Repair of the thoracic wall with an extracellular matrix scaffold in a canine model

Construction of extracellular matrix-based 3D hydrogel and its effects on cardiomyocytes

Some discoveries resulted from 2-dimensional (2D) cultured cardiac cells have been disqualified in animal testing and later clinical trials. Extracellular matrix (ECM) plays a vital role in cardiac homeostasis, cardiac ECM (cECM)-based 3D cell cultures can mimics the physiological and pathological conditions in vivo closely, it is hopeful of addressing this challenge. Construction of cECM-based 3-dimensional (3D) hydrogel (cECM3DH) and its effects on cell behaviors were studied here. The results indicated that cellular compartments could be efficiently removed from heart tissue via sodium dodecyl sulfonate (SDS)- and Triton X-100-mediated decellularization, remaining the natural fibrous network structure and major proteins. 3D hydrogel consisted of 1 × 107 cells/mL cells and 75% cECM could promote the proliferation and anti-apoptosis ability of human embryonic kidney (HEK)-293T cells. 0.25% trypsin or 0.20% collagenase was suitable to retrieve these cells from 3D hydrogel for further researches. Compared with 2D culture system, cECM3DH could significantly increase the proportion of GATA 4+ cardiomyocytes (CMs) derived from heart tissue of neonatal mouse or induced differentiation of embryonic stem cells (ESCs) (P < 0.05) The expression levels of mature genes including cTnT, JCN, CaV1.2, MYL2, CASQ2, NCX1, and Cx43 of these CMs in adult pig cECM-based 3D hydrogel (APcECM3DH) were significantly higher than that in 2D culture system and in newborn piglet cECM-based 3D hydrogel (NPcECM3DH), respectively (P < 0.05). Therefore, cECM3DH supports the generation of primary CMs and ESC-derived CMs, APcECM3DH was more conducive to promoting CM maturation, which contributes to building 3D model for pathogenesis exploration, drug screening, and regenerative medicine of heart diseases.

Human Bronchial Epithelial Cell Growth on Homologous Versus Heterologous Tissue Extracellular Matrix

BACKGROUND

Extracellular matrix (ECM) bioscaffolds produced by decellularization of source tissue have been effectively used for numerous clinical applications. However, decellularized tracheal constructs have been unsuccessful due to the immediate requirement of a functional airway epithelium on surgical implantation. ECM can be solubilized to form hydrogels that have been shown to support growth of many different cell types. The purpose of the present study is to compare the ability of airway epithelial cells to attach, form a confluent monolayer, and differentiate on homologous (trachea) and heterologous (urinary bladder) ECM substrates for potential application in full tracheal replacement.

MATERIALS AND METHODS

Porcine tracheas and urinary bladders were decellularized. Human bronchial epithelial cells (HBECs) were cultured under differentiation conditions on acellular tracheal ECM and urinary bladder matrix (UBM) bioscaffolds and hydrogels and were assessed by histology and immunolabeling for markers of ciliation, goblet cell formation, and basement membrane deposition.

RESULTS

Both trachea and urinary bladder tissues were successfully decellularized. HBEC formed a confluent layer on both trachea and UBM scaffolds and on hydrogels created from these bioscaffolds. Cells grown on tracheal and UBM hydrogels, but not on bioscaffolds, showed positive-acetylated tubulin staining and the presence of mucus-producing goblet cells. Collagen IV immunolabeling showed basement membrane deposition by these cells on the surface of the hydrogels.

CONCLUSIONS

ECM hydrogels supported growth and differentiation of HBEC better than decellularized ECM bioscaffolds and show potential utility as substrates for promotion of a mature respiratory epithelium for regenerative medicine applications in the trachea.

Graft alignment impacts the regenerative response of skeletal muscle after volumetric muscle loss in a rat model

A key event in the etiology of volumetric muscle loss (VML) injury is the bulk loss of structural cues provided by the underlying extracellular matrix (ECM). To re-establish the lost cues, there is broad consensus within the literature supporting the utilization of implantable scaffolding. However, while scaffold based regenerative medicine strategies have shown potential, there remains a significant amount of outcome variability observed across the field. We suggest that an overlooked source of outcome variability is differences in scaffolding architecture. The goal of this study was to test the hypothesis that implant alignment has a significant impact on genotypic and phenotypic outcomes following the repair of VML injuries. Using a rat VML model, outcomes across three autograft implant treatment groups (aligned implants, 45° misaligned, and 90° misaligned) and two recovery time points (2 weeks and 12 weeks) were examined (n = 6-8/group). At 2 weeks post-repair there were no significant differences in muscle mass and torque recovery between the treatment groups, however we did observe a significant upregulation of MyoD (2.5 fold increase) and Pax7 (2 fold increase) gene expression as well as the presence of immature myofibers at the implant site for those animals repaired with aligned autografts. By 12 weeks post-repair, functional and structural differences between the treatment groups could be detected. Aligned autografts had significantly greater mass and torque recovery (77 ± 10% of normal) when compared to 45° and 90° misaligned autografts (64 ± 10% and 61 ± 11%, respectively). Examination of tissue structure revealed extensive fibrosis and a significant increase in non-contractile tissue area fraction for only those animals treated using misaligned autografts. When taken together, the results suggest that implant graft orientation has a significant impact on in-vivo outcomes and indicate that the effect of graft alignment on muscle phenotype may be mediated through genotypic changes to myogenesis and fibrosis at the site of injury and repair. STATEMENT OF SIGNIFICANCE: A key event in the etiology of volumetric muscle loss injury is the bulk loss of architectural cues provided by the underlying extracellular matrix. To re-establish the lost cues, there is broad consensus within the literature supporting the utilization of implantable scaffolding. Yet, although native muscle is a highly organized tissue with network and cellular alignment in the direction of contraction, there is little evidence within the field concerning the importance of re-establishing native architectural alignment. The results of this study suggest that critical interactions exist between implant and native muscle alignment cues during healing, which influence the balance between myogenesis and fibrosis. Specifically, it appears that alignment of implant architectural cues with native muscle cues is necessary to create a pro-myogenic environment and contractile force recovery. The results also suggest that misaligned cues may be pathological, leading to fibrosis and poor contractile force recovery.

Extracellular Matrix-Based Biomaterials and Their Influence Upon Cell Behavior

Biologic scaffold materials composed of allogeneic or xenogeneic extracellular matrix (ECM) are commonly used for the repair and remodeling of injured tissue. The clinical outcomes associated with implantation of ECM-based materials range from unacceptable to excellent. The variable clinical results are largely due to differences in the preparation of the material, including characteristics of the source tissue, the method and efficacy of decellularization, and post-decellularization processing steps. The mechanisms by which ECM scaffolds promote constructive tissue remodeling include mechanical support, degradation and release of bioactive molecules, recruitment and differentiation of endogenous stem/progenitor cells, and modulation of the immune response toward an anti-inflammatory phenotype. The methods of ECM preparation and the impact of these methods on the quality of the final product are described herein. Examples of favorable cellular responses of immune and stem cells associated with constructive tissue remodeling of ECM bioscaffolds are described.

Large Hiatal Hernia Repair with Urinary Bladder Matrix Graft Reinforcement and Concomitant Sleeve Gastrectomy

Background:

There is no current consensus on the management of large hiatal hernias concomitant with performance of a sleeve gastrectomy procedure. Proposed solutions have included performing a modified Nissen fundoplication, performing cruroplasty alone, utilizing the Linx device, performing cruroplasty with reinforcement material, and avoiding the sleeve procedure altogether in favor of a bypass procedure in order to minimize gastroesophageal reflux. Urinary bladder matrix (UBM) represents a biologically derived material for use in hiatal hernia repair reinforcement with the potential to improve durability of repair without incurring the risks of other reinforcement materials.

Methods:

This study reports the results of a retrospective chart review of 32 cases of large hiatal hernia repair utilizing both primary crural repair and UBM reinforcement concomitant with laparoscopic sleeve gastrectomy by a single surgeon. Hernia diameter averaged 6 cm (range 4–9 cm). After an average of 1 year followup, 30 patients were assessed for subjective symptoms of gastroesophageal reflux (GERD) using the Gastroesophageal Reflux Disease-Health Related Quality of Life (GERD-HRQL) score. Twenty patients were evaluated with either upper gastrointestinal (GI) series, endoscopy, or both.

Results:

Each repair was successful and completed laparoscopically concomitant with sleeve gastrectomy. Anterior and posterior cruroplasty was performed using interrupted 0-Ethibond suture using the Endostitch device. The UBM graft exhibited favorable handling characteristics placed as a keyhole geometry sutured to the crura with absorbable suture. A careful chart review was undertaken to assess for complications. There have been no reoperations. After a median of 12 months (range, 4–27 months) of followup, an assessment of recurrences or long-term complications was completed. Median GERD-HRQL score was 6, with a range of 0 to 64 (of possible 75), indicating very low-level reflux symptomatology. Follow-up upper GI radiographs or endoscopy were obtained in 20 cases and show intact repairs.

Conclusion:

In this series of 32 cases, laparoscopic cruroplasty with UBM graft reinforcement has been effective and durable at 12 months of followup. This technique may offer one satisfactory solution for large hiatal hernia repair concomitant with laparoscopic sleeve gastrectomy that may achieve a durable repair with low GERD symptoms.

Comparison of in vivo remodeling of urinary bladder matrix and acellular dermal matrix in an ovine model

Aim: Biologically derived surgical graft materials come from a variety of sources with varying mechanical properties. This study aimed to evaluate the host response and mechanical performance of two extracellular matrix devices in a large animal preclinical model. Materials & methods: Bilateral defects were created in the fascia lata of sheep and repaired with either an acellular dermal matrix (ADM) or urinary bladder matrix (UBM). After 1 or 3 months, the repair site was explanted for histological and mechanical analysis. Results & conclusion: Despite pre-implantation mechanical differences, both UBM and ADM demonstrated similar mechanical performance at 3 months. However, UBM was completely remodeled into site-appropriate tissue by 3 months, while ADM showed limited tissue incorporation.

Retrorectus repair of incisional ventral hernia with urinary bladder matrix reinforcement in a long-term porcine model

Aim: Not all biologically derived materials elicit the same host response when used for reinforcement of ventral hernia repairs. This study aimed to evaluate the remodeling characteristics of the abdominal wall following reinforcement with urinary bladder matrix (UBM) in a large animal preclinical model of ventral hernia repair. Materials & methods: Midline defects in 36 Yucatan minipigs were reinforced with UBM-derived surgical devices using a classic Rives–Stoppa–Wantz approach, and compared with primary repair controls. After 3 or 8 months, the abdominal wall was explanted for histological and mechanical analysis. Results & conclusion: All UBM-derived surgical devices were completely resorbed within 8 months and facilitated deposition of vascularized, biomechanically functional connective tissue in the retrorectus plane, with no evidence of hernia formation.

Extracellular Matrix Bioscaffolds for Building Gastrointestinal Tissue

Regenerative medicine is a rapidly advancing field that uses principles of tissue engineering, developmental biology, stem cell biology, immunology, and bioengineering to reconstruct diseased or damaged tissues. Biologic scaffolds composed of extracellular matrix have shown great promise as an inductive substrate to facilitate the constructive remodeling of gastrointestinal (GI) tissue damaged by neoplasia, inflammatory bowel disease, and congenital or acquired defects. The present review summarizes the preparation and use of extracellular matrix scaffolds for bioengineering of the GI tract, identifies significant advances made in regenerative medicine for the reconstruction of functional GI tissue, and describes an emerging therapeutic approach.

Biologic Scaffolds

Biologic scaffold materials composed of allogeneic or xenogeneic extracellular matrix are commonly used for the repair and functional reconstruction of injured and missing tissues. These naturally occurring bioscaffolds are manufactured by the removal of the cellular content from source tissues while preserving the structural and functional molecular units of the remaining extracellular matrix (ECM). The mechanisms by which these bioscaffolds facilitate constructive remodeling and favorable clinical outcomes include release or creation of effector molecules that recruit endogenous stem/progenitor cells to the site of scaffold placement and modulation of the innate immune response, specifically the activation of an anti-inflammatory macrophage phenotype. The methods by which ECM biologic scaffolds are prepared, the current understanding of in vivo scaffold remodeling, and the associated clinical outcomes are discussed in this article.

Regenerative Rehabilitation: Combining Stem Cell Therapies and Activity-Dependent Stimulation

The number of clinical trials in regenerative medicine is burgeoning, and stem cell/tissue engineering technologies hold the possibility of becoming the standard of care for a multitude of diseases and injuries. Advances in regenerative biology reveal novel molecular and cellular targets, with potential to optimize tissue healing and functional recovery, thereby refining rehabilitation clinical practice. The purpose of this review is to (1) highlight the potential for synergy between the fields of regenerative medicine and rehabilitation, a convergence of disciplines known as regenerative rehabilitation; (2) provide translational examples of regenerative rehabilitation within the context of neuromuscular injuries and diseases; and (3) offer recommendations for ways to leverage activity dependence via combined therapy and technology, with the goal of enhancing long-term recovery. The potential clinical benefits of regenerative rehabilitation will likely become a critical aspect in the standard of care for many neurological and musculoskeletal disorders.

Laparoscopic Rectopexy with Urinary Bladder Xenograft Reinforcement

BACKGROUND AND OBJECTIVES

Rectal prolapse is often repaired laparoscopically, frequently with the use of reinforcement material. Both synthetic and biologically derived materials reduce recurrence rate compared to primary suture repair. Synthetic mesh introduces potential complications such as mesh erosion, fibrosis, and infection. Urinary bladder matrix (UBM) represents a biologically derived material for reinforcement of rectal prolapse repair with the potential to improve durability without risks of synthetic materials. The objective of the study is to evaluate the effectiveness, durability, and functional result of laparoscopic rectopexy using urinary bladder matrix xenograft reinforcement at three years follow up.

METHODS

The 20 cases presented describe rectal prolapse repair by means of laparoscopic rectopexy with presacral UBM reinforcement. Patients were followed up for an average of 3 years and assessed with interviews, physical examination, manometry, and the fecal incontinence severity index (FISI).

RESULTS

Each repair was completed laparoscopically. UBM exhibited favorable handling characteristics when sutured to the sacrum and the lateral rectal walls. One patient underwent laparoscopic drainage of a postoperative abscess; no other complications occurred. In 3 years of follow-up, there have been no full-thickness recurrences, erosions, reoperations, or long-term complications. Two patients exhibited a small degree of mucosal prolapse on follow-up physical examination that did not require surgery. Three-year FISI scores averaged 8 (range, 0-33 of a possible 61), indicating low fecal incontinence symptomatology. Follow-up anorectal manometry was performed in 9 patients, showing mixed results.

CONCLUSION

Surgeons may safely use laparoscopic rectopexy with UBM reinforcement for repair of rectal prolapses. In this series, repairs with UBM grafts have been durable at 3-year follow-up and may be an alternative to synthetic mesh reinforcement of rectal prolapse repairs. Future studies may compare the advantages and cost-effectiveness of reinforcement materials for rectal prolapse repair.

Hiatal Hernia Repair with Novel Biological Graft Reinforcement

Background and Objectives:

Hiatal hernias are repaired laparoscopically with increasing use of reinforcement material. Both synthetic and biologically derived materials reduce the recurrence rate compared to primary crural repair. Synthetic mesh introduces complications, such as mesh erosion, fibrosis, and infection. Urinary bladder matrix (UBM) represents a biologically derived material for use in hiatal hernia repair reinforcement with the potential to improve durability of repair without incurring the risks of other reinforcement materials.

Methods:

The 15 cases presented involved hiatal hernia repair with primary crural repair with UBM reinforcement and fundoplication. Patients were followed for an average of 3 years, and were assessed with upper gastrointestinal (GI) series, endoscopy, and assessments of subjective symptoms of gastroesophageal reflux disease (GERD).

Results:

Hernia diameters averaged 6 cm. Each repair was successful and completed laparoscopically. UBM exhibited favorable handling characteristics when placed as a horseshoe-type graft sutured to the crura. One patient underwent endoscopic balloon dilatation of a mild postoperative stenosis that resolved. No other complications occurred. In more than 3 years of follow-up, there have been no recurrences or long-term complications. GERD-health-related quality of life (HRQL) scores averaged 6 (range, 0–12, of a possible 50), indicating little reflux symptomatology. Follow-up upper GI series were obtained in 9 cases and showed intact repairs. An upper endoscopy was performed in 8 patients and showed no recurrences.

Conclusion:

Surgeons may safely use laparoscopic fundoplication with UBM reinforcement for successful repair of hiatal hernias. In this series, repairs with UBM grafts have been durable at 3 years of follow-up and may serve as an alternative to synthetic mesh reinforcement of hiatal hernia repairs.

Glottic regeneration with a tissue-engineering technique, using acellular extracellular matrix scaffold in a canine model

Acellular extracellular matrix scaffold derived from porcine urinary bladder (UBM) is decellularized material that has shown success for constructive remodelling of various tissues and organs. The regenerative effects of UBM were reported for the tympanic membrane, oesophagus, trachea, larynx, pleura and pericardium in animal studies, with promising results. The aim of this study was to investigate the regenerative effects of UBM on hemilarynx, using a canine model. A left partial hemilaryngectomy was performed and the surgical defects were reconstructed by insertion of UBM scaffold. Although local infection was observed in one dog in 1 week after implantation of the scaffold, all dogs showed good re-epithelialization with minimum complication in 1 month. The effect of regeneration of the larynx was evaluated 6 months after the operation. The excised larynx experiments were performed to measure phonation threshold pressure (PTP), normalized mucosal wave amplitude (NMWA) and normalized glottal gap (NGG). The results of the measurements showed that PTP was normal or near normal in two cases and NMWA was within normal range in three cases, although there were individual variations. Histological examination was completed to evaluate structural changes in the scaffold with the appearance of the new cartilaginous structure. However, the regenerated vocal fold mucosa was mostly scarred. The UBM scaffold has shown to be biocompatible, biodegradable and useful for tissue regeneration of the hemilarynx, with possible restoration of function of the vocal fold. The vocal fold mucosa was scarred, which is the next challenge to be addressed. Copyright © 2014 John Wiley & Sons, Ltd.

Decellularized scaffolds in regenerative medicine

Allogeneic organ transplantation remains the ultimate solution for end-stage organ failure. Yet, the clinical application is limited by the shortage of donor organs and the need for lifelong immunosuppression, highlighting the importance of developing effective therapeutic strategies. In the field of regenerative medicine, various regenerative technologies have lately been developed using various biomaterials to address these limitations. Decellularized scaffolds, derived mainly from various non-autologous organs, have been proved a regenerative capability in vivo and in vitro and become an emerging treatment approach. However, this regenerative capability varies between scaffolds as a result of the diversity of anatomical structure and cellular composition of organs used for decellularization. Herein, recent advances in scaffolds based on organ regeneration in vivo and in vitro are highlighted along with aspects where further investigations and analyses are needed.

Derivation and characterization of porcine vocal fold extracellular matrix scaffold

OBJECTIVES/HYPOTHESIS

To optimize decellularization of porcine vocal folds (VF) and quantify human bone marrow-derived mesenchymal stem cell (BM-MSC) interactions with this matrix to provide a foundation for regenerative approaches to VF repair.

STUDY DESIGN AND METHODS

Vocal folds were dissected from porcine larynges and three decellularization protocols were compared, each consisting of washes and mechanical agitations with different combinations of reagents. DNA content was analyzed via Quant-iT Picogreen assay and hematoxylin and eosin staining. Bone marrow-derived MSCs were then seeded onto the decellularized VF matrices. Morphology, metabolic activity, DNA content, and gene expression were assessed using LIVE/DEAD Cell Viability, alamarBlue Cell Viability Assay, Quant-iT Picogreen assay, and quantitative polymerase chain reaction, respectively.

RESULTS

The most successful decellularization protocol removed 95% DNA content within 1 day, compared to several days required for previously described protocols. Histology confirmed the retention of extracellular matrix (ECM) and its components, including glycosaminoglycans, collagen, and fibrin, while void of nuclear/cellular content. Decellularized scaffolds were then seeded with BM-MSCs. Similar DNA quantities were observed after 24 hours of seeding within the VF-ECM scaffold when compared to cells on tissue culture plastic (TCP). LIVE/DEAD staining of the seeded VF-ECM confirmed excellent cell viability, and the metabolic activity of BM-MSCs increased significantly on VF-ECM compared to TCP. Endoglin gene expression decreased, suggestive of differentiation.

CONCLUSION

Porcine VFs can be efficiently decellularized within 5 hours using a combination of sodium deoxycholate and peracetic acid. Decellularized VF-ECM supported attachment and growth of human BM-MSCs, with evidence of differentiation.

LEVEL OF EVIDENCE

N/A.

A novel technique for simultaneous whole-body and multi-organ decellularization: umbilical artery catheterization as a perfusion-based method in a sheep foetus model

The aim of this study was to develop a method to generate multi-organ acellular matrices. Using a foetal sheep model have developed a method of systemic pulsatile perfusion via the umbilical artery which allows for simultaneous multi-organ decellularization. Twenty sheep foetuses were systemically perfused with Triton X-100 and sodium dodecyl sulphate. Following completion of the whole-body decellularization, multiple biopsy samples were taken from different parts of 21 organs to ascertain complete cell component removal in the preserved extracellular matrices. Both the natural and decellularized organs were subjected to several examinations. The samples were obtained from the skin, eye, ear, nose, throat, cardiovascular, respiratory, gastrointestinal, urinary, musculoskeletal, central nervous and peripheral nervous systems. The histological results depicted well-preserved extracellular matrix (ECM) integrity and intact vascular structures, without any evidence of residual cellular materials, in all decellularized bioscaffolds. Scanning electron microscope (SEM) and biochemical properties remained intact, similar to their age-matched native counterparts. Preservation of the collagen structure was evaluated by a hydroxyproline assay. Dense organs such as bone and muscle were also completely decellularized, with a preserved ECM structure. Thus, as shown in this study, several organs and different tissues were decellularized using a perfusion-based method, which has not been previously accomplished. Given the technical challenges that exist for the efficient generation of biological scaffolds, the current results may pave the way for obtaining a variety of decellularized scaffolds from a single donor. In this study, there have been unique responses to the single acellularization protocol in foetuses, which may reflect the homogeneity of tissues and organs in the developing foetal body.

The Use of Biologic Scaffolds in the Treatment of Chronic Nonhealing Wounds

Significance: Injuries to the skin as a result of illness or injury, particularly chronic nonhealing wounds, present a major healthcare problem. Traditional wound care approaches attempt to control the underlying causes, such as infection and ischemia, while the application of wound dressings aims to modify a poorly healing wound environment into a microenvironment more closely resembling an acute wound allowing the body to heal the wound naturally. Recent Advances: Regenerative medicine approaches, such as the use of biologic scaffold materials comprising an intact extracellular matrix (ECM) or individual components of the ECM, are providing new therapeutic options that focus upon the provision of biochemical cues that alter the wound microenvironment to facilitate rapid restoration of normal skin architecture. Critical Issues: The incidence of chronic nonhealing wounds continues to increase. For example, between 15% and 20% of diabetics are likely to develop chronic, nonhealing foot wounds creating an increasing burden on healthcare systems worldwide. Future Directions: Developing a thorough understanding of wound microenvironment and the mechanisms by which biologic scaffolds work in vivo has the potential to markedly improve outcomes in the clinical translation for the treatment of chronic wounds.

An acellular biologic scaffold does not regenerate appreciable de novo muscle tissue in rat models of volumetric muscle loss injury

Extracellular matrix (ECM) derived scaffolds continue to be investigated for the treatment of volumetric muscle loss (VML) injuries. Clinically, ECM scaffolds have been used for lower extremity VML repair; in particular, MatriStem™, a porcine urinary bladder matrix (UBM), has shown improved functional outcomes and vascularization, but limited myogenesis. However, efficacy of the scaffold for the repair of traumatic muscle injuries has not been examined systematically. In this study, we demonstrate that the porcine UBM scaffold when used to repair a rodent gastrocnemius musculotendinous junction (MTJ) and tibialis anterior (TA) VML injury does not support muscle tissue regeneration. In the MTJ model, the scaffold was completely resorbed without tissue remodeling, suggesting that the scaffold may not be suitable for the clinical repair of muscle-tendon injuries. In the TA VML injury, the scaffold remodeled into a fibrotic tissue and showed functional improvement, but not due to muscle fiber regeneration. The inclusion of physical rehabilitation also did not improve functional response or tissue remodeling. We conclude that the porcine UBM scaffold when used to treat VML injuries may hasten the functional recovery through the mechanism of scaffold mediated functional fibrosis. Thus for appreciable muscle regeneration, repair strategies that incorporate myogenic cells, vasculogenic accelerant and a myoconductive scaffold need to be developed.

Short-Term Results of Treating Primary and Recurrent Anal Fistulas with a Novel Extracellular Matrix Derived from Porcine Urinary Bladder

Anal fistulas are difficult to treat because they are often recalcitrant to medical therapies and surgical treatment may lead to significant morbidities. A recent novel biologically derived graft from porcine urinary bladder (MatriStem™) has shown great promise in experimental studies of tissue regeneration in diverse tissues. The objectives of this study were to evaluate the safety and short-term efficacy of MatriStem for treatment of anal fistulas. This was a retrospective study of patients treated from January 3, 2012 to March 3, 2014 at the University of Pittsburgh Medical Center. MatriStem was used to treat patients with anal fistulas by implanting it uniformly with a single application in all patients using a standardized protocol. Data were collected retrospectively from hospital records and office charts. Nineteen fistulas were treated with MatriStem. There were no adverse complications. Overall efficacy of MatriStem was 79 per cent with healing occurring in a mean time of 17 days and mean follow-up of seven months (range 1–26 months). MatriStem was effective in healing in 75 per cent of primary anal fistulas and 86 per cent of recurrent fistulas. MatriStem seems to be a safe and promising treatment for primary and recurrent anal fistulas, and warrants further study and clinical trials to substantiate widespread clinical use.

Application of the orthoplastic reconstructive ladder to preserve lower extremity amputation length

BACKGROUND

A primary goal in traumatic lower extremity amputation management is preservation of limb length. Energy expenditure during ambulation directly correlates with residual limb length, preserved limb segments, and stable joint preservation. An additional factor affecting limb function includes achieving adequate residual limb soft tissue coverage. This report describes techniques for achieving a stable soft tissue envelope to facilitate limb length and joint preservation.

METHODS

A series of traumatic amputation cases with inadequate soft tissue coverage are reviewed. Concepts from the reconstructive surgery ladder were used to achieve residual limb soft tissue coverage and to preserve lower extremity amputation length.

RESULTS

Soft tissue coverage was accomplished through a series of methods including delayed primary closure with assistance from an external tissue expander, use of acellular dermal regenerative templates combined with split-thickness skin grafting and negative-pressure wound therapy, use of biologic scaffolds such as extracellular porcine urinary bladder matrix combined with delayed skin grafting, and local pedicle flaps or adjacent tissue rearrangements and free tissue transfers.

CONCLUSIONS

The preservation of residual limb length in lower extremity amputations is crucial to optimize prosthetic fitting and to obtain the maximal functional outcome. A series of cases are presented that outline soft tissue coverage options for preserving maximal residual limb length. Applying various concepts from the reconstructive ladder may allow for viable soft tissue coverage to maximize functional outcome.

Tracheal bioengineering: the next steps. Proceeds of an International Society of Cell Therapy Pulmonary Cellular Therapy Signature Series Workshop, Paris, France, April 22, 2014

There has been significant and exciting recent progress in the development of bioengineering approaches for generating tracheal tissue that can be used for congenital and acquired tracheal diseases. This includes a growing clinical experience in both pediatric and adult patients with life-threatening tracheal diseases. However, not all of these attempts have been successful, and there is ongoing discussion and debate about the optimal approaches to be used. These include considerations of optimal materials, particularly use of synthetic versus biologic scaffolds, appropriate cellularization of the scaffolds, optimal surgical approaches and optimal measure of both clinical and biologic outcomes. To address these issues, the International Society of Cell Therapy convened a first-ever meeting of the leading clinicians and tracheal biologists, along with experts in regulatory and ethical affairs, to discuss and debate the issues. A series of recommendations are presented for how to best move the field ahead.

Neurorestorative effect of urinary bladder matrix-mediated neural stem cell transplantation following traumatic brain injury in rats

Traumatic brain injury (TBI) is a leading cause of cell death and disability among young adults and lacks a successful therapeutic strategy. The multiphasic injuries of TBI severely limit the success of conventional pharmacological approaches. Recent successes with transplantation of stem cells in bioactive scaffolds in other injury paradigms provide new hope for the treatment of TBI. In this study, we transplanted neural stem cells (0.5x10(5) cells/µl) cultured in a bioactive scaffold derived from porcine urinary bladder matrix (UBM; 4 injection sites, 2.5µl each) into the rat brain following controlled cortical impact (CCI, velocity, 4.0 m/sec; duration, 0.5 sec; depth, 3.2mm). We evaluated the effectiveness of this strategy to combat the loss of motor, memory and cognitive faculties. Before transplantation, compatibility experiments showed that UBM was able to support extended proliferation and differentiation of neural stem cells. Together with its reported anti-inflammatory properties and rapid degradation characteristics in vivo, UBM emerged to be an ideal scaffold. The transplants reduced neuron/tissue loss and white matter injury, and also significantly ameliorated motor, memory, and cognitive impairments. Furthermore, exposure to UBM alone was sufficient to decrease the loss of sensorimotor skills from TBI (examined 3-28 days post-CCI). However, only UBMs that contained proliferating neural stem cells helped attenuate memory and cognitive impairments (examined 26-28 days post-CCI). In summary, these results demonstrate the therapeutic efficacy of stem cells in bioactive scaffolds against TBI and show promise for translation into future clinical use.

The use of skin substitutes in the treatment of the hand and upper extremity

The introduction of skin substitutes in the last decade has dramatically changed how we think about the concept of "non-healing" wounds. Their use has improved prognosis and reduced morbidity in the treatment of open wounds. This article aims to summarize the development of tissue-engineered skin substitutes, discuss their use, and highlight some specific applications in different clinical settings.

Patch esophagoplasty: esophageal reconstruction using biologic scaffolds

BACKGROUND

Standard techniques for surgical reconstruction of the esophagus remain suboptimal. Primary closure of diseased or injured esophagus has been associated with high morbidity, primarily due to leak and stricture, and synthetic materials are contraindicated due to the high risk of erosion and infection. Degradable bioscaffolds composed of extracellular matrix (ECM) have recently shown promising results in both pre-clinical and clinical settings to prevent stricture after extended endoscopic mucosal resection. We propose a novel surgical technique that utilizes an ECM scaffold as a reconstructive patch to augment the esophageal diameter during primary repair.

METHODS

Four patients requiring esophageal reconstruction underwent a patch esophagoplasty using an ECM scaffold composed of porcine urinary bladder ECM. The full thickness wall of the esophagus was replaced with an ECM patch that was sutured to the edges of the remaining esophagus, similar to the patch angioplasty performed in vascular procedures.

RESULTS

All patients had a favorable clinical outcome with immediate recovery from the procedure and reinstated oral intake after 7 days. One patient had a micro leak at day 5 that closed spontaneously 2 days after drainage. Follow-up studies including barium swallow and esophagogastroduodenoscopy (EGD) showed adequate esophageal emptying through the surgical segment in all patients. The EGD showed complete mucosal remodeling at 2 months, with approximately 20% area contraction at the patch level. The area of the defect was indistinguishable from surrounding healthy tissue. Biopsy of the patch area showed normal squamous epithelium. One of the patients had a separate intrathoracic stricture that required further surgery. Clinical outcomes were otherwise favorable in all cases.

CONCLUSIONS

An alternative for the treatment of esophageal stenosis is presented which uses a biological scaffold and an innovative surgical procedure. Additional work, including prospective studies and long-term follow-up, is required to fully evaluate the potential of this bioscaffold-based regenerative medicine approach for esophageal reconstruction.

Epicardial infarct repair with basic fibroblast growth factor-enhanced CorMatrix-ECM biomaterial attenuates postischemic cardiac remodeling

OBJECTIVES

Dysregulation of extracellular matrix (ECM) following myocardial infarction is a key contributor to myocardial fibrosis, chamber dilation, and progression to heart failure. Basic fibroblast growth factor is a potent inhibitor of fibrosis. We propose a novel surgical procedure leveraging a commercially available ECM biomaterial for the treatment of ischemic heart failure.

METHODS

Epicardial infarct repair using CorMatrix-ECM biomaterial patch (CorMatrix Cardiovascular Inc, Roswell, Ga) was compared with sham in a rat myocardial infarction model. Key indices of ischemic remodeling, including inflammation, fibrosis, and myocardial performance were evaluated 16 weeks post-treatment.

RESULTS

Histology and immunohistochemistry demonstrated comprehensive integration of CorMatrix-ECM biomaterial patch without evidence of immune reaction and an increase in basic fibroblast growth factor expression in treated animals. Functional analysis by serial echocardiography of normal (n = 13), sham (n = 15), nonenhanced CorMatrix-ECM patch (n = 18), and basic fibroblast growth factor-enhanced CorMatrix-ECM patch (n = 10) animals revealed an improvement in ejection fraction in basic fibroblast growth factor-enhanced CorMatrix-ECM patch animals compared with shams (55.3% ± 8.0% vs 35.1% ± 7.6%; P < .001). Prevention of left ventricle remodeling was also confirmed by pressure volume loop analysis, which demonstrated reduced left ventricular end diastolic volumes in basic fibroblast growth factor-enhanced CorMatrix-ECM patch animals (n = 5) compared with shams (n = 6) (208.0 ± 59.3 μL vs 363. 1 ± 108.7 μL; P < .01) and improved left ventricle contractility in nonenhanced CorMatrix-ECM patch (n = 7) and basic fibroblast growth factor-enhanced CorMatrix-ECM patch animals compared with shams (0.709 ± 0.306 and 0.609 ± 0.160 vs 0.437 ± 0.218; P < .05).

CONCLUSIONS

Epicardial infarct repair with basic growth factor-enhanced CorMatrix-ECM biomaterial patch attenuates myocardial remodeling and improves cardiac performance after subacute myocardial infarction in a rat coronary ligation model. These observations establish proof-of-concept for this novel surgical approach.

Urinary bladder matrix promotes site appropriate tissue formation following right ventricle outflow tract repair

The current prevalence and severity of heart defects requiring functional replacement of cardiac tissue pose a serious clinical challenge. Biologic scaffolds are an attractive tissue engineering approach to cardiac repair because they avoid sensitization associated with homograft materials and theoretically possess the potential for growth in similar patterns as surrounding native tissue. Both urinary bladder matrix (UBM) and cardiac ECM (C-ECM) have been previously investigated as scaffolds for cardiac repair with modest success, but have not been compared directly. In other tissue locations, bone marrow derived cells have been shown to play a role in the remodeling process, but this has not been investigated for UBM in the cardiac location, and has never been studied for C-ECM. The objectives of the present study were to compare the effectiveness of an organ-specific C-ECM patch with a commonly used ECM scaffold for myocardial tissue repair of the right ventricle outflow tract (RVOT), and to examine the role of bone marrow derived cells in the remodeling response. A chimeric rat model in which all bone marrow cells express green fluorescent protein (GFP) was generated and used to show the ability of ECM scaffolds derived from the heart and bladder to support cardiac function and cellular growth in the RVOT. The results from this study suggest that urinary bladder matrix may provide a more appropriate substrate for myocardial repair than cardiac derived matrices, as shown by differences in the remodeling responses following implantation, as well as the presence of site appropriate cells and the formation of immature, myocardial tissue.

Coalescence of extracellular matrix (ECM) from porcine urinary bladder (UBM) with a laser-activated chitosan-based surgical adhesive

Urinary bladder matrix (UBM) has been extensively investigated as a naturally occurring biomaterial in therapeutic applications for tissue repair or regeneration, while other strategies involve biopolymers such as chitosan for tissue reconstruction. The coalescence of UBM with chitosan has considerable potential in enhancing tissue reconstruction. Characterisation of a novel, laser-activated, chitosan-based, thin-film surgical adhesive with UBM in various morphologies showed that the films had increased surface rugosities and crystallinities (Ra approx. 0.83 um, approx. 12% crystallinity) when compared to the chitosan adhesive alone (R a = 0.74 um, 7% crystallinity). Tensile strength of the films was significantly increased by the addition of UBM in particulate form (12.1-32.4 MPa). Furthermore, tissue adhesion strengths using these hybrid biomaterials were maintained at approx. 15 kPa compared to 3 kPa for fibrin glue. Histological analysis demonstrated that laser irradiation of the UBM-chitosan adhesive biomaterial caused no thermal damage to tissue. Examination of the cellular response at the material interface showed that 3T3 fibroblasts maintained their regular morphology with enhanced growth compared to films of both chitosan and its adhesive form. These results suggest that coalescence of UBM with a chitosan-based adhesive supports the development of biomaterial devices for sutureless wound closure that could enhance tissue repair and reconstruction.

Right ventricular outflow tract repair with a cardiac biologic scaffold

BACKGROUND

Surgical reconstruction of congenital heart defects is often limited by the nonresorbable material used to approximate normal anatomy. In contrast, biologic scaffold materials composed of resorbable non-cross-linked extracellular matrix (ECM) have been used for tissue reconstruction of multiple organs and are replaced by host tissue. Preparation of whole organ ECM by decellularization through vascular perfusion can maintain much of the native three-dimensional (3D) structure, strength, and tissue-specific composition. A 3D cardiac ECM (C-ECM) biologic scaffold material would logically have structural and functional advantages over materials such as Dacron™ for myocardial repair, but the in vivo remodeling characteristics of C-ECM have not been investigated to date.

METHODS AND RESULTS

A porcine C-ECM patch or Dacron patch was used to reconstruct a full-thickness right ventricular outflow tract (RVOT) defect in a rat model with end points of structural remodeling function at 16 weeks. The Dacron patch was encapsulated by dense fibrous tissue and showed little cellular infiltration. Echocardiographic analysis showed that the right ventricle of the hearts patched with Dacron were dilated at 16 weeks compared to presurgery baseline values. The C-ECM patch remodeled into dense, cellular connective tissue with scattered small islands of cardiomyocytes. The hearts patched with C-ECM showed no difference in the size or function of the ventricles as compared to baseline values at both 4 and 16 weeks.

CONCLUSIONS

The C-ECM patch was associated with better functional and histomorphological outcomes compared to the Dacron patch in this rat model of RVOT reconstruction.

Cultured keratinocytes on urinary bladder matrix scaffolds increase angiogenesis and help in rapid healing of wounds

INTRODUCTION

Urinary Bladder Matrix (UBM) is an extracellular matrix (ECM) scaffold. It is now used in wound care management of partial and full-thickness wounds where conventional methods for wound care usually fail to give satisfactory results.

OBJECTIVE

In this study, the authors are comparing the healing of full-thickness excisional wounds in New Zealand rabbits using either UBM scaffolds alone or in combination with cultured keratinocytes. The wounds were compared grossly and histologically.

MATERIALS AND METHODS

It is a comparative controlled study including 40 full-thickness wounds in 2 groups. Group (A) wounds: treated with UBM scaffolds, Group (B) wounds: treated with UBM scaffolds with cultured keratinocytes. The wounds were examined grossly after 1, 2, and 3 weeks, and were examined histologically at the end of the 3rd week using ordinary hematoxylin-eosin staining techniques.

RESULTS

All the wounds healed completely by the end of the 3rd week. Early wound contraction was significantly less in group B. More angiogenic response was evident in all specimens of group B.

CONCLUSION

This study shows that adding cultured keratinocytes to the rough surface of the UBM scaffold may be beneficial in reducing early wound contraction and improving wound vascularity in treatment of full-thickness wounds.

Extracellular matrix powder protects against bleomycin-induced pulmonary fibrosis

Pulmonary fibrosis refers to a group of lung diseases characterized by inflammation, fibroblast proliferation, and excessive collagen deposition. Although the mechanisms underlying pulmonary fibrosis are poorly understood, current evidence suggests that epithelial injury contributes to the development of fibrosis. Regenerative medicine approaches using extracellular matrix (ECM) scaffolds have been shown to promote site-specific tissue remodeling. This led to the hypothesis that particulate ECM would promote normal tissue repair and attenuate bleomycin-induced pulmonary fibrosis. C57BL/6 mice were treated intratracheally with bleomycin or saline with or without a particulate form of ECM scaffold from porcine urinary bladder matrix (UBM-ECM) or enzymatically digested UBM-ECM. Mice were sacrificed 5 and 14 days after exposure. Compared to control mice, bleomycin-exposed mice had similar increases in inflammation in the bronchoalveolar lavage fluid regardless of UBM-ECM treatment. However, 14 days after exposure, lung histology and collagen levels revealed that mice treated with bleomycin and the particulate or digested UBM-ECM had negligible fibrosis, whereas mice given only bleomycin had marked fibrosis. Administration of the particulate UBM-ECM 24 h after bleomycin exposure also significantly protected against pulmonary injury. In vitro epithelial cell migration and wound healing assays revealed that particulate UBM-ECM promoted epithelial cell chemotaxis and migration. This suggests that promotion of epithelial wound repair may be one mechanism in which UBM-ECM limits pulmonary fibrosis.

Composite scaffold provides a cell delivery platform for cardiovascular repair

Control over cell engraftment, survival, and function remains critical for heart repair. We have established a tissue engineering platform for the delivery of human mesenchymal progenitor cells (MPCs) by a fully biological composite scaffold. Specifically, we developed a method for complete decellularization of human myocardium that leaves intact most elements of the extracellular matrix, as well as the underlying mechanical properties. A cell-matrix composite was constructed by applying fibrin hydrogel with suspended cells onto decellularized sheets of human myocardium. We then implanted this composite onto the infarct bed in a nude rat model of cardiac infarction. We next characterized the myogenic and vasculogenic potential of immunoselected human MPCs and demonstrated that in vitro conditioning with a low concentration of TGF-β promoted an arteriogenic profile of gene expression. When implanted by composite scaffold, preconditioned MPCs greatly enhanced vascular network formation in the infarct bed by mechanisms involving the secretion of paracrine factors, such as SDF-1, and the migration of MPCs into ischemic myocardium, but not normal myocardium. Echocardiography demonstrated the recovery of baseline levels of left ventricular systolic dimensions and contractility when MPCs were delivered via composite scaffold. This adaptable platform could be readily extended to the delivery of other reparative cells of interest and used in quantitative studies of heart repair.

Esophageal preservation in five male patients after endoscopic inner-layer circumferential resection in the setting of superficial cancer: a regenerative medicine approach with a biologic scaffold

As a result of injury caused by chronic gastroesophageal reflux, Barrett's esophagus with high-grade dysplasia and esophageal adenocarcinoma are rapidly increasing problems in the United States. The current standard of care involves esophagectomy, a procedure associated with a high morbidity, a negative impact on long term quality of life, and a mortality rate of 1-6 percent. An entirely endoscopic technique for circumferential, long segment en bloc removal of the mucosa and submucosa with subsequent placement of a biologic scaffold material that promotes a constructive remodeling response and minimizes stricture is described herein. The results of this approach are reported for five patients with 4-24-month follow-up. Restoration of normal mature, K4+/K14+, squamous epithelium, and return to a normal diet without significant dysphagia is reported for all patients. Two of five patients show a small focus of recurrent Barrett's esophagus at the gastroesophageal junction, but the entire length and circumference of the reconstituted esophageal mucosa remains free of disease. This experience provides evidence that a regenerative medicine approach may, for the first time, enable aggressive endoscopic resection of early stage neoplasia without the need for esophagectomy and its associated complications.

Preparation of cardiac extracellular matrix from an intact porcine heart

Whole organ engineering would benefit from a three-dimensional scaffold produced from intact organ-specific extracellular matrix (ECM). The microenvironment and architecture provided by such a scaffold would likely support site-appropriate cell differentiation and spatial organization. The methods to produce such scaffolds from intact organs require customized decellularization protocols. In the present study, intact adult porcine hearts were successfully decellularized in less than 10 h using pulsatile retrograde aortic perfusion. Serial perfusion of an enzymatic, nonionic detergent, ionic detergent, and acid solution with hypotonic and hypertonic rinses was used to systematically remove cellular content. The resultant cardiac ECM retained collagen, elastin, and glycosaminoglycans, and mechanical integrity. Cardiac ECM supported the formation of organized chicken cardiomyocyte sarcomere structure in vitro. The intact decellularized porcine heart provides a tissue engineering template that may be beneficial for future preclinical studies and eventual clinical applications.

Diaphragmatic support of a thoracic wall defect in a dog

A large, caudal thoracic mass was removed along with ribs 11 and 12, resulting in an approximate 16 x 14-cm, caudal thoracic wall defect in a dog. The diaphragmatic musculature was mobilized and used to support the thoracic wall defect. To our knowledge, this method of thoracic wall repair has not been previously reported. This procedure allowed for airtight closure of the thoracic cavity, provided physical support, eliminated the need for muscle flaps or commercially available meshes, and provided a good cosmetic appearance without negatively affecting the dog's athletic performance.

Novel utilization of serum in tissue decellularization

Decellularization of native tissues is a promising technique with numerous applications in tissue engineering and regenerative medicine. However, there are various limitations of currently available decellularization methods, such as alteration of extracellular matrix mechanics and restricted use on certain tissues. This study was conducted to explore the effect of serum on the decellularization of various types of tissues. Fetal bovine serum-containing cell culture medium endothelial growth media-2 removed DNA but not cellular beta-actin from human umbilical artery after detergent treatment, without compromising the tissue mechanical strength assessed by burst pressure. In addition, the effect of serum-containing endothelial growth media-2 on DNA removal was replicated in other types of tissues such as tissue-engineered vessels and myocardium. Other types of serum, including human serum, were also shown to remove DNA from detergent-pretreated tissues. In conclusion, we describe a novel utilization of serum that may have broad applications in tissue decellularization.