Production and characterisation of acellular porcine pulmonary heart valve conduits

Cardiac valve replacement is the second most common heart operation. Currently available replacement heart valves all have limitations. This study aimed to produce and
characterise a decellularised, biocompatible porcine pulmonary root conduit for use in the Ross procedure. A process for the decellularisation of porcine pulmonary roots was developed incorporating trypsin (2.25 × 104 Unit.ml-1) digestion of the adventitial surface of the scraped pulmonary artery and sequential treatment with: hypotonic Tris buffer (HTB; 10mM Tris pH 8.0, 0.1% (w/v) EDTA, 10KIU aprotinin), 0.1% (w/v)SDS in HTB, two cycles of DNase and RNase, and sterilisation with 0.1% (v/v)
peracetic acid.

Histology confirmed an absence of cells and retention of the gross histoarchitecture. DNA levels were reduced by >90 % throughout the decellularised tissue and functional
genes were not detected using PCR. Immunohistochemistry showed a lack of α-gal epitopes and confirmed cell removal but a loss of collagen IV. In vitro biocompatibility
studies indicated the decellularised leaflets were not cytotoxic while the pulmonary wall was shown to reduce 3T3 cells viability in 3 out of 6 samples.

Uniaxial tensile testing to failure demonstrated no significant difference in the tensile properties between the fresh and decellularised leaflets and pulmonary walls in the circumferential and radial directions with the exception of the elastin phase slope of the pulmonary artery in both directions which showed a significant decrease in the decellularised tissue. Pulsatile flow testing indicated the decellularised pulmonary roots
had excellent hydrodynamic function and leaflet kinematics in comparison to the fresh tissue. Initial attempts to culture fresh pulmonary roots in a heart valve bioreactor were unsuccessful, indicating a need to develop the physiological culture system further.

Overall the decellularised porcine pulmonary roots have excellent potential for development of a tissue engineered solution for right ventricular out flow tract reconstruction during the Ross procedure.