Related Experiment Video
Updated: Aug 10, 2026
Isolation of Intact Eyeball to Obtain Integral Ocular Surface Tissue for Histological Examination and Immunohistochemistry
Published on: October 20, 2019
The HNK-1 carbohydrate epitope in the eye: basic science and functional implications
1Ophthalmic Pathology Laboratory, Department of Ophthalmology, Helsinki University Central Hospital, PO Box 220 (Haartmaninkatu 4C, Helsinki), FIN-00029, HUS, Finland. marita.uusitalo@hus.fi
Insights
The HNK-1 carbohydrate epitope is crucial in eye structure and disease. Antibodies targeting HNK-1 help identify new cells and understand conditions like glaucoma and cataracts.
Area of Science:
- Ophthalmology
- Cell Biology
- Carbohydrate Chemistry
Background:
- The HNK-1 carbohydrate epitope is present on various cell surface and extracellular matrix molecules.
- It plays a role in cell adhesion and has emerged as a valuable tool in ocular research.
Purpose of the Study:
- To investigate the distribution and role of the HNK-1 epitope in the human eye.
- To explore its involvement in ocular development, physiology, and diseases.
Main Methods:
- Utilized antibodies against the HNK-1 epitope for identification and characterization of ocular cells and tissues.
- Examined HNK-1 distribution in various ocular structures and during development.
- Analyzed HNK-1 presence in ocular disease contexts like glaucoma, exfoliation syndrome, and cataracts.
Main Results:
- Identified a novel cell type, subepithelial matrix cells, in the ciliary body expressing the HNK-1 epitope.
- Mapped the HNK-1 epitope in multiple ocular tissues including epithelia, lens capsule, retina, and optic nerve.
- Demonstrated the HNK-1 epitope's presence in ocular diseases, aiding in diagnosis and understanding pathogenesis.
Conclusions:
- The HNK-1 epitope is a significant marker in ocular tissues, involved in structural integrity and cell adhesion.
- It is implicated in the pathogenesis of various eye diseases, including glaucoma, exfoliation syndrome, and cataracts.
- Further research into HNK-1 bearing molecules will enhance understanding of ocular physiology and disease.
Abstract:
The HNK-1 carbohydrate epitope is part of many cell membrane and extracellular matrix molecules. It has been implicated in cell to cell and cell to extracellular matrix adhesion, and antibodies to the HNK-1 epitope are emerging as a versatile tool in eye research. They have been used to identify a novel cell type in the human eye, the subepithelial matrix cells that reside in the inner connective tissue layer (ICTL) of the ciliary body. Although these cells resemble fibroblasts in ultrastructure, they form a distinct cell population that differs in its antigenic profile from fibroblasts of other tissues. These cells are associated with the elastic fiber system of the ICTL. Other structures in the human eye that harbor the HNK-1 epitope in a nonrandom pattern are the ciliary and iris epithelia, the zonular lamella, the lens capsule, the retina, glial cells of the optic and ciliary nerves, and scleral fibroblasts. The HNK-1 epitope in the eye appears early during embryonic development and is phylogenetically conserved, but many interspecies differences exist in its distribution. The role of the HNK-1 epitope may be to structurally stabilize the ciliary body and the retina, and to participate in zonular attachments. The HNK-1 epitope has been linked with many common eye diseases. The subepithelial matrix cells seem to be susceptible to undergo irreversible damage as a result of glaucoma, thermal injury, and tissue compression. This epitope has proved to be useful in identifying intraocular deposits of exfoliation syndrome. It can explain the adhesiveness of exfoliation material. Intraocular exfoliation material differs in HNK-1 immunoreactivity from the extraocular fibrillopathy of exfoliation syndrome and its presence in fellow eyes also argues against the concept of unilateral exfoliation syndrome. The HNK-1 epitope is found in the extracellular matrix of secondary cataract and anterior subcapsular cataract, and it may contribute to their pathogenesis. Finally, the HNK-1 epitope can be used to trace neuroepithelial derivatives of the optic vesicle in developmental anomalies and in tumors of the eye. Eventual identification of molecules that bear the HNK-1 epitope in the eye will likely shed light on many aspects of ocular physiology and pathobiology
