Plasma Osteopontin Levels: A New Marker for MS?

Elevated plasma osteopontin levels could prove to be a valuable biomarker not only for multiple sclerosis but also for neuromyelitis optica (NMO), according to findings from a new study published in the Journal of Neuroimmunology (Shimizu et al., 2013).

The authors, led by Yuko Shimizu, Ph.D., of Tokyo Women's Medical University, noted that previous studies of patients with MS have shown that osteopontin  (OPN) levels were higher during relapses than during remissions. However, no studies to date have gauged OPN levels in patients with NMO, and it is not known whether osteopontin levels could be a useful tool in identifying disease activity in patients with NMO. 

"In the present study, we measured plasma OPN levels in Japanese MS and NMO patients to investigate its utility as a biomarker of disease activity and therapeutic response," the authors wrote.

They enrolled three groups into the study: 20 healthy individuals, 16 patients with NMO, and 17 patients with MS.

The patients with NMO had been receiving treatment with either prednisolone alone or in combination with azathioprine. 

Of the patients with multiple sclerosis, six had secondary progressive MS and 11 had relapsing-remitting MS. Patients with relapsing-remitting MS were either in relapse, or they had been in remission for at least 2 years following interferon beta therapy.   

The investigators found that compared with MS patients in remission, MS patients in relapse had significantly higher OPN levels (69.24 ± 36.85 ng/ml versus 61.64 ± 16.31 ng/ml). In addition, they found that OPN levels were significantly lower after treatment with interferon beta (59.02 ± 15.71 ng/ml). 

Similar results were seen in patients with NMO. Patients in relapse had significantly higher OPN levels, compared with those whose disease was stable (76.86 ± 30.18 ng/ml versus 52.72 ± 23.16 ng/ml). 

The researchers also found that OPN levels were significantly higher in MS and NMO patients at all stages of disease, compared with healthy individuals (mean, 33.76 ± 26.56 ng/ml). 

"These are the first results to suggest that plasma OPN levels in NMO patients may provide a useful marker, and that OPN may play an important role in inflammation, disease activity, and disease progression, as well as MS," the researchers concluded.

Key open questions

• Do elevated plasma osteopontin levels play a role in the pathogenesis of MS and NMO, or are they the result of disease activity?
• Is it possible to quantify precisely what levels of plasma osteopontin would be associated with a firm diagnosis of MS or NMO? 

Disclosures   

Dr. Shimizu received honoraria for speaking for Bayer Health Care and Biogen Idec Japan. Another author, Shinichiro Uchiyama, M.D., of the Tokyo Women's Medical University in Tokyo, Japan, has received payment for development of educational presentations from Bayer Health Care. The remainder of the authors have reported no conflicts of interest.