Somatic cell nuclear transfer (SCNT) is a powerful technique, but still very inefficient despite 20 years passed by since the cloned mammal was born. We have recently shown that the major cause of abnormalities observed in cloned fetuses are mitochondrial dysfunctions in placenta collected from cloned sheep. Investigations on mitochondria in SCNT are limited to the mtDNA hetero/homoplasmy in cloned offspring, whereas no data is available for an eventual role of mitochondria dysfunction on the developmental failure of cloned animals. Here we wanted to know whether mitochondrial abnormalities are observed already in cloned blastocysts since mitochondrial replication does not occur after the hatched blastocysts stage. SCNT and in vitro processed (IVP) blastocysts were produced and analysed for mitochondrial structure and functionality. First, embryos were analysed using transmission electron microscope (TEM). Drastic differences in mitochondrial structure between SCNT and IVP blastocysts were observed. Decrease density of mature mitochondria, very high degree of cytoplasmic vacuolisation, numerous cytoplasmic vesicle and autophagosomes were observed in SCNT blastocysts. Moreover, statistically lower expression of major mitochondrial, autophagic and apoptotic proteins were observed in SCNT embryos. Obtained results clearly shown that mitochondrial abnormalities are already observed in blastocysts stage embryos. It is important to point out that activity of mitochondria are strictly control by nuclear signals, thus, obtained results may suggest that incomplete nuclear reprogramming in cloned nucleus might be responsible also for the impaired mitochondrial function in cloned embryos/fetuses
