Leukaemia inhibitory factor expression in human follicular fluid and ovarian cells

Abstract

Leukaemia inhibitory factor (LIF) is a 43 kDa glycoprotein with a remarkable range of biological actions in different tissue systems. LIF improves the rate of fertilization of mouse oocytes in vitro and up-regulates aromatase enzyme. We postulated that LIF may be an important modulator of ovarian function and may also improve embryo quality in humans. Follicular fluid samples from patients undergoing in-vitro fertilization (IVF) and embryo transfer (n = 123), from women undergoing ovarian stimulation (n = 4) and from women undergoing laparoscopy for tubal ligation during their follicular phase (n = 3) were used. Follicular fluid LIF, oestradiol, and progesterone were measured and embryo quality was assessed. Granulosa-lutein cells were cultured for 3 days in Ham's F-12:Dulbecco's modified Eagle's medium (DMEM). Ovarian stromal cells, isolated by enzymatic dispersion of ovarian tissue, were also cultured in the same medium. Following experimental treatments, LIF mRNA and protein concentrations were quantified. The concentration of LIF was 0.8 +/- 0.3 (mean +/- SEM) pg/ml in pre-human chorionic gonadotrophin (HCG) follicular fluid samples and 13.0 +/- 1.1 pg/ml in post-HCG follicular fluid samples (P < 0.05). LIF levels were undetectable in three follicular fluid samples obtained during unstimulated follicular phase. There was a correlation between follicular fluid LIF and follicular fluid oestradiol concentrations (r = 0.36; P = 0.0001) and the number of grade I embryos (r = 0.62; P = 0.01). LIF mRNA and the protein were expressed constitutively but in low amounts in the ovarian stromal cell cultures. The concentrations of LIF mRNA as well as protein were increased by interleukin (IL)-1alpha and tumour necrosis factor alpha (TNF alpha) in a time- and concentration-dependent manner. Purified granulosa-lutein cells expressed low amounts of LIF mRNA and protein which were not significantly increased by IL-1alpha or TNF alpha. Our findings suggest that HCG stimulates the expression of LIF in follicular fluid. Both granulosa-lutein and ovarian stromal cells express the LIF mRNA and produce the protein. Modulation of LIF in these cells may play an important role in the physiology of ovulation and early embryo development.