L1 pt. 1: Transport and Quality Assessment

Question 1

What is the function of the uterotubal junction?

Answer 1

Valve that controls movement of spermatozoa between oviduct and uterus

Question 2

How is sperm quality assessed in labs (4 example techniques)

Answer 2

• CASA: Morphology and motility (with reference to WHO quality parameters)
• Live/dead stain (routine in andrology labs)
• PICSI tests ability to bind hyaluronic acid and thus oocyte material
• Flow cytometry which automatically measures quality parameters; widely used in livestock andrology

Further stain example: JC-1 stain for mitochondrial membrane potential (specific for ATP production in midpiece of sperm)

Question 3

What processes take place in the testes and can impact fertility if impaired? (x2)

Answer 3

Sperm assembly and DNA condensation

Question 3

What sperm processes occur in the epididymis and can affect fertility if aberrant? (x3)

Answer 3

Sperm maturation, lipid and protein modification, sperm storage

Question 4

Factors that affect male fertility in seminal plasma: (x2)

Answer 4

Accessory protein secretion, adsorbance to sperm surface (aggregation)

Question 5

What unique motility is observed in certain marsupial species?

Answer 5

• Cooperative Swimming
• Sperm swim better in pairs, and motility is erratic in unpaired specimens

Question 6

Types of DNA damage that can impact sperm quality (x4):

Answer 6

• Direct injury to purines/pyrimidines
• Single and ds breaks
• Cross-linking
• Chromosomal rearrangements

Question 7

How can damage to mitochondria affect sperm quality? -> Alternatively, how may this impact potential offspring?

Answer 7

• Damage to mDNA results in decreased ATP production
• This results in impaired motility
• In eutherian mammals, upon fertilisation, the tail is tagged with ubiquitin for degradation; damage to mDNA will not be transmitted to offspring in event of successful fertilisation

Question 8

How can damage to sperm membrane affect sperm quality?

Answer 8

• Lipid peroxidation of polyunsaturated fatty acids results in impaired motility

Question 9

Name a technique for sorting sperm head quality?

Answer 9

• MACS (Magnetic activated cell sorting)

Question 10

How often are male factors involved in infertility cases?

Answer 10

50%

Question 11

How can oxidative stress damage sperm?

Answer 11

• ROS implicated in various sperm events (capacitation, acrosome reaction, binding and traversing ZP)
• Can case severe damage (poor motility, morphological abnormalities, DNA damage and ultimately cell death)

Question 12

How does DNA fragmentation come about? What factor is crucial in fragmentation differences observed between species?

Answer 12

• Impacted by various lifestyle and environmental factors
• Rate of fragmentation increases upon incubation at 37 degrees
• Higher concentration of cysteine groups in Protamine-1b reduces percentage of DNA fragmentation (confers greater stability in the gene)

Question 13

+ 3 mechanisms through which the female reproductive tract prevents polyspermy

Answer 13

• Selective prevention of passage of sperm depending on surface protein expression (e.g. calreticulin, ADAM1a, 2, 3)
• Hardening ZP (via oviductal proteins such as heparin-like GAGs) -> resistance to hydrolytic enzymes
• Deploying cortical granules filled with hydrolytic granules upon first fertilisation -> increases hardness of ZP

Question 14

+ Give two types of interaction that modulate sperm chemotaxis (excluding immune reactions)

Answer 14

• Hormonal interactions: Progesterone modulates CatSper activity, allowing calcium influx, activating capacitation
• Chemokine-receptor interactions using factors released by oocyte/GC e.g. CXCR4 on sperm and SF1, which 70% of sperm do not express -> point of selectivity

Question 15

+ How might direct cell-cell interactions facilitate sperm selection in the female RT?

Answer 15

• Immunological selection
• Immune targeting of specific paternal antigens, inducing post-mating inflammatory response -> neutrophil influx into uterine lumen

Question 16

+ What roles do ROS have in male fertility? Give examples (hydrogen peroxide)

Answer 16

• Physiological role: e.g. hydrogen peroxide stimulates capacitation via tyrosine phosphorylation (and also stimulates hyperactivation)
• Aetiological role: e.g. DNA fragmentation, lipid peroxidation of polyunsaturated FAs -> as seen in exposure to exogenous hydrogen peroxide

Question 17

+ List 3 key exogenous sources of ROS

Answer 17

• Pathological source (e.g. hyperglycaemia, varicocele)
• Occupational (industrial, heat)
• Iatrogenic (radiation therapy)

Question 18

+ How can exposure of sperm mitochondria to excess ROS cause infertility?

Answer 18

• Damage to mDNA
• Decreased ATP production
• Impaired motility
• Compounded by effect of lipid peroxidation

Question 19

+ List 2 key lifestyle effects heavily associated with increased DNA fragmentation

Answer 19

• Smoking
• Obesity

Question 20

What is TESA

Answer 20

• Testicular sperm aspiration, allowing surgical collection of the sample
• If you have no, or extremely low numbers of, sperm in your semen which means you can’t have a standard fertility treatment, you may be able to have sperm collected surgically

Question 21

Findings of experiment into migration efficiency of goat sperm in cervical mucus:

Answer 21

• High migration efficiency (i.e. vanguard) of sperm in vitro was able to predict migration efficiency in vivo (i.e. progression to oviduct)
• It was also able to predict high penetration rate in IVF