Cumulus Cells

Cumulus cells (CCs) originating from undifferentiated granulosa cells (GCs) differentiate in mural granulosa cells (MGCs) and CCs during antrum formation in the follicle by the distribution of location. CCs are supporting cells of the oocyte that protect the oocyte from the microenvironment, which helps oocyte growth and maturation in the follicles. Bi-directional communications between an oocyte and CCs are necessary for the oocyte for the acquisition of maturation and early embryonic developmental competence following fertilization. Follicle-stimulation hormone (FSH) and luteinizing hormone (LH) surges lead to the synthesis of an extracellular matrix in CCs, and CCs undergo expansion to assist meiotic resumption of the oocyte. The function of CCs is involved in the completion of oocyte meiotic maturation and ovulation, fertilization, and subsequent early embryo development. Therefore, understanding the function of CCs during follicular development may be helpful for predicting oocyte quality and subsequent embryonic development competence, as well as pregnancy outcomes in the field of reproductive medicine and assisted reproductive technology (ART) for infertility treatment.

Impaired oocyte quality has been demonstrated in diabetic mice; however, the potential pathways by which maternal diabetes exerts its effects on the oocyte are poorly understood. Cumulus cells are in direct contact with the oocyte via gap junctions and provide essential nutrients to support oocyte development. In this study, we investigated the effects of maternal diabetes on the mitochondrial status in cumulus cells. We found an increased frequency of fragmented mitochondria, a decreased transmembrane potential and an aggregated distribution of mitochondria in cumulus cells from diabetic mice. Furthermore, while mitochondrial biogenesis in cumulus cells was induced by maternal diabetes, their metabolic function was disrupted as evidenced by lower ATP and citrate levels. Moreover, we present evidence suggesting that the mitochondrial impairments induced by maternal diabetes, at least in part, lead to cumulus cell apoptosis through the release of cytochrome c. Together the deleterious effects on cumulus cells may disrupt trophic and signaling interactions with the oocyte, contributing to oocyte incompetence and thus poor pregnancy outcomes in diabetic females.

The ovarian follicle is the basic functional unit of the ovary, comprising theca cells and granulosa cells (GCs). Two different types of GCs, mural GCs and cumulus cells (CCs), serve different functions during folliculogenesis. Mural GCs produce oestrogen during the follicular phase and progesterone after ovulation, while CCs surround the oocyte tightly and form the cumulus oophurus and corona radiata inner cell layer. CCs are also engaged in bi-directional metabolite exchange with the oocyte, as they form gap-junctions, which are crucial for both the oocyte's proper maturation and GC proliferation. However, the function of both GCs and CCs is dependent on proper follicular angiogenesis. Aside from participating in complex molecular interplay with the oocyte, the ovarian follicular cells exhibit stem-like properties, characteristic of mesenchymal stem cells (MSCs). Both GCs and CCs remain under the influence of various miRNAs, and some of them may contribute to polycystic ovary syndrome (PCOS) or premature ovarian insufficiency (POI) occurrence. Considering increasing female fertility problems worldwide, it is of interest to develop new strategies enhancing assisted reproductive techniques. Therefore, it is important to carefully consider GCs as ovarian stem cells in terms of the cellular features and molecular pathways involved in their development and interactions as well as outline their possible application in translational medicine.

PurposeCan sperm selection through cumulus cells improve embryo quality compared to conventional methods, and is its effectiveness influenced by parental age?MethodsThis prospective clinical trial included 99 ICSI cycles from 95 couples. Sibling oocytes were randomly allocated at the oocyte level to either the study group (cumulus cell-mediated sperm selection after conventional density gradients centrifugation (DGC), 554 oocytes) or the control group (only sperm selection by DGC, 543 oocytes), using a dish designed to facilitate sperm interaction with cumulus cells. The inclusion criteria for this study were patients using their own oocytes, with a medical indication for ICSI, who had at least 6 mature oocytes (MII) in that cycle. For semen samples, inclusion required the ability to adjust the concentration to 10 million/mL. Exclusion criteria included the use of vitrified oocytes, donated oocytes, and semen samples obtained by testicular biopsy or aspiration. Embryo quality was assessed at the blastocyst stage on day 5 according to ASEBIR. A subanalysis evaluated the influence of parental age on outcomes.ResultsThe study group showed a significantly higher proportion of good-quality day-5 blastocysts compared to controls (55.2% vs. 45.3%, p = 0.028). No statistically significant differences were observed in overall blastocyst formation or pregnancy rates, although favourable trends were noted. In an age-stratified analysis, a significant improvement in day-5 blastocyst quality among evaluable blastocysts was observed in women aged 40-45 (51.4% vs. 30.4%, p = 0.017), with a non-significant trend toward improved outcomes in men aged 40-53 (44.7% vs. 32.6%, p = 0.083). No differences were seen in younger age groups.ConclusionCumulus cell-mediated sperm selection after DGC using a specialized Oosafe® ICSI Dish with Sperm Selection Channels was associated with an increased proportion of good-quality day 5 blastocysts compared with conventional sperm preparation. While clinical outcomes did not differ significantly, these findings suggest a potential benefit in specific ART subpopulations, particularly those of advanced maternal age. Further adequately powered studies are required to confirm these observations and to determine their impact on clinical outcomes.