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Immunohistochemical localisation of d-β-aspartic acid in pingueculae
  1. Y Kaji1,
  2. T Oshika1,
  3. F Okamoto1,
  4. N Fujii2
  1. 1
    Department of Ophthalmology, Tsukuba University Institute of Clinical Medicine, Tsukuba, Ibaraki, Japan
  2. 2
    Research Reactor Institute, Kyoto University, Kumatori, Sennan, Osaka, Japan
  1. Dr Y Kaji, Department of Ophthalmology, Tsukuba University Institute of Clinical Medicine, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8565, Japan; sanken-tky{at}umin.ac.jp

Abstract

Background: d-β-Aspartic acid residues, which are biologically uncommon, have been reported to accumulate in various proteins of the living body with age. In the present study, d-β-aspartic acid-containing proteins were found to be localised in pingueculae, which represent one of the most prominent age-related ocular changes.

Methods: Surgical specimens of conjunctivae with or without pingueculae were obtained from eight patients. Immunohistochemical localisation of d-β-aspartic acid-containing proteins was performed using a polyclonal antibody against d-β-aspartic acid-containing peptides.

Results: Strong immunoreactivity to d-β-aspartic acid-containing peptides was detected in the subepithelial amorphous materials of all surgical specimens with pingueculae. In contrast, no immunoreactivity to d-β-aspartic acid-containing peptides was detected in the specimens without pingueculae.

Conclusions: Pingueculae are thought to be aggregates of proteins that contain d-β-aspartic acid residues. It is known that the conversion of l- to d-aspartyl residues is accelerated by ultraviolet irradiation. In addition, d-β-aspartic acid-containing proteins, in general, tend to aggregate with each other and accumulate in the tissues. These facts indicate that ultraviolet irradiation-induced racemisation of aspartic acid is closely related to the development of pingueculae.

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Footnotes

  • Competing interests: None.

  • Funding: This work is supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Young Scientists, 18791259 (2006–2008) and for Scientific Research, 21592216 (2009–2011), Japan.

  • Ethics approval: Ethics approval was provided by Tsukuba University Hospital.

  • Patient consent: Obtained.

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