Therapeutic effects of adenoviral gene transfer of bone morphogenic protein-7 on a corneal alkali injury model in mice

Abstract

An alkali burn in the cornea is a common serious clinical problem often leading to permanent visual impairment. Since transforming growth factor-b (TGF-b) is involved in the response to corneal injury, we evaluated the therapeutic effects of adenoviral gene transfer of mouse bone morphogenic proten-7 (BMP-7), which has antagonistic effects on TGF-b in tissue fibrosis. Burned cornea did not express endogenous BMP-7 mRNA and protein. Resurfacing of the burned cornea by invading conjunctival epithelium was accelerated by adenoviral introduction of BMP-7. Exogenous BMP-7 expression also suppressed myofibroblast generation, appearance of monocytes/macrophages and expression of MCP-1, TGF-bs, and collagen I a2 chain in the affected stroma. Ectopic BMP-7 did not suppress stromal neovascularization throughout the interval studied and also did not reduce VEGF mRNA expression at Day 10. Ectopic BMP-7 in burned corneal tissue resulted in activation of Smad1/5/8 signaling and partial suppression of the phospho-Smad2 signal. These data suggest that overexpression of BMP-7 is an effective strategy for treatment of ocular alkali burns.

Corneal Antifibrotic Switch Identified in Genetic and Pharmacological Deficiency of Vimentin

“…On the other hand, the reduction of TGF-␤, a profibrogenic stimulus for myofibroblast differentiation, in Vim Ϫ/Ϫ mice and in WFA-treated Vim ϩ/ϩ mice points to a suppression of a fibrotic switch elicited in genetic and pharmacological deficiency of vimentin. That direct blockade of TGF-␤ (39) or antagonizing its signaling mechanism in corneal cells (77) inhibits ␣-SMA expression in corneal stroma and restores corneal clarity in alkali injured mice further supports the idea that this cytokine is relevant to therapeutic strategies being considered for treatment of corneal fibrotic disorders (37). In this respect, the regulatory control of TGF-␤ biogenesis and its activity is associated with mechanical forces exerted by stromal myofibroblasts on the extracellular matrix that facilitates a positive feedback loop, where mechanical tension in the stroma promotes and sustains the myofibroblast phenotype through activation of ␣-SMA expression (78).…”

TGFβ pathobiology in the eye

“…We have shown that gene introduction of BMP-7 also has a therapeutic effect on an alkali burn in mice, although its efficacy is less than that of Smad7. 109 Unlike in an alkali-burned cornea, Stevens-Johnson's syndrome is an inflammatory ocular surface disease caused by an autoimmune mechanism. Nevertheless, the main component of the disease consists of inflammation and scarring that are similar to those seen in a burned eye.…”

Loss of Tumor Necrosis Factor α Potentiates Transforming Growth Factor β-mediated Pathogenic Tissue Response during Wound Healing

“…16 Real-time RT-PCR for mRNAs of mouse TGF␤1, monocyte/macrophage-chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF), and collagen I␣2 was performed at weeks 1, 2, and 4 using primers and probes shown in Table 1 as previously reported.…”

“…16,17 Ofloxacin ointment was topically administered twice a week in the first 2 weeks and then once a week until week 8 to reduce the risk of bacterial contamination. The eyes with obvious bacterial infection were excluded from the study.…”

“…The burned corneas of 12 KO and 12 WT mice were obtained at weeks 1, 2, and 4 after burn and processed for RNA extraction and real-time RT-PCR as previously reported. 16,17 Four uninjured corneas of two KO and two WT mice were included to obtain the basal expression level of each cytokine.…”