Utilizing Synthetic Gene Circuits in Mouse Mesenchymal Stem Cell Derived Chondrocytes to Verify Cartilage Regeneration Outcomes In Vitro

Abstract

Articular cartilage, the avascular connective tissue present at the end of long bones, has limited healing capability when injured. Mesenchymal stem cell (MSC)-based cartilage repair is an appealing treatment strategy since these cells can differentiate into chondrocytes (cartilage producing cells) and produce cartilage macromolecules. However, clinical application of MSC-based cartilage repair requires significant improvements in stability of the chondrogenic phenotype and matrix accumulation by MSC derived chondrocytes (MdChs) under the hostile inflammatory environment of an injured joint. RUNX2 is a transcription factor that is upregulated in chondrocytes during osteoarthritis, which induces chondrocyte hypertrophy and leads to degradation of the cartilage extracellular matrix. Our lab has previously shown that suppression of RUNX2 stabilizes the chondrogenic phenotype and protects human MdChs from inflammation-induced matrix catabolism in vitro. To move forward and test the efficacy of the circuit using in vivo mouse models of PTOA, it needs to be confirmed that the gene circuit is equally successful in mouse MdChs. We hypothesize that the suppression of RUNX2 activity, via the engineered gene circuit used in vitro in human MdChs, will be equally successful at inhibiting RUNX2 and preventing hypertrophic maturation in vitro in mouse MdChs. To confirm this hypothesis, we will be answering the questions: 1) do the engineered RUNX2 gene circuit modified mouse MdChs successfully inhibit RUNX2? and 2) can the articular cartilage-specific phenotype be achieved from mouse MSCs while preventing chondrocyte hypertrophy?