Differences in Mammalian target of rapamycin gene expression in the peripheral blood and articular cartilages of osteoarthritic patients and disease activity.

Elena M. Zaitseva,A. Robin Poole,Eugeniya P. Sharapova,Maxim A. Makarov,Liudmila A. Semyonova,Svetlana I. Glukhova,Elena V. Tchetina,Natalya G. Kashevarova,Elena A. Taskina,Alexandr N. Kuzin,Sergey A. Makarov,Liudmila I. Alekseeva

doi:10.1155/2013/461486

Abstract

The gene expression of mTOR, autophagy-related ULK1, caspase 3, CDK-inhibitor p21, and TNF α was measured in the peripheral blood of osteoarthritic (OA) patients at different stages of the disease aiming to establish a gene expression profile that might indicate the activity of the disease and joint destruction. Whole blood of 65 OA outpatients, 27 end-stage OA patients, 27 healthy volunteers, and knee articular cartilages of 28 end-stage OA patients and 26 healthy subjects were examined. OA outpatients were subjected to clinical testing, ultrasonography, and radiographic and WOMAC scoring. Protein levels of p70-S6K, p21, and caspase 3 were quantified by ELISA. Gene expression was measured using real-time RT-PCR. Upregulation of mTOR gene expression was observed in PBMCs of 42 OA outpatients (“High mTOR expression subset”) and in PBMCs and articular cartilages of all end-stage OA patients. A positive correlation between mTOR gene expression in PBMCs and cartilage was observed in the end-stage OA patients. 23 OA outpatients in the “Low mTOR expression subset” exhibited significantly lower mTOR gene expression in PBMCs compared to healthy controls. These “Low mTOR” subset subjects experienced significantly more pain upon walking, and standing and increased total joint stiffness versus “High mTOR” subset, while the latter more often exhibited synovitis. The protein concentrations of p70-S6K, p21, and caspase 3 in PBMCs were significantly lower in the “Low” subset versus “High” subset and end-stage subjects. Increases in the expression of mTOR in PBMCs of OA patients are related to disease activity, being associated with synovitis more than with pain.

Highlights

Osteoarthritis (OA) is a systemic condition that can affect single or multiple joints and involves degenerative changes in the articular cartilage, remodeling of the subchondral bone, and limited synovial inflammation [1]
23 OA outpatients in the “Low mTOR expression subset” exhibited significantly lower mTOR gene expression in peripheral blood mononuclear cells (PBMCs) compared to healthy controls
Peripheral blood from the same subsets of OA outpatients was examined for the expression of the autophagy marker Unc-51-like kinase 1 (ULK1), the regulator of cell cycle progression, a cyclin-dependent kinase inhibitor p21, the apoptosis indicator caspase 3, and the proinflammatory cytokine TNFα. These analyses demonstrated that the “Low mTOR expression subset” OA outpatients exhibited significant upregulation of caspase 3 and TNFα genes, while ULK1 and p21 expression remained similar to that in healthy individuals (Figures 1(b)– 1(e))

Summary

Introduction

Osteoarthritis (OA) is a systemic condition that can affect single or multiple joints and involves degenerative changes in the articular cartilage, remodeling of the subchondral bone, and limited synovial inflammation [1]. The disease course is generally monitored by clinical and radiographic changes, which show poor sensitivity. There is a need to identify new approaches in indicating disease activity. Detection of gene expression changes measured in the whole blood is an emerging approach in OA research. Blood-based gene expression patterns recently obtained in transcriptome and microarray analyses appeared capable of distinguishing OA patients from control subjects [2, 3], Arthritis already showing promising results. The level of IL-1β gene expression in peripheral monocytes has been proposed for OA patient stratification, as upregulation of IL1β was accompanied by increased pain and predicted higher risk of radiographic progression of the disease [4]

Methods

Results

Conclusion