How to repair the oocyte and zygote?

The supply of human oocytes is very limited. This restricts not only certain assisted reproduction procedures in IVF clinics where recipients wait for oocytes from donors, but also development of some promising approaches, like therapeutic nuclear transfer with subsequent derivation of patient compatible embryonic stem cells. Moreover, in some patients, collected oocytes exhibit certain specific defects, and logically, we can expect that after fertilization, the embryos arising from these defective oocytes may not develop or that their development might eventually be compromised. For this reason, an increased effort to determine how to repair oocytes is evident in the literature. In general, abnormalities (defects) can be detected in different oocyte components, the zona pellucida, cytoplasm, nucleus (chromosomes) and nucleolus. Whereas defects of a nuclear component are impossible (nuclear DNA) or very hard to repair (nucleolus), zona pellucida abnormalities and cytoplasm defects (for example, if containing mutated mitochondrial DNA, mtDNA) can be repaired in some cases with the help of micromanipulation schemes. In the present article, we will briefly outline the current methodological approaches that can be used to repair the oocyte or one-cell stage embryo.