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Transcript
New Technologies in the IVF
lab.for embryo selection
Basak Balaban
Head of IVF Laboratory
VKF American Hospital
AMERICAN
HOSPITAL
TJOD 2014
Future of ART Lab. applications?
OVERVIEW
• There are two main important items that needs to be improved in IVF
laboratory applications in the future for maximum clinical efficiency
1.
İdeal culture for gametes & embryos. Keeping the cell viability as equal to in-vivo
2.
Selection techniques for the best viable gamete & embryo that would lead to
highest implantation potential is required. Predictive value of morphologically
selection is limited, therefore more objective selection techniques are being
studied
A. Biomarkers for oocyte/embryo selection
*** Measurement of uptake and secretion of single or specific molecules in the
culture medium
*** Omics technologies (Genomics, Transcriptomics, Metabolomics, Proteomics),
*** Microfluidics with combined omics technology
*** Monitorization systems for examining the embryo development more dynamicaly
than morphological evaluation
*** Birefrigence imaging of oocytes
Current Embryo Assessment Strategies
based on Morphology
• Association between the morphology and
quality/viability of human embryos has been
established early during the development of IVF
(Edwards 1984)
• Even after 30 years assessment of in-vitro grown
embryos is performed largely based on
morphology.
• Although the currently used embryo assessment
strategies have been useful in increasing
pregnancy rates, and decreasing multiple
pregnancies , their accuracy is still far from ideal
Aydıner et al., Cur.Mol.Med. 2010
Standardized Grading Sheme for Morphological Assessment of Embryos
The phases of new techniques
Phase 1: Introduction (e.g. Initial publication)
Phase 2: Validating (e.g. RCT)
Phase 3: Long term use and validation
(longditutional studies)
More objective biomarkers for gamete/embryo selection???
Measurement of specific molecules secreted within the culture environment of the embryo,
Objective biomarker for gamete/embryo viability?
+ F&S 2011 Tejera E quality & IR
These investigational approaches are all based on the hypothesis that ̋ an embryo that results
in a pregnancy alters its environment differently compared to a non-viable embryo ̏
Aydıner et al., Cur.Mol.Med. 2010
• Soluble Human Leukocyte Antigen-G(sHLA-G)
•
•
•
HLA-G molecule may play a role in immune tolerance in pregnancy, being expressed in the plasenta .
Both membrane and soluble forms (sHLA-G) are identified, possibilly sHLA-G having the role of
protecting the developing embryo from the maternal immune system. This led the detection of
HLA-G mRNA expression in oocytes & embryos, and a positive correlation was found between
embryonic HLA-G mRNA expression and pregnancy (Jurisicova 1996)
It’s suggested that there’s a positive correlation between sHLA-G in the culture media (measured by
ELISA) and increased embryo viability and improved pregnancy rates
Vercammen 2008, HR Update Meta-Analysis of 11 studies/1813 patients
sHLA-G in embryo culture supernatants is moderately helpful to predict the ability to achieve a
pregnancy in women undergoing infertility treatment. If the embryos are of good quality, however,
sHLA-G has a much better diagnostic performance. Our findings underscore the need to address the
critically important issues related to single-embryo transfer, single culture condition, and sHLA-G
detection threshold
•
Leptin
•
Secretion of leptin, a small pleitropic peptide linked to food consumption and energy balance,
measured in the spent embryo culture medium had shown a positive correlation with blastocyst
development
***Both methods are technicially challenging and not practical for a clinical setting
G-CSF-Granulocyte colony-stimulating factor
• Plays an important role in early cross talk between mother and conceptus
• Regulates reproductive processes at different times during women’s reproductive life
Leede HR 2008, J Reprod. Imm. 2010, F&S 2011
Ledee et al., HR 2013
OMICS Technologies
• Novel technologies that allow simultaneous profiling of multiple
markers (measured from secreted and consumed components within
culture medium) of embryonic phenotype
•
•
•
•
Genomics (requires embryo biopsy-Invasive)
Transciptomics (requires embryo biopsy-Invasive)
Proteomics
Metabolomics
• Most of the techniques are invasive, technically challenging, and time
consuming, and require agents such as radioactive probes or fluorescent
dyes, making them unsuitable for assessment of embryo viability in a
clinical setting
• Taking into account the complexity and diversity of the human embryo, it
would seem reasonable to envisage a combined omics contribution to the
characterization of the human embryonic secretome
Nagy et al., RBM Online 2008
Katz et al., MHR 2009
Transcriptomics
• Transciptome: All transcribed elements, regardless of whether
they are protein-coding sequences or not
• Transcriptomics: Microarray analysis through RNA for
investigation of gene expression in oocytes and embryos
• Small RNA molecules such as microRNAs are isolated and
processed. Main focus of transcriptomics is directed at proteinencoding RNAs (mRNA)
• Aside from mRNAs,RNA subtypes involved in the maturation
process of mRNAs and rRNAs , respectively localized in the
nucleus (small nuclear RNAs)and in the nucleolus (small nucleolar
RNAs) are important components of transcriptomics
• Proportion of mRNAs in a transcriptome account for only 1-2% of
total RNA content in somatic cells
Proteomics
• Entire complement of proteins expressed by a single embryo at a
given time is called the embryonic proteome, and it’s study is
proteomics. Since this is related with gene expression, it can give
insight into cellular health and viability.
• The secretome is the subset of proteins that are exported from
the cell in which build up the culture environment
• Changes in protein profiles were detected between embryos of
different developmental stages, as well as between embryos that
progressed versus those arrested. (Katz-Jaffe 2008)
• Despite new advances in proteomic techs.,knowledge of the
proteome of the mammalian preimplantation embryo remains
limited. The combined effect of limited template, low protein
expression and the lack of sensitivity of proteomic platforms are
the main hurdles
Vergouw et al., HR 2012 had also shown no beneficial effect in addition to morphology
Genomics
• Studying the DNA constitution/sequence of cells
• DNA determines the sequence of transcripts and is central
to protein synthesis and phenotype determination.The
existance of genetic determinants for embryo viability is
therefore conceivable and could be identified by analysing
individual’s DNA. However, specific DNA variant
sequences associated with increased viability have not
been identified.
• In addition the variability in the DNA within a cohort of
embryos generated by a given couple will be limited to
meiotic recombination. Therefore whether an analysis of
embryonic DNA sequence can generate information on
embryo viability is still unknown
PGS-Preimplantation Genetic Screening
• Whereas DNA sequence analysis is not likely
strategy for embryo viability assessment,
chromosome numbers and integrity can
determine embryo viability
• FISH (fluorescent in situ hybridization)-9-12
chromosomes can be tested. However,
randomized controlled trials showed no
improvement in IVF outcome parameters and
some found decrease in IR&PR (Staessen
2004,2008, Mastenbrook 2007,Checa 2009)
Lack of benefit from PGS with FISH;
*Injury to the embryo from blastomere biopsy
*Mosaicism of the embryo for aneuploidy(potentially leading to false + diagnosis)
*Limited no.of chromosomes studied (potentially leading to false – diagnosis)
*FISH only detects the presence or the absence of the chromosomal region targeted by the
probe(usually at the centromere), and does not provide information about the remainder of the
chromosome
PGS-Preimplantation Genetic Screening
• PGS using comparitive genomic hybridization (CGH);
• Conventional CGH: Advantage over FISH is that the copy
no.of all chromosomes can be determined. More detailed
analysis of the entire length of each chromosome can be
obtained, allowing detection of chromosome segments
imbalance(Wilton 2005). Disadvantage is the length of time
(3-4 days) required for the procedure, embryos need to be
cryopreserved and transferred in the following cycle
• Microarray CGH: Analysis completed in <48hrs. No need to
cryopreserve cleavage stage embryos or PB screened zygotes
*Day 5 biopsy & 6 ET can
only be used for good
prognosis patients
*TB can only be applied
for exp.blasts.
*Risk of decreasing the
implantation potential of
a poor quality blast. by day
6 ET
Microfluidics
Microfluidic technology provides a unique means of interfacing known analytical methods for
embryo developmental physiology and molecular phenotypes in real time
Fluid handling systems (made of glass or polymer; PDMS) incorporating
structural flow features (eg. branced or unbranched channels) that exploit
the unique physical differences between macro- and micro scale fluids. They
utilize rectilinear fluid channels width >100µm with respect to height >10µm
and up to centimetres long. ( 10µl of culture medium,and 10 mm long would
hold 10nL. Volume:cross section area x lengthFor ex. a human blastocyst
is 175-225 µm in diameter, equating to 5 nL in volume capacity
Aim: Ideal device could be an active, continuous culture platform with
integrated time-lapse imaging and metabolomic or secretomic endpoints,
Providing real-time physiological outputs as the embryo develops, as well
as sampling for interface with more detailed molecular analysis.
Details to be solved before using these devices in clinical practice,
• Suitability of microfluidics for analysis of oocyte & embryo morphology,
integration of time-lapse monitorization
• Adaptation of combined omics technology for oocytes & embryos
To produce devices with more automation and less user intervention to systematize assisted
reproductive technology laboratories
Gardner et al., Human Gametes and Preimplantion Embryos. Assessment and Diagnosis, 2013
Viability assessment by birefringence imaging with
polarization microscopy
Spindle imaging of the MII oocyte
De Santis et al., RBM Online 2005
During meiosis and fertilization meiotic spindles are responsible for proper
segregation of the nuclear material, and abnormalities in this fragile structure can lead to
infertility, miscarriage and genetic diseases, such as Down syndrome
Why are results contradictory?
• The dynamics of spindle formation during oocyte maturation were
not considered
1. Spindle visualization might change within the maturation stages: MI-1st.PB extrutiontelaphase I (MS dissapear for 40-60 minutes!!)- MII
2. The microtubules of the MS are highly sensitive to chemical (hyaluronidase), and
physical changes ( temperature& pH variations) that may occur during oocyte
handling. Shift of the PB1 position may also be related to physical displacement
during denudation.
• A precise classification spindle imaging should be performed
repeatedly: after hyaluronidase treatment and immediately prior to
ICSI
***Spindle retardance, length, angle to PB, age differences are also confounding parameters
should also be precisely evaluated
Rienzi et al., RBM Online 2005
Montag et al.,RBM Online 2006
Oocyte zona birefringence intensity
High zona birefringence
Low zona birefringence
Montag et al.,RBM Online 2008
undetectable
Ebner-Balaban F&S 2010
Polarization microscopy allows the distinction of three layers within the ZP. Inner layer exhibits the highest
birefringence(Pelletier 2004). Zona birefringence intensity is higher in conception cycles(Shen 2005)
The multilaminar structure of the ZP revealed by polarization microscopy is directly linked to the paracrystalline network
structure of the zona which is formed during the follicular maturation by the oocyte.
So a high birefringence of the inner zona layer might indicate an optimal formation of the ordered structure during oocyte
maturation. HZB oocytes can have better conditions during follicular growth and maturation compared with a LZB oocyte
with unordered zona structure. Regular structural integrity of ZP may reflect an optimal cytoplasmic potential of an oocyte
and its various cellular and molecular structures
Ebner - Balaban F&S 2010
Time-lapse imaging; morphokinetics
•
One of the fundamental problems of the current embryo quality assessment
by morphology is the static evaluation of a highly dynamic developing entity.
Current systems analyze the morphology at a few predefined time points
during embryo development preimplantation, with the consequent lack of
information about what happened between the analyzed points. Thus
continual monitoring might provide one strategy to collect a complete
picture of embryo developmental kinetics and improve the success rate of
viable embryo selection
• So far 2 algorithm have been proposed for morphokinetic embryo selection
to improve success rates based on parameters derived from time-lapse
measurements
** Wong Nat Biotechnology 2010; Analyzed time-lapse image series of embryo
development to identify predictive markers of blastocyst development and
the underlying gene expression profile (arrested /normal developing)
Sample was composed of supernumerary embryos cryopreserved at the 2PN
stage and donated to research. None of the embryos were transferred. No
data on IR were obtained. Hierarchy of morphokinetic markers were not
used for decision making
** Meseguer HR 2010, F&S 2012
Morphokinetic identification of cell cycles: t2,t3,t4,t5,cc2,s2
t2 :1st.cell division
cc1 :1st.cell cycle
s1 :1st.syncrony
Correlation between time taken to reach each development milestrone and
the implantation potential of each embryo
Meseguer et al.,HR 2011
Time-lapse markers used for clinical outcome predictions
Chen et al.,F&S 2013
Conclusions
• Morphological markers
higly subjective/ predictive value limited!
**BUT still remain to be the solely method of choice, and evidence based !!
• New objective biomarkers for oocyte and embryo selection
1.
Most likely to be used in the nearest future?
• Utilization of polarized microscopy, Time-lapse monitoring : morphokinetics can be
widely spread out in clinical setting with more prospective randomized proofs.
Perhaps a combination of these systems might be considered in the near future?
2.
To be used in the future with improvements?
• Combined omics technology integrated into microfluidic devices? More time needed
***FAST, EASY-TO-USE ,NON-INVASIVE and COST EFFECTIVE