Abstract
Purpose: :
To evaluate age–related accumulation and size distribution of lipoprotein–like particles (LLPs) in human macular Bruch's membrane (BrM).
Methods: :
The inner collageneous (ICL), elastic (EL) and outer collageneous layers (OCL) of macular BrM of preserved, grossly normal eyes (donor age 27 to 77 years) were visualized by using the quick–freeze/ deep–etch technique. Image J (NIH) was used to evaluate morphometric data of LLPs seen in these regions. Combining these data with stereologic theory, the diameter distribution, mean diameter, and volume fraction (<font face="symbol">f</font>) of LLPs were determined as a function of donor age.
Results: :
The highest <font face="symbol">f</font> values in eyes < 30 yr were seen in the EL (<font face="symbol">f</font> = 0.0092) and OCL (<font face="symbol">f</font> = 0.0105). However, in eyes > 60 yr, the highest <font face="symbol">f</font> values were found in the ICL (<font face="symbol">f</font> = 0.1808) and EL (<font face="symbol">f</font> = 0.1034). In all three BrM layers, the <font face="symbol">f</font> value increased at least three–fold during lifespan. Mean LLP diameter increased from 40.2 nm to 81.3 nm in a positive linear relationship with donor age and with <font face="symbol">f</font> value. LLPs were found capable of fusing to form larger particles, which might result in a higher mean diameter in older eyes.
Conclusions: :
This study showed that the ICL and EL are the major locations for LLP deposition in Bruch’s membrane during the human lifespan, with the most abundant accumulation occurring in the ICL. Both quantification results were consistent with our previous qualitative examination (Huang et al, ARVO, 2005). The positive relationship between LLP size and the <font face="symbol">f</font> value might be caused by a higher probability for LLP fusion in a high LLP density environment.
Keywords: Bruch's membrane • lipids • aging