A third variable is the density of the DNA on the cell surface. By controlling how many artificial sugars the cells express, the researchers can control the DNA surface density. The greater the density, the faster the cells bind to one another.
Bertozzi says more variables for controlling cell assemblies are possible. "For example, it might be possible to cluster DNA strands on specific cellular structures. Thus, distribution of DNA on the cell surface might be yet another parameter we can exploit to guide cell-cell interactions."
Building complex microtissues one step at a time
By controlling these variables to assemble small cellular structures, then separating the desired structures from unwanted ones and unreacted cells and assembling more cells on the purified collection then repeating the steps again the researchers can synthesize large, complex microtissues in much the same way a synthetic organic chemist assembles a complex molecule.
Bertozzi and Gartner applied these methods to build a signaling network where one kind of cell controls the growth of a second kind of cell. They maintained the survival and replication of hematopoietic progenitor cells (a kind of stem cell for blood cells), which depend on the presence of the growth factor interleukin-3, by combining them in microtissues with CHO cells (Chinese hamster ovary cells) that were engineered to secrete interleukin-3.
When the two cell types were randomly mixed, the stem cells didn't grow. But structured microtissues built from the two cell types stimulated their own growth, forming a simple artificial signaling network that behaved much like the natural network
|Contact: Paul Preuss|
DOE/Lawrence Berkeley National Laboratory