Porcine small intestinal submucosa as a dural substitute

Trends in CSF Leakage Associated with Duraplasty in Infratentorial Procedures over the Last 20 Years: A Systematic Review

Cerebrospinal fluid (CSF) leakage is a common postoperative complication of neurosurgical procedures, with iatrogenic causes accounting for 16% of CSF leakages. This complication increases healthcare costs and patient morbidity. The focus of this review is to analyze the rates of CSF leakage of some of the most commonly used xenogeneic and synthetic dural substitutes following surgeries in the infratentorial region of the brain where surgical repair can be most challenging. A systematic literature search was conducted using studies detailing duraplasty procedures performed with nonautologous grafts in the infratentorial region in PubMed. Studies were identified using the following search terms: "posterior fossa" or "infratentorial" were used in combination with "CSF leak," "CSF leakage," "cerebrospinal fluid leakage," "duraplasty" or "dura graft." The outcome of interest was a measure of the prevalence of CSF leakage rates following posterior fossa neurosurgery. Studies that contributed data to this review were published between 2006 and 2021. The dural graft materials utilized included: bovine collagen, acellular dermis, equine collagen, bovine pericardium, collagen matrix, and expanded polytetrafluoroethylene (ePTFE). The number of subjects in studies on each of these grafts ranged from 6 to 225. CSF leak rates ranged from 0% to 25% with the predominance of studies reporting between 3% and 15%. The studies that utilize bovine collagen, equine collagen, and acellular dermis reported higher CSF leakage rates; whereas studies that utilized ePTFE, bovine pericardium, and collagen matrix reported lower CSF leakage rates. Due to the heterogeneity of methodologies used across these studies, it is difficult to draw a direct correlation between the dural patch products used and CSF leaks. Larger prospective controlled studies that evaluate various products in a head-to-head fashion, using the same methods and animal models, are needed to conclude the relative efficacy of these dural patch products.

A biomimetic hierarchical small intestinal submucosa-chitosan sponge/chitosan hydrogel scaffold with a micro/nano structure for dural repair

The dura mater is an essential barrier to protect the brain tissue and the dural defects caused by accidents can lead to serious complications. Various materials have been applied to dural repair, but it remains a challenge to perfectly match the structure and properties of the natural dura mater. Small intestinal submucosa has been developed for dural repair because of its excellent biocompatibility and biological activity, but its application is tremendously limited by the rapid degradation rate. Chitosan has also been broadly investigated in tissue repair, but the traditional chitosan hydrogels exhibit poor mechanical properties. A nanofiber chitosan hydrogel can be constructed based on an alkaline solvent, which is equipped with surprisingly high strength. Therefore, based on the bilayer structure of the natural dura mater, a biomimetic hierarchical small intestinal submucosa-chitosan sponge/chitosan hydrogel scaffold with a micro/nano structure was fabricated, which possessed a microporous structure in the upper sponge and a nanofiber structure in the lower hydrogel. The degradation rate was remarkably reduced compared with that of the small intestinal submucosa in the enzymatic degradation experiment in vitro. Meanwhile, the chitosan nanofibers brought high mechanical strength to the bilayer scaffold. Moreover, the hierarchical micro/nano structure and the active factors in the small intestinal submucosa have a fantastic effect on promoting the proliferation of fibroblasts and vascular endothelial cells. The bilayer scaffold showed good histocompatibility in the experiment of in vitro subcutaneous implantation in rats. Thus, the biomimetic hierarchical small intestinal submucosa-chitosan sponge/chitosan hydrogel scaffold with micro/nano structure simulates the structure of the natural dura mater and possesses properties with excellent performance, which has high practical value for dural repair.

Tissue-Specific Decellularization Methods: Rationale and Strategies to Achieve Regenerative Compounds

The extracellular matrix (ECM) is a complex network with multiple functions, including specific functions during tissue regeneration. Precisely, the properties of the ECM have been thoroughly used in tissue engineering and regenerative medicine research, aiming to restore the function of damaged or dysfunctional tissues. Tissue decellularization is gaining momentum as a technique to obtain potentially implantable decellularized extracellular matrix (dECM) with well-preserved key components. Interestingly, the tissue-specific dECM is becoming a feasible option to carry out regenerative medicine research, with multiple advantages compared to other approaches. This review provides an overview of the most common methods used to obtain the dECM and summarizes the strategies adopted to decellularize specific tissues, aiming to provide a helpful guide for future research development.

Human Testis Extracellular Matrix Enhances Human Spermatogonial Stem Cell Survival In Vitro

IMPACT STATEMENT

This study developed and characterized human testis extracellular matrix (htECM) and porcine testis ECM (ptECM) for testing in human spermatogonial stem cell (hSSC) culture. Results confirmed the hypothesis that ECM from the homologous species (human) and homologous tissue (testis) is optimal for maintaining hSSCs. We describe a simplified feeder-free, serum-free condition for future iterative testing to achieve the long-term goal of stable hSSC cultures. To facilitate analysis and understand the fate of hSSCs in culture, we describe a multiparameter, high-throughput, quantitative flow cytometry approach to rapidly count undifferentiated spermatogonia, differentiated spermatogonia, apoptotic spermatogonia, and proliferative spermatogonia in hSSC cultures.

Cranioplasty Using Titanium Mesh After Skull Tumor Resection in Five Dogs

OBJECTIVE

To describe the clinical details, surgery, postoperative imaging, and short to mid-term outcome after cranioplasty with titanium mesh in dogs with large skull tumors.

STUDY DESIGN

Case series.

ANIMALS

Client-owned dogs with skull tumors (n=5).

METHODS

All tumors were removed via craniectomy and a sheet of titanium mesh was contoured to reconstruct the calvarial defect and sutured to surrounding musculature.

RESULTS

Four dogs had multilobular tumors of bone and 1 dog had a soft tissue sarcoma invading the cranial vault. Neurologic examination was unchanged or improved postoperative, a good cosmetic appearance was achieved, and no complications were noted at 2 weeks postoperative. Late postoperative computed tomography (CT) in 2 dogs and magnetic resonance (MR) imaging in 1 dog confirmed the presence of the titanium mesh without migration. There was no interference of the mesh with image interpretation and definitive radiation therapy was pursued in 1 dog without complication. Late follow-up reported 2 dogs euthanatized; at 44 weeks postoperative due to tumor re-growth; at 12 weeks postoperative for hemoabdomen, respectively. One dog drowned at 40 weeks postoperative, 1 dog was lost to follow-up, and 1 dog is alive at 83 weeks postoperative free of clinical signs.

CONCLUSIONS

Titanium mesh is suitable for cranioplasty based on its strength, biocompatibility, and excellent handling characteristics. It does not interfere with acquisition or interpretation of CT or MR images, thereby allowing postoperative imaging for ongoing assessment.

Reconstructing spinal dura-like tissue using electrospun poly(lactide-co-glycolide) membranes and dermal fibroblasts to seamlessly repair spinal dural defects in goats

Many neuro- and spinal surgeries involving access to the underlying nervous tissue will cause defect of spinal dural mater, further resulting in cerebrospinal fluid leakage. The current work was thus aimed to develop a package which included two layers of novel electrospun membranes, dermal fibroblasts and mussel adhesive protein for repairing spinal dural defect. The inner layer is electrospun fibrous poly(lactide-co-glycolide) membrane with oriented microstructure (O-poly(lactide-co-glycolide)), which was used as a substrate to anchor dermal fibroblasts as seed cells to reconstitute dura-like tissue via tissue engineering technique. The outer layer is chitosan-coated electrospun nonwoven poly(lactide-co-glycolide) membrane (poly(lactide-co-glycolide)-chitosan). During surgery, the inner reconstituted tissue layer was first used to directly cover dura defects, while the outer layer was placed onwards with its marginal area tightly immobilized to the surrounding normal spinal dura aided by mussel adhesive protein. Efficacy of the current design was verified in goats with spinal dural defects (0.6 cm × 0.5 cm) in lumbar. It was shown that seamless and quick sealing of the defect area with the implants was realized by mussel adhesive protein. Guided tissue growth and regeneration in the defects of goats were observed when they were repaired by the current package. Effective cerebrospinal fluid containment and anti-adhesion of the regenerated tissue to the surrounding tissue could be achieved in the current animal model. Hence, it could be ascertained that the current package could be a favorite choice for surgeries involving spinal dural defects.

Native extracellular matrix: a new scaffolding platform for repair of damaged muscle

Effective clinical treatments for volumetric muscle loss resulting from traumatic injury or resection of a large amount of muscle mass are not available to date. Tissue engineering may represent an alternative treatment approach. Decellularization of tissues and whole organs is a recently introduced platform technology for creating scaffolding materials for tissue engineering and regenerative medicine. The muscle stem cell niche is composed of a three-dimensional architecture of fibrous proteins, proteoglycans, and glycosaminoglycans, synthesized by the resident cells that form an intricate extracellular matrix (ECM) network in equilibrium with the surrounding cells and growth factors. A consistent body of evidence indicates that ECM proteins regulate stem cell differentiation and renewal and are highly relevant to tissue engineering applications. The ECM also provides a supportive medium for blood or lymphatic vessels and for nerves. Thus, the ECM is the nature's ideal biological scaffold material. ECM-based bioscaffolds can be recellularized to create potentially functional constructs as a regenerative medicine strategy for organ replacement or tissue repopulation. This article reviews current strategies for the repair of damaged muscle using bioscaffolds obtained from animal ECM by decellularization of small intestinal submucosa (SIS), urinary bladder mucosa (UB), and skeletal muscle, and proposes some innovative approaches for the application of such strategies in the clinical setting.

Biologic scaffold for CNS repair

Injury to the CNS typically results in significant morbidity and endogenous repair mechanisms are limited in their ability to restore fully functional CNS tissue. Biologic scaffolds composed of individual purified components have been shown to facilitate functional tissue reconstruction following CNS injury. Extracellular matrix scaffolds derived from mammalian tissues retain a number of bioactive molecules and their ability for CNS repair has recently been recognized. In addition, novel biomaterials for dural mater repairs are of clinical interest as the dura provides barrier function and maintains homeostasis to CNS. The present article describes the application of regenerative medicine principles to the CNS tissues and dural mater repair. While many approaches have been exploring the use of cells and/or therapeutic molecules, the strategies described herein focus upon the use of extracellular matrix scaffolds derived from mammalian tissues that are free of cells and exogenous factors.

Short-Term Outcomes of KeraSys Patch Graft for Glaucoma Drainage Devices: A Case Series

Purpose. Tube-related exposure is a known complication of glaucoma drainage device (GDD) surgery. Our objective is to report the early (approximately 1 year) tube exposure rate of implants covered with a keraSys (IOP Inc., Costa Mesa, CA, USA) tissue reinforcement graft. Patients and Methods. A retrospective, noncomparative, consecutive case series of 42 eyes with GDD implantation with keraSys patch grafts was performed. Main outcome measurements included patch-related complications: patch exposure, tube exposure, wound dehiscence, and patch migration. Results. Forty-two eyes were followed for an average of 15.24 ± 10.44 months (range 1.0–32.3 months). Four (10%) eyes experienced patch-related complications: two with exposure 8 months postoperatively, one with exposure 13 months postoperatively, and one with exposure 4 weeks postoperatively. Conclusion. The effectiveness of the keraSys patch graft is limited by the higher than expected early exposure rate found in this case series. These results should be confirmed in other studies.

Non-invasive imaging of transplanted human neural stem cells and ECM scaffold remodeling in the stroke-damaged rat brain by (19)F- and diffusion-MRI

Transplantation of human neural stem cells (hNSCs) is emerging as a viable treatment for stroke related brain injury. However, intraparenchymal grafts do not regenerate lost tissue, but rather integrate into the host parenchyma without significantly affecting the lesion cavity. Providing a structural support for the delivered cells appears important for cell based therapeutic approaches. The non-invasive monitoring of therapeutic methods would provide valuable information regarding therapeutic strategies but remains a challenge. Labeling transplanted cells with metal-based (1)H-magnetic resonance imaging (MRI) contrast agents affects the visualization of the lesion cavity. Herein, we demonstrate that a (19)F-MRI contrast agent can adequately monitor the distribution of transplanted cells, whilst allowing an evaluation of the lesion cavity and the formation of new tissue on (1)H-MRI scans. Twenty percent of cells labeled with the (19)F agent were of host origin, potentially reflecting the re-uptake of label from dead transplanted cells. Both T(2)- and diffusion-weighted MRI scans indicated that transplantation of hNSCs suspended in a gel form of a xenogeneic extracellular matrix (ECM) bioscaffold resulted in uniformly distributed cells throughout the lesion cavity. However, diffusion MRI indicated that the injected materials did not yet establish diffusion barriers (i.e. cellular network, fiber tracts) normally found within striatal tissue. The ECM bioscaffold therefore provides an important support to hNSCs for the creation of de novo tissue and multi-nuclei MRI represents an adept method for the visualization of some aspects of this process. However, significant developments of both the transplantation paradigm, as well as regenerative imaging, are required to successfully create new tissue in the lesion cavity and to monitor this process non-invasively.

Dura mater regeneration with a novel synthetic, bilayered nanofibrous dural substitute: an experimental study

Aim: To create a synthetic nanofibrous dural substitute that overcomes the limitations of current devices by enhancing dural healing via biomimetic nanoscale architecture and supporting both onlaid and sutured implantation. Materials & methods: A custom electrospinning process was used to create a bilayer dural substitute having aligned nanofibers on one side and random nanofibers on the other. Nanoscale architecture was verified using microscopy and macroscale mechanical properties were investigated using tensile testing. Biological response to this device was investigated both in vitro and in a canine duraplasty model. Results & conclusion: Bilayer nanofiber alignment yields a graft having anisotropic mechanical properties with significantly higher strength and suturability than a commercially available collagen matrix. When implanted, the nanofibrous graft prevents leaks and brain tissue adhesions, and encourages dura mater regrowth, performing comparably to the collagen matrix. Both in vitro fibroblast orientation and in vivo dural healing are enhanced by the aligned nanofibers.

Radially aligned, electrospun nanofibers as dural substitutes for wound closure and tissue regeneration applications

This paper reports the fabrication of scaffolds consisting of radially aligned poly(ε-caprolactone) nanofibers by utilizing a collector composed of a central point electrode and a peripheral ring electrode. This novel class of scaffolds was able to present nanoscale topographic cues to cultured cells, directing and enhancing their migration from the periphery to the center. We also established that such scaffolds could induce faster cellular migration and population than nonwoven mats consisting of random nanofibers. Dural fibroblast cells cultured on these two types of scaffolds were found to express type I collagen, the main extracellular matrix component in dural mater. The type I collagen exhibited a high degree of organization on the scaffolds of radially aligned fibers and a haphazard distribution on the scaffolds of random fibers. Taken together, the scaffolds based on radially aligned, electrospun nanofibers show great potential as artificial dural substitutes and may be particularly useful as biomedical patches or grafts to induce wound closure and/or tissue regeneration.

Adrenal extracellular matrix scaffolds support adrenocortical cell proliferation and function in vitro

Transplantation of functional adrenal cortex cells could reduce morbidity and increase the quality of life of patients with adrenal insufficiency. Our aim was to determine whether adrenal extracellular matrix (ECM) scaffolds promote adrenocortical cell endocrine function and proliferation in vitro. We seeded decellularized porcine adrenal ECM with primary human fetal adrenocortical (HFA) cells. Adrenocortical function was quantified by cortisol secretion of HFA-ECM constructs after stimulation with adrenocorticotropic hormone. Proliferation was assessed by adenosine triphosphate assay. HFA-ECM construct morphology was evaluated by immunofluorescence microscopy and scanning electron microscopy. Adrenal HFA-ECM constructs coated with laminin were compared to uncoated constructs. Laminin coating did not significantly affect HFA morphology, proliferation, or function. We demonstrated HFA cell attachment to adrenal ECM scaffolds. Cortisol production and HFA cell proliferation were significantly increased in HFA-ECM constructs compared to controls (p < 0.05), and cortisol secretion rate per cell is comparable to that of human adult and fetal explants. We conclude that adrenal ECM supports endocrine function and proliferation of adrenocortical cells in vitro. Adrenal ECM scaffolds may form the basis for biocompatible tissue-engineered adrenal replacements.

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.

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.

Successful incorporation of tissue-engineered porcine small-intestinal submucosa as substitute flexor tendon graft is mediated by elevated TGF-beta1 expression in the rabbit

PURPOSE

Ideal tendon repair materials combine minimal donor-site morbidity and ready availability with excellent healing and postoperative function. Bioengineered porcine small-intestinal submucosa (SIS) was compared with tendon autografts as a potential human flexor tendon graft substitute.

METHODS

Rabbit zone II flexor digitorum profundus segments were excised in 40 rabbits. Randomized tendon repair consisted of either interposition reversed autograft or SIS, passed beneath the A2 and A4 pulleys. Forepaws were statically splinted for 3 weeks followed by unrestricted motion. Animals were killed at 7, 14, 28, and 56 days. Specimens were analyzed for hydroxyproline content (absorption spectroscopy) and tensile strength. Hematoxylin-eosin and Movat-stained sections of the central graft and distal repair site were semiquantitatively scored for total cellularity, inflammatory cell content, foreign-body reaction, vascularity, mature collagen content, and new collagen deposition. Transforming growth factor-beta (TGF-beta1) and TGF-beta1 receptor immunostaining was performed.

RESULTS

At week 1, SIS hydroxyproline content was significantly reduced compared with autograft hydroxyproline content. However, week 2 SIS hydroxyproline content increased to equivalent values. Collagen deposition was evident in SIS by week 1 but negligible in autograft. More rapid total and inflammatory cell increases occurred in SIS by 4 weeks. A stronger early inflammatory reaction also occurred. More rapid SIS neovascularization occurred despite a greater foreign-body reaction. Small-intestinal submucosa vascularity was markedly greater at weeks 1 and 2 and equivalent thereafter. At week 4, SIS intrinsic tensile strength (suture removed) exceeded that of both autograft and suture material. Preoperative TGF-beta1 immunostaining in SIS was less than that of autograft but greater during weeks 2 and 4.

CONCLUSIONS

Earlier neovascularization, increased TGF-beta1 levels, and increased collagen deposition, along with greater intrinsic repair strength relative to both autograft and suture strength at week 4, make SIS a promising flexor tendon graft substitute. Future studies examining tendon excursion are planned.

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.

Safety and efficacy of the porcine small intestinal submucosa dural substitute: results of a prospective multicenter study and literature review

Object

Dural substitutes are often needed after neurosurgical procedures to expand or replace dura mater resected during surgery. A new dural repair material derived from porcine small intestinal submucosa (SIS) was evaluated in a prospective multicenter clinical study.

Methods

Between 2000 and 2003, 59 patients at five different institutions underwent dural reconstruction with the SIS dural substitute, with a minimum follow up of 6 months. The primary goals of the study were to assess the efficacy and safety of the SIS dural substitute according to the rate of cerebrospinal fluid (CSF) leakage, infection, and meningitis.

Chiari malformation Type I decompression (32 patients) and tumor resection (18 patients) were the most common procedures performed, with 81% of SIS grafts implanted in the posterior fossa or spine. There was one case of a CSF leak (1.7%), two cases of wound infection (3.4%), and no cases of bacterial meningitis (0%) in the 58 patients available for follow up. In both cases of wound infection, the SIS graft acted as a barrier to infection and was not removed. Intraoperatively, a watertight seal was achieved in all 59 cases. On follow-up imaging available in 27 patients there was no evidence of any adverse reaction to the graft or of cerebral inflammation.

Conclusions

The SIS dural substitute demonstrated substantial efficacy in these patients after a mean follow up of 7.3 ± 2.2 months. Rates of infection, CSF leakage, and meningitis were comparable to those reported for other dural substitute materials. A lack of adverse reactions to the graft, favorable safety profile, and clinical efficacy all point to the utility of this material as an alternative for dural repair.

Surgical repair of deep melting ulcers with porcine small intestinal submucosa (SIS) graft in dogs and cats

PURPOSE

To evaluate the efficacy of using a porcine small intestinal submucosa (SIS) graft for the surgical repair of deep melting ulcers in dogs and cats.

METHODS

Two cats and five dogs presented with deep and large melting ulcers of the cornea. In each case, the necrotic and collagenolytic tissue of the cornea was removed by keratectomy. A SIS graft, 1 mm greater than the corneal defect, was rehydrated in sterile saline and sutured to the edges of the ulcer with a simple interrupted pattern of 9/0 polyglactin 910. A nictitating membrane flap was utilized in two cats and four dogs for 2 weeks. All cases were treated postoperatively with topical and systemic antibiotics, a systemic anti-inflammatory drug and topical atropine. All animals were re-evaluated 15 days, 4 weeks, 35-45 days, 2-3 months and 6 months postsurgery.

RESULTS

At 15 days postsurgery, a superficial intense corneal neovascularization surrounded the SIS graft. No ocular discomfort was present and fluorescein staining was negative in all cases. At 4 weeks the SIS graft was thick and opaque in all cases, although in one cat the SIS graft had partially detached. Between 35 and 45 days, SIS graft integration was evident in all eyes, and corneal neovascularization had decreased progressively. All eyes healed without complications and retained corneal transparency. This occurred even in the presence of corneal perforation in two cases: one prior to and one during surgery.

CONCLUSION

Results of our study suggest the SIS graft may be an effective alternative surgical treatment to the traditional conjunctival grafts commonly used to repair melting ulcers in dogs and cats. The advantages of using a SIS graft include good corneal transparency, preservation of corneal integrity and maintenance of vision.

Investigations of urothelial cells seeded on commercially available small intestine submucosa

OBJECTIVES

To examine adherence and viability of human urothelial cells seeded on commercially available small intestine submucosa (SIS) specimens under serum-free conditions.

MATERIALS AND METHODS

Before seeding, SIS was either washed with incubation medium or coated with collagen A, fibronectin, or pronectin. A possible influence of SIS itself on the viability of urothelial cells was analysed with conditioned cell culture medium obtained by incubation of SIS for 24hours. In addition, untreated SIS and a setting without SIS were used as controls. Viability of urothelial cells was analysed with the WST-1 assay until day 9. Histology of seeded and unseeded SIS specimens was investigated after Papanicolaou staining. To demonstrate urothelial cell adherence on SIS, immunohistology was performed with a mixture of monoclonal AE1 and AE3 anticytokeratin antibodies.

RESULTS

Urothelial cells seeded on SIS revealed no measurable cell viability. SIS-conditioned cell culture medium was cytotoxic for urothelial cells after 24 hours. Histology only demonstrated cell nuclei and no cytoplasm both in seeded and unseeded SIS specimens, thus indicating porcine DNA. Expression of the cell type-specific marker proteins AE1/AE3 could not be demonstrated.

CONCLUSION

Since the commercially available SIS specimens used contained porcine DNA residues and demonstrated cytotoxic effects on urothelial cells, SIS is not suitable for in vitro construction of urothelial cell-matrix implants.

Porcine small intestine submucosa augmentation of surgical repair of chronic two-tendon rotator cuff tears. A randomized, controlled trial

BACKGROUND

Evidence to justify the use of porcine small intestine submucosa to augment repairs of large and massive rotator cuff tears is based on favorable results found in studies of Achilles tendon and infraspinatus tendon repairs in canines. The purpose of this study was to determine the effectiveness of a small intestine submucosal patch to augment the repair of chronic two-tendon rotator cuff tears in humans.

METHODS

Thirty shoulders with a chronic two-tendon rotator cuff tear that was completely repairable with open surgery were randomized to be treated with either augmentation with porcine small intestine mucosa or no augmentation. All patients completed a PENN shoulder-score questionnaire preoperatively and at the time of the latest follow-up (at an average of fourteen months). Magnetic resonance imaging showed that nine shoulders had a large tear and twenty-one had a massive tear. All patients underwent a magnetic resonance imaging scan with intra-articular gadolinium one year after the repair to assess the status of the rotator cuff.

RESULTS

The rotator cuff healed in four of the fifteen shoulders in the augmentation group compared with nine of the fifteen in the control group (p = 0.11). The median postoperative PENN total score was 83 points in the augmentation group compared with 91 points in the control group (p = 0.07). Healing of the defects in both groups demonstrated a strong correlation with the patients' clinical scores. The median postoperative PENN total score was 96 points in the group with a healed repair and 81 points in the group with a failed repair (p = 0.007). The percentage change between the preoperative and postoperative patient satisfaction scores was 400% in the group with a healed repair, and 50% in the group with a failed repair (p = 0.04).

CONCLUSIONS

Augmentation of the surgical repair of large and massive chronic rotator cuff tears with porcine small intestine submucosa did not improve the rate of tendon-healing or the clinical outcome scores. On the basis of these data, we do not recommend using porcine small intestine submucosa to augment repairs of massive chronic rotator cuff tears done with the surgical and postoperative procedures described in this study.

Reconstruction of large rotator cuff tendon defects with porcine small intestinal submucosa in an animal model

Large rotator cuff tears represent a challenging problem. The purpose of our study was to evaluate the small intestinal submucosa (SIS) extracellular matrix in reconstruction of such defects in an animal model. Forty rats were equally divided into an SIS group (reconstruction of a large supraspinatus tendon defect by use of the SIS) and a defect group (no repair). The operative and contralateral normal shoulders underwent histologic evaluation and biomechanical testing at 6 and 16 weeks. Neovascularization and fibroblastic ingrowth were present in SIS-regenerated tendons, which had an ultimate force to failure that was 78% of normal at 16 weeks. This was higher than in the defect group, which demonstrated an ultimate force to failure that was 34% of normal (P = .008). The ultimate force to failure of the SIS-regenerated tendons approached that of the normal tendon at 16 weeks. The SIS extracellular matrix served as a scaffold promoting host tissue ingrowth and appears promising in the management of large rotator cuff defects in a rat model. However, human beings sustain tears at the bone-tendon interface and demonstrate decreased healing potential relative to rats. Therefore, the findings of this preliminary study should not be extrapolated to human beings without further investigation.

Porcine small intestine submucosa (SIS) is not an acellular collagenous matrix and contains porcine DNA: possible implications in human implantation

Porcine small intestinal submucosa (SIS) has been recommended as a cell-free, biocompatible biomaterial for the repair of rotator cuff tendon tear. However, we have observed noninfectious edema and severe pain in patients who have undergone SIS implantation for tendon repair. The aim of this study was to conduct an independent assessment of the safety and efficacy of Restore SIS membrane. The Restore orthobiologic implant was examined by histology and the nested PCR technique using porcine immunoreceptor DAP12 gene to examine if SIS membrane contained porcine cells or DNA, respectively. The material was also implanted into mice and rabbits for the evaluation of biological reaction and inflammatory response. Restore SIS was found to contain multiple layers of porcine cells. Chloroacetate esterase staining showed that some of these cells were mast cells. Nested PCR of the DAP12 gene demonstrated that Restore SIS contained porcine DNA material. Subcutaneous implantation of Restore SIS membrane in mice, and in rabbits for rotator cuff tendon repair, showed that the membrane caused an inflammatory reaction characterized by massive lymphocyte infiltration. In conclusion, Restore SIS is not an acellular collagenous matrix, and contains porcine DNA. Our results contradict the current view that Restore SIS is a cell-free biomaterial, and that no inflammatory response is elicited by its implantation. We suggest that further studies should be conducted to evaluate the clinical safety and efficacy of SIS implant biomaterials.

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

OBJECTIVE

As a vascular conduit, expanded polytetrafluoroethylene (ePTFE) is susceptible to graft infection with Gram-positive organisms. Biomaterials, such as porcine small-intestinal submucosa (SIS), have been successfully used clinically as tissue substitutes outside the vascular arena.

SUMMARY BACKGROUND DATA

In the present study, we compared a small-diameter conduit of SIS to ePTFE in the presence of Gram-positive contamination to evaluate infection resistance, incorporation and remodeling, morphometry, graft patency, and neointimal hyperplasia (NH) development.

METHODS

Adult male mongrel pigs were randomized to receive either SIS or ePTFE (3-cm length, 6-mm diameter) and further randomized to 1 of 3 groups: Control (no graft inoculation), Staphylococcus aureus, or mucin-producing S epidermidis (each graft inoculation with 10 colonies/mL). Pressure measurements were obtained proximal and distal to the graft to create the iliac/aorta pressure ratio. Morphometric analysis of the neointima and histopathologic examinations was performed. Other outcomes included weekly WBC counts, graft incorporation, and quantitative culture of explanted grafts.

RESULTS

Eighteen animals were randomized. All grafts were patent throughout the 6-week study period. Infected SIS grafts had less NH and little change in their iliac/aorta indices compared with infected ePTFE grafts. Quantitative cultures at euthanasia demonstrated no growth in either SIS group compared with 1.7 x 10(4) colonies for ePTFE S aureus and 6 x 10(2) for ePTFE S epi (each P < 0.001). All SIS grafts were incorporated. Histology demonstrated remodeling into host artery with smooth muscle and capillary ingrowth in all SIS groups. Scanning electron micrography illustrated smooth and complete endothelialization of all SIS grafts.

CONCLUSIONS

Compared with ePTFE, SIS induces host tissue remodeling, exhibits a decreased neointimal response to infection, and is resistant to bacterial colonization. SIS may provide a superior alternative to ePTFE as a vascular conduit for peripheral vascular surgery.

Early inflammatory reaction after rotator cuff repair with a porcine small intestine submucosal implant: a report of 4 cases

BACKGROUND

Porcine small intestine submucosal grafts have been successful in enhancing soft tissue repair, as demonstrated by animal studies. Currently, there are no reports of the use of such implants in human rotator cuff repair.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Over a 6-month period, 25 patients underwent rotator cuff repair by one surgeon using the Restore Orthobiologic Implant to augment the repaired tendon or fill a defect.

RESULTS

Four of 25 patients experienced an overt inflammatory reaction at a mean of 13 days postoperatively. All patients underwent open irrigation and debridement of the rotator cuff and porcine small intestine submucosal implant.

CONCLUSION

Porcine small intestine submucosal implants should be used in rotator cuff surgery with the awareness that a non-specific inflammatory reaction can occur in the early postoperative period. This inflammatory reaction may cause breakdown of the repair. Further studies are needed to further characterize the reaction and determine which patients are susceptible.

Assessing porcine liver-derived biomatrix for hepatic tissue engineering

Acellular, biologically derived matrices such as small intestinal submucosa have been extensively utilized to induce tissue regeneration and remodeling of connective tissue, vascular grafts, and urinary bladder; however, decellularized scaffolds have not been explored for their potential utility in hepatic tissue engineering. In the case of both extracorporeal hepatocyte-based devices and implantable hepatocyte-scaffold tissue-engineered constructs, maintenance of hepatocellular function is of prime importance. In this study, we specifically explored decellularized, porcine, liver-derived biomatrix (LBM) as a bioresorbable scaffold for primary hepatocytes. Primary rat hepatocytes were cultured on LBM and compared with well-characterized hepatocyte culture models--double-gel cultures that promote maintenance of liver-specific functions for many weeks, and adsorbed collagen monolayers that lead to the rapid decline of hepatocellular function and viability. Hepatocytes were maintained for up to 45 days on LBM and liver-specific functions such as albumin synthesis, urea production, and P-450 IA1 activity were found to be significantly improved over adsorbed collagen cultures. Our data indicate that LBM may be a favorable alternative to existing scaffolds for tissue engineering in that it is bioresorbable, can be easily manipulated, and supports long-term hepatocellular functions in vitro.

Biaxial mechanical properties of muscle-derived cell seeded small intestinal submucosa for bladder wall reconstitution

Bladder wall replacement remains a challenging problem for urological surgery due to leakage, infection, stone formation, and extensive time needed for tissue regeneration. To explore the feasibility of producing a more functional biomaterial for bladder reconstitution, we incorporated muscle-derived cells (MDC) into small intestinal submucosa (SIS) scaffolds. MDC were harvested from mice hindleg muscle, transfected with a plasmid encoding for beta-galactosidase, and placed into single-layer SIS cell culture inserts. Twenty-five MDC and/or SIS specimens were incubated at 37 degrees C for either 10 or 20 days. After harvesting, mechanical properties were characterized using biaxial testing, and the areal strain under 1 MPa peak stress used to quantify tissue compliance. Histological results indicated that MDC migrated throughout the SIS after 20 days. The mean (+/-SE) areal strain of the 0 day control group was 0.182 +/- 0.027 (n=5). After 10 days incubation, the mean (+/-SE) areal strain in MDC/SIS was 0.247 +/- 0.014 (n=5) compared to 10 day control SIS 0.200 +/- 0.024 (n=6). After 20 days incubation, the mean areal strain of MDC/SIS was 0.255 +/- 0.019 (n=5) compared to control SIS 0.170 +/- 0.025 (n=5). Both 10 and 20 days seeded groups were significantly different (p=0.027) than that of incubated SIS alone, but were not different from each other. These results suggest that MDC growth was supported by SIS and that initial remodeling of the SIS ECM had occurred within the first 10 days of incubation, but may have slowed once the MDC had grown to confluence within the SIS.

Xenogeneic extracellular matrix as a scaffold for tissue reconstruction

Bioscaffolds derived from xenogeneic extracellular matrix (ECM) have been used in numerous tissue engineering applications. The safety and efficacy of such scaffolds when used for the repair and reconstruction of numerous body tissues including musculoskeletal, cardiovascular, urogenital and integumentary structures has been shown in both preclinical animal studies and in human clinical studies. More than 200,000 human patients have been implanted with xenogeneic ECM scaffolds. These ECM scaffolds are typically prepared from porcine organs such as small intestine or urinary bladder, which are subjected to decellularization and terminal sterilization without significant loss of the biologic effects of the ECM. The composition of these bioscaffolds includes the structural and functional proteins that are part of native mammalian extracellular matrix. The three-dimensional organization of these molecules distinguishes ECM scaffolds from synthetic scaffold materials and is associated with constructive tissue remodeling instead of scar tissue. The biologic response to these xenogeneic bioscaffolds, including the immune response, is discussed herein.

Low-molecular-weight peptides derived from extracellular matrix as chemoattractants for primary endothelial cells

The development of synthetic and naturally occurring scaffolds for tissue engineering applications has included strategies to promote attachment of specific cell types, control the rate of scaffold degradation, encourage angiogenesis, or otherwise modulate the host response. We have reported that bioscaffolds developed from porcine small intestinal submucosa (SIS) facilitate the constructive remodeling of tissues and recruit marrow-derived cells that persist long after the acute inflammatory stages have resolved. We have not yet determined which cells are recruited, the eventual fate of these cells, or via what mechanisms the events occur. We now have analyzed various molecular weight fractions of acid-hydrolyzed SIS by both functional and morphologic methods and have determined that fraction 4 (5 to 16 kDa) possesses chemoattractant activity for primary murine adult liver, heart, and kidney endothelial cells in vitro. Addition of fraction 4 to Matrigel plugs promoted in vivo vascularization when the plugs were implanted subcutaneously in mice. These results indicate that small-molecular-weight peptides derived from the degradation of porcine SIS are biologically active in the recruitment of murine endothelial cells in vitro and in vivo.

Porcine Small Intestine Submucosa for Soft Tissue Augmentation

OBJECTIVE

Porcine small intestine submucosa was evaluated as a material for soft tissue augmentation in the hairless guinea pig model.

MATERIALS AND METHODS

Small intestine submucosa was formed into strips and rolls and implanted into the dorsum of the hairless guinea pig. The animals were divided into three groups and the implants were evaluated grossly and microscopically for persistence, infection, and inflammation. A total of 116 implants were evaluated grossly.

RESULTS

Selected samples from the 1- and 3-month cohorts and all identifiable samples from the 5-month cohort were evaluated microscopically. Some implants were not located, likely due to migration. With one exception, the identified implants in the 5-month cohort exhibited minimal inflammation and appeared well tolerated. The eight-ply small intestine submucosa material appears well tolerated and provided increased soft tissue volume at 5 months.

CONCLUSION

Small intestine submucosa may represent an alternative to autologous and homologous materials for soft tissue augmentation.

Biaxial strength of multilaminated extracellular matrix scaffolds

Xenogeneic extracellular matrix (ECM) can be harvested and configured to function as a bioscaffold for tissue and organ reconstruction. The mechanical properties of the ECM vary depending upon the tissue from which it is harvested. Likewise, the manufacturing steps required to develop ECMs into medical grade devices will affect the surface morphology and the mechanical properties of the bioscaffold; important properties for constructive tissue remodeling. The present study compared the ball-burst strength of five different ECM scaffolds before and after treatment with peracetic acid (PAA): porcine small intestinal submucosa (SIS), porcine urinary bladder submucosa (UBS), porcine urinary bladder matrix (UBM), a composite of UBS + UBM, and canine stomach submucosa (SS). This study also compared the mechanical properties of 2- and 4-layer ECM scaffolds. Results showed 2-layer SS devices had the highest ball-burst value of all 2-layer ECM devices. Moreover, all 4-layer ECM devices had similar ball-burst strength except for 4-layer UBM devices which was the weakest. PAA-treatment decreased the ball-burst strength of SS and increased the ball-burst strength of UBS 2-layer devices. This study showed the material properties of the ECM scaffolds could be engineered to mimic those of native soft tissues (i.e. vascular, musculotendinous, etc) by varying the number of layers and modifying the disinfection/sterilization treatments used for manufacturing.

Host protection against deliberate bacterial contamination of an extracellular matrix bioscaffold versus Dacron mesh in a dog model of orthopedic soft tissue repair

The resistance of two biomaterials, one synthetic and one biologic in origin, to deliberate bacterial infection was compared in a dog model of orthopedic soft tissue reconstruction. Twenty-four adult female dogs were randomly divided into two equal groups and a 2.0-cm-round full-thickness defect was created on the lateral surface of the stifle joint, leaving only the synovium and skin intact. The defect was surgically repaired with either Dacron trade mark mesh or a porcine derived extracellular matrix (ECM) scaffold material. The repair site was inoculated with 1 x 10(8) Staphylococcus aureus at the time of surgery and the dogs were survived for 28 days. Results showed a chronic pyogranulomatous inflammatory response at the Dacron trade mark implant sites versus a constructive tissue-remodeling response without residual inflammation at the ECM implant site. Three dogs in the group receiving the Dacron trade mark mesh were treated with Keflex trade mark (500 mg bid x 7 days) for signs of septicemia. A quantitative bacterial count of the implant sites at the time of sacrifice showed 6.52 x 10(5) +/- 1.2 x 10(6) and 6.5 x 10(2) +/- 1.8 x 10(3) bacteria per gram of tissue for the Dacron trade mark and ECM scaffold sites, respectively (P <.03). The ECM implant material was more resistant than the synthetic implant material to persistent infection following deliberate bacterial contamination and the ECM scaffold supported constructive tissue remodeling.

Porcine small intestine submucosa as a flexor tendon graft

An attractive strategy for tendon tissue engineering is the use of natural extracellular matrices as scaffold materials. One matrix that has been shown to promote healing and regeneration of neotissue in various applications is porcine-derived small intestinal submucosa. It was the objective of this study to investigate small intestinal submucosa for intrasynovial flexor tendon grafting in a canine model. We hypothesized that at 6 weeks small intestinal submucosa grafts would undergo host cell infiltration, neovascularization, and replacement by host neotendon. We also hypothesized that small intestinal submucosa grafts would be incorporated by the host without extensive adhesions to surrounding tissues and therefore maintain normal digit function. An intrasynovial tendon autograft was used as a gold standard. At 6 weeks the intrasynovial tendon autografts remained viable, contained normal numbers of cells along their length, and had minimal peritendinous adhesions. Four of six autografts had normal function as determined by rotation of the distal interphalangeal joint. Also at 6 weeks, the small intestinal submucosa grafts had host cell infiltration, neovascularization, and wavy, oriented tissue. However, ubiquitous adhesions together with impaired function in all cases suggest that small intestinal submucosa grafts in the configuration used are not suitable as full-length intrasynovial grafts in this tendon and animal model.

Muscle-derived stem cells seeded into acellular scaffolds develop calcium-dependent contractile activity that is modulated by nicotinic receptors

OBJECTIVES

To explore the contractile activity and physiologic properties of muscle-derived stem cells (MDSCs) incorporated into small intestinal submucosa (SIS) scaffolds.

METHODS

MDSCs were harvested from mice hind leg muscles using the preplate technique and stably transfected with a plasmid to express the LacZ reporter gene. Fifty different preparations of SIS cultured with MDSCs (MDSC/SIS) or SIS alone were incubated at 37 degrees C for 1, 4, and 8 weeks and also were mounted in a bath to measure the isometric contractions.

RESULTS

LacZ and Masson-trichrome staining revealed MDSCs could migrate into and distribute throughout the SIS and form myotubes. In MDSC/SIS, spontaneous contractile activities were noted in the 4-week (five of six specimens) and 8-week (eight of eight specimens) cultures, but not in 1-week cultures (n = 11). All SIS control groups after 1 (n = 11), 4 (n = 6), and 8 (n = 8) weeks of incubation did not show any activity. In most of the 4-week, and all of the 8-week, MDSC/SIS cultures, the frequency and amplitude of spontaneous contractile activities were decreased by succinylcholine 10 microM and 20 microM. Electrical field stimulation, carbachol, and KCl did not alter the frequency, amplitude, or pattern of spontaneous contractile activities in MDSC/SIS. Spontaneous contractile activities were blocked by Ca(32+)-free Krebs solution with ethyleneglycoltetraacetic acid 200 microM and distilled water.

CONCLUSIONS

MDSCs could be incorporated into SIS-forming myotubes capable of contracting. The contractile activity of this three-dimensional construct is Ca(2+) dependent and is modulated by nicotinic receptors. MDSC seeding of an acellular matrix may become a functional sling to reengineer the deficient sphincter or as contractile bladder augmentation.

Evaluation of a collagen patch as a method of enhancing ventriculotomy healing in Japanese quail (Coturnix coturnix japonica)

OBJECTIVE

To assess the ability of a porcine submucosal collagen patch to enhance ventriculotomy healing in quail.

STUDY DESIGN

Histologic assessment of wound repair after ventriculotomy. Animal Population-Eighteen adult Japanese quail.

METHODS

All quail had a ventriculotomy through the caudoventral thin muscle. The quail were randomly assigned to 1 of 2 groups: group I (n = 9) had routine closure and group II (n = 9) had routine closure and the application of a porcine submucosal collagen patch over the serosal surface of the ventricular suture line. Three quail from each group underwent necropsy at 7, 14, and 21 days after surgery and healing of the ventriculotomy site was evaluated by microscopy.

RESULTS

Ventricular mucosal epithelium was completely healed at 21 days postoperatively. Time to restoration of the ventricular submucosal integrity was variable in both groups. There was evidence of a gross or microscopic perforation in 4 quail in group II, which was statistically significant (P =.041). Quail with perforations had significantly elevated numbers of ventricular serosal lymphoid aggregates compared with those without perforations (P =.029). There were no other significant temporal differences between group I and group II for mortality or histopathologic grading of wound healing.

CONCLUSIONS

A porcine collagen patch did not enhance ventriculotomy wound healing. Subjectively, the collagen patch might have contributed to perforation by the generation of a lymphocytic xenograft rejection response.

CLINICAL RELEVANCE

Ventriculotomy can be safely performed using routine closure methods in healthy birds.