Figure 3

The increase of MSC homing is associated with collagen fiber deposition. A) normal control group; B) COPD group; C) COPD + ⁶⁰CO γ irradiation + MSCs transplantation group; D) COPD + rAAV-SPA-TK injection + ⁶⁰CO γ irradiation + MSC transplantation group; E) COPD + AAV injection + ⁶⁰CO γ irradiation + MSC transplantation group. (I) Morphological appearance of lung sections stained with Masson’s trichrome (×100) showed hardly any collagen deposition in the normal control group (A). Compared with COPD (B), COPD + ⁶⁰CO γ irradiation + MSCs transplantation (C), and COPD + AAV injection + ⁶⁰CO γ irradiation + MSC transplantation (E) groups, there was an obvious increase in collagen deposition around vessels and bronchia in the COPD + rAAV-SPA-TK injection + ⁶⁰CO γ irradiation + MSC transplantation group (D). Furthermore, blue collagen fibers were found in lung interstitial spaces. (III) The result was expressed as Wac/Pbm (μm²/μm) (collagen area on the basal membrane of airway/the perimeter of the basement membrane of bronchioles.(II, IV) Detection of Y chromosome-specific signals by fluorescent in situ hybridization (FISH) (×200). The nuclei were stained yellow in cells with a Y chromosome (indicated by arrows). These cells were found in groups C, D and E, but more cells were present in group D. The percentage of Y- chromosome positive cells was calculated by the ratio of Y- chromosome positive cells to the total cell number in 5-10 fields at 400× magnification from each section. Increased numbers of MSCs after rAAV-SPA-TK injection suggested that stem cell niches increased the homing of MSCs to the lung. Scale bars = 100 μm. *P < 0.01 compared with the other four groups.