As we age, the cushioning cartilage between our joints begins to wear down, making it harder and more painful to move. Known as osteoathritis, this extremely common condition has no known cure; if the symptoms can’t be managed, the affected joints must be surgically replaced.
Now, researchers are exploring whether their specially designed nanoparticles can deliver a new inflammation inhibitor to joints, targeting a previously overlooked enzyme called sPLA2.
The normal function of sPLA2 is to provide lipids (fats) that promote a variety of inflammation processes. The enzyme is always present in cartilage tissue, but typically in low levels. However, when the researchers examined mouse and human cartilage taken from those with osteoarthritis, disproportionately high levels of the enzyme were discovered within the tissue’s structure and cells.
“This marked increase strongly suggests that sPLA2 plays a role in the development of osteoarthritis,” said the study’s corresponding author, Zhiliang Cheng, PhD, a research associate professor of Bioengineering. “Being able to demonstrate this showed that we were on the right track for what could be a potent target for the disease.”
The next step was for the study team – which included lead author Yulong Wei, MD, a researcher in Penn Medicine’s McKay Orthopaedic Research Laboratory – to put together a nanoparticle loaded with an sPLA2 inhibitor. This would block the activity of sPLA2 enzyme and, they believed, inflammation. These nanoparticles were mixed with animal knee cartilage in a lab, then observed as they diffused deeply into the dense cartilage tissue. As time progressed, the team saw that the nanoparticles stayed there and did not degrade significantly or disappear. This was important for the type of treatment the team envisioned.
A recent study published in Science Translational Medicine announces a discovery which could halt cartilage degeneration caused by osteoarthritis: “These researchers showed that they could target a specific protein pathway in mice, put it into overdrive and halt cartilage degeneration over time. Building on that finding, they were able to show that treating mice with surgery-induced knee cartilage degeneration through the same pathway via the state of the art of nanomedicine could dramatically reduce the cartilage degeneration and knee pain.” This development could eventually lead to treating osteoarthritis with injection rather than more complicated surgery.
Zhiliang Cheng, Ph.D., a research assistant professor in the Department of Bioengineering at the University of Pennsylvania, has received an R01 grant from the National Institute of Neurological Disorders and Stroke to study chronic pain. The grant, which provides nearly $1.7 million over the next five years, will support the work of Dr. Cheng, Bioengineering Professor Andrew Tsourkas, and Vice Provost for Education and Professor Beth Winkelstein, in developing a novel nanotechnology platform for greater effectiveness in radiculopathy treatment.
Based on the idea that phospholipase-A2 (PLA2) enzymes, which modulate inflammation, play an important role in pain due to nerve damage, the group’s research seeks to develop PLA2-responsive multifunctional nanoparticles (PRMNs) that could both deliver anti-inflammatory drugs and magnetic resonance contrast agents to sites of pain so that the molecular mechanisms at work in producing chronic pain can be imaged, as well as allowing for the closer monitoring of treatment.
This research builds on previous findings by Drs. Cheng, Tsourkas, and Winkelstein. In a 2011 paper, Drs. Tsourkas and Winkelstein used superparamagnetic iron oxide nanoparticles to enhance magnetic resonance imaging of neurological injury in a rat model. Based on the theory of reactive oxygen species playing a role in pain following neural trauma, a subsequent paper published in July with Sonia Kartha as first author and Dr. Cheng as a coauthor found that a type of nanoparticle called polymersomes could be used to deploy superoxide dismutase, an antioxidant, to sites of neuropathic pain. The current grant-supported study combines the technologies developed in the previous studies.
“To the best of our knowledge, no studies have sought to combine and/or leverage this aspect of the inflammatory and PLA2 response for developing effective pain treatment. We hypothesize that this theranostic agent, which integrates both diagnostic and therapeutic functions into a single system, offers a unique opportunity and tremendous potential for monitoring and treating patients with direct, clinically translational impact,” Dr. Cheng said.