Cytoskeletal Mechanics - Mofrad and Kamm
Preface
Although the importance of the cytoskeleton in fundamental cellular processes such
as migration, mechanotransduction, and shape stability have long been appreciated,
no single theoretical or conceptual model has emerged to become universally accepted.
Instead, a collection of structural models has been proposed, each backed
by compelling experimental data and each with its own proponents. As a result, a
consensus has not yet been reached on a single description, and the debate continues.
One reason for the diversity of opinion is that the cytoskeleton plays numerous
roles and it has been examined from a variety of perspectives. Some biophysicists
see the cytoskeleton as a cross-linked, branched polymer and have extended previous
models for polymeric chains to describe the actin cytoskeleton. Structural engineers
have drawn upon approaches that either treat the filamentous matrix as a continuum,
above some critical length scale, or as a collection of struts or beams that resist
deformation by the bending stiffness of each element. Others observe the similarity
between the cell and large-scale structures whose mechanical integrity is derived
from the balance between elements in tension and others in compression. And still
others see the cytoskeleton as a gel, which utilizes the potential for phase transition
to accomplish some of its dynamic processes. Underlying all of this complexity is the
knowledge that the cell is alive and is constantly changing its properties, actively, as
a consequence of many environmental factors. The ultimate truth, if indeed there is a
single explanation for all the observed phenomena, likely lies somewhere among the
existing theories.
As with the diversity of models, a variety of experimental approaches have been
devised to probe the structural characteristics of a cell. And as with the models,
different experimental approaches often lead to different findings, often due to the
fact that interpretation of the data relies on use of one or another of the theories.
But more than that, different experiments often probe the cell at very different length
scales, and this is bound to lead to variations depending on whether the measurement
is influenced by local structures such as the adhesion complexes that bind a bead to
the cell.
We began this project with the intent of presenting in a single text the many and
varied ways in which the cytoskeleton is viewed, in the hope that such a collection
would spur on newexperiments to test the theories, or the development of newtheories
themselves. We viewed this as an ongoing debate, where one of the leading proponents
of each viewpoint could present their most compelling arguments in support of their
model, so that members of the larger scientific community could form their own
opinions.
As such, this was intended to be a monograph that captured the current state of a
rapidly moving field. Since we began this project, however, it has been suggested that
this book could fill a void in the area of cytoskeletal mechanics and might be useful
as a text for courses taught specifically on the mechanics of a cell, or more broadly in
courses that cover a range of topics in biomechanics. In either case, our hope is that
this presentation might prove stimulating and educational to engineers, physicists,
and biologists wishing to expand their understanding of the critical importance of
mechanics in cell function, and the various ways in which it might be understood.
Finally, we wish to express our deepest gratitude to Peter Gordon and his colleagues
at Cambridge University Press, who provided us with the encouragement, technical
assistance, and overall guidance that were essential to the ultimate success of this
endeavor. In addition, we would like to acknowledge Peter Katsirubas at Techbooks,
who steered us through the final stages of editing.
Download
*
Preface
Although the importance of the cytoskeleton in fundamental cellular processes such
as migration, mechanotransduction, and shape stability have long been appreciated,
no single theoretical or conceptual model has emerged to become universally accepted.
Instead, a collection of structural models has been proposed, each backed
by compelling experimental data and each with its own proponents. As a result, a
consensus has not yet been reached on a single description, and the debate continues.
One reason for the diversity of opinion is that the cytoskeleton plays numerous
roles and it has been examined from a variety of perspectives. Some biophysicists
see the cytoskeleton as a cross-linked, branched polymer and have extended previous
models for polymeric chains to describe the actin cytoskeleton. Structural engineers
have drawn upon approaches that either treat the filamentous matrix as a continuum,
above some critical length scale, or as a collection of struts or beams that resist
deformation by the bending stiffness of each element. Others observe the similarity
between the cell and large-scale structures whose mechanical integrity is derived
from the balance between elements in tension and others in compression. And still
others see the cytoskeleton as a gel, which utilizes the potential for phase transition
to accomplish some of its dynamic processes. Underlying all of this complexity is the
knowledge that the cell is alive and is constantly changing its properties, actively, as
a consequence of many environmental factors. The ultimate truth, if indeed there is a
single explanation for all the observed phenomena, likely lies somewhere among the
existing theories.
As with the diversity of models, a variety of experimental approaches have been
devised to probe the structural characteristics of a cell. And as with the models,
different experimental approaches often lead to different findings, often due to the
fact that interpretation of the data relies on use of one or another of the theories.
But more than that, different experiments often probe the cell at very different length
scales, and this is bound to lead to variations depending on whether the measurement
is influenced by local structures such as the adhesion complexes that bind a bead to
the cell.
We began this project with the intent of presenting in a single text the many and
varied ways in which the cytoskeleton is viewed, in the hope that such a collection
would spur on newexperiments to test the theories, or the development of newtheories
themselves. We viewed this as an ongoing debate, where one of the leading proponents
of each viewpoint could present their most compelling arguments in support of their
model, so that members of the larger scientific community could form their own
opinions.
As such, this was intended to be a monograph that captured the current state of a
rapidly moving field. Since we began this project, however, it has been suggested that
this book could fill a void in the area of cytoskeletal mechanics and might be useful
as a text for courses taught specifically on the mechanics of a cell, or more broadly in
courses that cover a range of topics in biomechanics. In either case, our hope is that
this presentation might prove stimulating and educational to engineers, physicists,
and biologists wishing to expand their understanding of the critical importance of
mechanics in cell function, and the various ways in which it might be understood.
Finally, we wish to express our deepest gratitude to Peter Gordon and his colleagues
at Cambridge University Press, who provided us with the encouragement, technical
assistance, and overall guidance that were essential to the ultimate success of this
endeavor. In addition, we would like to acknowledge Peter Katsirubas at Techbooks,
who steered us through the final stages of editing.
Download
*