Hum. Reprod. Advance Access published online on October 3, 2008
Human Reproduction, doi:10.1093/humrep/den333
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Letter to the Editor |
Impact of hyperglycemia on early embryo development and embryopathy: in vitro experiments using a mouse model
1 Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115-5730, USA 2 Department of Obstetrics and Gynecology, Division of Reproductive Medicine, University of Massachusetts Medical School, 119 Belmont Street, Worcester, MA 01605, USA
3 Correspondence address. Tel: + 1-617-432-2080; Fax: + 1-617-432-2229; E-mail: john_biggers{at}hms.harvard.edu
Fraser et al. (2007)
identify the media they used in their work as mKSOM and KSOM, and characterize them as a ‘synthetic oviductal medium enriched with potassium’. We wish to point out that his characterization is erroneous. A medium called SOM was developed by Lawitts and Biggers (1991) using the experimental strategy called ‘sequential simplex optimization’ (hence SOM). SOM medium was not designed to imitate the composition of oviductal secretions. It was developed to overcome the 2-cell block which, at the time, interfered with many studies on the developmental biology of the mouse embryo. KSOM was later modified by raising the potassium concentration in SOM (Lawitts and Biggers, 1993) based on measurements of the intracellular potassium concentration in blastomeres determined by the electron-probe analysis. Since the concentration of potassium in KSOM is considerably lower than the measured levels found in mouse oviductal fluid (Borland et al., 1977), it is misleading to refer to KSOM as potassium-enriched SOM.
Fortuitously, KSOM was also found to be beneficial for the development of the mouse blastocyst (Erbach et al., 1994) and has been modified several times which we have called the KSOM family (see Biggers, 2002 for review). One of these was produced by increasing the concentrations of glucose to 5.56 mmol/l and bovine serum albumin (BSA) to 4 mg/ml in order to support in vitro fertilization in the mouse (Summers et al., 1995). This medium was denoted mKSOM. A second modification is KSOMAA, which is KSOM supplemented with 19 natural amino acids (Ho et al., 1995; Biggers et al., 2000). A third modification, mKSOMAA, which contains high glucose, albumin and the 20 natural amino acids has also been used to support in vitro fertilization (Summers et al., 2000, 2005).
We wish to stress that the abbreviations used by Fraser et al. (2007) are not the same as used by us. They have used mKSOM to mean our KSOM, and KSOM to mean KSOMAA. This type of confusion unfortunately arises frequently in the scientific and clinical literature due to the failure of authors to reference exactly the media they use. Since the constituents of media can have significant, sometimes unpredictable, effects, we urge authors and editors to ensure that the media used be uniquely identified and referenced.
References
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