Comparative analysis of the metaphase II spindle of human oocytes through polarized light and high-performance confocal microscopy

Objective: To determine whether Polscope analysis can predict different spindle and chromosome configurations of the oocyte metaphase II (MII) spindle. Design: Comparison of Polscope and confocal microscopy analysis of the MII spindle. Setting: Private IVF unit. Patient(s): Women undergoing IVF treatment for male or unexplained infertility. Intervention(s): Fresh and frozen-thawed mature oocytes were analyzed through the Polscope and, immediately afterward, fixed for confocal microscopy assessment. Main Outcome Measure(s): Comparison of retardance values, derived from Polscope analysis, between spindles with different microtubule and chromosome configurations, defined by confocal microscopy evaluation. Measurements of spindle longitudinal axis through the Polscope and confocal microscopy. Result(s): The mean retardance values of different categories of spindle configuration were not statistically significant in almost all cases, allowing only the identification of spindles with highly disorganized microtubules and chromosomes in frozen-thawed oocytes. In spindles with bipolar organization, the Polscope produced measurements of the spindle main axis which were in all cases statistically smaller compared with confocal microscopy evaluation. Conclusion(s): Retardance measurements have limited predictive value of the degree of spindle fiber order and chromosome position in routine clinical settings. Also, under the conditions tested, morphometric evaluation of the spindle through the Polscope is not consistent with confocal analysis. This suggests that the Polscope may still be a rather inefficient method for assessing the metaphase II spindle and, as a result, for noninvasive oocyte selection.