(a) UN-D
(b) AD
(c) OS
(d) CH
(e) WS
Figure 6: Optimal number of reference genes for normalization. Determining optimal number of reference genes is based on pairwise variation by calculating each two sequential normalization factors. The low V value indicates optimal number of reference genes normalized to target genes. Each V value is presented above bars. V values for (a) undifferentiated status of BMSCs, AMSCs, and SMSCs and (b–d) differentiated cells into adipocytes, osteocytes, and chondrocytes, respectively. (e) Whole status of MSCs.