Background/Purpose: Scleroderma is a progressive fibrotic multi-organ disease characterized by the hardening and tightening of the skin and connective tissues. TGF-β1 is a potent mediator of fibroblast to myofibroblast transition (FMT), which contributes to increased extracellular matrix deposition and is the main driver of disease. There is substantial evidence for crosstalk between αV integrins and TGF-β during these processes. TGF-β is secreted in a latent form which contains a Latency Associated Peptide (LAP) region. The LAP of TGF-β1 contains an Arg-Gly-Asp (RGD) motif, which interacts with the integrins αVβ1, αVβ3, αVβ5, αVβ6 and αVβ8 resulting in activation of TGF-β1. Abituzumab is a human antibody specific for αV and therefore inhibits ligand binding of these five integrins. The goal of this study was to determine if abituzumab can block TGF-β activation and FMT in vitro and thus have potential as a scleroderma therapeutic.

Methods: Expression of integrins and myofibroblast markers in human lung fibroblasts was analyzed by RT-PCR in the presence and absence of abituzumab. In addition, we examined the ability of abituzumab to block FMT in an epithelial cell (NCI-H358 or Calu3)/fibroblast co-culture, mimicking the potential interaction of epithelial cells and fibroblasts in tissues undergoing fibrosis.

Results: Analysis of integrin expression showed that human lung fibroblasts express ITGB1>ITGB5>ITGB8>ITGB3. TGF-β-induced FMT caused an increase in the expression of ITGB5, and to a lesser extent ITGB1 and ITGB3. TGF-β treatment increased myofibroblast marker genes in lung fibroblasts, and immunofluorescence staining revealed increased αVβ5 and a-SMA expression. Abituzumab treatment of fibroblast cultures showed a reduction in the increased αSMA expression, as well as production of IL-6 and collagen gel contraction, demonstrating an ability for abituzumab to block TGF-β-induced FMT. Co-culture of epithelial cells with fibroblasts resulted in induction of αSMA and multiple mRNA transcripts that are markers for FMT, as well as increased IL-6 production. In this system, these markers were reduced by abituzumab treatment, demonstrating that αV integrins play a role in FMT.

Conclusion: Results reported here indicate abituzumab has the potential to block TGF-β-induced FMT and thus development of fibrosis. It may potentially be an efficacious drug for treatment of scleroderma.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-%ce%b1v-integrin-inhibitor-abituzumab-inhibits-myofibroblast-differentiation/