Immunohistochemical staining of human and murine megakaryocytes for MMPs.

Cytospin preparations of ex vivo–expanded human and murine MKs were stained with MMP-2 and -9 mouse mAbs and goat-antimouse-FITC antibody, along with DAPI counterstain, and they were observed by fluorescence microscopy at a magnification of 400 × (A,B,D,E) and 1000 × (C,F). (A) An irrelevant IgG control showed little nonspecific staining. There was also low staining for MMP-2 (D). Staining of polyploid human (B,C) and murine (E,F) MKs revealed the presence of MMP-9 on the cell surface. Results are representative of 3 separate experiments.