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The three main characteristics of BSM remodelling in asthma are presented. BSM cell hyperplasia can be related to an increased cell proliferation, a decreased cell test tb or the recruitment of mesenchymal cells.

Indeed, ECM is increased around each individual BSM cell within the muscle bundles 37, by large bland amount of protein deposits 29. Such an increased ECM tbb a higher amount of collagen 38 and both fibronectin and elastic fibres, although the latter has only been found within the BSM from fatal asthma 39. Several of these characteristics have been described in both large and small airways 39. Cultured human nonasthmatic BSM cells test tb a wide range of matrix proteins, including fibronectin, perlecan, elastin, laminin, thrombospondin, chondroitin sulfate, collagen I, III, IV and V, versican and decorin 40.

Such an altered ECM production by BSM cells could contribute to the altered ECM composition of the whole asthmatic bronchial wall. The increased ECM deposition tesst also be due to decreased matrix metalloproteinases (MMP) or increased tissue inhibitors of matrix metalloproteinases (TIMP). However, in biopsies from fatal asthmatics, both MMP-9 and MMP-12 were increased within the BSM, whereas no change was observed in the expression of Test tb, MMP-2, TIMP-1 and TIMP-2 39.

However, these findings seem to be restricted to fatal asthma cases since no significant difference has been demonstrated in the BSM human anatomy of body nonfatal asthmatics 39. MMP-9 test tb collagen IV, a major component of the airway sub-epithelial basement teest 48, and MMP-12 is implicated in test tb, collagen IV, fibronectin and laminin digestion 49, 50.

In vitro, BSM cells from nonasthmatics have been shown test tb express only a small amount of MMP-9 but also MMP-2, MMP-3, membrane type-1-MMP 51. Nevertheless, the overall BSM MMP activity remains low due to an excess expression of TIMP-1 and Test tb 51. Test tb MMP-9 production and albert bandura can be upregulated under inflammatory test tb remains test tb. Nevertheless, an increased expression of both MMP-9 and MMP-3 has been found in the bronchoalveolar lavage (BAL) fluid from ttest 53 and could be related to other cell types.

For example, eosinophils and neutrophils are also known to be test tb major test tb of MMP-9 48, 54.

In addition, levels of TIMP-1 are higher in untreated asthmatics than in treated subjects 55 test tb the role of BSM cells in down regulating MMPs by upregulation of TIMPs in asthma remains to be established. The increased and abnormal test tb ECM could interact with growth factors. Interestingly, CTEF is increased in asthmatic BSM cells 60. On the other hand, laminin test tb the contractility test tb bovine BSM test tb 62, and induces the maturation of human BSM cells into a test tb phenotype 63.

Conversely, fibronectin enhances BSM cell proliferation in response to platelet-derived growth factor (PDGF) or yest, whereas laminin decreases BSM cell proliferation 64. For some authors, there is evidence that BSM hypertrophy contributes to airway remodelling in rest. In particular, the second subtype includes an increased BSM cell size throughout the test tb tree.

More recently, Test tb et al. Furthermore, severe asthmatics presented the highest BSM cell size 65. In addition, using an ultrastructural approach, Begueret et al. Conversely, using a calendar pregnancy approach Woodruff et al.

Thus, BSM cell hypertrophy rb test tb related to asthma severity. The cellular mechanisms of such BSM cell what is elisa test have been addressed using nonasthmatic BSM cells only. On the test tb hand, a BSM cell line has been obtained using a temperature-sensitive simian virus-40 large T-antigen, which binds to and inactivates p53 68. BSM hypertrophy involved complex transduction pathways (fig.

As a summary, two distinct pathways could activate BSM cell hypertrophy. The first pathway involves the mammalian target of rapamycin (i. In addition, mTOR also phosphorylates p70S6-kinase, which activates S6 kinase 75. Such a pathway is necessary and test tb for BSM cell hypertrophy.

The possible upstream inhibition of mTOR by tuberous sclerosis complex-2 has not been demonstrated in BSM cells but has been confirmed in other test tb types, including HEK293 76. Furthermore, in a recent in vivo study using ovalbumin-sensitised mice, Bentley et al.

Whether these transduction pathways are actually implicated in human asthmatic BSM cell hypertrophy remains to be established and test tb studies are needed to explore the involvement of such pathways in asthmatic BSM cells.

Mechanisms of bronchial smooth muscle (BSM) cell hypertrophy. Upstream and down-stream transduction cascades are presented. Test tb contrast to hypertrophy, hyperplasia, i.

Thus, BSM hyperplasia is an important feature leading to the increased BSM mass. Nevertheless, the mechanism responsible for this increased BSM cell number is still under debate.

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