Menstrual cycle 2

Question 1

Discuss the switch of E2 to positive feedback and the LH surge

Answer 1

At the end of the follicular phase E2 feedback becomes positive causing exponential rise in LH which need to exceed a threshold (required for ovulation)

LH surge will last for 36-48 hours. This will trigger ovulation.

The LH surge is a precise predictor of ovulation

LH is cleared from serum in contrast to hCG which is cleared slowly and binds with great affinity to LHCGR
(Luteinizing hormone/choriogonadotropin receptor)

Question 2

What releases hCG?

Answer 2

The growing placenta -the embryo

The hCG will maintain the corpus luteum

Question 3

Where are LHr found on the follicle?

Answer 3

They are found on both theca and granulosa cells

Question 4

How does the structure of a preovulatory follicle differ following LH stimulation prior to ovulation?

Answer 4

There is a loss of OSE (Ovarian surface epithelium).There is also a breakdown of underlying basal lamina and GC and TC at apex to allow for rupture.
This will allow the invasion of blood vessels into the follicle.

Granulosa cells do not have vasculature but theca cells do.

GC (granulosa cells)basal lamina is disrupted allowing extension of blood vessels into GC layer and for infiltration of theca cells and leukocytes into GC compartement.
COC detached from surrounding GC to expand.

Question 5

At what point will the oocyte come out of meiotic arrest and undergo meiosis 1 ?

Answer 5

This will occour during the LH surge

Question 6

What factors regulate the meiotic arrest of follicles?

Answer 6

1.High cAMP-This keeps the maturation promoting factor (MPF) inactive

What keeps cAMP high is :
2.cGMP enters oocytes from cumulus cells via gap junctions to inhibit oocyte cAMP phosphodiesterase PDE3A activity(PDE4A normally will degrade cAMP)

3. H202/No/Calcium
4. Other cells /ovarian environment

Question 7

What are the effects of the LH surge ?

Answer 7

Within 3-12 hours of the LH surge:

1.There is a detachment of the COC from surrounding mural granulosa cells, followed by cumulus cell expansion=the formation of the unique extracellular matric between cumulus cells (mucification) -this makes the complex sticky

• This is comprised of long chains of hyalyuronan
• Visco-elastic properties of CC matrix improtant for successful ovulation,ovum pick up by oviducts and penetration of sperm

Question 8

How does Lh surge lead to the ceasation of meiotic arrest?

Answer 8

There will be an activation of PDE3A which causes a reduction of cAMP.This leads to activation of pathways leading to the breakdown of nuclear membrane in primary oocyte (germinal vesicle breakdown)

This will cause the resumption of meiosis in the oocyte -com0pleted meiosis and the release of the first polar body

Arrests again in Metaphase 2

Question 9

Outline the uneven division during meiosis of an oocyte

Answer 9

The early oocytes are classified as immature at germinal vesicle or metaphase 1 stage

Meiosis 1 is completed with half chromosomes but nearly all cytoplasm will remain in the secondary oocyte

The remaining chromosomes will move with small bag of cytoplasm to form discarded polar body

Question 10

Why do we have an unequal division of cytoplasm ?

Answer 10

There is unbalanced division to form polar bodies so that the egg will contain enough nutrients for early embryonic development. This includes mitochondria which is why we get all our mitochondrial DNA from our mother.
Polar bodies can be tested for chromosomal abnormalities during IVF. However, these will only detect if errors of meiosis 1.

Question 11

What will happen following resumption of Meiosis during LH surge ?

Answer 11

Chromosomes of the secondary oocyte immediately enter 2nd meiotic divison and will form the 2nd metaphase spindle then arrest.

This arrest is maintained by cytostatic factor(protein complex)

Egg is ovulated in this arrested state

Question 11

What will happen following resumption of Meiosis during LH surge ?

Answer 11

Chromosomes of the secondary oocyte immediately enter 2nd meiotic divison and will form the 2nd metaphase spindle then arrest.

This arrest is maintained by cytostatic factor(protein complex)

Egg is ovulated in this arrested state

Question 12

What are some of the main effects of the LH surge during ovulation?

Answer 12

The LH surge will induce expression of progesterone receptor (PR) in the granulosa cell in all species and result in luteinisation of DF (dominant follicle) cells (both granulosa and theca)
The Oestrogen production will fall and progetseron is stimulated

Blood will flow to the follicle and this increases and new vessels appear in avascular granulosa cells

Prostaglandins and proteolytic enzymes e.g collagenase and plasmins are increased in response to LH and progesterone

Question 13

What are the roles of collagenase and plasmin

Answer 13

Digest the collagen in follicle wall

This causes the appearance of the stigma /apex which is the point of the fominant follicle which is closest to the ovarian surface where digestion occours

Question 14

Outline how ovulation is an inflammatory process

Answer 14

There is a cascade of events which leads to the release of the COC -this leads to ovulation

Increased secretion of chemokine/cytokines from granulosa cell and theca cell triggers massive infiltration of leukocytes from circulation
(Acute inflammatory response)

In humans -oculation occours randomly from either ovary during a given cycle some indication more common from right ovary

Progesterone is essential for ovulation

(progesterone inhibitor (RU486) will suppress ovulation.

Prostaglandins-0E and F and hydroxyeicosatetraenoic acid

Question 15

Outline how ovulation is an inflammatory process

Answer 15

There is a cascade of events which leads to the release of the COC -this leads to ovulation

Increased secretion of chemokine/cytokines from granulosa cell and theca cell triggers massive infiltration of leukocytes from circulation
(Acute inflammatory response)

In humans -oculation occours randomly from either ovary during a given cycle some indication more common from right ovary

Progesterone essential for ovulation
Progesterone inhibitor (RU486) suppress ovulation
Prostaglandins-E and -F and hydroxyeicosatetraenoic acid (HETE metabolite of arachidonic acid) reach a peak level in follicular fluid just prior to ovulation
Prostaglandins stimulate proteolytic enzymes (proteases)
HETEs may stimulate angiogenesis and hyperemia (↑blood flow)

Question 16

How does LH cause the follicular rupture to take place ?

Answer 16

LH stimulates secretion of Plasminogen Activator (PA).
Collagenase disrupts fibril network of theca & tunica albuginea & promotes digestion of basement membrane of follicle and OSE.
TNF induces cell death, proteolysis, stigma formation and eventual follicular rupture

Question 17

Outline ovulation

Answer 17

Secondary oocyte (arrested in metaphase II) with cumulus cells is extruded from the ovary.
Follicular fluid may pour into Pouch of Douglas.
Egg ‘collected’ by fimbria of uterine tube – tubes must be patent (not damaged/blocked).
Egg progresses down tube by peristalsis and action of cilia. Ciliated cells are controlled by oestrogen.
Residual part of follicle collapses into space left by fluid – a clot forms and whole structure become corpus luteum.

Question 18

What is the pouch of Douglas ?

Answer 18

the extension of the peritoneum between the rectum and the posterior wall of the uterus in the human female.

Question 19

Describe the process of inflammation which is associated with ovulation

Answer 19

The follicular fluid is “inflammatory”

(It contains inflammatory markers such as macrophages)

Inflammation definitely present, but too much is detrimental…
Higher “inflammation markers” in FF associated with decreased pregnancy rate (specifically C Reactive Protein, CRP)
Gingivitis associated with poorer IVF outcomes!

Question 20

What is Gingivitis?

Answer 20

Gingivitis is a common and mild form of gum disease (periodontal disease) that causes irritation, redness and swelling (inflammation) of your gingiva, the part of your gum around the base of your teeth.

Question 21

How does the ovulatory wound heal itself ?

Answer 21

The ovary faces monumental task of repairing damage caused by follicle rupture after each ovulation. The basic steps are known but the underlying mechanisms are still unknown. Interestingly the ovulation wounds scar, but not for long – they are resolved very quickly. This may be due to the steroidogenic environment – mitogenic (oestrogen).

Question 22

What are some signs of ovulation?

Answer 22

Slight rise in basal temperature typically 0.5-1 degree (using thermometer)

Tender breasts
Abdominal bloating
Light spotting
Changes in cervical mucus
Slight pain or ache on one side of the abdomen

Question 23

How can the cervical mucus be a sign of ovulation?

Answer 23

The cervical mucus or cervical fluid changes throughout MC.
Immediately after menstruation, the cervical mucous is scant and viscous.
In late follicular phase, ↑ E2 levels, the cervical mucous becomes clear, copious and elastic.
The stretchability/elasticity of cervical mucous evaluated between two glass slides and recorded as the spinnbarkeit.
After ovulation, ↑progesterone levels, the cervical mucous again becomes thick, viscous and opaque and ↓ quantity produced.
However might have egg white cervical mucus and still NOT ovulate – need to use more than 1 method of tracking.

Question 24

What do ovulation prediction kit measure ?

Answer 24

Fertile period spans 6 days and is affected by: Lifespan of the egg → up to 24h after ovulation Lifespan of sperm → median=1.5days but sperm can survive up to 5 days in the sperm supportive mucus of fertile days of cycle » sperm survival is dependent on the type & quantity of mucus within cervix AND the quality of the sperm E3G is urinary metyabolite of oestradiol and allows women to identify days of high fertility leading up to ovulation

Question 25

What forms the corpus luteum and how does this happen?

Answer 25

After ovulation, remaining granulosa enlarge, become vacuolated in appearance, and accumulate a yellow pigment called lutein. Massive angiogenesis to form new capillaries The luteinized granulosa cells combine with newly formed theca-lutein cells and surrounding stroma in the ovary to become the corpus luteum (CL). What hormones are produced by CL? Progesterone Inhibin A Androgens Oestrogens

Question 26

What will control the demise of the corpus luteum ?

Answer 26

What determines the life-span of the CL? Life span of CL depends on continued LH support or hCG from pregnancy (luteotrophic support) Process is not well understood In humans and higher primates NOT due to luteolytic agents but loss of luteotrophic support (i.e. below threshold levels of LH enough for maintenance for a whilst) CL undergoes luteolysis if no pregnancy and forms a scar tissue called the corpus albicans. Cell death occurs, vasculature breakdown, CL shrinks removal of CL essential to initiate new cycle

Question 27

Discuss menstruation and some of the changes that take place

Answer 27

Progesterone withdrawal results in increased coiling and constriction of spiral arterioles Endometrium releases prostaglandins that cause contractions of uterine smooth muscle and sloughing of degraded endometrial tissue Use of prostaglandin synthetase inhibitors decreases amount of menstrual bleeding Average duration of menstrual flow is 4-6 days (range 2-8 days) Average amount of menstrual blood loss is 30ml with >80ml abnormal

Question 28

What are some disorders of ovulation and anovulation?

Answer 28

Anovulation is a common cause of infertility in women – affecting up to 40% of infertile women Can be due to non-ovarian causes eg obesity, thyroid disorders Ovarian causes can be - primary ovarian insufficiency (POI) aka premature ovarian failure due to loss of follicles OR due to disorders that prevent ovulation: Luteinized unruptured follicle syndrome (LUF) Effect of non-steroidal anti-inflammatory drugs (NSAIDs) Polycystic Ovary Syndrome (PCOS)

Question 29

Describe what LUF is

Answer 29

Luteinized unruptured follicle syndrome (LUF) Normal follicle growth in follicular phase and normal hormonal profile but absence of follicle rupture and no release of oocytes Form a CL with trapped oocyte and luteal phase length is normal Diagnose using repeated transvaginal ultrasound LUF occurs in women with normal menstrual cycle at rate of 5% but in infertile women at rate of >25% (reviewed Duffy et al, 2019, Endocrine Reviews, 40:369-416) Linked to dysregulation of ovulation associated inflammatory changes e.g. reduction in prostaglandin synthesis/action. EVIDENCE: Patients treated with high dose prostaglandin synthetase inhibitors (eg Indomethacin) → block in prostaglandin production and follicular rupture The lack of cytokine - Granulocyte colony-stimulating factor 3 (CSF3) - has been linked to LUF formation in infertile women. In anovulatory women, a single injection of CSF3 during late follicular phase resulted in ovulation in most of the women

Question 30

What are NSAIDS and how do they work?

Answer 30

NSAIDs commonly used for relieving pain, lowering fever and reducing swelling. NSAIDs work by suppressing prostaglandins, the essential stimulators of inflammation Concept of ovulation as an “inflammatory response” → concern regarding effects of NSAIDs and ovulation Ovarian follicle expresses 2 types of prostaglandin synthase – PTGS1 (constitutive) and PTGS2 (inducible) ↑PTSG2 expression just before ovulation Administration of NSAID that specifically inhibit PTGS2 → delayed follicle rupture & oocyte release Most studies of NSAID inhibition of ovulation use doses that are at or above the maximum dose prescribed

Question 31

What is ovarian cancer and how can it affect ovulation?

Answer 31

Epithelial ovarian cancer (EOCs) most common cause of death from gynaecological malignancy in developed world EOCs comprise heterogenous group, most lethal form is high-grade serous cancer (HSGC) 10-25% of OvCa associated with hereditary genetic mutations eg BRCA1 or BRCA2 mutations For many years most accepted hypothesis of EOC carcinogenesis was the “incessant ovulation” theory Ovulation traumatises the OSE, hence increasing error during cell replication Epidemiological evidence that women with high number of life-time ovulations at increased risk of EOC eg. nulliparous women, those with early menarche and late menopause Long-term use of oral contraception reduces OvCa risk (MF Fathalla (2013) Facts Views Vis Obyn. 5:292-297) New evidence indicates that HSGC arises from fimbria of fallopian tube rather than the ovaries! RCOG “The distal fallopian tube as the origin of non-uterine pelvic high-grade serous carcinomas” Scientific Impact Paper No. 44 (Nov. 2014)