title: Ultrastructure of human oocytes after in vitro maturation.
abstract: OBJECTIVE
  How does the ultrastructure of human oocytes matured in vitro compare with oocytes collected from women after full hormonal stimulation?
  
  
  RESULTS
  The ultrastructure of human oocytes matured in vitro is largely, but not entirely, similar to those matured in vivo.
  
  
  BACKGROUND
  Embryos derived from in vitro-matured oocytes often have limited developmental potential, possibly as an effect of inappropriate in vitro maturation (IVM) conditions. Transmission electron microscopy (TEM) is a valuable research tool to compare in vivo and in vitro matured oocytes. However, previous studies on the ultrastructure of human IVM oocytes were done with inadequate material or inappropriate IVM conditions, and have limited significance.
  
  
  METHODS
  Immature cumulus cell-enclosed oocytes, retrieved from mid-sized antral follicles of women requiring IVM treatment, were matured in vitro for 30 h. No leftover germinal vesicle-stage oocytes collected from fully stimulated cycles were used. Control in vivo matured oocytes were obtained from age-matched women undergoing full ovarian stimulation. In vitro and in vivo matured oocytes were analysed by TEM and compared according to previously established morphometric criteria of oocyte quality.
  
  
  RESULTS
  All oocytes had normal ooplasm showing uniform distribution of organelles. Mitochondrial morphology appeared similar between the maturation conditions. Cortical granules were found typically stratified in a single, mostly continuous row just beneath the ooplasm in all oocytes. Microvilli were well preserved after IVM. Vacuoles were only occasionally found in all oocytes and, if present, they were frequently associated with lysosomes. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates and mitochondria-vesicles (MV) complexes were commonly found in in vivo matured oocytes. However, large MV complexes partially replaced M-SER aggregates in IVM oocytes.
  
  
  CONCLUSIONS
  As a note of caution it should be noticed that, being laborious and technically demanding, TEM cannot be applied to a large number of samples in a single investigation. Therefore, our data require further independent confirmation.
  
  
  CONCLUSIONS
  Our data suggests the notion that TEM remains a valuable research tool that can also offer quantitative data if associated with morphometric criteria of evaluation. Therefore, it can be adopted to test pre-clinically the performance of novel in vitro systems that are demanded to make oocytes IVM more successful in the human.
  
  
  METHODS
  Not applicable.
  
  
  BACKGROUND
  This study was independently funded by Biogenesi Reproductive Medicine Centre, Monza, Italy. All authors declare that their participation in the study did not involve factual or potential conflicts of interests.
authors.affiliation: Biogenesi Reproductive Medicine Centre, Monza, Italy coticchio.biogenesi@grupposandonato.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Coticchio
authors.affiliation: Biogenesi Reproductive Medicine Centre, Monza, Italy.
authors.forename: Mariabeatrice
authors.initials: M
authors.lastname: Dal Canto
authors.affiliation: Biogenesi Reproductive Medicine Centre, Monza, Italy.
authors.forename: Rubens
authors.initials: R
authors.lastname: Fadini
authors.affiliation: Biogenesi Reproductive Medicine Centre, Monza, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Mignini Renzini
authors.affiliation: Biogenesi Reproductive Medicine Centre, Monza, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Guglielmo
authors.affiliation: Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, University 'La Sapienza', Rome, Italy.
authors.forename: Selenia
authors.initials: S
authors.lastname: Miglietta
authors.affiliation: Department of Life, Health and Environmental Sciences, University of ĹAquila, L'Aquila, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Palmerini
authors.affiliation: Department of Life, Health and Environmental Sciences, University of ĹAquila, L'Aquila, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Macchiarelli
authors.affiliation: Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, University 'La Sapienza', Rome, Italy.
authors.forename: Stefania Annarita
authors.initials: SA
authors.lastname: Nottola
mesh_terms: D000328:Adult; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D054885:Cumulus Cells / Q000187:drug effects / Q000648:ultrastructure*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000648:ultrastructure; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006801:Humans; D059471:In Vitro Oocyte Maturation Techniques / Q000379:methods*; D008247:Lysosomes / Q000187:drug effects / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000187:drug effects / Q000648:ultrastructure; D009865:Oocytes / Q000187:drug effects / Q000648:ultrastructure*; D009866:Oogenesis / Q000187:drug effects / Q000235:genetics; D010062:Ovulation Induction / Q000379:methods*; D014617:Vacuoles / Q000187:drug effects / Q000648:ultrastructure
chemical_list: D006063:Chorionic Gonadotropin; D005640:Follicle Stimulating Hormone
keywords: cortical granules; endoplasmic reticulum; in vitro fertilization; in vitro maturation; mitochondria; oocytes; ultrastructure