23577
Growing evidence demonstrates that extracellular matrices ( ECMs ) regulate many aspects of megakaryocyte ( MK ) development ; however , among the different ECM receptors , integrin alpha2beta1 and GPVI are the only collagen receptors studied in platelets and MKs .
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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:
 None