The increased incidence of heat stroke is caused by reduced sweating as a result of failures in tissue homeostasis that occur with aging. Specifically, tissue homeostasis is disrupted by the exhaustion of stem cells. We previously revealed that myoepithelial cells are the stem cells of sweat glands, thereby heat stroke can be avoided by preventing myoepithelial cell loss. Although myoepithelial cells serve as a useful tool for revealing their depletion, only a single strain of sweat gland cells, NCL-SG3, can differentiate into mature cells in adherent culture conditions. Recently, mammary gland cells were shown to maintain a stem cell phenotype in floating spheroid culture. Similarly, we reported the culture of primary undifferentiated myoepithelial cells in spheroid culture conditions. However, these myoepithelial cells differentiated into mature epithelial cells after a few passages. Therefore, we attempted to generate immortalized undifferentiated myoepithelial cells in spheroid culture conditions. Although we first tried to transduce single sweat gland cells with lentiviral vectors carrying immortalized genes hTERT and SV40Tt, they were hardly transduced. Given that the surface (virus-cell contact) area of single cells is narrow, we directly transduced immortalized genes into spheroid architectures covered by myoepithelial cells, which expanded their surface area. Compared with primary sweat gland cells, immortalized sweat gland cells continued to form spheroids beyond the 20th passage. Furthermore, immortalized sweat gland cells co-expressed α-smooth muscle actin and keratin 14, indicating a myoepithelial phenotype. Thus, we generated immortalized myoepithelial cells, which will help to establish sweat gland evaluation systems that mimic sweat gland organs.

Generation of immortalized sweat gland myoepithelial cells and eccrine sweat gland research model