Effect of Thyroxine on Transforming Growth Factor β1, Collagen I, and V Expression in Keratoconus Corneal Fibroblasts and Keratocytes, in Vitro

ABSTRACT

Background

Keratoconus (KC) is a corneal disorder, associated with oxidative stress, hypoxia and as several times discussed, potentially with thyroid gland dysfunction. We aimed to investigate the effect of thyroxine on transforming growth factor β1 (TGF-β1), collagen I and V (Col I and V) expression in human corneal fibroblasts (HCFs) and human keratocytes of KC corneas, in vitro.

Methods

Primary human KC-keratocytes and normal keratocytes were isolated and cultured as corneal fibroblasts or keratocytes. The effect of 0.1 µg/ml and 1.0 µg/ml thyroxine on TGF-β1, Col I and Col V expression was investigated by qPCR, Western blot, and ELISA. Proliferation assay was performed using BrdU ELISA to observe the 24h effect of 1.0 µg/ml thyroxine on keratocytes, in vitro.

Results

TGFB1 mRNA expression of normal keratocytes increased following 1.0 µg/ml thyroxine stimulation for 24 h (p = .036), without changes in protein expression. Col I protein expression of KC-HCFs increased following 1.0 µg/ml thyroxine stimulation for 24 h (p = .0003). Proliferation of normal and KC keratocytes increased following a 7-day growth period and 24 hours thyroxine administration (p = .018; p = .024).

Conclusions

Thyroxine may affect the Col I protein expression in KC-HCFs, but not in KC keratocytes, in vitro. Thyroxine administration has no effect on TGF-β1, collagen I and V expression of keratoconus keratocytes. Therefore, an increased thyroxine concentration alone seems not to be causally related to the development of keratoconus.

KEYWORDS:

• Keratoconus
• thyroxine
• TGF-β1
• collagen I
• collagen V

Acknowledgments

We would like to thank Prof. Dr. Veit Flockerzi (Department of Experimental and Clinical Pharmacology, Institute of Experimental and Clinical Pharmacology and Toxicology, Center for Molecular Signaling (PZMS), Saarland University, Homburg, Germany) for the use of the Western blot visualization. The work of Dr. Stachon, Dr. Latta and Dr. Szentmáry at the Dr. Rolf M. Schwiete Center for Limbal Stem Cell and Congenital Aniridia Research was supported by the Dr. Rolf M. Schwiete Foundation.

Availability of data and materials

The data used to support the findings of this study are available from the corresponding author upon request.

Consent to publish

All authors declare their consent to publish.

Disclosure statement

The authors declare that they have no competing interests.

Ethics approval and consent to participate

This study was performed in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Saarland/Germany (No 263/15) and informed consent was obtained from all participants with KC, before keratoplasty was performed.

Additional information

Funding

No funding was received by any of the authors for the writing of this manuscript.