BACKGROUND AND AIM OF THE STUDY: Autologous and glutaraldehyde-treated xenogeneic and homogeneic pericardium has been used extensively in mitral valve repair, but there are a number of limitations associated with its use. These include calcification, limited durability and lack of in vivo regeneration with glutaraldehyde-treated xenografts, as well as the sacrifice of the patient's own pericardium in the case of repair with autologous pericardium. The study aim was to investigate the suitability of decellularized porcine pericardium for heterotopic repair of the mitral valve leaflets, and its potential to regenerate through endogenous cell repopulation in vivo, or in vitro cell seeding prior to implantation. METHODS: Fresh porcine anterior and posterior mitral valve leaflets, together with fresh and decellularized porcine pericardium, were tested histologically, biochemically and biomechanically to investigate potential similarities and differences between the different types of tissue. Subsequently, the decellularized pericardial scaffolds were tested both in terms of biocompatibility, using contact and extract cytotoxicity assays, and in terms of regenerative capacity through porcine mesenchymal stem cell (pMSC) seeding. RESULTS: Histological examination of fresh pericardium and leaflets showed the typical trilaminar and quadlaminar structures of the two tissues, respectively. No cell remnants were observed in the decellularized pericardium, whereas the histoarchitecture of the collagen, elastin and glycosaminoglycan (GAG) matrix appeared well preserved. Significant differences were found in the GAG and hydroxyproline contents and the biomechanics between the leaflet and the pericardial groups. No indication of cytotoxicity was observed with the decellularized pericardial scaffolds. The optimum cell seeding density of pMSCs was 1 x 10(5) cells per cm2, which represented the lowest density at which the cells were capable of repopulating the scaffold by migrating through its full thickness. CONCLUSION: Porcine mitral valve leaflets and porcine fresh/decellularized pericardium shared similar histoarchitectures, but had different biochemical compositions and biomechanics. Decellularized pericardium was shown to be an optimum material for cell repopulation, delivering the necessary biological and biomechanical cues to seeded or migrating cells, and representing a plausible scaffold option for the regeneration of the mitral leaflets in vitro or in vivo, respectively.