Claudio Manna (Italy)

Objective assessment of oocyte quality is actually an important matter of investigation in assisted reproduction technology (ART) because of bioethical reasons, improvement of oocyte freezing-thawing techniques and limited predectivity of embryo score systems (1).

Morphological oocyte evaluations are still the standard for routine work in intracytoplasmic sperm injection (ICSI) (2), though they are highly subjective. It was demonstrated that morphological evaluation before ICSI helps to identify metaphase II (MII) oocytes with higher developmental potential (3).

New methodologies, including polar body diagnosis (PBD) (4), metabolomics (5), polarization light microscopy (6; 7; 8; 9; 10)  and  pattern recognition of  processed images by special algorithms (11), have been proposed as methods to improve the objective selection of good quality oocytes.

In particular, the PolScope was used in a semiquantitative mode to evaluate the birefringence of the zona pellucida (ZP) (12) and the meiotic spindle (SP) of the metaphase II oocytes (7).

High zona pellucida birefringence (HZB) has been associated with a significant higher rate of embryo implantation and development to term in comparison to low zona pellucida birefringence (LZB) (9; 10). Oocytes with high fertilization rate show in general a birefringent SP (7; 10). Therefore there is a broad agreement that the analysis of ZP and SP birefringence represents a reliable objective criterion for good quality oocyte selection.

Also our laboratory observed the same results with polarized light microscopy and for this reason we consider the birefringence an objective way to evaluate the oocyte quality.

Bibliografy:

1. De Santis, L., Cino, I., Coticchio, G., Fusi, F.M., Papaleo, E., Rabellotti, E., Brigante, C., Borini, A., Ferrari, A., 2007. Objective evaluation of the viability of cryopreserved oocytes. Reprod. Biomed. Online. 15(3), 338-45.
2.  Serhal, P.F., Ranieri, D.M., Kinis, A., Marchant, S., Davies, M., Khadum, I.M., 1997. Oocyte morphology predicts outcome of intracytoplasmic sperm injection. Hum. Reprod. 12, 1267–1270.
3. Rienzi, L., Ubaldi, F.M., Iacobelli, M., Minasi, M.G., Romano, S., Ferrero, S., Sapienza, F., Baroni, E., Litwicka, K., Greco, E., 2008. Significance of metaphase II human oocyte morphology on ICSI outcome. Fertil Steril. 90, 1692-700.
4. Verlinsky, Y,, Ginsberg, N,, Lifchez, A., Valle, J., Moise, J., Strom, C.M., 1990. Analysis of the first polar body: preconception genetic diagnosis. Hum. Reprod. 5(7), 826-9.
5. Patrizio, P., Fragouli, E., Bianchi, V., Borini, A. and Wells, D., 2007. Molecular methods for selection of the ideal oocyte. Reprod. Biomed. Online. 15, 346-353.
6. Oldenbourg, R., 1996. A new view on polarized microscopy. Nature 381, 175–2008.
7. Wang, W.H., Meng, L., Hackett, R.J., Keefe, D.L., 2001. Developmental ability of human oocytes with or without birefringent spindles imaged by Polscope before insemination. Hum. Reprod. 16(7), 1464-68.
8. Rama Raju, G.A., Prakash, G.J., Krishna, K.M., Madan, K., 2007. Meiotic spindle and zona pellucida characteristics as predictors of embryonic development: a preliminary study using PolScope imaging. Reprod. Biomed. Online. 14(2), 166-174.
9. Montag, M., Schimming, T., Koster, M., Zhou, C., Dorn, C., Rosing, B., van der Ven, H., van der Ven, K., 2007. Oocyte zona birefringence intensity is associated with embryonic implantation potential in ICSI cycles. Reprod. Biomed. Online. 16, 239-244.
10. Madaschi, C., Aoki. T., Paes de Almeida Ferreira Braga, D., de Cassia Savio Figueira, R., Semiao Francisco, L., Iaconelli, A.J., Borges, E.J. 2009. Zona pellucida birefringence score and meiotic spindle visualization in relation to embryo development and ICSI outcomes. Reprod. Biomed. Online. 18, 681-686.
11. Manna, C., Patrizi, G., Rahmanm, A., Sallam, H., 2004. Experimental results on the recognition of embryos in human assisted reproduction. Reprod. Biomed. Online. 8, 460-9.
12. Keefe, D., Tran, P., Pellegrini, C., Oldenbourg, R., 1997. Polarized light microscopy and digital image processing identify a multilaminar structure of the hamster zona pellucida. Hum. Repr. 12, 1250-1252.