The clot contraction assay showing iMK-driven shrinkage of macroscopic plasma clots and comparative iMK and platelet contractility. (A) Representative snapshots of an iMK-containing plasma clot before contraction at zero time point as well as at 15 and 60 minutes after the onset of contraction (see supplemental Video 1). (B) Averaged contraction kinetic curves for the iMK-containing clots (red) and PRP clots (green) equalized by the cell surface area (M ± SD, n = 5). The clot contraction driven by iMKs is segregated into phases 1 and 2 defined by the local extremum of the first derivative (blue line). (C) Averaged contraction kinetic curves for the iMK-containing clots (red) and PRP clots (green) equalized by the total cell volume (M ± SD; n = 5), which reveal superb biomechanical efficacy of platelets compared with iMKs. The cell counts in plasma (B-C) were adjusted such that iMKs and platelets before clot formation and contraction (100 μL initial plasma or clot volume) had about the same total cell surface area (∼250 mm2) (B) or volume (∼0.52 mm3) (C). Equalization by the total cell surface area and volume are described in “Clot contraction assay.” (D-E) Plots showing the final extents of contraction (D) in the iMK-containing plasma clots and PRP clots that were equalized by the cell counts, and comparative contractility of individual iMKs vs single platelets (E). M, mean; SD, standard deviation.
