Abstract
Osteoarthritis (OA) is a degenerative joint disease estimated to affect 630 million people worldwide. OA is characterized by the progressive loss of articular cartilage, damage to subchondral bone and chronic inflammation; unfortunately, there is no cure for OA. Human mesenchymal stem cells/multipotent stromal cells (MSCs) have been evaluated as a potential treatment, as these cells can contribute through differentiation into bone and cartilage, and act as trophic mediators to reduce inflammation and promote healing. The safety of MSC therapies has been widely demonstrated and currently, at least 13 clinical trials are testing the efficacy of MSCs to treat OA. We hypothesized here that the efficacy of MSC therapy can be enhanced using lentiviral vectors to overexpress key factors including interleukin-10 (IL-10), IL-1 receptor antagonist (IL- 1RA) or fibroblast growth factor-2 (FGF-2). Based on our experience on how to perform these modifications in a clinically-compliant manner, our primary goal was to functionally characterize these genetically modified MSC in vitro. Collectively, experiments performed in our lab: (1) show effective over-expression of the respective transgenes at the mRNA and protein levels; (2) address the number of viral insertions per cell; (3) demonstrate that over-expressing FGF-2 exhibit increased proliferation rates and reduced differentiation potential into both the osteogenic and adipogenic lineage. In contrast, over-expression of IL-1RA or IL-10 did not affect cell proliferation or differentiation potential. Importantly, MSCs over-expressing IL-10 reveal significant immune suppressive abilities in vitro, as proliferation of PHA-activated peripheral blood mononuclear cells (PBMCs) were strongly inhibited in a co-culture system. These results support the notion of a “second generation of MSCs,” using genetic modifications to enhance therapeutic efficacy, while maintaining an excellent safety profile. Treatment of naturally occurring OA in dogs is now underway using canine MSCs overexpressing homologous IL-10. These studies will help establish safety and generate a proof of concept for advancing to human trials.