CXCR4 and VEGFR1 mediated impaired MK distribution. (A) Concentration of MMP-9 in the BM analyzed by ELISA in the ITP group (n = 30) and control group (n = 28). (B) Concentration of VEGF in the BM analyzed by ELISA in the ITP group (n = 30) and control group (n = 28). (C) Expression of MMP-9 mRNA in CD41⁺ MKs analyzed by RT-PCR in the ITP group (n = 30) and control group (n = 28). (D) Expression of VEGF mRNA in CD41⁺ MKs analyzed by RT-PCR in the ITP group (n = 30) and control group (n = 28). (E) Expression of VEGFR1 mRNA in CD41⁺ MKs analyzed by RT-PCR in the ITP group (n = 30) and control group (n = 28). (F) VEGFR1 protein levels in CD41⁺ MKs analyzed by western blot analysis in the ITP group (n = 30) and control group (n = 28). (G) Model illustrating the BM vascular niche alterations, disrupted MK distribution, and reduced platelet production in ITP patients. Data are pooled from 10 independent experiments with 4 to 8 samples per experiment (A-E). Data are shown as mean ± SD. Each point represents the mean adjusted value of 3 replicates for each individual patient. P values were calculated using the Mann-Whitney U test. *P < .001.