TUMOR-NECROSIS-FACTOR-ALPHA GENE-EXPRESSION IN MOUSE OOCYTES AND FOLLICULAR CELLS

ovarian cells that transcribe and translate the gene for tumor necrosis factor alpha (TNFalpha) were identified in the adult cyclic mouse by using in situ hybridization and immunocytochemistry. TNFalpha mRNA was observed in >97% and protein was contained in -53% of the oocytes of healthy follicles with two or more layers of granulosa cells, but neither was detectable in oocytes of primordial follicles and follicles with a single layer of granulosa cells. In early atretic follicles, only 13% contained TNFalpha protein and 40% contained TNFalpha mRNA. In late stages of atresia, intense immunoreactive TNFalpha was observed in all of the oocytes, but TNFalpha mRNA was present in only 13%. In approximately 85% of follicles, theca and/or granulosa cells exhibited TNFalpha mRNA hybridization signals. Macrophage-like cells within the interstitium were positive for TNFalpha mRNA and protein. In corpora lutea, luteal cells and macrophage-like cells contained TNFalpha message, while only the latter lineage contained immunoreactive TNFalpha. Hybridization signals and immunoreactivity were more intense in older corpora lutea than in corpora lutea of the present cycle. Northern blot analysis revealed a 2.2-kb TNFalpha mRNA in the ovary that was unchanged relative to 28S rRNA (constitutive RNA) during the cycle. Similarly, TNFalpha hybridization signals and immunoreactivity did not appear to change throughout the cycle. These results indicate that TNFalpha gene transcription in the oocyte coincides with the synthesis of immunoreactive TNFalpha and that these complex biochemical processes occur at distinct steps of follicular development in the mouse. The formation of the second layer of granulosa cells is coupled with the initial phase of TNFalpha gene transcription in the oocyte since TNFalpha MRNA and protein appear at this stage. Our findings also suggest that TNFalpha may be involved in various phases of follicular development, atresia, and luteal function in the mouse.