Mapping the entire nerve architecture of the cat cornea
Fonte: Jiucheng He, Thang Luong Pham, Haydee E. P. Bazan
Whole‐mount view of epithelial nerves from a quarter of cat cornea. Images were acquired in time‐lapse mode with a 10× objective lens. A, Subbasal nerves; B, highlighted images as framed in (A) show the detailed structures of subbasal nerves and terminals at the vortex (i), center (ii), and periphery zones (iii) of cat cornea
Objective: To provide a complete nerve architecture and neuropeptide distribution in the cat cornea. Animals studied: Two adult domestic cats. Procedure: The cat corneas were stained with protein gene product (PGP) 9.5 antibody—a pan marker for nerve fibers—and then divided into four quarters and double labeled with calcitonin gene‐related peptide (CGRP) or substance P (SP) antibodies. Relative corneal nerve fiber densities and nerve terminals were evaluated in whole mount images by computer‐assisted analysis. Results: An average of 21.5 ± 2.1 thick stromal nerves enters the cornea around the limbus where they split into many branches going up to the anterior stroma. Some branches link to each other, but most of them penetrate the basement membrane in the periphery to give origin to subbasal bundles, which run centripetally and merge to form a whirl‐like structure (vortex) at the center. These nerve bundles send out many fine terminals that innervate the epithelial cells. Subbasal nerve density and nerve terminals were greater in the center than in the periphery of the cornea. Additionally, CGRP‐positive central epithelial nerve fibers and terminals were more abundant than SP‐positive nerves and terminals. Conclusion: The architecture of cat corneal nerves shows similarities to human and mouse cornea innervation. This study provides useful data for researchers who use the cat model to assess corneal nerve pathological alterations, as well as in the veterinary field where corneal opacities, ulcerations, and infections damage the nerves and decrease sensitivity.