The fistula-in-ano model was created in the porcine model and treated with ADM in 14 animals. Fistula specimens were obtained at hours 12 and 24 and on days 3, 7, 14, 28, 60. Hematoxylin and eosin staining, Masson trichrome staining, and immunohistochemical staining for alpha smooth muscle actin and matrix metalloproteinase 9 were performed.

RESULTS

The cell density increased from hour 12 to day 7 and decreased from day 7 to day 28 (p < 0.001). Mature vessels stained with alpha smooth muscle actin were identified at day 7. Alpha smooth muscle actin-positive myofibroblasts were found in clusters at the edge of the ADM at day 7. The density of vessels (p < 0.001) and myofibroblasts (p < 0.001) increased from day 7 to day 14. The density of matrix metalloproteinase 9 increased from hour 12 to day 7 and decreased from day 14 to day 60 (p < 0.001). Partially organized bundles of muscle were found by day 60.

CONCLUSIONS

We suggest that ADM is a reasonable new option for closure of anal fistulas. Anal fistulas begin to heal as early as 12 hours, and day 7 may be an important time point to judge whether the fistula healed preliminarily or not. The ability of ADM to become vascularized and remodeled by autologous cells may be advantageous for anal fistula healing.

Constructive remodeling of biologic scaffolds is dependent on early exposure to physiologic bladder filling in a canine partial cystectomy model

Biologic scaffolds composed of extracellular matrix (ECM) have been used to facilitate the constructive remodeling of several tissue types. Previous studies suggest that the ECM scaffold remodeling process is dependent on microenvironmental factors, including tissue-specific biomechanical loading. The objective of the present study was to evaluate the effects of long-term catheterization (LTC), with its associated inhibition of bladder filling and physiologic biomechanical loading, on ECM scaffold remodeling following partial cystectomy in a canine model. Reconstruction of the partial cystectomy site was performed using ECM scaffolds prepared from porcine small intestinal submucosa (SIS) or porcine urinary bladder matrix (UBM). Animals were randomly assigned to either a long-term catheterization (LTC) group (n=5, catheterized 28 d) or a short-term catheterization group (STC, n=5, catheterized 24 h), and scaffold remodeling was assessed by histologic methods at 4 and 12 wk postoperatively. By 4 wk, animals in the STC group showed a well-developed and highly differentiated urothelium, a robust vascularization network, abundant smooth muscle actin (SMA), and smooth muscle myosin heavy chain (smMHC) expressing spindle-shaped cells, and many neuronal processes associated with newly formed arterioles. In contrast, at 4 wk the scaffolds in LTC animals were not epithelialized, and did not express neuronal markers. The scaffolds in the LTC group developed a dense granulation tissue containing SMA+, smMHC-, spindle-shaped cells that were morphologically and phenotypically consistent with myofibroblasts, but not smooth muscle cells. By 12 wk postoperatively, the ECM scaffolds in the STC animals showed a constructive remodeling response, with a differentiated urothelium and islands of smooth muscle cells within the remodeled scaffold. In contrast, at 12 wk the scaffolds in LTC animals had a remodeling response more consistent with fibrosis even though catheters had been removed 8 wk earlier. These findings show that early exposure of site-appropriate mechanical loading (i.e., bladder filling) mediates a constructive remodeling response after ECM repair in a canine partial cystectomy model.

Rabbit Ear Cartilage Regeneration With a Small Intestinal Submucosa Graft

OBJECTIVES/HYPOTHESIS

The objective was to demonstrate that interpositional grafting with porcine small intestinal submucosa promotes cartilage regeneration following excision of rabbit auricular cartilage.

STUDY DESIGN

Blinded, controlled study.

METHODS

Eight New Zealand white rabbits underwent excision of auricular cartilage on two sites with and two sites without preservation of perichondrium. Porcine small intestinal submucosa was implanted into one site with and one site without intact perichondrium. Remaining sites served as control sites. Histological assessment was performed at 3 (n = 4) and 6 (n = 3) months and at 1 year (n = 1) after grafting.

RESULTS

Histological evaluation showed cartilage regeneration accompanied by chronic inflammation in areas in which porcine small intestinal submucosa was implanted between layers of intact perichondrium. Other sites failed to show significant cartilage regeneration.

CONCLUSION

The results of the study using porcine small intestinal submucosa as a bioscaffold for cartilage regeneration are promising and justify further animal and human studies.

Small intestinal submucosa as a bioscaffold for tissue regeneration in defects of the colonic wall

BACKGROUND

Small intestinal submucosa (SIS) has proved considerable regenerative capacity for repair of bowel wall defects at different locations. This study assesses the effectiveness of SIS in the repair of defects at a gastrointestinal location with strong bacterial contamination.

METHODS

Fourteen domestic pigs had a 4.5 x 1.5 cm full-thickness defect created on the wall of the descending colon. Repair was done by suturing an SIS patch to the defect. Grafts were harvested after 30, 60, and 90 days. Outcomes were evaluated on the basis of animal survival, clinical course, and macroscopic, histological, and immunohistochemical assessment.

RESULTS

All animals survived the scheduled observation period. No patch failure and no postoperative leakage occurred. No luminal narrowing occurred at SIS-patched colon. Morphometric examination revealed contraction of the patched area of 77% after 30 days and more than 90% after 60 and 90 days. By 60 and 90 days, all animals showed mucosal regeneration at the margins of the graft. By 90 days, regeneration of smooth muscle cells was present at the original site of the muscularis mucosae. None of the reconstructed areas showed complete mucosal coverage or regeneration of a structured muscular layer.

CONCLUSION

SIS can be used effectively for patch repair of colonic defects in a porcine model. Distinctive contraction of the reconstructed area and limited architectural regeneration of the bowel wall suggest limitation of morphologic regenerative capacities in large-bowel regeneration.

Chemoattractant activity of degradation products of fetal and adult skin extracellular matrix for keratinocyte progenitor cells

Biological scaffolds composed of naturally occurring extracellular matrix (ECM) have been utilized as templates for the constructive remodelling of numerous tissues in preclinical studies and human clinical applications. The mechanisms by which ECM induces constructive remodelling are not well understood, but it appears that the degradation products of ECM scaffolds may play key roles in cell recruitment. The objective of the present study was to investigate the effects of age and species of the tissue from which ECM is harvested on the chemoattractant activity of degradation products of ECM for human keratinocyte stem and progenitor cells. Adult human skin ECM, fetal human skin ECM and adult porcine skin ECM were prepared, enzymatically digested, characterized by SDS-PAGE and evaluated for in vitro chemoattractant activity for human keratinocyte progenitor and stem cells (HEKn). Degradation products of human fetal skin ECM showed greater chemoattractant activity than human adult skin ECM degradation products for the HEKn. Degradation products of porcine adult skin ECM showed greater chemoattractant activity than human adult skin ECM. The human fetal skin ECM degradation products showed the strongest chemoattractant activity for the HEKn. The findings of this study support the concept that the mechanism of ECM scaffold remodelling involves the recruitment of lineage-directed progenitor cells by scaffold degradation products, and that both the age and species of the tissue from which the ECM is harvested have an effect upon this chemoattractant potential.

Nerve distribution in rat urinary bladder after incorporation of acellular matrix graft or subtotal cystectomy

OBJECTIVE

In the treatment of reduced bladder capacity, matrix grafts have been used as a scaffold into which cell elements from the native bladder grow, eventually forming a new bladder segment. Functioning motor nerve endings in such segments in the rat have been demonstrated, although little is known about nerve distribution. We compare the pattern of nerve distribution in scaffold-augmented rat bladders with that in bladders regrown after subtotal cystectomy and that in control bladders.

MATERIAL AND METHODS

Female Sprague-Dawley rats were either subtotally cystectomized (n=7) or had a part of the bladder dome replaced by an acellular collagen (small intestinal submucosa) matrix graft (n=10). Fourteen age-matched, unoperated animals were used as controls. Two and a half to 10 months after surgery the bladders were stained for acetylcholinesterase and studied in wholemounts.

RESULTS

No ganglion neurons were observed in any of the bladders. On their ventral side the control bladders showed longitudinal nerve trunks, running in parallel along the longitudinally oriented muscle bundles, while on the lateral and dorsal aspects the nerves were thinner, more irregularly arranged and frequently branched. In the bladders regrown after subtotal cystectomy, the ventral nerves were seen running obliquely to the still longitudinally oriented muscle bundles, resembling the pattern of the normal bladder base; the pattern of the dorsolateral nerves was the same as that in the controls. In the matrix bladders, the muscle and nerve patterns in the native part were the same as those in controls. Muscle bundles were growing into the matrix, accompanied by nerves, which showed limited branching when entering the matrix, usually running in parallel to the muscle, but then branching within the matrix.

CONCLUSIONS

The nerves in the matrix grafts and the regrown parts of the subtotally cystectomized bladders derive from preexisting nerves in the bladder. In neither case does the nerve trunk or muscle bundle arrangement fully attain the pattern found in normal bladders.

Collagen fistula plug for the treatment of anal fistulas

PURPOSE

This study was designed to evaluate the efficacy of the Surgisis (Anal Fistula Plug) in multiple patients at our institution and present early clinical results along with notable clinical observations from our experience.

METHODS

This was a prospective analysis of all patients who received the Anal Fistula Plug for treatment of anorectal fistulas between April 2006 and February 2007. All tracts were irrigated with peroxide, the plug was inserted in the tract, and buried at the internal opening with 2-0 vicryl and mucosal advancement flap. Statistical analysis was performed with Fisher's exact test.

RESULTS

Forty-five patients were treated with the Anal Fistula Plug and one patient was lost to follow-up. There were 27 males and 17 females with average age of 44.1 years treated for simple (n = 24) or complex (n = 20) fistulas. Preliminary results indicated an 84 percent healing rate by 3 to 8 weeks postoperatively, which progressively declined from 72.7 percent at 8 weeks to 62.4 percent at 12 weeks and 54.6 percent at a median follow-up of 6.5 (range, 3-13) months. Long-term Anal Fistula Plug closure rate was significantly higher in patients with simple than complex fistulas (70.8 vs. 35 percent; P < 0.02) and with non-Crohn's disease vs. Crohn's disease (66.7 vs. 26.6 percent; P < 0.02). Patients with two successive plug placements had significantly lower closure rates than patients who underwent placement of the plug once (12.5 vs. 63.9 percent; P < 0.02). No significant difference in closure rates were found between patients with one vs. multiple fistula tracts. Postoperative complications included perianal abscess in five patients (3 Crohn's disease, 2 non-Crohn's disease).

CONCLUSIONS

Anal Fistula Plug is most successful in the treatment of simple anorectal fistulas but is associated with a high failure rate in complex fistula and particularly in patients with Crohn's disease. Repeat plug placement is associated with increased failure. Given the relatively low morbidity associated with the procedure, Anal Fistula Plug should be considered as a first-line treatment for patients with simple fistulas and as an alternative in selected patients with complex fistulas.

Lip augmentation with porcine small intestinal submucosa

OBJECTIVE

To relate our initial experience using an acellular, soft tissue matrix derived from porcine small intestinal submucosa (Surgisis; Cook Biotech Inc, West Lafayette, Indiana) for lip augmentation.

DESIGN

A prospective, uncontrolled case series examining the results of lip augmentation using Surgisis in patients presenting to an academic otolaryngology/facial plastic surgery office.

RESULTS

Nineteen Surgisis implants were placed in 8 patients. All patients tolerated the procedure and denied unnatural sensations or complications at any interval. Adverse events included transient erythema and 1 case of local cellulitis treated effectively with oral antibiotics. Four patients were satisfied with the procedure and 4 patients requested greater augmentation. Six-month follow-up was reported, and preoperative and postoperative photography was used in all cases.

CONCLUSIONS

Short-term lip augmentation was achieved in all 8 patients (4 patients had multiple strands placed). This study demonstrates technical ease and early safety. Surgisis should serve as scaffolding for ingrowth of striated muscle of the lip, potentially providing long-term augmentation. This study introduces Surgisis as a novel implant for lip augmentation.

Reconstructive cranioplasty using a porcine small intestinal submucosal graft

A six-year-old border collie was presented with a solid mass on the dorsal cranium. Histological examination showed the mass to be a multilobular tumour of bone. A magnetic resonance imaging scan confirmed deformation of the dorsal cranium with compression of the cerebral hemispheres. A craniotomy was performed to excise the mass and overlying skin, resulting in a substantial deficit of calvarium and skin. A cranioplasty using a small intestinal submucosal (SIS) graft was performed to reconstruct the calvarial defect. A local myocutaneous advancement flap was elevated and positioned over the cranioplasty to close the skin deficit. The outcome of this reconstruction was aesthetic and functional. The small intestinal submucosal graft provided satisfactory mechanical support and was a suitable physical barrier in place of the calvarial bone. Histological examination of the small intestinal submucosal graft 128 days after implantation showed that the graft had been replaced by a dense network of collagenous tissue, with small focal areas of partially mineralised woven bone merging with a fibrocartilaginous matrix of the deeper margin. Histological examination also confirmed regrowth of the multilobular tumour of bone in the region of the small intestinal submucosal graft indicating that it is only a suitable implant if adequate surgical margins are obtained.

The incorporation of poly(lactic-co-glycolic) acid nanoparticles into porcine small intestinal submucosa biomaterials

Small intestinal submucosa (SIS) derived from porcine small intestine has been intensively studied for its capacity in repairing and regenerating wounded and dysfunctional tissues. However, SIS suffers from a large spectrum of heterogeneity in microarchitecture leading to inconsistent results. In this study, we introduced nanoparticles (NPs) to SIS with an intention of decreasing the heterogeneity and improving the consistency of this biomaterial. As determined by scanning electron microscopy and urea permeability, the optimum NP size was estimated to be between 200 nm and 500 nm using commercial monodisperse latex spheres. The concentration of NPs that is required to alter pore sizes of SIS as determined by urea permeability was estimated to be 1 mg/ml 260 nm poly(lactic-co-glycolic) acid (PLGA) NPs. The 1mg/ml PLGA NPs loaded in the SIS did not change the tensile properties of the unmodified SIS or even alter pH values in a cell culture environment. More importantly, PLGA NP modified SIS did not affect human mammary endothelial cells (HMEC-1) morphology or adhesion, but actually enhanced HEMC-1 cell growth.

Experimental evaluation of four biologic prostheses for ventral hernia repair

PURPOSE

To evaluate two bioprostheses derived from bovine pericardium, one cross-linked (Peri-Guard) and the other non-cross-linked (Veritas), and to compare them with Alloderm and Permacol for abdominal wall repair.

METHODS

The four prostheses were tested in acute and chronic hernia models. Prostheses were either sutured to the edge of the abdominal wall defect (inlay) or secured as an underlay with surgical tacks. Evaluation at 3 and 6 months included adhesion formation, defect area size and thickness, tensile strength, and histology.

RESULTS

Mean adhesion coverage area ranged from 25 to 31%. The two cross-linked materials, Permacol and Peri-Guard, showed greater tensile strength. Significant defect contraction followed repair with Veritas, whereas Alloderm stretched. All prostheses had cellular ingrowth and neovascularization by 3 months. No significant differences were found in prosthesis to abdominal wall breaking strength. Operative site infection occurred in six animals (5 Peri-Guard, 1 Veritas), and overlying skin ulceration in six others (6 Peri-Guard).

CONCLUSIONS

Permacol provided a strong and durable repair for up to six months. Peri-Guard was equally strong but prone to infection and to skin ulceration. With time, Veritas and Alloderm lost tensile strength associated with marked thinning and with hernia-like bulging in the case of Alloderm.

Small intestinal submucosa (SIS) in the repair of a cecal wound in unprepared bowel in rats

PURPOSE

Porcine-derived small intestinal submucosa (SIS) has been accepted as an acellular matrix for tissue regeneration. However, its use for remodeling gastrointestinal defects has been poorly investigated. Our previous study of the rodent stomach has demonstrated that the SIS stimulates regeneration of native tissue under acidic conditions. The purpose of this paper was to investigate the feasibility of using SIS as a bioscaffold for a colonic defect in unprepared bowel.

METHODS

A 1 x 1-cm whole layer was excised on the anterior wall of the cecum in 24 rats, followed by onlay repair with SIS. Measurement outcomes included animal survival, mesh stability in situ, and histologic evaluation at 3 weeks and 6 months.

RESULTS

Rats showed a significant weight gain and had no evidence of postoperative leakage. All wounds were secured and associated with either omental or other fatty adhesions. Histological findings revealed that intact mucosa covered the area of the graft in all cases 6 months after surgery and that the defect was completely replaced by the normal constituents (mucosa, muscle, and nerve cells) of the bowel wall.

CONCLUSIONS

SIS was largely successful in promoting healing in a cecal wound in unprepared bowel and serving as a bioscaffold for regeneration of the native colonic tissue. Small intestinal submucosa may be useful in surgical anastomoses to promote healing and presumably prevent leakage.

Commercially available extracellular matrix materials for rotator cuff repairs: state of the art and future trends

Rotator cuff tears, a common source of shoulder pathology, are often the cause of debilitating shoulder pain, reduced shoulder function and compromised joint mechanics. The treatment, evaluation and management of this disease puts an annual financial burden of 3 billion US dollars on the US economy. Despite surgical advances, there is a high rate of recurrent tears ranging (20-70%) after surgical repair, particularly for chronic, large to massive cuff tears. The inability to obtain a high healing rate in these tears has fueled investigation in the use of extracellular matrix (ECM) derived materials as a scaffolds for rotator cuff tendon repair and regeneration. The present paper reviews the current state of knowledge regarding the mechanical and biological characteristics of commercially available ECM materials, delineates indications for their clinical use and suggests future directions in developing ECM scaffolds for rotator cuff repair.

Repair of experimental Achilles tenotomy with porcine renal capsule material in a rat model

Porcine small intestinal submucosa (SIS) is a collagenous acellular matrix which has found substantial utility as a tissue growth scaffold. In the present study, the utility of porcine renal capsule matrix (RCM) was compared to SIS in a rat Achilles tenotomy repair model. Groups of rats underwent surgical tenotomy followed by either no repair, repair with a SIS graft, or repair with a RCM graft. The weight-bearing ability of the manipulated limb was evaluated for 10 days following surgery using a subjective scale. Tenotomy sites sampled 28 days after surgery were numerically graded for degree of histologic change. There were no statistically significant differences between groups with respect to return to weight-bearing ability (p >or= 0.05) or degree of histologic change (p >or= 0.001); however, a non-significant trend suggested that rats treated with SIS or RCM experienced a faster return to limb function than untreated rats, and RCM-treated rats had slightly higher scores for degree of histologic change, suggesting a more rapid repair of the tenotomy site than in SIS-treated or untreated rats. The harvested tenotomy sites in all treatment groups were characterized by marked fibroplasia and presence of macrophages. Remnants of SIS surrounded by macrophages and multi-nucleated giant cells were still present in some rats, however remnants of RCM were not observed, suggesting more rapid incorporation of RCM. The results show that RCM is equivalent to SIS as a material for repair of Achilles tendon injury and merits further study in other tendon injury models.

Degradation and remodeling of small intestinal submucosa in canine Achilles tendon repair

BACKGROUND

Extracellular matrix derived from porcine small intestinal submucosa is used for the repair of musculotendinous tissues. Preclinical evaluation and clinical use have suggested that small intestinal submucosa extracellular matrix degrades rapidly after implantation and can be replaced by host tissue that is functionally and histologically similar to the normal tissue.

METHODS

The present study analyzed the temporal degradation of a ten-layer multilaminate device of small intestinal submucosa extracellular matrix used for the repair of canine Achilles tendon and examined the corresponding histological appearance of the remodeled tissue during the course of scaffold degradation. Devices were fabricated from small intestinal submucosa extracellular matrix labeled with 14C. The amount of 14C remaining in the remodeled graft was measured by liquid scintillation counting at three, seven, fourteen, twenty-eight, sixty, and ninety days after surgery. Blood, urine, feces, and other parenchymal tissues were also harvested to determine the fate of scaffold degradation products. Tissue specimens were prepared for routine histological analysis to examine the morphology of the remodeled graft at each time-point.

RESULTS

The small intestinal submucosa extracellular matrix graft degraded rapidly, with approximately 60% of the mass lost by one month after surgery, and the graft was completely resorbed by three months after surgery. The graft supported rapid cellular infiltration and host tissue ingrowth. By ninety days after surgery, the remodeled small intestinal submucosa extracellular matrix consisted of a dense collagenous tissue with organization, cellularity, and vascularity similar to that of normal tendon.

CONCLUSIONS

Small intestinal submucosa extracellular matrix is rapidly degraded after implantation for the repair of a musculotendinous tissue in this canine Achilles tendon repair model and is replaced by the deposition and organization of host tissue that is histologically similar to that of normal tissue.

Development and characterisation of a full-thickness acellular porcine bladder matrix for tissue engineering

The aim of this study was to produce a natural, acellular matrix from porcine bladder tissue for use as a scaffold in developing a tissue-engineered bladder replacement. Full-thickness, intact porcine bladders were decellularised by distention and immersion in hypotonic buffer containing 0.1% (w/v) SDS and nuclease enzymes. Histological analysis of the resultant matrices showed they were completely acellular; that the major structural proteins had been retained and that there were some residual poorly soluble intracellular proteins. The amount of DNA per mg dry weight of fresh porcine bladder was 2.8 (+/-0.1) microg/mg compared to 0.1 (+/-0.1) microg/mg in decellularised bladder and biochemical analysis showed proportional differences in the hydroxyproline and glycosaminoglycan content of the tissue before and after decellularisation. Uniaxial tensile testing indicated that decellularisation did not significantly compromise the ultimate tensile strength of the tissue. There was, however, an increase in the collagen and elastin phase slopes indicating decreased extensibility. Cytotoxicity assays using porcine smooth muscle cell cultures excluded the presence of soluble toxins in the biomaterial. In summary, a full-thickness natural acellular matrix retaining the major structural components and strength of the urinary bladder has been successfully developed. The matrix is biocompatible with bladder-derived cells and has potential for use in urological surgery and tissue-engineering applications.

Abdominal wall reconstruction using biological tissue grafts: present status and future opportunities

Surgeons often encounter the challenge of treating acquired abdominal wall defects following abdominal surgery. The current standard of practice is to repair most defects using permanent synthetic mesh material. Mesh augments the strength of the weakened abdominal wall fascia and enables the hernia repair to be performed in a tension-free manner. However, there is a risk of acute and/or chronic infection, fistula formation and chronic abdominal wall pain with the use of permanent mesh materials, which can lead to more complex operations. As a means to avoid such problems, surgeons are turning increasingly to the use of xenogenic and allogenic materials for the repair of abdominal wall defects. Their rapid evolution and introduction into the clinical operating room is leading to a new era in abdominal wall reconstruction. There are promising, albeit limited, clinical data with short-term follow-up for only a few of the many biological tissue grafts that are being promoted currently for the repair of abdominal hernias. Additional clinical studies are required to better understand the long-term efficacy and limitations of these materials.

Different Types of Scaffolds for Reconstruction of the Urinary Tract by Tissue Engineering

INTRODUCTION

Tissue engineering is an important and expanding field in reconstructive surgery. The ideal biomaterial for urologic tissue engineering should be biodegradable and support autologous cell growth. We examined different scaffolds to select the ideal material for the reconstruction of the bladder wall by tissue engineering.

MATERIALS AND METHODS

We seeded mouse fibroblasts and human keratinocytes in a co-culture model on 13 different scaffolds. The cell-seeded scaffolds were fixed and processed for electron microscopy, hematoxylin and eosin stain, and immunohistochemistry. Cell density and epithelial cell layers were evaluated utilizing a computer-assisted optical measurement system.

RESULTS

Depending on the growth pattern, scaffolds were classified into the following three distinct scaffold types: carrier-type scaffolds with very small pore sizes and no ingrowth of the cells. This scaffold type induces a well-differentiated epithelium. Fleece-type scaffolds with fibers and huge pores. We found cellular growth inside the scaffold but no epithelium on top of it. Sponge-type scaffolds with pores between 20 and 40 microm. Cellular growth was observed inside the scaffold and well-differentiated epithelium on top of it.

CONCLUSION

To our knowledge, this is the first time three distinct scaffold types have been reported. All types supported the cell growth. The structure of the scaffolds affects the pattern of cell growth.

Cell responses to biomimetic protein scaffolds used in tissue repair and engineering

Basic science research in tissue engineering and regenerative medicine aims to investigate and understand the deposition, growth, and remodeling of tissues by drawing together approaches from a range of disciplines. This review discusses approaches that use biomimetic proteins and cellular therapies, both in the development of clinical products and of model platforms for scientific investigation. Current clinical approaches to repairing skin, bone, nerve, heart valves, blood vessels, ligaments, and tendons are described and their limitations identified. Opportunities and key questions for achieving clinical goals are discussed through commonly used examples of biomimetic scaffolds: collagen, fibrin, fibronectin, and silk. The key questions addressed by three-dimensional culture models, biomimetic materials, surface chemistry, topography, and their interaction with cells in terms of durotaxis, mechano-regulation, and complex spatial cueing are reviewed to give context to future strategies for biomimetic technology.

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.

Extracellular matrix bioscaffolds for orthopaedic applications. A comparative histologic study

BACKGROUND

Biologic scaffold materials prepared from extracellular matrix are currently available for the surgical repair of damaged or missing musculotendinous tissue. These scaffolds differ in their species and tissue of origin, methods of processing, and methods of terminal sterilization. The purpose of the present study was to evaluate the host-tissue morphologic response to five commercially available extracellular matrix-derived biologic scaffolds used for orthopaedic soft-tissue repair in a rodent model.

METHODS

One hundred twenty-six Sprague-Dawley rats were divided into six groups of twenty-one animals each. A defect was created in the musculotendinous tissue of the abdominal wall of each animal and then was repaired with one of five different scaffold materials (GraftJacket, Restore, CuffPatch, TissueMend, Permacol) or with the excised autologous tissue. Three animals from each group were killed at one of seven time-points after surgery (two, four, seven, fourteen, twenty-eight, fifty-six, and 112 days), and the specimens were examined with histologic and morphologic methods. The degree of cellular infiltration, multinucleated giant cell presence, vascularity, and organization of the replacement connective tissue were evaluated with semiquantitative methods.

RESULTS

Each device elicited a distinct morphologic response that differed with respect to cellularity (p<0.001), vascularity (p<0.01), the presence of multinucleated giant cells (p<0.01), and organization of the remodeled tissue (p<0.01) at or after the Day 7 time-point. More rapidly degraded devices such as Restore and autologous tissue showed the greatest amount of cellular infiltration, especially at the early time-points. Devices that degraded slowly, such as CuffPatch, TissueMend, and Permacol, were associated with the presence of foreign-body giant cells, chronic inflammation, and/or the accumulation of dense, poorly organized fibrous tissue.

CONCLUSIONS

Biologic scaffold materials composed of extracellular matrix elicit distinct host-tissue histologic and morphologic responses, depending on species of origin, tissue of origin, processing methods, and/or method of terminal sterilization.

Management of complicated gastroschisis with porcine small intestinal submucosa and negative pressure wound therapy

INTRODUCTION

In almost all cases of gastroschisis, fascial closure may be achieved primarily or after silo reduction. Rarely, fascial and skin closure are impossible. We report our experience with visceral coverage in complicated cases of gastroschisis with porcine small intestinal submucosa (SIS) augmented by negative pressure wound therapy (NPWT).

METHODS

Over a 3-year period, 55 infants with gastroschisis were managed. In 3 of these cases, fascia and skin could not be approximated safely after complete reduction of abdominal viscera with a spring-loaded silo. Visceral coverage in each case was achieved with 0.42-mm-thickness Surgisis ES (Cook Surgical, Bloomington, Ind) that was sewn to the fascial edges. Negative pressure wound therapy was then initiated at 75 mm Hg over the exposed SIS using vacuum-assisted closure.

RESULTS

In each case, granulation tissue developed quickly and was followed by complete epithelialization. Two patients subsequently developed umbilical hernias.

CONCLUSION

We have successfully used SIS augmented by NPWT in the management of 3 infants with complicated gastroschisis. In the rare situation in which fascial closure cannot be achieved, the combination of SIS and NPWT can provide a safe and effective means of abdominal wall closure.

Antibacterial activity within degradation products of biological scaffolds composed of extracellular matrix

Biological scaffolds composed of extracellular matrix (ECM) have been shown to be resistant to deliberate bacterial contamination in preclinical in vivo studies. The present study evaluated the degradation products resulting from the acid digestion of ECM scaffolds for antibacterial effects against clinical strains of Staphylococcus aureus and Escherichia coli. The ECM scaffolds were derived from porcine urinary bladder (UBM-ECM) and liver (L-ECM). These biological scaffolds were digested with acid at high temperatures, fractionated using ammonium sulfate precipitation, and tested for antibacterial activity in a standardized in vitro assay. Degradation products from both UBM-ECM and L-ECM demonstrated antibacterial activity against both S. aureus and E. coli. Specific ammonium sulfate fractions that showed antimicrobial activity varied for the 2 different ECM scaffold types. The results of this study suggest that several different low-molecular-weight peptides with antibacterial activity exist within ECM and that these peptides may help explain the resistance to bacterial infection provided by such biological scaffolds.

Defect repair in rat mandible with hydroxyapatite cement compared to small intestine submucosa

Aim: The aim of this study was to evaluate the bone formation in surgically created defects of rabbit mandibles by synthetic hydroxyapatite of calcium compared to small Intestine Submucosa. Material and Method: 24 mices lineage Wisthar-Furth were used. A bony defect of 0,75 cm x 1,5 cm in mandibular ramus was accomplished in all animals. The hydroxyapatite implants were placed on the left hemimandiblein groupI, small Intestine submucosa in group II, and the right served as control. The euthanasia was accomplished in the 40° postoperative day, it was proceeded the macroscopic and histological analysis. Results: medium length in millimeters of the hemimandibless in the hydroxyapatite group was of 3,75, in the small intestine submucosa 3,03 and the control group was of 2,63 (p: 0,022). Histomorphometry study reaveled new bone grown in 76,64% of the total area in hydroxyapatite group (p: 0,022). In Small Intestinal submucosa group new bone grown in 63,64% do total (p: 0,0022). Discussion: satisfactory bone integration was observed of the synthetic hydroxyapatite in that experimental model. Small intestinal submucosa cause osteoinduction Conclusion: using hydroxyapatite of calcium resulted in formation of significantly larger volume frations of new bone when compared to small intestinal submucosa group.

The use of extracellular matrix as an inductive scaffold for the partial replacement of functional myocardium

Regenerative medicine approaches for the treatment of damaged or missing myocardial tissue include cell-based therapies, scaffold-based therapies, and/or the use of specific growth factors and cytokines. The present study evaluated the ability of extracellular matrix (ECM) derived from porcine urinary bladder to serve as an inductive scaffold for myocardial repair. ECM scaffolds have been shown to support constructive remodeling of other tissue types including the lower urinary tract, the dermis, the esophagus, and dura mater by mechanisms that include the recruitment of bone marrow-derived progenitor cells, angiogenesis, and the generation of bioactive molecules that result from degradation of the ECM. ECM derived from the urinary bladder matrix, identified as UBM, was configured as a single layer sheet and used as a biologic scaffold for a surgically created 2 cm2 full-thickness defect in the right ventricular free wall. Sixteen dogs were divided into two equal groups of eight each. The defect in one group was repaired with a UBM scaffold and the defect in the second group was repaired with a Dacron patch. Each group was divided into two equal subgroups (n = 4), one of which was sacrificed 15 min after surgical repair and the other of which was sacrificed after 8 weeks. Global right ventricular contractility was similar in all four subgroups groups at the time of sacrifice. However, 8 weeks after implantation the UBM-treated defect area showed significantly greater (p < 0.05) regional systolic contraction compared to the myocardial defects repaired with by Dacron (3.3 +/- 1.3% vs. -1.8 +/- 1.1%; respectively). Unlike the Dacron-repaired region, the UBM-repaired region showed an increase in systolic contraction over the 8-week implantation period (-4.2 +/- 1.7% at the time of implantation vs. 3.3 +/- 1.3% at 8 weeks). Histological analysis showed the expected fibrotic reaction surrounding the embedded Dacron material with no evidence for myocardial regeneration. Histologic examination of the UBM scaffold site showed cardiomyocytes accounting for approximately 30% of the remodeled tissue. The cardiomyocytes were arranged in an apparently randomly dispersed pattern throughout the entire tissue specimen and stained positive for alpha- sarcomeric actinin and Connexin 43. The thickness of the UBM graft site increased greatly from the time of implantation to the 8-week sacrifice time point when it was approximately the thickness of the normal right ventricular wall. Histologic examination suggested complete degradation of the originally implanted ECM scaffold and replacement by host tissues. We conclude that UBM facilitates a constructive remodeling of myocardial tissue when used as replacement scaffold for excisional defects.

Small Intestinal Submucosa Improves Islet Survival and Function in Vitro Culture

INTRODUCTION

Most centers maintain isolated human islet preparations in tissue culture to improve the safety as well as the practicality of islet transplantation. However, maintaining viability and recovery of islets remains a challenge. Extracellular matrix (ECM) is one of the most important components of the islet microenvironment. Reconstruction of the cell-matrix relationship seems to be necessary to sustain the structure and function of differentiated islets. Small intestinal submucosa (SIS), a natural ECM, is well known to promote wound healing, tissue remodeling, and cell growth. The purpose of this study was to evaluate recovery and function of isolated rat pancreatic islets during in vitro culture with SIS.

METHODS

Pancreatic islets isolated from Wistar rats following intraductal collagenase distension, mechanical dissociation, and EuroFicoll purification were cultured in plates coated with multilayer SIS (SIS-treated group) or without (standard cultured group) for 7 or 14 days in an islet culture media of RPMI 1640 (Gibco). The islets from both experimental groups were stained and counted with dithizone. Islet recovery following culture was determined by the ratio of counts after culture to the yield of islets immediately following islet isolation. The viability of the islets was assessed by a glucose challenge test with low glucose (2.7 mmol/L), high glucose (16.7 mmol/L), and high glucose solution supplemented with 50 micromol/L 3-isobutyl-1-methylxanthine solution. The apoptosis of islet cells was measured by relative quantification of histone-complexed DNA fragments by using enzyme-linked immunosorbent assay.

RESULTS

After 7 or 14 days of in vitro tissue culture, the recovery in SIS-treated islets group was about double of that cultured in the plates without SIS coating. In the SIS-treated group, there was no significant difference between the short- and the long-term periods of culture (95.8%+/-1.0% vs 90.8%+/-1.5%, P>.05). Following incubation with high glucose (16.7 mmol/L) solution, the insulin secretion in the SIS-treated group showed a greater increase than the control group after 14 days of culture (20.7+/-1.1 mU/L vs 11.8+/-1.1 mU/L, P<.05). When islets were placed in the high glucose solution containing IBMX, the stimulated insulin secretion was more increased in the SIS-treated than in the control group despite the duration of the culture. The calculated stimulation index of SIS-treated group was about two to three times greater than the control group. In addition, the stimulation index of the SIS-treated group remained constant regardless of short-term versus long-term culture (9.5+/-0.2 vs 10.2+/-1.2, P>.05). Much less apoptosis of islet cells occurred in the SIS-treated than in the control group.

CONCLUSION

Coculture of isolated rat islets with native sheetlike small intestinal submucosa seemed to build an ECM for islets providing possible biotrophic and growth factors that promote the recovery and subsequent function of islets.