2218
To clarify this , we investigated bone phenotypes of apoE knock - in ( k . i . ) mice , which express one human isoform each ( apoE2 k . i . , apoE3 k . i . , apoE4 k . i . ) in place of the mouse apoE .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None