Acute lung injury involving extremely immature lungs often heals without excessive
fibrosis unlike later in gestation and in adults. Several factors may be involved, but fibroblast contraction of
collagen has been linked to the level of
wound fibrosis. To assess whether human lung fibroblasts of fetal versus adult origin differ in ability to contract
collagen and define the molecular underpinnings, we performed three-dimensional
collagen contraction assay, analyzed their differential
mRNA profile, specifically for
transforming growth factor-beta (
TGF-beta) signaling pathway and extracellular matrix components, studied the cell response to
TGF-beta in culture, and used two-dimensional gel electrophoresis followed by mass spectrometry to identify differences in their overall
proteomes. Human lung fetal fibroblasts contracted the
collagen matrix less than the adults. Smooth muscle actin expression did not differ.
TGF-beta stimulation resulted in greater Smad3 phosphorylation in fetal compared with adults.
mRNA and proteomic profiling reveal a number of
TGF-beta pathways, ECM components, and cytoskeletal regulatory molecules are differentially expressed between the cell types. Of note is
TGF-beta receptor interacting
protein 1 (TRIP-1), which we show inhibits fibroblast
collagen contraction and is higher in fetal than adult fibroblasts. We conclude that human lung fetal fibroblasts are less able to contract
collagen than adult lung fibroblasts. The diminished ability is not due to impediment of Smad3 activation but rather, at least in part, due to their higher level of TRIP-1 expression. TRIP-1 is a novel modulator of fibroblast
collagen contraction.