FIGURE 8.

Influenza A-induced collagen deposition requires Smad3 in vivo. A, SV129/BL6 mice (dashed black line) or Smad3^−/− mice infected with A/FM/1/47-MA (solid black line) did not show any change in their body weight 5 days following infection compared with sham-infected mice (dotted black line). B, 5-μm-thick tissue sections from sham-infected (panel i), A/FM/1/47-MA-infected (panel ii) wild-type mice, or A/FM/1/47-MA-infected (panel iii) Smad3^−/− mice treated were stained with an anti-influenza A antibody. Sections were visualized under a light microscope, and positive staining was identified in influenza-infected but not sham-infected mice. C, hydroxyproline levels were assessed in lungs 5 days following A/FM/1/47-MA infection in C57BL/6 SV129BL6 mice and compared with PBS control mice. Animals were grouped as follows: C57BL/6 + PBS (filled circle; n = 8); C57BL/6 SV129/BL6+ A/FM/1/47-MA (filled square; n = 11); Smad3^−/− mice + A/FM/1/47-MA (filled triangle; n = 8). Smad3^−/− had significantly lower collagen levels compared with WT C57BL/6 mice infected with A/FM/1/47-MA. Data are expressed as individual sample values with continuous line representing the mean value per group and error bars representing S.E. **, p < 0.01; ***, p < 0.001. D, homogenates of lungs from mice euthanized on day 5 were used to determine the viral titer via TCID₅₀ assay. Data are expressed as individual sample values with continuous line representing the mean value per group and error bars representing S.E. E, 5-μm-thick tissue sections from sham-infected mice (panels i–iv), wild-type A/FM/1/47-MA-infected mice (panels v–viii), or A/FM/1/47-MA-infected Smad3^−/− mice (panels ix–xii) were immunostained with anti-collagen I (panels i, v, and ix), anti-collagen III (panels ii, vi, and x), anti-collagen IV (panels iii, vii, and xi), and anti-collagen VI antibodies (panels iv, viii, and xii). Sections were visualized under a light microscope, and positive staining was identified in regions of lung with evidence of influenza infection and inflammation in wild-type mice, but this was reduced in Smad3^−/− mice.