Vitrification Carriers and European Regulation

6 03 2012

To the Editor:

We read with interest the recent article by Valbuena et al. (1) comparing the efficiency of Cryotip vs. Cryotop for blastomere vitrification. The authors concluded that it is preferable to preserve individual human blastomeres using Cryotip, which is a closed system. Furthermore, they suggest that this has the advantage of complying with European Union directives.

We would like to point out that European Union directives on tissue manipulation (European Union Tissues and Cells Directive EUTCD: 2004/23/EC, 2006/17/EC and 2006/86/EC) have been issued by the European Parliament in order to increase the safety and quality of tissues – including reproductive cells – processed for human re-implantation through the control of equipment, devices and environment. These regulations require specific procedures in embryo/oocyte/ovarian tissue cryopreservation in order to minimize the risk of any hypothetical contamination of human cells due to direct contact with accidentally contaminated liquid nitrogen (LN2).

Nevertheless, in these directives there are no specific indications against direct contact between tissue/cells and LN2; for this reason Cryotop and any other open system can also comply with European Union directives, as long as aseptic procedures during vitrification-cryostorage-warming are established (2, 3). Furthermore, single-straw closed systems like Cryotip have the same risk of hypothetical contamination as open systems. In fact, while these closed carriers avoid direct contact between cells and LN2, they cannot avoid the transmission of microorganisms in the culture medium during the warming procedure due to the previous direct contact during vitrification between the external surface of the carrier and the accidentally contaminated LN2 (2).

Although the risk of contamination during cryopreservation remains negligible (4,5), we can confidently choose the type of carrier (open or closed) best suited to our purposes in the knowledge that, when aseptic procedures are followed, both systems conform in equal measure to EU directives.

Lodovico Parmegiani M.Sc., Graciela Estela Cognigni M.D., and Marco Filicori M.D.
Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy

L.P. holds an international patent: Device and method for sterilizing liquid nitrogen by ultraviolet
Radiation. G.E.C. has nothing to disclose. M.F. has nothing to disclose.

REFERENCES

1. Valbuena D, Póo ME, Aguilar-Gallardo C, Martinez S, Cobo AC, Pellicer A, Simón C. Comparison of Cryotip vs. Cryotop for mouse and human blastomere vitrification. Fertil Steril 2012;97:209-217.
2. Parmegiani L, Cognigni GE, Bernardi S, Cuomo S, Ciampaglia W, Infante FE, Tabarelli de Fatis C, Arnone A, Maccarini AM, Filicori M. Efficiency of aseptic open vitrification and hermetical cryostorage of human oocytes. Reprod Biomed Online 2011;23:505-512.
3. Parmegiani L, Rienzi L. Hermetical goblets for cryostorage of human vitrified specimens Hum Reprod 2011;26:3204-3205.
4. Pomeroy KO, Harris S, Conaghan J, Papadakis M, Centola G, Basuray R, Battaglia D. Storage of cryopreserved reproductive tissues: evidence that cross-contamination of infectious agents is a negligible risk. Fertil Steril 2010;94:1181-1188.
5. Bielanski A. A review of the risk of contamination of semen and embryos during cryopreservation and measures to limit cross-contamination during banking to prevent disease transmission in ET practices. Theriogenology 2012;77:467-482.

Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2011.12.053

The authors respond:

We have read the lettter to the editor by Parmegiani et al. entitled Vitrification carriers and European Regulation referring to our recent article by Valbuena et al. (1). In our work, we have compared open versus closed system for mice and human blastomere vitrification and conclude that closed system is more efficient in terms of blastomere survival and division.

The main objective and interest of our work was the scientific demonstration of the optimal system for blastomere cryopreservation, and not the discussion about the interpretation of EU directives on tissue manipulation. This topic is more suitable for an opinion debate rather than in a scientific paper.

Diana Valbuena, M.D., Ph.D.
Valencia Stem Cell Bank, Centro de Investigacion Príncipe Felipe
and
Carlos Simon, M.D., Ph.D.
Valencia Stem Cell Bank, Centro de Investigacion Príncipe Felipe
Instituto Valenciano de Infertilidad Foundation
Instituto Valenciano de Infertilidad
Department of Pediatrics, Obstetrics and Gynecology, Valencia University
Valencia, Spain

Reference

(1) Valbuena D, Póo ME, Aguilar-Gallardo C, Martinez S, Cobo AC, Pellicer A, Simón C. Comparison of Cryotip vs. Cryotop for mouse and human blastomere vitrification. Fertil Steril 2012;97:209-217.

Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2011.12.053

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