Table 1.

Analysis of cell surface marker expression by flow cytometry after transfection (%, $\overline{X}\pm \mathrm{SD}$).

Group	N	CD29	CD44	CD34	CD45
hBMSC P3	5	98.10 ± 1.10	94.99 ± 1.00	0.32 ± 0.12	1.78 ± 0.44
hPPE-hBMSC	5	99.08 ± 0.55	95.07 ± 2.35	0.43 ± 0.40	1.48 ± 0.45
pBABE-hBMSC	5	98.99 ± 0.59	93.37 ± 2.36	0.57 ± 0.35	1.82 ± 0.49
F value	—	2.368	1.141	0.815	0.796
P value	—	0.136	0.352	0.466	0.474

Note. The third passage of cultured hBMSCs, pBABE-hBMSC, and hPPE-hBMSCs were analyzed using fluorescence-activated cell sorting (FCS) to confirm the cellular identity of cultured cells. The results confirmed these cells expressed CD 29 and CD 44 surface makers but were CD 34 and CD 45 negative, consistent with characteristic surface markers of undifferentiated BMSCs. The lack of expression of CD34 and CD45 suggested that the cell population was depleted of hematopoietic stem cells. The multipotency of these cells further verified the cellular nature of BMSCs. The results also revealed that BMSCs kept the same cellular identity after transfection with the vector and the hPPE gene. hPPE: human proenkephalin; hBMSCs: human bone marrow stem cells. pBABE-hBMSCs: pBABE-hBMSCs group, hPPE-hBMSCs: hPPE-hBMSCs group.