Alessio Palini

The recent hypothesis that postnatal microglia are maintained independently of circulating monocytes by local precursors that colonize the brain before birth has relevant implications for the treatment of various neurological diseases, including lysosomal storage disorders (LSDs), for which hematopoietic cell transplantation (HCT) is applied to repopulate the recipient myeloid compartment, including microglia, with cells expressing the defective functional hydrolase. By studying wild-type and LSD mice at diverse time-points after HCT, we showed the occurrence of a short-term wave of brain infiltration by a fraction of the transplanted hematopoietic progenitors, independently from the administration of a preparatory regimen and from the presence of a disease state in the brain. However, only the use of a conditioning regimen capable of ablating functionally defined brain-resident myeloid precursors allowed turnover of microglia with the donor, mediated by local proliferation of early immigrants rather than entrance of mature cells from the circulation.

BACKGROUND#ENTITYSTARTX02014;: Adaptive T-cell response is promoted during atherogenesis and results in the differentiation of naïve CD4(+)T cells to effector and/or memory cells of specialized T-cell subsets. Aim of this work was to investigate the relationship between circulating CD4(+)T-cell subsets and atherosclerosis. METHODS AND RESULTS#ENTITYSTARTX02014;: We analyzed 57 subsets of circulating CD4(+)T cells by 10-parameter/8-color polychromatic flow cytometry (markers: CD3/CD4/CD45RO/CD45RA/CCR7/CCR5/CXCR3/HLA-DR) in peripheral blood from 313 subjects derived from 2 independent cohorts. In the first cohort of subjects from a free-living population (n=183), effector memory T cells (T(EM): CD3(+)CD4(+)CD45RA(-)CD45RO(+)CCR7(-) cells) were strongly related with intima-media thickness of the common carotid artery, even after adjustment for age (r=0.27; P<0.001). Of note, a significant correlation between T(EM) and low-density lipoproteins was observed. In the second cohort (n=130), T(EM) levels were significantly increased in patients with chronic stable angina or acute myocardial infarction compared with controls. HLA-DR(+)T(EM) were the T(EM) subpopulation with the strongest association with the atherosclerotic process (r=0.37; P<0.01). Finally, in animal models of atherosclerosis, T(EM) (identified as CD4(+)CD44(+)CD62L(-)) were significantly increased in low-density lipoprotein receptor and apolipoprotein E deficient mice compared with controls and were correlated with the extent of atherosclerotic lesions in the aortic root (r=0.56; P<0.01). CONCLUSIONS#ENTITYSTARTX02014;: Circulating T(EM) cells are associated with increased atherosclerosis and coronary artery disease in humans and in animal models and could represent a key CD4(+)T-cell subset related to the atherosclerotic process. (J Am Heart Assoc. 2012;1:27-41.).