Related Experiment Video
Updated: Jun 6, 2026

Monitoring Neutrophil Elastase and Cathepsin G Activity in Human Sputum Samples
Published on: May 21, 2021
Osteoprotegerin in sputum is a potential biomarker in COPD
Masako To1, Kazuhiro Ito1, Pilar M Ausin1
1Airway Disease Section, National Heart and Lung Institute, Imperial College, London, England.
Background:
COPD is characterized by chronic airflow limitation and inflammation of the respiratory tract. Several inflammatory biomarkers have been evaluated in COPD but are poorly related to disease severity and progression. Osteoprotegerin (OPG) is a glycoprotein mediator that is expressed in the lung and macrophages, so we have studied its concentration in induced sputum and macrophages of patients with COPD.
Methods:
OPG was measured by enzyme-linked immunosorbent assay in induced sputum of patients with COPD and control subjects.
Results:
OPG concentrations in induced sputum of patients with COPD (18.7 ± 18.6 ng/mL, n = 39) were significantly higher than those of healthy smokers (8.1 ± 5.6 ng/mL, n = 15), healthy nonsmokers (3.5 ± 3.8 ng/mL, n = 14), or patients with asthma (8.0 ± 5.4 ng/mL, n = 18). Sputum OPG levels in COPD negatively correlated with FEV(1) and positively correlated with residual volume to total lung capacity ratio (RV/TLC) (r = 0.55, P < .05), transfer factor of the lung for carbon monoxide (r = -0.53, P < .05), and carbon monoxide transfer coefficient (r = -0.61, P < .01). By contrast, sputum IL-8 concentrations were related to disease severity but not to RV/TLC or gas diffusion. Airway macrophages and neutrophils were positive for OPG by immunocytochemistry in sputum and peripheral lung tissue. OPG induced matrix metalloproteinase-9 release from sputum macrophages in vitro.
Conclusions:
Sputum OPG may be a useful biomarker to monitor parenchymal destruction in COPD.
Related Concept Videos
Chronic Obstructive Pulmonary Disease-IV: Assessement and Diagnostic Studies
Medical History
Chronic Obstructive Pulmonary Disease
Smoking is a primary risk factor for COPD, with over 80% of patients having a history of it. Patients typically experience progressive dyspnea or labored breathing, frequent coughing, and recurrent pulmonary infections. Many eventually succumb to respiratory failure, characterized by...
COPD: Management Using Bronchodilators and Corticosteroids
Chronic Obstructive Pulmonary Disease III: Chronic Bronchitis Features
Chronic Obstructive Pulmonary Disease-II: Pathophysiology
Chronic Inflammation
COPD: Pathogenesis and Clinical Features
The primary cause for the onset of COPD is cigarette smoking and exposure to air pollution. These hazardous factors initiate a chain reaction within the lungs, resulting in chronic inflammation, damage to the airways, and a...
