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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.

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.

Abstract: 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 × 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. [Copyright &y& Elsevier]