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Human intrinsic choroidal neurons do not alter the expression of intrinsic markers in response to pressure
  1. Christian Platzl1,
  2. Alexandra Kaser-Eichberger1,
  3. Heidi Wolfmeier1,
  4. Andrea Trost2,
  5. Falk Schroedl1
  1. 1 Center for Anatomy and Cell Biology, Institute of Anatomy and Cell Biology – Salzburg, Paracelsus Medical University, Salzburg, Austria
  2. 2 University Clinic of Ophthalmology and Optometry, Research Program for Ophthalmology and Glaucoma Research, Paracelsus Medical University, Salzburg, Austria
  1. Correspondence to Professor Falk Schroedl, Institute of Anatomy and Cell Biology- Salzburg, Paracelsus Medical University, Salzburg, Austria; falk.schroedl{at}


Background The choroid is densely innervated by all parts of the autonomic nervous system and further harbours a network of local nerve cells, the intrinsic choroidal neurons (ICN). Their function in ocular control is currently unknown. While morphological data assume a role in intraocular pressure regulation, we here test if increased pressure on isolated choroids may activate ICN.

Methods Donor tissue was transferred into a pressurisable tissue culture chamber, and nasal and temporal choroid halves incubated for 1 or 4 hours, with pressures set to 15 or 50 mm Hg, followed by qRT-PCR expression analysis of the ICN-specific markers VIP, UCN, NOS1, UCH-L1. POL2-normalised data in the different pressure settings, incubation times and localisations were statistically analysed.

Results The presence of the ICN-specific markers VIP, UCN, NOS1, UCH-L1 was confirmed using immunohistochemistry, and mRNA of all markers was detected in all experimental conditions. Marker analysis revealed no significant changes of mRNA expression levels between 15 and 50 mm Hg in the different incubation times. When comparing all samples over all experimental conditions, a significant increase of VIP and NOS1 mRNA was detected in temporal versus nasal choroids.

Conclusion In this functional analysis of human ICN in vitro, higher amounts of VIP and NOS1 mRNA were detected in the temporal choroid, that is, the choroidal site with ICN accumulation. Further, our data indicate that elevated pressure is apparently not able to trigger ICN responses via the investigated markers. Alternative markers and stimuli need to be investigated in upcoming studies in order to unravel ICN function.

  • experimental – laboratory
  • anatomy
  • choroid
  • intraocular pressure
  • pathology

Data availability statement

No data are available. Not applicable.

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Data availability statement

No data are available. Not applicable.

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  • CP and AK-E contributed equally.

  • Correction notice Since this article was first published, the funding statement has been updated.

  • Contributors CP, AK-E, HW, AT and FS (guarantor): Contributed substantial to the conception and design of the work; the acquisition, analysis and interpretation of data for the work; drafting the work and revising it critically for important intellectual content; gave final approval of the work to be published; agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. CP and AK-E contributed equally to this paper.

  • Funding Austrian National Bank Anniversary Fund (17617) and Research Fund of Paracelsus Medical University (PMU-FFF A-18/01/030- SCK).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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