Development of an osteoarthritis drug screening platform using engineered stem cell lines to identify novel mechanisms of disease biology

Background

Osteoarthritis (OA) is a painful and disabling disease of articulating joints with substantial global healthcare and socioeconomic burden. Management of OA is primarily limited to pain relief. There are no approved disease-modifying OA drugs (DMOADs), hampered by the lack of appropriate pre-clinical test systems. We have developed an immortalised human clonal mesenchymal stem cell (MSC) line capable of differentiating into bone-forming osteoblasts and cartilage-forming chondrocytes, the primary joint tissues affected in OA. From this MSC line we engineered fluorescent and secreted luciferase reporters of osteogenic and chondrogenic differentiation status (alkaline phosphatase and type II collagen promoter-driven reporters respectively) and inflammatory responses (NF-KB promoter-driven reporter). Here, we will determine the feasibility of developing the MSC-based reporter system as a screening platform to identify DMOADs.


Objectives

Validate existing MSC reporter lines

Engineer a new dual (health/disease) reporter line

Test reporters in low- and medium-throughout screens

Functionally test compounds identified

Develop screening platform for scale-up and commercialisation


Experimental Approach

We will undertake a comprehensive validation of our existing reporter lines to characterise both in vivo translatability (via RNAseq) and applicability to use in scaled screening (via robustness testing against chemical compound training sets). We will engineer a dual reporter for simultaneous readouts of health (aggrecan promoter reporter) and disease (ADAMTS5 promoter reporter). Screening using this dual reporter, has the potential to identify pathways that determine the balance of tissue formation versus degradation, which drives OA pathogenesis. We will identify a selection of regulators of osteogenesis and chondrogenesis using a small, well-annotated set of chemical modifiers in conjunction with CRISPR/Cas-9 gene editing and/or RNA silencing. This will define a wider set of chemicals, which will enable us to demonstrate proof-of-concept in medium-throughput assays and provide mechanistic insight into the regulation of MSC differentiation. Compounds identified by these screens will be taken forward for in-depth analysis of effects in osteogenic and chondrogenic differentiation assays. Later work will focus on scale-up, throughput and commercialisation with GSK as the first potential end-users.


Timeliness

The project addresses a key gap in efforts to tackle an urgent yet unmet global healthcare need. The incidence of OA, currently estimated at 250 million affected individuals, is predicted to rise to become a leading cause of disability worldwide.


Novelty

The research tools are unique. The proposed work has the potential to identify novel mechanisms responsible for joint tissue health and provide a highly valuable resource of OA drug discovery.