Because mesenchymal stem cells (MSCs) maintain distinct capacities with respect to self-renewal, differentiation ability and immunomodulatory function, they have been highly considered as the therapeutic agents for cell-based clinical application. Of particular, differentiation condition alters characteristics of MSCs, including cellular morphology, expression of gene/protein and cell surface molecule, immunological property and apoptosis. However, the previous results for differentiation-related apoptosis in MSCs have still remained controversial due to varied outcomes. Therefore, the present study aimed to disclose periodical alterations of pro- and anti-apoptosis in MSCs under differentiation inductions. The human dental pulp-derived MSCs (DP-MSCs) were differentiated into adipocytes and osteoblasts during early (1 week), middle (2 weeks) and late (3 weeks) stages, and were investigated on their apoptosis-related changes by Annexin V assay, qRT-PCR and western blotting. The ratio of apoptotic cell population was significantly (p < 0.05) elevated during the early to middle stages of differentiations but recovered up to the similar level of undifferentiated state at the late stage of differentiation. In the expression of mRNA and protein, whereas expressions of pro-apoptosis-related makers (BAX and BAK) were not altered in any kind and duration of differentiation inductions, anti-apoptosis marker (BCL2) was significantly (p < 0.05) elevated even at the early stage of differentiations. The recovery of apoptotic cell population at the late stage of differentiation is expected to be associated with the response by elevation of anti-apoptotic molecules. The present study may contribute on understanding for cellular mechanism in differentiation of MSCs and provide background data in clinical application of MSCs in the animal biotechnology to develop effective and safe therapeutic strategy.

ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
  Chemicals
  Cell isolation and culture
  MSCs-specific molecules expression
  Differentiation of MSCs
  Apoptosis analysis by Annexin V assay
  Apoptosis analysis by quantitative RT-PCR (qRT-PCR)
  Apoptosis analysis by western blotting
  Statistical analysis
 RESULTS
  Characterization of DP-MSCs
  Apoptosis analysis by Annexin V assay
  Investigation for apoptosis analysis by quantitativeRT-PCR (qRT-PCR) and western blotting
 DISCUSSION
 CONFLICTS OF INTEREST
 ACKNOWLEDGEMENTS
 REFERENCES

• Hyeon-Jeong Lee(College of Veterinary Medicine, Gyeongsang National University)
• Byung-Joon Park(College of Veterinary Medicine, Kyungpook National University)
• Ryoung-Hoon Jeon(College of Veterinary Medicine, Gyeongsang National University)
• Si-Jung Jang(College of Veterinary Medicine, Gyeongsang National University)
• Young-Bum Son(College of Veterinary Medicine, Gyeongsang National University)
• Sung-Lim Lee(College of Veterinary Medicine, Gyeongsang National University)
• Gyu-Jin Rho(College of Veterinary Medicine, Gyeongsang National University)
• Seung-Joon Kim(College of Veterinary Medicine, Kyungpook National University)
• Won-Jae Lee(College of Veterinary Medicine, Kyungpook National University) Correspondence