Targeted AAV5-Smad7 gene therapy inhibits corneal scarring in vivo

Abstract

Corneal scarring is due to aberrant activity of the transforming growth factor β (TGFβ) signaling pathway following traumatic, mechanical, infectious, or surgical injury. Altered TGFβ signaling cascade leads to downstream Smad (Suppressor of mothers against decapentaplegic) protein-mediated signaling events that regulate expression of extracellular matrix and myogenic proteins. These events lead to transdifferentiation of keratocytes into myofibroblasts through fibroblasts and often results in permanent corneal scarring. Hence, therapeutic targets that reduce transdifferentiation of fibroblasts into myofibroblasts may provide a clinically relevant approach to treat corneal fibrosis and improve long-term visual outcomes. Smad7 protein regulates the functional effects of TGFβ signaling during corneal wound healing. We tested that targeted delivery of Smad7 using recombinant adeno-associated virus serotype 5 (AAV5-Smad7) delivered to the corneal stroma can inhibit corneal haze post photorefractive keratectomy (PRK) in vivo in a rabbit corneal injury model. We demonstrate that a single topical application of AAV5-Smad7 in rabbit cornea post-PRK led to a significant decrease in corneal haze and corneal fibrosis. Further, histopathology revealed lack of immune cell infiltration following AAV5-Smad7 gene transfer into the corneal stroma. Our data demonstrates that AAV5-Smad7 gene therapy is relatively safe with significant potential for the treatment of corneal disease currently resulting in fibrosis and impaired vision.

Novel Combination BMP7 and HGF Gene Therapy Instigates Selective Myofibroblast Apoptosis and Reduces Corneal Haze In Vivo

“…On the other hand, BMP7 is well known to antagonize the TGF-β pathway 15 , 17 via upregulation of the Id3 proteins 59 and Smad 7 signaling. 60 Coadministration of BMP7 and HGF has been found therapeutic in renal fibrosis and tubular nephropathy. 61 Expression of profibrotic factors such as α-SMA , fibronectin, and collagens has been shown to decrease in response to BMP7 treatment.…”

Myofibroblast transdifferentiation: The dark force in ocular wound healing and fibrosis

“…Overexpression of a specific fibril collagenase, MMP14, by a single intrastromal injection of MMP14 viral vector also prevented collagen deposition and subsequent scarring with reduced mRNA expression of two key gene markers of corneal fibrosis, α-SMA and type III collagen (Galiacy et al, 2011). In a rabbit corneal injury model, adenoviral-mediated targeted delivery of Smad7 to the corneal stroma also inhibited TGFβ1-induced myofibroblastic transdifferentiation (significant reduction in α-SMA levels), as well as corneal haze and fibrosis post-PRK (Gupta et al, 2017). More recently, treatment with cationic nanoparticles encapsulating a combination of silencing RNAs (siRNAs) targeting TGFβ1, type II TGFβ receptor and connective tissue growth factor (CTGF) significantly reduced the levels of α-SMA expression and scar formation in an organ culture model of excimer ablated rabbit corneas (Sriram et al, 2014).…”

“…In particular, Smad7 gene therapy has been found to be efficacious in corneal stromal fibrosis (Gupta et al, 2017), endothelial wound healing (Sumioka et al, 2008), injury-induced lens fibrosis (Saika et al, 2004c) and EMT of RPE cells (Saika et al, 2007). BMPs and their downstream target genes, Id, have shown promise in antagonizing TGFβ-induced corneal stromal injury (Saika et al, 2005; Tandon et al, 2013; Mohan et al, 2016), EMT of lens epithelial cells (Kowanetz et al, 2004; Saika et al, 2006; Shu et al, 2017) and myofibroblast transdifferentiation of TM cells (Wordinger et al, 2007; Fuchshofer et al, 2009; Mody et al, 2017).…”

KCa3.1 ion channel: A novel therapeutic target for corneal fibrosis

“…The TGFβ1 signaling proteins are key regulators of fibroblast differentiation to myofibroblasts which represents a major pathway in tissue fibrosis. Great efforts are under way in corneal research to understand the mechanisms of corneal fibrosis and identify pharmacological molecules [ 19 ], nanoparticles [ 9 , 17 ], or gene therapy approaches [ 16 , 18 ] to counterbalance TGFβ1 mediated pro-fibrotic function as a means of decreasing the myofibroblast population in injury-induced corneal fibrosis. The accumulating literature suggests that TRAM-34 significantly inhibits pro-fibrotic gene and protein expression by antagonizing TGFβ1 mediated downstream signaling, corroborating that KCa3.1 contributes to TGFβ1-driven fibrosis.…”