Expression of lumican in human lungs

The collagen-elastin-proteoglycan (PG) matrix is the key constituent of lung parenchyma and plays a major role in the mechanical behavior of lung tissues. However, the exact composition of the PG matrix in lungs has not yet been fully determined. In the present study we report the expression of leucine-rich repeat PGs in adult human lungs. PG extraction was performed on peripheral lung tissue from patients undergoing therapeutic lung resections. The samples were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting using antipeptide antisera specific to human lumican, decorin, biglycan, and fibromodulin. Control experiments to verify antiserum reactivity were performed with an extract of adult human articular cartilage, which is known to contain all four PGs. In all lung extracts analyzed, a single component of molecular weight 65 to 90 kD was detected for lumican. Decorin, biglycan, and fibromodulin were either not detected or were barely detectable in the lung extracts, but were readily visualized in the cartilage samples. Immunohistochemistry showed that lumican was diffusely present in peripheral lung tissue, mainly in vessel walls. These results suggest that lumican is a major component of the PG matrix in adult human lungs.