To Örebro University

AIM: The aim of the study was to assess the cellular and structural properties of skeletal muscle in restless legs syndrome (RLS).

METHOD: Twenty patients and 16 controls were included. Aerobic performance was assessed using a submaximal test. On muscle biopsies taken from the tibialis anterior, fiber distribution and fiber area were analyzed together with parameters surveying the microvascularization, especially the tortuosity, which is expressed as a percent of muscle fiber perimeter in contact with the wall of the microvessel, length of capillary/perimeter of fiber (LC/PF) index.

RESULTS: The RLS group had significantly lower predicted maximal oxygen uptake (p = 0.01) and significantly higher LC/PF index (p = 0.01) compared to the controls.

CONCLUSION: The higher capillary tortuosity in RLS patients indicates the occurrence of significant remodeling in capillary geometry in RLS.

Background: Despite the fact that patients with obstructive sleep apnoea syndrome (OSAS) often have symptoms at the level of skeletal muscle such as fatigue, the question of whether the structural, cellular and functional properties of limb skeletal muscles are affected has not been fully examined. Objective: The aim was to examine physiological and muscular parameters in patients with OSAS and to assess the relationship between these parameters and the clinical symptoms. Method: Eighteen patients with OSAS and 16 controls participated. Aerobic capacity was assessed using a submaximal test. Fibre type distribution and fibre area were analyzed on muscle biopsies taken from the tibialis anterior. The microvascularization was assessed using the following parameters: (1) the number of capillaries per fibre (CAF), (2) CAF per fibre area (CAFA), (3) capillary to fibre perimeter exchange (CFPE) index, which represents the interface between muscle fibre and capillaries, and (4) length of capillary/perimeter of the fibre (LC/PF) index or capillary tortuosity, which represents the percent of muscle fibre perimeter in contact with the wall of the microvessel. Results: The OSAS group had significantly lower predicted relative maximal oxygen uptake (p = 0.0047) which was inversely correlated to the apnoea/hypopnoea index (AHI; r = –0.6, p = 0.017). There was a significantly higher CFPE index for slow type I fibres (p = 0.007) and fast type II fibres (p = 0.0126) and a significantly higher LC/PF index for type I fibres (p = 0.0003) and type II fibres (p = 0.0285) in OSAS patients compared to controls. Conclusion: OSAS patients have a higher muscle microvascularization and a lower aerobic capacity than controls. Furthermore the aerobic capacity was inversely correlated to AHI.

An increased capillary network has been observed in the skeletal muscle in patients with Restless Legs Syndrome (RLS) and Obstructive sleep apnea syndrome (OSAS). These changes 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), OSAS (n=12) 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 compared to controls. The percentage of proliferating capillaries (CD31,Ki-67⁺)  was significantly higher in OSAS compared with controls.

In conclusion 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.