Abstract: Objective To construct OX40Ig genetically modified rat adipose derived mesenchymal stromal cells (ADSCsOX40Ig), and to investigate its immunomodulatory effect on lymphocytes in vitro. Methods The fusion gene expression vector of pcDNA3.1(+)/OX40Ig was constructed and transfected into rat ADSCs by nuclear transfection. The expression of OX40Ig in ADSCs was measured by Western blot assay. The transfected and untransfected ADSCs were co-cultured with rat allogeneic lymphocytes, and were divided into the control group (responder + stimulator), the ADSCs (responder+stimulator+ ADSCs) group, and the ADSCsOX40Ig (responder+stimulator+ADSCsOX40Ig) group. The proliferatory activity of lymphocytes was detected by MTT method. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect interferon (IFN)-γ, interleukin (IL) -10 and transforming growth factor (TGF) - β mRNA levels in lymphocytes. Results The sequencing confirmed that pcDNA3.1(+)/OX40Ig plasmid was successfully constructed, and OX40Ig was highly expressed in transfected ADSCs. Compared with ADSCs, the proliferation inhibition rate of allogeneic lymphocytes was significantly increased in ADSCsOX40Ig (P＜0.05). The expression levels of IFN-γ mRNA decreased gradually, but the expression levels of IL-10 and TGF-β mRNA increased gradually in the control, ADSCs and ADSCsOX40Ig groups (P＜0.05). Conclusion Compared with ADSCs along, ADSCsOX40Ig has better immunomodulatory effects on allogeneic lymphocytes.

Key words: mesenchymal stromal cells, gene fusion, immunomodulation, OX40 ligand, adipose-derived mesenchymal stem cells, eukaryotic expression vector