Am. J. Respir. Crit. Care Med., Vol 151, No. 6, Jun 1995, 1956-1964.
Increased expression of type VI collagen in lung fibrosis
U Specks, A Nerlich, TV Colby, I Wiest and R Timpl
Max-Planck-Institut fur Biochemie, Martinsried, Germany.
Pulmonary fibrosis is characterized by disturbances of extracellular matrix
protein deposition resulting from fibroblast activation and proliferation.
Collagen VI, forming microfibrillar meshworks separate from major fibrillar
systems, is thought to serve as an anchoring element between collagen I/III
fibrils and basement membranes and as a cell binding substrate. We report
on the expression of collagen VI in normal and in fibrotic lungs. Collagen
VI is present in vascular and bronchial walls and in the interstitial space
of normal lungs. Its turnover is too low to generate a mRNA signal by in
situ hybridization. Collagen VI expression is increased in lung fibrosis,
and its degree appears independent of the etiology of fibrosis. There was
no evidence for differential regulation of gene expression for the alpha
1(VI) and alpha 3(VI) constitutive peptide chains of collagen VI. Collagen
VI mRNA is expressed by fibroblasts, mostly with myofibroblast
characteristics. Collagen VI was coexpressed with collagen III rather than
collagen I in idiopathic bronchiolitis obliterans with organizing
pneumonia, acute interstitial pneumonitis of the Hamman-Rich type, and
bleomycin-induced fibrosis, but collagen VI overlapped with collagen types
I and III in idiopathic pulmonary fibrosis. These coexpression data suggest
that collagen VI expression may be an early rather than a late phenomenon
in pulmonary fibrosis.
