199 EFFECTS OF REPROGRAMMING-CONDITIONED MEDIUM ON ULTRAVIOLET RAY A–DAMAGED HUMAN DERMAL FIBROBLASTS

Abstract

Ultraviolet ray A (UVA) is an electromagnetic light with a long wavelength from the sun. The penetration of UVA deep into the human dermis causes changes in cells, such as DNA fragmentation, apoptosis, and senescence, eventually leading a decline of proliferation and wound-healing ability. These changes induced by UVA exposure are similar to those seen in the process of stem cell differentiation. We postulated that the condition that reverses cellular differentiation may alleviate the UVA-induced damage in skin cells. Human dermal fibroblasts (HDF) could be reprogrammed to induced pluripotent stem cells (iPSC). Conditioned medium (CM) was prepared during the process of iPSC reprogramming (referred to as Repro-CM). The UVA-irradiated HDF were cultured in Repro-CM for 24 h. In comparison with CM prepared from the culture of normal HDF and iPSC (referred to as HDF-CM and iPSC-CM, respectively), effects of Repro-CM on UVA-irradiated cells were investigated. Viability, wound-healing ability, apoptosis, and senescence of HDF were analysed by WST-1 assay, scratch assay, Annexin V assay, and senescence-associated β-galactosidase assay, respectively. Upon recovering from the UVA-induced damage, viability and wound-healing ability of HDF were significantly different (P < 0.05) among the treatments in the order of Repro-, HDF-, and iPSC-CM. In the same context, apoptosis and senescence were significantly different (P < 0.05) in the order of iPSC-, HDF-, and Repro-CM. Interestingly, iPSC-CM did not substantially ameliorate UVA-induced damage, suggesting that the conditions optimized to pluripotent stem cells may not be suitable for the recovery from damage in terminally differentiated cells, such as fibroblasts. The RNA-seq analysis was performed to assess the genome-wide transcriptional profile in the process of recovery. Repro- and HDF-CM were categorized more closely than iPSC-CM in hierarchical cluster analysis. In comparison with iPSC-CM, the up-regulated genes by Repro-CM treatment were related to regulation of cell proliferation and cell metabolism, whereas down-regulated genes were related to antiapoptosis and response to stimulation of chemical and organic substances. Overall, providing an environment of reprogramming, as shown by Repro-CM in the present study, may assist recovery of HDF from UVA-induced damage. The results of the study may be applicable in developing pharmaceuticals to treat aging and wrinkling of the skin caused by UVA irradiation.