Detection of activity and mRNA of MMP-9 in platelets. (A) Zymography of highly purified platelet lysates prepared according to 3 different methods (lane 3 = complete lysis buffer; lane 4 = the same lysis buffer but without EDTA and Na₃VO₄; lane 5 = 3 cycles of freezing in liquid nitrogen and thawing at 37°C). Two concentrations of MMP-9, used as standards, are shown in lanes 1 and 2. No MMP-9 is detectable in platelet lysates prepared by any of the 3 methods. (B) Zymography of highly purified platelets, alone (lane 1) or with added white blood cells at platelet leukocyte ratios of 789:1 (lane 4), 24 000:1 (lane 3), and 47 000:1 (lane 2). PMNs lysate and a concentration of MMP-9 used as standards, are shown in lanes 5 and 6, respectively. (C) RNA-seq analysis for MMP-9 mRNA in platelet and PMN lysates. Matched sequences are aligned to the MMP-9 gene using the Integrated Genome Browser (IGB). Gene map (bottom portion of the panel, oriented 5′-3′ direction) is represented by thick (exon) and thin (intron) lines. The transcript levels were quantified using RPKM (reads per kilobase of exon model per million mapped reads). The RPKM for adult PMNs without any treatment is 82.6916 compared with 0.4619 for platelets.