O-099 The use of cumulus cells (CCs) to select spermatozoa for intracytoplasmic sperm injection improves blastocyst development and quality
Authors: Marti L , Ten J , Herreros M , Diaz N , Rodriguez-Arnedo A , Guerrero J , Ortiz J.A , Bernabeu A , Bernabeu R 
Published: June 2022

Study question

Is there a role for sperm selection based on the capacity to pass through cumulus oophorous column in improving the laboratory outcomes in ICSI cycles?

Summary answer

A higher rate of blastocyst formation and quality are obtained with the use of CCs to select spermatozoa for ICSI compared to conventional density gradients.

What is known already

The sperm selection for ICSI is an operator-dependent procedure based on sperm morphology and motility. ICSI bypasses all natural barriers of sperm selection, which may impact embryo development.

During natural fertilization, only the spermatozoa that pass-through cumulus cells will have the chance to fertilize the egg. Spermatozoa capable of traverse COCs have better morphology, higher chromatin integrity and greater acrosomal reaction. Hyaluronic acid is an important component of these cells and plays a key role in the selection of spermatozoa with intact DNA. However, there is scarce data regarding this selection method for ICSI on the development of the embryo.

Study design, size, duration

This is a prospective randomized sibling oocyte pilot study (February-December 2021). A total of 996 metaphase II (MII) oocytes were randomized into two groups. In the control group (Group 0, n = 489 MII), ICSI was performed with sperm selected by conventional density gradients. In the study group (Group 1, n = 507 MII) the oocytes were microinjected with sperm selected through CCs. The main outcome was blastocyst formation rate and quality. Reproductive results were analyzed as secondary outcomes.

Participants/materials, setting, methods

Ninety-eight couples undergoing ICSI (private center) with ≥6 fresh own MII obtained after ovarian stimulation, embryo culture until blastocyst stage and ejaculated sperm samples were included in the study.

All seminal samples were processed using density gradients and those in the study group were additionally passed through CCs (the patient's own CCs were used in all cases).

Fertilization and day 5 blastocyst formation rates were assessed. Embryo quality was scored according to Gardner's criteria.

Main results and the role of chance

Data was similar with regards to cause of infertility, maternal age (36.47 vs 36.63 y.o.), sperm count (60.53 vs 58.25 mill/ml) and progressive motility (57.45 vs 57.50%) between group 0 vs 1, respectively.

Fertilization rate was similar between groups (74.0% vs 78.7%; p = 0.419. Group 0 vs 1, respectively). However, the blastocyst formation rate was significantly higher in the study group compared to control (70.9% vs 60.1%; p = 0.002). In addition, high-quality blastocyst rate was significantly higher in the CCs compared to the control group (49.6% vs 38.5%; p = 0.003). After the analysis of 145 treatments (131 frozen vs 14 fresh transfers) the cumulative clinical pregnancy rate in the study group was 47.2%, higher than in the control group (32.1%), but without reaching statistical difference (p = 0.07).

Limitations, reasons for caution

This is an exploratory study, aimed to evaluate the effectiveness of CCs as a more “physiologic” selection of spermatozoa for ICSI treatments in terms of laboratory outcomes (blastocyst formation rate and quality). Albeit not reaching statistical significance, the higher cumulative pregnancy rate in the study group seems clinically relevant.

Wider implications of the findings

Our results suggest that CCs can select more competent sperm for ICSI. This “physiologic-resembling”, operator-independent selection method has the potential of increasing pregnancy outcomes in ICSI cycles, pending of confirmation in larger studies including cumulative embryo-transfer cycles.

Trial registration number

NA