I've previously mentioned work showing that providing young blood to an older brain can be beneficial, and now want to note work by Loffredo et al. that shows that exposure to a young circulation reverses age-related cardiac hypertrophy, which is a prominent feature of age-related diatolic heart failure. The TGFβ family member GDF11 appears to be the crucial circulating factor that declines with age; restoring GDF11 to youthful levels reverses age-related cardiac hypertrophy.
Also, relevant to aging, I might note a longitudinal study by Pudas et al. comparing MRI data from elderly people most successful in preserving episodic memory and ability on paired association tasks with measurements on average contemporaries. The results suggest that successful cognitive aging is associated with preservation of the responsiveness of the hippocampus and prefrontal cortex.