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Immunohistochemical localisation of d-β-aspartic acid-containing proteins in climatic droplet keratopathy
  1. Y Kaji1,
  2. T Oshika1,
  3. Y Takazawa2,
  4. M Fukayama2,
  5. N Fujii3
  1. 1
    Department of Ophthalmology, Tsukuba University Institute of Clinical Medicine, Ibaraki, Japan
  2. 2
    Department of Pathology, University of Tokyo Graduate School of Medicine, Tokyo, Japan
  3. 3
    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 305-8575, Japan; sanken-tky{at}


Aim: Biologically uncommon d-β-aspartic acid (d-β-Asp) accumulates in the body with age and is involved in the ageing process. In the present study, the localisation of d-β-Asp-containing proteins was investigated in surgical specimens with climatic droplet keratopathy (CDK), one of the ocular changes related to the ageing process.

Methods: Immunohistochemical localisation of d-β-Asp-containing proteins using polyclonal antibodies raised against d-β-Asp-containing peptides was examined in three corneas with CDK, three corneas with interstitial keratitis, six corneas with bullous keratopathy, and three corneas without any corneal diseases.

Results: Strong immunoreactivity to d-β-Asp-containing peptide was detected in all the surgical specimens with CDK. In contrast, no immunoreactivities to d-β-Asp-containing peptides were detected in the surgical specimens with bullous keratopathy, interstitial keratitis, or no corneal diseases.

Conclusions: CDK was regarded as aggregations of d-β-Asp-containing proteins. The formation of d-amino acids in protein causes the different side chain orientations and β-linkage of Asp residues elongates the main chain of proteins. Therefore, d-β-Asp formation will result in a partial unfolding of proteins leading to the aggregation of proteins seen in CDK.

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  • 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 Yuichi Kaji.

  • Patient consent: Obtained.