Preparation and characterization of highly porous, biodegradable polyurethane scaffolds for soft tissue applications

Mechanisms controlling vascular smooth muscle cell (VSMC) plasticity and renewal still remain to be elucidated completely. A class of small RNAs called microRNAs (miRs) regulate gene expression at the post-transcriptional level. Here, we show a critical role of the miR-143/145 cluster in SMC differentiation and vascular pathogenesis, also through the generation of a mouse model of miR-143 and -145 knockout (KO). We determined that the expression of miR-143 and -145 is decreased in acute and chronic vascular stress (transverse aortic constriction and in aortas of the ApoE KO mouse). In human aortic aneurysms, the expression of miR-143 and -145 was significantly decreased compared with control aortas. In addition, overexpression of miR-143 and -145 decreased neointimal formation in a rat model of acute vascular injury. An in-depth analysis of the miR-143/145 KO mouse model showed that this miR cluster is expressed mostly in the SMC compartment, both during development and postnatally, in vessels and SMC-containing organs. Loss of miR-143 and miR-145 expression induces structural modifications of the aorta, because of an incomplete differentiation of VSMCs. In conclusion, our results show that the miR-143/145 gene cluster has a critical role during SMC differentiation and strongly suggest its involvement in the reversion of the VSMC differentiation phenotype that occurs during vascular disease.

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The knockout of miR-143 and -145 alters smooth muscle cell maintenance and vascular homeostasis in mice: correlates with human disease

As in human disease, macrophages (MO) are central players in the development and progression of experimental atherosclerosis. In this study we have evaluated the phenotype of MO associated with progression of atherosclerosis in the apolipoprotein E (ApoE) knockout (KO) mouse model.We found that bone marrow-derived MO submitted to M1 and M2 polarization specifically expressed arginase (Arg) II and Arg I, respectively. This distinct arginase expression was used to evaluate the frequency and distribution of M1 and M2 MO in cross-sections of atherosclerotic plaques of ApoE KO mice. Early lesions were infiltrated by Arg I(+) (M2) MO. This type of MO favored the proliferation of smooth muscle cells, in vitro. Arg II(+) (M1) MO appeared and prevailed in lesions of aged ApoE KO mice and lesion progression was correlated with the dominance of M1 over the M2 MO phenotype. In order to address whether the M2->M1 switch could be due to a phenotypic switch of the infiltrated cells, we performed in vitro repolarization experiments. We found that fully polarized MO retained their plasticity since they could revert their phenotype. The analysis of the distribution of Arg I- and Arg II-expressing MO also argued against a recent recruitment of M1 MO in the lesion. The combined data therefore suggest that the M2->M1 switch observed in vivo is due to a conversion of cells already present in the lesion. Our study suggests that interventional tools able to revert the MO infiltrate towards the M2 phenotype may exert an atheroprotective action.

/pdf/macrophage-plasticity-in-experimental-atherosclerosis-2mkllzu9rj.pdf

Macrophage Plasticity in Experimental Atherosclerosis

Preparation and rheological characterization of a gel form of the porcine urinary bladder matrix.

Microintegrating smooth muscle cells into a biodegradable, elastomeric fiber matrix.

The vascular smooth muscle cell plays a significant role in many important cardiovascular disorders, and smooth muscle biology is therefore important to cardiovascular research. The mouse is critical to basic cardiovascular research, largely because techniques for genetic manipulation are more fully developed in the mouse than in any other mammalian species. We describe here a technique for isolating smooth muscle cells from a single mouse aorta. This technique is particularly useful when material is limiting, as is frequently the case when genetically modified animals are being characterized.

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Isolation of vascular smooth muscle cells from a single murine aorta.

We stimulated differentiation of purified rat neural crest stem cells (NCSCs) into smooth muscle cells (SMCs) in culture, then subtracted NCSC sequences from SMC sequences to make a cDNA library specific for differentiating smooth muscle cells. Sequence analysis of the library shows that a large subset of clones is strongly associated with smooth muscle biology, confirming the overall success of the differentiation and subtraction procedures. Of this subset of clones, more than half encode proteins that have previously been shown to be upregulated in atherosclerotic or injured vascular smooth muscle as compared to normal vascular smooth muscle. Thus, a set of genes activated in differentiating smooth muscle of the neural crest lineage is also activated in atherosclerotic or injured vascular smooth muscle.

Rebecca L. Leach

Papers

Isolation of vascular smooth muscle cells from a single murine aorta.

A set of genes activated in differentiating smooth muscle is also activated in smooth muscle from injured arteries or atherosclerotic lesions