Collagen fibers in small airways (Picrosirius-polarization method). C: control groups. E: emphysema groups. Mice were treated with saline (SAL) or bone marrow (BM), adipose (AD), and lung (L)-derived mesenchymal stromal cells (MSC). IV: intravenous route. IT: intratracheal route. Values are mean × SD of 7–30 mice in each group. All values were computed in ten random, non-coincident fields per animal. *Vs. C group (p < 0.05). #Vs. E-SAL group (p < 0.05).