title: Effect of treating induced mitochondrial damage on embryonic development and epigenesis.
abstract: Germinal vesicle transplantation (GVT) has been proposed as a possible treatment to correct age-related oocyte aneuploidy caused by dysfunctional ooplasm. How healthy ooplasm regulates normal meiosis and subsequent development has yet to be elucidated, but impaired mitochondrial metabolism may be attributable to incomplete segregation of the oocyte chromosomes. In the present study, after ooplasmic mitochondrial damage by photoirradiating chloromethyl-X-rosamine, examination of the oocyte nuclei's ability to survive after transfer into healthy ooplasts was performed. To assess their fertilizability and potential for development, GVT oocytes were fertilized by intracytoplasmic sperm injection (ICSI) and transferred to foster mice. Condition of the offspring at birth was assessed, and epigenetic analysis was performed. Photosensitization consistently inhibited oocyte maturation. However, after GVT of photosensitized nuclei into healthy ooplasts, 67.2% were reconstituted, and 76.2% of these matured normally, with an overall rate of 51.2%, much higher than that (6.0%) in the mitochondrially injured oocytes. After ICSI, 65.8% (52/79) of GVT oocytes were fertilized normally, and 21.1% (11/52) eventually reached the blastocyst stage. The transfer of 132 two-cell GVT embryos into the oviducts of pseudopregnant females resulted in 17 apparently healthy live offspring. For some key developmental genes, a high level of expression was identified in the GVT and "rescue"-derived fetal adnexa. Thus, one can induce in oocyte mitochondria a photosensitization-based type of damage, which consistently inhibits GV breakdown, meiotic spindle formation, chromosomal segregation, and polar body extrusion. Germinal vesicle transplanted and rescued oocytes were able to undergo maturation, fertilization, and embryonic cleavage and, ultimately, to develop to term. This approach may provide a model with which to study the age-related ooplasmic dysfunction seen in human oocytes.
authors.affiliation: The Center for Reproductive Medicine and Infertility, Weill Medical College of Cornell University, New York, New York 10021, USA.
authors.forename: Takumi
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Queenie V
authors.initials: QV
authors.lastname: Neri
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Katagiri
authors.forename: Zev
authors.initials: Z
authors.lastname: Rosenwaks
authors.forename: Gianpiero D
authors.initials: GD
authors.lastname: Palermo
mesh_terms: D000818:Animals; D016922:Cellular Senescence / Q000502:physiology / Q000528:radiation effects; D003593:Cytoplasm / Q000502:physiology; D004249:DNA Damage / Q000235:genetics; D004624:Embryo Transfer; D047108:Embryonic Development / Q000235:genetics / Q000502:physiology*; D044127:Epigenesis, Genetic; D005260:Female; D005298:Fertility / Q000502:physiology* / Q000528:radiation effects; D005306:Fertilization / Q000502:physiology; D005307:Fertilization in Vitro / Q000379:methods; D005456:Fluorescent Dyes; D008027:Light; D008297:Male; D008540:Meiosis / Q000502:physiology*; D051379:Mice; D008928:Mitochondria / Q000528:radiation effects; D053652:Nuclear Transfer Techniques; D009865:Oocytes / Q000502:physiology* / Q000528:radiation effects; D009930:Organic Chemicals; D017319:Photosensitizing Agents; D011247:Pregnancy; D020554:Sperm Injections, Intracytoplasmic
chemical_list: D005456:Fluorescent Dyes; D009930:Organic Chemicals; D017319:Photosensitizing Agents; C107472:red dye CMXRos