Recent evidences indicate that signal transducer and activator of transcription 3 (STAT3) is one of the crucial signaling pathways in the progression of diabetic nephropathy (DN). Here, we investigated the hypothesis that pharmacological blockade of STAT3 limits the progression of DN. Treatment with selective STAT3 inhibitor, S3I-201 for 16 weeks significantly attenuated kidney injuries in streptozotocin (STZ) induced diabetic mice, associated with downregulated expression of TGF-β1, ACE/AT1, and VEGF in diabetic mouse kidneys. Similar results were confirmed using genetic knockdown of STAT3 in mouse kidneys by injections of AAV2 expressing STAT3 shRNA in diabetic mouse. Further, STAT3 localization in kidney tissue was evaluated using immunofluorescent double-staining analysis, which indicated that STAT3 expression was mainly in the tubular epithelial cells. As expected, in renal tubular epithelial NRK-52E cells, high glucose (HG)-induced overexpression of TGF-β1, ACE/AT1, and VEGF were abrogated by S3I-201 pretreatment, as well as by genetic knockdown of STAT3 using specific siRNA sequence. This study found that renal tubular epithelial cells contributed to STAT3-mediated progression of DN and provided the first evidence that pharmacological inhibition of STAT3 attenuates DN.

ObjectivesTo clarify the key role of circulating interferon-γ (IFN-γ) and to improve the clinical efficacy of mesenchymal stem cell (MSC) transplantation (MSCT) in patients with rheumatoid arthritis (RA).MethodsStudy of wild-type or IFN-γR-/- MSCT was first evaluated in a murine model of collagen-induced arthritis (CIA) following which a phase 1/2 randomised controlled study was conducted in 63 patients with RA who responded poorly to regular clinical treatments. Subjects were randomly assigned to an MSCT monotherapy group (n=32) or an MSCT plus recombinant human IFN-γ treatment group (n=31), with 1 year of follow-up. The primary end points consisted of efficacy as assessed as good or moderate EULAR response rates and the proportion of patients at 3 months attaining American College of Rheumatology 20 (ACR20) response rates.ResultsIn the murine studies, wild-type MSCT significantly improved the clinical severity of CIA, while IFN-γR-/- MSCT aggravated synovitis, and joint and cartilage damage. Transitioning from the murine to the clinical study, the 3-month follow-up results showed that the efficacy and ACR20 response rates were attained in 53.3% patients with MSCT monotherapy and in 93.3% patients with MSCT combined with IFN-γ treatment (p<0.05). No new or unexpected safety issues were encountered in 1-year follow-up for either treatment group.ConclusionsThe results of this study show that IFN-γ is a key factor in determining the efficacy of MSCT in the treatment of RA, and that an MSC plus IFN-γ combination therapeutic strategy can greatly improve the clinical efficacy of MSC-based therapy in RA patients.

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