Small molecules facilitate single factor-mediated sweat gland cell reprogramming

Background Large skin defects severely disrupt the overall skin structure and can irreversibly damage sweat glands (SG), thus impairing the skin's physiological function. This study aims to develop a stepwise reprogramming strategy to convert fibroblasts into SG lineages, which may provide a promising method to obtain desirable cell types for the functional repair and regeneration of damaged skin. Methods The expression of the SG markers cytokeratin 5 (CK5), cytokeratin 10 (CK10), cytokeratin 18 (CK18), carcino-embryonic antigen (CEA), aquaporin 5 (AQP5) and alpha-smooth muscle actin (alpha-SMA) was assessed with quantitative PCR (qPCR), immunofluorescence and flow cytometry. Calcium activity analysis was conducted to test the function of induced SG-like cells (iSGCs). Mouse xenograft models were also used to evaluate the in vivo regeneration of iSGCs. BALB/c nude mice were randomly divided into a normal group, SGM treatment group and iSGC transplantation group. Immunocytochemical analyses and starch-iodine sweat tests were used to confirm the in vivo regeneration of iSGCs. Results EDA overexpression drove HDF conversion into iSGCs in SG culture medium (SGM). qPCR indicated significantly increased mRNA levels of the SG markers CK5, CK18 and CEA in iSGCs, and flow cytometry data demonstrated (4.18 +/- 0.04)% of iSGCs were CK5 positive and (4.36 +/- 0.25)% of iSGCs were CK18 positive. The addition of chemical cocktails greatly accelerated the SG fate program. qPCR results revealed significantly increased mRNA expression of CK5, CK18 and CEA in iSGCs, as well as activation of the duct marker CK10 and luminal functional marker AQP5. Flow cytometry indicated, after the treatment of chemical cocktails, (23.05 +/- 2.49)% of iSGCs expressed CK5(+) and (55.79 +/- 3.18)% of iSGCs expressed CK18(+), respectively. Calcium activity analysis indicated that the reactivity of iSGCs to acetylcholine was close to that of primary SG cells [(60.79 +/- 7.71)% vs. (70.59 +/- 0.34)%, ns]. In vivo transplantation experiments showed approximately (5.2 +/- 1.1)% of the mice were sweat test positive, and the histological analysis results indicated that regenerated SG structures were present in iSGCs-treated mice. Conclusion We developed a SG reprogramming strategy to generate functional iSGCs from HDFs by using the single factor EDA in combination with SGM and small molecules. The generation of iSGCs has important implications for future in situ skin regeneration with SG restoration.