Drivers of epithelial-mesenchymal transition in chronic obstructive pulmonary disease

COPD is a chronic disease with a complex condition that involves a frequent mix of airway and lung parenchymal damage. The Global Initiative for Chronic Obstructive Lung Disease (GOLD 2014) has characterised it by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airways and the lung to noxious particles or gases. The definition of COPD has been a bit confusing and controversial due to its difficult diagnostic procedures over the years until recently. It was stereotyped as being caused by inflammation and considered analogous to asthma (1). The current definition of COPD does not include the terms chronic bronchitis and emphysema. Chronic bronchitis is the inflammation involving cough and sputum production that is not always necessarily associated with airflow limitation. Emphysema, defined as destruction of the alveoli, a pathological feature of several structural abnormalities in COPD that can also be found in people with normal lung functions (GOLD 2014). However, it is reflected by a decline in gas-exchange rate of the alveoli of the lungs by a measurement of the O₂ (oxygen) or CO (carbon monoxide) transfer rate (diffusion capacity) and can cause worsening of airflow limitation in COPD