Endometrial receptivity - window of implantation , markers for ER , ERA , Limitations , strategies to improve ER has been discussed .

1. ENDOMETRIAL RECEPTIVITY
By Dr. G. Abirami

2. Successful implantation requires the presence of a
- healthy embryo
- a receptive endometrium
- a synchronized and successful molecular dialogue
between the two and
- immune protection from the host.

3. • The human endometrium is a dynamic tissue
• It undergoes changes at multiple levels during the
menstrual cycle in response to ovarian hormones
and paracrine secretions.
• The endocrine and paracrine secretions control gene
expression of the different endometrial cell types.

4. • Endometrial receptivity is a self limited period in which
the endometrium acquires
- a functional and transient steroid dependent status that
allows a blastocyst to attach to the endometrial
epithelium and
- to invade further into the decidualized stroma through
mediation by immune cells , cytokines, growth factors ,
chemokines and adhesion molecules.

5. • During the phase of receptivity, the endometrium
undergoes morphological, cytoskeletal, biochemical,
and genetic changes to become functionally
competent.
• This period of receptivity is known as the “window
of implantation” (WOI).

6. WINDOW OF IMPLANTATION
• opens on day 19 or 20 of the cycle and remains open
for just 4–5 days at the time when Progesterone
reaches peak serum concentrations.
• D6 to D10 – post ovulation or
• D7 to D11- post LH surge or
• D20 to D24 of 28 day cycle

7. EFFECT OF COH ON ER
• Abnormalities of the luteal phase have been
detected in all the stimulation protocols on
both hormonal & endometrial levels.
• COH adversely affect endometrial receptivity

8.  High concentration of estrogens & progesterone, altered
E2 to progesterone ratios.
 Disturbed LH levels
 Corpus luteum deficiency
 A direct effect of GnRh agonist or antagonist on the
corpus luteum or on endometrium
 Altered endometrial receptivity from endometrial
asynchrony & earlier expression of pinopodes

9. • Endometrial histology in GnRh-agonist cycles (mid-
luteal biopsy) :
 increased glandulo-stromal dyssynchrony
 delay in endometrial development
 strong positivity of endometrial glands for PR
 decreased cell adhesion molecule profiles and
 earliest appearance of surface epithelium pinopodes
• shift forwards of implantation window. .

10. • Progesterone supplementation improves endometrial
histology, and its necessity has been established, at least in
cycles, using GnRh agonists
• There is increased peri-ovulatory Progesterone in the COH
cycles.
• The early rise of Progesterone has a negative impact on
endometrial receptivity but not on oocyte-embryo quality
these cause premature endometrial lutenization & provide an
explanation for the observed decrease in endometrial
receptivity

11. • Implantation & pregnancy rates did not differ
between IVF-ET patients and recipients of donor
oocytes.
• Exposure of the developing endometrium to COH
during IVF cycles does not inhibit embryo
implantation or affect pregnancy rate.

12. ASSESSMENT OF ER
• A. FUNCTIONAL MARKERS:
 Biochemical markers
• 1. Endometrial adhesion molecules - Integrins - co-expressed
on glandular epithelium only during cycle D 20 to 24
– 3 integrins are expressed by the endometrium with a pattern that
coincide well with the window of implantation
– α 1β1
– α 4β1
– α vβ3 ( coincides with Window Of Implantation)

14. • 2.Endometrial anti-adhesion molecules - Mucin 1 and 6
• 3. Endometrial Cytokines- Leukemia inhibitory factor Interleukin-1
,Interleukin-11, Colony-stimulating factor.
• 4. Endometrial growth factors - Heparin binding-epidermal growth
factor, Insulin like growth factor binding protein
• 5. Other endometrial markers -Mouse ascites Golgi (MAG),
Laminin,HomeoboxA10, fibronectin & collagen IV ,Glycodelin, Cyclin
E & p27

15. ENDOMETRIAL FUNCTION TESTS:
The most efficient way to directly assess endometrial receptivity
1. MAG test:
Endometrial biopsy.
 It measures a sticky mucinous substances that is secreted by
endometrial glands before implantation.
 85% of normal fertile women express higher levels of MAG
between D 5 & D 18 & no expression after D19.
 70% with unexplained infertility showed abnormal MAG
levels.

16. 2. Cyclin E & p27:
• It allows dating of the endometrium & differentiating
between normally & abnormally developing
endometrium.
• Cyclin E: First appears in proliferative phase & not seen
after D19
• P27: First appears on D17 & remains for the rest of the
cycle.

17. B. Morphological markers
1. Pinopodes:
• Globular protrusions in the surface membrane of endometrial
epithelial cells.
• Accurate markers of the implantation window.
• Last for less than 2 days.
The timing of their formation depends on:
1. The hormone treatment applied
2. Patient's individual response.

19. • On average, they form on days 20-21 in natural, days 19-20 in COH, and
days 21-22 in HC (hormone controlled)cycles
• There is a wide (up to 5 days) variation between women in the cycle days
on which pinopodes form.
• Pinopode numbers correlate with implantation .On the other hand there
is evidence of implantation occurring in the absence of pinopodes
• In natural cycle: There is an inherent synchrony between the maturing
endometrium & the developing embryo, ensuring that both will meet at
the right stage.
• Fully developed pinopodes have been detected on days LH+6 to LH+9
(days 19 to 22) in different individuals.

20. • In COH- IVF cycles: Embryonic development is probably delayed because
of the in vitro conditions ,while the endometrium may be advanced
resulting in an early closure of the implantation window before the zygote
eventually reaches a stage capable of initiating implantation.
• Accelerated pinopode formation correlated strongly with preovulatory
progesterone rise (≥6 ng by day 13).
• Consequently, it would be highly desirable if the window of receptivity in
IVF cycles could be postponed for a couple of days.
• A low dose of mifepristone (antiprogestin) on days 14 and 15 caused
delayed pinopode formation .

21. In Hormone –Controlled cycles:
• The most receptive day of the cycle corresponds to fully
developed pinopodes or is postulated to be 1 day before
regressing or 1 day after developing pinopodes are observed.
• A transfer cycle follows in which synchronization with the
embryo is arranged so that the predicted most receptive day
coincides with embryonic age day 6. It is assumed that by that
time the IVF embryo is ready to implant.

22. 2. Decrease in the epithelial tight junctions
between D13 & 23.
3.Apoptosis On D 19-20 apoptosis is detectable
in the glands of the basal layer

23. MOLECULAR MARKERS
• The various molecular approaches for the study of biological samples are
collectively called the “Omics”.
It includes –
• Genomics - study of genes
• Epigenomics -study of gene Expression
• Proteomics -quantification of proteins
• Metabolomics – composition and quantification of metabolites
• Lipidomics - composition and quantification of lipids
• Secretomics- analysis of complex array of chemokines,cytokines, growth
and signaling factors.
• Transcriptomics is considered the most established technology available
for evaluation of the endometrial factor.

24. • Analysis of gene expression pattern is done by three
approaches
- Macroarray
- Microarray
- Differential display polymerase chain reaction (whole
genome analysis)

25. ENDOMETRIAL RECEPTIVITY ARRAY
• Developed by Diaz – Gimeno et al
• Bioinformative predictor of endometrial dating
• A total of 238 genes are expressed in optimal models
• High reproducibility – transcriptomic profile valid over next 3 years.
• Sensitivity - 99.75%, Specificity – 88.57%.
• Good tool to provide favourable outcome in RIF.
• Accurate, reproducible, No intercycle variability.
• Defining a receptive window will avoid embryo wastage and
emotional, physical and financial distress.

28. • STORAGE
– Keep in fridge (4 – 8c) for 4 hrs.
– This preserved sample, in cryotube can beimmediately
shipped at room temp.
– Sample at room temp should reach the main lab
within 4 to5 days.
– Results will be ready in 20 days after receiving
samples.

30. • LIMITATIONS OF GENOMICS :
- Large variation + variable expression of genes
- The mRNA/ gene products/ proteins need to be analysed
- Need endometrial tissue biopsy( invasive)
- Interferes with implantation

31. USES OF ENDOMETRIOMICS
• Nutritional environment of developing embryo
• Markers for assessment of ER
• Timing of embryo transfer
• Effect of therapeutic intervention
• Alternative stimulation regimen
• Insight about diagnosis of RIF
• Assessing impact of pathological conditions

32. NON INVASIVE ASSESSMENT
1. TVS: Thickness & pattern
– Favorable receptivity: Trilaminar pattern (triple line), Thickness:7-14
mm
– Unfavorable receptivity: Hyperechoic or isoechogenic, , Thickness<7
mm or >14 mm.
– Endometrial thickness: has a significant positive correlation with the
duration of follicular stimulation & an inverse correlation with age.
2. 3D US: Endometrial volume:
– 2 ml is the minimum for a receptive endometrium
– <1ml: no pregnancy . > 4 ml. No increase in ER
3. Doppler US: Some authors reported significant correlation between
pregnancy rates & uterine artery Doppler flow values , while others failed
to show such a relationship.

33. 4. 3D power Doppler US:
– Sub-endometrial perfusion can not predict ER
– Use of subendometrial vascularization index was superior in
predicting the pregnancy rate of IVF to using endometrial volume
5. MRI: High cost, not used in routine practice
6. LASER blood-flowmetry
– A novel way to assess ER by measuring endometrial tissue blood
flow, using hystero fiberscope laser blood-flowmetry.
– It is superior to conventional parameters for determining ER for
implantation.

34. STRATEGIES TO IMPROVE ER
I. To develop ovarian stimulation protocols that cause a
minimum reduction in endometrial receptivity.
II. To avoid the endometrium during stimulated cycles
altogether by freezing the embryos & replacing them in
subsequent natural cycles.
III. To improve uterine vascularization. (aspirin, L arginine,
sildenafil)
IV. To treat the pathology