Novel method of decellularization of porcine valves using polyethylene glycol and gamma irradiation.
BACKGROUND
Recent tissue-engineered valves are in need of a breakthrough to overcome several limitations against clinical applications. We have developed a new method of decellularization using polyethylene glycol and gamma irradiation.


METHODS
Fresh porcine aortic valves were decellularized using polyethylene glycol and gamma irradiation. These were evaluated by histologic, biochemical (DNA, solubilized protein and collagen content), mechanical (strength test, transmission electron microscopy) and immunologic (porcine endogenous retrovirus and the alpha-1.3 galactosyl epitope) analyses. Implantations into the subcutaneous tissue of rats (1 week, n = 10; 2 months, n = 10) and into the descending aorta of dogs (2 months, n = 6; 6 months, n = 3) were used as in vivo studies.


RESULTS
Complete decellularization was confirmed by histologic examination and by determining the DNA and solubilized protein content. The decellularized valve showed no significant differences in its mechanical strength or collagen content compared with native porcine tissues. The ultrastructure was well preserved in transmission electron microscope images. The DNA sequence of a porcine endogenous retrovirus and the alpha-1.3 galactosyl epitope were eliminated after the decellularizing process. No acute rejection and little calcification was noted in the rat model. In the dog model at 2 months, the surface of the graft was completely covered with a monolayer of endothelial cells. In addition, several layers of vimentin-positive cells lay under the endothelial cells. At 6 months after implantation, many smooth muscle cells, monolayer endothelial cells, and some vasculogenesis were seen.


CONCLUSIONS
The decellularizing method provided low immunogenicity, low risk of unknown infections, and was little subject to calcification. The decellularized tissues showed acceptable durability and recellularization.
Ota
Takeyoshi
T
Department of Cardiovascular Surgery, Kobe University Graduate School of Medicine, Kobe, Japan. toota-cvs@umin.ac.jp
Taketani
Satoshi
S
Iwai
Shigemitsu
S
Miyagawa
Shuji
S
Furuta
Masakazu
M
Hara
Masayuki
M
Uchimura
Eiichiro
E
Okita
Yutaka
Y
Sawa
Yoshiki
Y
D000818:Animals; D001021:Aortic Valve / Q000166:cytology / Q000528:radiation effects; D001705:Bioprosthesis; D002465:Cell Movement / Q000187:drug effects; D004195:Disease Models, Animal; D004285:Dogs; D005720:Gamma Rays; D006349:Heart Valve Diseases / Q000601:surgery*; D019918:Heart Valve Prosthesis Implantation / Q000379:methods*; D046529:Microscopy, Electron, Transmission; D011092:Polyethylene Glycols / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011474:Prosthesis Design; D051381:Rats; D012680:Sensitivity and Specificity; D013552:Swine; D023822:Tissue Engineering / Q000379:methods*
D011092:Polyethylene Glycols