Cumulus cell gene expression in luteal-phase-derived oocytes after double stimulation in one menstrual cycle

Abstract

Research question

Does double stimulation (DuoStim) affect cumulus cell gene expression in luteal-phase-derived oocytes?

Design

This prospective observational study included 39 patients with reduced ovarian reserve. Fifteen patients (group 1) underwent IVF with a gonadotrophin-releasing hormone antagonist in the follicular phase and 24 patients (group 2) underwent DuoStim. A total of 149 cumulus cell samples were divided into two groups according to the phase of the cycle: group 1 included 55 follicular-phase-derived oocytes and group 2 included 94 luteal-phase-derived oocytes. The expression levels of the following genes were assessed using quantitative polymerase chain reaction: HAS2, VCAN, ALCAM, PTGS2, GREM1, ITPKA, TRPM7, SDC4, CALM2, SPSB2, TP53I3, PGR and PFKP.

Results

The expression of 10 out of 13 genes in cumulus cells was similar between DuoStim luteal-phase-derived oocytes and follicular-phase-derived oocytes. A significant increase in the mRNA levels of VCAN (15.542 ± 6.8 versus 20.353 ± 10.58; P = 0.001), SDC4 (1.016 ± 0.65 versus 1.318 ± 0.97; P = 0.013), and TP53I3 (0.185 ± 0.09 versus 0.270 ± 0.11; P = 1.19E-05) was observed in group 2. The number of oocytes collected (5.57 ± 2.3 versus 5.7 ± 2.7; P > 0.05) and the number of blastocysts were comparable between the groups (2.1 ± 2.1 versus 2.7 ± 2.2; P > 0.05).

Conclusions

The DuoStim approach leads to changes in the follicular environment. It affects the expression levels of VCAN, SDC4, and TP53I3 in the cumulus cells of luteal-phase-derived oocytes. These results, however, did not correlate with oocyte maturation, embryo quality and pregnancy rate.

Introduction

Many strategies have been proposed for the management of patients with impaired ovarian response; however, the consensus on the most beneficial approach has not yet been reached (Vaiarelli et al., 2018). To optimize and personalize the management of poor responders, a low prognosis concept was introduced by the Patient-Oriented Strategies Encompassing Individualized Oocyte Number group in 2016 (Alviggi et al., 2016). In addition, a new measure was introduced for successful treatment: the ability to retrieve the number of oocytes necessary to obtain at least one euploid embryo for transfer in each patient (Alviggi et al., 2016). In this context, one of the most promising approaches is double stimulation (DuoStim), which results in a larger yield of retrieved oocytes in a single ovarian cycle compared with the traditional stimulation in the follicular phase only. Using the random-start protocol, it has been demonstrated that oocytes can be obtained regardless of the phase of the menstrual cycle. Hence, use of the random-start protocol has been suggested for fertility preservation in patients with cancer (von Wolff et al., 2009; Bedoschi et al., 2010; Sönmezer et al., 2011). This agrees with the multiple follicular wave theory, which suggests that two or three groups of antral follicles are recruited and undergo synchronous growth at regular intervals during each menstrual cycle (Baerwald et al., 2012). The concept of stimulation in the follicular and luteal phases of the menstrual cycle, introduced by Kuang et al. (2014) (Shanghai protocol) and Ubaldi et al. (2016) (DuoStim), is a novel approach in the management of poor-responder patients. Previous studies have demonstrated a higher retrieval rate of good-quality oocytes and embryos during a single menstrual cycle using the DuoStim approach, which led to higher pregnancy rates (Kuang et al., 2014; Ubaldi et al., 2016; Vaiarelli et al., 2017; Cimadomo et al., 2018).

Furthermore, recent studies have reported no difference in gestational age, birth weight, length and congenital birth defects between the live births resulting from luteal phase stimulation (LPS) compared with those resulting from conventional stimulation protocols (Chen et al., 2015; Cimadomo et al., 2018). The quality of LPS-derived oocytes requires further investigation. The morphological appearance of the oocyte does not accurately predict oocyte competence. One of the methods to determine oocyte quality is the analysis of cumulus cells (Fragouli et al., 2012). Cumulus cells surround the oocyte and are pivotal in determining oocyte developmental competence. Several studies have revealed certain cumulus cell genes that are correlated with oocyte competence, embryo development and pregnancy rates (Adriaenssens et al., 2010). These genes have a critical role in folliculogenesis and oocyte development (Table 1). Gene expression in the cumulus cells of LPS-derived oocytes after DuoStim, however, has still not been investigated. Therefore, this study aimed to investigate whether DuoStim affects gene expression in the cumulus cells obtained from the luteal-phase-derived oocyte–cumulus complex.