Lecture 3 - embryo implantation

Question 1

What are the essential factors for implantation?

Answer 1

1. correct window (receptive endometrium)
2. healthy embryo at blastocyst stage
3. communication between mother and embryo at time of implantation

Question 2

What are the characteristics of a non-receptive endometrium?

Answer 2

• Long apiucal microvilli
• high surface negative charge
• Thick mucin layer

Question 3

What are the characteristics of a receptive endo? (Window of implantation)

Answer 3

• Shortening of microvilli (blasto has enzymes that destroy villi)
• Loss of surface negative charge
• Thinning of mucin charge
• Formation of pinopodes (glue to blasto)

Question 4

What is decidualisation?

Answer 4

Post ovulation process of endometrial remodelling in preparation for pregnancy

Question 5

What happens during decidualisation?

Answer 5

1. Secretory transformation of uterine glands
2. Influx of specialised NK cells and vascular remodelling
3. Stromal cells acquire unique ability to regulate trophoblast invasion, resist inflam insults and dampen local maternal immune response

Question 6

When does decidualisation occur in humans?

Answer 6

Mid-luteal phase, independent of pregnancy

Question 7

What drives decidualisation?

Answer 7

Progesterone - changes at both transcriptome and proteomic level

Question 8

Where are the short range signals during pre-conception environment derived from?

Answer 8

Sperm, oocyte, seminal plasma, embryo

Question 9

Where are the long range signals during pre-conception environment derived from?

Answer 9

Hormone, nutrition and environmental factors

Question 10

What are the molecular messages at implantation?

Answer 10

Attachment 
- Mucin1: do not attach 
- LIF/adhesion molecules: attach 
Invasion 
- MMPs/TIMPs (b.d.)
- PGs
- COX2 
- IL-11
- VEGF (placentation)

Question 11

What contributes to implantation failure?

Answer 11

Endometrial factors - thin endo, altered adhesive molecule exp and immunological factors
Embryo factors - genetic abnorm, sperm defects, emb aneup or zona hardening

Question 12

What are the developmental stages in early embryo development?

Answer 12

Embryogenic (conceptus) - 14 days, hCG synth
Embryonic (embryo) - 6 weeks, diff of cells and tissues
Fetal (fetus) - 220 days, 2nd and 3rd trimester

Question 13

What are the roles of hormones during implantation?>

Answer 13

Est: stim prolif and diff of uterine epithelial cells
Prog: stim prolif and diff of stromal cells
Adequate production of progesterone is critical to maintenance of pregnancy until placenta takes over at 12 weeks
hCG synth (by tropho) prolongs progesterone secretion