Bruch's membrane calcification in pseudoxanthoma elasticum: comparing histopathology and clinical imaging

Sara Risseeuw, Matthew G. Pilgrim, Sergio Bertazzo, Connor Brown, Lajos Csincsik, Sarah Fearn, Richard B. Thompson, Arthur A. Bergen, Jacoline B. ten Brink, Elod Kortvely, Wilko Spiering, Jeannette Ossewaarde van Norel, Redmer van Leeuwen, Imre Lengyel

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Abstract

Purpose: To investigate the histology of Bruch's membrane (BM) calcification in pseudoxanthoma elasticum (PXE) and correlate this to clinical retinal imaging. Design: Experimental study with clinicopathological correlation. Subjects and Controls: Six postmortem eyes from 4 PXE patients and 1 comparison eye from an anonymous donor without PXE. One of the eyes had a multimodal clinical image set for comparison. Methods: Calcification was labeled with OsteSense 680RD, a fluorescent dye specific for hydroxyapatite, and visualized with confocal microscopy. Scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (SEM-EDX) and time-of-flight secondary ion mass spectrometry (TOF-SIMs) were used to analyze the elemental and ionic composition of different anatomical locations. Findings on cadaver tissues were compared with clinical imaging of 1 PXE patient. Main Outcome Measures: The characteristics and topographical distribution of hydroxyapatite in BM in eyes with PXE were compared with the clinical manifestations of the disease. Results: Analyses of whole-mount and sectioned PXE eyes revealed an extensive, confluent OsteoSense labeling in the central and midperipheral BM, transitioning to a speckled labeling in the midperiphery. These areas corresponded to hyperreflective and isoreflective zones on clinical imaging. Scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy and TOF-SIMs analyses identified these calcifications as hydroxyapatite in BM of PXE eyes. The confluent fluorescent appearance originates from heavily calcified fibrous structures of both the collagen and the elastic layers of BM. Calcification was also detected in an aged comparison eye, but this was markedly different from PXE eyes and presented as small snowflake-like deposits in the posterior pole. Conclusions: Pseudoxanthoma elasticum eyes show extensive hydroxyapatite deposition in the inner and outer collagenous and elastic BM layers in the macula with a gradual change toward the midperiphery, which seems to correlate with the clinical phenotype. The snowflake-like calcification in BM of an aged comparison eye differed markedly from the extensive calcification in PXE. Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Original languageEnglish
Article number100416
Number of pages15
JournalOphthalmology Science
Volume4
Issue number2
Early online date12 Dec 2023
DOIs
Publication statusPublished - 01 Mar 2024

Bibliographical note

Funding Information:
The TOF-SIMS analysis was funded by the Engineering and Physical Sciences Research Council , UK (Grant EP/H006060/1 ) and by the Natural Environment Research Council , UK (Grant NE/J013382/1 ). The authors would like to thank the patients and their relatives who agreed to donate tissue for research. The tissue for this project was provided by the Dutch National Expertise Center of PXE, the Netherlands Institute for Neuroscience, the University College London Institute of Ophthalmology and Moorfields Eye Hospital Eye Tissue Repository supported by National Institute for Health Research funding. Imre Lengyel is a member of the International Network on Ectopic Calcification (INTEC, www.itnintec.com )

Funding Information:
Supported by Rotterdamse Stichting Blindenbelangen , Stichting Vrienden UMC Utrecht, Donders-Binkhorststichting, Fischer Stichting, Stichting tot verbetering van het Lot der Blinden, Stichting PXE Fonds (S.R.); National Eye Institute, EY 030443, NIH (RBT); Unrestricted grant (I.L.) and a postdoctoral fellowship (M.P.) from Hoffman LaRoche. Fight for Sight UK (S.B. and I.L.). I.L. and R.T. are supported by the grant “Ectopic soft tissue calcification (NIH-P01 AG081167). The funding organizations had no role in design or conduct of this research.

Funding Information:
Supported by Rotterdamse Stichting Blindenbelangen, Stichting Vrienden UMC Utrecht, Donders-Binkhorststichting, Fischer Stichting, Stichting tot verbetering van het Lot der Blinden, Stichting PXE Fonds (S.R.); National Eye Institute, EY 030443, NIH (RBT); Unrestricted grant (I.L.) and a postdoctoral fellowship (M.P.) from Hoffman LaRoche. Fight for Sight UK (S.B. and I.L.). I.L. and R.T. are supported by the grant “Ectopic soft tissue calcification (NIH-P01 AG081167). The funding organizations had no role in design or conduct of this research.The TOF-SIMS analysis was funded by the Engineering and Physical Sciences Research Council, UK (Grant EP/H006060/1) and by the Natural Environment Research Council, UK (Grant NE/J013382/1). The authors would like to thank the patients and their relatives who agreed to donate tissue for research. The tissue for this project was provided by the Dutch National Expertise Center of PXE, the Netherlands Institute for Neuroscience, the University College London Institute of Ophthalmology and Moorfields Eye Hospital Eye Tissue Repository supported by National Institute for Health Research funding. Imre Lengyel is a member of the International Network on Ectopic Calcification (INTEC, www.itnintec.com)

Publisher Copyright:
© 2023

Keywords

  • Bruch's membrane
  • Calcification
  • Hydroxyapatite
  • Pseudoxanthoma elasticum

ASJC Scopus subject areas

  • Ophthalmology

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