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

The origin of this novel putative human lung stem/progenitor cell is yet to be determined. In our study, some uninfected CD34 Ï© Oct4 Ï© cells were identifi ed in the alveoli and bronchiolar lining layer of the SARS lung ( Fig. 2 and Fig. S6) . Furthermore, not all the enrolled non-SARS individuals had these cells in the lung. It is thus likely that these CD34 Ï© Oct-4 Ï© cells might be blood-borne and recruited into the lung under regulation. This postulation can be supported at least in part by reports that circulation-or bone marrow -derived cells may diff erentiate into mature respiratory epithelia in animals ( 26 -28 ) , and that preexisting injury may increase recruitment of adult bone marrow -derived cells to the lung, which subsequently give rise to diff erentiated cells ( 29 ) . Because CD34 Ï© Oct4 Ï© cells can be found in the non-SARS lung ( Fig. 3 A ) and can be infected by SARS-CoV ex vivo ( Fig. 3 B and Figs. S8 and S9), we regard it unlikely that the presence of these cells in the lung is merely a response to SARS infection. For the same reason, it is also unlikely that these cells are recruited into the lung only as part of an attempt for viral clearance or are the only remaining cells bearing viral antigen by the time of death.