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.

FIGURE 1

Replica showing macular (A) and peripheral (B) BrM from the RPE at the top of the figures to the choriocapillaris on the bottom. Basal lamina (BL), inner collagenous layer (ICL), elastic layer (EL), outer collagenous layer (OCL), choriocapillaris (CC), lamina densa (LD); 63-year-old eye. Note that panels (A) and (B) are of different magnifications, because the fracture angle is different in (A) than (B). They are included in this illustration because these replicas showed the most complete demonstration of all layers in both regions. Bars are 1 μm.

FIGURE 2

Replica showing choriocapillaris (CC), basal lamina (BL), and the outer collagenous layer (OCL) of macular (A) and peripheral (B) BrM; 63-year-old eye. Bars are 500 nm.

FIGURE 3

Surface of the endothelium of the choriocapillaris showing several fenestrations (dark arrow) and presumed artifactual pores (white arrow) that formed during tissue preparation for QFDE; 64-year-old eye, macular region. Bar is 100 nm.

FIGURE 4

Replica of the elastic layer in macular (A) and peripheral (B) BrM of a 63-year-old eye. Arrows point to LLPs. Elastic fiber (EF). Bars are 500 nm.

FIGURE 5

Negative contrast OTAP images of macular (A) and peripheral (B) BrM from a 64-year-old donor. Basal lamina of the RPE (BL), inner collagenous layer (ICL), elastic fiber (EF), outer collagenous layer (OCL), endothelial cell (E), red blood cell (RBC). The small white dots are collagen fibrils cut in cross section. (A) Arrow shows four LLPs in elastic layer. (B) Arrows show two LLPs, one of which was only partially preserved by the OTAP. Bars are 500 nm.

FIGURE 6

Replicas of the ICL and basal lamina (BL) of the RPE from the macula (A) and periphery (B) of BrM; 64-year-old eye. Arrows in (A) point to clumps of small granules. Bars are 200 nm.

FIGURE 7

Replica of the ICL layer in the macular (A) and peripheral (B) regions of a 76-year-old eye. Arrowheads in (A) point at a few of the many small granules. Many LLPs and a few collagen fibrils are evident. Lamina densa (LD). Bars are 200 nm.

FIGURE 8

Negative contrast OTAP images of the macular (A) and peripheral (B) regions of BrM of a 76-year-old eye. Arrows point at LLPs that in OTAP images are bright on their boundaries and usually somewhat darker in their core. Rod-like structures and small bright dots in (B) are collagen fibrils. Basal lamina of the RPE (BL), elastic fiber (EF). Bars are 500 nm.

FIGURE 9

Two distinct appearances of lipid wall (LW) are seen in this 78-year-old eye. The macula (A) shows many LLPs and small granules, and the periphery (B) shows mainly LLPs in the lipid wall. Bars are 200 nm.

FIGURE 10

Detailed view of lipid wall layer in macula of 78-year-old eye. Many small granules surround the LLPs. Bar is 100 nm.

FIGURE 11

Negative-contrast thin-section images of the region between inner collagenous layer (ICL) and basal lamina (BL) of RPE in the macula (A) and periphery (B) of BrM of a 78-year-old eye. Lipid wall (LW). Bar is 500 nm.