\[Abstract\]ObjectiveTo study the telomerase activity changes during the differentiation of human mesenchymal stem cells (MSCs) into adipocytes and the related mechanism. MethodsHuman MSCs were isolated from human bone marrow by plastic adhesion and were characterized by immune phenotyping. The multilineage differentiation potential of MSCs was confirmed by inducing MSCs to differentiate into osteoblasts and neuron-like cells by corresponding agents. Telomeric repeat amplification protocol (TRAP) assay was performed to examine telomerase activity in MSCs during adipogenic differentiation of MSCs; Western blotting analysis was used to examine the protein expression levels of hTERT, TRF1, and Tankyrase 1. ResultsTRAP showed that telomerase was negative in MSCs, but greatly up-regulated during the adipogenic differentiation process, peaked on the 7th day after adipogenic differentiation of MSCs(P<0.05), and then decreased thereafter. Western blotting analysis showed slight hTERT expression in MSCs, and the expression of hTERT and Tankyrase 1 increased during the adipogenic differentiation process, peaked on the 7th day, and gradually decreased thereafter. The expression of TRF1 remained unchanged. ConclusionTelomerase is weakly expressed in MSCs; the expression is increased during the adipogenic differentiation process of MSCs and then gradually decreases; and Tankyrase 1 may play an important role during the process.