The venture into cell biology has been ongoing since the 1800s, with the discovery of cells and the multiple complex shapes and roles they play in the human body. The idea of stem cells was somewhat of a late arrival within this field. Initially, the existence of stem cells was simply an educated hypothesis and most researchers thought all cells were directly differentiated from different cells of the embryo without any pre-cursor involved.

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In the 1900s, European scientists observed the structure of red blood cells, white blood cells and platelets and compared to the bone marrow of human beings. They found stark evidence that all the kind of cells originated from the marrow and eventually differentiated into the three different types of blood cells. Hence scientists coined the term ‘stem cells’ to describe the pre-cursor of blood cells that eventually differentiated on the basis of function.

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After years of search for proofs, the factual evidence for their existence was found the same way many huge scientific breakthroughs were made, accidentally. In the 1950s when observing the testicular germ cells of mice for studying teratocarcinomas, he noticed that teratocarcinomas from 129 different strains of inbred mice came from these germ cells while on the contrary, the germ cells showed no difference in characteristics and are not the cause for the formation of the tumour.

 

He also noticed that they never differentiated into different cell types, implying there were specific cells present for this purpose, thereby confirming the presence of stem cells as the mother cell from which different cells arose from.

However, it was not until 1963 that the first quantitative descriptions of the self-renewing activities of transplanted mouse bone marrow cells were documented by Canadian researchers Ernest A McCulloch and James E Till.

 

The experiment involved extracting the bone marrow from one mouse and observing how the marrow replenishes. Instead of bone marrow cells replicating themselves, distinct cells differentiated into different marrow cells to produce different blood cells.  This gave the idea of stem cells a final solid proof and was accepted as a scientific fact rather than hypothesis. This eventually formed the basis for bone marrow transplants for cures of certain cancers, which eventually developed to be one of the most successful methods and is also being researched as a cure for AIDs.

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After this discovery, the research on stem cells kept on entering newer frontiers. In the 1980s, as chimeric mice we classified as inefficient sources of stem cells, extraction of them from human teratocarcinomas was discovered which radically changed the industry. First attempts were made in the mid-1980s, Thomson in the US continued, first in primates then in humans, and in 1998, his group published their breakthrough. In humans, at that time inducing teratocarcinomas was not possible.

 

Instead, they were able to extract the genes responsible for the tumour in humans and induce them into immunodeficient mice yielding much more efficient stem cells. This also allowed to determine the exact phenotype human stem cells would portray.

This eventually led the discovery of a method to derive stem cells from human embryos and grow the cells in the laboratory. Human embryonic cells were allowed to divide until they reached the stem cell stage. Then stem cells were extracted from them and the embryo would be cryopreserved for future research.

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Nowadays these cells extracted can be converted into various cells in culture in response to cytokines, hormones and growth conditions. These include neural cells (neurons, glia, and oligodendrocytes) and, most recently, insulin-producing pancreas cells, cartilage and bone, cardiomyocytes, hematopoietic cells, endothelial cells and hepatocytes. 

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Modern day advances include the stem cell banks that have been popping up all over the landscape. The advent of stem cell extraction from umbilical cords and Human Exfoliated Deciduous Teeth have brought about a new change within the field of stem cells, making their extraction a much safer and easier process.