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

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