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Our results demonstrate that 3 % O ( 2 ) augmented proliferation of BMSC , as well as the formation of colonies in the colony - forming unit assay ( CFU - A ) , the percentage of quiescent cells , and the expression of stemness markers Rex - 1 and Oct - 4 , thereby suggesting an increase in the stemness of culture when exposed to hypoxia .
 Chemical: O ( 2 )
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: O ( 2 )