The expression of vascular endothelial growth factor in skeletal muscle of patients with sleep disorders

An increased capillary network has been observed in skeletal muscle of patients with restless legs syndrome (RLS) and obstructive sleep apnea syndrome (OSAS). This finding could be due to upregulation of growth factors responsible for angiogenesis. The aim of the study was to examine the occurrence and localization of VEGF and capillary proliferation in skeletal muscle of RLS (n = 12) and OSAS (n = 12) patients and controls (n = 11). Double-immunofluorescence staining for capillaries (CD31) and VEGF, and proliferating cells (Ki-67), was carried out on biopsies taken from the tibialis anterior. The percentage of capillaries expressing VEGF (CD31,VEGF(+)) was significantly higher in OSAS and RLS patients compared with controls. The percentage of proliferating capillaries (CD31,Ki-67(+)) was significantly higher in OSAS patients compared with controls. Our study shows the occurrence of proliferation of endothelial cells in skeletal muscle in RLS and OSAS, supporting an upregulation of VEGF located in capillaries, probably due to local hypoxia.