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

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.

• Authors: Florent Eymard, Audrey Pigenet, Danièle Citadelle, Joan Tordjman, Louise Foucher, Cindy Rose, Charles-Henri Flouzat Lachaniette, Christine Rouault, Karine Clément, Francis Berenbaum, Xavier Chevalier, Xavier Houard
• Journal: Annals of the rheumatic diseases (Ann Rheum Dis) Vol. 76 Issue 6 Pg. 1142-1148 (Jun 2017) ISSN: 1468-2060 [Electronic] England
• PMID: 28298375 (Publication Type: Comparative Study, Journal Article)
• Copyright: Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Chemical References

• CD36 Antigens
• Culture Media, Conditioned
• EN1 protein, human
• FABP4 protein, human
• Fatty Acid-Binding Proteins
• Homeodomain Proteins
• Hoxc9 protein, human
• Interleukin-6
• Interleukin-8
• Membrane Proteins
• PPAR gamma
• RNA, Messenger
• SFRP2 protein, human
• Lipase
• PNPLA2 protein, human
• LPL protein, human
• Lipoprotein Lipase
• Dinoprostone

Topics

• Adipocytes (metabolism, pathology)
• Adipose Tissue (metabolism, pathology)
• Adolescent
• Adult
• Aged
• CD36 Antigens (genetics)
• Culture Media, Conditioned (pharmacology)
• Dinoprostone (metabolism)
• Fatty Acid-Binding Proteins (genetics)
• Female
• Gene Expression
• Hip Joint
• Homeodomain Proteins (genetics)
• Humans
• Interleukin-6 (metabolism)
• Interleukin-8 (metabolism)
• Knee Joint
• Lipase (genetics)
• Lipoprotein Lipase (genetics)
• Male
• Membrane Proteins (genetics)
• Middle Aged
• Osteoarthritis, Hip (genetics, metabolism)
• Osteoarthritis, Knee (genetics, metabolism)
• PPAR gamma (genetics)
• Phenotype
• RNA, Messenger (metabolism)
• Subcutaneous Fat (metabolism, pathology)
• Synoviocytes (drug effects)
• Young Adult