An efficient method for in vitro fertilization in rabbits

In vivo and in vitro maturation of rabbit oocytes differently affects the gene expression profile, mitochondrial distribution, apoptosis and early embryo development

In vivo-matured cumulus–oocyte complexes are valuable models in which to assess potential biomarkers of rabbit oocyte quality that contribute to enhanced IVM systems. In the present study we compared some gene markers of oocytes and cumulus cells (CCs) from immature, in vivo-matured and IVM oocytes. Moreover, apoptosis in CCs, nuclear maturation, mitochondrial reallocation and the developmental potential of oocytes after IVF were assessed. In relation to cumulus expansion, gene expression of gap junction protein, alpha 1, 43 kDa (Gja1) and prostaglandin-endoperoxide synthase 2 (Ptgs2) was significantly lower in CCs after in vivo maturation than IVM. In addition, there were differences in gene expression after in vivo maturation versus IVM in both oocytes and CCs for genes related to cell cycle regulation and apoptosis (V-Akt murine thymoma viral oncogene homologue 1 (Akt1), tumour protein 53 (Tp53), caspase 3, apoptosis-related cysteine protease (Casp3)), oxidative response (superoxide dismutase 2, mitochondrial (Sod2)) and metabolism (glucose-6-phosphate dehydrogenase (G6pd), glyceraldehyde-3-phosphate dehydrogenase (Gapdh)). In vivo-matured CCs had a lower apoptosis rate than IVM and immature CCs. Meiotic progression, mitochondrial migration to the periphery and developmental competence were higher for in vivo-matured than IVM oocytes. In conclusion, differences in oocyte developmental capacity after IVM or in vivo maturation are accompanied by significant changes in transcript abundance in oocytes and their surrounding CCs, meiotic rate, mitochondrial distribution and apoptotic index. Some of the genes investigated, such as Gja1, could be potential biomarkers for oocyte developmental competence in the rabbit model, helping improve in vitro culture systems in these species.

Fertilization studies and assisted fertilization in mammals: their development and future

Studies of mammalian fertilization progressed very slowly in the beginning because of difficulties in obtaining a large quantity of fully mature eggs at one time. With progression of techniques to collect and handle eggs and spermatozoa, research in mammalian fertilization advanced rapidly. Today, far more papers are published on mammalian gametes and fertilization than those of all other animals combined. The development of assisted fertilization and related technologies revolutionized basic research as well as human reproductive medicine and animal husbandry. Reproduction is fundamental to human and animal lives. The author lists a few subjects of his personal interest for further development of basic and applied research of gametes and fertilization. Each reader will probably have more exciting subjects of future investigation.

Normal developmental competence to the blastocyst stage is preserved in rabbit ovarian tissue following cryopreservation and autografting to the mesometrium

The aim of the present study was to evaluate mesometrial autotransplantation of frozen–thawed ovarian tissue in the adult rabbit and investigate the developmental competence of oocytes retrieved from grafts by in vitro maturation, fertilisation and blastocyst formation. Twenty-five rabbits were divided into control, fresh tissue transplantation and frozen–thawed tissue transplantation groups. Rabbits were stimulated with follicle-stimulating hormone (FSH) and oocytes were retrieved 3 months after transplantation. Oocytes matured in vivo or in vitro were then fertilised by conventional in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI), followed by observation and evaluation of fertilisation and blastocyst formation rates. No significant differences were found in the percentage of oocytes, maturation, fertilisation, cleavage and blastocyst formation among the three groups. Significantly higher fertilisation rates of in vitro-matured (IVM) oocytes were observed with ICSI compared with IVF in each group (81.1% v. 58.5%, 79.2% v. 59.6% and 80.4% v. 56.0% in the control, fresh tissue transplantation and frozen–thawed tissue transplantation groups, respectively). The blastocyst formation rate of IVM oocytes was significantly lower than that of in vivo-matured oocytes in each group (25.5% v. 65.7%, 22.4% v. 61.8% and 28.9% v. 63.0% in the control, fresh tissue transplantation and frozen–thawed tissue transplantation groups, respectively). In concusion, the mesometrium is a promising site for ovarian autografts in the rabbit. Oocytes retrieved from mesometrial grafts can develop to the blastocyst stage.

Analysis of gene expression in rabbit nuclear transfer embryos: Use of single-embryo mRNA differential display

Lack of or abnormal expression of developmentally important genes is believed to hamper early development of the nuclear transfer (NT) embryo. To identify stage-specific genes in rabbit NT embryo development, mRNA differential display was used to compare the mRNA content of rabbit NT embryos at different developmental stages, from Metaphase II oocytes to 8-16-cell stage embryos. Thirty-four zygotic transcripts, which abruptly appeared at the 8-16-cell stage in rabbit NT embryos, were isolated; 11 of these were potential novel genes with no matches in the current databases. Of the remaining 23, 12 were matched with established sequence tags with functions uncharacterized and the other 11 were homologous to those in the European Molecular Biology Laboratory (EMBL) and GenBank databases. The differential expression of eight of the 34 amplicons were confirmed by reverse Northern blotting, and four positive clones were validated. Previous studies and present data indicated that these three genes were probably related to preimplantation rabbit embryo development.