MSP, also known as hepatocyte growth factor–like protein, is the only protein identified as a specific ligand for tyrosine kinase receptor (RON), a protein expressed by microglia in brain.31 In addition to stimulating macrophages, MSP can also act with other cell types including epithelial and haematopoietic cells.32 After intracerebral haemorrhage (ICH), MSP and RON are found to be expressed less in neurons and predominantly in astrocytes, which is a kind of macrophage and closely related to the neural degeneration, regeneration and cerebral ischaemic injury.33,34. The gene discussed is NTRK1; the disease is intracerebral hemorrhage.