Corneal fibrosis is a common outcome of inappropriate
repair associated
with trauma or ocular infection. Altered biomechanical properties
with increased corneal stiffness is a feature of fibrosis that cause
corneal opacities, resulting in severe visual impairment and even
blindness. The present study aims to determine the effect of hydroxycamptothecin
(HCPT) and matrix stiffness on transforming growth factor-β1
(TGF-β1)-induced fibrotic processes in human corneal fibroblasts
(HTK cells). HTK cells were cultured on substrates with different
stiffnesses (“soft”, ∼261 kPa; “stiff”,
∼2.5 × 103 kPa) and on tissue culture plastic
(TCP, ∼106 kPa) and simultaneously treated with
or without 1 μg/mL HCPT and 10 ng/mL TGF-β1. We found
that HCPT induced decreased cell viability and antiproliferative effects
on HTK cells. TGF-β1-induced expression of fibrosis-related
genes (FN1, ACTA2) was reduced if
the cells were simultaneously treated with HCPT. Substrate stiffness
did not affect the expression of fibrosis-related genes. The TGF-β1
induced expression of FN1 on both soft and stiff
substrates was reduced if cells were simultaneously treated with HCPT.
However, this trend was not seen for ACTA2, i.e.,
the TGF-β1 induced expression of ACTA2 was
not reduced by simultaneous treatment of HCPT in either soft or stiff
substrate. Instead, HCPT treatment in the presence of TGF-β1
resulted in increased gene expression of keratocyte phenotype makers
(LUM, KERA, AQP1, CHTS6) on both substrate stiffnesses. In addition,
the protein expression of keratocyte phenotype makers LUM and ALDH3
was increased in HTK cells simultaneously treated with TGF-β1
and HCPT on stiff substrate as compared to control, i.e., without
HCPT. In conclusion, we found that HCPT can reduce TGF-β1-induced
fibrosis and promote the keratocyte phenotype in a substrate stiffness
dependent manner. Thus, HCPT stimulation might be an approach to stimulate
keratocytes in the appropriate healing stage to avoid or reverse fibrosis
and achieve more optimal corneal wound healing.