O-271: Evaluation of metaphase II spindle length, retardance and its relationship to embryo quality on day 3 and day 5

Abstract

Recent studies suggest a relationship between meiotic spindle retardance and embryo development. The aim of this study is to determine if meiotic spindle retardance in metaphase II human oocytes, as viewed by the Oosight, are effective predictors of embryo development. This study was conducted in a prospective randomized way. This study was approved by Sterling Institutional Review Board (Atlanta, GA). Twenty-six patients who elected for intracytoplasmic sperm injection (ICSI) insemination were also consented for this study. Patients must have >9 mature eggs at retrieval. For each patient, half the mature eggs designated for ICSI will be viewed with Oosight, a polarized light microscope designed to view the spindle apparatus. After egg retrieval, the selected oocyte was viewed under the Oosight. The length and retardance of the entire meiotic spindle was measured with the Oosight. Retardance refers to the amount of microtubules present within the spindle. Embryos were graded on day 3 and day 5, taking into account cell number, cell size, fragmentation, and multinucleation. Embryos with a grade of “A” were considered excellent while embryos with a grade of “D” were considered poor quality. Statistical analysis was done utilizing either the unpaired t-test or chi square statistical test. P>0.05 was considered significant. Fertilization was compromised when there was no spindle present (spindle present: 109 of 126 fertilized; spindle absent: 10 of 17 fertilized; P=0.0099). On day 3 however there was no difference in embryo quality when no spindle was detected (present: #A=50, #B=32, #C=11,#D=5; absent: #A=7, #B=3, #C=0, #D=0; P=0.5180). A total of 78 embryos developed to day 3. Of those, 36 were of “A” quality, 28 were of “B” quality, 9 were of “C” quality, and 5 were of “D” quality. No significance difference between spindle retardance levels and embryo quality was seen (A = 1.66 ± 0.33, B = 1.62 ± 0.50, C = 1.55 ± 0.49, D =1.44 ± 0.42; P=0.4636). There was a significant difference in embryo quality on day 3 and length of the meiotic spindle (A = 6.89 ± 1.78 μm, B = 7.69 ± 2.49 μm, C = 8.55 ± 1.74 μm, D = 6.27 ± 1.83 μm). Of the 78 embryos on day 3, 65 went on to day 5. Of those 65, 4 were of “A” quality, 14 were “B” quality, 23 were “C” quality, and 24 were “D” quality. No significance difference between spindle retardance levels and blastocysts quality was seen (A = 1.69 ± 0.48, B =1.59 ± 0.39, C = 1.68 ± 0.26, D = 1.68 ± 0.52; P=0.9044). Lastly, there was a trend, however no significance in meiotic spindle length and blastocysts quality (A = 7.0 ± 1.2 μm, B = 6.2 ± 1.7 μm, C = 7.1 ± 1.2 μm, D = 7.3 ± 1.1 μm; P=0.0739). The Oosight is effective at viewing the meiotic spindle. In our study, the presence of a spindle was a good indicator of fertilization, but contrary to other studies, it was not an indicator of subsequent embryo quality. The retardance level of the metaphase II spindle is poor predictor of embryo quality on day 3 and blastocyst quality on day 5. However, spindle length, as measured by the Oosight, correlates to embryo quality on day 3 and blastocyst quality on day 5.