Faculty Collaboration Database

The serine protease inhibitor trappin-2 is present in cartilage and synovial fluid in osteoarthritis. J Rheumatol 2006 Feb;33(2):318-25

Date

02/09/2006

Pubmed ID

16465664

Scopus ID

2-s2.0-32144440435 (requires institutional sign-in at Scopus site)   11 Citations

Abstract

OBJECTIVE: Trappins are small serine protease inhibitors bound to extracellular matrix (ECM) through the actions of transglutaminase (TGase) enzymes. Trappin-2 is present in many tissues and is upregulated at sites of injury. In osteoarthritis (OA), serine proteases contribute to articular cartilage destruction, and TGase activity is increased. Yet little is known about matrix-bound serine protease inhibitors or TGase substrates in articular cartilage. Our purpose was to determine if trappin-2 was present in OA cartilage and synovial fluid (SF).

METHODS: OA knee articular cartilage and SF were assayed for trappin-2 protein by Western blotting, ELISA, and immunohistochemistry. Trappin-2 mRNA was detected with RT-PCR. The ECM components bound to trappin-2 were identified by 2-D gel electrophoresis and peptide fingerprinting.

RESULTS: Trappin-2 was detectable in OA articular cartilage extracts, cultured chondrocytes, conditioned media, and SF by Western blotting. OA cartilage protein extracts contained significantly higher quantities of trappin-2 than normal cartilage protein extracts (22.98 +/- 1.28 ng/mg wet weight vs 14.97 +/- 1.92 ng/mg wet weight; p < 0.01). RT-PCR confirmed the presence of trappin-2 mRNA in OA chondrocytes. Immunohistochemical studies of OA cartilage revealed trappin-2 protein in chondrocytes. Peptide mapping of trappin-2 binding partners showed that fibromodulin was bound to trappin-2 in cartilage.

CONCLUSION: We confirmed the presence of trappin-2 in OA cartilage and SF. Elevated levels of TGase activity in OA cartilage may increase levels of this serine protease inhibitor in response to injury.

Author List

Jaovisidha K, Etim A, Yamakawa K, Masuda I, Gohr CM, Wakim BT, Boonapatcharoen N, Ninomiya J, Rosenthal AK

Author

Ann K. Rosenthal MD Associate Dean, Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adolescent
Adult
Cartilage, Articular
Cells, Cultured
Chondrocytes
Culture Media, Conditioned
Elafin
Humans
Immunoenzyme Techniques
Leukocyte Elastase
Osteoarthritis
Protein Precursors
RNA, Messenger
Reverse Transcriptase Polymerase Chain Reaction
Synovial Fluid