Abstract
Purpose :
The choroid is an important mediator in myopia development and is densely innervated. The gaseous transmitter nitric oxide contributes to choroidal innervation, but is also discussed in regulation of ocular growth. While other gaseous transmitters exist, their role in choroidal modulation is unclear. Therefore, we here investigate the presence of hydrogen sulfide (H2S) in human choroid.
Methods :
Human choroids (body donors/cornea bank Salzburg) were prepared for immunohistochemistry of CBS (cystathionine beta-synthase) or CTH (cystathionine γ-lyase), the key enzymes in H2S-synthesis, and combined with neurofilaments 160/200 (NF), smooth–muscle actin (SMA), TH (tyrosine hydroxylase), and CGRP (calcitonin gene-related peptide). Confocal laser-scanning microscopy was used for documentation.
Results :
CTH was detected in stromal and perivascular nerve fibres, in the vessel wall of choroidal blood vessels, in small cells (10 microns diameter) within the choroidal stroma, and further in intrinsic choroidal neurons (ICN). For CBS, a similar staining pattern was observed. When combining CBS with NF for ICN-identification, ICN were counted and 132/132 ICN were CBS+. Further, CBS and CTH were co-localized in ICN. Stromal nerve fibres co-localized for CBS and CGRP, but not TH. CBS and SMA revealed an overlap in the vessel wall.
Conclusions :
CTH and CBS were detected in neuronal structures with same appearance, thus an involvement of H2S in choroidal neurotransmission is likely. ICN represent an intrinsic source while co-localization with CGRP suggests trigeminal origin; sympathetic fibres (TH) do not utilize H2S. The role of H2S in the vascular wall is not clear, but has been reported in other non-ocular systems. Further studies will clarify the role of H2S in choroidal homeostasis and ocular growth.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.