Adeno-Associated Virus-Mediated Overexpression of Interleukin-10 Affects the Immunomodulatory Properties of Equine Bone Marrow-Derived Mesenchymal Stem Cells.

The current study investigates the combined application of bone marrow-derived mesenchymal stem cells (BM-MSCs) and Interleukin (IL)-10 through gene therapy in treating posttraumatic osteoarthritis (OA). The expectation was that BM-MSCs overexpressing IL-10 would exhibit superior immunomodulation, yielding superior suppression of T cell proliferation and inflammatory cytokines, thereby safeguarding the extracellular matrix (ECM). However, the IL-10 overexpression in the AAV-IL10-transduced BM-MSCs did not significantly outperform the plain MSCs in suppressing T cell proliferation and while it slightly reduced the synthesis of certain inflammatory cytokines, it did not prevent the ECM loss.

Objective and Hypothesis

• The study sought to explore the combined effect of BM-MSCs and immunomodulatory cytokine, IL-10, for OA treatment. The hypothesis was that overexpressing IL-10 in BM-MSCs would provide superior immunomodulation, yielding increased suppression of T cell proliferation and reduced synthesis of inflammatory cytokines. This would in turn protect the ECM in a stimulated OA model.

Experiments and Outcomes

• The experiments divided treatment groups into untransduced BM-MSCs, AAV-IL10-transduced BM-MSCs, and AAV-null transduced BM-MSCs. These groups were either stimulated or unstimulated with IL-1β/TNF-α. It was observed that T cell proliferation dropped considerably upon introducing BM-MSCs. However, no particular distinction was found in T cell suppression between cells cultured with AAV-IL10-transduced and AAV-null transduced BM-MSCs.
• Furthermore, it was noticed that the AAV transduction itself was associated with decreased synthesis of IL-1β, IL-6, and TNF-α. Within the AAV-transduced BM-MSCs, expressions of certain genes downregulated and the expression in cartilage explants co-cultured with AAV-transduced BM-MSCs also followed a similar pattern.
• Key elements of the hypothesis were not conclusively proven as while IL-10 overexpression enhanced BM-MSC-mediated T cell suppression, no clear evidence surfaced regarding the significant reduction in inflammation-driven cartilage degradation in cultures containing AAV-IL10-transduced BM-MSCs.

Conclusions and Further Investigation

• Contrary to the original hypothesis, IL-10 overexpression in BM-MSCs did not demonstrate a substantially higher ability to suppress T cell proliferation or inflammatory response. Furthermore, the ECM loss was not ameliorated either in AAV-IL10-transduced or AAV-null transduced co-cultures. This indicates that applying gene therapy for OA combining BM-MSCs and IL-10 overexpression may not be as effective as originally estimated.
• It was noted that the AAV transduction itself had a significant effect on BM-MSCs paracrine signaling. This finding calls for further investigation of AAV transduction’s role in BM-MSCs paracrine signaling and subsequent effects on the immunomodulation in OA treatment.