Abstract: BACKGROUND: With the wide application of adipose-derived stem cells, exploring the regulatory mechanism of adipose stem cells is helpful to broaden the choice of materials.
OBJECTIVE: To investigate the effect of adipose-derived stem cell transplantation on the immune microenvironment of adipose tissue in aged mice and its mechanism of action in aging-associated obesity. 
METHODS: Mouse adipose-derived stem cells were isolated and purified, and transplanted into aged mice at the age of 18 months by intraperitoneal injection. The 18-month-old mice with the same amount of PBS intraperitoneally were used as the old control group, and the 2-month-old mice with the same amount of PBS intraperitoneally were used as the young control group. At 4 weeks after transplantation, changes in food intake and body weight were recorded in each group, and changes in immune cell abundance in adipose, spleen, bone marrow and peripheral blood were analyzed by flow cytometry. The levels of interleukin-6 and tumor necrosis factor-α in adipose tissue and serum were detected using qRT-PCR and ELISA.  
RESULTS AND CONCLUSION: (1) The body weight of adipose-derived stem cells-transplanted aged mice decreased by (1.94±0.26) g compared with aged controls. (2) The results of flow cytometry abundance analysis showed that the abundance of myeloid-derived suppressor cells decreased, the abundance of T cells increased, and the abundance of B cells and NK cells tended to develop in adipose-derived stem cells-transplanted aged mice toward young controls. (3) The results of qRT-PCR and ELISA experiments showed that expression levels of interleukin-6 and tumor necrosis factor-α were significantly down-regulated in the adipose tissue and serum of adipose-derived stem cells-transplanted aged mice. (4) In summary, adipose-derived stem cell transplantation was able to suppress the development of obesity in inflammatory aging mice through the modulation of the immune microenvironment in aged mice.

Key words: adipose-derived stem cells, transplantation, adipose tissue, immunity, microenvironment, inflammation, aging, obesity