Cell Density-Dependent Upregulation of PDCD4 in Keratinocytes and Its Implications for Epidermal Homeostasis and Repair

The study explored the role of Programmed Cell Death 4 (PDCD4) in keratinocytes, finding that PDCD4 is upregulated in a cell density-dependent manner and is crucial for regulating keratinocyte proliferation and contact inhibition. Knockdown of PDCD4 using siRNAs in HaCaT cells led to increased cell proliferation and impaired contact inhibition, with an upregulation of cyclin D1 observed. PDCD4 expression was also noted in different stages of the hair cycle and during wound healing in vivo, suggesting its involvement in epidermal homeostasis and repair. The study indicates that PDCD4 is a key regulator in maintaining the balance of skin cell growth and repair, with potential implications for understanding hair follicle cycling and wound healing processes. The number of HaCaT cells used in the study for cell cycle analysis was 3, and for the quantification of EdU-positive cells, the number was 10.