Beneficial Effects of Hypercapnic Acidosis on the Inhibition of Transforming Growth Factor β-1-induced Corneal Fibrosis in Vitro

ABSTRACT

Purpose

Corneal scarring is a common poor outcome of corneal trauma. Transforming growth factor β-1 plays a vital role in corneal fibrosis, inducing keratocyte transformation to myofibroblasts. Other than corneal transplantation, no other curative treatment methods for corneal scarring are currently available. Hypercapnic acidosis exerts anti-inflammatory and anti-migratory effects on numerous organs; however, its effect on corneal fibroblasts remains unknown. Hence, this study aimed to evaluate the effect of hypercapnic acidosis on transforming growth factor β-1-induced fibrosis in corneal fibroblasts and to elucidate the underlying mechanisms.

Materials and Methods

Corneal fibroblasts were obtained from human limbal tissue and cultured with or without transforming growth factor β-1 under hypercapnic acidosis or no-hypercapnic acidosis conditions, and subjected to scratch wound, cell migration, and collagen matrix contraction assays. Furthermore, immunocytochemistry was performed to evaluate the alpha-smooth muscle actin stress fiber. Finally, western blotting was performed to assess the expression of proteins in the NF-κB and Smad pathways.

Results

Hypercapnic acidosis suppressed collagen gel contraction capacity in transforming growth factor β-1-treated corneal fibroblasts and inhibited transforming growth factor β-1-induced cell migration. Moreover, hypercapnic acidosis downregulated corneal fibrosis marker alpha-smooth muscle actin in transforming growth factor β-1-treated corneal fibroblasts. Furthermore, hypercapnic acidosis suppressed transforming growth factor β-1-induced fibrosis, at least partly, by inhibiting Smad2/3 phosphorylation and down-regulating p-IκB-dependent and RelB signaling transduction.

Conclusions

Hypercapnic acidosis inhibits transforming growth factor β-1-induced corneal fibroblast migration, collagen gel contraction capacity, and alpha smooth muscle actin expression, potentially through the Smad and NF-κB pathways. Therefore, hypercapnic acidosis may be a potentially useful anti-fibrotic therapy for corneal scarring.

KEYWORDS:

• Corneal scarring
• transforming growth factor β-1
• hypercapnic acidosis
• nuclear factor-κB
• in vitro

Acknowledgments

We thank the staff at the Department of Ophthalmology, TSGH and National Defense Medical Center.

Declaration of interest

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported in part by grants from the Tri-Service General Hospital [TSGH-C108-220 and TSGH-C108-121] and the Ministry of Science and Technology [MOST 107-2314-B-016-035], Taiwan, ROC.