Heme-induced microstructural neuroaxonal damage is associated with poor cognitive responses in SCD mice. (A-B) Representative DTI image from AA and SS mice challenged with vehicle or heme and quantitation of FA (n = 6; M, 3; F, 3). (C-D) Elevated SMI32 accumulation compared to MBP and quantitation of staining intensity (SMI32/MBP ratio) indicating increased white matter injury in the SS mice at 24 hours following heme challenge (n = 5; M, 3; F, 2; original magnification ×20). (E-F) Representative photomicrograph and quantitation of GFAP-positive (GFAP⁺) astrocytes in cerebral tissue sections from SS and SSH mice (original magnification ×20; n = 6; M, 4; F, 2). (G-I) The SS mice were subjected to NOR testing at baseline followed by 7-days and 14-days post-heme challenges in a longitudinal fashion (n = 14; M, 8; F, 6). (G) Representative track plot from NOR testing showing halted movement of SS mice at day 7 and 14 following heme challenge compared to their baseline movement. (H-I) Memory and learning behavioral parameters including the exploration time (H), discrimination index (I) during NOR testing in the SS mice prior to and following heme injection indicating poor cognitive responses following heme challenge. Unpaired t test for panels B,D,F; 1-way ANOVA for panels H-I. ∗P < .05, ∗∗P < .01, ∗∗∗P < .001. F, female mice; M, male mice; ns, not significant.