Abstract
Objectives:
We test a novel paradigm in the pathogenesis of atherosclerosis as an imbalance in the pro-repair function of circulating bone marrow-derived stem cells (BMDSC) that can be modulated by Notch activity.
Methods:
Significance Analysis of Microarray (SAM) and PCRArray/immunoblotting were used to study Notch activity in empirically-derived repair-competent versus repair-incompetent BMDSC (RC-BMDSC vs. RI-BMDSC). In parallel experiments, BMDSC with low-Notch activity were generated by transducing cells with dominant-negative Master-mind like 1 (DN-MAML1)/lentivirus (Notch-inhibited). Mock/lentivirus transduced cells were used as control. 5 x 10^6 Lin- BMDSC were infused bi-weekly for 4 consecutive weeks i.v. into Apo E -/- mice under high fat diet (HFD); (N=5/group). Atherosclerosis plaque burden was assessed using Oil Red O staining and blinded computerized quantitative measurements.
Results:
Of 289 genes with differential expression in RC-BMDSC vs. RI-BMDSC, by SAM, Notch1 expression was significantly elevated in RI-BMDSC compared to RC-BMDSC, p<0.0009. Notch activity was higher in BMDSC (EPC and MSC) from ApoE-/- mice before initiation of HFD (Notch target genes, Hes-1 and Hey-1, with 6.6- and 8.2-fold higher expression, respectively (p<0.05)). Compared to mice infused with control Lin-BMDSC, ApoE-/- mice treated with DN-MAML1/Lin-BMDSC had significantly decreased aortic plaque burden (p<0.05).
Conclusions:
For the first time we demonstrate a direct correlation between Notch activity and pro-repair function in BMDSC that modulates atherosclerosis plaque burden. Lower Notch activity in BMDSC appears to confer a pro-repair or repair-competent BMDSC phenotype. These novel findings provide rationale for further studies into clinically-relevant cell-based therapy for atherosclerosis.