Document Type : Original Article
FRAGMENTATION, HUMAN EMBRYO, BLASTOCYST, TUNEL
Introduction: The aim of this investigation was to study the developmental potential of human fragmented embryos to blastocyst stage and to evaluate thedeveloped blastocysts in the term of size, cellularity, the type of inner cell mass(ICM), trophoetoderm (TE) and the number of dead cells.
Material and Methods: Four to eight cell fragmented human embryos wereobtained from the embryology lab of Royan Institute. Embryos were scoredaccording to the degree of fragmentation, using invert microscope, into four groups(group I: embryos with least fragmentation, group II: embryos with small fragmentamong blastomers, group Ill: embryos with large fragment approximately in the sizeof blastomers and group IV: embryos with necrotic fragments). Each group wascultured in rS2 medium and their development was recorded to the day six (embryoswere cultured in rS1 for first 3 days).In this study the size and the quality of developed blastocyst and number ofblastomer in the ICM and TE were evaluated .The number of dead cells in eachblastocyst (apoptotic or necrotic) were counted using TUNEL staining and theresults were analyzed statistically by X2 and ANOVA.
Results: High percentage of embryos from group IV had developmental block at 2- 4 cell stage. In addition, a high percentage of embryos from all groups stoppedtheir development at 8-cell to morolla stage. The rate of blastocyst formation ofembryos from group I and II was higher than group III and IV. The results showedthat size of embryos from group IV was statistically lower than groups I and II.Blastocyst quality (the number of blastomers in ICM) of embryos from group I and II was better than group III and IV. Differential staining results suggested that the ratioof ICM to TE in embryos from each group is not statistically different compared toother groups. But the mean total number of blastomer and the mean number of ICMand TE of embryos from groups I and II was higher than the other two groups. The results of TUNEL staining showed that embryos with high number and size offragmentation at 4-cell stage had a high number of apoptotic and necrotic cell.
Conclusion: Embryos with high fragmentation have reduced developmental potential, blastocyst size, low quality blastocyst, low quality ICM and TE, and lownumber of total cell number. In addition the number of dead cell was higher.