Orthopedic implants dipped in growth factors stimulate bone, blood vessel, or cartilage growth.
MADISON – When William Murphy works with some of the most powerful tools in biology, he thinks about making tools that can fit together. These constructions sound a bit like socket wrenches, which can be assembled to turn a half-inch nut in tight quarters, or to loosen a rusted-tight one-inch bolt using a very persuasive lever.
The tools used by Murphy, an associate professor of biomedical engineering and orthopedics and rehabilitation at University of Wisconsin-Madison, however, are proteins, which are vastly more flexible than socket wrenches -- and roughly 100 million times smaller. One end of his modular tool may connect to bone, while the other end may stimulate the growth of bone, blood vessels or cartilage.
To grow replacement tissue in situ (in place in our bodies) we need the ability to create 3-dimensional biochemical environments that orchestrate the right sequence of signals to guide tissue growth to repair damaged areas. While stem cells get a great deal of attention for many types of damage the problem isn't the lack of cells to do the repair. Rather, the challenge is to guide cells so they go to the right places and create the right 3-dimensional structures.
On February 4th and 6th, at the Orthopedic Research Society meeting in San Francisco, Darilis Suarez-Gonzalez and Jae Sung Lee of the Murphy lab are reporting that orthopedic implants "dip-coated" with modular growth factors can stimulate bone and blood vessel growth in sheep.
For many years, medical scientists have been fascinated by growth factors -- proteins that can stimulate tissues to grow. But these factors can be too effective or not specific enough, leading to cancer rather than the controlled growth needed for healing.
What's still needed: variable control of which signals get sent thru time. What happens naturally during development where limbs and organs grow is much harder to bring about for one area in an already adult body. All the cells in developing tissue send signals that coordinate their changes in a very complex sequence. Replicating that is not easy. Also, the adult tissue contains plenty of aged cells that are not functioning optimally. More youthful replacement cells would do a better job of repair.
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