Gene Expression Signatures of Synovial Fluid Multipotent Stromal Cells in Advanced Knee Osteoarthritis and Following Knee Joint Distraction.

Clara Sanjurjo-Rodriguez,Thomas Baboolal,Hemant Pandit,Floris Lafeber,Elena Jones,Dennis Mcgonagle,Tim Welting,Ala Altaie,Simon Mastbergen

doi:10.3389/fbioe.2020.579751

Abstract

Osteoarthritis (OA) is the most common musculoskeletal disorder. Although joint replacement remains the standard of care for knee OA patients, knee joint distraction (KJD), which works by temporarily off-loading the joint for 6–8 weeks, is becoming a novel joint-sparing alternative for younger OA sufferers. The biological mechanisms behind KJD structural improvements remain poorly understood but likely involve joint-resident regenerative cells including multipotent stromal cells (MSCs). In this study, we hypothesized that KJD leads to beneficial cartilage-anabolic and anti-catabolic changes in joint-resident MSCs and investigated gene expression profiles of synovial fluid (SF) MSCs following KJD as compared with baseline. To obtain further insights into the effects of local biomechanics on MSCs present in late OA joints, SF MSC gene expression was studied in a separate OA arthroplasty cohort and compared with subchondral bone (SB) MSCs from medial (more loaded) and lateral (less loaded) femoral condyles from the same joints. In OA arthroplasty cohort (n = 12 patients), SF MSCs expressed lower levels of ossification- and hypotrophy-related genes [bone sialoprotein (IBSP), parathyroid hormone 1 receptor (PTH1R), and runt-related transcription factor 2 (RUNX2)] than did SB MSCs. Interestingly, SF MSCs expressed 5- to 50-fold higher levels of transcripts for classical extracellular matrix turnover molecules matrix metalloproteinase 1 (MMP1), a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), and tissue inhibitor of metalloproteinase-3 (TIMP3), all (p < 0.05) potentially indicating greater cartilage remodeling ability of OA SF MSCs, compared with SB MSCs. In KJD cohort (n = 9 patients), joint off-loading resulted in sustained, significant increase in SF MSC colonies’ sizes and densities and a notable transcript upregulation of key cartilage core protein aggrecan (ACAN) (weeks 3 and 6), as well as reduction in pro-inflammatory C–C motif chemokine ligand 2 (CCL2) expression (weeks 3 and 6). Additionally, early KJD changes (week 3) were marked by significant increases in MSC chondrogenic commitment markers gremlin 1 (GREM1) and growth differentiation factor 5 (GDF5). In combination, our results reveal distinct transcriptomes on joint-resident MSCs from different biomechanical environments and show that 6-week joint off-loading leads to transcriptional changes in SF MSCs that may be beneficial for cartilage regeneration. Biomechanical factors should be certainly considered in the development of novel MSC-based therapies for OA.

Highlights

Multipotent stromal cells (MSCs), originally termed as mesenchymal stem cells, are present in different joint structures including the synovial membrane, synovial fluid (SF), infrapatellar fat pad, ligaments/tendons, and the subchondral bone (SB) (Fellows et al, 2016; McGonagle et al, 2017)
There was no significant difference in the growth rates or surface phenotypes of SF MSC cultures and both types of SB MSCs (Figures 1A,B)
Harnessing endogenous joint repair mechanisms following biomechanical correction of OA joints following Knee joint distraction (KJD) appears to hold particular promise (Mastbergen et al, 2013; McGonagle et al, 2017). While their mechanisms of action remain to be fully elucidated, endogenous SB and SF MSCs have been suggested as potential contributors to structural improvements and cartilage regeneration following these treatments (Chen et al, 2015; Baboolal et al, 2016; Sánchez et al, 2016)

Summary

Introduction

Multipotent stromal cells (MSCs), originally termed as mesenchymal stem cells, are present in different joint structures including the synovial membrane, synovial fluid (SF), infrapatellar fat pad, ligaments/tendons, and the subchondral bone (SB) (Fellows et al, 2016; McGonagle et al, 2017). SF MSCs are a intriguing class of joint-resident MSCs, as unlike other MSCs, they are not attached to other cells or surfaces but instead are suspended in a viscous hyaluronan-rich SF (Jones et al, 2004; Baboolal et al, 2016; Fang et al, 2020) In healthy individuals, they are believed to be shed from the synovial intimal layer or superficial cartilage, as a result of mechanical attrition during joint movement (Jones et al, 2008; Morito et al, 2008; Lee et al, 2012; Matsukura et al, 2014). Combined with their ease of harvesting, despite their limited numbers, they are considered as an attractive MSC source for repairing focal osteochondral defects and potentially, joint regeneration in osteoarthritis (OA), acting via direct differentiation (McGonagle et al, 2017; Piñeiro-Ramil et al, 2017) as well as paracrine mechanisms (Garcia et al, 2016)

Objectives

Methods

Results

Conclusion