Comparison of Morphology of Human Macular and Peripheral Bruch's Membrane in Older Eyes

Abstract

Deposits in macular human Bruch's membrane (BrM) increase with age and have been postulated to be associated with age-related maculopathy. We used two ultrastructural methods to compare these deposits by electron microscopy in macular and peripheral BrM of eight eyes from donors 63-86 years of age. Quick-freeze/deep-etch (QFDE) was used to prepare replicas that showed the ultrastructure of deposits, and osmium-tannic acid-paraphenylenediamine (OTAP) was used to preserve small extracellular lipid particles. We found that an accumulation of lipoprotein-like particles (LLPs) occurred in the peripheral BrM just as it does in the macular region, but with perhaps a somewhat slower time course. The "lipid wall," reported in macular BrM, was also found occasionally in the peripheral regions. The same processes that lead to age-related accumulation of LLPs in macular BrM appear to also occur in the peripheral regions.

Aging, age-related macular degeneration, and the response-to-retention of apolipoprotein B-containing lipoproteins

“…This tightly packed layer of space-filling particles, too dense for volume fraction measurements, displaces the structural collagen fibers at the same location in younger eyes that help bind BrM to the RPE basal lamina. Interestingly, particle accumulation and Lipid Wall formation occurs not only in macular BrM, but also in the periphery, although less prominent in the latter region, and in somewhat older eyes (Johnson et al, 2007). Taken together, these observations are consistent with an interpretation that lipoprotein accumulation starts in the elastic layer, backs up into the inner collagenous layer, and eventually forms the Lipid Wall.…”

Apolipoprotein B-containing lipoproteins in retinal aging and age-related macular degeneration

“…QFDE analysis of normal eyes at different ages ( 92,93,145,146 ) reveals that signifi cant lipoprotein accumulation begins by the fourth decade of life in or near the elastic layer of BrM in the macula, and to a lesser degree, the periphery. This process is reminiscent of the preferential deposition of lipoprotein-derived EC near elastin in arterial intima ( 147 ).…”

Quick-freeze/deep-etch electron microscopy visualization of the mouse posterior pole

“…Our examination included the RPE, BrM, choroid and sclera, areas that may be particularly vulnerable and prone to structural alterations in retinal diseases, such as age-related macular degeneration. Previously, QFDE of human donor tissue from aged individuals revealed macromolecular components such as lipoprotein particles within BrM and ultra-structural features such as BrM inclusions, both characteristics of aging and age-related macular degeneration (Ruberti et al, 2003; Huang et al, 2007; Johnson et al, 2007; Huang et al, 2008). These features are not easily identified using conventional imaging techniques nor is it possible to manipulate human tissue to produce disease states in a controlled manner.…”

“…To date, the QFDE method (Heuser, 2011) has been used to successfully image neural synapses (Heuser and Salpeter, 1979), muscle actin/myosin interactions (Heuser and Cooke, 1983), intra/inter cellular structures of intestinal epithelial cells (Hirokawa and Heuser, 1981), and lipid accumulation in the aorta of rabbits (Frank and Fogelman, 1989; Haberland et al, 2001) and mice (Tamminen et al, 1999; Brown et al, 2004). Of particular importance to vision researchers, it has also been used to evaluate ocular tissues including the cornea (Yamabayashi et al, 1991; Hirsch et al, 1999), the trabecular meshwork in human eyes (Gong et al, 2002), the outer retinal vasculature and the pentalaminar extracellular matrix of Bruch’s membrane, in aged human eyes (Ruberti et al, 2003; Huang et al, 2007; Johnson et al, 2007; Huang et al, 2008). The latter studies resulted in revealing a novel aging phenomenon, namely the accumulation of lipoprotein particles within human Bruch’s membrane as a function of age (Ruberti et al, 2003; Huang et al, 2007), highlighting the value of this imaging technique.…”