A novel subset of putative stem/progenitor CD34(+)Oct-4(+) cells is the major target for SARS coronavirus in human lung

Chen, Yongxiong; Chan, Vera Sau-Fong; Zheng, Bojian; Chan, Kelvin Yuen-Kwong; Xu, Xiaoning; To, Leo Yuk-Fai; Huang, Fang-Ping; Khoo, Ui-Soon; Lin, Chen-Lung Steve

To determine if ACE2 ϩ CD34 ϩ Oct4 ϩ cells could be found in non-SARS lung, lung tissues from 14 lung cancer patients who had no SARS infection ( Table II ) were examined. Eight of these patients were retrieved from our archive. The other six were additionally enrolled to obtain fresh lung tissues, part of which was immediately fi xed, embedded, and sectioned for IHC-FISH-ISH study upon collection, and the other part was used for ex vivo infection experiments (described below). Results showed that ACE2 signals were detectable in samples from 8 of 14 lung cancer patients, but not in the others ( Table II ) . In these eight patients, we found that consistent with our fi ndings in the SARS lung, ACE2 ( Fig. 3 A , b , f, and n, green) was not expressed by surfactant A ϩ cells ( Fig. 3 A , a, e, i, and m, brown; each row represents results from a patient) but was expressed by CD34 ϩ cells ( Fig. 3 A , c and j, purple or green). For better diff erentiation between alveolar and vascular lumens, an endothelial cell marker, CD31, was used to depict blood vessels ( Fig. 3 A , a -c, red) . We showed that cytokeratin ϩ cells ( Fig. 3 A , e, f, m, and n, red) did not express ACE2 either ( Fig. 3 A , f and n, green) . Furthermore, CD34 expression ( Fig. 3 A , j, green) was colocalized with Oct-4 ( Fig. 3 A , k, purple) . Interestingly, these ACE2 ϩ CD34 ϩ Oct4 ϩ cells did not express CD15 (i.e., SSEA-1), another marker for stem/progenitor cells ( Fig. 3 A , i, j, and k, red) . We also found that in line with our previous report ( 13 ), ACE2 ϩ cells ( Fig. 3 A , n, green) also expressed L-SIGN ( Fig. 3 A , p, purple) , a binding receptor for SARS-CoV. In the lung samples from these eight patients, the number of CD34 ϩ cells was identifi ed from 2 to 72 per microscopic fi eld (400ϫ) ( Table II ) . Therefore, ACE2 ϩ CD34 ϩ Oct4 ϩ L-SIGN ϩ cells are also present in the lung of some non-SARS individuals. Together with our previous fi ndings (reference 13 and Fig. S1 ), we also conclude that the binding receptor L-SIGN is expressed by at least two cell types in the non-SARS lung: cytokeratin ϩ ACE2 − bronchial/bronchiolar epithelial cells and CD34 ϩ Oct4 ϩ cells that , followed by FISH for ACE2 (green labeling in b, some indicated by green arrows) and ISH for CD34 (purple labeling in c, some indicated by light blue arrows). DAPI counterstaining is in d. Circle in b indicates autofl uorescence from red blood cells. (e -h) IHC for surfactant A (brown labeling, one indicated by a yellow arrow in e; also visible in g) and for cytokeratin (red labeling, one indicated by a white arrow in e; also visible in f and g), followed by FISH for ACE2 (green labeling in f, some indicated by green arrows) and ISH for CD34 (purple labeling in g, some indicated by light blue arrows). DAPI counterstaining is in h. (i -L) IHC for surfactant A (brown labeling in i, one indicated by a yellow arrow; also visible in k) and for CD15 (red labeling, one indicated by a dark green arrow in i; also visible in j and k), followed by FISH for CD34 (green labeling in j, some indicated by light blue arrows) and ISH for Oct-4 (purple labeling in k, some indicated by purple arrows). DAPI counterstaining is in L. One of the CD34 ϩ Oct-4 ϩ cells is juxtaposed to a surfactant ϩ cell (the yellow arrow in i vs. the lower light blue arrow in j and the lower purple arrow in k). (m -q) IHC for surfactant A (brown labeling, one indicated by a yellow arrow in m; also visible in p) and for cytokeratin (r