Increased DNA fragmentation and ultrastructural changes in fibromyalgic muscle fibres

Abstract

Objective: To determine whether there is evidence of increased DNA fragmentation and ultrastructural changes in muscle tissue of patients with fibromyalgia (FM) compared with healthy controls.

Methods: Muscle tissues from 10 community residents with FM and 10 age and sex matched healthy controls were examined "blindly" for the presence of DNA fragmentation by two different methods: terminal deoxynucleotidyl transferase (TdT) staining (TUNEL) and the FragEL-Klenow DNA fragmentation detection kit. Ultrastructural analysis of tissue was performed by electron microscopy.

Results: DNA fragmentation was detected by both methods in 55.4 (SEM 2.5)% of the nuclei in muscle tissue of patients with FM compared with 16.1 (4.1)% (p<0.001) of the nuclei in healthy controls. Contrary to expectation, no typical features of apoptosis could be detected by electron microscopy. The myofibres and actin filaments were disorganised and lipofuscin bodies were seen; glycogen and lipid accumulation were also found. The number of mitochondria was significantly lower in patients with FM than in controls and seemed to be morphologically altered.

Conclusion: The ultrastructural changes described suggest that patients with FM are characterised by abnormalities in muscle tissue that include increased DNA fragmentation and changes in the number and size of mitochondria. These cellular changes are not signs of apoptosis. Persistent focal contractions in muscle may contribute to ultrastructural tissue abnormalities as well as to the induction and/or chronicity of nociceptive transmission from muscle to the central nervous system.

Figures

Figure 1

DNA fragmentation staining (dark dots, black arrow) with the Klenow method in muscle tissue of subjects with FM (B) compared with healthy controls (A). Blue staining (white arrow) shows nuclei without DNA fragmentation (original magnification x200).

Figure 2

Electron micrograph of muscle tissue from a healthy control (A) and from a subject with FM (B) showing zig-zagging of the Z bands. L shows a lipid droplet. M and the white arrow shows a mitochondrion (A). There are no mitochondria in the selected anatomical region of the subject with FM (B). (Original magnification x8400.)

Figure 3

Electron micrograph of muscle tissue from a healthy control (A) for comparison and from subjects with FM (B-D) with different duration of symptoms: (B) 1 year; (C) 8 years; (D) 20 years. Black arrows indicate mitochondria (A, D). The open arrow indicates glycogen accumulation as a sign of disturbed glycogen use in FM (C). Uniformity of size and shape of the mitochondria in the healthy control is shown in (A). In (B) loss of mitochondria is shown in the presented section (see also fig 2B). (C) shows a huge accumulation of glycogen. In (D) enlargement and different shape of mitochondria (arrow) are presented. (Original magnification 2.2x14 000.)