Polymyalgia rheumatica (PMR) is an inflammatory disease that typically affects elderly people. Its clinical hallmark is the severity of pain in the shoulder and pelvic girdle. Mild to moderate synovitis and/or bursitis of the joints involved has been described. Neuropeptides are involved in nociception and modulation of inflammatory reaction. To evaluate whether neuropeptides have a role in PMR pathophysiology, we studied the expression of substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP) and somatostatin (SOM) in shoulder synovial tissues of PMR patients.
Synovial expression of neuropeptides was investigated by immunohistochemical analysis, in two groups of PMR patients: the first one at the onset of disease and the second one after corticosteroid treatment, and in other joint diseases, rheumatoid arthritis (RA) and osteoarthritis (OA).
The only significant expression of VIP was found in PMR and, to a lesser extent, in RA synovial tissue. In PMR, we observed VIP immunostaining both in the lining layer and in the sublining area. In patients on corticosteroid treatment VIP lining layer expression was not significantly different while VIP positive cells in the sublining area were almost absent.
Local VIP production in PMR synovial tissue might contribute to the typical musculoskeletal discomfort and it may have a role in the immunomodulation of synovial inflammation.