Andreina Poggi

Monocyte Chemotactic Protein 1 (MCP-1) Is a Mitogen for Cultured Rat Vascular Smooth Muscle Cells

The involvement of inflammatory mechanisms in the progression of atherosclerosis has recently been suggested. Monocyte chemotactic protein 1 (MCP-1) is a soluble protein which is implicated in acute and chronic inflammatory processes, including atherosclerosis. We evaluated the effect of human recombinant MCP-1 on the in vitro proliferation of rat vascular smooth muscle cells (VSMCs). Incubation of VSMCs with MCP-1 (50-200 ng/ml) in the presence of 0.5% FCS significantly increased cell proliferation, [3H]-thymidine incorporation and the proliferative S fraction, measured by flow cytometry, compared to control cells. The proliferative effect of MCP-1 was specific, as shown by inhibition with a rabbit polyclonal serum to MCP-1. Moreover, the mitogenic effect of MCP-1 was significantly inhibited by downregulation of protein kinase C (PKC) activity and by incubation with H-7, a protein kinase inhibitor, suggesting the involvement of the PKC system. Verapamil, a Ca2+ channel blocker, also reduced the stimulatory effect of MCP-1 on cell proliferation. This study demonstrates that MCP-1 does not merely have a chemotactic activity, but also a mitogenic effect on cultured rat VSMCs.

Increased Plasma Levels of Platelet-Derived Growth Factor Activity in Patients with Progressive Systemic Sclerosis

Abstract We measured mitogenic activity of whole blood serum and platelet-poor plasma-derived serum of a group of 10 patients with progressive systemic sclerosis and of 8 controls. Mitogenic activity of plasma-derived serum was greater in patients than in controls, in the absence of other signs of platelet activation. This increased activity was inhibited by specific antibodies, anti-platelet derived growth factor, suggesting that circulating levels of platelet-derived growth factor may be present in progressive systemic sclerosis patients. Platelet-derived growth factor, released either by platelets or by monocytes, might play a role in the pathogenesis of scleroderma.

Effect of ditazole, an inhibitor of platelet aggregation, on a metastasizing tumour in mice

Effect of ditazole, an inhibitor of platelet aggregation, on a metastasizing tumour in mice

Differences in the glutathione system of cultured aortic smooth muscle cells from young and aged rats

We studied the relation between the glutathione (GSH) system and cell proliferation in a model of smooth muscle cells (SMC) derived from the thoracic aorta of 4-6-week-old (young) and 15-month-old (aged) rats. SMC from aged rats showed greater levels of total non-protein thiol compounds (T-SH), increased glutathione transferase (GST) and increased glutathione reductase (GSSG-Red) activities compared with cells from young rats. These changes were associated with an increased proliferation rate of SMC from aged rats. To evaluate the role of GSH on cell proliferation better, a specific inhibitor of gamma-glutamyl-cystein synthetase, DL-buthionine-SR-sulphoximine (BSO) was used. BSO showed a dose-dependent inhibition of cell growth, with an IC50 of 10(-4) M, after 48-72 h of incubation. Removal of BSO restored cell growth, further suggesting a link between GSH levels and vascular cell proliferation. The inhibitory effect of BSO was about two times greater on SMC from young than on SMC from aged rats. BSO showed 56% inhibition on the proliferation of SMC from young rats and 32% inhibition on SMC from aged rats (10(-4) M, 72 h of incubation). A parallel reduction of GSH levels of 38% and 19% for SMC from young and aged rats, respectively, was observed, suggesting that age-related factors may influence the involvement of GSH system in cell proliferation.

Reduced smooth muscle cell regeneration in Yoshida (YOS) spontaneously hypercholesterolemic rats

Hypercholesterolemia is a predisposing factor for atherosclerosis. We studied the response to damage of vascular smooth muscle cells (SMC) from normocholesterolemic Brown Norway (BN) and from spontaneously hyper-cholesterolemic Yoshida (YOS) rats (16-24 month old). The regrowth rate of SMC from BN and YOS rats after freeze-induced damage was similar in the presence of fetal calf serum and of serum derived from normocholesterolemic rats, while it was reduced in the presence of serum from hypercholesterolemic rats. Freeze-injury of the abdominal aorta was followed by reduced neointima formation in YOS rats, as compared to BN rats, confirming the impaired response of vascular cells from hypercholesterolemic rats to injury. This defect may be due either to lipids or to unknown factors present in the hyperlypidemic serum.

New model of vascular cell repair in vitro

Dear Editor: The maintenance of endothelial monolayer integrity is an important function of endothehal cells. Numerous in vitro studies have been performed to investigate the mechanisms of vascular integrity and repair following injury (for review s e e ref. 2). Vascular repair models include systems where mechanical injury is provoked with razor blade (5), spatula (1) or the tip of a thin nylon filament (4). Although mechanical injury has been shown to be a reliable tool in regeneration experiments, it is not, in our opinion, without disadvantages: (a) the underlying extracellular matrix is usually damaged [with the only exception of the single cell wound model (7)]; (b) the wound surface area is very difficult to standardize; (c) microorganism contamination may occur in long term experiments. To avoid these difficulties we suggest a method of freeze injury. Briefly, a metal bar (aluminium or copper), cooled to the temperature of liquid nitrogen, is placed on the outer surface of a plastic well or flask containing confluent cells. A frozen area, shghtly larger than the bar size, occurs on the inner surface. After melting of ice, detached cells are washed out so that the injury area

Endothelialized myointimal thickening in the rat aorta as a result of extensive freeze injury.

The regeneration of rat aorta intima and medial layer was examined after extensive freeze injury that caused the death of both endothelial and smooth muscle cells. After 1 month complete re-endothelialization of the denuded area was observed. In parallel, myointimal thickening was formed by the smooth muscle cells (SMC) from the uninjured edges and its thickness increased with time. The SMC of myointimal thickening were stellate in the upper part and elongated near the internal elastic lamina. No regenerative response was seen in the medial layer, consisting only of elastic and collagen fibers, and its thickness was reduced during regeneration. These results show that the regenerative response of medial SMC to extensive freeze injury proceeds in the form of intimal thickening.

Arterial lesions in hypercholesterolaemic Yoshida rats: morphological evaluation

The aortic wall structure of genetically determined hypercholesterolaemic (Yoshida) and control (Brown-Norway) rats was investigated by transmission and scanning electron and light microscopy. Leucocyte adherence mostly at branch sites and irregular protrusive structures were observed on the endothelial surface of the thoracic aorta of Yoshida, but not of Brown-Norway rats. The subendothelial space of the aortic wall of Yoshida rats was characterized by intimal cushions consisting of smooth muscle cells of synthetic phenotype associated with adhering leucocytes and lipid droplets. Lipid infiltration of the cytoplasm of medial smooth muscle cells was observed on the inner part of the aortic arch and on the lateral parts of the large branches of Yoshida rats. This model of spontaneously hyperlipidaemic Yoshida rats is an appropriate moderate injury system, which may be useful for studies of multiple risk factors for atherogenesis.