Release of superoxide dismutase-1 by day 3 embryos of varying quality and implantation potential

Abstract

Purpose: To determine if the antioxidant superoxide dismutase-1 (SOD1 or Cu,Zn-SOD) is released by cultured human cleavage-stage embryos and to assess any link between SOD1 and implantation potential.

Methods: Women (n = 91; ≤40 years old) undergoing IVF treatment with transfer of one or two 8-cell embryos that resulted in 0 or 100% implantation were included. Following individual embryo culture, spent medium samples (n = 122) were collected and levels of SOD1 protein were measured by an enzyme-linked immunosorbent assay. SOD1 detection and concentration in embryo spent medium were analyzed in relation to embryo fragmentation and symmetry scores, and implantation (viable fetus at >12 weeks).

Results: Cleavage-stage embryos release SOD1 protein into the spent culture medium. Neither detection nor concentration of SOD1 was related to implantation. There was a positive relationship between increased embryo fragmentation scores and SOD1 release, with no apparent association with symmetry. In non-pregnant cycles, the release of SOD1 decreased with increasing maternal age.

Conclusions: While SOD1 does not predict implantation potential of select good-quality embryos, our data support the need to evaluate the biological significance of released SOD1 by embryos of varying quality and from patients of varying age.

Fig. 1

Spent medium SOD1 concentrations according to pregnancy outcome (a; no pregnancy, n = 25; pregnancy, n = 18) and fragmentation scores (b; 0, n = 12; 1, n = 25; 2, n = 11) of hyc=10?>8-cell embryos. Boxes show the 25th and 75th percentile of the data, with the 50th percentile (median) depicted by the central line. Bars extending from the box indicate the full range of the data, and circles represent data outliers. In (B), the asterisk denotes a significant difference (p = 0.018, One-Way ANOVA)

Fig. 2

Spent medium SOD1 concentrations in relation to patient age for non-pregnant (a, n = 70) and pregnant (b, n = 52) cycles. In (A), there is a significant negative correlation between SOD1 and patient age (Pearson’s r = -0.293, p = 0.014). Shown are the best fitting lines for the data. Note that a single circle may reflect the SOD1 concentration for more than one sample; there was no difference in the distribution of samples across the range of patient ages