Vascular Endothelial Growth Factor is Highly Expressed in Muscle Tissue of Patients with Polymyositis and Patients with Dermatomyositis

Objective: To investigate the expression of vascular endothelial growth factor (VEGF) in muscle biopsy specimens and serum from patients with polymyositis and patients with dermatomyositis compared with that in healthy control subjects.

Methods: Muscle biopsy specimens from 33 patients with polymyositis or dermatomyositis and 15 healthy control subjects and serum samples from 56 patients and 56 healthy control subjects were analyzed. Patients were categorized into 3 groups, depending on disease duration and the presence or absence of inflammatory infiltrates. The expression of VEGF and the vessel marker CD31 in muscle was analyzed by immunohistochemistry, the expression of VEGF messenger RNA (mRNA) was analyzed by in situ hybridization, and serum levels of VEGF were determined by enzyme-linked immunosorbent assay.

Results: Patients with polymyositis or dermatomyositis in the early or chronic phase without inflammatory infiltrates had a decreased total number of capillaries compared with healthy individuals. In patients with early disease without inflammatory infiltrates, the number of VEGF-expressing muscle fibers was increased compared with that in control subjects, whereas VEGF expression was unchanged in the chronic phase of disease. In patients with established disease with inflammatory infiltrates, total VEGF expression was high compared with that in healthy control subjects. In healthy control subjects, VEGF was expressed in endothelial cells and in occasional muscle fibers. VEGF mRNA was expressed in muscle fibers in both healthy individuals and patients. The level of serum VEGF was significantly increased in patients compared with control subjects.

Conclusion: Our observations support a role of VEGF in the early phases of polymyositis and dermatomyositis. A reduced number of capillaries could lead to induction of VEGF expression in muscle fibers. Furthermore, differences in molecular expression during certain phases of disease may help in the development of specific therapeutic algorithms in the treatment of myositis.