Heteroparental blastocyst production from microsurgically corrected tripronucleated human embryos.
OBJECTIVE: To prove the efficiency of identification and removal of one of the surplus paternal pronuclei in dispermic IVF zygotes to obtain heteroparental blastocysts. DESIGN: Experimental. SETTING: One hundred fourteen tripronucleated (3PN) embryos from conventional IVF. PATIENT(S): After informed and signed consent, the patients from Instituto Valenciano Infertilidad (IVI), Valencia, donated their abnormally fertilized embryos. INTERVENTION(S): Seventy-two embryos were diploidized by microsurgical removal of the pronucleus located at the farthest position to the second polar body. Forty-two 3PN embryos served as controls. MAIN OUTCOME MEASURE(S): Survival and correction rate; in vitro development up to the blastocyst stage; X, Y, and 18 chromosome determination by triple fluorescent in situ hybridization and, inheritance analysis for 10 polymorphic repeat regions using polymerase chain reaction (PCR) amplification and sequencing. RESULT(S): Seventy-eight percent of 3PN zygotes (56/72) survived manipulation and eventually 51 zygotes had two pronuclei (71%). Forty-one percent of manipulated embryos progressed in vitro to the blastocyst stage (21/51). Fluorescent in situ hybridization analysis performed on eight manipulated embryos confirmed their diploid state; all four controls were triploid. Heteroparental inheritances were also confirmed in four of six manipulated embryos. CONCLUSION(S): Heteroparental blastocysts can be derived from corrected dispermic zygotes.