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1) Stiffness of the environment helps to determine stem cell fate Stem cells are cells that have the potential to become one of multiple types of cells

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1) Stiffness of the environment helps to determine stem cell fate

Stem cells are cells that have the potential to become one of multiple types of cells. In the right conditions, a stem cell will divide into two cells: one remains a stem cell and the other develops into a specific type of cell. Ongoing research efforts seek to identify the signals that trigger a stem cell to differentiate into a certain desired cell type.

 

 

In general, we know that stem cells respond to several types of cues from their local environment:

 

 

1.	Chemical signals secreted into the environment by other cells through    ____________
2.	Direct cell-to-cell contact mediated by    on touching cells__________________________
3.	The stiffness of the surroundings

 

 

 

The following data, taken from a paper published in the research journal Science in 2006, show how sensitive certain stem cells are to the elasticity (or stiffness) of the surrounding tissue. Here, elasticity is measured in kilopascals (kPa).  From Engler, Sen, Sweeney, and Discher, "Matrix Elasticity Directs Stem Cell Lineage Specification," Cell, Vol. 126, pp. 677-689, Figure 1A. Reprinted by permission of Elsevier.

Different human tissues have different elasticities, or levels of stiffness. What is the elasticity of bone?____________________  From Engler, Sen, Sweeney, and Discher, "Matrix elasticity directs stem cell lineage specification," Cell, Vol. 126, pp. 677-689, Figure 1B. Reprinted by permission of Elsevier.

In this experiment, scientists grew multipotent stem cells (MSCs) on an artificial elastic surface coated with collagen to mimic the natural environment of the__________    , which varies in stiffness from tissue to tissue.

 

Examine the microscope images taken of MSCs grown on different surfaces over the course of 96 hours. Below, describe the effect of different elasticities on the MSCs.

On ____________________    -like surfaces, the main cell bodies shrink to small spheres.
On ________________   -like surfaces, the cells stretch out along a line.
On  _____________________  -like surfaces, the main cell bodies grow flatter.

Different cell types express different sets of genes, resulting in the production of different proteins. For example, only pancreatic cells produce and secrete insulin, and only certain immune cells produce antibodies. When MSCs are grown on surfaces with different elasticities, they start producing different proteins.

 

 

 

 

 

 

 

 

 

In the fluorescent microscope images to the left, the cells have been treated with a blue dye that specifically stains DNA to reveal the location of the  __________________  . In each row, the green fluorescence represents where a certain protein (β3-tubulin in the top row, myoD in the middle row, or CBFα1 in the bottom row) is located in these cells.

In this experiment, scientists grew multipotent stem cells (MSCs) on an artificial elastic surface coated with collagen to mimic the natural environment of the __________________   , which varies in stiffness from tissue to tissue.

 

MSCs grown on which elasticity produce the most myoD?

 

8-17 kPa

25-40 kPa

0.1-1 kPa

Which protein is most likely a bone-specific protein?

 

CBFα1

MyoD

β3-tubulin