Vitamin D may slow the progressive decline in the ability to breathe that can occur in people with asthma as a result of human airway smooth muscle (HASM) proliferation, according to researchers at the University of Pennsylvania. The group found that calcitriol, a form of vitamin D synthesized within the body, reduced growth-factor-induced HASM proliferation in cells isolated from both persons with asthma and from persons without the disease. The proliferation is a part of process called airway remodeling, which occurs in many people with asthma, and leads to reduced lung function over time. The researchers believe that by slowing airway remodeling, they can prevent or forestall the irreversible decline in breathing that leaves many asthmatics even more vulnerable when they suffer an asthma attack. "Calcitriol has recently earned prominence for its anti-inflammatory effects," said Gautam Damera, Ph.D., who presented the research at the American Thoracic Society's 105th International Conference in San Diego on May 20, 2009. "But our study is the first to reveal the potent role of calcitriol in inhibiting ASM proliferation."
As part of the University of Pennsylvania's Airway Biology Initiative, the researchers are planning a randomized control trial of calcitriol vitamin D in patients with severe asthma and expect to have data from the trial in about a year's time. With its anti-inflammatory qualities and its ability to inhibit smooth muscle proliferation, Dr. Damera said, calcitriol may become an important new therapy, used alone or in combination with already prescribed steroids, for treating steroid-resistant asthma. Dr. Damera and his colleagues have also conducted experiments to determine the mechanism by which calcitriol retards HASM proliferation. They believe the vitamin D works by inhibiting activation of distinct set of proteins responsible for cell-cycle progression.