Cell Structures Exhibit Novel Behaviors, Mimic Red Blood Cells and Liquid Crystals

Researchers at the University of Pennsylvania and Yale University have manipulated the internal, structural components of cells, creating a set of simulated cellular structures with novel mechanical properties, including one that acts like a red blood cell and another that mimics the soft, elastic behavior commonly found in novel synthetic materials called liquid crystal elastomers.

The findings point to nature's innate ability to create a variety of cell structures and behaviors using standard cell proteins and to science's potential to construct new classes of material by manipulating cell cytoplasm.

In a study reported online this month in Nature Physics, researchers fortified actin filament networks, the protein components in cell cytoplasm that help form the skeleton and the cell's capacity for movement, with protein crosslinks of varying length and elasticity.

"The resulting cell structures exhibited a number of novel and useful physical properties, depending upon the length of the filaments that formed the cell network," Dennis Discher, professor of biological engineering at Penn, said.

Those with very short actin filaments and long crosslinkers resemble the cytoskeleton of the red blood cell and remain isotropic, that is, maintain their shape under compression and shear. Since blood cells in blood flow experience hydrodynamic stresses from all directions, the isotropic properties of the simulated cells are well suited to the fluid stresses of blood flow.

Networks with longer filaments, which occur naturally in many types of animal cells, demonstrate different behavior. Loose networks with long crosslinkers are isotropic at zero stress, yet align under compression or shear, allowing these cells to adjust their cytoskeleton to the stresses in the environment. Such cell structures can be moved, or directed, as cells adjust to their surroundings.

"Semi-loose" networks have somewhat shorter crosslinks and are nematic, or thread-like at low stress, but become isotropic under dilation. "Tight" networks possess a locked-in nematic orientation, much like the cytoskeleton of the outer hair cell in the ear. This cell is responsible for the amplification of sound, and the oriented cytoskeleton helps direct sound propagation from the ear canal to the receiving neuron that interfaces to the brain.

A subset of the simulated cells, those with periodic crosslinks, demonstrate an especially unique type of super-soft behavior recently found in liquid crystal elastomers. Synthetic materials of this type have properties typified in liquid crystal displays but also the flexibility of highly elastic materials, such as latex gloves. The biologically based results highlight the fact that nature probably "did it first," and the results point the way towards the creation of new materials with novel optical, thermal and electrical properties.

The study was conducted by Discher, of Penn's School of Engineering and Applied Science, as well as Tom Lubensky, chair of Penn's Department of Physics and Astronomy in the School of Arts and Sciences, and Paul Dalhaimer of the Department of Molecular, Cellular and Developmental Biology at Yale University.

Source: University of Pennsylvania

Related stories:

Statins may prevent miscarriages
Hospital for Special Surgery researchers have found that statins may be able to prevent miscarriages in women who are suffering from pregnancy complications caused by antiphospholipid syndrome (APS), according to a study in mice. In this autoimmune syndrome, the body produces antibodies directed at phospholipids, the main components of cell membranes. This news comes from a study published in the October issue of the Journal of Clinical Investigation that is currently online in advance of print.
A link between mitochondria and tumor formation in stem cells
Researchers report on a previously unknown relationship between stem cell potency and the metabolic rate of their mitochondria –a cell's energy makers. Stem cells with more active mitochondria also have a greater capacity to differentiate and are more likely to form tumors.
On the trail of a targeted therapy for blood cancers
Investigators from the Herman B Wells Center for Pediatric Research at the Indiana University School of Medicine are focusing on a family of blood proteins that they hope holds a key to decreasing the toxic effects of chemotherapy in children and adults.
Scientists discover crucial control in long-lasting immunity
National Institutes of Health (NIH) scientists have identified a protein that plays matchmaker between two key types of white blood cells, T and B cells, enabling them to interact in a way that is crucial to establishing long-lasting immunity after an infection. Their finding may also explain why some individuals who have a genetic defect that prevents them from making this protein—called SAP—suffer from lethal infections with a common virus that otherwise is rarely fatal (Epstein-Barr virus), while others with this genetic defect have problems with B-cell lymphomas.
Mouse studies suggest daily dose of ginkgo may prevent brain cell damage after a stroke
Working with genetically engineered mice, researchers at Johns Hopkins have shown that daily doses of a standardized extract from the leaves of the ginkgo tree can prevent or reduce brain damage after an induced stroke.
Time of day influences yield for pharmacologically stimulated stem cell mobilization
A new study uncovers a previously unrecognized, species-specific impact of circadian rhythms on the production of mobilized stem cells. The research, published by Cell Press in the October 9th issue of the journal Cell Stem Cell, suggests that when it comes to collecting human stem cells for clinical transplantation, picking the right time of day to harvest cells may result in a greater yield.
Bisphenol A linked to chemotherapy resistance
Exposure to bisphenol A (BPA) may reduce the effectiveness of chemotherapy treatments, say University of Cincinnati (UC) scientists.
Scientists pinpoint key proteins in blood stem cell replication
A family of cancer-fighting molecules helps blood stem cells in mice decide when and how to divide, say researchers at the Stanford University School of Medicine. Blocking the molecules' function spurs the normally resting cells to begin proliferating strangely - making too much of one kind of cell and not enough of another. Many types of human blood cancers involve a similar disruption in the expression of that same family of molecules.

News discussion:

Physics news