In vivo inhibition of TLR4 in SCD mice. (A) Clustering of genes related to TLR4 Gene Ontology pathway in SS vs SA MSCs from RNA-sequencing analysis. Red star indicates significant fold change (FC) (P ≤ .05); N = 4 mice per group. To investigate the effect of TLR4 inhibition in SCD mice, SS mice were injected with 1 mg/kg TAK-242 for 5 days to systemically inhibit TLR4 activity and compared with vehicle-injected SS mice (control). (B-E) Using flow cytometry, the mean fluorescence intensity (MFI) of p38 expression among bone marrow MSCs (B) and MFI of p65 expression among bone marrow MSCs (C) was determined. Furthermore, using flow cytometry, the MFI of DCFDA among MSCs in the bone marrow (D) and MFI of DCFDA among HSCs in the bone marrow (E) were assessed. (F) Peripheral blood hematopoietic stem and progenitor cell population marked by Lineage-Sca1⁺Ckit⁺Flt3^– is represented as FC in number per mL relative to control. N = 3-4 mice for panels B-F. Data were analyzed with a 2-tailed, unpaired Student t test (B-F). Data are presented as mean ± standard error of the mean. *P ≤ .05, **P ≤ .01.