Distal-Less Homeobox 5 Is a Therapeutic Target for Attenuating Hypertrophy and Apoptosis of Mesenchymal Progenitor Cells

Abstract

<jats:p>Chondrocyte hypertrophy is a hallmark of osteoarthritis (OA) pathology. In the present study, we elucidated the mechanism underlying the relationship between the hypertrophy/apoptotic phenotype and OA pathogenesis in bone marrow-derived mesenchymal stem cells (BM-MSCs) via gene targeting of distal-less homeobox 5 (DLX5). Our primary objectives were (1) to determine whether DLX5 is a predictive biomarker of cellular hypertrophy in human osteoarthritic tissues; (2) To determine whether modulating DLX5 activity can regulate cell hypertrophy in mesenchymal stem/progenitor cells from marrow and cartilage. Whole transcriptome sequencing was performed to identify differences in the RNA expression profile between human-cartilage-derived mesenchymal progenitors (C-PCs) and bone-marrow-derived mesenchymal progenitors (BM-MSCs). Ingenuity Pathway Analysis (IPA) software was used to compare molecular pathways known to regulate hypertrophic terminal cell differentiation. RT-qPCR was used to measure DLX5 and hypertrophy marker COL10 in healthy human chondrocytes and OA chondrocytes. DLX5 was knocked down or overexpressed in BM-MSCs and C-PCs and RT-qPCR were used to measure the expression of hypertrophy/terminal differentiation markers following DLX5 modulation. Apoptotic cell activity was characterized by immunostaining for cleaved caspase 3/7. We demonstrate that DLX5 and downstream hypertrophy markers were significantly upregulated in BM-MSCs, relative to C-PCs. DLX5 and COL10 were also significantly upregulated in cells from OA knee joint tissues, relative to normal non-arthritic joint tissues. Knocking down DLX5 in BM-MSCs inhibited cell hypertrophy and apoptotic activity without attenuating their chondrogenic potential. Overexpression of DLX5 in C-PCs stimulated hypertrophy markers and increased apoptotic cell activity. Modulating DLX5 activity regulates cell hypertrophy and apoptosis in BM-MSCs and C-PCs. These findings suggest that DLX5 is a biomarker of OA changes in human knee joint tissues and confirms the DLX5 mechanism contributes to hypertrophy and apoptosis in BM-MSCs.</jats:p>

DLX Genes in the Development and Maintenance of the Vertebrate Skeleton: Implications for Human Pathologies

“…Cell hypertrophy is a hallmark of OA. Cartilage samples derived from patients presenting different OA statuses demonstrated a positive correlation between the levels of DLX5 expression and the severity of osteoarthritis, reinforcing the notion that DLX5 is a regulator of cellular hypertrophy, and that its inhibition could improve cell-mediated cartilage tissue repair [ 89 ]. Indeed, DLX5 expression increases with chondrocyte differentiation [ 90 ] and in OA; cultured chondrocytes from OA patients express higher levels of DLX5 and COL10 , compared with non-arthritic chondrocytes.…”

“…Indeed, DLX5 expression increases with chondrocyte differentiation [ 90 ] and in OA; cultured chondrocytes from OA patients express higher levels of DLX5 and COL10 , compared with non-arthritic chondrocytes. DLX5 inhibition in BM-MSCs was found to reduce cellular hypertrophy without inhibiting chondrogenic potential, while overexpression of DLX5 was associated with increased expression of cellular hypertrophy markers [ 89 ]. Articular cartilage calcification indicates cartilage damage.…”

Anti-Dlx5 Retards the Progression of Osteoarthritis through Inhibiting Chondrocyte Hypertrophy and Apoptosis

“…It has been reported that Dlx5 is upregulated in osteoarthritis cartilage [ 15 ]. To investigate the role of Dlx5 in osteoarthritis, knee osteoarthritis was induced by intraarticular injection of papain along with cysteine in rabbits.…”

“…By contrast, overexpression of Dlx5 accelerates chondrocyte hypertrophy [ 14 ]. Moreover, it has been reported that Dlx5 is upregulated in osteoarthritis cartilage [ 15 ]. However, whether Dlx5 plays a role in osteoarthritis progression has not been investigated.…”

Stable human cartilage progenitor cell line stimulates healing of meniscal tears and attenuates post-traumatic osteoarthritis

“…Mesenchymal progenitor cells derived from healthy articular cartilage, herein referred as CPCs, are a small subset of cells that are highly proliferative, chondrogenic, and migratory ( Dowthwaite et al, 2004 ; Seol et al, 2014 ; Jayasuriya and Chen, 2015 ; Jayasuriya et al, 2016 ), making them a potentially useful resource for biologic cell therapy and cartilaginous tissue engineering applications ( McCarthy et al, 2012 ; Seol et al, 2014 ; Bilgen et al, 2018 ; Park et al, 2020 ). Further, they are resistant to cellular hypertrophy and terminal differentiation ( McCarthy et al, 2012 ; Twomey-Kozak et al, 2020 ), unlike mesenchymal progenitor/stem cells from bone marrow and osteoarthritic (diseased) cartilage tissue ( Jayasuriya et al, 2018 ; Hu et al, 2019 ; Liu et al, 2020 ). We have recently demonstrated the efficacy of using stable CPC lines, either as such or in a collagen coated hydroxypropyl cellulose scaffold, to stimulate meniscus injury repair in rat and human ex-vivo organ culture model systems, respectively ( Jayasuriya et al, 2019 ; Newberry et al, 2020 ).…”