OBJECTIVETo study the differentiation potential of human umbilical cord-derived mesenchymal stem cells (UCMSC) into human sweat gland cells (hSGC) and the role of extracellular signal-regulated kinase (ERK) pathway.

METHODSUCMSC and hSGC were isolated and cultured in vitro. The former was identified with expression of CD14, CD29, CD34, CD44, CD45, CD105, cytokeratin 7 (CK7), CK19, and carcinoembryonic antigen (CEA), while the latter was identified with expression of CK19 and CEA. UCMSC with density of 5 x 10(4) cells per well placed in lower compartment of Transwell chamber were divided into control group (C, cultured with nutrient solution without any stimulation), thermal injury group (TI, treated with heat-shocked hSGC with density of 1 x 10(4) cells per well inoculated into the upper compartment of Transwell chamber for indirect co-culture), thermal injury + EGF group (TIE, treated with indirect co-culture as used in TI group, with addition of 50 ng/mL EGF), thermal injury + PD98059 group (TIP, treated with indirect co-culture as used in TI group, with addition of 10 nmol/mL ERK specific inhibitor PD98059) according to the random number table. One week after culture, the positive expression rates of CK7 and CK19 in UCMSC were detected by flow cytometry, the expression of CK19 and CEA in UCMSC were examined with immunohistochemical staining and the positive expression rate of CEA was calculated, and the expression level of phosphorylated ERK (pERK) was determined by Western blotting. Data were processed with one-way analysis of variance.

RESULTS(1) CD29, CD44, and CD105 were highly expressed in UCMSC, accompanied by low or negative expression of CD14, CD34, CD45, CK7, CK19, and CEA. The expression of CK19 and CEA were positive in hSGC. The two results showed that UCMSC and hSGC were pure. (2) Compared with those of C group [(2.2 +/- 1.5)%, (2.2 +/- 0.7)%, (3.3 +/- 0.7)%, 0.640 +/- 0.026], the expression levels of CK7, CK19, CEA, and pERK in UCSMC of TI group [(6.4 +/- 0.7)%, (5.7 +/- 0.3)%, (7.4 +/- 1.0)%, 0.790 +/- 0.049] and TIE group [(14.3 +/- 1.0)%, (12.6 +/- 1.1)%, (17.6 +/- 2.3)%, 1.200 +/- 0.032] were significantly increased (with F value respectively 78.49, 139.36, 87.13, and 191.74, P values all below 0.01), and those of TIE group were higher than those of TI group (with F value from 50.14 to 145.47, P values all below 0.01). There were no obvious difference in the 4 indexes between TIP group and C group (with F value from 0.00 to 0.13, P values all above 0.05).

CONCLUSIONSUCMSC co-cultured with heat-shocked hSGC can differentiate into hSGC, and ERK signal pathway participates in the process of differentiation of UCMSC into hSGC.