8951
Nevertheless , despite relative enthusiasm arising from experimental data , application of stem cell therapy in the clinical setting has been severely hampered by several safety concerns arising from the major lack of knowledge on the fate of exogenously administrated stem cells within the COPD lung as well as the mechanisms regulating activation of resident progenitor cells .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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