Research on hyaluronan polymer for cartilage repair

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Rheumawire

Mar 24, 2004

Research on hyaluronan polymer for cartilage repair

San Francisco, CA - Repairing damaged cartilage is still a far-off dream

in osteoarthritis (OA) research, but experimental studies point to how

it may be done in the future.

At the recent Orthopedic Research Society 2004 meeting, a group of

researchers from Duke University described their work with a hyaluronan

polymer that turns from liquid into solid after laser activation [1].

The gel could be inserted into a damaged joint in its liquid form, so

that it would pour over and fill up cartilage tears and ragged wound

margins; laser treatment would then transform it into a solid that fills

the defect and provides supportive scaffolding for new cartilage growth.

At the meeting, the researchers described studies in rabbits, also

detailed in the March 2004 issue of the ls of Biomedical Engineering

[2].

" We feel that the outcomes from this study suggest that therapies like

this one hold promise for future, successful cartilage-repair

procedures, " say the researchers, headed by Dr Lori Setton (Pratt School

of Engineering, Duke University, Durham, NC). They were working in

conjunction with orthopedic surgeon Dr T Vail.

" Cartilage is a tissue that does not have the ability to heal itself, so

there cannot be any healing without outside intervention, " says Vail in

a press release issued by Duke University. " There are still many hurdles

and challenges to overcome, but we have been very encouraged by the

positive results to date. The bringing together of the expertise of the

disparate fields of engineering and medicine will yield breakthroughs

necessary to advance biomedical research. "

In the rabbit studies, the light-activated polymer hydrogel

(photo-cross-linked hyaluronan) stimulated new cartilage growth in

knee-joint cartilage defects. The polymer creates a protective cap over

the cartilage defects, enabling joint movement, says Setton. At the same

time, it " creates a scaffold of support that fills the defect and

provides the correct physical and chemical cues to enable cells that

move into the defect to differentiate appropriately into cartilage

cells. "

In further, recently completed studies, Vail applied the hyaluronan

polymer to animal joint wounds in an operative procedure. After 2 weeks,

cross-sections showed that the material integrated well within existing

cartilage tissue and encouraged cells to infiltrate and lay down new

cartilage growth.

The polymer also showed signs of degrading, something that needs to

happen as new tissue grows to replace it, Setton comments. More work is

needed to optimize the properties of the polymer, she points out - for

instance, to establish the pore size that optimizes nutrient diffusion

and cell movement, how much mechanical strength the polymer needs to

maintain new cells as they grow, and how quickly it needs to degrade.

Ideally, Setton says, she would like to develop a treatment that lasts

for at least 10 years.

" If we can heal lesions in joint cartilage with this type of bridge

therapy, we could prevent end-stage osteoarthritis that leads to knee

replacements, " she says.

Zosia Chustecka

Sources

1. Nettles DL, Hsu D, Vail TP, et al. Presentation: In situ

crosslinkable hyaluronan. San Francisco, CA: Orthopedic Research

Society: 2004 meeting; March 7-10, 2004:Paper no 202.

2. Nettles DL, Vail TP, MT, and Setton LA. Photocrosslinkable

hyaluronan for articular cartilage repair. Ann Biomed Eng 2004;

32(3):391-397.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org