Quantitative and qualitative changes of mitochondria in human preimplantation embryos

Abstract

The mitochondrial respiratory function of human embryos developed along with embryonic growth although the copy numbers of mtDNA decreased transiently before blastulation. OCRs increased toward the morula stage ahead of an increase of mtDNA at the time of blastulation. Data regarding changes in mitochondrial function and mtDNA copy number during preimplantation development of human embryos will be useful for the development of ideal culture media.

Mitochondrial Heterogeneity: Evaluating Mitochondrial Subpopulation Dynamics in Stem Cells

“…In undifferentiated embryonic stem cells (ESCs), mitochondria are characterized as having a globular shape, with few defined cristae and limited oxidative capacity [21]. This ovoid mitochondrial morphology and cristae arrangement are rather striking [21, 22] and also observed in oocytes (Figure 1), as well as in the inner cell mass of blastocysts—the originating source for ESCs [23]. The low matrix and cristae density are associated with slowly respiring state IV mitochondria, as compared to fast respiring state III mitochondria, which have a higher matrix and cristae density and a morphologically “condensed” ultrastructure [24–26].…”

The role of mitochondria in the female germline: Implications to fertility and inheritance of mitochondrial diseases

“…However, even at the blastocyst stage, mitochondrial activation, which involves elongated organelles with well-developed cristae structures and mtDNA replication, seems to be restricted to TE (Van Blerkom, 2008;St John et al, 2010;St John, 2014;Hashimoto et al, 2017). Thus, there is evidence that mitochondria are in an inactive stage in the ICM, or at least in the preimplantation epiblast that will give rise to the embryo proper (Hashimoto et al, 2017). Further commitment and differentiation of the epiblast into specific cell types (e.g., somatic tissues) is also accompanied by an intrinsic mitochondrial remodeling, whereas mitochondria remain undeveloped in the germline (Wassarman and Josefowicz, 1978;Jansen and De Boer, 1998;Motta et al, 2000).…”

“…During pre‐implantation development, mitochondria also play a significant role in providing most of the energy as, at least at the earliest stages, the embryo lacks some of the enzymes needed to drive glycolysis (Su et al, ; Leese, ). Yet, mitochondria (OXPHOS dependent) account for only ∼30% of the oxygen consumed by cleavage‐stage embryos (Trimarchi et al, ; Leese, ; Hashimoto et al, ). This finding supports the importance of OXPHOS‐independent oxygen consumption, thereby maintaining the embryo in a metabolically quiet state to protect it from oxidative damage (Leese, ).…”

“…Therefore, as shown in the mouse (Wai et al, ), it is assumed that oocytes must contain a minimum content of mtDNA to support early development (Chiaratti and Meirelles, ). Yet, the increased levels of mtDNA in TE may reflect premature mitochondrial activation (Chiaratti et al, ; St John et al, ; Hashimoto et al, ), with possible consequences to ATP and ROS generation (Van Blerkom, ; Leese, ). In addition, this increase may be a consequence of cellular stress response, as blastocysts with chromosomal abnormalities contain increased mtDNA content in TE (Tan et al, ).…”

Renaissance, reinvention, or rhetoric: mitochondria in reproductive medicine 2017

“…Complementing measures of mtDNA with parallel assessments of mitochondrial activity is a rarity amongst the papers attempting to resolve the ongoing controversy (having a distinctly molecular-centric rather than physiological content, with rare exceptions) [6].…”