Low temperature culture enhances ameloblastic differentiation of human keratinocyte stem cells

Previous studies have demonstrated that several types of human stem cells of non-dental origin can be induced to differentiate into enamel-secreting ameloblasts after recombined with mouse embryonic dental mesenchyme. However, the successful rate of ameloblastic differentiation is about rather low, which presents a major obstacle for future stem cell-based whole tooth bioengineering. Previous studies have shown that cultures at reduced temperature could improve the differentiation capability of stem cells in tissue engineering. In this study, we systematically investigated the effects of low temperature on the viability, proliferation and stemness of human keratinocytes stem cells (hKSCs) in cell culture and further examined ameloblastic differentiation of the hKSCs in human-mouse recombinant chimeric tooth germs. Our results demonstrated that low temperature indeed reduces growth rate and maintains healthy undifferentiated morphology of hKSCs without any effects on cell viability. Moreover, examination of stemness makers revealed improved stemness of hKSCs cultured at low temperature with increased expression of stemness markers K15, CD29 and p63 and decreased expression differentiation marker K10, as compared to those cultured at 37 °C. These low temperature treated hKSCs, when recombined with mouse embryonic dental mesenchyme, exhibited significantly increased rate (40%) of ameloblastic differentiation, as compared to that (17%) in tissue recombinants with those hKSCs treated at standard temperature. Our studies demonstrate that low temperature cell culture improves the stemness and plasticity of hKSCs, which in turn enhances ameloblastic differentiation capability of the stem cells in bioengineered teeth.