INTRODUCTION

The oocyte cytoplasm plays a crucial role in the different steps of fertilization and embryo development. It is known that embryo quality is associated to its ability to implant and, consequently, to achieve pregnancy. There are several conditions that diminish oocyte quality, leading to lower implantation and pregnancy rates. Recently, a new twchique has been developed named “cytoplasm transfer”, with the objective of enhancing oocyte quality by transferring the cytoplasm extracted from a excellent quality “donator” oocyte to na oocyte having impaired cytoplasmic quality. In this way, the global oocyte quality get better, enhancing implantation and pregnancy rates.

Cytoplasmic components are very important to determine the oocyte quality. In some cases, during oocyte retrieval we can already observe in the microscope that the oocyte has a bad quality. Those altrations include abnormal morphology, cytoplasm fragmentation, granulosity, vacuolization and darkening. These oocytes generate bad quality embyos in general. Recovering incompetent oocyte potential for development may be achieved by alteration of their molecular state, using selected organelle injection or transferring normal cytoplasm without the nuclear material. In this last case, the receptor oocyte becomes hybrid from a cytoplasmic point of view and, by this procedure we can, hypothetically, partiallly restore the normal physiological state.

ADVANCE