Background: Approximately 20% of recovered oocytes are immature and discarded in intracytoplasmic sperm injection (ICSI) procedures. These oocytes represent a potential resource for both clinical and basic science application.
Objective: The aim of this study was to evaluate the ultrastructure architecture of in vitro matured human oocytes using transmission electron microscopy (TEM).
Materials and methods: A total of 204 immature oocytes from infertile patients who underwent ICSI cycles were included in this prospective study. Immature oocytes were divided into two groups: (i) GV oocytes (n = 101); and (ii) MI oocytes (n = 103). Supernumerary fresh in vivo matured oocytes (n = 10) were used as control.
Results: The rates of maturations were 61.38% for GV and 73.78% for MI oocytes in IVM medium (P = 0.07). However, the rate of oocyte arrest was significant between groups (P <0 .05). Ultrastructurally; in vitro and in vivo matured oocytes appeared round, with a homogeneous cytoplasm, an intact oolemma and an intact zona pellucida. However, immature oocytes indicated numerous large mitochondria-vesicle complexes (M-VC).
Conclusions: Ultrastructural changes of M-VC in IVM groups emphasize the need for further research in order to refine culture conditions and improve the implantation rate of in-vitro matured oocytes.
Keywords: Germinal Vesicle Oocytes; In vitro Maturation; Metaphase-I Oocytes; Ultrastructure.