M Khorraminejad Shirazi - S tudent research committee ,Shiraz University of Medical Sciences,Shiraz ,Iran
M DORVASH - S tudent research committee ,Shiraz University of Medical Sciences,Shiraz ,Iran
MA FAGHIHI - Persian BayanGene Research and Training Center, Shiraz Universityof Medical Sciences, Shiraz, Iran
A ATTAR - Department of Cardiovascular Medicine, Shiraz University ofMedical Sciences, Shiraz, Iran
M SANI - Department of Tissue Engineering and Applied Cell Sciences,School of Advanced Medical Sciences and Technologies, ShirazUniversity of Medical Sciences, Shiraz, Iran
A Monabati - Department of Pathology, Shiraz University of Medical Sciences,Shiraz, Iran

Objective: Tissue engineering has yet to reach its ideal goal,i.e. creating profitable off-the-shelf tissues and organs. One ofthe major challenges of this field that affects the outcome of thecell transplantation is the in vitro aging and replicative senescenceof the cell source.Materials and Methods: In the present work, Passage ۵ (P۵)adipose-derived mesenchymal s tem cells (MSCs) were treated with control media, nicotinamide (NAM), AICAR, or thecombination of AICAR+NAM till P۱۰. Proliferative capacity,senescence-associated changes, multi-lineage differentiationpotential, CDK-inhibitors -P۱۶ and P۲۱-, ROS, and apoptoticmarkers were compared between cells of P۵ and P۱۰. Furthermore,we s tudied the effects of AICAR and NAM on mTORC۱activity, and autophagy.Results: Our results showed that MSCs treated with NAM,AICAR, or both demons trated an increase in proliferation andos teogenic differentiation potential, which was amplified in thegroup receiving both. AICAR or NAM treatment resulted in reducedexpression of β-galactosidase and decreased accumulationof dysfunctional lysosomes. Also, NAM or AICAR+NAMsignificantly reduced the cellular ROS in aged MSCs. Moreover,AICAR and NAM adminis tration attenuated mTORC۱ activityand boos ted autophagy.Conclusion: In general, inhibition of mTORC۱ by AICAR andNAM upregulates autophagy, retains MSCs’ self-renewal capacity,and delays senescence of MSCs after prolonged in vitroculture. Furthermore, our findings showed that concomitant useof AICAR and NAM shows a synergis tic effect on the attenuationof cellular senescence. Our findings provide a viable optionto slow down the in vitro aging of the s tem cells and conqueraging as a limiting factor in tissue engineering.

Aging, Autophagy, mTOR, Senescence