Airway smooth muscle hyperproliferation is regulated by microRNA-221 in severe asthma.

Increased airway smooth muscle (ASM) mass is a feature of asthmatic airways, and could result from augmented proliferation. We determined whether proliferation and IL-6 release are abnormal in ASM cells (ASMCs) from patients with severe asthma, and whether these features could be mediated by microRNA-221 and microRNA-222, through modulation of the cyclin-dependent kinase inhibitors, p21(WAF1) and p27(kip1). ASMCs cultured from bronchial biopsies of healthy subjects and patients with nonsevere or severe asthma were studied.