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Ann Rheum Dis. 2017 Jun;76(6):1142-1148. doi: 10.1136/annrheumdis-2016-210478. Epub 2017 Mar 15.

Knee and hip intra-articular adipose tissues (IAATs) compared with autologous subcutaneous adipose tissue: a specific phenotype for a central player in osteoarthritis.

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INSERM, Sorbonne University, UPMC Univ Paris 06, Centre de Recherche Saint-Antoine (CRSA), Paris, France.
Department of Rheumatology, AP-HP Henri Mondor Hospital, Créteil Cedex, France.
INSERM UMR_S1166, Sorbonne University, UPMC Univ Paris 06, Pitié-Salpêtrière Hospital, Paris, France.
Institute of Cardiometabolism and Nutrition, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, Paris, France.
Department of Orthopedic Surgery, AP-HP Henri Mondor Hospital, Créteil Cedex, France.
Department of Rheumatology, Inflammation-Immunopathology-Biotherapy Department (DHU i2B), AP-HP Saint-Antoine Hospital, Paris, France.



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.


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.


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.


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.


Inflammation; Osteoarthritis; Synovitis

[Indexed for MEDLINE]

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