Greetings from Chennai, India ASPIRE - 2008

II World CongressSingapore

April 11-13,2008

SMOOTH ENDOPLASMIC RETICULUM CLUSTERS AND ICSI OUTCOME

V.Thomas

Chief Embryologist

Dr T R Varma

Medical Director

Institute of Reproductive Medicine

Madras Medical Mission

Chennai, India

Introduction

• Veek (1988) –Good quality MII oocytes should show clear and colourless

cytoplasm with moderate granulation and no inclusions,

a small PVS, and a clear ZP.

• However, more than half of all human oocytes collected show at least one morphological abnormality.

MINOR DYSMORPHISMS • Incorporations or refractile bodies

– unlikely to have any impact on fertilization

rate and embryo quality in ICSI patients

• Whereas Vacuoles or aggregations of smooth

endoplasmic reticulum (SER) will

impair developmental capacity of human oocytes. 

ROLE OF OOCYTE MORPHOLOGY AND ICSI OUTCOME

• Alikani et al 1995,desutter 1996 – oocyte morphology does not affect fertilization and embryoscores.

• Serhal et al 1997,Lourtradis et al 1999 –oocyte morphology does have impact on implatation and clinical pregnancy rates.

• Balaban et al 1998 – no influence of oocyte morphology on clinical pregnancy rates.

SERC

• What is SERC?• How common is it?- ( 9-13%)• Why does it happen ?– not known, possibly

duration of gonadotrophins (Otsuki et al 2004) Evidence of its effect on fertilization, cleavage

and pregnancy rates ?• 2004 Otsuki et al – The presence of SERC is

associated with normal fertilization and cleavage but lower clinical pregnancy rates.

SERC – Literature Review

• There are very few studies published in literature on SERC and ICSI outcome.

• Otsuki et al 2004 – The presence of SERC is associated with normal fertilization and cleavage but lower clinical pregnancy rates.

• Ebner et al 2008 – found lower fertilization and cleavage rates and lower pregnancy rates in women with SERC positive oocytes.

The role of Smooth endoplasmic reticulum

• It increases surface area for the action or storage of

key enzymes (eg: Glucose 6 phoaphatase )

• It serves as a store of calcium and acts as a detoxifier• In the oocyte it has a key role in regulating calcium

influx during fertilization.

ER Cluster Formation Is Related to Cell Cycle

• The development of the ER clusters on the vegetal side is observed during maturation. Small clusters first appear at time of germinal vesicle breakdown.

• The clusters disappear and then reappear by the

time of second meiotic metaphase arrest as large clusters.

• The timing suggests that small clusters appear during meiosis I metaphase and disappear during first polar body formation, perhaps at anaphase, and then large clusters appear during meiosis II metaphase. (De Sutter et al., 1996; Balaban et al., 1998; Ebner et al.,2001).

• Fundamental changes occur in Ca2+ physiology during ovum maturation

• Central physiological event at fertilization is an intracellular Ca2+ wave that begins at the sperm entry site (Stricker, 1999)

• Ca2+ is released from internal membrane stores, THE ENDOPLASMIC

RETICULUM (ER)• Changes in the structure &

redistribution of the ER

Smooth Endoplasmic Reticulum clusters (SERC)

• The Ca2+ source in SERC is altered leading to abnormal oocyte maturation and Ca2+ signalling for embryonic development.

• Mechanisms responsible for SER clusters are unknown.

• SERCs in human oocytes require future studies at the molecular level.

Oocyte – Cytoplasmic abnormalities

Oocyte with normal cytoplasm Oocyte with granular cytoplasm Oocyte with big vacuole

Oocyte with Refractile body Oocyte with small vacuole Oocyte with SERC

M II – Oocyte with SER Clusters M II – Oocyte with vacuole

Vacuoles are membrane boundCytoplasmic inclusions filled with Fluid-derived from SER or golgiApparatus.

High E2 concentration on the dayOf HCG may be one of the reason for SERC formation

SERC & ICSI

t-SERt-SERv-SERv-SER

Smooth endoplasmic reticulum

Courtesy of Prof. Azumaya

Plenty of tubular and vesicular smooth ER showed active synthesis of proteins in ooplasma.

SERC

Smooth EndoplasmicReticulum clusters

Courtesy of Dr.Otsuki

Our study

• Type of Study: Retrospective analysis

Materials and Methods:• ICSI outcome of 510 patients• 53 had oocytes with SERC• We looked at proportion of oocytes with SERC• Fertilization , cleavage, embryo grade and clinical

pregnancy rates.• These were compared to patients without SERC in

their oocytes.

Results• Incidence of SERC in our study – 13%

SERC (+) SERC (-) P-value

Fertilization : 86% 84% NS

Cleavage 94% 96% NS

Embryo grade (A+B)

65% 68% NS

Pregnancy Rate 32% 67% P<0.05

Ongoing Pregnancy 9.3% 55% P<0.05

Biochemical 22.7% 6.8% P<0.05

Missed Abortion 1.9% 1.7% NS

0

10

20

30

40

50

60

70

SERC + SERC -

PREGNANCYONGOINGBIOCHEMMISSED

32%

22%

9%

2%

67%

55%

7%1.7%

SERC & ICSI OUTCOME

Conclusion• SERC adversely affects clinical pregnancy rates

following ICSI. • Fertilization , cleavage and embryo grade are not

affected.• Even small proportionate of oocytes with SERC in a

cohort may have an overall negative prognosis.• This is probably because smaller SERCs cannot be

seen at standard magnifications (40X) which we use for ICSI.

• High estradiol levels could be one of the cause of SERC formation.

• Our results are similar to those of otsuki et al (2004).

Acknowledgment

Medical Team

Thangam Varma PhD

Sathya MD

Shalu Gupta MD

Betty MD

Research Team

Stephen MS

Hema MS