18360
The transgene is expressed in osteoblasts , periosteum , and cortical bones , and plasma levels of TNAP in mice expressing Col1a1 - Tnap are 10 - 20 times higher than those of wild - type mice .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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