TIMP1 is upregulated in human sepsis survivors and inhibits Notch-mediated suppression of myelopoiesis of cultured human HSPCs. (A) Levels of circulating TIMP1 in age-matched healthy persons (n = 7) and in patients in ICU with sepsis (n = 22). Symbols indicate individual subjects; red lines show the mean value ± SD. ** P < 0.01 (unpaired two-tailed Student’s t test). (B) Mortality rates of septic patients with circulating TIMP1 levels higher than 600 ng/ml or lower than 550 ng/ml. (C) Circulating TIMP1 levels in healthy individuals (n = 7) or in sepsis survivors (n = 4) at 6 mo after release from ICU. Symbols show data from individual persons with the mean value ± SD. ** P < 0.01 (unpaired two-tailed Student’s t test). (D)Hes1 expression in human HSPCs. Human CD34⁺ HSPCs were cultured in medium with indicated stimuli for 5 h. Expression of Hes1 transcripts was determined by qRT-PCR. Induction fold of Hes1 is calculated as the ratio of Hes1 levels stimulated with DLL4 plus GI254023X or TIMP1 to that with DLL4 alone. Symbols depict data from three independent experiments. * P < 0.05; ns, P > 0.05 (unpaired two-tailed Student’s t test). RU, relative unit. (E) Cultured human HSPCs under the indicated conditions are FACS analyzed by the indicated markers. Percentages of CD11b⁺ cells developed in the 5-day culture are given. The suppression index of myeloid differentiation is calculated as the ratio of the percentage of CD11b⁺ cells generated with DLL4 ± TIMP1 to that without DLL4. Symbols depict data from three independent experiments. * P < 0.05; ** P < 0.01 (unpaired two-tailed Student’s t test).