Currently, in vitro fertilization (IVF) is one of the most common approaches towards treating infertility. However, the success of this approach is still relatively low an the outcome of the IVF procedure is challenging to predict. At present, there is no highly successful marker that could reliably predict the pregnancy outcome in the process of assisted reproduction (AR). Currently, multiple embryo transfers are performed to warrant a successful pregnancy outcome, but this commonly results in multiple pregnancies, narrowing the feasibility of this method for a subset of couples affected by infertility. Recently IVF cycles with single-embryo transfers have become an option of interest in AR approaches. Such cycles, however, are significantly less successful and for this reason, there is an incentive to improve the pregnancy chance per IVF cycle by incorporating more criteria for selection of the embryo with the highest implantation potential. Gene expression in follicular cells, including granulosa cells (GC) and cumulus cells (CC) has previously been considered as a tool to predict the quality of the oocytes in several studies in addition to assessing the morphologic criteria of the embryos. Gene expression estimation in these cells, especially of the CC population, carries along several benefits as their harvesting is non-invasive, they are in direct contact with the oocyte and are usually discarded during the process of intracytoplasmatic sperm injection procedure (ICSI), making them any easily accessible surrogate tissue for gene expression analyses. Considering that several studies reporting various rates of success in prediction of AR cycle outcome with expression as a biomarker have been published, we attempted to perform the largest study of global gene expression alterations in finding novel biomarkers to outcome of in- vitro fertilization, which would encompass discovery of new biomarker genes and subsequent confirmational study of the selected biomarker set on an independent validation group. In this experiments 4 samples were hybridized twice, to allow for inspection of technical validity of microarray experiments.
Overall design
Whole genome expression profiling was performed on 64 samples - we have included three different outcomes of IVF, including cases where fertilization was unsuccessful (Unfertilized), those where fertilization was attained but without successful pregnancy (NonPregnant) and those resulting in successful pregnancy outcome (Pregnant). Additionally, we have investigated the extent of expression alterations in two different populations of follicular cells, in order to select the tissue of choice that would have the highest potential for predicting outcome of the IVF process.
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