1M.V. Lomonosov Moscow State University, Moscow, Russia; 2N.M. Emanuel Institute of Biochemical Physics Russian Academy of Sciences, Moscow, Russia; email@example.com
Retinal degeneration is recognized as one of the leading causes of irreversible blindness. It is known, that intense light exposure (particularly short wavelengths of the visible spectrum - often referred to as blue light hazard) is a significant risk factor for the development of retinal pathologies. Light damage affects first of all retinal pigment epithelium cells (RPE), which perform multiple highly specialized metabolic and transport functions essential for homeostasis of retina. Now the Japanese quail Coturnix japonica is served as experimental animal model of accelerated aging and photodamage of retina. This organism has rather short lifespan (about 1,5 -2 years) and retinal morphological parameters, which are similar to human.
Structural changes of RPE were studied in Japanese quails females (age 9, 25, 39, 52, 78 weeks) by light, transmission electron microscopy, morphometric and TUNEL analyses after blue light damage (spectral band – 430-465 nm, doses 1-4 J, exposure time – 40 min). According to our light microscopic data, irradiation of birds’ retinas of all ages leads to thickening of RPE layer mostly due to elongation of apical microvilli of these cells. Ultrastructural analysis revealed significant changes in RPE ultrastructure only in young quails (age 9 and 25 weeks): 1) 2-fold increase in quantity of mitochondria of unusual shapes (ring- or dumb-bell shaped), which are rare in control; 2) 30% decrease in relative volume and quantity of myeloid bodies which could reflect phagocytosis level of RPE; 3) disorganization of the basal infoldings; 4) frequent presence of irregular shaped nuclei with invaginations of nuclear envelope and sometimes with highly condensed chromatin, resembling apoptotic nuclei. Indeed, TUNEL-positive RPE nuclei (4 %) were detected in blue light-damaged retinas of young quails, although no significant changes in number of apoptic nuclei were observed in old birds after irradiation.
So our study revealed that acute blue light exposure induces RPE damage predominantly in young birds: chondriom state, nuclei and myeloid bodies changed and cells with apoptotic signs appeared.