Oral communication, iL10

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

The other ones: non-cutaneous melanocytes

SPEAKER L. Kos #whois submiter ?
AUTHOR(s) F.C. Brito, N. Fernandez, K. Balani, A. Agarwal, L. Kos

Melanocytes are generally associated with pigment producing cells found in the skin. However, they can be found in organs and tissues as diverse as the eye, inner ear, brain, heart and fat. Except for those found in the retinal pigment epithelium of the eye that originate directly from the neural ectoderm, all others are derived from neural crest precursors. Melanocytes found in the skin exert protective functions against the damaging effects of ultraviolet radiation. The exact function of the other melanocytes have yet to be fully determined but may include detoxification and protection against oxidative stress due to the capacity of melanin to scavenge reactive oxygen radicals. In the heart, melanocytes are specifically located in the pulmonary veins, atrial walls, and atrioventricular (AV) valves. The melanocytes found in the pulmonary veins and atrial walls have adrenergic and muscarinic receptors and have been linked to atrial fibrillation. We have focused on those melanocytes that reside in the AV valves. They reach the heart at a time when major remodeling events are taking place in the endocardial cushion that are necessary for the proper formation of the AV valve leaflets. The resulting arrangement of organized layers of extracellular matrix (ECM) and the biomechanical properties of the leaflets are required for the valves to regulate blood flow direction. We hypothesized that melanocytes influence the distribution of ECM components in the AV valves and as a consequence may affect their biomechanical characteristics. We used a modified Movat’s pentachrome stain to reveal the arrangement of ECM components in AV valve leaflets with wild type numbers of melanocytes, no melanocytes (EdnrBs-l/s-l mutants) and large numbers of melanocytes (K5-Edn3 transgenics). Our results indicated that there was an increase in the amount of collagen in the leaflets with no melanocytes while there was an increase in the amount of proteoglycans and elastin in the leaflets with excessive numbers of melanocytes. To test for the leaflets’ biomechanical properties, a quasi-static and nanodynamic (Nano-DMA) mechanical analysis was evaluated using a Hysitron’s Tribolndenter®. The quasi-static nanoindentation of the wild type leaflet indicated its viscoelastic property. Nano-DMA measurements of the storage modulus of the wild type leaflet showed and average stiffness of approximately 7.5 GPa. The storage modulus of the leaflets with no melanocytes (approximately 3.5 GPa) was much smaller when compared to the wild type whereas that for the leaflets with extra numbers of melanocytes was much higher (approximately 11.5 GPa). Our results suggest that the presence of melanocytes in the AV valves affect their ECM patterning resulting in changes in their stiffness.



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Université de Bordeaux 2 & Conseil Régional Aquitaine