Fluorescent Probe Tracks Knee Osteoarthritis
A fluorescent probe may make it easier to diagnose and monitor osteoarthritis, a painful joint disease affecting nearly 27 million Americans, according to a study led by researchers at Tufts University School of Medicine (TUSM) and the Sackler School of Graduate Biomedical Sciences at Tufts and published in the February issue of Arthritis & Rheumatology.
A release from Tufts explains that the disease is often detected late in development after painful symptoms occur. Earlier diagnosis might lead to better management and patient outcomes. The study reports that a fluorescent probe tracked the development of osteoarthritis in male mice, brightening as the disease progressed.
In this case, the “probe” was a harmless fluorescent molecule that detected the activity leading to cartilage loss in the joint, the key characteristic of osteoarthritis. This lab and mouse study is the first to demonstrate that near-infrared fluorescence – a specific type of light invisible to the human eye but possible to see with optical imaging – can be used to detect osteoarthritis changes over time. The new approach might also help analyze the effectiveness of osteoarthritis drugs, leading to improved treatments.
The release quotes co-first author Averi A. Leahy, B.A., an M.D./Ph.D. student in the medical scientist training program at TUSM and the Sackler School, as saying, “Patients are frequently in pain by the time osteoarthritis is diagnosed. The imaging tests most frequently used, X-rays, don’t indicate the level of pain or allow us to directly see the amount of cartilage loss, which is a challenge for physicians and patients.”
Co-first author Shadi A. Esfahani, M.D., M.P.H., post-doctoral fellow in the division of nuclear medicine and molecular imaging at Massachusetts General Hospital, and in the department of radiology at Harvard Medical School, added, “The fluorescent probe made it easy to see the activities that lead to cartilage breakdown in the initial and moderate stages of osteoarthritis, which is needed for early detection and adequate monitoring of the disease. To measure the probe’s signal, we used an optical imaging system, to non-invasively look inside the knee.”
The right knees of 54 mice were affected by injury-induced osteoarthritis and served as the experimental group (the mice received pain medication). The healthy, left knees of the mice served as the control group.
Over a two-month period, the researchers took images of each knee every two weeks to determine if the fluorescent probe emitted a signal. Strikingly, the signal became brighter in the injured right knee, at every examined time point, through the early to moderate stages of osteoarthritis. The probe emitted a lower signal in the healthy left knee, and did not increase significantly over time.