ILK regulates osteogenic differentiation of Human Periodontal Ligament Stem Cells through YAP‐mediated Mechanical Memory

Mechanical memory meant the mechanical properties of the matrix could influence the cell fate even after the matrix was changed and has been justified in many kinds of cells. To utilize the phenomenon to improve periodontal tissue engineering, we studied whether mechanical memory existed in human periodontal ligament stem cells and testified if ILK plays a role in this process. The substrate of different stiffness was fabricated by gelatin methacrylate hydrogel. Two groups of hPDLSCs with stiff (St) and soft (So) matrix, respectively, were cultivated. Then, half of the cells exchanged their matrix stiffness in the fourth passage and therefore So, St, So-St, and St-So were formed. Morphology of hPDLSCs and intracellular location of YAP was observed via fluorescence staining, osteogenic differentiation of hPDLSCs was assessed by real-time PCR, ALP staining, and Western blot. Then, all these were reassessed after the ILK gene had been knocked down. The results showed that morphology and YAP location of hPDLSCs were different between matrix changed and unchanged groups; osteogenic genes expression, ALP staining, and Western blot also varied. After the ILK gene had been knocked down, the YAP location and osteogenic activity of hPDLSCs were significantly influenced. Thus, it could be concluded that mechanical memory exists in hPDLSCs; ILK is involved in this process.