Figure 3.

Bone Marrow Activity After Cardiac Ischemia-Reperfusion and Permanent Left Anterior Descending Coronary Artery Occlusion Are Similar

(A) Cardiac ischemia induces proliferation, metabolic activation, and myeloid cell egress in/from the bone marrow. We probed these processes via molecular imaging. (B)¹⁸F-fluorothymidine (FLT) PET/CT was performed 2 days after IR/PO surgery. ¹⁸F-FLT was injected 90 minutes before the scan. (C) Quantification of ¹⁸F-FLT signal in the lumbar vertebrae (n = 5-7; P = 0.032 control vs IR; P = 0.018 control vs PO; P = 0.92 IR vs PO; Kruskal-Wallis test) and representative ¹⁸F-FLT PET/CT images showing higher activity for both IR and PO mice. (D) Ex vivo gamma counting of ¹⁸F-FLT uptake in the bone marrow (n = 8-9; P = 0.006 control vs IR; P = 0.006 control vs PO; P = 0.92 IR vs PO; Kruskal-Wallis test). (E) Flow cytometry analysis of bone marrow cells 3 days after IR/PO. Representative histograms of BrdU expression in Lin⁻Sca-1⁺cKit⁺ (LSK) cells and quantification of BrdU-positive cells. BrdU (1 mg) was injected i.P. 24 hours before analysis (n = 6-8, P = 0.014 control vs IR; P < 0.001 control vs PO; P = 0.18 IR vs PO; Kruskal-Wallis test). (F)¹⁸F-FDG PET/CT was performed 2 days after IR/PO surgery. ¹⁸F-FDG was injected 30 minutes before imaging. (G) Quantification of ¹⁸F-FDG signal in the lumbar vertebrae (n = 5-7; P = 0.005 control vs IR; P = 0.025 control vs PO; P = 0.52 IR vs PO; Kruskal-Wallis test) and representative images showing higher activity in IR and PO mice compared with control mice. (H) Ex vivo gamma counting of ¹⁸F-FDG uptake in the bone marrow (n = 6-8; P = 0.008 control vs IR; P = 0.011 control vs PO; P = 0.92 IR vs PO; Kruskal-Wallis test). (I) Number of LSK cells in the bone marrow 3 days after IR/PO (n = 6-8; P = 0.003 control vs IR; P = 0.052 control vs PO; P = 0.33 IR vs PO; Kruskal-Wallis test) with representative plots. (J) CD11b PET was performed 3 days after myocardial infarction. The ⁸⁹Zr-labeled CD11b-specific nanobody was injected 2 days after myocardial infarction. (K) Quantification of PET signal in the lumbar vertebrae (n = 5-8; P = 0.001 control vs IR; P = 0.032 control vs PO; P = 0.41 IR vs PO; Kruskal-Wallis test) and representative images showing lower signal in mice with IR or PO surgery compared with control. (L) Ex vivo gamma counting of tracer uptake in the bone marrow (n = 6-8; P = 0.017 control vs IR; P = 0.039 control vs PO; P = 0.77 IR vs PO; Kruskal-Wallis test). (M) Representative flow plots of blood samples, gated on viable cells. Significantly higher numbers of CD11b⁺ cells were observed in the blood of IR and PO animals 2 days after infarction (n = 9-14; P = 0.021 control vs IR; P = 0.025 control vs PO; P = 0.87 IR vs PO; 1-way ANOVA). Data are presented as mean ± SEM, unless otherwise specified. ∗P <0.05; ∗∗P <0.01, ∗∗∗P <0.001. Abbreviations as in Figures 1 and 2.