Adult stem cells(SCs) exist in all tissues that promote tissue growth, regeneration, and healing throughout life. The SC niche in which they reside provides signals that direct them to proliferate, differentiate, or remain dormant; these factors include neighboring cells, the extracellular matrix, soluble molecules, and physical stimuli. In disease and aging states, stable or transitory changes in the microenvironment can directly cause SC activation or inhibition in tissue healing as well as functional regulation. Here, we discuss the microenvironmental regulation of the behavior of SC and focus on plasticity approaches by which various environmental factors can enhance the function of SCs and more effectively direct the fate of SCs.
Myofibroblasts,recognized classically by-smooth muscle actin(-SMA)expression,play a key role in the wound-healing process,promoting wound closure and matrix deposition.Although a body of evidence shows that keratinocytes explanted onto a wound bed promote closure of a skin injury,the underlying mechanisms are not well understood.The basal layer of epidermis is rich in undifferentiated keratinocytes(UKs).We showed that UKs injected into granulation tissue could switch into-SMA positive cells,and accelerate the rate of skin wound healing.In addition,when the epidermis sheets isolated from foreskin cover up the wound bed or are induced in vitro,keratinocytes located at the basal layers or adjacent sites were observed to convert into myofibroblast-like cells.Thus,UKs have a potential for myofibroblastic transition,which provides a novel mechanism by which keratinocyte explants accelerate skin wound healing.
