After each round of cell division, cells need to increase their size and mass in preparation for the next round of division. Even in cells that do not divide, such as neurons, cell growth is important. Some neurons increase their volume ~10,000-fold after their last mitosis. In the case of neurons in particular, growth is important both during normal development and during regeneration after injury. Since most axons and dendrites find their synaptic targets early in development, the subsequent growth of neurons occurs in a manner independent of growth cone guidance. Rather, neurons lengthen with the lengthening of the body, and so it has been suggested that mechanical tension is responsible for most of the growth of neurons. Studies of neuron growth in vitro with single neurons, initially by Dennis Bray and subsequently by Steve Heidemann and co-workers, confirmed that mechanical tension is indeed a potent stimulator of neuron growth. Our work with embryonic chick forebrain neurons is consistent with these studies. The main advance that we have developed is the use of magnetic beads to apply tension to neurons. This has two advantages over glass microneedles: 1) better control of force, and 2) remote manipulation. Becaue of the latter advantage, it raises the possibility of remote manipulation of neurons (and cells in general) in the body by magnetic force. Our studies confirm the potency of mechanical force: whereas embryonic chick forebrain neurons will grow axons spontaneously after a few hours in culture, application of ~500 pN of force causes an axon to form within ~1 minute.

Our current studies are aimed at determining the cytoskeletal basis of neuron growth and the role of mechanical force in particular.

Recent Articles

Lipkow, K. and D. J. Odde, "Model for protein concentration gradients in the cytoplasm," Cellular and Molecular Bioengineering, in press.

Fischer, T.M., Steinmetz, P.N., and Odde, D.J. (2005). Robust micromechanical neurite elicitation in synapse-competent neurons via magnetic bead force application. Annals of Biomedical Engineering 9, 1229-1237.

Fass, J.N., and Odde, D.J. (2003). Tensile Force-Dependent Neurite Elicitation via Anti-β1 Integrin Antibody-Coated Magnetic Beads. Biophysical Journal 85, 623-636.

Baldi, A., Fass, J.N., DeSilva, M.N., Odde, D.J., and Ziaie, B. (2003). A micro-tool for mechanical manipulation of in vitro cell arrays. Biomedical Microdevices 5, 291-295.