molecular aspects of implantation

Question 1

what things are seen in the endometrium under the microscope?

Answer 1

glandular epithelium
luminal epithelium
stroma
blood vessels

Question 2

what does the endometrium look like during the proliferative phase?

Answer 2

small glands with epithelial cells close together

dense stroma

Question 3

what does the endometrium look like during the early secretory phase?

Answer 3

glands expanding

secretory vesicles at basal side of epithelial cells

Question 4

what does the endometrium look like in the mid secretory phase?

Answer 4

further expansion of glands with secretory vesicles at apical side of epithelial cells
presence of secreted material in lumen

Question 5

what does the endometrium look like in the late secretory phase?

Answer 5

long extended glands with no secretory vesicles

oedema in stroma

Question 6

where are oestrogen and progesterone receptors expressed?

Answer 6

expressed in nuclei of stroll and epithelial cells

Question 7

when is oestrogen receptor expression at maximum?

Answer 7

late proliferative/early secretory phase of cycle

Question 8

when is progesterone receptor expression at maximum?

Answer 8

early secretory phase then decreases

decreases in epithelial cells before stroma

Question 9

what leukocytes are present in the endometrium?

Answer 9

uterine natural killer cells
macrophages
T cells
(no B cells)

Question 10

how do the populations of immune cells change during the menstrual cycle and early pregnancy?

Answer 10

uNK cells increase a lot
T cells stays same
macrophages very slight increase

Question 11

what is the window of implantation?

Answer 11

time during which the endometrium is receptive to embryo = days 20-23
characterised by expression of specific set of factors in the endometrium
luminal epithelial cells may develop pinopod extensions

Question 12

what is the initial interaction between at implantation?

Answer 12

trophoblast cells of embryo and luminal epithelium

later it is between trophoblast cells and stroma

Question 13

what are the stages of implantation?

Answer 13

apposition (orientation of blastocyst on the lumen of the endometrium)
adhesion (interaction between trophoblast cells and luminal epithelial cells in endometrium)
invasion (breakdown of connective tissue between luminal epithelial cells and passage of embryo through to the underlying stroma)

Question 14

what are the different populations of trophoblast cells?

Answer 14

villous trophoblast (invasive - come into contact with maternal stroma. anchoring) 
endovascular trophoblast (invade maternal blood vessels) 
syncytiotrophoblast (formed inside maternal blood vessels by cell fusion)

Question 15

what is decidualisation?

Answer 15

after implantation stroma cells undergo decidualisation (change phenotype)
start secreting many factors including prolactin and IGFBP1
controlled by cAMP ad progesterone

Question 16

what molecules are involved in the implantation process?

Answer 16

adhesion molecules = integrins and mucins
proteases
cytokines and growth factors

Question 17

what are integrins?

Answer 17

heterodimers with alpha and beta subunits
mediate cell binding to extracellular matrix
transduce signals from ECM into cells
regulate gene expression including those of ECM degrading enzymes
unregulated in WOI
highest expression in epithelium and blood vessels

Question 18

what are the different types of integrins?

Answer 18

αvβ3 - may be involved in attachment of embryo to endometrium
α1
α4

Question 19

what are mucins and what is there role?

Answer 19

MUC1 = glycoprotein on lining the luminal epithelial cells
prevents embryo access to luminal epithelium
glycosylation needs to been removed to allow implantation to occur

Question 20

what are matrix metalloproteinases (MMPs)?

Answer 20

collagenases 
gelatinases 
stromeolysins 
found in endometrium 
controlled by progesterone - decreases production therefore increased MMPs seen at end of cycle when progesterone levels decrease

Question 21

what is the role of protease in endometrial function?

Answer 21

implantation = breakdown of extracellular matrix to allow embryo through epithelial cells, breakdown of extracellular matrix tissue to allow trophoblast cells to invade sstroma 
menstruation = breakdown of endometrial tissue

Question 22

when does the expression of cytokine increase?

Answer 22

at time of implantation

Question 23

what is the role of cytokines in embryo implantation?

Answer 23

receptors expressed by cytotrophoblast cells
shown to bring positive secretory effects and negative apoptosis and decreased cell growth of cytotrophoblast
could affect leucocyte activity (uNK)