Placenta is the cradle of hematopoietic stem cells
Scientists at the University of California (Los Angeles), working under the guidance of Dr. Hanna Mikkola, in experiments on mice found that hematopoietic stem cells, giving rise to all blood cells, appear in the placenta during intrauterine development.
Until now, the place of the primary formation of hematopoietic cells remained a mystery for specialists. According to Mikkol, the data obtained leave no doubt that this happens in the placenta, and will allow scientists to recreate the specific embryonic microenvironment necessary for growing hematopoietic stem cells in culture for subsequent use in the treatment of diseases such as leukemia and aplastic anemia. Currently, the authors have already begun work on reproducing the results obtained in humans.
At the present stage of the development of science, scientists can isolate embryonic stem cells and stimulate their differentiation into almost all types of cells of an adult organism. However, until now, it has been possible to turn them into full-fledged hematopoietic cells capable of self-renewal and not differentiating prematurely when administered to a patient, only by manipulating nuclear regulatory mechanisms using retroviral vectors. Unfortunately, such methods are unacceptable for practical medicine, because the use of retroviruses can cause undesirable side effects.
The creation of hematopoietic stem cells in the laboratory will significantly increase the effectiveness of the treatment of leukemia and other diseases requiring bone marrow transplantation. To date, the possibilities of carrying out this procedure are significantly limited by the lack of donor material suitable for transplantation. Given the recent success in developing a method for converting human skin cells into induced pluripotent cells similar in properties to embryonic cells, in the future these cells can be used to create non-reactive rejection of transplant material from the patient's own skin.
In an earlier study, the authors found that the placenta contains a large number of hematopoietic stem cells, but whether they form in the placenta or migrate there was unclear. In experiments on a unique mouse model – an embryo with an unbreakable heart and, accordingly, with no circulation – scientists have established that the placenta is a kind of "nursery" for hematopoietic stem cells, where they receive primary "education".
According to the results of the work, hematopoietic stem cells are formed in the large arteries of the embryo and placenta, after which they move to the vascular labyrinth of the placenta, where oxygen and nutrients are exchanged between the mother's body and the fetus, which allows these cells to actively proliferate.
Thus, the placenta provides hematopoietic cells with two niches performing different roles, the study of which will help scientists in creating a system for the cultivation of hematopoietic stem cells in the laboratory. According to the researchers, the vascular labyrinth is a source of many growth factors and cytokines, so an important task is to identify among them exactly those signaling molecules that ensure the formation of full-fledged hematopoietic cells. In addition, the authors are confident that they will be able to confirm all the results obtained when studying the human placenta.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
12.03.2008