Objective To investigate the expression of specific marker molecules in hair-inducing activity of long-term cultured human dermal papilla cells (HDPCs) in vitro.Methods After dissected and cultured the HDPCs in vitro,the cells of passages 1 to 8 were used for experiments.The growth appearances of HDPCs in different passages were observed under inverted microscope.To detect the expression of specific marker molecules of long-term cultured HDPCs,the alkaline phosphatase (ALP) activity of the HDPCs was examined,and the specific genes ALP and insulin-like growth factor-1 (IGF-1) expression levels of HDPCs were determined by real-time quantitative PCR.Results After long-term cultured in vitro,the ALP and IGF-1 expression levels of HDPCs gradually decreased in different passages,as well as the display of the aggregated and cartouche growth.The ALP and IGF-1 expression levels of HDPCs in passage 1 was the highest,they were almost about 6.8-fold and 3.5-fold higher than the HDPCs in passage 8.The ALP staining of the HDPCs in passage 1 and passage 2 were evident,but the cells' ALP staining gradually became much weaker than the cells in the previous passages after the long-term cultured in vitro.Conclusions The expression levels of specific marker molecules ALP and IGF-1 of the HDPCs decrease gradually after long-term cultured in vitro,and the higher passage HDPCs lost the special aggregated and cartouche growth appearance,and hence lead to the loss of hair-inducing activity of HDPCs.