Regulation of Gdf5 expression in joint remodelling, repair and osteoarthritis

Abstract

Growth and Differentiation Factor 5 (GDF5) is a key risk locus for osteoarthritis (OA). However, little is known regarding regulation of Gdf5 expression following joint tissue damage. Here, we employed Gdf5-LacZ reporter mouse lines to assess the spatiotemporal activity of Gdf5 regulatory sequences in experimental OA following destabilisation of the medial meniscus (DMM) and after acute cartilage injury and repair. Gdf5 expression was upregulated in articular cartilage post-DMM, and was increased in human oA cartilage as determined by immunohistochemistry and microarray analysis. Gdf5 expression was also upregulated during cartilage repair in mice and was switched on in injured synovium in prospective areas of cartilage formation, where it inversely correlated with expression of the transcriptional co-factor Yes-associated protein (Yap). Indeed, overexpression of Yap suppressed Gdf5 expression in chondroprogenitors in vitro. Gdf5 expression in both mouse injury models required regulatory sequence downstream of Gdf5 coding exons. Our findings suggest that Gdf5 upregulation in articular cartilage and synovium is a generic response to knee injury that is dependent on downstream regulatory sequence and in progenitors is associated with chondrogenic specification. We propose a role for Gdf5 in tissue remodelling and repair after injury, which may partly underpin its association with OA risk. Growth and Differentiation Factor 5 (GDF5) is a major risk locus for osteoarthritis (OA), the most common joint disease characterised by progressive loss of articular cartilage, remodelling of subchondral bone, chondro-osteophyte formation and synovitis. Common variants spanning a large 130 kb interval confer risk of hip and knee OA 1-3. A well-studied SNP is located in the 5′ UTR of the GDF5 gene (rs143383), with the OA susceptibility allele resulting in decreased GDF5 expression 2,4-6. Gdf5 plays important roles during joint formation. It is one of the earliest genes expressed in the embryonic joint interzone 7-10 , fated to give rise to joint tissues including articular cartilage, synovium, menisci, and ligaments 11,12. Gdf5-expressing progenitors are continuously recruited into joint interzones throughout development 13 and their progeny retain skeletal joint stem/progenitor activity in adulthood 14. Following injury to the joint surface, Gdf5-lineage mesenchymal stromal/stem cells (MSCs) proliferate to underpin synovial hyperplasia and migrate to the site of injury, through the activity of the transcriptional co-factor Yes-associated protein (Yap), where they repair cartilage 14. Loss-of-function mutations in GDF5 have been linked to congenital disorders including Hunter-Thompson syndrome 15 , brachydactyly type C 16 , and DuPan syndrome 17. These syndromes are partly phenocopied in brachypodism (bp) mice, which harbour Gdf5 coding mutations 7. Homozygous bp mice have dysmorphic knees lacking cruciate ligaments 18,19. Heterozygous bp mice, which model human GDF5 variants that cause decreased

Yes-Associated Protein 1: Role and Treatment Prospects in Orthopedic Degenerative Diseases

“…Several studies have confirmed that YAP1 is overexpressed in OA animal model tissues, and the YAP1 content increases with the severity of OA (Nie et al, 2019;Zhang et al, 2019;Kania et al, 2020). Gong et al (2019) reached the same conclusion in studies with an OA mouse model and human OA tissue:…”

“…In the process of chondrogenic differentiation, sex-determining region Y-type high mobility group box protein 9 SOX9) is one of the primary regulators of early chondrocyte differentiation and interacts with the transcription factors SOX5 and SOX6 to promote the proliferation and differentiation of chondrocytes, subsequently promoting the expression of chondrocyte matrix components, including aggrecan and type II collagen (Darling and Athanasiou, 2005). YAP1 has been reported to be a negative regulator of chondrogenesis, and the level of YAP1 expression has been shown to be a key element in maintaining chondrocyte function in vitro (Karystinou et al, 2015;Kania et al, 2020). Zhang et al (2019) observed through qPCR and Western blotting analyses that YAP1 overexpression significantly downregulates the expression of Runx2, osteocalcin, and collagen I related to ATDC5 cell differentiation, while inhibition of YAP1 significantly enhances the expression of Runx2, osteocalcin, and collagen I.…”

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

“…Our data showed an increase in TGFβ receptor 2 and 3 expression in SF MSCs early in KJD, which may represent an enrichment in TGFβ-responsive MSCs during early stages of treatment. Interestingly, this coincided with higher-level GREM1 and GDF5 transcripts in week 3 MSCs, the molecules associated with chondrogenesis and healthy cartilage homeostasis (Leijten et al, 2013;Worthley et al, 2015;Kouroupis et al, 2019;Kania et al, 2020). A sustained increase in ACAN expression in SF MSCs following KJD suggests some degree of their chondrogenic commitment and may be explained by the activity of these GREM1-and GDF5-expressing cells.…”

“…Therefore, we separately considered a group of transcripts that showed a significant change in their expression levels at week 3 followed by "return to baseline" at week 6 ( Figure 6). Remarkably, this group included GDF5 (4.8-fold increase at week 3, p < 0.01), associated with chondrogenic specification in joint interzone and synovium (Kouroupis et al, 2019) and cartilage-resident progenitors (Kania et al, 2020), and gremlin 1 (GREM1) (3.9-fold at week 3, p < 0.001) described as characteristic for osteochondroreticular stem cells within the metaphysis of long bones (Worthley et al, 2015) and enriched in healthy articular cartilage where it regulates hypertrophy (Leijten et al, 2013) (Figure 6A). A similar pattern of changes was seen for TGFBR2 and TGFBR3 ( Figure 6B) and IGFR (Figure 6C), the receptors for cartilage-anabolic growth factors and involved in pathogenesis of OA (Goldring, 2000).…”

“…*p < 0.05; **p < 0.01; ***p < 0. levels of expression ( Supplementary Table 1), 5% genes showed significantly >2-fold higher expression in lateral SB MSCs, and 26% of genes were significantly >2-fold higher expressed in SF MSCs (Table 1). Interestingly, genes previously described as highly specific for synovial-origin MSCs, such as SFRP4 (Sekiya et al, 2012;Baboolal et al, 2014) and growth differentiation factor (Kania et al, 2020), were not expressed at the higher levels in OA SF MSCs ( Table 1). To summarize, compared with both medial and lateral SB MSCs, SF MSCs expressed lower levels of osteogenesisrelated genes, consistent with our original hypothesis that SF MSCs were less osteogenically committed (McGonagle et al, 2017) ( Figure 3A).…”