Accumulation of c-kit<sup>+</sup> cells in the SU5416/chronic hypoxia (SuHx) model.

<p>(<b>A</b>) Representative images of <i>in situ</i> hybridization images demonstrating <i>Kit</i> mRNA expression. In naïve control animals, occasional low <i>Kit</i> expression was found in cells of vessels and alveolar walls<b>,</b> whereas multiple cells in lumen-obliterating regions and vessel wall/perivascular region expressed <i>Kit</i> (granular staining pattern) in the lung of a SuHx animal. The open arrows indicate cells with strong <i>Kit</i> expression. Counterstaining with Gill’s Hematoxylin. Magnification: 400×. Scale bar: 20 µm. (<b>B</b>) Quantification of the number of c-kit<sup>+</sup> cells/vessel over time. n = 3 animals per group. * <i>P</i><0.05, ** <i>P</i><0.01. (<b>C</b>) Images demonstrate representative optical sections (confocal microscopy). c-kit<sup>+</sup>, c-kit<sup>+</sup> von Willebrand Factor<sup>+</sup> (vWF<sup>+</sup>) and c-kit<sup>+</sup> α-smooth muscle actin<sup>+</sup> (α-SMA<sup>+</sup>) cells were occasionally found in alveolar walls and vessel walls of naïve control animals. c-kit<sup>+</sup> and c-kit<sup>+</sup> α-SMA<sup>+</sup> cells accumulated in and around the pulmonary arteries of SuHx animals over time. The number of c-kit<sup>+</sup> vWF<sup>+</sup> cells also increased until day 21 in and around the pulmonary arteries of SuHx animals and started to decline thereafter. Arrows indicate c-kit<sup>+</sup> vWF<sup>+</sup> or c-kit<sup>+</sup> α-SMA<sup>+</sup> cells. Nuclear counterstaining with 4',6-diamidino-2-phenylindole (DAPI). Magnification: 630×. Scale bar: 20 µm. (<b>D-E</b>) Quantification of the number of c-kit<sup>+</sup> vWF<sup>+</sup> (D) and c-kit<sup>+</sup> α-SMA<sup>+</sup> (E) cells per vessel. n = 3 animals per group. * <i>P</i><0.05, ** <i>P</i><0.01 and *** <i>P</i><0.0001.</p>