Evolution of damage in the lens after in vivo close to threshold exposure to UV-B radiation: Cytomorphological study of apoptosis Konstantin Galichanin a, b, * , Stefan Löfgren a , Jan Bergmanson c , Per Söderberg b a St. Erik’s Eye Hospital, Karolinska Institutet, Stockholm, Sweden b Gullstrand Lab, Ophthalmology, Department of Neuroscience, Uppsala University Hospital, Uppsala, Sweden c Texas Eye Research and Technology Center, University of Houston College of Optometry, Houston, Texas, USA article info Article history: Received 14 May 2010 Accepted in revised form 10 June 2010 Available online 17 June 2010 Keywords: lens ultraviolet radiation cataract apoptosis repair light scattering microscopy abstract The purpose of the present study was to investigate cataractogenesis and recovery of lens damage after in vivo close to threshold ultraviolet (UV)-B radiation around 300 nm. Eighty six-week-old albino Spra- gueeDawley rats were familiarized to a rat restrainer five days prior to exposure. Groups of non- anesthetized rats were exposed unilaterally to 8 kJ/m 2 UVR-300 nm. The animals were sacrificed at 1, 7, 48 and 336 h following exposure. The lenses were extracted for imaging of dark-field lens macro anatomy and measurement of intensity of forward lens light scattering to quantify lens opacities. Three exposed lenses and one non-exposed lens from each time interval were examined with light and transmission electron microscopy (TEM). Macro anatomy and lens light scattering revealed that all contralateral non-exposed lenses were clear. The degree of lens opacity (difference in lens light scat- tering between exposed and non-exposed lenses) increased during the 336 h, reaching a plateau towards the end of the observation period. Light microscopy and TEM demonstrated that apoptotic features appeared in the epithelium already 1 h after UVR exposure, and small vacuoles were seen in the outer cortex. Epithelial damage occurs during the first 48 h after exposure and is followed by regenerative repair at 336 h post-exposure. Apoptotic epithelial cells were phagocytized by adjacent epithelial cells. Cortical fiber cells exhibited increasing damage throughout the observation period without any clear repair after 336 h. In conclusion, acute UVR-induced cataract is partly a reversible. Lens epithelium is a primary target for UVR exposure. Damage to cortical fiber cells remained irreversible. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Cataract is the number one cause of blindness in the world (Brian and Taylor, 2001; Evans et al., 2004; West, 2000). Phacoe- mulsification is the most prevalent cure of cataract in developed countries (Asbell et al., 2005). In spite of the progress made in cataract surgical techniques and materials during the last ten years, cataract continues to be a substantial public-health issue globally (Resnikoff et al., 2004). The Eye Disease Prevalence Research Group has projected that the number of US patients with cataract will increase by 50% by 2020 (Congdon et al., 2004). To join the efforts for blindness prevention the World Health Organization with other institutions has launched the Global Initiative for the Elimination of Avoidable Blindness “VISION 2020: the Right to Sight” (Thylefors, 1998). The magnitude of the cataract problem emphasizes the importance of development of cataract prevention and treatment strategies. Solar radiation is the major source of UVR (Pitts, 1990). Exposure to sunlight has been correlated with the development of human senile cataract (Hiller et al., 1977; ItalianeAmerican Cataract Study, 1991; West and Valmadrid, 1995). Population-based studies in United States (Cruickshanks et al., 1992; Taylor et al., 1988), Australia (McCarty et al., 2000) and Japan (Sasaki et al., 2003) reported association between exposure to UVR-B and cortical cataract formation. Moreover, animal models have proven that exposure to UVR-B induces cataract (Jose and Pitts, 1985; Löfgren et al., 2003; Meyer et al., 2008; Michael et al., 1996; Pitts et al., 1977; Söderberg, 1988; Wegener, 1995). The vertebrate ocular lens is a highly organized, compact and transparent structure that has evolved to refract light entering the eye. The lens comprises densely packed fibers and a single layer of epithelial cells on its anterior surface, enclosed by a thick elastic lens capsule. The entire homeostasis, in which the lens develops, differentiates and grows throughout life, is maintained by all the * Address correspondence to: Konstantin Galichanin, Gullstrand Lab, Ophthal- mology, Dept. of Neuroscience, Uppsala University Hospital, SE-751 85 Uppsala, Sweden. Tel.: þ46 18 611 3716; fax: þ46 18 50 48 57. E-mail address: konstantin.galichanin@neuro.uu.se (K. Galichanin). Contents lists available at ScienceDirect Experimental Eye Research journal homepage: www.elsevier.com/locate/yexer 0014-4835/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.exer.2010.06.009 Experimental Eye Research 91 (2010) 369e377