Evolution has left mammals with only a limited ability to regenerate heart tissue. Unlike very regenerative species such as salamanders or zebrafish, we lose most of our ability to heal the heart very early in life. Here, researchers suggest that this is keyed to reduced telomere length in heart cells, but in a way that is very different to the more familiar erosion of average telomere length that occurs over the course of aging. In this case that reduced length is a developmental process occurring in early childhood.
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