P-142 Alterations in mitochondrial DNA levels in luteal granulosa cells may affect the morphology of mature oocytes and subsequently their fertilization potential: a retrospective multicenter study
Authors: Raad G , Tanios J , Yarkiner Z , Bazzi M , Mourad Y , Azoury J , Fakih F , Fakih C 
Published: June 2023

Abstract

Study question
Do alterations in mitochondrial DNA levels in luteal granulosa cells (LGCs) affect the quality of mature oocytes in infertile women?

Summary answer
Alterations in the mitochondrial DNA levels in LGCs may modify the characteristics of the first polar body in oocytes and subsequently decrease their fertilization potential.

What is known already
Assisted reproductive treatment outcomes are closely linked to the oocyte quality as shown in several systematic reviews and meta-analyses. Particularly, the oocyte quality is highly affected by the surrounding luteal granulosa cells (LGCs). This is mainly due to the crucial role of the mitochondria in the LGCs in fueling the metabolic processes required for oocyte maturation. Therefore, modifications in the quality of LGCs may have direct effects on the developmental competence of oocytes. However, the exact mechanisms by which this could happen are not fully understood.

Study design, size, duration
A retrospective multicenter study was conducted on 303 mature oocytes retrieved from 51 women undergoing intracytoplasmic sperm injection (ICSI). It was conducted in Lebanon at Al Hadi IVF center and Azoury IVF clinic, between January 2019 and January 2020. G-Power 3.1 was used to determine the sample size for Generalized Linear Mixed Models through a one-sample t-test power analysis with alpha 0.05, power 0.8, medium effect size (f2 = 0.15), and 5 predictors. Resulting sample size: 43.

Participants/materials, setting, methods
This study excluded cases of premature ovarian failure, severe oligozoospermia (&lt;2 x 102/ml), or cases using frozen gametes. Mature oocytes, from young women (&lt; 36 years old), were injected and cultured in the Embryoscope where morphometric measurements were performed. LGCs vitality and mitochondrial DNA (mtDNA) levels were analyzed using trypan blue exclusion dye and next-generation sequencing, respectively. Possible associations between these independent variables and the size and integrity of the first polar body were evaluated.

Main results and the role of chance
The included women presented with primary infertility. Their mean age was 29.98 ± 5.5 years old and their mean body mass index was 23.33 ± 3.32 Kg/m2. 10% of the included women had polycystic ovary syndrome, and 48% were smokers. Regarding the LGCs parameters, a statistically significant negative correlation was found between the mtDNA levels in LGCs and their vitality percentage (r = −0.313, p = 0.029). Interestingly, the average size of the first polar body (PBI) was 346.67 µm. Here we found that the PBI size decreased by 15.05 units when the mtDNA level in LGCs increased by one unit above its average. In parallel, the median percentage of oocytes having a fragmented PBI was 33.33 (0-100). This percentage increased by 4.26% for every one unit increase in the mtDNA level in LGCs (p &lt; 0.0001). In contrast, this percentage decreased by 0.86% for every unit increase in the percentage of LGCs vitality (p &lt; 0.0001). Moreover, the mean percentage of fertilization rate was found to be 70.19 ± 26.7. A higher percentage of fragmented PBI (38.3%) was found among oocytes that did not fertilize compared to those that did successfully fertilize (24%) (p = 0.019).

Limitations, reasons for caution
This study only analyzed the effects of alterations in mtDNA levels in LGCs on oocytes. It would be worthwhile to also analyze the effects on foetal development and offspring health. Furthermore, it would be interesting to study the relationship between alterations in LGCs and oocyte quality within individual follicles.

Wider implications of the findings
Several studies have suggested that abnormal size and fragmentation of the PBI may impair embryo development. Therefore, treating factors that affect LGCs, such as obesity and polycystic ovary syndrome, may benefit infertile women. This highlights the need for new clinical trials in this context.

Trial registration number
Not applicable