HMGB1 induces matrix vesicles secretion from RAW264.7 macrophages (A-F) or mouse peritoneal macrophages (G-I).

<p>Transmission electron microscopic images show MVs with no crystalline hydroxyapatite <b>(A)</b>, with early mineralized electron dense materials (short arrow) near the inner leaflet <b>(B)</b> and with matured crystal-like structures (long arrow) in the vesicle interior <b>(C)</b>. <b>(D)</b> Size distribution of MVs was determined by dynamic light scattering method. <b>(E)</b> Assay of TNAP activity in cells (filled bar) or MVs (white bar). *<i>P</i> <0.05 (n = 3). <b>(F)</b> MVs secretion from cells was determined by flow cytometry. **<i>P</i> <0.01 (n = 5). <b>(G)</b> Effect of HMGB1 on secretion of MVs from mouse peritoneal macrophages was determined by flow cytometry. **<i>P</i> <0.01 (n = 4). <b>(H)</b> TNAP activity in MVs was determined. *<i>P</i><0.05 (n = 4). <b>(I)</b> HMGB1-MVs from mouse peritoneal macrophages initiated mineralization in type I collagen-coated dishes as determined by Alizarin Red staining and von Kossa staining. For all grouped data, values are presented as the mean±SEM.