Obesity does not affect the size of infrapatellar fat pad adipocytes: implications for the pathogenesis of knee osteoarthritis

Garcia, J.; Wei, W.; Runhaar, J.; Wright, K.; Mennan, C.; Roberts, S.; Van Osch, G.; Bastiaansen-Jenniskens, Y.

Abstract

Purpose: Obesity is known to be a risk factor for the development of osteoarthritis (OA). Obesity is accompanied by adipocyte hypertrophy and elevated inflammation in subcutaneous and visceral adipose tissue. The infrapatellar fat pad (IPFP) is an adipose tissue that contains adipocytes. The IPFP is believed to be influential in determining the inflammatory state of the knee. However, little is known whether obesity influences adipocytes in the IPFP. The aim of this exploratory study was to determine whether obesity influences the size of the adipocytes, as a measure of their inflammatory activity, in the IPFP.

Methods: IPFP was obtained from 18 patients undergoing knee arthroplasties with a mean body mass index (BMI) of 29.7 kg/m2 (range 21.5–48.47 kg/m2). Subcutaneous fat was obtained from 12 donors undergoing total hip or knee replacement with a mean BMI of 33.0 kg/m2 (range 24.2–48.5 kg/m2). Fat tissues were cryosectioned and stained with haematoxylin and eosin and imaged at x100 magnification. To determine the size of the adipocytes, the cross-sectional area of the imaged adipocytes was calculated using Fiji Is Just ImageJ software with the additional Adiposoft plugin. Three separate sections, with a minimum of 25 adipocytes in each section were measured per donor. The Shapiro-Wilk test was conducted to assess the distribution of the adipocyte sizes for each donor and a Kruskal-Wallis with multiple comparisons was used to compare adipocyte sizes between groups. Spearman’s rho was determined to relate BMI to adipocyte size in IPFP and subcutaneous fat.

Results: The adipocyte sizes for each individual donor were not normally distributed. Median subcutaneous adipocyte size positively correlates with donor BMI (r=0.63, p=0.028), however this relationship was not observed in IPFP adipocytes (r= −0.06, p=0.82). For non-obese donors (BMI &lt 0.99). In obese donors (BMI &gt 30) on the other hand, subcutaneous adipocytes were significantly larger than the adipocytes in the IPFP (p=0002).

Conclusions: In contrast to subcutaneous adipose tissue, obesity does not affect the size of adipocytes in the IPFP. Previous reports have shown that adipocyte hypertrophy is directly linked to a higher secretion of pro-inflammatory cytokines and the recruitment of pro-inflammatory macrophages. Our results may highlight the functional differences between these two adipose tissues. In the context of obesity and OA, our data suggests that adipocytes in the IPFP are not responsible for obesity related joint environment changes. Further investigations are necessary to determine whether IPFP adipocyte secretion pattern is influenced by BMI.

Citation

Garcia, J., Wei, W., Runhaar, J., Wright, K., Mennan, C., Roberts, S., …Bastiaansen-Jenniskens, Y. (2016). Obesity does not affect the size of infrapatellar fat pad adipocytes: implications for the pathogenesis of knee osteoarthritis. Osteoarthritis and Cartilage, 24(S1), S334-S335. https://doi.org/10.1016/j.joca.2016.01.599

• Journal Article Type: Conference Paper
• Conference Name: 2016 OARSI World Congress on Osteoarthritis; 31 March-3 April 2016
• Conference Location: Amsterdam, The Netherlands
• Online Publication Date: Mar 20, 2016
• Publication Date: 2016-04
• Deposit Date: Jun 12, 2023
• Journal: Osteoarthritis and Cartilage
• Print ISSN: 1063-4584
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 24
• Issue: S1
• Pages: S334-S335
• DOI: https://doi.org/10.1016/j.joca.2016.01.599
• Keywords: Orthopedics and Sports Medicine; Biomedical Engineering; Rheumatology