Stem cell research: In on the ground floor

by Lorien E. Menhennett

When it comes to research, stem cells are where it’s at. And I’m in on it.

Already an established treatment for bone marrow transplantation, stem cells are thought to be (possibly) capable of treating spinal cord injuries, traumatic brain injuries, stroke, Alzheimer’s disease, Parkinson’s disease, and even baldness, among many other things.

Basically, stem cells are cells that can differentiate into a range of specialized cell types and therefore regenerate tissue. For example, bone marrow stem cells (also called hematopoietic stem cells, or HSCs), once transplanted into an person without HSCs, will produce new blood cells and immune cells.

What Olga is trying to do – and I will be trying to help her with this summer – is to prove that the mouse lung epithelial cells she has collected are indeed stem cells. So far they have some of the indicators of stem cells, but proving that they are is more complicated. (I will get to that later.)

The implication would be that if those cells were re-injected into another mouse, one with damaged lung tissue, the stem cells would (hopefully) be able to differentiate into the needed types of cells and therefore regenerate the lung tissue.

So how does one go about proving that cells are, indeed, stem cells? Well, there is a complicated answer and then there is a complicated answer. I will try to simplify it as best I can (with my limited but expanding knowledge of biochemistry and genetics).

What you need to do is prove that your cells contain certain “stem cell markers.” These markers are used to (obviously) identify and isolate stem cells.

So what is a stem cell marker? Good question. Here is a good answer, from the NIH’s website:

What are stem cell markers? Coating the surface of every cell in the body are specialized proteins, called receptors, that have the capability of selectively binding or adhering to other “signaling” molecules. There are many different types of receptors that differ in their structure and affinity for the signaling molecules. Normally, cells use these receptors and the molecules that bind to them as a way of communicating with other cells and to carry out their proper functions in the body. These same cell surface receptors are the stem cell markers. Each cell type, for example a liver cell, has a certain combination of receptors on their surface that makes them distinguishable from other kinds of cells. Scientists have taken advantage of the biological uniqueness of stem cell receptors and chemical properties of certain compounds to tag or “mark” cells. Researchers owe much of the past success in finding and characterizing stem cells to the use of markers.

So what Olga and I are going to do is test for these stem cell markers in her batch of cells. But how do we do that? Another good question, and one I don’t completely understand quite yet. But I’m getting there.

_gelWhat I do know is that we will be using a technique called “gel electrophoresis” (see an example at right) to study the gene expression of the RNA that Olga and I isolated earlier this week. (When genes are expressed, they produce proteins – hopefully, the stem cell marker proteins that we are looking for.) The first step is to use “reverse transcription” to turn the RNA into cDNA. Then you load your cDNA into little wells (holes, really) in a sticky gel matrix which sits in a plastic case. After that, you run an electric current through the gel matrix. The current causes the cDNA molecules to move through the matrix at different rates, determined largely by their mass. After completing the electrophoresis, you can stain the molecules to make them visible (and see which ones, if any, were expressed in your reaction).

We will be looking to see whether particular stem cell markers – which will be evidenced in the staining by the bands we see (or don’t see) – are present in our cell sample. The stem cell markers we are looking for include SOX9, SOX2, and GATA6, among a few others (I mostly remembered the SOX ones because I used to be a White Sox fan … go figure).

I’m still a little fuzzy on some of the details – not because Olga didn’t explain them to me, but because my background in biochemistry and genetics is just slightly lacking – but I’m beginning to get the picture. What we’re doing is part of the infant stages of stem cell research, and won’t likely have practical applications for some time to come. But when it does, the potential will be earth-shattering. Pretty exciting stuff for someone who had never worked in a research lab before this Tuesday, eh?