Type 2 immunity induced by bladder extracellular matrix enhances corneal wound healing.

The avascular nature of cornea tissue limits its regenerative potential, which may lead to incomplete healing and formation of scars when damaged. Here, we applied micro- and ultrafine porcine urinary bladder matrix (UBM) particulate to promote type 2 immune responses in cornea wounds. Results demonstrated that UBM particulate substantially reduced corneal haze formation as compared to the saline-treated group. Flow cytometry and gene expression analysis showed that UBM particulate suppressed the differentiation of corneal stromal cells into α-smooth muscle actin-positive (αSMA+) myofibroblasts. UBM treatments up-regulated interleukin-4 (IL-4) produced primarily by eosinophils in the wounded corneas and CD4+ T cells in draining lymph nodes, suggesting a cross-talk between local and peripheral immunity. Gata1-/- mice lacking eosinophils did not respond to UBM treatment and had impaired wound healing. In summary, stimulating type 2 immune responses in the wounded cornea can promote proregenerative environments that lead to improved wound healing for vision restoration.

Urinary Bladder Matrix Scaffolds Promote Pericardium Repair in a Porcine Model.

Pericardium closure after cardiac surgery is recommended to prevent postoperative adhesions to the sternum. Synthetic materials have been used as substitutes, with limited results because of impaired remodeling and fibrotic tissue formation. Urinary bladder matrix (UBM) scaffolds promote constructive remodeling that more closely resemble the native tissue. The aim of the study is to evaluate the host response to UBM scaffolds in a porcine model of partial pericardial resection. Twelve Landrace pigs were subjected to a median sternotomy. A 5 × 7 cm pericardial defect was created and then closed with a 5 × 7 cm multilayer UBM patch (UBM group) or left as an open defect (control group). Animals were survived for 8 wk. End points included gross morphology, biomechanical testing, histology with semiquantitative score, and cardiac function. The UBM group showed mild adhesions, whereas the control group showed fibrosis at the repair site, with robust adhesions and injury to the coronary bed. Load at failure (gr) and stiffness (gr/mm) were lower in the UBM group compared with the native pericardium (199.9 ± 59.2 versus 405.3 ± 99.89 g, P = 0.0536 and 44.23 ± 15.01 versus 146.5 ± 24.38 g/mm, P = 0.0025, respectively). In the UBM group, the histology resembled native pericardial tissue, with neovascularization, neofibroblasts, and little inflammatory signs. In contrast, control group showed fibrotic tissue with mononuclear infiltrates and a lack of organized collagen fibers validated with a histologic score. Both groups had normal ultrasonography results without cardiac motility disorders. In this setting, UBM scaffolds showed appropriate features for pericardial repair, restoring tissue properties that could help reduce postsurgical adhesions and prevent its associated complications.

Urinary Bladder Matrix Protects Host in a Murine Model of Bacterial-Induced Lung Infection.

IMPACT STATEMENT: Lung infection is a leading cause of human life lost to morbidity and/or mortality. This problem is exacerbated by the alarming emergence of increasingly antibiotic-resistant (AR) microorganisms worldwide and the lack of effective antimicrobials to overcome the AR bacterial infection. Urinary bladder matrix (UBM) is a biologically derived scaffold material that has been used to promote site-appropriate tissue regeneration and remodeling in a variety of body systems. Our novel findings demonstrate that the preformulated UBM effectively protects the host from methicillin-resistant Staphylococcus aureus (MRSA)- and Pseudomonas aeruginosa-induced murine pneumonia and may provide a viable alternative/supplement for protection against respiratory AR bacterial infection.

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.

Procedure for decellularization of porcine heart by retrograde coronary perfusion.

Perfusion-based whole organ decellularization has recently gained interest in the field of tissue engineering as a means to create site-specific extracellular matrix scaffolds, while largely preserving the native architecture of the scaffold. To date, this approach has been utilized in a variety of organ systems, including the heart, lung, and liver (1-5). Previous decellularization methods for tissues without an easily accessible vascular network have relied upon prolonged exposure of tissue to solutions of detergents, acids, or enzymatic treatments as a means to remove the cellular and nuclear components from the surrounding extracellular environment(6-8). However, the effectiveness of these methods hinged upon the ability of the solutions to permeate the tissue via diffusion. In contrast, perfusion of organs through the natural vascular system effectively reduced the diffusion distance and facilitated transport of decellularization agents into the tissue and cellular components out of the tissue. Herein, we describe a method to fully decellularize an intact porcine heart through coronary retrograde perfusion. The protocol yielded a fully decellularized cardiac extracellular matrix (c-ECM) scaffold with the three-dimensional structure of the heart intact. Our method used a series of enzymes, detergents, and acids coupled with hypertonic and hypotonic rinses to aid in the lysis and removal of cells. The protocol used a Trypsin solution to detach cells from the matrix followed by Triton X-100 and sodium deoxycholate solutions to aid in removal of cellular material. The described protocol also uses perfusion speeds of greater than 2 L/min for extended periods of time. The high flow rate, coupled with solution changes allowed transport of agents to the tissue without contamination of cellular debris and ensured effective rinsing of the tissue. The described method removed all nuclear material from native porcine cardiac tissue, creating a site-specific cardiac ECM scaffold that can be used for a variety of applications.

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.

Hydrated xenogeneic decellularized tracheal matrix as a scaffold for tracheal reconstruction.

Tracheal injury is a rare but complex problem. Primary tracheal reconstructions are commonly performed, but complications such as tension and inadequate vascular supply limit the length of surgical resection. The objective of the present study was to determine whether a hydrated, decellularized porcine tracheal extracellular matrix showed the potential to serve as a functional tracheal replacement graft. Porcine tracheas were decellularized and evaluated to characterize their biochemical composition and biomechanical behavior. Hydrated decellularized tracheal matrix (HDTM) grafts (>5 cm) were implanted heterotopically beneath the strap muscle and wrapped in the omentum in a canine model for 2 and 8 weeks followed by histologic and mechanical analysis. HDTM patches (2 x 3 cm) were also used in a patch tracheoplasty model. The repair site was evaluated bronchoscopically and radiographically, and the grafts were analyzed by histologic methods to evaluate epithelialization and persistence of the cartilage rings. The present study showed that HDTM maintains mechanical characteristics necessary for function under physiologic loading conditions even after 8 weeks of heterotopic implantation. After orthotopic implantation, the grafts were shown to support development of a columnar, pseudostratified, ciliated epithelium, but the cartilage structures showed histologic evidence of degradation and limited new cartilage formation. The results of the study showed tracheal ECM scaffolds support the formation of site-specific epithelium and provide sufficient mechanical integrity withstand physiologic pressures in the short-term. However, for long-term success, it appears that pre-implantation to allow vascularization or preseeding of the graft with chondrocytes will be necessary.