INCREASED CELL-DEATH IN RAT BLASTOCYSTS EXPOSED TO MATERNAL DIABETES IN-UTERO AND TO HIGH GLUCOSE OR TUMOR-NECROSIS-FACTOR-ALPHA IN-VITRO

The morphogenetic function of the transient phase of cell death that o ccurs during blastocyst maturation is not known but it is thought that its regulation results from a delicate balance between survival and l ethal signals in the uterine milieu, In this paper, we show that blast ocysts from diabetic rats have a higher incidence of dead cells than c ontrol embryos, Differential lineage staining indicated that increased nuclear fragmentation occurred mainly in the inner cell mass, In addi tion, terminal transferase-mediated dUTP nick end labeling (TUNEL) dem onstrated an increase in the incidence of non-fragmented DNA-damaged n uclei in these blastocysts. Analysis of the expression of clusterin, a gene associated with apoptosis, by quantitative reverse transcription -polymerase chain reaction detected an increase in the steady-state le vel of its transcripts in blastocysts from diabetic rats, In situ hybr idization revealed that about half the cells identified as expressing clusterin mRNA exhibited signs of nuclear fragmentation, In vitro expe riments demonstrated that high D-glucose increased nuclear fragmentati on, TUNEL labeling and clusterin transcription, Tumor necrosis factor- alpha (TNF-alpha), a cytokine whose synthesis is up-regulated in the d iabetic uterus, did not induce nuclear fragmentation nor clusterin exp ression but increased the incidence of TUNEL-positive nuclei, The data suggest that excessive cell death in the blastocyst, most probably re sulting from the overstimulation of a basal suicidal program by such i nducers as glucose and TNF-alpha, may be a contributing factor of the early embryopathy associated with maternal diabetes.