Stromal ‘activation’ markers do not confer pathogenic activity in tendinopathy

Crowe, L. A.N., Melchor, E. G., Murrell, G. A.C., McInnes, I. B. , Akbar, M. and Millar, N. (2021) Stromal ‘activation’ markers do not confer pathogenic activity in tendinopathy. Translational Sports Medicine, 4(2), pp. 268-279. (doi: 10.1002/tsm2.204)

Abstract

Tendinopathy is a highly prevalent musculoskeletal pathology associated with incremental injury as result of repetitive microtrauma. We sought to explore the physiological significance of stromal “activation” signatures in a human model of tendinopathy. Torn supraspinatus tendon and matched intact subscapularis tendon biopsies were collected from patients undergoing shoulder surgery while healthy tendon was collected from patients undergoing anterior cruciate ligament (ACL) reconstruction. Expression of stromal activation markers was analyzed at transcript/protein level using qRT‐PCR and immunohistochemistry. Gene expression of stromal activation markers was silenced by siRNA‐mediated knockdown or induced by IL‐1β stimulation. Expression of “activation” markers podoplanin, VCAM‐1 and CD248 was identified in human tendon tissue. Podoplanin and VCAM‐1 expression were significantly increased in tendinopathic tissue. Knockdown of podoplanin and VCAM‐1 in normal and tendinopathic tenocytes did not have any significant effect on expression of matrix genes COL1A1, COL3A1, TNC, or DCN. Similarly, no changes in release of inflammatory mediators IL‐6, IL‐8, and CCL2 were observed in podoplanin/VCAM‐1 knockdown cultures. Our data suggest that silencing expression of stromal “activation” markers does not affect the intrinsic inflammatory profile or matrix regulatory behavior of tenocytes. We propose that the term “activation” is more appropriately reflected by alterations in tenocyte behavior that induce changes in the stromal microenvironment and overall tissue architecture rather than identification through potentially arbitrary phenotypic traits.

• Item Type: Articles
• Additional Information: This work was funded by the Medical Research Council (MR/R020515/1).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: McInnes, Professor Iain and Akbar, Mr Moeed and Crowe, Ms Lindsay and Millar, Professor Neal
• Authors: Crowe, L. A.N., Melchor, E. G., Murrell, G. A.C., McInnes, I. B., Akbar, M., and Millar, N.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Research Centre: College of Medical Veterinary and Life Sciences > School of Infection & Immunity > Centre for Immunobiology
• Journal Name: Translational Sports Medicine
• Publisher: Wiley
• ISSN: 2573-8488
• ISSN (Online): 2573-8488
• Published Online: 30 September 2020
• Copyright Holders: Copyright © 2020 The Authors
• First Published: First published in Translational Sports Medicine 4(2):268-279
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
301515		Damage mechanisms in tendon disease	Neal Millar	Medical Research Council (MRC)	MR/R020515/1	III - Immunology