Proof of the existence of stem cells is the famous experiments of James Till and Ernest McCulloch in the 50-60s. They created radiation chimeras, irradiating recipient mice in a lethal dose, and the death of animals was prevented by bone marrow transplantation from the donor animal. These authors have managed to prove experimentally and mathematically that blood production in deadly irradiated animals can be restored by transplanting a single cell that could differentiate into a variety of blood cells.
Already in 1968, E. Donnall Thomas has successfully performed a human bone marrow transplant. He did to man what Till and McCulah did to their mice. In 1990, he received the Nobel Prize for "Discovery of Organ and Cell Transplantation in the Treatment of Diseases".
Such "young" cells by the middle of the twentieth century were already called stem cells, actually by this period the concept of the so-called "unitary theory of hematopoiesis" was already quite formed. As it turned out later, several other important tissues of the body have their own stem cells.
Alexander Maksimov graduated from the Military Medical Academy in 1896, but before graduating he was actively engaged in tissue research in the pathology and anatomy room of Professor Vinogradov. After defending his thesis, he went to Germany for an internship.
He was very interested in inflammation, especially in the development of cellular reactions. While in Freiburg at the pathology laboratory of the local university, he took up the research proposed by its head, Ernst Ziegler.
At that time (1900) it was already known that some cells functioned in the tissues during the inflammatory reaction. These are some types of leukocytes and cells capable of producing intercellular protein collagen. Biological sense: at the time of damage, leukocytes destroy foreign particles or their own damaged tissues, and they are replaced by builders capable of repairing the damage.
Using the so-called "Ziegler's chambers" - two interlocking cover glasses implanted under the skin of animals - Maksimov was able to track by hours and days which cells and in what sequence come into the source of inflammation. It was then that the concept was born.
Studies of the twentieth century have not confirmed the validity of this hypothesis. But from biology, it is known that such cells of dual-purpose exist.
At the end of this work, Maksimov published a scientific article in which he used the then not fashionable word StammZelle - stem cell - in addition to polyblasts. It happened 7 years before the triumphant report on the society of hematologists (1909), where he set out experimental proof of his concept of development of all blood cells from one single - hematopoietic stem cell.
There is a legend that it was Alexander Alexandrovich who coined the term "stem cell". This is not the case. It was used before, but very rarely. German embryologists are H. Scshridde and V. Hacker. Maksimov wrote about them in 1902, implying simply the initial cells for the transformation processes:
"...the natural internal architecture of the newly described young giant cells and the structural uniqueness of their components, which are still fully represented in all the details of the types of initial polyballoys, are lost and changed, and so thoroughly that in the final giant cells almost nothing more remains of the described, except for the general noticeable similarity with stem cells - polyballoons" (1902).