Immune system humanization in dyslipidemic Rag2-KO/IL2rg-KO/CD47-KO/LDL-R KO mice controls atherosclerosis

Abstract

Abstract Background and aim Given the key role of the immune response during atherosclerosis and the therapeutic interest of biologics targeting human immune cells, the need of experimental models to translate molecular mechanisms and to test therapeutic approaches for atherosclerosis is continuously increasing. Here we describe the characteristics of an innovative immunodeficient mouse humanized with hCD34+ cells on an atheroprone background. Methods LDLR-KO mice were crossed with the immunodeficient C57BL/6J strain Rag2-KO/IL2rg-KO/CD47-KO (TKO, IMSR_JAX:025730) to generate an immunocompromised dyslipidemic mouse recipient TKO-LDLR KO of human hematopoietic stem cells (hCD34+). Results TKO-LDLR KO were first characterized for their immune and metabolic profile. TKO mice are deficient in mature lymphocytes and NK cells and this profile was conserved in TKO-LDLR KO mice. Under high cholesterol diet for 8 weeks, both male and females TKO-LDLR KO present monocytosis with increased levels of Ly6Chi monocytes compared to TKO-LDLR KO at standard diet, develop marked dyslipidemia (total cholesterol 870.9 and 890.1 mg/dL male and females respectively), steatosis and atherosclerosis. This profile confirms the suitability of TKO-LDLR KO mice for atherosclerosis studies. Next we tested the impact of immune system humanization on atherosclerosis. TKO-LDLR KO pups received a low-dose irradiation (150-200 cGy) and thereafter 1,5-2 x 10^5 hCD34+ were injected with in the liver. Engraftment of human leukocytes (hCD45+) was evaluated after two months by flow cytometry analysis from tail blood. This approach allows to reconstitute between 10-30% of hCD45+, mainly B and T cells. The humanization with hCD34+ cells affected atherosclerosis development as compared to non-humanized TKO-LDLR KO mice. Conclusion We have generated and characterized for the first time a humanized dyslipidemic TKO-LDLR KO mice. This mouse model presents human B and T cells and represent and important toll to investigate the impact of biologics targeted toward human targets in the context of atherosclerosis.