Temporal expression of platelet-derived growth factor (PDGF)-A and its receptor in human preimplantation embryos

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.