To the Editor:
We read the paper of Biggers and Summers (1) and followed the never-ending scientific discussion (or should we say, dispute) on the optimal composition of culture media (2,3) with interest.
Critically analyzing the above-mentioned debate (1-3), the reader cannot help but think that the path of objective discussion has been left and that the argument got personal. Undoubtedly, both authors have provided substantial contributions to the composition of culture media; however, discussion should be objective and factual. Although we regularly use global media and our experience is more in line with Biggers et al. (1, 2), we would like to point out some flaws in the present paper (1).
To begin with, the statement that “all but one commercially available protocols for the culture of human preimplantation embryos to the blastocyst stage are of the sequential media type” is rather incorrect. At least one alternative global medium called GM501 (Gynemed, Lensahn, Germany) has been marketed for 5 years and is frequently used in Central Europe and Asia (4); hence, Table 1 should be adapted accordingly.
Secondly, it is questionable to argue exclusively on the basis of preliminary data. The abstracts listed in Table 2 had not been peer-reviewed and, thus, are of limited value in this context. Although this limitation has been mentioned by the authors (1) and one paper has in the meantime been published as an original article (5), a strange aftertaste is left since it took these authors (5) almost 3 years to publish their data, which, by the way, are not consistent with the data from the corresponding abstract submitted earlier (1). Interestingly, some co-authors have been deleted from the original list of authors, probably because of conflicting interests.
Last, but not least, the authors (1) mentioned “difficulties in the interpretation of clinical outcomes due to the heterogeneous nature of the IVF patient population;” however, they completely neglected in vitro culture conditions. Different volumes of culture medium and embryo densities within this volume do not allow for comparison of blastulation rates or pregnancy rates.
To conclude, we are convinced that both strategies of culturing zygotes up to blastocyst stage have roles in IVF laboratories. In the current situation of competing concepts, parallel usage of both types of media on sibling gametes and embryos is recommended, which would help to reduce dependence on brand names and batch numbers.
Paul A. Ebert, B.Sc.
Karl Völklein, M.D.
Fertility Center Bielefeld
1. Biggers, JD, Summers MC. Choosing a culture medium: making informed choices. Fertil Steril 2008; 90: 473-83.
2. Biggers JD, McGinnis LK, Lawitts JA. One-step versus two-step culture of mouse preimplantation embryos: is there a difference? Hum Reprod 2005; 20: 3376-84.
3. Gardner DK, Lane M. One-step versus two-step culture of mouse preimplantation embryos. Hum Reprod 2006; 21: 1935-6.
4. Ebert P, Szypajlo B, Tomalak K, Völklein K. Prospective comparison of two commercially available culture media under the provisions of the German embryo protection law. J Turkish-German Gynecol Assoc 2009; 10: 10-3.
5. Sepúlveda S, Garcia J, Arriaga E, Diaz J, Noriega-Portella L, Noriega-Hoces L. In vitro development and pregnancy outcomes for human embryos in either a single medium or in a sequential media system. Fertil Steril 2009, 91: 1765-70.
Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2009.12.048
The Authors Respond:
We thank Ebert and Völklein for drawing our attention to Medium GM501 marketed by Gynemed (Lensahn, Germany). We were not aware at the time of writing our review referred to in their letter of any peer-reviewed, journal papers describing the use of Medium GM501 for the extended culture of human preimplantation embryos. The omission of this medium from inclusion in Table 1 is thus understandable, and not a flaw which the authors suggest in their letter. Moreover, the paper by Ebert et al. (1) was published after our review article appeared. Their paper focuses on the culture and clinical outcome following the transfer of cleavage-stage human embryos, and thus is not germane to the principle purpose of our review article on culturing human embryos from the zygote to the blastocyst.
Reportedly, Medium GM501 has been successfully used for the culture of human zygotes to the blastocyst stage using a single-step protocol. These findings are not published in a peer-review journal, but appear, along with a detailed history of GM501 by Weiss and Schneider in Gynemedia, an undated Company newsletter. This medium, like Global marketed by IVFOnline, is a derivative of medium KSOMAA, designed originally for use in the mouse, and used for the culture of human preimplantation embryos by Biggers and Racowsky (2).
The authors seem to have doubts about the scientific value of the summary of abstracts listed in our Table 2 since they are not peer reviewed. We felt that there was sufficient agreement between the abstracts, to warrant the suggestion that serious consideration be given to the use of single-step protocols. It is indeed gratifying that our suggestions have been justified by the subsequent publication of two full length, peer reviewed papers supporting the efficaciousness of single-step protocols for the culture of human preimplantation embryos (3,4).
We wish to make a correction to a mistake made in our review with respect to the abstract by Sepúlveda et al. (5) and the paper by Sepulveda et al. put online by Fertility and Sterility in 2008 and now in print in 2009 (3). We mistakenly implied that the same data were used in these two studies; rather the two contributions were based on independent sets of data. Thus, the sentence in which Ebert and Völklein question the validity of the work of Sepúlveda et al. is merely unjustified speculation.
Ebert and Völklein quote part of the first sentence of the last paragraph of our review, p.478 , “difficulties in the interpretation of clinical outcomes is the heterogeneous nature of the patient population…”, and then say we ignored the many other variables that exist in the IVF laboratory. Their criticism is not justified. The last part of the paragraph quite plainly addresses the technical variables that occur in the IVF laboratory. Also, it is well-known that valid, unbiased evaluations of media are only obtained when the comparisons are made within clinics using the same culture conditions.
John D Biggers, PhD, D.Sc.a
Michael C. Summers, M.D., Ph.D.b
aDepartment of Cell Biology
Harvard Medical School
bDepartment of Obstetrics and Gynecology
Division of Reproductive Medicine
University of Massachusetts Medical School
1. Ebert P, Szypajlo B, Tomalak K, Völklein K. (2009) Prospective comparison of two commercially available culture media under the provisions of the German embryo protection law. J. Turkish-German Gynecol Assoc 10, 10-3.
2. Biggers JD, Racowsky C (2002) The development of fertilized human ova to the blastocyst stge in medium KSOMAA : is a two-step protocol necessary? Reprod BioMed Online 5, 133-40.
3. Sepúlveda S, Garcia J, Arriaga E, Diaz J, Noriega-Portella L, Noriega-Hoces L. (2009) In vitro development and pregnancy outcomes for human embryos in either a single medium or in a sequential media system. Fertil Steril 91, 1765-70.
4. Reed ML, Hamic A, Thompson DJ, Caperton CL (2009) Continuous uninterrupted single medium culture without medium renewal versus sequential media culture: a sibling embryo study. Fertil Steril 92, 1783-6.
5. Sepúlveda S, Garcia J, Arriaga E., Noriega L, Wierner KE, Rieger D. (2006) Comparison of a single medium with sequential media for culture of sibling human embryos to the blastocyst stage. Proceedings of the 37th Annual Meeting of the Society for Reproductive Biology, Queensland, Australia.
Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2009.12.047