22 January 2009

Building New Cellular Infrastructure

Tissue scaffolds are the next big thing for implants of the future. Like the scaffolding we see on construction sites, the nano scaffolds are being created by Ko to reconstruct damaged tissue within the human body. Burn victims would benefit from scaffolds used to regenerate new skin. Those with failing heart valves or damaged nerves could count on scaffolds to regenerate these parts from within the patient’s own body. As healing progresses, the scaffold, being constructed from a biodegradable material, is absorbed and metabolized by the body while slowly releasing drugs to aid in the healing process. _CyborgAge
Almost every part of the body presents opportunities for scaffold bio-engineers to experiment. From the heart to the spine to the skin, all parts of the body eventually wear out and need to be replaced or regenerated. Scientists at UC Berkeley are taking an entirely new approach to bio-scaffold development. They are using viruses (bacteriophages) to build a proteinaceous infrastructure that promotes regeneration of nerve tissue.
Some biological engineers are using scaffolds made of polymers to try to mimic the supportive matrix of real tissue. Seung-Wuk Lee, a bioengineer at the University of California, Berkeley, has turned to viruses instead. "Viruses are smart materials," he says. "Once you construct the genome, you can make billions of phages, and they're self-replicating materials." The phage that Lee is working with, called M13, is long and thin like the protein fibers that make up the cellular matrices inside the body.

First, Lee and his colleague Anna Merzlyak genetically engineered M13 to display nerve-friendly proteins on their outer coats. These proteins are known to help nerve cells proliferate, adhere, and extend into long fiberlike shapes. Next, the researchers grew large numbers of the viruses in bacterial-cell hosts and dropped them into a solution containing neural-progenitor cells. These cells are more fully developed than stem cells but are still young and need coaxing to form new tissues. In the solution, the viruses align themselves like a liquid crystal, says Lee. He and Merzlyak used pipettes to inject the solution into agar, a Jell-O-like cell-culture medium, creating long, nerve-like fibers of the virus interspersed with cells. The progenitor cells then multiplied and grew the long branches characteristic of neurons. Lee says that the phage are well suited to making long, fiberlike structures such as nerve tissue but can also be made into more complex structures by varying their concentration or manipulating their position with a magnetic field. _TechnologyReview
Lee is planning to move to research inside live animals next. He is interested to discover how the immune systems of animals will react to viral construction workers hammering, drilling, and welding new infrastructure deep inside the organism.

For regenerative medicine to take that next big step forward, it will need the ability to grow specific infrastructure for every tissue and organ type that will be replaced or regenerated. Then, scientists will need to integrate growth factors and stem cells into the new matrix, and provide optimal nutrient solution. The prognosis for significant progress in this area is extremely favourable.

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