Table 1.

Alterations in stem cell characteristics with age [54]

Stem cells	Self-renewal in senescence tissuesa	Proliferative activity	Differentiation capability	Regeneration and repair
HSCs	About × 2–6	diminished	Increased myeloid cell production	Immune suppression, reduced engraftment potential
NSCs	About ÷ 2	diminished	Maintained in vitro	-
MuSCs	About ÷ 2	diminished	Increased fibrosis after injury	Myofibril regeneration and reduced engraftment potential
ISCs	=	diminished	Increased secretory lineage cells	UV exposure reduces generation; response delayed
HFSCs	=	diminished	=	The hair cycle stops, and wounds take longer to heal

^aIncreased ( ×)/ Decreased ( ÷)/Maintained at equivalent levels ( =)