MMP2 and obstructive sleep apnea syndrome: Based on the pathologic significance of MMPs in OSA and the potential biological effects of MMP-2 (-1306C/T) and MMP-9 (-1562C/T) polymorphisms on their protein expression, we hypothesized that functional polymorphisms in the promoter region of MMP-2 and MMP-9 would be associated with differential risk of OSA.