Preimplantation embryology

In order to improve assisted fertilization in humans it is important to elucidate the mechanisms of control of growth and development in the early pre-embryo. Increasing evidence shows that growth factors are of importance for such control mechanisms. As platelet-derived growth factor (PDGF) has been shown to enhance growth in a number of tissues, it may also be important in human pre-embryo development. PDGF acts as a dimer (AA, BB or AB) through its receptors: alpha alpha, beta beta and alpha beta. In order to study the role of PDGF and its receptors, we have used reverse transcription-polymerase chain reaction (RT-PCR) to examine the presence of transcripts in human pre-embryos that were surplus from the in-vitro fertilization treatment of infertile couples. Transcripts for PDGF A were present in the oocyte, 8-cell, morula and blastocyst stages but not in the 4-cell stage. Transcripts for PDGF B were not detected at any stage. PDGF receptor (PDGFR)-alpha transcripts were found in the 4-cell, 8-cell and blastocyst stages but not in the oocyte or morula stages. Transcripts for PDGFR-beta were detected from the 8-cell, morula and blastocyst stages but not in the oocyte or 4-cell stages. These results show that mRNA synthesis of both PDGF A and the two receptor subunits alpha and beta takes place from the 8-cell stage onwards, suggesting an autostimulatory pathway as a possible mechanism for growth factors during pre-embryo development.