C.W. Elsner

Immunosuppression supports implantation of zona pellucida dissected human embryos

The effect of low dose immunosuppression with methylprednisolone during the first 4 days after oocyte retrieval on potential immune cell invasion of partially zona dissected embryos in utero was investigated in alternate in vitro fertilization patients (n = 32). The incidence of pregnancy was significantly higher in patients receiving methylprednisolone (7 of 18, 39%) than in control patients (1 of 14, 7%). Twenty-eight percent (11 of 39) of the embryos replaced in the corticosteroid treated patients implanted, whereas only 7% (2 of 31) of embryos in control patients had a fetal heart beat. There were no side effects reported in any of the patients receiving corticosteroids. It can be concluded that methylprednisolone supports implantation of embryos with small holes in their zonae. However, the actual mechanisms of corticosteroid support on the interaction between immune cells and micromanipulated embryos are not well understood.

Coculture of Human Zygotes on Fetal Bovine Reproductive Tract Cells

When early cleaved human embryos are kept in culture, only one in four can be expected to develop into fully expanded blastocysts.1 Alternatively, only 1% to 12% of them will implant and develop into full-term babies, when replaced into the uterus or fallopian tube before the third cleavage division commences.2,3 Embryonic wastage following assisted reproduction can only in part be explained by an increased incidence of genetic abnormalities or loss at the time of replacement. Other more esoteric factors, like a reduced receptivity of the endometrium in stimulated menstrual cycles, probably play an important role as well.

Partial Zona Dissection for Enhancement of Sperm Passage through the Zona Pellucida

Fertilization in mammals occurs in a number of intricate steps, culminating in the union of male and female genomes. Spermatozoa capacitate prior to sperm receptor binding on the zona pellucida (ZP), where the acrosome reaction is induced. Following ZP penetration membrane fusion occurs, triggering oocyte activation. This leads to the release of cortical granules and the zona reaction, causing a slow, but usually permanent block to polyspermy. Changes in the oolemma may initiate a fast, but often weak and temporary block, as well. Following decondensation and syngamy, the fertilization process is completed with the formation of a genetically new conceptus at the two-cell stage.1 Pathological changes may occur during any of these steps, and fertilization may either be discontinued or result in a genetically abnormal embryo. Discontinued fertilization is common during human in vitro fertilization (IVF), especially when there is a sperm disorder. Although the methods for microsurgical fertilization proposed in recent years only alleviate abnormal ZP-binding, ZP-penetration, and/or membrane fusion, they may be welcome additions to IVF. Basically, three methods, each with its own advantages and disadvantages, have been proposed: