RESUMO
Introduction: The aim of this investigation was to study the developmental potential of human fragmented embryos to blastocyst stage and to evaluate the developed 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 were obtained from the embryology lab of Royan Institute. Embryos were scored according to the degree of fragmentation, using invert microscope, into four groups [group I: embryos with least fragmentation, group II: embryos with small fragment among blastomers, group III: embryos with large fragment approximately in the size of blastomers and group IV: embryos with necrotic fragments]. Each group was cultured in rS2 medium and their development was recorded to the day six [embryos were cultured in rS1 for first 3 days].In this study the size and the quality of developed blastocyst and number of blastomer in the ICM and TE were evaluated. The number of dead cells in each blastocyst [apoptotic or necrotic] were counted using TUNEL staining and the results were analyzed statistically by chi2 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 stopped their development at 8-cell to morolla stage. The rate of blastocyst formation of embryos from group I and II was higher than group III and IV. The results showed that 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 ratio of ICM to TE in embryos from each group is not statistically different compared to other groups. But the mean total number of blastomer and the mean number of ICM and 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 of fragmentation 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 low number of total cell number. In addition the number of dead cell was higher