A role for local inflammation in the formation of drusen in the aging eye.
OBJECTIVE
The accumulation of numerous or confluent drusen, especially in the macula, is a significant risk factor for the development of age-related macular degeneration (AMD). Identifying the origin and molecular composition of these deposits, therefore, has been an important, yet elusive, objective for many decades. Recently, a more complete profile of the molecular composition of drusen has emerged.


METHODS
In this focused review, we discuss these new findings and their implications for the pathogenic events that give rise to drusen and AMD.


METHODS
Tissue specimens from one or both eyes of more than 400 human donors were examined by light, confocal or electron microscopy, in conjunction with antibodies to specific drusen-associated proteins, to help characterize the transitional events in drusen biogenesis. Quantification of messenger RNA from the retinal pigment epithelium (RPE)/choroid of donor eyes was used to determine if local ocular sources for drusen-associated molecules exist.


RESULTS
The results indicate that cellular remnants and debris derived from degenerate RPE cells become sequestered between the RPE basal lamina and Bruch's membrane. We propose that this cellular debris constitutes a chronic inflammatory stimulus, and a potential "nucleation" site for drusen formation. The entrapped cellular debris then becomes the target of encapsulation by a variety of inflammatory mediators, some of which are contributed by the RPE and, perhaps, other local cell types; and some of which are extravasated from the choroidal circulation.


CONCLUSIONS
The results support a role for local inflammation in drusen biogenesis, and suggest that it is analogous to the process that occurs in other age-related diseases, such as Alzheimer's disease and atherosclerosis, where accumulation of extracellular plaques and deposits elicits a local chronic inflammatory response that exacerbates the effects of primary pathogenic stimuli.
Center for the Study of Macular Degeneration, Neuroscience Research Institute, University of California, Santa Barbara 93106, USA. d_anders@lifesci.ucsb.edu
Don H
DH
Anderson
Robert F
RF
Mullins
Gregory S
GS
Hageman
Lincoln V
LV
Johnson
D000375:Aging / Q000473:pathology*; D005136:Eye Proteins / Q000378:metabolism; D006801:Humans; D008268:Macular Degeneration / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D018613:Microscopy, Confocal; D010857:Pigment Epithelium of Eye / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D015593:Retinal Drusen / Q000209:etiology* / Q000378:metabolism / Q000473:pathology*; D012173:Retinitis / Q000150:complications* / Q000378:metabolism / Q000473:pathology*
D005136:Eye Proteins; D012333:RNA, Messenger