MMP inhibition and hematopoietic recovery after 5-FU. (A) Compared with vehicle controls, WBC counts in C57Bl6 mice treated with 30 mg/kg doxycycline were impaired at different time points after 5-FU (200 mg/kg intravenously). P < .05 versus vehicle (n = 10; ANOVA). *P < .05 versus vehicle per time point. (B,C) Immunostaining on BM sections of WT mice for different MMPs at 7 days after 5-FU (200 mg/kg intravenously). MMP-2 (B, brown) was expressed in stroma cells/matrix and hematopoietic cells. MMP-12 (C, brown) was expressed in stroma cells/matrix and hematopoietic cells such as macrophages (black arrowheads). Magnification bars represent 50 μm. (D,E) Compared with their respective WT controls, WBC counts in MMP-2^−/− (D) and MMP-12^−/− mice (E) were impaired at different time points after 5-FU (200 mg/kg intravenously). P < .05 for each genotype versus WT (n = 8-15; ANOVA). *P < .05 versus WT per time point.