Rice Bioengineers Develop Method To Grow 3-D Bone Matrix

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Rice Bioengineers Develop Method To Grow 3-D Bone Matrix

HOUSTON-- Oct. 3, 2002 -- A new study by Rice University researchers

indicates that bioengineers growing bone in the laboratory may be able to

create the mechanical stimulation needed to grow bone outside the body.

One of the greatest challenges tissue engineers face in growing bone in the

laboratory is recreating the conditions that occur inside the body. The

recipe for growing healthy bones includes not only a precise biological mix

-- bone cells called " osteoblasts " and several growth factors that

osteoblasts use to build the mineralized matrix of bones -- but also

mechanical stimulation. Astronauts whose bones become brittle after months

in orbit are a testament to the importance that mechanical stress plays in

bone growth. In orbit, their skeletons aren't subject to the everyday

stresses of gravity.

Tissue engineers at Rice placed bone marrow-derived osteoblasts from rats

into centimeter-wide plexiglass chambers containing a thin stack of titanium

fiber mesh. The samples were covered with a liquid growth medium -- a bath

of chemicals that promotes bone growth -- and sealed in an incubator. After

letting the cultures sit overnight -- to give the cells time to attach

themselves to the mesh -- engineers pumped growth medium through the

cultures for 16 days. Bone cultures were subjected to a range of three

different flow rates to provide mechanical stimulation, and another set of

cultures were grown in a motionless bath.

Results of the research appear in the current issue of the Proceedings of

the National Academy of Sciences USA.

" Researchers have used fluid flow to stimulate bone growth before, but no

one has looked at its effect on three-dimensional cultures that have been

subjected to continuous stimulation for several days, " said Tony Mikos, the

W. Professor of Bioengineering. " We found that even the lowest flow

rate produced a significant increase in the formation of mineralized bone.

Moreover, the mineralized bone that formed in samples subjected to flow was

thick and well-developed -- similar to what we find in natural bone --while

the bone matrix formed by the static samples was thin and brittle. "

Mikos said more studies are needed to determine the exact flow rate needed

to produce the optimal amount of bone matrix with the optimal

three-dimensional structure. For those who have lost a segment of bone to

cancer or injury, the technology isn't expected to result in clinical

treatment options for several years. Ultimately, however, artificial bone

could be substituted for donor tissue or surgical implants made of synthetic

materials.