Scientists like Dr. Spillstuff here are constantly working to further evaluate stem cell samples. The goal here is to unify those for cultivation and transplantation. The process that tells us the most about cell samples is called flow cytometry. Another name is cytofluorometry for those who are too lazy to hit the space bar. The process entails the use of an array of antibodies to specific markers. Different types of cells have different proteins in them. We can use these proteins to identify all kinds of cells, especially adult neural stem cells. Recently, a team of Russian scientists used a battery of 12 anitbodies for 12 protein markers that were expressed in the cells. Here's a list of the proteins they were looking for:
In order to reveal anything, these proteins have to first be visualized. This is done by incubating cells with antibodies that are labeled with fluorescent chemicals such as fluoresceinisothiocyanate (FITC) and phycoerythrine(PhE). Machines called cytofluorimeters use a method called direct dichromatic immunofluorescence to make these markers visible to the human eye. So now, the scientists know that the cells have the right proteins in them in order to be classified as stem cells.
They allow the cells to grow in petri dishes in a serum-free medium with the addition of general growth factors. These growth factors include:
These factors simply allow the cells to keep living and differentiating on their own power.
After an incubation period of a week, these cells were found to differentiate into various cell types. That is, the new cells expressed multiple different phenotypes. The pattern of differentiation was investigated by immunocytochemical methods where another series of antibodies is used. These antibodies are:
They were then fixed and processed in a solution of secondary antibodies and stained with fluorescent dye (DiI).
(R. Poltavtseva, et al)
It is also important to note that the isolation of stem cells is possible without special procedures like the one described above. Some work has been done where the isolation procedures relied on the ability of neural stem cells to proliferate rapidly in response to mitogens present in the growth medium and take over the culture (A. Villa, et al).
Since they found a whole bunch of different phenotype expressions in the cells, they concluded that it was due to the different fetuses from which the samples were drawn. Cell samples in further analyses should be more uniform in order to really make valid generalizations about neuronal development in humans. The standardization of neural multipotent cell samples is of great importance for the cultivation for transplantation. We shall now move on to a little about the process of differentiation.