ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 2231

The Actin-Crosslinking Protein Lasp-1 Regulates Synovial Fibroblast Migration and Cartilage Destruction In Arthritis

Denise Beckmann1, Jan Hillen2, Marianne Heitzmann2, Catherine S. Chew3, Stefan Butz4, Dietmar Vestweber5, Hermann Pavenstädt6, Thomas Pap7 and Adelheid Korb-Pap2, 11nstitute of Experimental Musculoskeletal Medicine, University Hospital Muenster, Muenster, Germany, 2Institute of Experimental Muskuloskeletal Medicine, University Hospital Muenster, Muenster, Germany, 3Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA, 4Max Planck Institute of Molecular Biomedicine, Max Planck Institute of Molecular Biomedicine, Muenster, Germany, 5Max Planck Institute of Molecular Biomedicine, Muenster, Germany, 6Internal Medicine D, Department of Nephrology and Rheumatology, University Hospital Muenster, Muenster, Germany, 7Institute of Experimental Muskuloskeletal Medicine, University Hospital Münster, Münster, Germany

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords:

Session Information

Title: Rheumatoid Arthritis - Animal Models II

Session Type: Abstract Submissions (ACR)

Background/Purpose: Lasp-1 localizes at focal adhesions along stress fibres and leading edges of migrating cells and regulates the metastatic dissemination of tumors. Although rheumatoid arthritis synovial fibroblasts (RASF) have been shown to contribute to the spreading of disease by leaving cartilage destruction sites, migrating via the bloodstream and re-initiating the destructive process at distant articular cartilage surfaces, the underlying mechanisms are not yet understood. Therefore, we investigated the role of Lasp-1 in SF migration and in a mouse model of RA.

Methods: We used Western blot analyses and immunofluorescence stainings of cells grown on different extracellular matrices (ECM) including fibronectin, laminin and in vitro reconstituted cartilage collagen fibrils to study the expression of Lasp-1 and its sub-cellular distribution in RASF as well as in SF isolated from the hind paws of wild type (wt) and human TNFalpha transgenic (hTNFtg) mice, an established animal model of human RA. To investigate the effects of a Lasp-1 deficiency on RA-like arthritis in vivo, we interbred Lasp-1-/- mice with hTNFtg mice. Wt, Lasp-1-/-, hTNFtg and Lasp-1-/-/hTNFtg mice were scored for clinical parameters such as paw swelling, grip strength and weight once weekly for 14 weeks. Hind paws of 14 weeks old mice of all genotypes were harvested, embedded into paraffin, and tissue sections were stained with toluidin-blue and analyzed using AxioVision software. The migration characteristics of SF derived from all genotypes were studied in a modified scratch assay as well as in live cell imaging studies.

Results: Western blot analyses showed a significantly increased expression of Lasp-1 in RASF and in hTNFtg SF compared to healthy and wt controls. Using immunofluorescence, Lasp-1 was localized to structures of cell adhesion and invasion especially when in vitro reconstituted cartilage collagen fibrils were used as ECM. Quantification of scratch assay data showed a significantly reduced migration of Lasp-1-/- SF compared to wt cells (-43.7%, p<0.05) and even more prominently of Lasp-1-/-/hTNFtg SF compared to hTNFtg cells (-69.11%, p<0.05). Live cell imaging demonstrated striking differences both in the migration velocity and in migration edge formation of Lasp-1-/-/hTNFtg SF compared to hTNFtg SF in vitro. Lasp-1-/-/hTNFtg mice presented milder clinical symptoms compared to hTNFtg animals in vivo. Histopathologic analyses showed less cartilage damage in Lasp-1-/-/hTNFtg compared to hTNFtg mice (5.2% vs. 33.6%, p<0.05) and attachment of synovial tissue to the cartilage (0.4 µm vs. 1.4µm, p<0.05) at an age of 14 weeks.

Conclusion: We conclude that Lasp-1 modulates SF migration and influences cartilage degradation and SF attachment to cartilage in hTNFtg mice. SF – when activated – migrate through the formation of invasive and adhesive membrane structures, where Lasp-1 is prominently localized. Thus, targeting Lasp-1 may be a promising strategy to reduce the invasive and migratory behaviour of RASF.

Disclosure:

D. Beckmann,
None;

J. Hillen,
None;

M. Heitzmann,
None;

C. S. Chew,
None;

S. Butz,
None;

D. Vestweber,
None;

H. Pavenstädt,
None;

T. Pap,
None;

A. Korb-Pap,
None.

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