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Objective: To construct the epidermal model with HaCaT cells and evaluate the feasibility of this model as an in vitro skin irritation test tool., Methods: The HaCaT model was reconstructed with HaCaT cells by adoption gas-liquid surface culture technique, and the EpiKutis ® model was reconstructed with human epidermal keratinocytes by the same techinique as control. Morphology changes of HaCaT and EpiKutis ® models were observed by HE staining. Barrier function assessment was performed with penetration test. According to Organization for Economic Cooperation and Development (OECD) Test Guideline 439, the surface of the HaCaT and the EpiKutis ® models were treated with 20 chemicals for 30 minutes, incubated for 42 hours, and determined tissue viability by MTT assay, to evaluate the irritation of chemicals. Then the results were compared with the irritation of chemicals with the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS) system and validated reference method (VRM) for the classification of chemical, and evaluated the feasibility of this model as an in vitro skin irritation test tool., Results: The results of HE staining showed that there was no complete stratified structure in the HaCaT model. The results of barrier function showed that the ET 50 was 0.99 hours. The results of skin irritation of chemicals showed that the sensitivity was 100% and 100%, the specificity was 50% and 70%, and the accuracy rate was 75% and 85% for HaCaT model and EpiKutis ® model respectively., Conclusion: The epidermal model of HaCaT cells does not possess the complete epidermal physiological structure, the barrier function as ET 50 of the HaCaT model is lower than EpiKutis ® model, the chemicals in vitro skin irritation test results do not meet the OECD criteria for the determination of stimulants, so the HaCaT model is not suitable as a replacement tool in vitro to determine the chemicals skin irritation.

Adult pluripotent stem cells, such as mesenchymal stem cells derived from bone marrow and adipose tissue are capable of multilineage differentiation. Although autologous stem cell transplantation is an effective alternative to organ transplantation, the loss of cell viability and differentiation confinement of implanted cells has largely impaired the therapeutic efficacy. To produce biomaterial-free liver construct to integrate into living tissue, we isolated adipose mesenchymal stem cells and subjected them to a delicate culture configuration to mediate the hepatocyte differentiation. The differentiated hepatocyte-like cells were then inoculated onto poly (N-isopropylacrylamide) (PNIPAAm) grafted cell culture dish. By lowering the culture temperature to 20 degrees C, cells detached from the dish surface into a complete cell sheet. Hematoxylin and eosin staining and immunohistochemistry results showed that cell sheet was composed of 2-3 layers of cells and extracellular matrix was maintained intact. As compared with traditional cell harvest using trypsin digestion, cell sheet fabrication causes no damage to cell membrane and extracellular matrix. Hence, cell sheets would form a better interaction with tissues in situ, and a higher cell viability and therapeutic efficiency would be expected.