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Detailed analysis of cytoplasmic strings in human blastocysts: new insights
Jessica Eastick1,2, Christos Venetis1,2, Simon Cooke1,2
1IVFAustralia, New South Wales, Australia.
Insights
Cytoplasmic strings (CS) in human blastocysts are linked to higher embryo quality and improved live birth rates in fertility treatments. Their presence indicates better development and is not a negative predictor.
Area of Science:
- Reproductive Biology
- Embryology
- In Vitro Fertilization
Background:
- Cytoplasmic strings (CS) are observed in human embryos during in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).
- The clinical significance and association of CS with human blastocyst development and outcomes remain areas for further investigation.
Purpose of the Study:
- To investigate the association between the presence and characteristics of cytoplasmic strings (CS) and human blastocyst quality.
- To evaluate the relationship between CS and embryo development and clinical outcomes, specifically live birth rate.
Main Methods:
- A two-centre cohort study involving 1152 blastocysts from 225 patients undergoing IVF/ICSI.
- Embryos were cultured in Embryoscope+; CS presence, number, location, and duration were assessed using time-lapse imaging and specialized software.
- Blastocyst quality and developmental stage were evaluated on day 5, with CS characteristics recorded on days 5/6.
Main Results:
- A positive association was found between the presence of CS and higher blastocyst quality and advanced developmental stages.
- Blastocysts with more CS and vesicles traveling along them were of higher quality and showed longer CS activity duration.
- Blastocysts exhibiting CS demonstrated a significantly higher live birth rate compared to those without.
Conclusions:
- The presence of a higher number of CS and vesicles in human blastocysts is associated with top-quality embryos and is not a negative predictor of development.
- CS presence is linked to improved blastocyst quality, advanced development, and a significant increase in live birth rates.
- This study confirms CS as a potentially positive indicator in human blastocyst development and clinical success in assisted reproductive technologies.
Abstract:
The aim of this study was to determine if there was an association between the presence of cytoplasmic strings (CS) and their characteristics, with blastocyst quality, development and clinical outcome in human blastocysts. This two-centre cohort study was performed between July 2017 and September 2018 and involved a total of 1152 blastocysts from 225 patients undergoing in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). All embryos were cultured in Embryoscope+ and were assessed for CS using time-lapse images. A single assessor examined all blastocysts and reviewed videos using the EmbyroViewer® Software. Blastocyst quality was assessed on day 5 of embryo development. The number of CS, location and duration of their activity was recorded on days 5/6. A positive association between the presence of CS in human blastocysts with blastocyst quality was identified. Blastocysts with a higher number of CS present, were of higher quality and were in the more advanced stages of development. Top quality blastocysts had CS activity present for longer, as well as having a higher number of vesicles present travelling along the CS. Blastocysts that had CS present, had a significantly higher live birth rate. This study has confirmed that a higher number of CS and vesicles in human blastocysts is associated with top quality blastocysts and is not a negative predictor of development. They had a higher number of CS present that appeared earlier in development and, although ceased activity sooner, had a longer duration of activity. Blastocysts with CS had a significant increase in live birth rate.
