Background/Purpose

In rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) that line joint synovial membranes aggressively invade the extracellular matrix, destroying cartilage and bone. Although this cell type mediates RA pathogenesis, it is currently untapped as a drug target. Signal transduction in FLS is mediated through multiple pathways involving protein tyrosine phosphorylation, thus we sought to identify the protein tyrosine phosphatases (PTPs) regulating the aggressiveness of FLS from RA patients (RA FLS). We previously profiled the expression of all PTPs in FLS from RA and osteoarthritis (OA) patients, and found that the PTPN11 gene, encoding the PTP SHP-2, is overexpressed in RA FLS. We also reported that SHP-2 promotes the aggressiveness of RA FLS by enhancing sensitivity of these cells to stimulation by platelet-derived growth factor (PDGF) or tumor necrosis factor (TNF). Here we sought to further explore the role of SHP-2 in mediating pathogenesis of RA.

Methods

Inhibition of SHP-2 enzymatic activity was achieved using a cell-permeable small-molecule chemical inhibitor. FLS migration was assessed in transwell assays in response to 5% fetal bovine serum. Inducible in vivo deletion of Ptpn11 in hematopoietic cells was achieved by breeding Ptpn11 floxed mice with mice expressing Cre recombinase under the Mx1 promoter. Prior to experiments, deletion of the floxed alleles was induced by treating mice with 3 administrations of 300 μg poly(I:C) 2 days apart. In vivo inhibition of SHP-2 activity was achieved by administering mice with 7.5 mg/kg SHP-2 inhibitor once daily. Severity of arthritis in female mice was assessed every 2 days by ankle swelling in the K/BxN passive serum transfer arthritis mouse model following administration of 150 μl arthritogenic serum.

Results

We found that RA FLS migration was reduced 86% upon treatment with 25 μM SHP-2 chemical inhibitor (Median [IQR] % maximum cells per field: 56.58 [41.45-72.37] for vehicle-treated FLS and 7.90 [3.29-15.13] for SHP-2 inhibitor-treated FLS; p<0.0001 by Mann-Whitney test). Using the K/BxN mouse arthritis model, we found that inducible deletion of SHP-2 in hematopoietic cells led to >50% reduction in arthritis severity (Median [IQR] change in ankle thickness after 8 days: 3.62 [3.08-3.78] for Cre^– mice and 0.46 [0.11-1.69] for Cre⁺ mice; p<0.0001 by two-way ANOVA test of 14-day arthritis course). Global inhibition of SHP-2 activity by daily administration of 7.5 mg/kg SHP-2 inhibitor also led to reduced arthritis severity (Median [IQR] change in ankle thickness after 8 days: 2.650 [1.81-3.27] for vehicle-treated mice and 2.14 [0.70-2.73] for inhibitor-treated mice; p<0.01 by two-way ANOVA test for 14-day arthritis course).

Conclusion

These data indicate that SHP-2 promotes the aggressiveness of RA FLS, a role that is dependent on the catalytic activity of the phosphatase. Both global inhibition and inducible deletion of SHP-2 in hematopoietic cells caused a reduction in arthritis severity, suggesting SHP-2 could be a potential target for therapy for RA.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/sh2-domain-containing-phosphatase-2-promotes-aggressiveness-of-rheumatoid-fibroblast-like-synoviocytes/