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In Vitro Photoentrainment and Circadian Endothelial Permeability

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In Vitro Photoentrainment and Circadian Endothelial Permeability

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Samenvatting

The rotation of the earth around its own axis results in a 24 hour recurring cycle. During this period environmental properties are subject to change, the most noticeable variable being light. During the day, life on earth is exposed to significantly higher doses of ultraviolet radiation, which is detrimental for replicating DNA. Therefore, organisms acquired a circadian clock which generates rhythms of approximately 24 hours. The circadian clock allows these organisms to anticipate and prepare for environmental changes during the night/day cycle by regulating many properties, such as nearly all physiological and cellular processes. However, the periodicity of the circadian clock, as the word circadian implies, is not exactly 24 hours. Because light is the most reliable daily recurrence, it is used to keep the internal clock in sync. Light input is received by the retina, where melanopsin is expressed in retinal ganglion cells, and gets translated via the retinohypothalamic track to the suprachiasmatic nucleus (SCN), which regulates several biological functions and output processes, through generation of electrical, neuronal and hormonal activities.
Susceptibility to or detrimental effects of medicine and drugs may vary during these rhythmic processes. This makes the circadian clock worthwhile to research for clinical purposes. Since many companies do not want to be involved with animal testing, in vitro research of the circadian clock is a suitable alternative. However, in vitro cells are unable to synchronize, because they lack signals from the central pacemaker, the SCN.
Here we show that melanopsin induces the ability of cultured cells to synchronize their clock to a light/dark cycle. Light pulses are shown to have varying effects on the expression of clock(-related) genes during different stages of the clock. The expression of melanopsin allowed NIH3T3 and SIMH4 cells to entrain to a daily one-hour light pulse within 5 or 3 days respectively.
Provided that NIH3T3 and SIMH4 cells are photoentrainable, the same methods could be applied to endothelial cells to research possible circadian rhythmicity of permeability to immune cells. This could mean that the immune system is better prepared for antigens at certain times of the day. We show that EA.hy926 and HMEC-I endothelial cells do not have a strong rhythmic expression of clock genes, and therefore seem unsuitable for chronotherapy research.
These findings suggest that inducing melanopsin expression in cultured cells could create and maintain clock synchronization on a population level when placed in a consistent light/dark cycle. EA.hy926 and HMEC-I cells do not show robust circadian oscillation in clock gene expression and therefore other cells will have to be chosen to further investigate the possibility of circadian endothelial permeability rhythmicity.

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OrganisatieAvans Hogeschool
OpleidingBiologie en Medisch Laboratoriumonderzoek-Breda
AfdelingATGM Academie voor de technologie van Gezondheid en Milieu
Jaar2015
TypeBachelor
TaalEngels

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