The group of scientists working with mouse cloning has reported that cloned mice in comparison with normal are sensitive to aging process. They have cloned 12 male mice from immature Sertoli cells and have been evaluating their weight gain and serum biochemical values in a period of time. Controls were derived from natural mating and spermicidal injection. Results were as follows. Weight difference was not observed, but biochemical parameters, 2 out of 16 measured have showed significant difference. Lactate dehydrogenase (LDH) and ammonia (NH₃) were found to be significantly higher (in both 3 and 14 month old measured mice). Besides, life expectancy of cloned animals was reduced too. They began to die 311 days after birth and 10 of them died before 800 days (Fig. 1)

Fig. 1

The histological examination of necropsy of cloned mice didn't show post-mortem degeneration. Severe pneumonia, extensive necrosis in the liver and tumors (leukemia and lung cancer) were found in died cloned mice. Increased LDH amounts and high ammonium in the serum of cloned mice was explained by some hepatic damage. Some tumors were found in natural mating controls too. It is thus likely that morbidity and mortality of the cloned mice was due to a dysfunction of the liver and lungs that occurred specifically in clones.

Speaking about cloned animals, one should mention that calves produced by cloning had malfunctioning immune system. The situation with mice seemed to be similar. At 4-5 months of age the antibody productivity of the clones was significantly reduced. Phagocytic activity was lowered too. Decreased immunity is common during normal aging process and in cloned animals it is highly accelerated, causing pneumonias and other immune insufficiencies. Talking about liver necrosis, observed, authors resumed that they should be yet to be determined.

The situation with cloned animals is still very unclear. Here it was mentioned that cloned mice had short lifespan, hepatic insufficiency, reduced immune system activity; talking about Dolly she is already dead with severe pneumonia diagnosed, and her general symptoms are similar to those of cloned mice. To compare cloned calves – they too suit this company very well. They have decreased life expectancy, viability and reduced immune system activity; in addition high percentage of abortion in case of cloned animals should be mentioned too. Nevertheless two of twelve above mentioned mice clones are still alive and might have normal lifespan.

Such results suggest that cloning is possible and much promising, but still some problems and questions should be solved and answered.