| The continued renewal of feathers in avian species is maintained through the presence of feather keratinocyte stem cells (FKSCs), which link molecular activity and cellular behavior to the functional morphology of the epidermis, dermis, appendages, muscle and nerve fibers. In order to characterize FKSCs and understand the proliferation and trans-differentiation potentials involved in such relationships, we developed a novel culture scheme to select FKSCs from chick feather follicles and characterized these FKSCs. We further investigated effects of the ectopic expression of human telomerase reverse transcriptase (hTERT) on the replicative senescence of chicken feather keratinocyte stem cells. The results showed that FKSCs were capable of self-renewal and proliferation. These cells were positive for epidermal stem cell-specific molecules such as Integrinβ1, CD49c, keratin 15 (K15) and keratin 19 (K19). FKSCs had multipotentials of differentiation into adipose, neural cells and terminally differentiated keratinocyte, as indicated by the expression of cell lineage-specific markers. The formation of organization-like structures from FKSCs was also analyzed. We established immortalized hTERT-EGFP-FKSCs cell lines. The ectopic expression of hTERT in native FKSCs increased the proliferation potential of FKSCs. The cells transduced with hTERT grew indefinitely in vitro. The cell lines expressed hTERT-EGFP genes without tumorigenic transforming activity and sustained some parental cellular characteristics. In vivo transplantation of hTERT-EGFP-FKSCs showed the multi-linleage differentiation potential in developing chicken embryos. The above data provide a novel framework for understanding the telomere activity in different species and suggest the new insight for manipulating TERT for therapeutic purposes in treating tissue injury and aging.
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