Reply: coasting acts through down regulation of VEGF gene expression and protein secretion
Instituto Valenciano de Infertilidad, C/Santiago de Compostela 88 28035 Madrid and Valencia, Spain
Email: jgvelasco{at}ivi.es
Sir,
We read with interest the letter by Ajonuma et al. and would like to thank them for their interest in our research. However, most of the claims they make are probably based on a misunderstood concept of the coasting procedure. The authors on several occasions claim that coasted patients showed a similar ovarian hyperstimulation syndrome (OHSS) risk to non-coasted patients, and for this reason they consider coasting a useless procedure to minimize the risk of developing the syndrome. We have to bear in mind that patients undergoing coasting are at a very high risk of OHSS: close to 100% would develop OHSS if hCG was administered without any preventive measure and only 
3% do so after coasting. As described by our group and others (Fluker et al., 1999
; Isaza et al., 2002; Ulug et al., 2004), after coasting, a tremendous drop in estradiol levels is observed—as well as in VEGF expression and secretion—reaching figures similar to non-coasted patients, thus bringing to ‘normal’ the risk of OHSS. As stated in the manuscript, coasting does not abolish the risk of OHSS, but it reduces the incidence and severity of the syndrome in patients at a very high risk.
It has been shown in several experimental and clinical settings that estradiol alone is not the causative factor of OHSS. We all see patients in our clinics with high serum E2 levels that do not develop the syndrome while others with not so elevated E2 develop moderate or even severe forms of the syndrome. Even more, patients with extremely high levels of E2 that do not receive hCG do not develop the syndrome. On the other hand, women with very low E2 levels due to an enzymatic defect, i.e. 17,20 desmolase (Pellicer et al., 1991) may show OHSS with ascites; this supports the hypothesis that E2 is not the absolute mediator of capillary permeability. There are several mediators that have been described in the literature, and VEGF is a strong candidate, but obviously it may not be the only one. Our group has shown that the ovary is the main source of VEGF, which acts through VEGR receptor-2 to increase vascular permeability in a rat model, an event that may be blocked by a specific VEGF receptor-2 inhibitor, showing unequivocally that VEGF mediates OHSS (Gómez et al., 2002).
The main strength of our research is based on going further than simply analyzing serum VEGF, evaluating protein secretion in follicular fluids, mRNA expression in granulosa-lutein cells by means of a quantitative analysis (real-time PCR) and cell status by flow cytometry. Ajonuma and coauthors cite several references in the literature regarding the lack of correlation between serum VEGF concentrations and the severity of OHSS, something not surprising as serum VEGF determinations alone are being considered less and less useful. Serum VEGF measurements are influenced by the activation and release of VEGF from cellular components found within blood. Serum concentrations of VEGF can be 8–10-fold higher than plasma levels secondary to the release of VEGF from activated platelets and other cellular components (Verheul et al., 1997), as we discussed in our paper. The use of plasma rather than serum eliminates many of these methodological concerns, thus diminishing the impact of the previous publications based on serum determinations alone. However, since the ovaries are the main source of VEGF production (Gómez et al., 2002), we based our findings not only on peripheral VEGF levels but on VEGF protein secretion in follicular fluids and VEGF gene expression measured in granulosa cells by real-time PCR, a highly specific and accurate quantitative method, confirming that coasting induces a significant decrease in VEGF expression and secretion.
The authors suggest that maybe the apoptotic process could be reversed. As this is a highly speculative hypothesis, there is no proof that after the apoptotic cascade has been initiated by any known or unknown stimulus it could be reversed as suggested (Tilly, 2001).
As shown in Table I (where P on the y-axis refers to ‘pick-up’), estradiol (E2) on the day of hCG was <3000 pg/ml in coasted patients, and did not increase after the day of ovum pick-up. Figure 1 also shows in the dotted line serum E2 levels (z-axis), and there we can observe that E2 is <4000 pg/ml on both days (hCG and P).
Thus, we consider—as do Ajonuma et al.—that serum estradiol levels are an excellent clinical predictor of the risk of suffering OHSS in a specific patient. In fact, it is the parameter being used to decide whether or not a patient should be coasted. Understanding the empiric mechanisms of many clinical attitudes will not only benefit our patients but also improve our logical reasoning. We have shown that VEGF plays a pivotal role in justifying the benefits of coasting, and confirmed that this preventive manoeuvre is an excellent alternative to cycle cancellation in patients at a very high risk of developing OHSS.
References
Fluker MR, Hooper WM and Yuzpe AA (1999) Withholding gonadotropins (‘coasting’) to minimize the risk of ovarian hyperstimulation during superovulation and in vitro fertilization-embryo transfer cycles. Fertil Steril 71, 294–301.[CrossRef][Web of Science][Medline]
Gómez R, Simón C, Remohí J and Pellicer A (2002) Vascular endothelial growth factor receptor-2 activation induces vascular permeability in hyperstimulated rats, and its effect is prevented by receptor blockade. Endocrinol 143, 4339–4348.
Isaza V, García-Velasco JA, Aragones M, Remohi J, Simón C and Pellicer A (2002) Oocyte and embryo quality after coasting: the experience from oocyte donation. Hum Reprod 17, 1777–1782.
Pellicer A, Miró F, Sampaio M, Gómez E and Bonilla-Musoles F (1991) In vitro fertilization as diagnostic and therapeutic tool in a patient with partial 17,20 desmolase deficiency. Fertil Steril 50, 970–975.
Tilly JL (2001) Commuting the death sentence: how oocytes strive to survive. Nat Rev Mol Cell Biol 2, 838–848.[CrossRef][Web of Science][Medline]
Ulug U, Ben-Shlomo I and Bahceci M (2004) Predictors of success during the coasting period in high-responder patients undergoing controlled ovarian stimulation for assisted reproduction. Fertil Steril 82, 338–342.[CrossRef][Web of Science][Medline]
Verheul HM, Hoekman K, Luykx-de-Bakker S, Eekman CA, Folman CC, Broxterman HJ and Pinedo HM (1997) Platelet: transporter of vascular endothelial growth factor. Clin Cancer Res 3, 2187–2190.
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