The importance of cytoplasmic strings during early human embryonic development

Area of Science:

• Reproductive Medicine
• Embryology
• Assisted Reproductive Technology

Background:

• Embryo selection in in vitro fertilisation (IVF) traditionally relied on morphological assessment.
• Current IVF practices utilize time-lapse imaging for morphokinetic analysis.
• Cytoplasmic strings (CS) at the blastocyst stage are a newly observable feature.

Purpose of the Study:

• To investigate the relationship between the presence of cytoplasmic strings (CS) and embryo viability in human IVF.
• To compare morphokinetic parameters and developmental dynamics of embryos with and without CS.

Main Methods:

• Evaluation of morphokinetic data from 208 human embryos across 78 IVF patients.
• Comparison of embryo development, morphology, and time-lapse derived scores (KIDScore, iDAScore) between CS+ and CS- groups.
• Analysis of blastocyst development rates and time to reach blastocyst stage.

Main Results:

• 81.2% of blastocysts exhibited cytoplasmic strings (CS+).
• CS+ embryos showed significantly higher rates of developing into high-quality blastocysts (52.1% vs. 20.5%, p=0.02).
• CS+ embryos achieved better morphokinetic scores (KIDScore, iDAScore) and reached the blastocyst stage earlier (103.9h vs. 107.6h, p=0.001).

Conclusions:

• The presence of cytoplasmic strings (CS) is common in human blastocysts and not linked to the fertilization method (IVF vs. ICSI).
• CS+ embryos demonstrate enhanced developmental potential, indicated by superior morphokinetic parameters and earlier blastocyst formation.
• Cytoplasmic strings are a promising indicator of increased embryo viability and implantation potential in IVF treatments.