Background:
Aldehyde-fixed pericardium is commonly used in valve implant manufacturing. Despite its wide employment, this tissue undergoes chronic rejection that limits implant performance and durability. In this work, we employed a method to engineer a leaflet-like tissue by seeding aortic valve interstitial cells (VIC) into fixative-free decellularized pericardium using a bioreactor based approach.
Methods:
Following treatment with hypotonic buffer (Tris-HCl) to induce cell lysis, porcine pericardium was incubated with TritonX-100, to remove adipose tissue and then treated with sodium dodecylsulfate to wash cellular debris. DNA was removed by incubation into a DNAse I solution. Pericardium permeability was measured on samples before and after decellularization (pressure from 735 Pa to 2200 Pa). A direct perfusion bioreactor was employed to seed (3days, 3ml/min) porcine VICs (6.5E+5 cell/scaffold) into decellularized pericardium patches (6mm diameters) and perform long-term culture (up to 14 days, 0.03ml/min). Cell seeding efficiency (Day 3) and cell proliferation (Day 7-14) were evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) staining, histological analyses and fluorescence staining for quiescent/activated VIC markers (DAPI, vimentin, α-smooth muscle actin).
Results:
Permeability tests revealed a significant increase in decellularized samples (1-way ANOVA
p
< 0.05), thus supporting its use in a direct perfusion bioreactor system. MTT staining revealed homogeneous cell seeding distribution, supported by DAPI staining, showing efficient cellularization through the whole patch volume. Computer-based cell nuclei counting revealed a significant cell increase from day 3 to 7 and 14 (
p
<0.05 1-way ANOVA). Immunofluorescence showed a marked reduction of αSMA in cells populating the inner layers.
Conclusions:
Our data show, for the first time, the capability to seed and culture VICs into a cell/fixative free pericardium with a direct perfusion system. Moreover, the use of pericardium treated with our decellularization procedure and recellularized under dynamic conditions supports a more physiological growth of VIC, as suggested by downregulation of αSMA in the inner pericardium layer.