LDLR and Hypercholesterolemia: It was recently found that prolonged hypercholesterolemia in the low-density lipoprotein receptor-deficient (Ldlr-/-) mouse model led to a complete loss of the resident-derived lipid-laden foam cells, as they were ultimately replaced entirely by recruited blood monocytes, indicating the key role of monocyte recruitment to sustain macrophage proliferation and to allow the expansion of multiple generations of macrophages during plaque progression (48).