Figure 1
Figure 1. tPA mobilizes hematopoietic myelomonocytic cells into the circulation, a process dependent on plasmin and MMP-9–mediated growth factor release. (A-D) C57BL/6 mice were injected intraperitoneally with recombinant tPA (n = 8 per group) or G-CSF (n = 3) from day 0 until day 2. The total number of WBCs (A), neutrophils (B), and monocytes (C) were counted. (D) FACS analysis of CD45+CD11b+ cells in peripheral blood of tPA-treated, G-CSF–treated, or BSA-PBS–treated mice (n = 3 per group). (E-G) Plasma VEGF-A levels were determined by ELISA in MMP-9−/− (E), Plg−/− (F) and wild-type control mice (n = 6) as well as in mice treated with tranexamic acid, a drug that impairs plasmin activation (n = 3), after tPA administration. Double asterisks indicate a significant difference between tPA-treated MMP-9 or Plg wild-type mice and their matching knockout controls. (H) PBMCs were isolated at the indicated time points from tPA-treated and untreated C57BL/6 mice. Cells were cultured under serum-free conditions for 24 hours. Supernatants were analyzed for VEGF-A by ELISA (n = 6). (I) tPA-treated and untreated C57BL/6 mice were coinjected with antibodies against murine VEGF-A or (J) cotreated with batroxobin intraperitoneally (fibrinogen-reducing agent). (K) Mice were treated with tPA, nonenzymatically active tPA, or vehicle control. (L) tPA- or carrier-injected C57BL/6 mice were coinjected with the plasmin inhibitor tranexamic acid. (I-L) The frequency of circulating CD45+CD11b+ cells was determined on day 2 (n = 3 per group). (M) Plg+/+ and Plg−/− mice received tPA intraperitoneally or BSA-PBS from day 0 to day 2. WBC counts were assessed (n = 5 per group; **P < .001; comparing Plg−/− to Plg+/+ group). (N) C57BL/6 mice were injected with tPA and anti–c-Kit or control antibodies. The frequency of circulating CD45+CD11b+ cells was measured on day 2 (n = 3 per group). (O) WBC counts were determined in MMP-9+/+ and MMP-9−/− mice after tPA administration (n = 4). The asterisk indicates a significant difference between tPA-treated MMP-9−/− and MMP-9+/+ mice. (I-L,N) Asterisks denote a significant difference between the indicated groups. (A-D) Asterisks indicate a significant difference between the BSA-PBS and tPA or G-CSF groups. Single asterisk, P < .05; double asterisk, P < .001. Values represent the mean ± SEM.

tPA mobilizes hematopoietic myelomonocytic cells into the circulation, a process dependent on plasmin and MMP-9–mediated growth factor release. (A-D) C57BL/6 mice were injected intraperitoneally with recombinant tPA (n = 8 per group) or G-CSF (n = 3) from day 0 until day 2. The total number of WBCs (A), neutrophils (B), and monocytes (C) were counted. (D) FACS analysis of CD45+CD11b+ cells in peripheral blood of tPA-treated, G-CSF–treated, or BSA-PBS–treated mice (n = 3 per group). (E-G) Plasma VEGF-A levels were determined by ELISA in MMP-9−/− (E), Plg−/− (F) and wild-type control mice (n = 6) as well as in mice treated with tranexamic acid, a drug that impairs plasmin activation (n = 3), after tPA administration. Double asterisks indicate a significant difference between tPA-treated MMP-9 or Plg wild-type mice and their matching knockout controls. (H) PBMCs were isolated at the indicated time points from tPA-treated and untreated C57BL/6 mice. Cells were cultured under serum-free conditions for 24 hours. Supernatants were analyzed for VEGF-A by ELISA (n = 6). (I) tPA-treated and untreated C57BL/6 mice were coinjected with antibodies against murine VEGF-A or (J) cotreated with batroxobin intraperitoneally (fibrinogen-reducing agent). (K) Mice were treated with tPA, nonenzymatically active tPA, or vehicle control. (L) tPA- or carrier-injected C57BL/6 mice were coinjected with the plasmin inhibitor tranexamic acid. (I-L) The frequency of circulating CD45+CD11b+ cells was determined on day 2 (n = 3 per group). (M) Plg+/+ and Plg−/− mice received tPA intraperitoneally or BSA-PBS from day 0 to day 2. WBC counts were assessed (n = 5 per group; **P < .001; comparing Plg−/− to Plg+/+ group). (N) C57BL/6 mice were injected with tPA and anti–c-Kit or control antibodies. The frequency of circulating CD45+CD11b+ cells was measured on day 2 (n = 3 per group). (O) WBC counts were determined in MMP-9+/+ and MMP-9−/− mice after tPA administration (n = 4). The asterisk indicates a significant difference between tPA-treated MMP-9−/− and MMP-9+/+ mice. (I-L,N) Asterisks denote a significant difference between the indicated groups. (A-D) Asterisks indicate a significant difference between the BSA-PBS and tPA or G-CSF groups. Single asterisk, P < .05; double asterisk, P < .001. Values represent the mean ± SEM.

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