Characterization of Calcium Phosphate Spherical Particles in the Subretinal Pigment Epithelium–Basal Lamina Space in Aged Human Eyes

Abstract

Purpose: Micrometer-sized spherules formed of hydroxyapatite or whitlockite were identified within extracellular deposits that accumulate in the space between the basal lamina (BL) of retinal pigment epithelium (RPE) and the inner collagenous layer of Bruch's membrane (sub-RPEeBL space). This investigation aimed to characterize the morphologic features, structure, and distribution of these spherules in aged human eyes with and without clinical indications of age-related macular degeneration (AMD).Design: Experimental study.Participants: Five human eyes with varying degrees of sub-RPEeBL deposits were obtained from the University College London Institute of Ophthalmology and Moorfield's Eye Hospital Tissue Repository or the Advancing Sight Network. Two eyes were reported as having clinical indications of AMD (age, 76e87 years), whereas 3 were considered healthy (age, 69e91 years).Methods: Cadaveric eyes with sub-RPEeBL deposits were embedded in paraffin wax and sectioned to a thickness of 4-10 mm. Spherules were identified and characterized using high-resolution scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy, and time-of-flight secondary ion mass spectroscopy.Main Outcome Measures: High-resolution scanning electron micrographs of spherules, the size-frequency distribution of spherules including average diameter, and the distribution of particles across the central-peripheral axis. Elemental maps and time-of-flight secondary ion mass spectra also were obtained.Results: The precipitation of spherules is ubiquitous across the central, mid-peripheral, and far-peripheral axis in aged human eyes. No significant difference was found in the frequency of spherules along this axis. However, statistical analysis indicated that spherules exhibited significantly different sizes in these regions. Indepth analysis revealed that spherules in the sub-RPEeBL space of eyes with clinical signs of AMD were significantly larger (median diameter, 1.64 mm) than those in healthy aged eyes (median diameter, 1.16 mm).Finally, spherules showed great variation in surface topography and internal structure.Conclusions: The precipitation of spherules in the sub-RPEeBL space is ubiquitous across the centraleperipheral axis in aged human eyes. However, a marked difference exists in the size and frequency of spherules in eyes with clinical signs of AMD compared to those without, suggesting that the size and frequency of spherules may be associated with AMD.

Multiscale Multimodal Characterization and Simulation of Structural Alterations in Failed Bioprosthetic Heart Valves

“…from macrophages or other cells, cell-derived structures or particles originating from the blood), as previously suggested (45–48) for the same particles (same shape, size and composition) in native valves. Furthermore, similar particles have also been observed in tumour vasculature (49), the Bruch’s membrane of the eye (50, 51), and other cardiovascular tissues(52) suggesting a host-environment origin shared between several pathologies.…”

A Common Finding in Foveal-Sparing Extensive Macular Atrophy With Pseudodrusen Implicates Basal Laminar Deposits

“…As confirmed in previous histological studies, BLamD was invariably detected with RPE cells at this stage of degeneration. 34,35,47–49 In our opinion, these findings may be overlooked in clinical practice and assimilated as just geographic atrophy. Therefore, detailed identification of GA phenotypes and their clinical interpretation may be crucial before recruitment into a clinical trial to increase the chance of success.…”

“…Subretinal hyperreflective deposits assimilable to RPD/SDD are also visible on ( C ) ( inset ). After 4 years, the same region of interest (ROI) on FAF ( D ) shows a fine, diffuse punctiform hyperautofluorescence, more evident in the superior perifovea close to vascular arcades, corresponding to multiple hyperreflective spherules 49 on NIR ( E-II ); the OCT B-scan demonstrates a diffusely indistinct IZ and EZ bands ( F -inset). The RPE appeared irregular with a medium reflectivity material underneath that allows the visualization of the Bruch membrane (BrM, yellow arrows ).…”

Sub-retinal pigment epithelium tubules in non-neovascular age-related macular degeneration

“…HIRD can be identified on OCT as a hyporeflective core encircled by a hyperreflective cap with hyperreflective dots, which may mimic SRT appearance. Unlike SRT, however, this OCT signature is often accompanied by a glistening appearance on color fundus photograph, hyperreflectivity on NIR, and variable FAF manifestations 2 , 22 . The whitlockite spherules represent the reflective component of refractile drusen, responsible for the glistening and the reflectivity on OCT 2 , 23 .…”