Mechano Growth Factor - Defining the role of fluid shear stress in the expression of

New Exercise and Fitness Review

Mechano Growth Factor – Defining the role of fluid shear stress in the expression of

Related Articles Defining the role of fluid shear stress in the expression of early signaling markers for calcific aortic valve disease.

PLoS One. 2013;8(12):e84433

Authors: Sun L, Rajamannan NM, Sucosky P

Abstract
Calcific aortic valve disease (CAVD) is an active process presumably triggered by interplays between cardiovascular risk factors, molecular signaling networks and hemodynamic cues. While earlier studies demonstrated that alterations in fluid shear stress (FSS) on the fibrosa could trigger inflammation, the mechanisms of CAVD pathogenesis secondary to side-specific FSS abnormalities are poorly understood. This knowledge could be critical to the elucidation of key CAVD risk factors such as congenital valve defects, aging and hypertension, which are known to generate FSS disturbances. The objective of this study was to characterize ex vivo the contribution of isolated and combined abnormalities in FSS magnitude and frequency to early valvular pathogenesis. The ventricularis and fibrosa of porcine aortic valve leaflets were exposed simultaneously to different combinations of sub-physiologic/physiologic/supra-physiologic levels of FSS magnitude and frequency for 24, 48 and 72 hours in a double cone-and-plate device. Endothelial activation and paracrine signaling were investigated by measuring cell-adhesion molecule (ICAM-1, VCAM-1) and cytokine (BMP-4, TGF-?1) expressions, respectively. Extracellular matrix (ECM) degradation was characterized by measuring the expression and activity of the proteases MMP-2, MMP-9, cathepsin L and cathepsin S. The effect of the FSS treatment yielding the most significant pathological response was examined over a 72-hour period to characterize the time-dependence of FSS mechano-transduction. While cytokine expression was stimulated under elevated FSS magnitude at normal frequency, ECM degradation was stimulated under both elevated FSS magnitude at normal frequency and physiologic FSS magnitude at abnormal frequency. In contrast, combined FSS magnitude and frequency abnormalities essentially maintained valvular homeostasis. The pathological response under supra-physiologic FSS magnitude peaked at 48 hours but was then maintained until the 72-hour time point. This study confirms the sensitivity of valve leaflets to both FSS magnitude and frequency and suggests the ability of supra-physiologic FSS levels or abnormal FSS frequencies to initiate CAVD mechanisms.

PMID: 24376809 [PubMed - indexed for MEDLINE]

Mechano Growth Factor
MGF

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Mechano Growth Factor - Defining the role of fluid shear stress in the expression of

Mechano Growth Factor - Differential Axonal Conduction Patterns of Mechano-Sensitive

New Exercise and Fitness Review

Mechano Growth Factor – Differential Axonal Conduction Patterns of Mechano-Sensitive

Differential Axonal Conduction Patterns of Mechano-Sensitive and Mechano-Insensitive Nociceptors – A Combined Experimental and Modelling Study.

PLoS One. 2014;9(8):e103556

Authors: Petersson ME, Obreja O, Lampert A, Carr RW, Schmelz M, Fransén E

Abstract
Cutaneous pain sensations are mediated largely by C-nociceptors consisting of both mechano-sensitive (CM) and mechano-insensitive (CMi) fibres that can be distinguished from one another according to their characteristic axonal properties. In healthy skin and relative to CMi fibres, CM fibres show a higher initial conduction velocity, less activity-dependent conduction velocity slowing, and less prominent post-spike supernormality. However, after sensitization with nerve growth factor, the electrical signature of CMi fibres changes towards a profile similar to that of CM fibres. Here we take a combined experimental and modelling approach to examine the molecular basis of such alterations to the excitation thresholds. Changes in electrical activation thresholds and activity-dependent slowing were examined in vivo using single-fibre recordings of CM and CMi fibres in domestic pigs following NGF application. Using computational modelling, we investigated which axonal mechanisms contribute most to the electrophysiological differences between the fibre classes. Simulations of axonal conduction suggest that the differences between CMi and CM fibres are strongly influenced by the densities of the delayed rectifier potassium channel (Kdr), the voltage-gated sodium channels NaV1.7 and NaV1.8, and the Na+/K+-ATPase. Specifically, the CM fibre profile required less Kdr and NaV1.8 in combination with more NaV1.7 and Na+/K+-ATPase. The difference between CM and CMi fibres is thus likely to reflect a relative rather than an absolute difference in protein expression. In support of this, it was possible to replicate the experimental reduction of the ADS pattern of CMi nociceptors towards a CM-like pattern following intradermal injection of nerve growth factor by decreasing the contribution of Kdr (by 50%), increasing the Na+/K+-ATPase (by 10%), and reducing the branch length from 2 cm to 1 cm. The findings highlight key molecules that potentially contribute to the NGF-induced switch in nociceptors phenotype, in particular NaV1.7 which has already been identified clinically as a principal contributor to chronic pain states such as inherited erythromelalgia.

PMID: 25136824 [PubMed - as supplied by publisher]

Mechano Growth Factor
MGF

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Mechano Growth Factor - Differential Axonal Conduction Patterns of Mechano-Sensitive