Gene expression and functional comparison between multipotential stromal cells from lateral and medial condyles of knee osteoarthritis patients

Abstract

Osteoarthritis (OA) is the most common degenerative joint disorder. Multipotential stromal cells (MSCs) have a crucial role in joint repair, but how OA severity affects their characteristics remains unknown. Knee OA provides a good model to study this, as osteochondral damage is commonly more severe in the medial weight-bearing compartment compared to lateral side of the joint. This study utilised in vitro functional assays, cell sorting, gene expression and immunohistochemistry to compare MSCs from medial and lateral OA femoral condyles. Despite greater cartilage loss and bone sclerosis in medial condyles, there was no significant differences in MSC numbers, growth rates or surface phenotype. Culture-expanded and freshly-purified medial-condyle MSCs expressed higher levels of several ossification-related genes. Using CD271-staining to identify MSCs, their presence and co-localisation with TRAP-positive chondroclasts was noted in the vascular channels breaching the osteochondral junction in lateral condyles. In medial condyles, MSCs were additionally found in small cavities within the sclerotic plate. These data indicate subchondral MSCs may be involved in OA progression by participating in cartilage destruction, calcification and sclerotic plate formation and that they remain abundant in severe disease. Biological or biomechanical modulation of these MSCs may be a new strategy towards cartilage and bone restoration in knee OA.

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

“…All articular cartilage was harvested from the lateral and medial condyle surfaces using a scalpel, and chondrocytes were isolated as described before and kept separate (Sanjurjo-Rodriguez et al, 2019). We were interested to see whether the nature of cells (MSCs versus chondrocytes) or their loading environment (medial versus lateral) had a stronger effect on their gene expression.…”

“…The fixed dishes were stained with methylene blue for CFU-F counting and were scanned for CFU-F area and integrated density (ID) analysis, as previously described (Ganguly et al, 2019;Sanjurjo-Rodriguez et al, 2019). Briefly, scanned images were converted to 8-bit format, calibrated, and analyzed using ImageJ software.…”

“…Tri-lineage differentiation was performed on the same cultures, as described before (Sanjurjo-Rodriguez et al, 2019). Briefly, SF MSCs were seeded in 24-well plates (Corning) for adipogenic and osteogenic differentiation.…”

“…In vitro motility of SB and SF MSCs was assessed using a scratch assay as described before (Sanjurjo-Rodriguez et al, 2019). Briefly, MSCs were grown to confluence in a 6-well plate in StemMACS MSC Expansion Media.…”

“…On the other hand, MSCs present in the SB are accessible through subchondral plate perforation and are believed to be responsible for limited cartilage regeneration following microfracture treatment of focal cartilage lesions (Dwivedi et al, 2018). In our previous work, we investigated SB MSCs in advanced knee OA and compared MSCs from the medial, commonly weight-bearing compartment, with the lateral side of the joint (Sanjurjo-Rodriguez et al, 2019). This work used collagenase-assisted release of MSCs from subchondral trabecular bone surfaces and marrow-filled bone cavities and demonstrated large MSC numbers in both lateral and medial femoral condyles.…”