Drug-loaded nanoparticles may reduce arthritis pain when injected

Drug delivery nanoparticles may be useful in treating osteoarthritis. In mice with signs of symptoms, a single injection of the particles relieved pain for several months.

Osteoarthritis is the most common form of arthritis and is approximately 530 million people worldwide. It occurs when the cartilage that cushions bones breaks down, causing joint stiffness and pain. Treatment options for this condition are limited, and there is no treatment to prevent cartilage degeneration.

Previous research has shown that a drug called pazopanib may help reduce osteoarthritis pain. However, the effect only lasts for a few days.So Heejeong Im Sampeng University of Illinois at Chicago and colleagues have developed a method of administration that extends release.

The researchers encapsulated pazopanib within nanoparticles that have already been approved by the U.S. Food and Drug Administration to deliver other drugs. They then injected the nanoparticles into the knees of 16 mice, and found that half of them had early signs of osteoarthritis, and half had advanced signs. The same number of animals received a dummy injection of nanoparticles without pazopanib.

Because it is difficult to assess joint pain in animals, the researchers used the widely accepted idea that individuals experiencing pain, such as joint pain, also become more sensitive to physical touch. and instead focused on rodent sensitivities.

Immediately after treatment, the researchers assessed how quickly the mice removed one paw from the uncomfortable hot plate. Mice with early or advanced osteoarthritis took significantly longer to remove their paws when given pazopanib rather than a dummy injection, suggesting that pazopanib nanoparticles rapidly reduced joint pain. I did. The researchers then repeated the hot plate test and found similar effects after two months in the advanced osteoarthritis group and after three months in the early osteoarthritis group. This means that pazopanib nanoparticles provide effective pain relief over several weeks. Animals treated with pazopanib also had less cartilage degeneration, indicating that nanoparticles may slow the progression of osteoarthritis.

But just because a treatment works in mice doesn't mean it will work in humans, Sampen says. The researchers plan to explore other ways to assess pazopanib's analgesic properties in animals. One approach, the researchers say, is to analyze how people walk and use their limbs to make sure the drug reduces joint pain.