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Knee and hip intra-articular adipose tissues (IAATs) compared with autologous subcutaneous adipose tissue: a specific phenotype for a central player in osteoarthritis
  1. Florent Eymard1,2,
  2. Audrey Pigenet1,
  3. Danièle Citadelle1,
  4. Joan Tordjman3,4,
  5. Louise Foucher1,
  6. Cindy Rose1,
  7. Charles-Henri Flouzat Lachaniette5,
  8. Christine Rouault3,4,
  9. Karine Clément3,4,
  10. Francis Berenbaum1,2,6,
  11. Xavier Chevalier2,
  12. Xavier Houard1
  1. 1INSERM, Sorbonne University, UPMC Univ Paris 06, Centre de Recherche Saint-Antoine (CRSA), Paris, France
  2. 2Department of Rheumatology, AP-HP Henri Mondor Hospital, Créteil Cedex, France
  3. 3INSERM UMR_S1166, Sorbonne University, UPMC Univ Paris 06, Pitié-Salpêtrière Hospital, Paris, France
  4. 4Institute of Cardiometabolism and Nutrition, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Paris, France
  5. 5Department of Orthopedic Surgery, AP-HP Henri Mondor Hospital, Créteil Cedex, France
  6. 6Department of Rheumatology, Inflammation–Immunopathology–Biotherapy Department (DHU i2B), AP-HP Saint-Antoine Hospital, Paris, France
  1. Correspondence to Dr Francis Berenbaum, INSERM UMR-S 938, “Metabolism and Age-Related Joint Diseases”, Saint Antoine Research Center, 27 rue Chaligny, F-75571 Cedex 12, Paris, France; francis.berenbaum{at}aphp.fr

Abstract

Objectives Compared with subcutaneous adipose tissue (SCAT), infrapatellar fat pad (IFP), the main knee intra-articular adipose tissue (IAAT), has an inflammatory phenotype in patients with osteoarthritis (OA). We phenotyped suprapatellar fat pad (SPFP) and hip acetabular fat pad (AFP), two other IAATs, to determinate the unique signature of IAATs compared with SCAT.

Methods IFP, SPFP, AFP and autologous SCAT were obtained from patients with OA during total knee (n=38) or hip replacement (n=5). Fibrosis and adipocyte area were analysed by histology and vascularisation, leucocyte and mast cell infiltration were analysed by immunohistochemistry for von Willebrand factor, leucocytes and tryptase, respectively. Secretion of interleukin (IL)-6, IL-8 and prostaglandin E2 (PGE2) was assessed by ELISA. The mRNA expression of adipocyte-associated genes (ATGL, LPL, PPAR-γ, FABP4 and CD36) and developmental genes (SFRP2, HoxC9 and EN1) was determined. The inflammatory response of isolated fibroblast-like synoviocytes (FLS) to autologous IFP and SPFP conditioned media was examined.

Results Fibrosis, vascularisation and leucocyte and mast cell infiltration were greater in IAATs than SCAT, and levels of IL-6, IL-8 and PGE2 were greater in all IAATs than SCAT. IFP and SPFP induced a similar inflammatory response to FLS. Adipocyte area was smaller in IAATs than SCAT. Adipocyte-associated and developmental genes showed a similar gene expression pattern in all IAATs, different from SCAT.

Conclusions IFP but also SPFP and AFP (gathered under the term ‘IAAT’) may play a deleterious role in OA by affecting joint homeostasis because of their inflammatory phenotype and their close interaction with synovium in the same functional unit.

  • Osteoarthritis
  • Inflammation
  • Synovitis

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Footnotes

  • Handling editor Tore K Kvien

  • Contributors Study design: FE, FB and XH. Data acquisition: FE, AP, DC, JT, LF, CRose, CRouault and C-HFL. Data analysis: FE, AP, DC, KC and XH. Statistical analysis: FE and XH. Manuscript preparation: FE, XH and XC. All authors have critically reviewed the manuscript.

  • Funding The authors thank the “Société Française de Rhumatologie” for financial support.

  • Competing interests None.

  • Patient consent Obtained.

  • Ethics approval The study was approved by the ethics committee of Henri Mondor Hospital and by the Assistance Publique Hôpitaux de Paris (approval no. 07-34) for biological sample collection.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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