Prof. Mohamed Labib Salem *

Of animals, what God has endowed with the ability to bear and freeze the pregnancy in her womb and then continue to complete it until birth, so does this happen in a person ?! How can understanding this process help us in the treatment of cancer?

Pregnancy, and then pausing until the right time to give birth, seems like a science fiction, but for many mammals, what is known as "diaphragm" is an essential part of raising their young.

Although scientists have recorded since the fifties of the last century that some animals have this ability to freeze pregnancy after its occurrence, it is now clear how this can teach us valuable lessons about human pregnancy and dealing with stem and cancer cells.

There are more than 130 types of mammals that can temporarily stop their pregnancy, and the layoff can last from two days to 11 months.

This occurs in most types of mammals except for some bats, which do this later. Fetal discontinuation - that is, the suspension of pregnancy - usually occurs when the fetus is a small ball consisting of about 80 cells, before it sticks to the uterine wall.

Not only is this one group of mammals, but it seems that different species have evolved their ability to reproduce. It has been found that most carnivores can temporarily stop carrying them, including all bears, as well as many rodents, deer, and all types of Australian kangaroos.

Why do these animals stop pregnancy?
Although the answer to this question is not fully known, the main reason why pregnancy is terminated may be the need for these mammals to separate marriage and childbirth. It is known that some animals are vulnerable to extinction due to climate change, migration or human intervention in hunting.

Therefore, these animals carry a repeated pregnancy immediately after birth in order to continue to produce new generations so that the gender of this species is not subjected to extinction, but the new pregnancy after birth strains the mother and reduces the opportunity to breastfeed the young. Therefore, these mammals resort to pregnancy, and then freeze this pregnancy to hit two birds with one stone.

On the one hand it ensures pregnancy and the survival of the type, and on the other hand it guarantees rest until the appropriate time for birth to avoid repeated birth. Thus, the animal gives more attention to newborn infants, as the stress in breastfeeding causes a temporary pause during lactation, then these mammals will resume pregnancy, as soon as they wean their infants.

Another reason that might cause mammals to stop their pregnancy temporarily, may be the need to give birth when the appropriate time and season comes.

For example, "mink" mating with the beginning of March, but temporarily stops embryos until after the spring equinox (21 March), when the days are long in the homes of the northern hemisphere. Here, the mammal ensures that its young are born in the spring when conditions improve, not in the winter.

The Australian kangaroo also combines these two methods, breastfeeding in the first half of the year, and then suspending the pregnancy for about a year until birth in January.

This ensures that the young ones leave the mother cavity in the following spring instead of the hot Australian mid summer. Because animal behavior is mostly instinctive, especially in pregnancy and childbirth related to sex and species survival, this pregnancy freeze is programmed and not optional by the animal.

What can we learn from suspending pregnancy in animals?
The discovery of the timing of the lamb suspension first dates back to 1854, after hunters in Europe noticed that deer lamb seemed to be longer than usual. Scientists have known this process since then, and this has helped them to understand more about these basic reproductive processes in all mammals.

However, it took until 1950 when the knowledge of pregnancy increased enough to be able to confirm what the hunters observed 100 years ago.

But how this process works at the molecular level, is still a scientific puzzle for scientists. Until recently, there was no link between the types of animals that used this process. Nor does there appear to be a uniform mechanism for how pregnancy is temporarily stopped.

Even the hormones that control this scientific occurrence differ among groups of mammals. However, research now indicates that regardless of the hormones that affect the womb, molecular signals between the womb and the fetus are preserved, at least in some animals such as rodents.

In an exciting experiment, researchers in Poland temporarily suspended fetuses in sheep (in which there is no pregnancy suspension) by transferring them to the womb of mice, and then returning them to the womb of the sheep that were born without causing any bad effects. This experience suggests that pregnancy suspensions may occur in all mammals, including humans.

Is it possible to stop pregnancy in pregnant women?
Stopping pregnancy is unlikely to become the norm in humans. For this to happen in humans, a woman is required to know that she is pregnant within five days of pregnancy, the time when most types of animals begin to suspend their pregnancy, when the fetus is a small ball consisting of about 80 cells, as we mentioned. On the other hand, understanding how pregnancy stops may help in understanding how healthy fetuses are formed.

It is interesting that the stage at which the fetus stops dividing (fetal cessation) in animals is the same as in the IVF process at which the embryo is transferred to the womb. Therefore, understanding the Diapause process can help us improve the way we grow embryos and how to identify the "best" fetus to be transferred.

Fetal discontinuation can also help to create better stem cells and find new treatments for cancer, as the first stem cells were ever isolated by scientists, they came from a rat fetus during the termination of pregnancy, which is the stage when each fetal cell is a stem cell , Which is also similar to many of the characteristics of cancer stem cells.

Therefore, an understanding of the embryonic stopping process at the molecular level is sure to lead to new therapies to stop cell division or to identify markers of tumor stem cells, which are believed to be responsible for the origin and return of the malignant tumors.

Therefore, future studies on the process of stopping the pregnancy after its occurrence to identify the cellular and molecular mechanisms behind this phenomenon are very important to reveal its secrets and benefit from them.

And who knows, we may discover in the future a way in which doctors can stop the pregnancy after it occurs in women and then return it at the time the wife wants when social, financial or health conditions are appropriate.

The topic appears from science fiction, but we have learned in the past fifty years that a lot of science fiction has become a reality that we use in our daily lives.
_______________
* Professor of Immunology, Faculty of Science, Tanta University
This article is published by the Arab Scientific Society Organization website.