Trophoblast invasion

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Trophoblast invasion

• Dr Ian Stewart
• i.stewart_at_abdn.ac.uk

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Trophoblast invasive?

• Is trophoblast invasive?
• Is placentation an invasive process?
• Place blastocyst under kidney capsule and
  trophoblast will pervade throughout kidney (Kirby
  1963)
• Evidence that trophoblast invasive?
• Similar to invasive malignant cells?
• Hazardous to mother?
• Choriocarcinoma malignant trophoblast

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Trophoblast invasion occurs?

• At implantation in human pregnancy yes
• Interstitial implantation
• At implantation in rodents no
• Eccentric implantation
• Epithelium breaks down around blastocyst

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Trophoblast invasion occurs?

• During placentation?
• In humans no
• In rodents no
• Maternal placenta (and uterus) expands as foetal
  placenta grows
• Boundary forms between maternal and foetal
  placenta but invasion does not occur
• There is attachment but not invasion

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However!

• Endovascular trophoblast
• Invades along inside of arterial blood vessels
  supplying placenta
• Interstitial trophoblast
• Invades between cells of maternal placenta
  (decidua)
• Invasion limited yes
• Purpose - ?

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Endovascular trophoblast
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Interstitial trophoblast
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Invasive trophoblast

• Endovascular
• Human Yes
• Macaque - Yes
• Mouse No
• Rat Yes
• Field vole - No
• Hamster - Yes

• Interstitial
• Human Yes
• Macaque - Yes
• Mouse No
• Rat No
• Field vole - Yes
• Hamster - No

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Source of invasive trophoblast cells
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Endovascular trophoblast

• Arises from trophoblast at maternal-trophoblast
  interface trophoblast not involved in blood
  barrier
• Lines (spiral) arteries feeding placenta
• Does not extend beyond uterine wall
• Erodes arterial epithelium
• Erodes arterial smooth muscle
• Important in maintaining blood supply to placenta
  even in cardiovascular distress?

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Interstitial trophoblast

• Arises from trophoblast at maternal-trophoblast
  interface trophoblast not involved in blood
  barrier
• Very large cells
• Very active cells
• Function?
• A mystery to be resolved

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Interstitial trophoblast very active cells