Bilateral Effect of the Unilateral Corneal Nerve Cut on Both Ocular Surface and Lacrimal Gland

Abstract

PURPOSE. This study investigated the effect of a unilateral cut of the corneal nerve on the bilateral ocular surface and tear secretory function. METHODS. Seven-week-old female BALB/c mice were divided into control and nerve-cutting (NC) groups (n ¼ 60). The left cornea was partially incised with a 2-mm circular trephine through the upper half of the stromal layer. Lissamine green corneal staining and tear volume measurements were conducted, and corneal whole-mount staining using class III b-tubulin antibody was performed to assess corneal nerves. Flow cytometric analyses for dendritic cells (DCs), CD4 þ /CD8 þ and regulatory T cells and ELISA for neuropeptides were performed. RESULTS. The grading of corneal staining increased in the NC group, while the tear volume decreased over the 4 weeks. The nerve density decreased in bilateral corneas over 2 weeks. At day 14, CD11b þ or CD11c þ DCs and the mature DCs expressing CD86 or MHCII increased in bilateral cornea/conjunctiva. At day 28, CD11c þ CD86 hi , CD11c þ MHCII hi , Th17 and IFN-csecreting CD8þ T cells highly increased in bilateral draining lymph nodes. CD4 þ CD25 hi Fox-p3 hi and CD8 þ CD25 hi Foxp3 hi regulatory T cells notably increased in the spleen. In ELISA, neuropeptide Y, calcitonin gene-related peptide, and vasoactive intestinal peptide were generally suppressed in the extraorbital lacrimal glands at day14. CONCLUSIONS. The unilateral corneal nerve severing resulted in activation of the immune cells on the ocular surface and dysregulated lacrimal secretion bilaterally through the bidirectional neuronal signals. It suggests that the unilateral corneal nerve damage may alter immune homeostasis and mechanistically participate in the development of bilateral inflammatory disorders such as dry eye.

Morphological and Functional Changes of Corneal Nerves and Their Contribution to Peripheral and Central Sensory Abnormalities

“…There is also a wealth of evidence to show that contralateral structural and molecular changes can occur both in the periphery and the central nervous system in response to a unilateral insult (Koltzenburg et al, 1999;Shenker et al, 2003;Ferrari et al, 2014;Lee et al, 2019).…”

“…For example, unilateral corneal damage induces inflammatory responses in contralateral mouse eyes (Yamaguchi et al, 2016;Lee et al, 2019), the TG (Ferrari et al, 2014), and the central nervous system (Launay et al, 2016). Indeed, FOS-like positive neurons were seen in the contralateral trigeminal brainstem after corneal nerve damage (Launay et al, 2016).…”

Comparative Analysis of Age-Related Changes in Lacrimal Glands and Meibomian Glands of a C57BL/6 Male Mouse Model

“…For MG analysis, upper and lower samples of each eye were pooled (8W, n = 9; 1Y, n = 5; 2Y, n = 3). The proportion of IFN-γ and IL-17A in CD4 + and CD8 + T cells was assessed as a subset of effector T cells in the LGs and DLNs [48].…”

Lacrimal gland excision in male and female mice causes ocular pain and anxiety-like behaviors

“…Previous studies have shown that unilateral corneal injury can produce bilateral effects on corneal innervation, immune cells, and cytokines 34 – 36 . For example, 14 days after unilateral trephine-induced corneal nerve injury, a contralateral reduction in stromal and sub-basal nerve innervation was found, along with bilateral ocular inflammation 36 . Corneal sensitivity in these studies, however, was not assessed.…”