Chris Smith

The CytoMatrix: Reloaded

Helping stem cells to boldly grow, where no cells have grown before.

A material designed originally to help rockets blast into space is now helping scientists in America to grow stem cells in large numbers outside the body, potentially ushering in a new field of medicine where doctors prescribe cells rather than drugs.

Figure 1: To the naked eye, the Cytomatrix looks like sponge.

Known as the Cytomatrix, the material is made by coating a carbon

skeleton with metals at very high temperatures. With the naked eye

it resembles a hard piece of sponge (figure 1, right), but

under a microscope it is almost indistinguishable from bone marrow

(see figures 2 and 4 below).

"When you take stem cells out of the body and add them to

our matrix," says Michael Rosenzweig, chief scientific officer

at Cytomatrix, "they can grow in three-dimensions, the way

they normally do in the body".

Because it so closely mimics the natural environment of the body,

stem cells grown on the Cytomatrix secrete their own growth factors

which means they can multiply, producing 4 to 6 times as many cells,

whilst retaining their full stem cell characteristics.

Until now, when scientists tried to grow stem cells outside the

body, powerful growth factors were needed to make the cells divide.

Whilst this produced a large increase in the number of cells, it

had the unfortunate consequence of also causing the stem cells to

lose valuable characteristics such as the potential to turn into

any cell type in the body, and the ability to repair damaged or

diseased tissues.

The remarkable potential of the Cytomatrix to overcome this problem

was first noticed after it was tested as a bone implant for use

in joint replacements. Researchers were surprised to see not only

the hard outer part of the bone growing into the porous surface

of the matrix, but also bone marrow cells thriving on it too.

Figure 2: Under the microscope, Cytomatrix closely resembles bone marrow

Subsequent tests showed that the matrix could safely be implanted

into the bone marrow cavity where it could support the growth of

the full range of bone marrow and blood cells (figure 3).

"This led us to suspect that it might be able to provide a

surrogate bone marrow for the expansion of stem cells outside the

body," explains Mark Pykett, one of the scientists working

on the Cytomatrix.

One source of stem cells that scientists and doctors are particularly

excited about is umbilical cord blood which can be harvested from

the discarded placenta and cord of a newborn baby. Cord blood stem

cells are viewed as extremely promising candidates for stem cell

therapy because collection is simple and risk free, and there are

fewer complications, such as graft versus host disease, when umbilical

cord blood stem cells are donated to unrelated patients, possibly

because these cells are more 'tolerant' than stem cells obtained

from other tissues.

Figure 3: Stem cells growing on the Cytomatrix

Owing to their therapeutic potential, there are now a number of

companies around who, for a small fee, will store your umbilical

cord blood stem cells until you need them. Indeed, last year about

10% of American newborns 'banked' their cord blood stem cells in

this way.

But, like most stem cells, cord blood stem cells are only present

in limited numbers and it is often difficult to obtain them in sufficient

amounts to successfully to treat a patient. At the same time, the

number of conditions that can be tackled using stem cells is rising

exponentially; there are now over 70 different diseases that can

be treated this way, meaning that, for most people, a single cord

blood collection will probably not be sufficient for a lifetime's

needs.

It was with this problem in mind that Cordlife, Singapore's first

umbilical cord blood stem cell bank, recently announced an US$11

million deal to acquire Cytomatrix, with the aim of using this technology

to grow umbilical cord blood stem cells. This approach has been

successfully tested in animals, and Cordlife are now about to begin

clinical trials in human patients.

Crucially, the ability to expand the number of available stem cells

makes it possible to treat multiple diseases and, potentially, multiple

patients. "If we can grow the stem cells," explains Soren

Müller Bested, Cordlife's chief technology officer, "then

it may also be possible to use some of the extra cells generated

to treat other people who also need a stem cell transplant but have

no available stem cells of their own".

The other major benefit of establishing a pool of your own cells

is that, rather than using stem cells only as a last resort, doctors

can begin to prescribe prophylactically, to help offset some of

the effects of ageing.

But for those craving immortality, be warned, "we're not talking

about eternal life, just allowing people to stay healthier when

they get older," says Müller Bested.

Figure 4: The Cytomatrix as it appears under the electron microscope (EM). In each case, the scale bar is 100µm long (0.1 mm)

 

Acknowledgements

I am indebted to Soren Müller Bested, Sher Min Gaspar,

Ronald Hee, Ian Brown and Steven Fang , from Cordlife, Singapore,

and Mark Pykett and Michael Rosenzweig from Cytomatrix, Boston,

US, for their help in putting together this article and the accompanying

radio interview.

- February 2005

About the Author

Chris Smith is a clinical lecturer in virology at Cambridge University and the founder and managing editor of the Naked Scientists