Expression of interleukin-1 system genes in human gametes

There is considerable evidence that the interleukin-1 (IL-1) system plays a n important role in ovarian and testicular physiology, implantation, and ot her reproductive events. Human embryos express IL-1 beta, IL-1 receptor typ e I (IL-1 Rtl), and IL-1 receptor antagonist (IL-1 RA) at both the mRNA and protein levels. The presence of IL-1 alpha and IL-1 beta in oocyte-conditi oned media and on the surface of human oocytes suggests that these cells ma y also produce this cytokine; however, whether the IL-1 system gene product s are present as stable mRNAs in human gametes (oocytes and spermatozoa) ha s not yet been demonstrated. We used stringent cell separation techniques combined with reverse transcri ption-polymerase chain reaction to investigate the expression of various IL -1 system genes (IL-1 alpha, IL-1 beta, IL1Rtl, and IL-1RA) in human gamete s and cumulus cells. Our results indicate that freshly isolated cumulus cel ls express all these IL-1 system components. On the other hand, IL-1 alpha, IL-1 beta, and IL-1Rtl mRNAs were not found in either unfertilized or fert ilized human oocytes, and a very few metaphase II human oocytes had transcr ipts for either secreted (10%) or intracellular (17%) IL-1RA. Mature sperma tozoa did not contain mRNA for any of the of the IL-1 system components. Th e absence of informational RNA for the IL-l system components in human unfe rtilized and polyploid oocytes and fresh immature oocytes suggests that mat ernal transcripts for these genes do not contribute to early embryo develop ment. The presence of IL-1 components at the protein level in human oocytes may be due to binding of IL-1 produced by cumulus cells or other cell type s, or to prior intrafollicle transcription and translation. Likewise, IL-1 system components do not appear to have a physiological role in mature sper matozoa since none of these components are present at the mRNA or protein l evels, and important functional parameters such as motility and acrosome re action appear not to be affected by IL-1 beta in vitro. However, the abunda nt expression of IL-1 alpha, IL-1 beta, the IL-1Rtl, and its antagonist IL- 1RA by human cumulus cells provides further evidence that the IL-1 system p lays a role in human ovarian physiology.