Bioreactor-derived mPLTs manifest structural and functional properties of mouse blood PLTs. (A) Biomarker expression, and forward/side scatter and relative concentration of GPIX⁺ primary mouse MKs infused into bioreactor after isolation on culture day 4, and (B) effluent collected from bioreactor 2 hours postinfusion. (C) Application of shear stress shifts GPIX⁺ product toward more PLT-sized cells relative to static culture supernatant. (D) Comparison of primary mouse MK culture product under static and bioreactor conditions over a period of 2 hours. (E) Application of shear stress shifts product toward more PLT-sized β1-tubulin⁺ Hoechst^- cells (labeled Platelet) relative to static culture supernatant. Insert shows quantitation of free nuclei in effluent. (F) Bioreactor-mPLTs are ultrastructurally similar to mouse blood PLTs and contain a cortical MT coil, open canalicular system, dense tubular system, mitochondria, and characteristic secretory granules. Bottom inserts show magnification of yellow boxes at PLT ends. (G) Bioreactor-mPLTs and PLT intermediates are morphologically similar to mouse blood PLTs (supplemental Figure 6) and display comparable MT and actin expression. Top 8 panels show Hoechst labeling, middle 8 panels show β1-Tubulin labeling bottom 8 panels show Phalloidis labeling. (H) Bioreactor-mPLTs form filpodia/lamellipodia on activation and spread on glass surface. Scale bars represent 5 µm (D,G-H) and 1 µm (F).