Mesenchymal stem cells (MSCs) are promising candidates for tissue regeneration and disease treatment. However, long-term in vitro passaging leads to stemness loss of MSCs, resulting in failure of MSCs therapy. Here, we report a melatonin-based strategy to improve cell therapy of in vitro cultured MSCs. Among four small molecules with anti-aging and stem cell-protection properties (rapamycin, resveratrol, quercetin and melatonin), colony forming, proliferation, and osteogenic differentiation assay showed that melatonin was the most efficient to preserve self-renewal and differentiation properties of rat bone marrow MSCs (BMMSCs) after long-term passaging. Functional assays confirmed melatonin treatment did not affect the colony forming, proliferation and osteogenic differentiation of BMMSCs cultured for 1 or 4 passages, but largely prevented the decline of self-renew and differentiation capacity of BMMSCs cultured for 15 passages in vitro. Furthermore, heterotopic osteogenesis assay, critical size calvarial defects repair assay, osteoporosis treatment and experimental colitis therapy assay strongly certified that melatonin preserved the therapeutic effect of long-term passaged BMMSCs on bone regeneration and immunotherapy in vivo. Mechanistically, melatonin functioned by activating antioxidant defense system, inhibiting the pathway of cell senescence, and preserving the expression of gene governing the stemness. Taken together, our findings showed that melatonin treatment efficiently prevented the dysfunction and therapeutic failure of BMMSCs after long-term passaging, providing a practical strategy to improve the application of BMMSCs in tissue engineering and cytotherapy.
Bone marrow-derived mesenchymal stem cells (MSCs) have been recently used in clinical treatment of inflammatory diseases. Practical strategies improving the immunosuppressive property of MSCs are urgently needed for MSC immunotherapy. In this study, we aimed to develop a microRNA-based strategy to improve MSC immunotherapy. Bioinformatic analysis revealed that let-7a targeted the 3 0 UTR of mRNA of Fas and FasL, both of which are essential for MSCs to induce T cell apoptosis. Knockdown of let-7a by specific inhibitor doubled Fas and Fas ligand (FasL) protein levels in MSCs. Because Fas attracts T cell migration and FasL induces T cell apoptosis, knockdown of let-7a significantly promoted MSC-induced T cell migration and apoptosis in vitro and in vivo. Importantly, MSCs knocked down of let-7a were more efficient to reduce the mortality, prevent the weight loss, suppress the inflammation reaction, and alleviate the tissue lesion of experimental colitis and graftversus-host disease (GVHD) mouse models. In conclusion, knockdown of let-7a significantly improved the therapeutic effect of MSC cytotherapy on inflammatory bowel diseases and GVHD. With high safety and convenience, knockdown of let-7a is a potential strategy to improve MSC therapy for inflammatory diseases in clinic.
Estrogen protects bone loss by promoting Fas ligand (FasL) transcription in osteoclasts and osteoblasts to induce apoptosis of osteoclasts. Bone marrowderived mesenchymal stem cells (BMMSCs) express FasL protein, which is necessary for BMMSCs to induce T-cell apoptosis in cell therapy. However, the physiologic function of FasL in BMMSCs is unknown. In this study, using an in vitro coculture system and an in vivo BMMSC transplantation assay, we found that BMMSCs potently induced apoptosis of osteoclasts through the FasL/Fas pathway. Estrogen was necessary for this process as a promoter of FasL protein accumulation in BMMSCs. Furthermore, estrogen elevated FasL protein accumulation, not by increasing FasL gene transcription, but through microRNAmediated posttranscriptional regulation. In brief, estrogen down-regulated expression of miR-181a, a negative modulator of FasL targeting the 39-UTR of FasL mRNA. Estrogen deficiency resulted in excessive miR-181a, which decreased FasL protein levels to suppress BMMSCinduced osteoclast apoptosis. Furthermore, knockdown of miR-181a recovered the BMMSC defect to induce osteoclast apoptosis during estrogen deficiency. Taken together, our results showed that estrogen preserves FasL protein accumulation by inhibiting miR-181a expression in BMMSCs to maintain bone remodeling balance, suggesting a novel mechanism by which estrogen preserves bone mass.-Shao, B., Liao, L., Yu, Y., Shuai, Y., Su, X., Jing, H., Yang, D., Jin, Y. Estrogen preserves Fas ligand levels by inhibiting microRNA-181a in bone marrow-derived mesenchymal stem cells to maintain bone remodeling balance. FASEB J. 29, 3935-3944 (2015). www.fasebj.org
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