The researcher point of view: evaluating follicle quality and chances to pregnancy

The researcher point of view:
evaluating follicle quality and
chances to pregnancy
David Albertini
Kansas University Medical Center
Kansas City, USA
Oocyte Qualiy As A Developmental
Continuum
Ovarian Development
Ovulation
MEIOSIS-GENES-IMPRINTS
Transmission of genetic errors….?
Embryogenesis
MITOSIS-GENES-EPIGENES
Determinants of OQ
Epi/genetic Integrity
• Chromatin and
Chromosome-based
• DNA damage
response(DDR) is active
• Aneuploidy is common
Metabolic Support
• Derived from somatic cells
via direct contact
• Negatively impacted by FSH
and LH
• Sustains meiotic cell cycle
Repeated COH causes a progressive decrease in mouse
oocyte ATP content
TZP density is sensitive
to FSH/LH stimulation
Less contact
Less ATP
Both methods lead to oocyte chromatin condensation
Control
Slow
Freeze
Vitrified
DNA damage incurred by cryo can
be repaired
Bovine strips
Slow freeze
24 hr post thaw
culture
The DDR is initiated and completed in bovine follicles contained
within cultured ovarian strips after slow freeze but
NOT vitrification.
Is metabolic recovery influenced by the type of freezing used??
Lesson 1:Compromised
metabolism leads to
compromised function
How does cryopreservation and
subsequent culture impact the
follicle’s ability to maintain oocyte
metabolism?
The dark side of aerobic metabolism
• Oxidative stress and the preantral follicle
• Oxidative stress and the well-vascularized
antral follicle
• Intrinsic defense mechanisms
• Extrinsic manipulations to foster follicle
viability and oogenesis
Coupling Oxidative Stress to Survival
ROS
ATM
PAR/LKBp
kinase
AMPKp
AUTOPHAGY
TSC2
mTOR
Autophagy is a good thing
• Involves breakdown of organelles, such as
peroxisomes, lysosomes, mitochondria for
storage and recycling of membrane and
protein precursors.
• Is probably part of an intrinsic pathway to
maintain oocytes.
• Is pharmacologically accessible
Lesson 2: Metabolic support
from the follicle requires
maintenance of TZPs
As manifestations of granulosa cell
polarity designed to serve and
protect the oocyte from genetic or
epigenetic damage sustained during
cryo and/or culture
The researchers perspective
• Minimizing gonadotropin exposure at all costs
will maintain follicle in an oocentrically
favorable environment-in vivo or in vitro
• Counteracting oxidative stress continues to be
essential via exposure to reducing equivalents
or ideally, shifting metabolism away from
OX/PHOS
• We should soon be able to manipulate ovarian
tissue survival pharmacologically
Take Home Message
• Frozen-thawed ovarian tissues undergo stress
adaptive changes that will influence follicle
survival and function following transplantation
or culture.
• The challenge ahead is to minimize, rectify,
and/or rehabilitate follicular function and in so
doing support oogenesis that results in the
production of developmentally competent
and genetically stable oocytes.
The road to fertility preservation
Oocyte
Cryopreservation
P63, c-abl, imantinib
PTEN/AKT/ROS
Plausible Mechanisms
for Preventing or
Ameliorating Damage
gammaH2AX/IR
Cytoxan/DOX
Chemo and IR-induced
DNA Damage
Ovarian Tissue
Cryopreservation
Oocyte and Somatic
Cell DNA Damage