Abstract
Purpose :
Despite the distribution of corneal nerves having been widely studied previously, this novel work gives a better understanding of the distribution of nerves in corneal surfaces. It provides new findings due to the differential staining of nerves by NF and TUBB3, and their co-staining with markers of different corneal tissues.
Methods :
We obtained twenty human corneas, including 12 normal corneas from body donation and 8 post-surgical corneal buttons from patients with regraft (4), HSV keratitis (1), Fuchs dystrophy (2) and neurotrophic keratitis (1). Optimized immunostaining on flat mounted corneas was employed. Nerves were stained by TUBB3 and/or NF on whole mounted cornea. The connective tissue/vessels, limbus, superficial layer of epithelium, Bowman’s membrane (BM) and stromal structures were respectively stained using antibodies anti a-SAM, CK15, CK12, Laminin 5, and Collagen IV.
Results :
Numerous nerve bundles (NF++, TUBB3+) in connective tissue under the conjunctiva subdivided several times into smaller side branches and entered the connective tissue below the limbus. Most of them penetrated into corneal stroma, and the others continued to the surface of the BM before extending to the centre. Most stromal nerves penetrated the BM and formed the sub-basal nerve plexus at periphery, whereas some stromal nerves penetrated the BM near the centre. The thick sub-basal nerve fibres (NF++, TUBB3++) divided into several thin nerve fibres (NF-, TUBB3++). They converged towards the central cornea to form a clockwise whorl pattern. Numerous nerve endings (NF-, TUBB3++) separated from sub-basal nerve fibres coursed obliquely into the superficial epithelial layer. These findings were consistent in normal fresh corneas but altered in pathological corneas (NF-,TUBB3++ nerves were significantly decreased). This was particularly evident in opaque corneas, with no NF- TUBB3++ nerves in neurotrophic corneal button. We also observed that some stromal cells (NF+) may participate in the maintenance of stromal nerves, and that a few cells (Collagen IV +) protected stromal nerves by forming a collagen tube around them, aiding penetration of the BM.
Conclusions :
This study provides a comprehensive map of the distribution of the differential staining of nerves. The nerves (NF-, TUBB3++) seem crucial in the proper functioning of corneas.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.