In vivo confocal microscopic analysis of normal human anterior limbal stroma.
OBJECTIVE
To characterize the microarchitecture of anterior limbal stroma in healthy individuals using in vivo confocal microscopy (IVCM) and to correlate it with mesenchymal stem cells (MSCs), a component of the limbal niche.


METHODS
The corneal side of the superior limbus was scanned in 30 eyes of 17 normal subjects beyond the basal epithelium, deep into the stroma using an HRT III laser scanning microscope. The IVCM findings were correlated with the immunohistochemical features of MSCs in the anterior limbal stroma.


RESULTS
Clusters of hyperreflective structures were observed in the anterior limbal stroma, subjacent to the basal epithelium (depth, 50.2 ± 8.7 μm to 98 ± 12.8 μm), but not in the corneal stroma. The structures showed unique morphology compared with epithelial cells, keratocytes, neurons, and dendritic cells. In parallel, confocal analysis of immunostained sections showed clusters of cells, double positive for MSC-specific markers (CD90 and CD105) in the anterior limbal stroma at a depth of 55.3 ± 12.7 μm to 72 ± 37.6 μm. The organization and distribution of the MSC clusters locates them within the hyperreflective region in the anterior limbal stroma.


CONCLUSIONS
The hyperreflective structures, demonstrated for the first time in the human anterior limbal stroma, probably represent an important component of the limbal niche. Our approach of in vivo imaging may pave the way for assessing the limbal stromal health.
*Department of Immunology and Stem Cell Biology, Aravind Medical Research Foundation, Madurai, India; †International Centre for Eye Health, London School of Hygiene and Tropical Medicine, London, United Kingdom; ‡Department of Cornea, Aravind Eye Hospital and Postgraduate Institute of Ophthalmology, Madurai, India; and §Advisor-Research, Aravind Medical Research Foundation, Madurai, India.
Saumi
S
Mathews
Jaya Devi
JD
Chidambaram
Shruti
S
Lanjewar
Jeena
J
Mascarenhas
Namperumalsamy Venkatesh
NV
Prajna
Veerappan
V
Muthukkaruppan
Gowri Priya
GP
Chidambaranathan
D000328:Adult; D015415:Biomarkers; D002452:Cell Count; D003319:Corneal Stroma / Q000166:cytology*; D019573:Epithelium, Corneal / Q000166:cytology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D016850:Limbus Corneae / Q000166:cytology*; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology; D018613:Microscopy, Confocal; D008875:Middle Aged; D055815:Young Adult
D015415:Biomarkers