Objective    To investigate the dedifferentiation of epidermal cells into their progenitor stem cells induced by basic fibroblasts growth factors (bFGF) in vitro.     Methods    HEKa cells obtained from Cascade were found flattening and formation of cell-to-cell contacts after 6 to 7 passages

which resembled differentiated epidermal cells in vivo

. To examine the effect of growth factors on the cell proliferative alterations

bFGF (100 ng/ml) was added into the culture medium for different periods (6

12

24

48

or 72 h)

then the cell proliferation was measured by MTT assay. Phenotypic changes and the cell-fate determination of HEKa cells after bFGF treatment were detected by immunocytochemical assays

flow cytometry and RT-PCR analysis. HEK cells with no intervention treatment were used as a control.     Results    MTT assay proved that the optimal culture condition to induce the dedifferentiation of epidermal cells into their progenitors was to culture HEKa cells for 36 to 48 h when the addition of bFGF was 100 ng/ml. After treatment with bFGF for 48 h

clusters of round-shaped cells appeared around differentiated epidermal cells

and expanded progressively thereafter. These cells were smaller in shape and with larger nuclear/cytoplasm ratio

and had not only clonogenicity but also ability to form a cutaneous ridge-like structure. Immunohistochemical staining revealed that the expression levels of β

1

  integrin

CK19 and CK14 were up-regulated

while the expression of CK10 was significant down-regulated after bFGF treatment. Flow cytometry indicated that there were more CK19-positive and CK14-positive cells in the treatment group than in the control (74.77% vs 15.74%

and 87.14% vs 67.26%respectively)

but much lesser CK10-positive cells (4.56% vs 98.56%). Additionally

the mRNA expression levels of β

1

integrin

CK19 and CK14 were up-regulated after bFGF treatment

but that of CK10 was down-regulated.     Conclusion    bFGF can reverse the differentiated process of epidermal cells and induce them to produce immature

stem-like cells

which can proliferate and be used in the wound repair and regeneration of skin tissues.