Case Report
Open Access
Giant Oocytes with Two Meiotic Spindles and Two
Polar Bodies: Report of Two Cases
Baris Baykal1*, Cem Korkmaz1, Muhterem Bahçe2, Cihangir Mutlu Ercan1 and Temel
Ceyhan1
1ART Centre, Department of Obstetrics and Gynecology, Gulhane Research and Training
Hospital, University of Health Sciences, Ankara, Turkey.
2MBGENLAB Genetic Diseases Diagnosis Center, Ankara, Turkey.
2MBGENLAB Genetic Diseases Diagnosis Center, Ankara, Turkey.
*Corresponding author: Dr. Baris Baykal, ART Centre, Department of Obstetrics and Gynecology,
Gulhane Research and Training Hospital, University of Health Sciences, Ankara,Turkey; E-mail:
@
Received: May 08, 2017; Accepted: May 22, 2017; Published: May 31, 2017
Citation: Baykal B, Korkmaz C, Bahçe M, Ercan CM, Ceyhan ST (2017) Giant Oocytes with Two Meiotic Spindles and Two Polar Bodies: Report of Two Cases. SOJ Gynecol Obstet Womens Health 3(2):1-3 DOI: http://dx.doi.org/10.15226/2381-2915/3/2/00123
Introduction
With the advent of IVF technology, the terms normal
and abnormal oocytes have been defined and one
type of abnormal oocyte is the “giant oocyte”. Giant
oocytes are defined to have a 30% larger diameter and
twice the volume of normal oocytes[1,2]. Giant oocyte
is a rarery observed phenomenon among humans and
embryos may develop from these oocytes [2,3].The first
hypothesis for the mechanism of their formation is cytoplasmic
fusion of two oogonia and the second one is the
lack of cytokinesis during mitotic divisions in an oogonium
[4]. Fertilization and progression of a giant oocyte
is suspected to be the cause of digynic triploidy, which is
defined as triploidy with two maternal and one paternal
complements [5]. In this case report, we present two
giant oocytes, each shown to have two meiotic spindles
via visualization by polarization microscope. Because
giant oocytes can develop into embryos that are morphologically
normal, but genetically abnormal, an embryologist
has to be aware of this phenomenon. For this
reason, the scientific aim of this report is to present the
polarization microscopic properties of giant oocytes and
increase the awareness of such oocytes among embryologists.
Keywords:Giant oocyte; meiotic spindle; polarization microscopy
Keywords:Giant oocyte; meiotic spindle; polarization microscopy
Case Report
During the ICSI procedure of two patients with the aid of
polarization microscope, we encountered giant oocytes with two
distinct meiotic spindles and two polar bodies.
Figure 1: Giant oocyte retrieved from patient 1. It has two polar
bodies (red and blue arrows).
The first patient was 26 years old and the reason for infertility
was detected to be poor ovarian reserve and male factor
infertility. An antagonist patch protocol was applied using a total
dose of 2400 units of Follitropin-alfa (Gonal-F, Merck Serono,
Germany) and a toal dose of 2400 units of human menopausal gonadotrophin
(Merional, IBSA, Slovakia) for 8 days. Her husband’s
semen was found to be oligoasthenozoospermic (sperm concentration:
2x106/ml; ICSI was performed with motile sperm)
according to World Health Organization guidelines [6]. Five
oocytes were collected, three of which were at MII stage, one
was at MI stage and one was at GV stage. During ICSI proce-dure, we observed that one of the MII oocytes was a giant oocyte
with two polar bodies and a diameter of 143.75 mm (Fig. 1). Visualization
with polarization microscope (Oosight Meta Imaging
System, Cambridge Research and Instrumentation, USA) revealed
two meiotic spindles (Fig. 2). ICSI was performed on this oocyte.
It had 3PN view on day one, 5 blastomeres on day two and 10
blastomeres on day 3 (Fig. 3). Blastomere biopsy was performed
and PGD using FISH method with 7 probes (for chromosomes X,
Y, 13, 14, 16, 18 and 21, revealed triploidy (Fig. 4).
Figure 2: Polarization micrographs of the giant oocyte retrieved
from patient 1. a. First polar body and the first meiotic spindle is
shown by red arrow and red arrow head. The second polar body
and the second meiotic spindle are marked by blue arrow and
blue arrowhead. b. The positions of the polar bodies and meiotic
spindles after rotating the oocyte.
Figure 3: Progression of the giant oocyte of patient 1. a. Day 1;
3PN view. b. Day 2; the embryo has 5 blastomeres. c. Day 3; the
embryo has 10 blastomeres.
The other patient was 31 years old and she had endometriosis.
An ultralong protocol was applied. Her husband’s semen
analysis report was found to be normozoospermic (sperm concentration:
100x106/ml; progressive motility: 75%) according
to World Health Organization guidelines [6]. Sixteen oocytes (15
MII and 1 MI stage) were collected. During ICSI procedure a giant
oocyte with two polar bodies was encountered (Fig 5). Visualization
with polarization microscope revealed two meiotic spindles
both at telophase I stage (Fig 6). ICSI was performed, but no progression
was observed.
Figure 4: Fluorescent micrograph of the embryo that originated
from the giant oocyte of patient 1. Green signals refer to chromosome
14 and red signals refer to chromosome 16.
Discussion
Our case report and the studies by other researchers prove
that giant oocytes at different stages of maturation can be retrieved
in human IVF cycles. The giant oocyte of patient 2 in our
case also demostrates that even being evaluated as a MII stage
oocyte under phase contrast optics, an oocyte can still be determined
to be immature (telophase I stage) under polarization optics.
Giant oocytes can become fertilized and as reported by Rosenbusch et al., they result in triploid zygotes after monospermic fertilization even if they have 2 PN on day 1 [2]. The giant oocyte of patient 1 in our case report got fertilized with 3 PN and developed into a 10 blastomere embryo on day 3. PGD revealed triploidy.
The diameters of the giant oocytes in our cases were 146.88 mm and 143.75 mm when measured without zona pellucida. Balakier et al. have reported the mean diameter of giant human oocytes as 147.73 mm when measured without zona pellucida [1].
Mahadevan et al. are the first to report the recovery of a binucleated oocyte after ovarian stimulation. They proposed its formation by fusion of two adjacent oocytes [7]. Because they did not specify the size of the oocyte, we can not be sure whether it was a giant oocyte. Rosenbusch et al. have reported that all binucleate GV stage oocytes in their IVF programme have matured into giant oocytes. They have also stated that they constantly detected diploidy in giant oocytes [2]. A morphologically giant oocyte, which had two chromosome sets each accompanied by its own polar body chromosomes has been described by Angell et al. [8]. Our polarization micrograph of the giant oocyte of patient 2 also verifies this finding.
Giant oocytes can become fertilized and as reported by Rosenbusch et al., they result in triploid zygotes after monospermic fertilization even if they have 2 PN on day 1 [2]. The giant oocyte of patient 1 in our case report got fertilized with 3 PN and developed into a 10 blastomere embryo on day 3. PGD revealed triploidy.
The diameters of the giant oocytes in our cases were 146.88 mm and 143.75 mm when measured without zona pellucida. Balakier et al. have reported the mean diameter of giant human oocytes as 147.73 mm when measured without zona pellucida [1].
Mahadevan et al. are the first to report the recovery of a binucleated oocyte after ovarian stimulation. They proposed its formation by fusion of two adjacent oocytes [7]. Because they did not specify the size of the oocyte, we can not be sure whether it was a giant oocyte. Rosenbusch et al. have reported that all binucleate GV stage oocytes in their IVF programme have matured into giant oocytes. They have also stated that they constantly detected diploidy in giant oocytes [2]. A morphologically giant oocyte, which had two chromosome sets each accompanied by its own polar body chromosomes has been described by Angell et al. [8]. Our polarization micrograph of the giant oocyte of patient 2 also verifies this finding.
Figure 5: The giant oocyte retrieved from patient 2. Arrows point
to the two polar bodies.
Figure 6: Polarization view of the giant oocyte from patient 2.
The two spindles are at telophase I stage (arrows).
Conclusion
Giant oocytes are rarely observed in humans. They can get
fertilized and develop into morphologically high quality embryos.The findings in this case report reveal that embryos derived from
giant oocytes may be triploidic. Visualization with polarization
microscope reveals two meiotic spindles. Based on the findings
in this case reports, transfer of the embryos derived from giant
oocytes should only be considered after PGD.
ReferencesTop
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