Maria
Teresa Zenzes1, Ryszard Bielecki1, Jim Meriano2,
S.P. Leibo3, Robert F. Casper1.
1 Dept. of Obs./Gyn., U. of Toronto,
2 Toronto Center for Advanced Reproductive Technology,
3 Dept. of Biomedical Sciences, U. of Guelph, Ontario, Canada.
Objective: To determine the status of meiotic spindles
and metaphase II chromosomes in cytochemical preparations of oocytes
mature in vitro from women in IVF-ET therapy.
Design: Prospective study of patients in
a private clinic setting. Oocytes in G.V. stage which showed after
24 or 48 hr. in culture in the second polar body, were analyzed
for meiotic spindle quality and spindle alignment of MII chromosomes.
Materials and Methods: Twenty-four women
with ages 29 to 44 years (mean age 32.9) participated and signed
a consent. Women were hyperstimulated with GnRH agonist and hMG,
and 36 hours later their oocytes were aspirated.
Cumulus cells were removed with hyaluronidase. Oocytes remained
in culture in modified HTF medium until visualization of second
polar body (for 24 or 48 hours). Oocytes were then fixed in formaldehyde
treated with polyclonal antibody to a-tubulin, FITC-conjugated secondary
antibody and DAPI to localize chromosomes.
Results: From a total of thirty-nine oocytes,
31% (12) required 24 hr. of culture and 69% (27) require 48 hr.
A proportion of 46% (18) oocytes had (1 to 3) chromosomes misaligned
from the plane of the metaphase plate. No difference in the proportion
of oocytes with misaligned chromosomes was found between the 24
hr and 48 hr. stages of culture.
Conclusions: Chromosome behavior is directly
linked to meiotic spindle kinetics. Spindle assembly in the second
meiotic division is altered in its structure, resulting in displacement
of chromosomes from the spindle plane.
This may lead to oocytes with chromosomal aneuploidies. The high
proportion of abnormal oocytes with displayed chromosomes may be
due to a selected population of women with infertility and a relative
high mean age. The proportion of 46% of oocytes with misaligned
chromosomes, found in this study, is similar to reported cytogenetic
data on oocytes with chromosomal aneuploidies. Supported by the
MRC of Canada. |
