Background-Atherosclerosis is largely attributed to chronic vascular injury, as occurs with excess cholesterol; however, the effect of concomitant vascular aging remains unexplained. We hypothesize that the effect of time in atherosclerosis progression is related to obsolescence of endogenous progenitor cells that normally repair and rejuvenate the arteries. Methods and Results-Here we show that chronic treatment with bone marrow-derived progenitor cells from young nonatherosclerotic ApoE Ϫ/Ϫ mice prevents atherosclerosis progression in ApoE Ϫ/Ϫ recipients despite persistent hypercholesterolemia. In contrast, treatment with bone marrow cells from older ApoE Ϫ/Ϫ mice with atherosclerosis is much less effective. Cells with vascular progenitor potential are decreased in the bone marrow of aging ApoE Ϫ/Ϫ mice, but cells injected from donor mice engraft on recipient arteries in areas at risk for atherosclerotic injury. Conclusions-Our

. Engineering skeletal myoblasts: roles of three-dimensional culture and electrical stimulation.

Mesenchymal stem cells (MSCs) transplanted into injured myocardium promote repair through paracrine mechanisms. We have previously shown that MSCs overexpressing AKT1 (Akt-MSCs) exhibit enhanced properties for cardiac repair. In this study, we investigated the relevance of Abi3bp towards MSC biology. Abi3bp formed extracellular deposits with expression controlled by Akt1 and ubiquitin-mediated degradation. Abi3bp knockdown/knockout stabilized focal adhesions and promoted stress-fiber formation. Furthermore, MSCs from Abi3bp knockout mice displayed severe deficiencies in osteogenic and adipogenic differentiation. Knockout or stable knockdown of Abi3bp increased MSC and Akt-MSC proliferation, promoting S-phase entry via cyclin-d1, ERK1/2 and Src. Upon Abi3bp binding to integrin-β1 Src associated with paxillin which inhibited proliferation. In vivo, Abi3bp knockout increased MSC number and proliferation in bone marrow, lung, and liver. In summary, we have identified a novel extracellular matrix protein necessary for the switch from proliferation to differentiation in MSCs.