Implantation

Question 1

What are the stages of implantation?

Answer 1

• Hatching: Embryo escapes the zona pellucida.
• Apposition: Initial contact with the endometrium.
• Attachment: Adhesion molecules anchor the embryo.
• Invasion: Trophoblast cells invade the uterine lining.

Question 2

What factors regulate implantation?

Answer 2

Proteases, cytokines (e.g., LIF, IL-1), integrins, and growth factors like VEGF.

Question 3

What factors affect embryo hatching?

Answer 3

Proteases regulated by growth factors like EGF and LIF help the embryo shed the zona pellucida.

Question 4

How do cytokines influence implantation?

Answer 4

Pro-inflammatory cytokines like IL-1 and LIF promote embryo-endometrium interactions and trophoblast invasion.

Question 5

What role does VEGF play during implantation?

Answer 5

VEGF supports angiogenesis in the endometrium and placenta, which is crucial for embryo implantation.

Question 6

What are pinopodes? and what is their function?

Answer 6

Pinopodes are projections on the endometrial surface that absorb uterine fluid and help facilitate embryo adhesion.

Question 7

How does MUC-1 affect implantation?

Answer 7

MUC-1 on the endometrial surface aids initial adhesion of the embryo and modulates immune response during implantation.

Question 8

What role do integrins play in implantation?

Answer 8

Integrins on the embryo and endometrium mediate adhesion during apposition and attachment.

Question 9

What is the role of matrix metalloproteinases (MMPs) during implantation?

Answer 9

MMPs degrade the extracellular matrix, enabling trophoblast invasion into the uterine lining.

Question 10

What changes occur in the endometrium during the implantation window?

Answer 10

It becomes thickened, vascularized, and secretes adhesive molecules like integrins and cytokines.

Question 11

What is the role of IL-1in implantation?

Answer 11

IL-1 promotes trophoblast differentiation and invasion, supporting successful implantation.

Question 12

what is the possible mechanism behind hatching?

Answer 12

The mechanical pressure from the blastocyst expansion causes a nick in the zona pellucida, facilitated by a protease. Through the nick, the blastocyst egresses out of the zona pellucida, leaving the ZP intact

Question 13

what regulates the expression of proteases?

Answer 13

epidermal growth factor (EGF),
heparin binding like-epidermal growth factor (HB-EGF),
transforming growth factor-β
leukaemia inhibitory factor (LIF)

Question 14

How does MUC-1 expression change?

Answer 14

MUC-1 is continuously present at the luminal surface of the endometrial cavity throughout the cycle, with an increase in the secretory phase.

Question 15

what stimulates pinopode development?

Answer 15

Progesterone

Question 16

What is the function of a pinopode?

Answer 16

Regulation of luminal fluid.
Prior to implantation, uterine fluid volume increases to promote embryo transportation and appropriate intrauterine position.
Fluid levels decrease following transportation allowing luminal closure to facilitate attachment of embryo to the uterus.

Question 17

how do integrins support implantation?

Answer 17

may establish a firmer adhesion after the appositioning process initiated by selectin.

Question 18

why are cytokines suspected to have a role in implantation?

Answer 18

Proinflammatory markers including prostaglandins, cytokines and leukocytes are elevated during implantation.
Many proinflammatory cytokines have been identified at the maternal-fetal interface in early pregnancy, including interleukin-1 and leukaemia inhibitory factor.

Question 19

What is the role of LIF in implantation?

Answer 19

The possible mechanism is that it modulates trophoblast differentiation.

Question 20

what is the suspected role of CSF-1 in implantation?

Answer 20

A possible mechanism for this is a trophic effect on trophoblast cells, thereby promoting embryo implantation. Substitution of CSF-1 in women with recurrent abortion seems to have a beneficial effect.

Question 21

what is the role of VEGF in implantation?

Answer 21

• An angiogenic factor involved in angiogenesis in different parts of the body.
• Implantation and subsequent placentation of the embryo into endometrium is not possible without angiogenesis in the endometrium, making it receptive and in the developing embryo, leading to the formation of the placenta.
• The human blastocyst is a source of VEGF → it produces IL-1β, which induces VEGF production.

Question 22

what is the suspected role of Glycodelin-A in implantation?

Answer 22

Glycodelin may play a role in this process as it has immunosuppressive properties via the inhibition of natural killer cell activity and is the major secretory product of the endometrium.

Question 23

what is the role of MMPs in implantation?

Answer 23

The matrix metalloproteinases (MMPs) are a family of zinc-containing endopeptidases capable of degrading all components of the ECM, both interstitial matrix and basement membrane.

The ECM degradation permits cellular invasion to take place.

Question 24

What is the specific role of MMP-2 and -9 in implantation?

Answer 24

degrade collagen IV, the main component of the basement membrane, and are therefore regarded as key enzymes in the implantation process, enabling the invasion of the trophoblast cells through the decidua and into the maternal vasculature.

Question 25

what does oestrogen cause to change in the endometrium?

Answer 25

Up-regulation of progesterone receptors
Up-regulation of VEGF, IGF-1, HB-EGF, L-selectin
Endometrial proliferation

Question 26

what does progesterone cause to change in the endometrium?

Answer 26

Pinopode formation (electron microscopy)
Up-regulation of CSF, IL-1, prostaglandins, VEGF, glycodelin A, IGF-II, HB-EGF, fibronectin, MUC-1, L-selectin
Down-regulation of oestrogen receptors and oestrogen activity