Effects of continuous positive airway pressure on exhaled transforming growth factor-β and vascular endothelial growth factor in patients with obstructive sleep apnea

BACKGROUND: Both transforming growth factor β (TGF-β) and vascular endothelial growth factor (VEGF) are master regulators of airway remodeling; however, their pathological roles in obstructive sleep apnea (OSA) remain unclear. The aim of the present study was to evaluate the expression of TGF-β and VEGF protein in the serum and exhaled breath condensate (EBC) before and after continuous positive airway pressure (CPAP) treatment in OSA patients. METHODS: Forty patients with moderate to severe OSA requiring CPAP and 20 healthy subjects were prospectively recruited. The concentrations of TGF-β and VEGF protein in the serum and EBC were evaluated by enzyme-linked immunosorbent assay. All OSA patients underwent a sleep study that was repeated 3 months after receiving CPAP therapy. RESULTS: Protein concentrations of TGF-β and VEGF in the serum did not differ between healthy controls and OSA patients before CPAP treatment. There was also no difference in the serum protein concentrations of TGF-β and VEGF of the OSA patients before and after CPAP treatment. However, both the TGF-β and VEGF protein concentrations in the EBC were higher in the OSA patients than those in control subjects, and recovered to normal levels after CPAP. CONCLUSIONS: Successful treatment of OSA by CPAP can restore the TGF-β and VEGF protein concentrations in the EBC.