Abstract
Purpose :
Limbal stromal niche structures are essential in the maintenance of limbal epithelial stem cells. The purpose of this study was to examine limbal stromal structures by clinical imaging methods such as in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography with or without angiography (aOCTA, aOCT) and correlate findings with immunohistological features of limbal niche structures.
Methods :
The corneal limbus of 6 healthy individuals was examined by IVCM, aOCT and aOCTA. Immunohistological analysis was performed in cadaveric cornea samples sectioned in directions corresponding to the IVCM and OCT imaging, with putative markers for limbal niche cells (CD90, CD105, nestin, N-cadherin, Melan-A, SSEA-4), blood/lymphatic vessels (CD31), nerves (acetyl-tubulin and beta-III-tubulin), limbal epithelial progenitor cells (CK14/15, p63) and hyaluronic acid (HA).
Results :
Limbal stroma associated with the palisades of Vogt (POV) was hyperreflective on IVCM and was located between the area of capillaries running in POV and deeper vessels running towards the sclera. On aOCT and aOCTA limbal stroma appeared as a small hyperreflective area between superficial and deep limbal blood vessels. Immunofluorescence showed numerous mesenchymal cells positive for putative niche markers surrounding the deep and superficial vessels identified on IVCM and aOCT. Nerves run alongside the blood vessels and all structures are surrounded by a limbal stroma rich in hyaluronic acid.
Conclusions :
The limbal stromal hyperreflective areas on IVCM and aOCT located between deep and superficial limbal vessels correspond to the HA-rich stroma. Limbal vessels and nerves running in this stroma are surrounded by putative niche cells, thus damage to limbal blood vessels not only causes limbal ischaemia but also indicates potential direct damage to niche cells.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.