Scaffold size as a function of time in culture for the cell-free scaffolds. The scaffolds containing higher concentration of platelets (PFC and R-PFC groups; p < 0.0001) had significantly greater contraction than those with lower concentrations of platelets (COL and CF groups). The addition of erythrocytes did not have a significant effect on scaffold contraction (PFC vs. R-PFC, p > 0.8). COL, collagen; CF, Collagen–fibrin; PFC, platelet–fibrin–collagen; R-PFC, RBC–platelet–fibrin–collagen.