Laboratoire de Biologie de la Reproduction, CHU-HME, 7 quai Moncousu, 44093 Nantes cedex 01, France
INSERM U 463, Institut de Biologie, 9 quai Moncousu, 44093 Nantes cedex 01, France
Service de Gynecologie, CHU-HME, 7 quai Moncousu, 44093 Nantes cedex 01, France
Dear Sir,
We were interested to read the paper by Arici et al. (1997) who found leukaemia inhibitory factor (LIF) expression in human follicular fluid (hFF). We would like to confirm this fact and make some short comments.
Since we have postulated that LIF could play a role in the inflammatory-like processes involved in the periovulatory events, we have performed a study to assess its presence in hFF and evaluate this cytokine as a marker of oocyte quality. The preliminary results of this study were presented at the 13th Annual Meeting of the European Society for Human Reproduction and Embryology (ESHRE) (Jean et al., 1997).
Briefly, the hFF samples evaluated in our study (n = 96) were obtained from individual follicles at the time of oocyte retrieval for patients undergoing in-vitro fertilization (IVF). The aspirated follicles were immediately examined for the presence of oocytes and hFF were then classified into two groups based on the morphology of the oocyte. Group 1 (n = 70) included hFF corresponding to oocytes that could be inseminated, while group 2 (n = 26) was composed of hFF containing atretic oocytes. The LIF concentration of each hFF sample was determined in both groups by an enzyme-linked immunosorbent assay (ELISA) method (kit Medgenix, Fleurus, Belgium) while the patient serum served as a negative control for LIF detection. The sensitivity (20 pg/ml), the precision (intra-assay variation <5%), and the reproducibility (inter-assay variation <10%) of this ELISA have been reported previously (De Groote et al., 1994) while a good correlation (r = 0.96; P <0.0001) between LIF measurements in several biological fluids using this ELISA and the corresponding DA-1a bioassay has been demonstrated previously (Godard et al., 1993
; De Groote et al., 1994
).
As reported by Arici et al., we confirm that LIF was expressed in hFF samples 35 h after administration of human chorionic gonadotrophin (HCG). However, despite the lack of available data in the literature, we were astonished by the very low mean concentration of LIF measured by these authors (13.0 ± 1.1 pg/ml) in comparison with the LIF concentrations reported in our study (group 1: 2833.37 ± 1270.08 pg/ml and group 2: 1602.33 ± 1159.01 pg/ml). In addition, the mean concentration of LIF in the pre-HCG hFF samples (0.8 ± 0.3 pg/ml) appears to be very low, especially with respect to the sensitivity for LIF (2 pg/ml) of the ELISA used by Arici et al. This level of LIF seems to us to be too low to be considered as a significant expression of LIF in hFF samples obtained from patients prior to the administration of HCG.
Nevertheless, we fully agree with these authors that LIF is probably one of the factors in hFF involved in the ovulatory process and embryo development. As they reported a significant correlation between embryo quality and corresponding hFF LIF concentrations, we have demonstrated that the LIF level in hFF could be related to the oocyte quality. Thus, both the findings by Arici et al. and ourselves support the hypothesis that LIF expression in hFF is required in the early reproductive events.
Finally, although further studies have to be conducted to assess accurately the level of LIF in hFF, this cytokine appears to have a promising role in extending our knowledge of the processes leading to fertilization and embryo development.
References
Arici, A., Oral, E., Bahtiyar, O. et al. (1997) Leukaemia inhibitory factor expression in human folicular fluid and ovarian cells. Hum. Reprod., 12, 12231239.
De Groote, D., Fauchet, F., Jadoul, M. et al. (1994) An ELISA for the measurement of human leukemia inhibitory factor in biological fluids and culture supernatants. J. Immunol. Meth., 167, 253261.[ISI][Medline]
Godard, A., Fauchet, F., Raher, S. et al. (1993) Obtention of monoclonal antibodies against LIF/HILDA and their use in the quantitative assay of the cytokine. Cytokine, 5, 1623.[ISI][Medline]
Jean, M., Mensier, A., Godard, A. et al. (1997) Leukaemia inhibitory factor concentration in follicular fluid: a marker of oocyte quality? [Abstr. no. P-054] Hum. Reprod., 12 (Abstr. Book 1), 145.
Yale University School of Medicine, Department of Obstetrics and Gynecology 333 Cedar Street, PO Box 208063, New Haven, CT 06520-8063, USA
Dear Sir,
We read with interest the letter by Jean et al., and we appreciate their comments. We were pleased to see that their results confirm ours. However, we were surprised by the relatively high concentrations of leukaemia inhibitory factor (LIF) measured by these authors; their values are >200-fold higher than the ones we observed. The most likely possibility is the use of different enzyme-linked immunosorbent assay (ELISA) kits. Our kit came from R&D Systems, Rochester, MI, USA, while their ELISA was from Medgenix, Fleurus, Belgium. We are planning to purchase an ELISA from Medgenix, so that we can compare the two kits.
We thank Jean et al. for their interest.