Fibromyalgia (FM) is a common, chronic musculoskeletal pain disorder of unknown etiology seen predominantly in women. As reported previously, highly ordered collagen cuffs were observed around preterminal nerve fibers in the skin of FM patients for unknown reasons. Therefore, the question was raised whether abnormal collagen metabolism is correlated with neurogenic inflammation, a potential activator of collagen metabolism, in FM patients. The presence of inflammatory cytokines, IL-1b, IL-6 and TNF-a was investigated by using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC).
53 skin biopsies from FM patients (women, 30-65 years of age) were examined and compared to skin biopsies of 10 age- and gender-matched healthy controls. Biopsies were obtained from the deltoid region. One rheumatoid arthritis synovial tissue was used as a positive control for the expression of cytokines. Total RNA isolated from the tissue samples were reverse transcribed (RT) by random hexamers as the primer for RT followed by PCR amplification (40 cycles) using specific primers for IL-1b, IL-6 and TNF-a.
G3PDH was used as an internal control for loading differences. Negative controls included no template control and RNA control to check for genomic contamination. Expression of IL-1b and TNF-a protein was investigated in the skin by IHC using specific antibodies (avidin-biotin method). Rabbit polyclonal anti-human TNF-a antibodies and monoclonal anti-human IL-1b antibodies were employed as primary antibodies. Equal concentrations of purified rabbit and mouse IgG were used as negative control.
Positive signals (RT-PCR) were detected in 19/50 FM patients (38%) for IL-1b, in 14/51 FM patients (27%) for IL-6, and in 17/53 patients (32%) for TNF-a. None of the cytokines could be detected in healthy control skin. Immunoreactivity for IL-1b and TNF-a could be demonstrated in some skin tissues of FM patients. However, the number of positive cells and the intensity of staining was low.
In conclusion, the detection of cytokines in FM skin suggest the presence of inflammatory foci in the skin of these patients and may explain the response to NSAID therapy in a certain subset of FM patients.
Disclosure: Dr. Salemi was supported by the Zurzach foundation and Dr. Sprott by the American Fibromyalgia Syndrome Association (AFSA) and the Albert Böni foundation, all others by their institutions.