Local inhibition of ornithine decarboxylase reduces vascular stenosis in a murine model of carotid injury.

OBJECTIVES: Polyamines are organic polycations playing an essential role in cell proliferation and differentiation, as well as in cell contractility, migration and apoptosis. These processes are known to contribute to restenosis, a pathophysiological process often occurring in patients submitted to revascularization procedures. We aimed to test the effect of α-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, on vascular cell pathophysiology in vitro and in a rat model of carotid arteriotomy-induced (re)stenosis. METHODS: The effect of DFMO on primary rat smooth muscle cells (SMCs) and mouse microvascular bEnd.3 endothelial cells (ECs) was evaluated through the analysis of DNA synthesis, polyamine concentration, cell viability, cell cycle phase distribution and by RT-PCR targeting cyclins and genes belonging to the polyamine pathway. The effect of DFMO was then evaluated in arteriotomy-injured rat carotids through the analysis of cell proliferation and apoptosis, RT-PCR and immunohistochemical analysis of differential gene expression. RESULTS: DFMO showed a differential effect on SMCs and on ECs, with a marked, sustained anti-proliferative effect of DFMO at 3 and 8 days of treatment on SMCs and a less pronounced, late effect on bEnd.3 ECs at 8 days of DFMO treatment. DFMO applied perivascularly in pluronic gel at arteriotomy site reduced subsequent cell proliferation and preserved smooth muscle differentiation without affecting the endothelial coverage. Lumen area in DFMO-treated carotids was 49% greater than in control arteries 4 weeks after injury. CONCLUSIONS: Our data support the key role of polyamines in restenosis and suggest a novel therapeutic approach for this pathophysiological process.

Appearance of remodelled and dendritic cell-rich alveolar-lymphoid interfaces provides a structural basis for increased alveolar antigen uptake in chronic obstructive pulmonary disease.

RATIONALE: The alveolar pathology in chronic obstructive pulmonary disease (COPD) involves antigen-driven immune events. However, the induction sites of alveolar adaptive immune responses have remained poorly investigated. OBJECTIVES: To explore the hypothesis that interfaces between the alveolar lumen and lymphoid aggregates (LAs) provide a structural basis for increased alveolar antigen uptake in COPD lungs. METHODS: Lung samples from patients with mild (Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I), moderate-severe (GOLD II-III), and very severe (GOLD IV) COPD were subjected to detailed histological assessments of adaptive immune system components. Never smokers and smokers without COPD served as controls. RESULTS: Quantitative histology, involving computerised three-dimensional reconstructions, confirmed a rich occurrence of alveolar-restricted LAs and revealed, for the first time, that the vast majority of vascular or bronchiolar associated LAs had alveolar interfaces but also an intricate network of lymphatic vessels. Uniquely to COPD lungs, the interface epithelium had transformed into a columnar phenotype. Accumulation of langerin (CD207)(+) dendritic cells occurred in the interface epithelium in patients with COPD but not controls. The antigen-capturing capacity of langerin(+) dendritic cells was confirmed by increased alveolar protrusions and physical T cell contact. Several of these immune remodelling parameters correlated with lung function parameters. CONCLUSIONS: Severe stages of COPD are associated with an emergence of remodelled and dendritic cell-rich alveolar-lymphoid interfaces. This novel type of immune remodelling, which predicts an increased capacity to respond to alveolar antigens, is suggested to contribute to aggravated inflammation in COPD.