Evaluation of a polyacrylamide hydrogel in the treatment of
osteoarthritis: A pilot study in goats
The objective of this study was to evaluate the use of a polyacrylamide hydrogel (PAAG) in the treatment
of osteoarthritis. PAAG is polymers obtained by the polymerization of acrylamide and are considered
non-toxic because of the inability to pass through biological membranes due to their large size (1). PAAG
is hydrophilic, biodegradable, non-degradable, and consists of 97.5 % water and 2.5 % polyacrylamide.
PAAG has been used for years in the treatment of facial lipo-atrophy in HIV patients (2), as a bulking
agent in the treatment of stress urinary incontinence in women (3), and in the aesthetic industry. The
filling effect is achieved entirely by the gel itself and will stay at the injection site and allow ingrowth of
vessels and cells via a fibrous network (2). After a few months the gel will be entirely integrated with the
surrounding tissue.
This pilot study in goats has been approved by the Danish Animal Experiments Inspectorate and will
focus on the mode of action of PAAG in an osteoarthritic joint. Osteoarthritis was created in one knee
joint of 6 healthy, adult goats using an approved experimental model (4). After a post-operative period of
14 days, the goats were allowed free exercise for three months in order to develop osteoarthritis. After
three months, 4 goats were treated with the hydrogel locally in the operated joint and two goats had a
placebo in the joint. All goats had MRI before surgery, before treatment and with 1-2 months apart after
treatment until euthanasia,. The goats have been trained to walk on a treadmill so lameness was evaluated
both on the ground and on treadmill. Blood samples were obtained before surgery and during every MRI
session until euthanasia. Synovial fluid samples were obtained before surgery and after euthanasia. After
euthanasia, the elastance of the joint capsule from the operated and non-operated joint will be measured
and compared and the joint will undergo normal histopathological examination with focus on the synovial
membrane, subchondral bone, and cartilage.
The study is currently still in process, but preliminary clinical examinations of the goats on the ground
and on treadmill show very promising results.
References;
1. Fernández-Cossío, S; Castaño-Oreja, M.T. (2006): Biocompatibility of Two Novel Dermal
Fillers: Histological Evaluation of Implants of a Hyaluronic Acid Filler and a Polyacrylamide
Filler. Plastic & Reconstructive Surgery, 117 (6), 1789-1796
2. Negredo, E., Puig, J., Aldea, D., Medina, M., Estany, C., Pérez-Álvarez, N., et al. (2009). FourYear Safety with Polyacrylamide Hydrogel to Correct Antiretroviral-Related Facial Lipoatrophy.
Aids Research and Human Retroviruses, 25(4), 451-455.
3. Lose, G., Mouritsen, L., & Nielsen, J. (2006). A new bulking agent (polyacrylamide hydrogel) for
treating stress urinary incontinence in women. British Journal of Urology International, 98, 100117.
4. Didier, L., O'Byrne, E., Wasvary, J., & Pellas, T. (2006). In vivo MRI of cartilage pathogenesis in
surgical models of osteoarthritis. Skeletal Radiology, 35, 555-564.