Disease Modifying Osteoarthritis Drug Discovery Using A Temporal Phenotypic Reporter In Primary Human Chondrocytes

Osteoarthritis is a significant and growing problem with no disease modifying drugs in the clinic. Current screening platforms typically use 2D culture, immortalized or non-human cells in a hyperoxic environment. To challenge this paradigm and identify new drugs, we engineered primary human chondrocytes with a secreted luciferase reporter under the control of the articular cartilage marker, type II collagen. We then successfully screened a natural product library using a high throughput model with COL2A1-Gaussia luciferase primary human chondrocyte reporter cells in 3D aggregates under physioxia. We identified several candidate compounds that increased type II collagen over controls, with aromoline being the best candidate. Aromoline is a bisbenzylisoquinoline alkaloid that has been studied for its anti-proliferative, anti-inflammatory, and anti-microbial properties, and we are the first to explore its effects on chondrocytes and chondrogenesis. In silico analysis of predicted targets narrowed by RNA-Seq data on expression provided an unexpected initial candidate target protein: the dopamine receptor D4 (DRD4). The researchers confirmed upregulation in the expression of DRD4 and type II collagen after treatment with aromoline. This novel approach combining in silico and in vitro methods provides a platform for drug discovery in a challenging and under-researched area. In conclusion, a novel drug (aromoline) and target receptor (dopamine receptor D4) were identified as stimulating type II collagen, with the goal to treat or prevent osteoarthritis.