Targeting Mesenchymal Stem Cells to damaged cartilage in Osteoarthritis

Abstract

Osteoarthritis is a condition which results in the degradation of cartilage, the protective tissue which enables movement of our joints with a low coefficient of friction. No treatment is currently available to cure the cause of the disease. The injection of Mesenchymal Stem Cells (MSCs) into the joints of osteoarthritic patients has been investigated. Although these injections were shown to improve pain, no cartilage repair was observed, and it was shown that MSCs did not engraft at the site of injection. We hypothesised that increasing the number of cells which can accumulate onto the lesion would lead to better cartilage regeneration. This thesis describes the development of a method to specifically target MSCs towards type II gelatin, a molecule which is uniquely found in damaged cartilage, by coating them with a protein which binds to this substrate. MSCs were successfully coated with a chimeric protein named 222, which was engineered following the expression and characterisation of the Collagen Binding Domain (CBD) of the Matrix Metalloprotease MMP-2. 222 was shown to bind to type II gelatin with a Kd of 2.46 nM, a value which was 14 times lower than that obtained for the CBD. The protein was shown to be present at the cell surface by confocal microscopy, and the viability of coated MSCs was similar to that of wild-type cells. Cells coated with 222 were shown to bind significantly better to type II gelatin than uncoated cells in vitro, with a median attachment of 224.4% for coated cells compared to 23.67% for wild-type cells.