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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Yutaka Okita Yoshiki Sawa Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ota, T. Articles by Sawa, Y. Search for Related Content PubMed Articles by Ota, T. Articles by Sawa, Y. Related Collections Cardiac - other Valve disease Related Article

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Correspondence

Reply

^a Department of Cardiovascular Surgery, Kobe University Graduate School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
^b Department of Surgery (E1), Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan

(Email: toota-cvs{at}umin.ac.jp; sawa{at}surg1.med.osaka-u.ac.jp).

To the Editor:

We appreciate the comments by Drs Dohmen and Konertz [1] on our article [2] and for giving us an opportunity to describe further the explanation of our study.

Gamma irradiation played an important role in our decellularization process. The original purpose for use of gamma irradiation was to remove the cell components from the porcine aortic valves in conjunction with polyethylene glycol (PEG). Because the radiation effect can reach the entire tissue evenly, it contributed to complete decellularization of such porcine aortic valves that had complex structures (eg, variety of tissue thickness). Gamma irradiation also brought supplemental benefits to our decellularized tissue, such as elimination of both the DNA sequence of porcine endogenous retrovirus and 1.3-galactosyl epitope (ie, they could be the sources of infection or rejection, or both), and the possible reinforcement effect due to polymerization of PEG by gamma irradiation, as described in our article [2]. Therefore, Dohmen and Konertz's [1] comment that "gamma irradiation was not used to decellularize but to sterilize the decellularized scaffold" is definitely incorrect. Although it is true that decellularized tissues get sterilized through our process with 100 kGy gamma irradiation, it is of limited significance in our study. On the other hand, we agree with their comments that we need further studies on hemodynamic functional evaluations and long-term impact of gamma irradiation, which were described as limitations in our article [2]. However, we believe that it was inappropriate to refer the article by Cohen and colleagues [3] to discuss the use of gamma irradiation and its negative effects, because it had a completely different setting from ours (ie, the homograft).

Regarding the use of DNase, we used it for enhancing removal of debris of nuclei after gamma irradiation. There is no evidence to support Dohmen and Konertz's [1] comment that "deoxyribonuclease also damages and alters the extracellular matrix." Theoretically, any kind of chemical reagents could damage biological tissues to somewhat of an extent. In addition, the article [4] to which Dohmen and Konertz [1] referred to in their letter did not describe anything about what they insisted.

Finally, we were impressed with their excellent decellulalization method and clinical outcomes [5, 6]. However, we believe that mechanical property has to be evaluated only by in vitro mechanical strength studies and by the electron microscope. They should not claim that there was no evidence of extracellular matrix destruction in their decellularized tissue by their clinical articles [6, 7] in which there were no mechanical studies, and the scaffold was implanted only in the right ventricular outflow tract, not even in the left heart (ie, the high blood pressure environment).

	References

Top References

 

1. Dohmen PM, Konertz W. Decellularization of xenogenic biologic tissue Ann Thorac Surg 2008;85:2163(letter).[Free Full Text]
2. Ota T, Taketani S, Iwai S, et al. Novel method of decellularization of porcine valves using polyethylene glycol and gamma irradiation Ann Thorac Surg 2007;83:1501-1507.[Abstract/Free Full Text]
3. Cohen DJ, Myerowitz PD, Young WP, et al. The fate of aortic valve homografts 12 to 17 years after implantation Chest 1988;93:482-484.[Medline]
4. Uchimura E, Sawa Y, Taketani S, et al. New method of preparing acellular cardiovascular grafts by decellularization with poly(ethylene glycol) J Biomed Mater Res A 2003;67:834-837.[Medline]
5. Erdbrügger W, Posner S, Ellerbrock H, et al. Deoxycholic acid treatment offers improved prospects in heart valve replacement Tiss Eng 2006;8:2059-2068.
6. Konertz W, Dohmen PM, Liu J, et al. Hemodynamic characteristics of the Matrix P decellularized xenograft for pulmonary valve replacement during Ross operation J Heart Valve Dis 2005;14:78-81.[Medline]
7. Dohmen PM, da Costa F, Lopes SV, et al. Is there a possibility for a glutaraldehyde-free porcine heart valve to grow? Eur Surg Res 2006;38:54-61.[Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Yutaka Okita Yoshiki Sawa Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ota, T. Articles by Sawa, Y. Search for Related Content PubMed Articles by Ota, T. Articles by Sawa, Y. Related Collections Cardiac - other Valve disease Related Article