Interleukin-6 biosynthesis in human preovulatory follicles: some of its potential roles at ovulation

J Clin Endocrinol Metab. 1994 Aug;79(2):633-42. doi: 10.1210/jcem.79.2.7519193.

Abstract

In the present work we explored cellular sites of interleukin-6 (IL-6) biosynthesis in human follicular aspirates from patients undergoing in vitro fertilization therapy and the effects of this cytokine on oocyte fertilization and granulosa cell (GC) steroidogenesis. Biological IL-6 activity from 20-40 IU/mL was present in follicular fluids from 22 patients; it was also detected in 10 of 22 supernatants of cultured oocyte-cumulus complexes and in cumulus cell and GC cultures. Biological IL-6 activity in oocyte-cumulus complex cultures was not related to fertilization rates. Total ribonucleic acid was isolated from follicular aspirates and GC-enriched preparations. After reverse transcriptase and polymerase chain reaction cycles using oligonucleotide primers corresponding to known cDNA sequences for IL-6, a 126-basepair band characterized the amplification product of IL-6 transcripts on gel electrophoresis. To localize IL-6 messenger ribonucleic acid, in situ hybridization analysis was performed using a [35S]IL-6 riboprobe. The distribution of transcripts was more dense (15% vs. 3% stained cells) in GC-enriched preparations, which contained more than 95% GCs, than in original follicular preparations, which contained 20-40% viable GCs; it was not significantly modified by the presence of macrophage contaminants. The expression of IL-6 protein was assessed by positive immunohistological stainings. Biological IL-6 activity was higher, and in situ hybridization signals were more dense and more intense in 24-h GC cultures than in 72-h GC cultures, suggesting that IL-6 biosynthesis was transiently induced. Under experimental conditions of low IL-6 endogenous levels in cultures, adding recombinant human IL-6 from 10-200 IU/mL had no effect on progesterone production or aromatase activity in GC cultures free of macrophages, whereas in GC cultures including macrophage contaminants, stimulatory effects on basal and hCG-stimulated progesterone production and on basal and FSH-stimulated aromatase activities were observed. The present study provides strong support for the view that IL-6 is produced by GCs in the preovulatory follicle at the time of ovulation. In addition, we showed that IL-6 might be an intraovarian regulatory factor concerned with steroidogenesis.

MeSH terms

  • Adult
  • Aromatase / metabolism
  • Base Sequence
  • Cells, Cultured
  • DNA Primers
  • Female
  • Fertilization in Vitro
  • Follicular Fluid / metabolism
  • Granulosa Cells / metabolism
  • Humans
  • In Situ Hybridization
  • Interleukin-6 / biosynthesis*
  • Interleukin-6 / genetics
  • Interleukin-6 / pharmacology
  • Molecular Sequence Data
  • Oocytes / metabolism
  • Ovarian Follicle / metabolism*
  • Ovulation / physiology*
  • Polymerase Chain Reaction
  • Progesterone / biosynthesis
  • RNA-Directed DNA Polymerase
  • Recombinant Proteins / pharmacology

Substances

  • DNA Primers
  • Interleukin-6
  • Recombinant Proteins
  • Progesterone
  • Aromatase
  • RNA-Directed DNA Polymerase