Flashcards in embryo formation and metabolism Deck (28)
at what stage does the activation of the embryonic genome in humans occur?
four cell stage
at what stage foes compaction occur?
16-32 cell stage
what is compaction dependent on?
what drives compaction?
E-cadherin (a transmembrane cell-cell adhesion molecule)
when and where is E-cadherin expressed?
expressed from early cleavage but relocated to regions of cell to cell contact at the time of compaction, probably through the activation of Pk-C
what are some cell adhesion molecules/cell junction components in the pre-implantation blastocyst?
when is JAM-1 staining detected?
in all pre-compact eight cell embryos
at the onset of compaction all eight cell embryos also revealed intense JAM1 staining at the apical poles (outward facing) of the blastomeres as well as contact sited.
what is blastocyst formation dependent upon?
--> polarised distribution of Na/K - ATPase confined to the basolateral membrane domain of the trophectoderm.
-->this establishes a trans-trophoectoderm ion gradient that facilitates movement of water across the epithelium facilitated by the presence of both apical and basolateral AQPs.
--> these events combined with the establishment of a trophectoderm tight junctional seal to prevent loss of fluid out of the embryo through parcellular routes results in the expansion of the embryo and the formation of the blastocyst
how's early development regulated?
embryo and uterus produce a large amount of different growth factors or cytokines (e.g. - embryo: IGF-1, IGFII, TGF-alfa, TGF-beta(1-3), FGF-4, IL-1alpha, IL-1beta, IL-6, IL-7)
embryos express growth factor receptors
paracrine and endocrine mechanisms are involved in supporting early stage embryo growth and development
what happens to ATP production and the % of ATP from oxidation as the embryo develops?
as number of cells increases ATP production increases
As embryo develops the percentage of ATP from oxidation decreases
around the time of compaction what happens to the embryos metabolism?
it switches from dependence on the TCA cycle to a metabolism based on glycolysis.
why is glucose needed in the embryo?
provides the pentose moieties for nucleic acid synthesis and is required for phospholipids and non-essential amino acids biosynthesis.
what glucose transporter genes are expressed in the oocyte?
what glucose transporter genes are expressed at the 8 cell stage?
what glucose transporter genes are expressed at the blastocyst stage?
what stage embryo consumes the most oxygen?
how does oxygen affect embryo development ?
20% compared with 5%
20% leads to a decrease in glucose uptake
20% leads to a decreased blastocyst formation and decrease in cell number per blastocyst
how does glutamine affect human pre-impantation embryo development?
it improves it
increase the morula and blastocyst formation
what are the outcomes of fertilisation?
- successful preimplantation embryo development
- two cell arrest - occurs primarily in mouse (cell shrinkage and lysis; possible autophagic death, presence of midline cellular fragmentation, complete embryo fragmentation)
- abnormal embryo development - occurs primarily in human (fragmentation without loss of blastomeres; possible caspase independent, possible oncosis, embryo arrest, fragmentation with loss of blastomeres; caspase dependent process, possible apoptosis)
what is a good indicator of good and poor embryo quality?
the ratio of ICM:TE is an important indicator of embryo quality
high number of apoptotic cells is an indicator of poor quality embryos
do faster or slower embryos have higher ICM:TE ratio?
faster embryos have significantly higher ICM:TE ration
faster embryos have significantly more inner cell mass cells and subsequently a higher total cell number
developmental kinetics of faster embryos
carbohydrate metabolism of faster embryos
amino acid metabolism of faster embryos
developmental kinetics - increased blastocyst number, increased fatal development per implantation
carbohydrate metabolism - increased inner cell mass, increased glucose consumption, decreased lactate production, decreased glycolytic rate.
amino acid metabolism - increase aspirate consumption, glutamate consumption instead of production.
faster embryos consume more aspirate and have a lower glycolytic rate
slower embryos produce glutamate
how do fast and slow embryos differ in glucose and lactate production/consumption?
faster embryos consume more glucose and produce more lactate
what is time lapse microscopy TLM?
it captures images over time and provides a combination of morphological, dynamic and quantitative information about developmental events.
what are the benefits of TLM?
you can see the time taken to for 2 cell embryo (first cleavage
you can see regularity in duration of cell cycles
you can see morphology of embryos and fragmentation
you do not need to open incubators to monitor embryo development, reduces perturbation of embryo enviroment
what are the pros of metabolic analysis?
- non invasive
- easy to use routinely
- is it cost effective??
- no ethical questions raised
- independent of other parameters (morphology)
what metabolic factors may for the basis of a non invasive test of embryo viability?
- glucose, pyruvate, amino acids, other sugars, oxygen
- lactate, ammonium, amino acids, enzymes e.g. LDH, sHLA-G, HOXA2- regulator, PAF, metabolomics/proteomics, other peptides and factors