Physiological shear stress induces proPLT production in primary mouse MKs. (A) Primary mouse MKs range between 20 and 85 µm in diameter on culture day 4, and become larger (40-100 µm) if they do not form proPLTs. (B) MKs in static culture begin producing proPLTs at 6 hours postpurification and reach maximal proPLT production at 18 hours. (C) Primary mouse MKs under physiological shear stress (∼600 mPa) begin producing proPLTs immediately upon trapping and extend/release proPLTs within the first 2 hours of culture. (D) Percent proPLT-producing primary mouse MKs under physiological shear stress are increased significantly to ∼90% over static cultures (∼50%).²⁶  (E) ProPLT extension rates under physiological shear stress are increased significantly (to ∼30 µm/min) over static cultures (0.85 µm/min).⁴¹  Scale bars represent 50 µm (A-C).