Inflammation-induced transgene expression in genetically engineered equine mesenchymal stem cells.

This study focused on enabling osteoarthritis treatment through genetically engineered mesenchymal stem cells (MSCs). By making use of specific genes and responsive systems in these stem cells, the researchers could induce transgene expression in the presence of natural inflammatory substances, a crucial step towards realizing a regenerative medicine for osteoarthritis.

Research Method

• The researchers used bone marrow-isolated equine MSCs that were stably transduced (genetically modified) with an HIV-1 based lentiviral vector expressing the luciferase gene controlled by the nuclear factor κB (NFκB)-responsive promoter.
• These modified cells were then stimulated with different concentrations of either Interleukin (IL)-1β or Tumour Necrosis Factor (TNF)α, both of which are naturally occurring substances in the body.
• The expression of luciferase, which is a marker gene, was measured in the transduced cells following cytokine stimulation.

Findings

• The researchers observed a dose-dependent increase in luciferase expression in the transduced MSCs when these cells were stimulated with cytokines.
• The induction effect was more potent in cells treated with TNFα when compared to those stimulated with IL-1β.
• The peak transgene expression was achieved after 48 hours of stimulation and the same time was required to return to baseline luciferase expression levels after removing the stimulus.
• Repeating cycles of induction allowed for a controllable on-off modulation of transgene expression, without the cells becoming unresponsive to induction.
• Importantly, the researchers found that the NFκB-responsive promoter retained its inducibility even in chondrogenically (developing into cartilage) differentiated equine MSC/Luc cells.

Conclusion

• The key outcome of this research was the demonstration of the potential of “on-demand” transgene expression from the NFκB-responsive promoter using naturally occurring inflammatory cytokines in undifferentiated and chondrogenically differentiated equine MSCs.
• This potentially implicates a promising new approach that leverages the paracrine, differentiation, and self-renewal abilities of MSCs for cell-based treatments of osteoarthritis.
• The development of systems allowing transgene expression regulated by substances naturally occurring in the body, will be central to further progress in this field of research.